An expedient synthesis strategy to the 1,4-dihydropyridines and pyrido[1,2-a]quinoxalines: iodine catalyzed one-pot four-component domino reactions

Abstract

Another aspect concerning enaminone chemistry leading to the one-pot synthesis of functionalized novel 1,4-dihydropyridines and pyrido[1,2-a]quinoxalines has been described. By highly efficient, one-pot, iodine-catalyzed four-component reactions, combining one set of enamine intermediates and arylidene pyruvic acid (APA) in two procedures, heterocyclic skeletal diversity can be achieved. The synthesis involves reaction of the intermediates formed by the 1:1 interaction between primary amines (or o-phenylenediamine) and dialkyl acetylenedicarboxylate with pyruvic acid and benzaldehyde through an iodine-catalyzed Knoevenagel/Michael/cyclization sequence. The reaction is particularly attractive due to the following advantages: atom economy, optimum convergence, high bond-forming efficiency, and avoidance of tedious workup and purification of products. Significantly, the presence of an acidic group at the 9-position on the products make these compounds excellent precursors for further synthetic modifications to meet the need for diverse chemical inputs.