Oxidative photochemical cyclization of ethyl 3-(indol-3-yl)-3-oxo-2-phenylpropanoate derivatives: synthesis of benzo[a]carbazoles

摘要

6-Ethoxycarbonyl-5-hydroxy-benzo[a]carbazoles were prepared from ethyl 3-(1-methyl-1H-indol-3-yl)-3-oxopropanoates in two steps: the first step involved alpha-arylation of the indicated starting materials via Ullmann-Hurtley reaction; in the key second step, the thus formed coupling products underwent oxidative photocyclization to afford the benzo[a]carbazole ring. The present photocyclization features the use of CuBr2 to prompt the transformations, which could not be realized under the conventional conditions. (C) 2015 Elsevier Ltd. All rights reserved.