Lewis Base Catalyzed Aza-Diels-Alder Type Reactions between Danishefsky’s Dienes in the Presence of Lewis Base Catalysts. An Efficient Method for the Synthesis of Substituted 2,3-Dihydropyridin-4-ones

Abstract

Aza-Diels-Alder type reactions of various imines with 1-methoxy-3-trimethylsilyloxy-1,3-butadiene (Danishefsky's diene) derivatives catalyzed by Lewis bases such as lithium methoxide are described. The reaction proceeds via a stepwise pathway, i.e. first by an imino-aldol reaction followed by the acid mediated annulation to afford the corresponding 2,3-dihydropyridin-4-ones in high yields. An appropriate choice of the substituents on nitrogen plays important roles both in addition of the silyl enolates and in the subsequent annulation to form the desired cycloadducts.