Preparation of indole derivatives

Abstract

An improved process for preparing indole derivatives of the formula, ##STR1## wherein R.sub.1 and R.sub.2 each are hydrogen, halogen, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkoxy, nitro, cyano or trifluoromethyl, or when taken together, form methylenedioxy; R.sub.3 is hydrogen, halogen, C.sub.1 -C.sub.3 alkyl, C.sub.1 -C.sub.3 alkoxy, nitro, cyano or dimethylamino; and R.sub.4 is hydrogen or halogen, which comprises cyclizing a compound of the formula, ##STR2## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as defined above, with an acidic condensing agent. The indole derivatives of the formula (I) mentioned above are useful as a key intermediate for the preparation of benzodiazepines, which are useful as tranquilizers, muscle relaxants and the like.

Dependencies are inferred from the claim text.