Yoshihiro Ishimaru

Chemicals
References

Synthesis and Antiaromatic Properties of Highly Planar Dithiaamethyrin

Co-reporter:Dr. Yoshihiro Ishimaru;Naoyuki Shimoyama;Dr. Takashi Fujihara;Keigo Watanabe;Dr. Jun-ichiro Setsune

Chemistry – An Asian Journal 2015 Volume 10( Issue 2) pp:329-333

Publication Date(Web):

DOI:10.1002/asia.201403126

Abstract

2,5-Bis(4-propyl-2-pyrrolyl)thiophene was reacted with aryl aldehydes to afford large porphyrinoids; [24]dithiaamethyrin(1.0.0.1.0.0) and [36]trithianonaphyrin(1.0.0.1.0.0.1.0.0). X-ray crystallography of the dithiaamethyrin revealed a highly planar ring structure with mean plane deviation (MPD) value of 0.053 Å. A large positive NICS(0) value (+13.9 ppm) calculated for this planar 24π system unambiguously indicates an antiaromatic character that is consistent with a remarkably low field ¹H chemical shift of the inner NH proton at 24.0 ppm. The magnitude of the paratropic ring current effect in the 24π amethyrin framework in the free base form and the diprotonated form was discussed on the basis of the MPD value and the NICS value. The present dithiaamethyrin is much more strongly antiaromatic than the dodecaalkylamethyrin in their free base forms, but the order inversed in their diprotonated forms.

Design on head-to-tail directly linked homogeneous and heterogeneous cyclodextrin dimers and their evaluation of hydrophobic cavity

Co-reporter:Yoshihiro Isihimaru, Yasunori Kojo, Taich Masuda, Syunsuke Saito, Yu Yue, Yu Fujisaki

Tetrahedron Letters 2014 Volume 55(Issue 15) pp:2438-2441

Publication Date(Web):9 April 2014

DOI:10.1016/j.tetlet.2014.02.128

Covalent directly head-to-tail linked homogeneous and heterogeneous cyclodextrin (CD) dimers were synthesized, and that the reaction of 6-tosylated α-, β-, or γ-CD with a β-CD mono-oxyanion linked the second CD to the secondary hydroxyl side of β-CD was demonstrated. Moreover, deprotonation of α- and γ-CD using NaOH gave corresponding mono-oxyanions, which reacted with the 6-tosylated CDs to produce the CD dimers. The binding of the dimers to sodium 6-(4-tert-butylaniline)-2-naphthalenesulfonate (BNS) was investigated. The binding constant of the 6β–2β-CD dimer with BNS was estimated as 3.2 × 106 M−1, about 102 times larger than that of β-CD monomer.