Synthesis of 11-phenyl-2,3,4,5-tetrahydro-1H-(1,4)diazepino(1,2-a)indoles and 1-(3-aminopropyl)-2-hydroxymethyl-3-phenylindoles as 5-hydroxytryptamine antagonists

A series of novel 11-phenyl-2,3,4,5-tetrahydro-1H-(1,4)diazepino(1,2-a) indoles (5a-f) and 1-(3-aminopropyl)-2-hydroxymethyl-3-phenylindoles (6a-f) are reported. The compounds (5a-f) were prepared by the lithium aluminum hydride (LAH) reduction of corresponding 11-phenyl-1H-1-oxo-2,3,4,5-tetrahydro(1,4)diazepino(1,2-a)indoles (4a-f). The precursors (4a-f) were, in turn, prepared by the catalytic reduction of 1-(2-cyanoethyl)-3-phenylindole-2-carboxylates (2a-f) and cyclization of the resulting 1-(3-aminopropyl)-3-phenylindole-2-carboxylates (3a-f) with sodium hydride in xylene. The LAH reduction of 2a-f gave exclusively 1-(3-aminopropyl)-2-hydroxymethyl-3-phenylindoles (6a-f) and not the diazepinoindoles (5a-f) which were expected. The title compounds and the intermediates have been screened for their anti-5-hydroxytryptamine (anti-5-HT) activity. The most potent anti-5-HT compounds of this series, 6a and 6e, were found to be weak compared with cyproheptadiene, a standard anti-5-HT drug.