The reactions of 3,4-dehydroproline with substituted isatins

Abstract

Substituted isatins having a free NH group react with 3,4- dehydroproline, like isatin itself, to give 3-(1-pyrrolyl)oxindoles. Analysis of the N.M.R. spectra of the 5-nitro and 5,7-dibromo analogues confirms that the isatins condense at their 3- and not their 2-carbonyl groups. N-Alkylisatins form similar products which, depending on the conditions, may react with a further molecule of the isatin to give unstable di-adducts whose structures have been determined.