Bicyclic guanidine catalyzed enantioselective isomerization reactions

Abstract

A chiral bicyclic guanidine was found to catalyze the isomerization of alkynes to chiral allenes with high ees. The axial chirality was efficiently transferred to functionalized butenolides and cycloaddition products. We have also successfully demonstrated the stereospecific synthesis of butenolide through allenoate cyclization with a catalytic cationic Au(I) complex.

We have also found that a Br?nsted-base catalyzed tandem isomerization-Michael reaction can be used to form useful heterocycles under mild conditions. This efficient method was applied to the synthesis of various functionalized 2-alkylidenetetrahydrofurans with excellent yields. Tandem isomerization-aza-Michael reaction with alkynyl-amines, alkynyl-amide and alkynyl-carbamates led to interesting piperidines, lactams and oxazolidinones. Asymmetric version of tandem isomerization-aza-Michael reaction was tested to give moderate ee using a chiral bicyclic guanidine as a catalyst.

We have discovered a Br?nsted-base catalyzed tandem Mannich-isomerization reaction between imines and itaconimides. Moderate to good ees were achieved with this reaction catalyzed by a chiral bicyclic guanidine.