Synthesis of Heterocycles through Nucleophilic Additions to Acetylenic Esters

Abstract

This chapter highlights the use of acetylenic esters in the synthesis of different heterocycles, primarily involving nucleophilic additions. The chapter discusses the reaction of amines with acetylenic esters. The primary amines react with dimethyl acetylenedicarboxylate (DMAD), giving rise chiefly to the enamine fumarates. The preferential formation of the fumarates in these additions can be understood in terms of their relative stabilities, as compared to the corresponding maleates, due to internal hydrogen bonding. The enamine adducts formed in the reaction of aromatic amines with DMAD have been found to undergo cyclization leading to heterocyclic compounds, and the mode of these reactions is influenced by the reaction conditions, the catalyst employed, and also the nature of the functional groups present in the starting amine.