SYNTHESIS OF HETEROCYCLES FROM AZADIENES

Azadienes have become a useful tool for the construction of heterocyclic compounds. In the chapter, their application toward natural product synthesis through pericyclic processes is reviewed and their great potential in the field of the alkaloid chemistry is demonstrated. The chapter describes the utility of azadienes and 1,3-diazadienes in the synthesis of heterocycles of various ring sizes. The [4 + 2] cycloaddition reactions of azadienes are reviewed in the chapter, focusing on Diels–Alder cycloadditions processes. It also summarizes the cycloaddition reactions of heterocyclic azadienes. The chapter describes the chemistry of 2-azadienes directed for the preparation of five- to seven-membered heterocycles; the study of electronically neutral 2-azadienes is an important subject. The chemistry of diazadienes is focused in the chapter in the utility of 1, 3-diazadienes. The electrocyclic ring closure reactions of vinyl or aryl 2-azadienes (azatrienes) involving six electrons occur at moderate temperatures and, in this respect, several pyridine syntheses are described in the chapter. © 1993, Academic Press Inc. All rights reserved.