Mannich reactions. Synthesis of 4,5‐dihydropyrrolo[l,2‐a]quinoxalines, 2,3,4,5‐tetrahydro‐l<i>H</i>‐pyrrolo[l,2‐a] [l,4]diazepines and 5,6‐dihydro‐4<i>H</i>‐pyrrolo[ 1,2‐a] [ 1,4]benzodiazepines

Abstract

Abstract l‐(2‐Aminophenyl)pyrrole (I) and l‐[2‐(aminomethyl)]phenylpyrrole hydrochloride (III) undergo cyclization reactions with aldehydes and ketones to form 4,5‐dihydropyrrolo[l,2‐a]‐ quinoxalines and 5,6‐dihydropyrrolo[l,2‐a][l,4]benzodiazepines, respectively. It was also found that the use of the free base of compounds corresponding to III do not cyclize directly but lead instead to the intermediate Schiff bases which are subsequently cyclized to the desired benzodiazepines by treatment with hydrochloric acid.