Co-reporter:Toshimichi Ohmura, Hiroki Nishiura, and Michinori Suginome
Organometallics November 13, 2017 Volume 36(Issue 21) pp:4298-4298
Publication Date(Web):October 30, 2017
DOI:10.1021/acs.organomet.7b00695
Silylboronic esters bearing a N,N-dialkylaminomethyl group on the silicon atoms were synthesized and used in palladium-catalyzed reactions. Five silylboronic esters were synthesized through a reaction of the [(N,N-dialkylaminomethyl)diorganosilyl]lithiums with i-PrOB(pin). An addition reaction of the silylboronic ester to ethynylbenzene (silaboration) took place efficiently by a phosphine- and isocyanide-free palladium catalyst to give (E)-1-silyl-2-boryl-1-phenylethene in a regio- and stereoselective manner. On the other hand, the silylboronic esters underwent β-elimination reactions in the presence of a palladium catalyst and styrene to afford 1,3-disilacyclobutanes and aminoboranes in good yields. This may be due to the generation of silene intermediates during the reaction. It should be noted that use of styrene as a ligand was essential for the generation of the silene species.
Co-reporter:Takeru Torigoe, Toshimichi Ohmura, and Michinori Suginome
The Journal of Organic Chemistry March 17, 2017 Volume 82(Issue 6) pp:2943-2943
Publication Date(Web):February 10, 2017
DOI:10.1021/acs.joc.6b02917
A conversion of trimethylsilylalkanes into the corresponding alcohols is established based on an iridium-catalyzed, chemoselective C(sp3)–H borylation of the methyl group on silicon. The (borylmethyl)silyl group formed by C(sp3)–H borylation is treated with H2O2/NaOH, and the resulting (hydroxymethyl)silyl group is converted into a hydroxyl group by Brook rearrangement, followed by oxidation of the resulting methoxysilyl group under Tamao conditions. An alternative route proceeding through the formylsilyl group formed from a (hydroxymethyl)silyl group by Swern oxidation is also established. The method is applicable to substituted trimethylsilylcycloalkanes and 1,1-dimethyl-1-silacyclopentane for conversion into the corresponding stereodefined cycloalkyl alcohols and 1,4-butanediol.
Co-reporter:Yukako Yoshinaga, Takeshi Yamamoto, and Michinori Suginome
ACS Macro Letters July 18, 2017 Volume 6(Issue 7) pp:705-705
Publication Date(Web):June 20, 2017
DOI:10.1021/acsmacrolett.7b00352
Helical poly(quinoxaline-2,3-diyl)s copolymers PQXbpy consisting of a coordinating unit, which bears a varied achiral, substituted 2,2′-bipyridyl pendant, and a chiral unit bearing chiral side chains were synthesized and used as a ligand in copper-catalyzed asymmetric cyclopropanation of olefins with diazoacetates, giving up to 91:9 er with high chemical yield. The enantioselection relied on the helical structure of PQXbpy. A single PQXbpy afforded either of a pair of enantiomers with high enantioselectivity by switching its helical sense by changing the reaction solvent from pure toluene to a 3/1 mixture of toluene and 1,1,2-trichloroethane.
Co-reporter:Takeshi Yamamoto, Ryo Murakami, and Michinori Suginome
Journal of the American Chemical Society February 22, 2017 Volume 139(Issue 7) pp:2557-2557
Publication Date(Web):February 5, 2017
DOI:10.1021/jacs.6b12349
Helically chiral poly(quinoxaline-2,3-diyl)s bearing 4-aminopyrid-3-yl pendants were synthesized as new helical-polymer-based chiral nucleophilic organocatalysts. The obtained chiral nucleophilic polymer catalysts exhibited high catalytic activity, enantioselectivity, and reusability in asymmetric Steglich rearrangement of oxazolyl carbonate to C-carboxyazlactone. The polyquinoxaline-based, helically chiral DMAP catalyst mediated intramolecular acyl transfer selectively, by contrast with known small-molecule-based chiral organocatalysts, which also mediate intermolecular acyl transfers.
Co-reporter:Dr. Takeru Torigoe; Dr. Toshimichi Ohmura; Dr. Michinori Suginome
Angewandte Chemie International Edition 2017 Volume 56(Issue 45) pp:14272-14276
Publication Date(Web):2017/11/06
DOI:10.1002/anie.201708578
AbstractHighly enantioselective cycloisomerization of N-methylanilines, bearing o-alkenyl groups, into indolines is established. An iridium catalyst bearing a bidentate chiral diphosphine effectively promotes the intramolecular addition of the C(sp3)−H bond across a carbon–carbon double bond in a highly enantioselective fashion. The reaction gives indolines bearing a quaternary stereogenic carbon center at the 3-position. The reaction mechanism involves rate-determining oxidative addition of the N-methyl C−H bond, followed by intramolecular carboiridation and subsequent reductive elimination.
Co-reporter:Takeshi Yamamoto, Aoi Ishibashi, and Michinori Suginome
Organic Letters 2017 Volume 19(Issue 4) pp:
Publication Date(Web):January 30, 2017
DOI:10.1021/acs.orglett.7b00041
Ir-catalyzed ortho-directed C–H borylation of pyrazolylaniline (PZA)-modified arylboronic acids with bis(pinacolate)diboron afforded o-benzenediboronic acids in which two boronyl groups are differentially modified by pinacol (PIN) and PZA. By using this borylation after nondirected Ir-catalyzed C–H borylation, o-benzenediboronic acids are conveniently synthesized from unfunctionalized arenes. The differentially modified o-benzenediboronic acids undergo selective oxidation and Suzuki–Miyaura cross-coupling at the PZA-modified boronyl groups, affording o-functionalized arylboronic acids selectively.
Co-reporter:Yuuya Nagata, Tsuyoshi Nishikawa, and Michinori Suginome
ACS Macro Letters 2016 Volume 5(Issue 4) pp:519
Publication Date(Web):April 5, 2016
DOI:10.1021/acsmacrolett.6b00191
Random poly(quinoxaline-2,3-diyl) copolymers, containing chiral (S)-3-octyloxymethyl and achiral propoxymethyl side chain units, experience an abnormal sergeants-and-soldiers effect, that is, they adopt, depending on the chiral monomer mole fraction, either P- or M-helical conformations in anisole (PhOCH3) and benzotrifluoride (PhCF3). In benzene (PhH) and toluene (PhCH3), these copolymers exclusively adopt an M-helical conformation, regardless of the chiral monomer mole fraction. For a co-300mer, with a 40% mole fraction of chiral units, the selective induction of an M-helix (>99%) was observed in PhH, while in PhCF3, a P-helical conformation was induced selectively (>99%). This helix inversion of the polymer backbone is thus able to control the chirality of a chiral polymer ligand in aromatic solvents. The incorporation of a small amount of coordinating PPh2 groups into the copolymer resulted in a chiral macromolecular ligand, which allowed the enantioselective synthesis of both enantiomeric products in an asymmetric Suzuki–Miyaura coupling reaction (R-product: 91% ee in PhH; S-product: 95% ee in PhCF3) from a single catalyst.
Co-reporter:Toshimichi Ohmura, Ikuo Sasaki, Takeru Torigoe, and Michinori Suginome
Organometallics 2016 Volume 35(Issue 11) pp:1601-1603
Publication Date(Web):June 3, 2016
DOI:10.1021/acs.organomet.6b00316
An iridium-catalyzed C(sp3)–H borylation of X3SiMe (X = hydrolyzable group) was established. A trialkoxy(methyl)silane bearing sterically demanding neopentyloxy groups (X = neopentyloxy) underwent C–H borylation at the methyl group on silicon, giving (borylmethyl)tris(neopentyloxy)silane in 70% isolated yield. The choice of the hydrolyzable group X was the key to efficient and chemoselective C–H borylation; trialkoxy(methyl)silanes bearing sterically less demanding alkoxy groups (X = ethoxy, n-butyloxy, and isobutyloxy) suffered from C–H activation at the alkoxy groups, and trichloro(methyl)silane (X = Cl) failed to react. A trimethylsiloxy group could substitute the neopentyloxy groups of the borylated product by the reaction of trimethylsilanol in the presence of tetrabutylammonium fluoride.
Co-reporter:Yuuya Nagata; Tsuyoshi Nishikawa
Journal of the American Chemical Society 2015 Volume 137(Issue 12) pp:4070-4073
Publication Date(Web):March 20, 2015
DOI:10.1021/jacs.5b01422
Chiral random poly(quinoxaline-2,3-diyl) polymers of the sergeants-and-soldiers-type (sergeant units bearing (S)-3-octyloxymethyl groups) adopt an M- or P-helical conformation in the presence of achiral units bearing propoxymethyl or butoxy groups (soldier units), respectively. Unusual bidirectional induction of the helical sense can be observed for a copolymer with butoxy soldier units upon changing the mole fraction of the sergeant units. In the presence of 16–20% of sergeant units, the selective induction of a P-helix was observed, while the selective induction of an M-helix was observed for a mole fraction of sergeant units of more than 60%. This phenomenon could be successfully employed to control the helical chirality of copolymers by applying either random or block copolymerization protocols. Random or block copolymerization of sergeant and soldier monomers in a 18:82 ratio resulted in the formation of 250mers with almost absolute P- or M-helical conformation, respectively (>99% ee). Incorporation of a small amount of coordination sites into the random and block copolymers resulted in chiral macromolecular ligands, which allowed the enantioselective synthesis of both enantiomers in the Pd-catalyzed asymmetric hydrosilylation of β-methylstyrene.
Co-reporter:Toshimichi Ohmura; Yohei Morimasa
Journal of the American Chemical Society 2015 Volume 137(Issue 8) pp:2852-2855
Publication Date(Web):February 10, 2015
DOI:10.1021/jacs.5b00546
A 4,4′-bipyridine-based catalyst system for diboration of pyrazine derivatives was established. The catalyst cycle consists of the following two steps: (1) reductive addition of the boron–boron bond of bis(pinacolato)diboron to 4,4′-bipyridine to form N,N′-diboryl-4,4′-bipyridinylidene and (2) oxidative boryl transfer from the intermediate to pyrazine to give N,N′-diboryl-1,4-dihydropyrazine with regeneration of 4,4′-bipyridine.
Co-reporter:Toshimichi Ohmura, Hiroki Taniguchi, and Michinori Suginome
ACS Catalysis 2015 Volume 5(Issue 5) pp:3074
Publication Date(Web):April 14, 2015
DOI:10.1021/acscatal.5b00513
1-Alkyl-2-methylenecyclopropanes react with silylboronic esters under mild conditions in the presence of a phosphine-free platinum catalyst, giving 3-substituted 2-boryl-4-silyl-1-butenes through selective cleavage of the less hindered proximal C–C bond of the cyclopropane ring. The steric bulk of the silyl group of the silylboronic esters was critical for efficient formation of the silaboration products, and i-PrPh2Si–B(pin) was developed as a silylboronic ester of choice.Keywords: C−C bond cleavage; homogeneous catalysis; methylenecyclopropane; organoboron compound; organosilicon compound; platinum catalyst; selectivity; silaboration
Co-reporter:Yuuya Nagata, Ryohei Takeda and Michinori Suginome
Chemical Communications 2015 vol. 51(Issue 56) pp:11182-11185
Publication Date(Web):03 Jun 2015
DOI:10.1039/C5CC04255K
Poly(quinoxaline-2,3-diyl)s with chiral (S)-2-butoxymethyl side chains dissolved in 1,2-dichloroethane experience a reversible pressure-dependent helix inversion from P- to M-helical structures between 0.1 MPa and 200 MPa.
Co-reporter:Yuto Akai, Laure Konnert, Takeshi Yamamoto and Michinori Suginome
Chemical Communications 2015 vol. 51(Issue 33) pp:7211-7214
Publication Date(Web):20 Mar 2015
DOI:10.1039/C5CC01074H
A single-handed helical polymer ligand PQXphos afforded axially chiral biaryl esters with high enantioselectivities in asymmetric Suzuki–Miyaura cross-coupling. The use of naphthyl bromide bearing a 2,4-dimethyl-3-pentyl ester resulted in both high yields and high enantioselectivities. Either enantiomer could be synthesized selectively by using a single PQXphos through a solvent-dependent switch of the helical chirality.
Co-reporter:Dr. Yuan-Zhen Ke;Dr. Yuuya Nagata;Dr. Tetsuya Yamada;Dr. Michinori Suginome
Angewandte Chemie 2015 Volume 127( Issue 32) pp:9465-9469
Publication Date(Web):
DOI:10.1002/ange.201502209
Abstract
A highly efficient majority-rules effect of poly(quinoxaline-2,3-diyl)s (PQXs) bearing 2-butoxymethyl chiral side chains at the 6- and 7-positions was established and attributed to large ΔGh values (0.22–0.41 kJ mol−1), which are defined as the energy difference between P- and M-helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from (R)-2-octanol (23 % ee) and a monomer bearing a PPh2 group adopted a single-handed helical structure (>99 %) and could be used as a highly enantioselective chiral ligand in palladium-catalyzed asymmetric reactions (products formed with up to 94 % ee), in which the enantioselectivity could be switched by solvent-dependent inversion of the helical PQX backbone.
Co-reporter:Dr. Yuan-Zhen Ke;Dr. Yuuya Nagata;Dr. Tetsuya Yamada;Dr. Michinori Suginome
Angewandte Chemie International Edition 2015 Volume 54( Issue 32) pp:9333-9337
Publication Date(Web):
DOI:10.1002/anie.201502209
Abstract
A highly efficient majority-rules effect of poly(quinoxaline-2,3-diyl)s (PQXs) bearing 2-butoxymethyl chiral side chains at the 6- and 7-positions was established and attributed to large ΔGh values (0.22–0.41 kJ mol−1), which are defined as the energy difference between P- and M-helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from (R)-2-octanol (23 % ee) and a monomer bearing a PPh2 group adopted a single-handed helical structure (>99 %) and could be used as a highly enantioselective chiral ligand in palladium-catalyzed asymmetric reactions (products formed with up to 94 % ee), in which the enantioselectivity could be switched by solvent-dependent inversion of the helical PQX backbone.
Co-reporter:Yuuya Nagata ; Tsuyoshi Nishikawa
Journal of the American Chemical Society 2014 Volume 136(Issue 45) pp:15901-15904
Publication Date(Web):October 24, 2014
DOI:10.1021/ja509531t
Poly(quinoxaline-2,3-diyl) containing (S)-3-octyloxymethyl side chains was synthesized to investigate the induction of a single-handed helical sense to the main chain in various alkane solvents. The polymer showed an efficient solvent dependent helix inversion between n-octane (M-helix) and cyclooctane (P-helix). After a screening of alkane solvents, it was found that linear alkanes having large molecular aspect ratios induced M-helical structure, and branched or cyclic alkanes having small molecular aspect ratios induced P-helical structure. A polymer ligand containing (S)-3-octyloxymethyl side chains and diphenylphosphino pendants also exhibited solvent-dependent helical inversion between n-octane and cyclooctane, leading to the highly enantioselective production of the both enantiomeric product in a palladium-catalyzed asymmetric hydrosilylation reaction of styrene (R-product 94% ee in n-octane and S-product 90% ee in cyclooctane).
Co-reporter:Yuuya Nagata ; Keisuke Takagi
Journal of the American Chemical Society 2014 Volume 136(Issue 28) pp:9858-9861
Publication Date(Web):June 18, 2014
DOI:10.1021/ja504808r
Poly(quinoxaline-2,3-diyl)s bearing (S)-2-methylbutyl, n-butyl, and 8-chlorooctyl groups as side chains were synthesized to fabricate dry solid polymer thin films. These films exhibited selective reflection of right-handed circular polarized light (CPL) in the visible region after annealing in CHCl3 vapor at room temperature. The handedness of reflected CPL was inverted to the left after annealing in 1,2-dichloroethane vapor. It was also found that the color of a particular single film along with the handedness of reflected CPL were fully tuned reversibly, upon exposure of the film to the vapor of various mixtures of chloroform and 1,2-dichloroethane in different ratios.
Co-reporter:Yuuya Nagata, Tsuyoshi Nishikawa and Michinori Suginome
Chemical Communications 2014 vol. 50(Issue 69) pp:9951-9953
Publication Date(Web):07 Jul 2014
DOI:10.1039/C4CC03944K
Poly(quinoxaline-2,3-diyl)s containing (S)-2-methylbutoxy side chains were found to exhibit blue circularly polarized luminescence (CPL). The handedness of the CPL could be switched by a solvent-dependent helix inversion of the polymer backbone between chloroform (M-helical structure) and 1,1,1-trichloroethane (P-helical structure).
Co-reporter:Toshimichi Ohmura, Takeru Torigoe and Michinori Suginome
Chemical Communications 2014 vol. 50(Issue 48) pp:6333-6336
Publication Date(Web):06 May 2014
DOI:10.1039/C4CC01262C
The C(sp3)–H bonds located on the methyl groups of an isopropyl group participate in iridium-catalysed C–H borylation with bis(pinacolato)diboron via a significant rate acceleration caused by a catalytic amount of t-BuOK.
Co-reporter:Dr. Takeshi Yamamoto;Yuto Akai;Dr. Michinori Suginome
Angewandte Chemie 2014 Volume 126( Issue 47) pp:12999-13002
Publication Date(Web):
DOI:10.1002/ange.201407358
Abstract
Post-polymerization CH activation of poly(quinoxaline-2,3-diyl)-based helically chiral phosphine ligands (PQXphos) with palladium(II) acetate afforded chiral phosphapalladacycles quantitatively. In situ generated palladacycles exhibited enantioselectivities up to 94 % ee in the palladium-catalyzed asymmetric ring-opening arylation of 1,4-epoxy-1,4-dihydronaphthalenes with arylboronic acids.
Co-reporter:Dr. Takeshi Yamamoto;Yuto Akai;Dr. Michinori Suginome
Angewandte Chemie International Edition 2014 Volume 53( Issue 47) pp:12785-12788
Publication Date(Web):
DOI:10.1002/anie.201407358
Abstract
Post-polymerization CH activation of poly(quinoxaline-2,3-diyl)-based helically chiral phosphine ligands (PQXphos) with palladium(II) acetate afforded chiral phosphapalladacycles quantitatively. In situ generated palladacycles exhibited enantioselectivities up to 94 % ee in the palladium-catalyzed asymmetric ring-opening arylation of 1,4-epoxy-1,4-dihydronaphthalenes with arylboronic acids.
Co-reporter:Yuuya Nagata ; Tetsuya Yamada ; Takumi Adachi ; Yuto Akai ; Takeshi Yamamoto
Journal of the American Chemical Society 2013 Volume 135(Issue 27) pp:10104-10113
Publication Date(Web):June 17, 2013
DOI:10.1021/ja403391m
Poly(quinoxaline-2,3-diyl) copolymers bearing various “sergeant” chiral units with common “soldier” achiral units have been synthesized to investigate the efficiency of screw-sense induction and its dependence on the nature of the solvents. Optically active 2-alkoxymethyl side chains located at the 6- and 7-positions of the quinoxaline ring induced a single-handed helical conformation more efficiently than 3-methylpentyl or 2-methylbutoxy chiral side chains. Among the 2-alkoxymethyl side chains, those bearing higher 2-alkoxy groups induced a single-handed screw sense more efficiently. For instance, a monomer unit bearing (R)-2-octyloxymethyl groups stabilized the P-helix by 1.01 kJ/mol, whereas the monomer bearing (S)-2-butoxymethyl groups stabilized the M-helix by 0.59 kJ/mol. The effect of the position of the sergeant units in the polymer main chain on the screw-sense induction was also investigated using copolymers in which the positions of the sergeant units were carefully controlled by their synthesis via living polymerization. Chiral units placed sparsely could induce single-handed helical structure efficiently. Chiral units bearing 2-alkoxymethyl, 3-methylpentyl, and 2-methylbutoxy groups showed solvent-dependent helix inversion in CHCl3 and 1,1,2-trichloroethane. No helix inversion was observed in those solvents with chiral units bearing 2-butoxy or (2-methylbutoxy)methyl side chains. The 40-mer of the (R)-2-octyloxymethyl units showed P-helical structures in THF, t-BuOMe, and c-C5H11OMe, toluene, pyridine, Et3N, 1-BuOH, CHCl3, CH2Cl2, 1,4-dichlorobutane, 1,1,-dichloroethane, and 1,1,1-trichloroethane, whereas M-helical structures were induced in 1-BuCN, 1-PrCN, 1,2-dichloroethane, 1,3-dichloropropane, and 2-BuOH.
Co-reporter:Toshimichi Ohmura, Akihito Kijima, Yusuke Komori, and Michinori Suginome
Organic Letters 2013 Volume 15(Issue 14) pp:3510-3513
Publication Date(Web):July 5, 2013
DOI:10.1021/ol401051d
Reaction of N-alkylisoindoles with (bromoethynyl)triisopropylsilane afforded 1,3-bis(triisopropylsilylethynyl) isoindoles in high yields. The formal C–H alkynylation proceeds under transition-metal-free conditions through [4 + 2] cycloaddition of the pyrrole ring of isoindole with bromoalkyne followed by ring-opening of the product.
Co-reporter:Takeshi Yamamoto, Takumi Adachi, and Michinori Suginome
ACS Macro Letters 2013 Volume 2(Issue 9) pp:790
Publication Date(Web):August 20, 2013
DOI:10.1021/mz4003326
Poly(quinoxaline-2,3-diyl) bearing menthyloxymethyl side chains derived from (−)-menthol at the 6- and 7-positions of the quinoxaline ring showed a single, right-handed helical structure in chloroform. Upon introduction of the same (−)-menthol-derived side chains into the 5- and 8-positions, a single, left-handed helical structure was formed in chloroform. The former poly(quinoxaline-2,3-diyl)s showed solvent-dependent inversion of the helical sense in 1,1,2-trichloroethane to form a left-handed helical structure with high screw sense purity. Copolymers bearing both menthyloxymethyl and o-(diphenylphosphino)phenyl groups in their side chains served as highly enantioselective chiral ligands in the palladium-catalyzed hydrosilylation of styrene.
Co-reporter:Dr. Masaki Daini;Dr. Akihiko Yamamoto ;Dr. Michinori Suginome
Asian Journal of Organic Chemistry 2013 Volume 2( Issue 11) pp:968-976
Publication Date(Web):
DOI:10.1002/ajoc.201300164
Abstract
Cyclizative alkynylboration and alkenylboration of carbon–carbon triple bonds proceeds in the presence of a nickel catalyst. Chloroboranes bearing homopropargyloxy or bishomopropargyloxy groups were used as substrates with alkynylstannane, vinylstannane, and alkenylzirconium reagents as donors of organic groups. The reaction mechanism may involve the following elementary steps: oxidative addition of the BCl bond to a nickel(0) catalyst, insertion of the triple bond into the NiB bond, Z-to-E isomerization of the alkenylnickel intermediate, transmetalation from organostannane or organozirconium reagents, and reductive elimination of the BC bond. An intermediary nickel complex was isolated and identified by a single-crystal X-ray analysis.
Co-reporter:Toshimichi Ohmura, Takeru Torigoe, and Michinori Suginome
Organometallics 2013 Volume 32(Issue 21) pp:6170-6173
Publication Date(Web):October 9, 2013
DOI:10.1021/om400900z
In the presence of an iridium 3,4,7,8-tetramethyl-1,10-phenanthroline catalyst, a methyl group on the silicon atom of alkyltrimethylsilanes undergoes selective C–H borylation with bis(pinacolato)diboron in cyclooctane at 135 °C to give alkyl(borylmethyl)dimethylsilanes. The C–H borylation of tetramethylsilane takes place efficiently at 100 °C. Permethyloligosilanes can also undergo C–H borylation without cleavage of the Si–Si bonds.
Co-reporter:Toshimichi Ohmura, Kazuyuki Oshima, and Michinori Suginome
Organometallics 2013 Volume 32(Issue 9) pp:2870-2873
Publication Date(Web):April 23, 2013
DOI:10.1021/om400138u
Cyclic alkenylborates have been synthesized regioselectively via a palladium-catalyzed regioselective silaboration of terminal alkynes with ClMe2Si–B(pin) followed by basic hydrolysis. The cyclic borates undergo cross coupling with 4-iodoanisole in the absence of an external base.
Co-reporter:Toshimichi Ohmura ; Takeru Torigoe
Journal of the American Chemical Society 2012 Volume 134(Issue 42) pp:17416-17419
Publication Date(Web):October 8, 2012
DOI:10.1021/ja307956w
A methyl group of methylchlorosilanes undergoes C–H borylation in an iridium-catalyzed reaction with bis(pinacolato)diboron in cyclohexane at 80 °C, giving (borylmethyl)chlorosilanes selectively.
Co-reporter:Yuto Akai ; Takeshi Yamamoto ; Yuuya Nagata ; Toshimichi Ohmura
Journal of the American Chemical Society 2012 Volume 134(Issue 27) pp:11092-11095
Publication Date(Web):June 22, 2012
DOI:10.1021/ja303506k
The poly(quinoxaline-2,3-diyl)-based helically chiral phosphine ligands PQXphos exhibited high enantioselectivities up to 97% ee in palladium-catalyzed desymmetrization of meso-1,2-dialkylsubstituted-3-methylenecyclopropanes through silaborative cleavage of the C–C bond. The observed enantioselectivities were higher than those obtained with 2-diarylphosphino-1,1′-binaphthyl in our original report. Remarkable rate enhancement was also observed with a series of PQXphos in comparison with the corresponding low-molecular weight ligands.
Co-reporter:Kazuyuki Oshima ; Toshimichi Ohmura
Journal of the American Chemical Society 2012 Volume 134(Issue 8) pp:3699-3702
Publication Date(Web):February 9, 2012
DOI:10.1021/ja3002953
Pyridine undergoes addition of pinacolborane at 50 °C in the presence of a rhodium catalyst, giving N-boryl-1,2-dihydropyridine in a high yield. The selective 1,2-hydroboration also takes place in the reactions of substituted pyridines. In the reaction of 3-substituted pyridines, 3-substituted N-boryl-1,2-dihydropyridines are formed regioselectively.
Co-reporter:Yuuya Nagata, Tsuyoshi Nishikawa and Michinori Suginome
Chemical Communications 2012 vol. 48(Issue 91) pp:11193-11195
Publication Date(Web):28 Sep 2012
DOI:10.1039/C2CC36275A
Poly(quinoxaline-2,3-diyl)s bearing pyrene pendants exhibited solvent-dependent changes of the fluorescence color (blue and green) and the screw-sense selectivity (left-handed and racemic) in chloroform and 1,1,1-trichloroethane, respectively.
Co-reporter:Kazuyuki Oshima, Toshimichi Ohmura and Michinori Suginome
Chemical Communications 2012 vol. 48(Issue 68) pp:8571-8573
Publication Date(Web):05 Jul 2012
DOI:10.1039/C2CC34086K
Pyrazines and substituted pyrazines undergo addition of boron reagents having B–B, Si–B, and H–B bonds under transition-metal-free conditions, leading to high-yield synthesis of N-borylated 1,4-dihydropyrazines and 1,2,3,4-tetrahydropyrazine.
Co-reporter:Yuuya Nagata;Satoru Ohashi
Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 8) pp:1564-1571
Publication Date(Web):
DOI:10.1002/pola.25926
Abstract
Poly(quinoxaline-2,3-diyl)s having a terminal formyl or boronyl group were prepared by living polymerization of 1,2-diisocyanobenzenes using organopalladium initiators bearing a protected formyl or boronyl group. Poly(quinoxaline-2,3-diyl)s were successfully deracemized by reacting them with small optically active molecules at their terminal formyl or boronyl group, leading to the induction of optically active helical structures. Poly(quinoxaline-2,3-diyl) having terminal formyl groups was converted to one-handed helical polymer, in which the screw-sense excess was 68% (84:16). The helix sense of the boronyl-terminated poly(quinoxaline-2,3-diyl) was reversibly controlled by attaching and removing the chiral group. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Co-reporter:Tomotsugu Awano ; Toshimichi Ohmura
Journal of the American Chemical Society 2011 Volume 133(Issue 51) pp:20738-20741
Publication Date(Web):November 30, 2011
DOI:10.1021/ja210025q
The stereochemical course of the stereospecific Suzuki–Miyaura coupling of enantioenriched α-(acetylamino)benzylboronic esters with aryl bromides can be switched by the choice of acidic additives in the presence of a Pd/XPhos catalyst system. Highly enantiospecific, invertive C–C bond formation takes place with the use of phenol as an additive. In contrast, high enantiospecificity for retention of configuration is attained in the presence of Zr(Oi-Pr)4·i-PrOH as an additive.
Co-reporter:Kazuyuki Oshima ; Toshimichi Ohmura
Journal of the American Chemical Society 2011 Volume 133(Issue 19) pp:7324-7327
Publication Date(Web):April 21, 2011
DOI:10.1021/ja2020229
The addition of silylboronic esters to pyridine takes place in toluene at 50 °C in the presence of a palladium catalyst to give N-boryl-4-silyl-1,4-dihydropyridines in high yield. The regioselective 1,4-silaboration also proceeds in the reaction of 2-picoline and 3-substituted pyridines, whereas 4-substituted pyridines undergo 1,2-silaboration to give N-boryl-2-silyl-1,2-dihydropyridines regioselectively.
Co-reporter:Masaki Daini
Journal of the American Chemical Society 2011 Volume 133(Issue 13) pp:4758-4761
Publication Date(Web):March 10, 2011
DOI:10.1021/ja200856t
Palladium-catalyzed alkenylboration of carbon−carbon double bonds has been achieved using the reaction of chloro(diisopropylamino)boryl ethers of homoallylic alcohols with alkenylzirconium reagents. The reaction may proceed through an initial oxidative addition of the B−Cl bond, intramolecular insertion of the C═C bond into the B−Pd bond, transmetalation from the alkenylzirconium reagent, and reductive elimination of the products. The cyclization proceeds with high diastereoselectivity for the formation of cis-3,5- or trans-3,4-disubstituted-1,2-oxaborolane products. Cross-coupling of the resultant products with aryl iodides proceeds with retention of configuration at the boron-bound secondary carbon atom.
Co-reporter:Kohei Masuda, Toshimichi Ohmura, and Michinori Suginome
Organometallics 2011 Volume 30(Issue 6) pp:1322-1325
Publication Date(Web):February 21, 2011
DOI:10.1021/om200135u
The palladium-catalyzed silylene transfer to 2-alkenylindoles from a silylboronic ester bearing a diethylamino group on the silicon atom takes place efficiently, resulting in the formation of a 1-sila-3-cyclopentene ring fused with the indole ring. Further silylene transfer proceeds in the reaction of 2-(1-alkenyl)indoles, giving bissilylated tricyclic indoles in high yields.
Co-reporter:Dr. Takeshi Yamamoto;Yuto Akai;Dr. Yuuya Nagata;Dr. Michinori Suginome
Angewandte Chemie International Edition 2011 Volume 50( Issue 38) pp:8844-8847
Publication Date(Web):
DOI:10.1002/anie.201103792
Co-reporter:Dr. Toshimichi Ohmura;Kazuyuki Oshima ;Dr. Michinori Suginome
Angewandte Chemie International Edition 2011 Volume 50( Issue 52) pp:12501-12504
Publication Date(Web):
DOI:10.1002/anie.201106077
Co-reporter:Yuuya Nagata
Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 19) pp:4275-4282
Publication Date(Web):
DOI:10.1002/pola.24871
Abstract
Poly(quinoxaline-2,3-diyl)s bearing alkoxy pendants was synthesized by living polymerization of 4,5-dialkoxy-3,6-dimethyl-1,2-diisocyanobenzenes, which were easily accessible from 3,6-dimethylcatechol, using organonickel complexes as initiators. Thermal properties of the obtained polymers were fully determined by thermogravimetric analysis and differential scanning calorimetry, exhibiting strong dependence on their side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Co-reporter:Dr. Takeshi Yamamoto;Yuto Akai;Dr. Yuuya Nagata;Dr. Michinori Suginome
Angewandte Chemie 2011 Volume 123( Issue 38) pp:9006-9009
Publication Date(Web):
DOI:10.1002/ange.201103792
Co-reporter:Toshimichi Ohmura, Kazuyuki Oshima, Hiroki Taniguchi and Michinori Suginome
Journal of the American Chemical Society 2010 Volume 132(Issue 35) pp:12194-12196
Publication Date(Web):August 11, 2010
DOI:10.1021/ja105096r
The regioselectivity in the addition of silylboronic esters to terminal alkynes can be switched by the choice of phosphorus ligands on the palladium catalysts. The silaboration proceeds with normal regisoselectivity in the presence of (η3-C3H5)Pd(PPh3)Cl (1.0 mol %) to give 1-boryl-2-silyl-1-alkenes in high yields. In sharp contrast, selective formation of the inverse regioisomers, 2-boryl-1-silyl-1-alkenes, takes place when the reaction is carried out with a palladium catalyst bearing P(t-Bu)2(biphenyl-2-yl). A reaction mechanism for the change of regioselectivity that involves reversible insertion/β-boryl elimination steps is proposed.
Co-reporter:Takeshi Yamamoto ; Tetsuya Yamada ; Yuuya Nagata
Journal of the American Chemical Society 2010 Volume 132(Issue 23) pp:7899-7901
Publication Date(Web):May 20, 2010
DOI:10.1021/ja102428q
A polyquinoxaline-based helical polymer ligand bearing both helical-sense-determining chiral side chains and coordinating diarylphosphino side chains exhibits solvent-dependent formation of P- or M-helical structures, with which either the S- or R-hydrosilylation product was obtained with high (>93% enantiomeric excess) enantioselectivities.
Co-reporter:Noriyuki Iwadate
Journal of the American Chemical Society 2010 Volume 132(Issue 8) pp:2548-2549
Publication Date(Web):February 8, 2010
DOI:10.1021/ja1000642
A differentially protected diboron bearing the naphthalene-1,8-diaminato group on one of the two boron atoms undergoes highly regioselective diboration with terminal alkynes in the presence of Pt or Ir catalysts, giving 1-alkene-1,2-diboronic acid derivatives in which the less reactive B(dan) group is located at the terminal position. The products undergo selective Suzuki−Miyaura coupling with aryl bromides at the internal boronyl group, leading to the formation of 2,2-disubstituted alkenylboronic acid derivatives.
Co-reporter:Tetsuya Yamada, Yuuya Nagata and Michinori Suginome
Chemical Communications 2010 vol. 46(Issue 27) pp:4914-4916
Publication Date(Web):01 Jun 2010
DOI:10.1039/C001564D
Poly(quinoxaline-2,3-diyl)s bearing chiral (R)-2-butoxy side chains adopt pure right- or left-handed screw senses in CHCl3 and 1,1,2-trichloroethane, respectively.
Co-reporter:Masamichi Shirakura Dr. Dr.
Angewandte Chemie 2010 Volume 122( Issue 22) pp:3915-3917
Publication Date(Web):
DOI:10.1002/ange.201001188
Co-reporter:Michinori Suginome
The Chemical Record 2010 Volume 10( Issue 5) pp:348-358
Publication Date(Web):
DOI:10.1002/tcr.201000029
Abstract
Transition-metal-catalyzed carboborations, in which organic and boryl groups are introduced concomitantly to unsaturated organic molecules, have been developed. Direct carboborations, which proceed via activation of B–C bonds of cyanoboranes and alkynylboranes, and transmetalative carboborations, in which activation of B–Cl bonds is followed by transmetalation from organotin and organozirconium reagents, are overviewed. In addition, as representative results and mechanistic considerations, the scientific background and a personal view behind the study are also described. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Published online in Wiley InterScience (www.interscience.wiley.com)
Co-reporter:Tetsuya Yamada;Hiroyoshi Noguchi;Yuuya Nagata
Journal of Polymer Science Part A: Polymer Chemistry 2010 Volume 48( Issue 4) pp:898-904
Publication Date(Web):
DOI:10.1002/pola.23842
Abstract
Optically active chiral organonickel complexes served as efficient chiral initiators for living aromatizing polymerization of 1,2-diisocyanobenzene derivatives, which afford optically active helical poly(quinoxaline-2,3-diyl)s up to 84% s.e. (screw-sense excess). In comparison with asymmetric polymerization with the corresponding organopalladium initiators, the nickel initiators show a much greater polymerization rate, while the selectivity remains high. The organonickel initiators can be generated in situ from nickel(0) precursors with the corresponding enantiopure (S,S)-2-(4,5-diphenylimidazolin-2-yl)phenyl chloride, leading to the convenient synthesis of highly stereo-controlled poly(quinoxaline-2,3-diyl)s. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 898–904, 2010
Co-reporter:Masamichi Shirakura Dr. Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 22) pp:3827-3829
Publication Date(Web):
DOI:10.1002/anie.201001188
Co-reporter:Tetsuya Yamada and Michinori Suginome
Macromolecules 2010 Volume 43(Issue 9) pp:3999-4002
Publication Date(Web):April 13, 2010
DOI:10.1021/ma100500r
Co-reporter:Toshimichi Ohmura ; Kohei Masuda ; Ichiro Takase
Journal of the American Chemical Society 2009 Volume 131(Issue 46) pp:16624-16625
Publication Date(Web):November 2, 2009
DOI:10.1021/ja907170p
Silylboronic esters bearing a dialkylamino group on the silicon atoms reacted with 1,3-dienes in the presence of a palladium catalyst to give silacyclopent-3-enes (i.e., 2,5-dihydrosiloles) in high yields via efficient silylene transfer from the silylboronic ester to the 1,3-dienes. The [4 + 1] cycloaddition was applicable to the parent 1,3-butadiene and various mono-, di-, and trisubstituted 1,3-dienes having silyloxy, cyano, and ester groups. Stereospecific ring formation took place in the reaction with either stereoisomer of 5,7-dodecadiene: the (E,E)-diene gave the cis product, whereas selective formation of the trans product was observed in the reaction of the isomeric (E,Z)-diene. The [4 + 1] cycloaddition followed by dehydrogenation with DDQ or chloranil afforded 2,4- and 2,5-diarylsiloles.
Co-reporter:Hiroki Taniguchi ; Toshimichi Ohmura
Journal of the American Chemical Society 2009 Volume 131(Issue 32) pp:11298-11299
Publication Date(Web):July 28, 2009
DOI:10.1021/ja9046894
A nickel-catalyzed intermolecular hydroacylation of methylenecyclopropanes (MCPs) has been developed. The reaction proceeds with stereospecific cleavage of the proximal C−C bond of the cyclopropane ring to give γ,δ-unsaturated ketones with high diastereoselectivities. A nickel catalyst generated in situ from Ni(cod)2 and P(n-Bu)3 with a P/Ni ratio of 1:1 is effective for the hydroacylation, in which benzaldehyde derivatives, heteroaryl aldehydes, and aliphatic aldehydes react with MCPs at 60−100 °C to afford the corresponding ketones in high yields.
Co-reporter:Hideki Ihara
Journal of the American Chemical Society 2009 Volume 131(Issue 22) pp:7502-7503
Publication Date(Web):May 12, 2009
DOI:10.1021/ja902314v
o-C−H silylation of arylboronic acids has been achieved using 2-pyrazol-5-ylaniline as an ortho-directing agent, which was temporarily attached to the boronyl group via Ru-catalyzed silylation with hydrosilanes. Condensation products of arylboronic acids with 2-pyrazol-5-ylaniline were prepared in situ and subjected to reaction with triorganosilanes in the presence of RuH2(CO)(PPh3)3 at 135 °C. Regioselective silylation at their ortho-positions proceeded in good yields for phenylboronic acids bearing para-substituents such as chloro, fluoro, methyl, methoxy, and trifluoromethyl groups. p-Methoxycarbonyl-substituted phenylboronic acid provided the corresponding silylated product in moderate yield. m-Tolyl- and 2-naphthylboronic acids underwent silylation selectively at the less sterically hindered ortho-positions. The silylated products were utilized in Suzuki−Miyaura coupling, followed either by iodination with ICl or by Tamao oxidation to furnish iodine- or hydroxy-substituted biaryls.
Co-reporter:Toshimichi Ohmura ; Akihito Kijima
Journal of the American Chemical Society 2009 Volume 131(Issue 17) pp:6070-6071
Publication Date(Web):April 8, 2009
DOI:10.1021/ja901095h
1-Boryl- and 1,3-diborylisoindoles were synthesized by the palladium-catalyzed reaction of isoindolines with pinacolborane via sequential dehydrogenation and C−H borylation. Selective formation of the borylated isoindoles was achieved using Pd(dba)2/Me2S as the catalyst, in which Me2S suppressed the formation of 1-boryl-4,5,6,7-tetrahydroisoindoles. Diborylisoindole was cross-coupled with iodobenzene, giving 1,3-diphenylisoindole in high yield.
Co-reporter:Toshimichi Ohmura, Hiroki Taniguchi and Michinori Suginome
Organic Letters 2009 Volume 11(Issue 13) pp:2880-2883
Publication Date(Web):June 10, 2009
DOI:10.1021/ol900829c
Kinetic resolution of racemic 1-alkyl-2-methylenecyclopropanes via silaborative C−C cleavage was efficiently catalyzed by a palladium complex bearing a chiral phosphoramidite, affording 2-boryl-3-silylmethyl-1-alkenes as major products with up to 92% ee. Enantioenrichment through parallel kinetic resolution, where the slower reacting enantiomer was converted to the constitutional isomer of the major product, may be involved as the crucial stereodiscriminating step.
Co-reporter:Noriyuki Iwadate and Michinori Suginome
Organic Letters 2009 Volume 11(Issue 9) pp:1899-1902
Publication Date(Web):March 30, 2009
DOI:10.1021/ol9003096
Hydroboration of aromatic and aliphatic alkynes with 1,8-naphthalenediaminatoborane ((dan)BH) proceeded in the presence of [IrCl(cod)]2 complex with a DPPM or DPEphos ligand, affording alkenylboronic acids whose boronyl groups are masked by the diaminonaphthalene group. The masked alkenylboronic acids thus obtained from alkynes bearing halo-substituted aryl groups served as new coupling modules in an iterative Suzuki−Miyaura cross-coupling reaction for the synthesis of oligo(phenylenevinylene)s.
Co-reporter:Yusuke Tanaka;Kousuke Hidaka;Tomoaki Hasui
European Journal of Organic Chemistry 2009 Volume 2009( Issue 8) pp:1148-1151
Publication Date(Web):
DOI:10.1002/ejoc.200801190
Abstract
Mannich-type reactions of aldehydes with secondary amines and a ketene silyl acetal were promoted by trimethoxyborane in DMSO to afford the corresponding β-amino esters in good yields. B(OMe)3 also promoted Ugi-type reactions ofaldehydes with secondary amines and isocyanides in 1,2-dichloroethane, which leads to the formation of α-amino amides. In these reactions, trimethoxyborane serves as an inexpensive, commercially available, and virtually nonacidic iminium ion generator.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Co-reporter:Takeshi Yamamoto Dr.
Angewandte Chemie 2009 Volume 121( Issue 3) pp:547-550
Publication Date(Web):
DOI:10.1002/ange.200803719
Co-reporter:Toshimichi Ohmura Dr.;Yuta Takasaki;Hideki Furukawa Dr.
Angewandte Chemie 2009 Volume 121( Issue 13) pp:2408-2411
Publication Date(Web):
DOI:10.1002/ange.200805406
Co-reporter:Noriyuki Iwadate, Michinori Suginome
Journal of Organometallic Chemistry 2009 694(11) pp: 1713-1717
Publication Date(Web):
DOI:10.1016/j.jorganchem.2008.11.068
Co-reporter:Akihiko Yamamoto, Yuto Ikeda, Michinori Suginome
Tetrahedron Letters 2009 50(26) pp: 3168-3170
Publication Date(Web):
DOI:10.1016/j.tetlet.2009.01.025
Co-reporter:Takeshi Yamamoto Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 3) pp:539-542
Publication Date(Web):
DOI:10.1002/anie.200803719
Co-reporter:Toshimichi Ohmura Dr.;Yuta Takasaki;Hideki Furukawa Dr.
Angewandte Chemie International Edition 2009 Volume 48( Issue 13) pp:2372-2375
Publication Date(Web):
DOI:10.1002/anie.200805406
Co-reporter:Masaki Daini and Michinori Suginome
Chemical Communications 2008 (Issue 41) pp:5224-5226
Publication Date(Web):12 Sep 2008
DOI:10.1039/B809433K
Three-component coupling of bis(dialkylamino)chloroborane, alkynes and organozirconium reagents proceeded in the presence of palladium catalysts, leading to the formation of stereo-defined alkenylborane derivatives via cis-carboboration of carbon–carbon triple bonds.
Co-reporter:Toshimichi Ohmura, Kazuyuki Oshima and Michinori Suginome
Chemical Communications 2008 (Issue 12) pp:1416-1418
Publication Date(Web):18 Feb 2008
DOI:10.1039/B800181B
Palladium-catalysed cis- and trans-silaboration of terminal alkynes has been developed via the addition of (chlorodimethylsilyl)pinacolborane, followed by a one-pot conversion of the chloro group on the silicon atom to an isopropoxy group.
Co-reporter:Yoko Abe, Kei Kuramoto, Masahiro Ehara, Hiroshi Nakatsuji, Michinori Suginome, Masahiro Murakami and Yoshihiko Ito
Organometallics 2008 Volume 27(Issue 8) pp:1736-1742
Publication Date(Web):March 18, 2008
DOI:10.1021/om070110f
A mechanism for the regioselective silaboration of terminal allene by a palladium catalyst has been studied theoretically. The overall reaction scheme has been examined in particular to determine the mechanism of the regioselectivity. The present catalytic reaction is exothermic and the rate-determining step is the insertion of allene into the Pd−B bond of the Pd complex. σ-Allylic and π-allylic complexes exist as intermediates and play an important role in the regioselectivity. Selective insertion of the unsubstituted C═C bond into the Pd−B bond produces the most stable σ-allylic complex, which converts to the π-allylic complex while maintaining the Pd−O coordination. The selective formation of the specific σ-allylic complex and the large activation barrier between two isomeric π-allylic complexes dominantly determines the regioselectivity of the present reaction. The major-product complex is less stable than the minor-product complex, and therefore kinetic control is predominant in the present reaction.
Co-reporter:Michinori Suginome, Akihiko Yamamoto, Masahiro Murakami
Journal of Organometallic Chemistry 2005 Volume 690(Issue 23) pp:5300-5308
Publication Date(Web):15 November 2005
DOI:10.1016/j.jorganchem.2005.05.005
Cyano(dialkylamino)boryl ethers of homopropargylic alcohols undergo intramolecular addition of a B–CN bond across their carbon–carbon triple bonds (cyanoboration) in the presence of palladium and nickel catalysts, furnishing five-membered cyclic boryl ethers regioselectively in good yields via 5-exo cyclization. The products were transformed into highly substituted α,β-unsaturated nitriles via Suzuki–Miyaura coupling to aryl iodides, rhodium-catalyzed conjugative addition to methyl vinyl ketone, and rhodium-catalyzed protodeborylation.Cyano(dialkylamino)boryl ethers of homopropargylic alcohols undergo intramolecular addition of a B–CN bond across their carbon–carbon triple bonds (cyanoboration) in the presence of palladium and nickel catalysts, furnishing five-membered cyclic boryl ethers regioselectively in good yields via 5-exo cyclization.
Co-reporter:Michinori Suginome Dr.;Taisuke Iwanami Dr.;Yutaka Ohmori;Akira Matsumoto Dr.;Yoshihiko Ito Dr.
Chemistry - A European Journal 2005 Volume 11(Issue 10) pp:
Publication Date(Web):3 MAR 2005
DOI:10.1002/chem.200401031
Highly enantioenriched (E)-allylsilanes have been synthesized from optically active allylic alcohols on the basis of Pd-catalyzed intramolecular bis-silylation followed by highly stereospecific SiO elimination reactions. The method involves three steps: 1) O-disilanylation of the allylic alcohols with chlorodisilanes, 2) intramolecular bis-silylation in the presence of a 1,1,3,3-tetramethylbutyl isocyanide/[Pd(acac)2] (acac=acetylacetonate) catalyst at 110 °C, and 3) treatment of the reaction mixture with organolithium reagents. The overall transformation proceeds with nearly complete conservation of the enantiopurity of the starting allyl alcohols by transposition of the CC bond. For instance, (R)-(E)-3-decen-2-ol (99.6–99.7 % ee) produced (S)-(E)-4-(organosilyl)-2-decene of 98.8–99.4 % ee for a variety of silyl groups, including Me3Si, Me2PhSi, tBuMe2Si, Et3Si, and iPr3Si. In the bis-silylation step, the initially formed trans-1,2-oxasiletanes immediately dimerize to stereoselectively give 1,5-dioxa-2,6-disilacyclooctanes, which are isolated in high yield by carrying out the reaction at 70 °C. The eight-membered ring compounds undergo thermal extrusion of (E)-allylsilanes in high yield at 110 °C, along with formation of 1,3-dioxa-2,5-disilacyclohexane derivatives. These in turn undergo a Peterson-type elimination by treatment with nucleophiles such as BuLi and PhLi to give the (E)-allylsilanes. All of the steps involved in the sequence proceed with extremely high stereoselectivity and stereospecificity, leading to almost complete 1,3-chirality transfer through the overall transformation. The dimerization step, which forms diastereomeric intermediates, allows the synthesis of a highly enantioenriched allylsilane (99.4 % ee) from an optically active allylic alcohol with lower enantiopurity (79.2 % ee) by enrichment of enantiopurity. A general method for the determination of the enantiomeric excesses of (E)-allylsilanes is also described in detail.
Co-reporter:Michinori Suginome Dr.;Akihiko Yamamoto;Masahiro Murakami Dr.
Angewandte Chemie 2005 Volume 117(Issue 16) pp:
Publication Date(Web):10 MAR 2005
DOI:10.1002/ange.200462961
Sehr nützliche Intermediate entstehen bei der cis verlaufenden Pd-katalysierten Cyanoborierung von Alkinen. Ausgehend von 1-Arylalkinen werden die entsprechenden α,β-ungesättigten β-Borylnitrile mit der Cyanogruppe in α-Position zur Arylgruppe regioselektiv und in guten Ausbeuten erhalten. Durch Suzuki-Miyaura-Kupplung werden sie in hoch substituierte α,β-ungesättigte Nitrile überführt (siehe Schema).
Co-reporter:Michinori Suginome Dr.;Akihiko Yamamoto;Masahiro Murakami Dr.
Angewandte Chemie International Edition 2005 Volume 44(Issue 16) pp:
Publication Date(Web):10 MAR 2005
DOI:10.1002/anie.200462961
Highly versatile intermediates are formed through the Pd-catalyzed cyanoboration of alkynes, which proceeds in a cis fashion. When 1-aryl alkynes are used, the corresponding α,β-unsaturated β-boryl nitriles are obtained regioselectively in good yields with the cyano group α to the aryl group. Suzuki–Miyaura coupling of the products leads to highly substituted α,β-unsaturated nitriles (see scheme).
Co-reporter:Michinori Suginome, Yoshihiko Ito
Journal of Organometallic Chemistry 2003 Volume 685(1–2) pp:218-229
Publication Date(Web):15 November 2003
DOI:10.1016/S0022-328X(03)00163-3
Stereoselective synthesis of allyl-, allenyl-, and propargyl-silanes via palladium-catalyzed intramolecular bis-silylation (IBS) is described. IBS of disilanyl ethers of propargylic and allylic alcohols produced bis-silylation products stereoselectively in good yields via formation of 1,2-oxasiletanes as primary products. From the bis-silylation products, allyl-, allenyl-, and propargyl-silanes were synthesized via Peterson-type elimination or acid-catalyzed 1,2-silyl migration. The IBS/elimination as well as the IBS/migration sequences were carried out in one reaction vessel, providing ready access to those synthetically useful organosilicon compounds. Highly enantioenriched allyl-, allenyl-, and propargyl-silanes including polymer-supported derivatives were stereoselectively synthesized by the new methods. Synthetic application of the highly enantioenriched allenyl- and allyl-silanes is also described.Palladium-catalyzed intramolecular bis-silylation of optically active allylic and propargylic alcohols followed by Peterson-type elimination or acid-catalyzed 1,2-silyl migration has been established as stereoselective accesses to highly enantioenriched allyl-, allenyl-, and propargyl-silanes.
Co-reporter:Michinori Suginome, Akihiko Yamamoto and Yoshihiko Ito
Chemical Communications 2002 (Issue 13) pp:1392-1393
Publication Date(Web):30 May 2002
DOI:10.1039/B203645B
α-Dialkylamino nitriles are formed in excellent yields in the reactions of bis(dialkylamino)cyanoboranes with a wide array of carbonyl compounds.
Co-reporter:Michinori Suginome, Yutaka Ohmori and Yoshihiko Ito
Chemical Communications 2001 (Issue 12) pp:1090-1091
Publication Date(Web):25 May 2001
DOI:10.1039/B102613P
Reactions of α-phenethyl-β-borylallylsilane with
aldehydes afforded tricyclic trans-1,2-benzooxadecaline frameworks
stereoselectively in the presence of Lewis acids via sequential
incorporation of two different aldehydes followed by cationic cascade
cyclization, ending up with intramolecular Friedel–Crafts
reaction.
Co-reporter:Toshimichi Ohmura ; Tomotsugu Awano
Journal of the American Chemical Society () pp:
Publication Date(Web):September 7, 2010
DOI:10.1021/ja106632j
The first invertive B-alkyl Suzuki−Miyaura coupling has been achieved. The coupling of enantioenriched α-(acylamino)benzylboronic esters with aryl bromides and chlorides took place efficiently in toluene at 80 °C in the presence of Pd(dba)2 (5 mol %), XPhos (10 mol %), K2CO3 (3 equiv), and H2O (2 equiv). The reaction proceeded with inversion of configuration to give diarylmethanamine derivatives in high yields with high conservation of enantiomeric excesses.
Co-reporter:Masaki Daini and Michinori Suginome
Chemical Communications 2008(Issue 41) pp:NaN5226-5226
Publication Date(Web):2008/09/12
DOI:10.1039/B809433K
Three-component coupling of bis(dialkylamino)chloroborane, alkynes and organozirconium reagents proceeded in the presence of palladium catalysts, leading to the formation of stereo-defined alkenylborane derivatives via cis-carboboration of carbon–carbon triple bonds.
Co-reporter:Tetsuya Yamada, Yuuya Nagata and Michinori Suginome
Chemical Communications 2010 - vol. 46(Issue 27) pp:NaN4916-4916
Publication Date(Web):2010/06/01
DOI:10.1039/C001564D
Poly(quinoxaline-2,3-diyl)s bearing chiral (R)-2-butoxy side chains adopt pure right- or left-handed screw senses in CHCl3 and 1,1,2-trichloroethane, respectively.
Co-reporter:Kazuyuki Oshima, Toshimichi Ohmura and Michinori Suginome
Chemical Communications 2012 - vol. 48(Issue 68) pp:NaN8573-8573
Publication Date(Web):2012/07/05
DOI:10.1039/C2CC34086K
Pyrazines and substituted pyrazines undergo addition of boron reagents having B–B, Si–B, and H–B bonds under transition-metal-free conditions, leading to high-yield synthesis of N-borylated 1,4-dihydropyrazines and 1,2,3,4-tetrahydropyrazine.
Co-reporter:Toshimichi Ohmura, Kazuyuki Oshima and Michinori Suginome
Chemical Communications 2008(Issue 12) pp:NaN1418-1418
Publication Date(Web):2008/02/18
DOI:10.1039/B800181B
Palladium-catalysed cis- and trans-silaboration of terminal alkynes has been developed via the addition of (chlorodimethylsilyl)pinacolborane, followed by a one-pot conversion of the chloro group on the silicon atom to an isopropoxy group.
Co-reporter:Yuuya Nagata, Ryohei Takeda and Michinori Suginome
Chemical Communications 2015 - vol. 51(Issue 56) pp:NaN11185-11185
Publication Date(Web):2015/06/03
DOI:10.1039/C5CC04255K
Poly(quinoxaline-2,3-diyl)s with chiral (S)-2-butoxymethyl side chains dissolved in 1,2-dichloroethane experience a reversible pressure-dependent helix inversion from P- to M-helical structures between 0.1 MPa and 200 MPa.
Co-reporter:Yuuya Nagata, Tsuyoshi Nishikawa and Michinori Suginome
Chemical Communications 2012 - vol. 48(Issue 91) pp:NaN11195-11195
Publication Date(Web):2012/09/28
DOI:10.1039/C2CC36275A
Poly(quinoxaline-2,3-diyl)s bearing pyrene pendants exhibited solvent-dependent changes of the fluorescence color (blue and green) and the screw-sense selectivity (left-handed and racemic) in chloroform and 1,1,1-trichloroethane, respectively.
Co-reporter:Toshimichi Ohmura, Takeru Torigoe and Michinori Suginome
Chemical Communications 2014 - vol. 50(Issue 48) pp:NaN6336-6336
Publication Date(Web):2014/05/06
DOI:10.1039/C4CC01262C
The C(sp3)–H bonds located on the methyl groups of an isopropyl group participate in iridium-catalysed C–H borylation with bis(pinacolato)diboron via a significant rate acceleration caused by a catalytic amount of t-BuOK.
Co-reporter:Yuuya Nagata, Tsuyoshi Nishikawa and Michinori Suginome
Chemical Communications 2014 - vol. 50(Issue 69) pp:NaN9953-9953
Publication Date(Web):2014/07/07
DOI:10.1039/C4CC03944K
Poly(quinoxaline-2,3-diyl)s containing (S)-2-methylbutoxy side chains were found to exhibit blue circularly polarized luminescence (CPL). The handedness of the CPL could be switched by a solvent-dependent helix inversion of the polymer backbone between chloroform (M-helical structure) and 1,1,1-trichloroethane (P-helical structure).
Co-reporter:Yuto Akai, Laure Konnert, Takeshi Yamamoto and Michinori Suginome
Chemical Communications 2015 - vol. 51(Issue 33) pp:NaN7214-7214
Publication Date(Web):2015/03/20
DOI:10.1039/C5CC01074H
A single-handed helical polymer ligand PQXphos afforded axially chiral biaryl esters with high enantioselectivities in asymmetric Suzuki–Miyaura cross-coupling. The use of naphthyl bromide bearing a 2,4-dimethyl-3-pentyl ester resulted in both high yields and high enantioselectivities. Either enantiomer could be synthesized selectively by using a single PQXphos through a solvent-dependent switch of the helical chirality.
![2,1,3-Benzothiadiazole, 4-[2-[bis[4-(trifluoromethyl)phenyl]phosphinothioyl]phenyl]-7-methyl-](/data/chemimg/3737500/1689557-66-1.png)
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![2,1,3-Benzothiadiazole, 4-[2-[bis(4-methoxyphenyl)phosphinothioyl]phenyl]-7-methyl-](/data/chemimg/3737500/1689557-56-9_b.png)
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![2,1,3-Benzothiadiazole, 4-[2-[bis(4-methylphenyl)phosphinothioyl]phenyl]-7-methyl-](/data/chemimg/3737500/1689557-46-7_b.png)
![Quinoxaline, 5-[2-(diphenylphosphino)phenyl]-8-methyl-2,3-diphenyl-](/data/chemimg/3737500/1689556-44-2.png)
![Quinoxaline, 5-[2-(diphenylphosphino)phenyl]-8-methyl-2,3-diphenyl-](/data/chemimg/3737500/1689556-44-2_b.png)
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![Quinoxaline, 5-[2-(diphenylphosphinyl)phenyl]-8-methyl-2,3-diphenyl-](/data/chemimg/3737500/1689556-28-2_b.png)
![Benzoic acid, 4-[(1S,2R)-1,2-dihydro-1-hydroxy-2-naphthalenyl]-, ethyl ester](/data/chemimg/3737400/1689553-28-3.png)
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![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[(1S)-1-methylpropoxy]-](/data/chemimg/3737400/1446202-03-4.png)
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![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[[(2S)-2-methylbutoxy]methyl]-](/data/chemimg/3737400/1446202-01-2.png)
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![Benzene, 1-bromo-2-[2-(2-methoxyphenyl)ethynyl]-](/data/chemimg/3742800/1137270-38-2.png)
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![[1,1'-Biphenyl]-2,3-diamine, 2'-(diphenylphosphinyl)-4-methyl-](/data/chemimg/3720700/1134641-49-8.png)
![[1,1'-Biphenyl]-2,3-diamine, 2'-(diphenylphosphinyl)-4-methyl-](/data/chemimg/3720700/1134641-49-8_b.png)
![Benzene, 1-methoxy-2-[[4-(trifluoromethyl)phenyl]ethynyl]-](http://img.cochemist.com/ccimg/886600/886577-19-1.png)
![Benzene, 1-methoxy-2-[[4-(trifluoromethyl)phenyl]ethynyl]-](http://img.cochemist.com/ccimg/886600/886577-19-1_b.png)
![ETHANONE, 1-[4-[(2-METHOXYPHENYL)ETHYNYL]PHENYL]-](http://img.cochemist.com/ccimg/862700/862604-31-7.png)
![ETHANONE, 1-[4-[(2-METHOXYPHENYL)ETHYNYL]PHENYL]-](http://img.cochemist.com/ccimg/862700/862604-31-7_b.png)
![Benzoic acid, 4-[(2-methoxyphenyl)ethynyl]-, methyl ester](http://img.cochemist.com/ccimg/229200/229174-44-1.png)
![Benzoic acid, 4-[(2-methoxyphenyl)ethynyl]-, methyl ester](http://img.cochemist.com/ccimg/229200/229174-44-1_b.png)
![1H-Isoindole-1,3(2H)-dione, 2-[2-(methylenecyclopropyl)ethyl]-](http://img.cochemist.com/ccimg/199200/199176-89-1.png)
![1H-Isoindole-1,3(2H)-dione, 2-[2-(methylenecyclopropyl)ethyl]-](http://img.cochemist.com/ccimg/199200/199176-89-1_b.png)
![Phosphine, (1R)-[1,1'-binaphthalen]-2-yldiphenyl-](/data/chemimg/1754900/176850-06-9.png)
![Phosphine, (1R)-[1,1'-binaphthalen]-2-yldiphenyl-](/data/chemimg/1754900/176850-06-9_b.png)
![1-Oxa-5-silaspiro[4.5]decane, 4-phenyl-, (R)-](http://img.cochemist.com/ccimg/139100/139017-16-6.png)
![1-Oxa-5-silaspiro[4.5]decane, 4-phenyl-, (R)-](http://img.cochemist.com/ccimg/139100/139017-16-6_b.png)
![Silacyclohexane, 1-[(3-phenyl-2-propenyl)oxy]-, (E)-](http://img.cochemist.com/ccimg/139100/139016-94-7.png)
![Silacyclohexane, 1-[(3-phenyl-2-propenyl)oxy]-, (E)-](http://img.cochemist.com/ccimg/139100/139016-94-7_b.png)
![Benzene, 1-methoxy-2-[(4-methylphenyl)ethynyl]-](http://img.cochemist.com/ccimg/122200/122134-95-6.png)
![Benzene, 1-methoxy-2-[(4-methylphenyl)ethynyl]-](http://img.cochemist.com/ccimg/122200/122134-95-6_b.png)
![BENZENE, 1-METHOXY-2-[(2-METHYLPHENYL)ETHYNYL]-](http://img.cochemist.com/ccimg/64900/64897-49-0.png)
![BENZENE, 1-METHOXY-2-[(2-METHYLPHENYL)ETHYNYL]-](http://img.cochemist.com/ccimg/64900/64897-49-0_b.png)
![[Ir(η2-ethylene)2Cl]2](http://img.cochemist.com/ccimg/39800/39722-81-1.png)
![[Ir(η2-ethylene)2Cl]2](http://img.cochemist.com/ccimg/39800/39722-81-1_b.png)
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![Silane, trichloro[(1R)-1-phenylethyl]-](http://img.cochemist.com/ccimg/38100/38053-75-7_b.png)
![Silane, trichloro[(1S)-1-phenylethyl]-](http://img.cochemist.com/ccimg/38100/38053-74-6.png)
![Silane, trichloro[(1S)-1-phenylethyl]-](http://img.cochemist.com/ccimg/38100/38053-74-6_b.png)
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![Pyridine, 2-[(2-methoxyphenyl)ethynyl]-6-methyl-, hydrochloride](http://img.cochemist.com/ccimg/33700/33673-92-6_b.png)
![Benzene, 1-methoxy-2-[(4-methoxyphenyl)ethynyl]-](http://img.cochemist.com/ccimg/31800/31766-64-0.png)
![Benzene, 1-methoxy-2-[(4-methoxyphenyl)ethynyl]-](http://img.cochemist.com/ccimg/31800/31766-64-0_b.png)
![Benzene, 1-methoxy-2-[(1Z)-2-phenylethenyl]-](/data/chemimg/1775300/1898-14-2.png)
![Benzene, 1-methoxy-2-[(1Z)-2-phenylethenyl]-](/data/chemimg/1775300/1898-14-2_b.png)
![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[[[(1R)-1-methylheptyl]oxy]methyl]-](/data/chemimg/3737300/1446202-09-0.png)
![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[[[(1R)-1-methylheptyl]oxy]methyl]-](/data/chemimg/3737300/1446202-09-0_b.png)
![Benzene, 1,2-bis[[[(1S)-1-ethylhexyl]oxy]methyl]-4,5-diisocyano-3,6-dimethyl-](/data/chemimg/3737400/1446202-12-5.png)
![Benzene, 1,2-bis[[[(1S)-1-ethylhexyl]oxy]methyl]-4,5-diisocyano-3,6-dimethyl-](/data/chemimg/3737400/1446202-12-5_b.png)
![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[[(1R)-1-methylpropoxy]methyl]-](/data/chemimg/3737300/1229608-42-7.png)
![Benzene, 1,2-diisocyano-3,6-dimethyl-4,5-bis[[(1R)-1-methylpropoxy]methyl]-](/data/chemimg/3737300/1229608-42-7_b.png)
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![Silane, trichloro[(1R)-1-phenylpropyl]-](http://img.cochemist.com/ccimg/154400/154377-45-4_b.png)
![POLY[5,8-DIMETHYL-6,7-BIS(PROPOXYMETHYL)-2,3-QUINOXALINEDIYL]](http://img.cochemist.com/ccimg/144100/144043-03-8.png)
![POLY[5,8-DIMETHYL-6,7-BIS(PROPOXYMETHYL)-2,3-QUINOXALINEDIYL]](http://img.cochemist.com/ccimg/144100/144043-03-8_b.png)
![Silane, trichloro[(1S)-1-phenylpropyl]-](http://img.cochemist.com/ccimg/104000/103980-88-7.png)
![Silane, trichloro[(1S)-1-phenylpropyl]-](http://img.cochemist.com/ccimg/104000/103980-88-7_b.png)
![Phosphine sulfide, (2',3'-diisocyano-4'-methyl[1,1'-biphenyl]-2-yl)diphenyl-](/data/chemimg/3726100/1229608-40-5.png)
![Phosphine sulfide, (2',3'-diisocyano-4'-methyl[1,1'-biphenyl]-2-yl)diphenyl-](/data/chemimg/3726100/1229608-40-5_b.png)