Unprecedented formation of 2-oxaspiro[bicyclo[2.2.1]heptane-6,3′-indoline] derivatives from reaction of 3-phenacyalideneoxindole with malononitrile or ethyl cyanoacetate

Abstract

The reaction of malononitrile or ethyl cyanoacetate with two molecules of 3-phencylideneoxindoles in ethanol in the presence of piperidine at room temperature afforded novel 7-(1-benzyl-2-oxoindolin-3-yl)-2′-oxo-2-oxaspiro[bicyclo[2.2.1]heptane-6,3′-indoline] derivatives in good yields. Under similar reaction conditions, the reaction of cyanoacetamide with 3-phencylideneoxindoles resulted in polysubstituted 4-(2-oxoindolin-3-yl)-2-oxopyrrolidines. The stereochemistry of the reaction was well established by data from ¹H NMR spectra and single crystal structures and a plausible reaction mechanism is rationally proposed.