Co-reporter:Vinoth Kumar Chenniappan and Ronald J. Rahaim
Organic Letters 2016 Volume 18(Issue 19) pp:5090-5093
Publication Date(Web):September 28, 2016
DOI:10.1021/acs.orglett.6b02537
α,β-Unsaturated amides are important building blocks and are key structural elements in a number of biologically active natural products. Despite their importance and prevalence, few methods exist to prepare conjugated amides directly and modularly. To address this gap, a titanium-promoted coupling of alkynes and isocyanates has been developed. The method is highly stereoselective, producing only the E isomer with good chemoselectivity and regioselectivity (>95/5), for unsymmetrical internal alkynes that contain a steric bias. The reactive titanacyclopentene intermediate formed from the coupling of the alkyne and isocyanate was additionally reacted with various electrophiles to access tetrasubstituted enamides.
Co-reporter:Sajan Silwal, Ronald J. Rahaim
Tetrahedron Letters 2015 Volume 56(Issue 42) pp:5738-5742
Publication Date(Web):14 October 2015
DOI:10.1016/j.tetlet.2015.09.021
A method for the modular one-pot synthesis of tetra-substituted furans utilizing alkynes, Weinreb amides, and non-enolizable aldehydes has been developed. Under this titanium promoted method, furans were prepared in moderate yields with high levels of regioselectivity. The system showed good chemoselectivity tolerating aromatic and aliphatic bromides, chlorides, and fluorides, heteroaromatics, alkenes, and silyl ethers.
Co-reporter:Jill A. Muchnij, Farai B. Kwaramba, and Ronald J. Rahaim
Organic Letters 2014 Volume 16(Issue 5) pp:1330-1333
Publication Date(Web):February 19, 2014
DOI:10.1021/ol5000549
A selective iridium catalyzed hydrosilylation of alkenes in the presence of more reactive alkynes is described. By utilizing [IrCl(COD)]2 in the presence of excess COD, hydrosilylation of alkenes and alkynes with ethynylsilanes is achieved with good chemo- and regioselectivity. This approach goes against the traditional reactivity trends of platinum and rhodium catalysts and allows access to highly substituted silicon alkyne tethers.
Co-reporter:Sajan Silwal and Ronald J. Rahaim
The Journal of Organic Chemistry 2014 Volume 79(Issue 17) pp:8469-8476
Publication Date(Web):August 13, 2014
DOI:10.1021/jo5014417
A modular titanium-promoted coupling of unsymmetrical internal alkynes with Weinreb amides is described. The coupling reaction takes place at room temperature and affords E-trisubstituted enones in moderate to good yields with high levels of regioselectivity. The system shows moderate chemoselectivity.