Reduction of certain oxindoles and isatins with lithium aluminium hydride

Abstract

Reduction by lithium aluminium hydride of the adducts from the interaction of 3,4-dehydroproline and various isatins is described. The parent mono-adduct, 3-(1-pyrrolyl)oxindole, is normally inert but yields indole under special conditions. The 1-methyl and 1-ethyl analogues give mixtures of the corresponding 3-(1-pyrrolyl)-indoles and 3-(1-pyrrolyl)indolines. These indolines are extremely weak bases. The di-adduct from 1-methylisatin gives products which confirm its hemiacetal structure.