Hydroacylation of Activated Ketones Catalyzed by N-Heterocyclic Carbenes

摘要

Direct methods for the selective oxidation of a bonds are powerful bond-forming strategies in organic synthesis.One established approach to selectively oxidize C-H bonds utilizes transition metals capable of undergoing oxidative addition pathways.The rhodium(I)-catalyzed intramolecular hydroacylations of alkenes,reported from many laboratories including Bosnich,Larock,Jun,Brookhart,Shair,Fu,and Morehead,functionalize aldehydic C-H bonds for the synthesis of carbocycles.Interestingly,the development of analogous catalytic hydroacylation processes involving aldehydes and carbonyl pi systems has not received the same attention.We have been interested in developing approaches in which an organic molecule promotes multiple bond-forming steps in a single catalytic cycle.Herein,we report the hydroacylation of alpha-keto esters (2) with aldehydes (1) catalyzed by N-heterocyclic carbenes (eq 1).In this process,the carbene facilitates selective catalytic oxidation of a C-H bond with concomitant reduction of a ketone.