Deacylation of Pyrrole and other Aromatic Ketones

Article abstract of DOI:10.1021/jo00189a002

Ethyl 4-acetyl-3,5-dimethyl-1H-pyrrole-2-carboxylate (1a) reacts rapidly with ethylene glycol in refluxing benzene with p-toluenesulfonic acid or perchloric acid as a catalyst to give ethyl 3,5-dimethyl-1H-pyrrole-2-carboxylate (3) in high yield (96 percent).Various 2- and 3-acylpyrroles can be efficiently deacylated by using this procedure.Other ketones which undergo deacylation include phenyl(2-phenylindol-3-yl)methanone (19), 1-(5-methyl-1-phenylpyrazol-4-yl)ethanone (20), and 2,4-dimethoxybenzophenone.Certain pyrrole ketones where the acyl group is flanked by two ring methyl groups are also cleaved under acidic conditions by using ethanedithiol.