Facile synthesis of N-acyl-2-pyrrolines

In conjunction with our studies of the amidoalkylation reaction,' multigram quantities of N-acyl-2-pyrrolines (1) were needed. Interestingly, only a few methods for the synthesis of this class of compounds had been reported. Stille and co-workers prepared 1 by a novel transition metal mediated isomerization of N-acyl-3-pyrrolines2 and also cyclized (acy1amino)butyraldehydes to produce le3 Although these methods are excellent for qmall-scale preparation, large-scale reactions would entail considerable expense.