Catalyst-Enabled Site-Divergent Stereoselective Michael Reactions: Overriding Intrinsic Reactivity of Enynyl Carbonyl Acceptors

摘要

A site-divergent stereoselective Michael reaction system is developed based on the identification of two distinct catalysts. Cinchonidine-derived thiourea catalyzes the 1,4-addition of prochiral azlactone enolates to enynyl N-acyl pyrazoles in a highly diastereo- and enantioselective manner to give stereochemically defined alkynes, while P-spiro chiral triaminoiminophosphorane catalytically controls the stereoselective 1,6-addition and the consecutive gamma-protonation of the vinylogous enolate intermediate to afford Z,E-configured conjugated dienes. This 1,6-adduct serves as a valuable precursor for the synthesis of a 2-amino-2-deoxy sugar.