Lewis Base Effects in the Baylis−Hillman Reaction of Imines with Methyl Vinyl Ketone

Abstract

In the Baylis−Hillman reaction of N-benzylidene-4-methylbenzenesulfonamide with methyl vinyl ketone (MVK), we found that, in the presence of a catalytic amount of DMAP, PPh3 or DABCO as Lewis base, the Baylis−Hillman reaction can be greatly accelerated to give the normal Baylis−Hillman adducts 1 in good or very high yields. However, with PBu3 as a Lewis base, the abnormal Baylis−Hillman adducts 2 and 3 were formed under the same reaction conditions. The effect of the substituents was also examined and a plausible reaction mechanism proposed.