A new synthetic procedure to spiro[cyclohexane-1,3′-indoline]-2′,4-diones

A new synthetic pathway to spiro[cyclohexane-1,3′-indoline]-2′,4-diones was found starting from 3-chloromethylene-2-indolones and Danishefskyʹs diene . Their synthesis consists of several steps involving the formation of the cycloadducts, the 6-chloro-4-trimethylsilyloxy-2-methoxyspiro[cyclohex-3-en-1,3′-indolin]-2′-one derivatives, transformed into spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones via 6-chloro-spiro[cyclohex-2-en-1,3′-indoline]-2′,4-dione intermediates. The reduction of spiro[cyclohexa-2,5-dien-1,3′-indoline]-2′,4-diones gave spiro[cyclohexane-1,3′-indoline]-2′,4-diones . Using a ‘one pot reaction’, starting from and , compounds were obtained in satisfactory overall yield.