Four-component reaction of N-alkylimidazoles(N-alkylbenzimidazoles), dialkyl but-2-ynedioate, N-alkylisatins and malononitrile

Abstract

Under catalyst-free conditions, the four-component reaction of N-alkylimidazole, dialkyl but-2-ynedioate, N-alkylisatins and malononitrile in tetrahydrofuran at room temperature afforded novel functionalized spiro[imidazo[1,2-a]pyridine-7,3′-indolines] in good yields. Moreover, a similar four-component reaction containing N-alkylbenzimidazole usually resulted in a mixture of spiro[benzimidazo[1,2-a]pyridine-6,3′-indoline] and spiro[benzimidazo[1,2-a]pyridine-7,3′-indoline] derivatives, which derives from two regioselective reaction modes of isatylidene malononitrile in the cyclocondensation reaction. The structures and formation mechanism of the different products were clearly elucidated.