Hydroxylation study of carbazole

Abstract

The primary products of the hydroxylation of carbazole were investigated. The four C-mono-hydroxycarbazoles were synthesized to serve as reference compounds. They were separated chromatographically on silicagel plates, and colour reactions were developed to identify them. The hydroxylation of carbazole by chemical systems that introduce the hydroxyl group directly onto aromatic rings, such as the Udenfriend Fe++ - ascorbic acid-oxygen system, produced only 3-hydroxy-carbazole of the four possible monohydroxycarbazoles. 3-Hydroxycarbazole was partially further oxidized by most hydroxylating system, but when homogeneous reaction was possible, or at elevated temperatures, it was completely oxidized. The principle products of the hydroxylation of carbazole were independent of the hydroxylating system used. The greater stability of 3-hydroxycarbazole compared to that of the other monohydroxycarbazoles is suggested to account for its predominance among the products of the hydroxylation of carbazole.