Catalyst-free facile synthesis of 2-(dihydropyridyl)benzothiazoles from (benzothiazol-2-yl)acrylonitriles: green route

Abstract

An efficient, metal-free, catalyst-free, and atom-economical “green” route for the synthesis of C-2-(dihydropyridyl)benzothiazoles is described. The synthesis was achieved by a [3 + 3] cycloaddition reaction of (benzo[d]thiazol-2-yl)acrylonitriles with cyclic 1,1-enediamines under mild conditions to furnish imidazo[1,2-a]pyridine-, pyrimidino[1,2-a]pyridine-, and diazapino[1,2-a]pyridine-incorporated benzothiazole moieties. The protocol was operationally simple, afforded products that were isolated directly by filtration, and obviated other purification techniques for the isolation of scaffolds. Furthermore, the strategy tolerated a wide range of substrates, as well as gram-scale synthesis, yielding the product in good-to-excellent yields, demonstrating its practicality and versatility. The absorption behaviour of the benzothiazole hybrid was also analysed. The method aligns with green chemistry principles, combining high atom economy with low environmental impact.