Catalyticasymmetric protonation of chiral calcium enolates was performed. Chiral calcium enolates, prepared in situ from imides and malonates via 1,4-addition in the presence of catalytic amounts of Ca(OEt)(2), Ph-PyBox, and achiral phenol, were smoothly protonated to afford adducts bearing tertiary asymmetric carbons in high yields with high enantioselectivities. The adducts were readily converted
Organocatalytic enantioselective transient enolate protonation in conjugate addition of thioacetic acid to α-substituted N-acryloyloxazolidinones
作者:Rajshekhar A. Unhale、Nirmal K. Rana、Vinod K. Singh
DOI:10.1016/j.tetlet.2013.01.004
日期:2013.4
Organocatalytic conjugate addition of thioacetic acid to a series of α-substituted N-acryloyloxazolidin-2-ones followed by enantioselectiveprotonation has been studied in the presence of thiourea catalysts derived from cinchona alkaloids. Conjugate addition/protonation adducts have been obtained up to 97% ee and high yields. The methodology could serve as an easy and practical route to the syntheses
efficient electrochemical Ni-catalyzed alkene hydrogenation is described. The reaction features outstanding substrate generality and functional group compatibility, and distinct chemoselectivity. Notably, hydrodebromination of alkyl and aryl bromides can be realized using the same reaction system with a different ligand, and high chemoselectivity between hydrogenation of alkene and hydrodebromination could