Construction of dispirocyclohexyl-3,3′-bisoxindole and dispirocyclopentyl-3,3′-bisoxindole via domino cycloaddition reactions of N-benzylbenzimidazolium salts with 2-(2-oxoindolin-3-ylidene)acetates

Abstract

The cycloaddition reaction of N-benzyl-N-phenacylbenzimidazolium salts with two molecules of 2-(2-oxoindolin-3-ylidene)acetate in ethanol in the presence of triethylamine as base afforded functionalized dispirocyclohexyl-3,3′-bisoxindoles in good yields. Alternatively, the similar reaction of N-benzyl-N-(alkoxycarbonylmethyl)benzimidazolium salts with two molecules of 2-(2-oxoindolin-3-ylidene)acetate resulted in dispirocyclopentyl-3,3′-bisoxindole derivatives in good yields and with high diastereoselectivity.