Concise, efficient and practical assembly of bromo-5,6-dimethoxyindole building blocks

A concise, efficient and simple route to a series of bromoindole building blocks is described. The synthetic routes are highlighted by purification-free preparation of o-nitrocinnamate intermediates and clean, modified Cadogan indole syntheses. The scope of this indole synthesis has been explored and expanded through the use of a range of solvents and easily removable phosphine reagents. (C) 2011 Elsevier Ltd. All rights reserved.