The Selective Preparation of N-Acylindigo

Abstract
The hitherto unknown N-acylindigo has been selectively prepared by heating the corresponding known N,N′-diacylindigo in aqueous pyridine. The data of N-acetyl, N-benzoyl, N-(p-toluoyl), N-(p-chlorobenzoyl), N-(p-nitrobenzoyl), and N-(3,5-dinitrobenzoyl)indigo are summarized.