Synthesis of tetrahydro-3-benzazepines

A synthetic route toward tetrahdro-3-benzazepines 1a-f starting with 2a and 2b in modest total yield is described. The facile route was carried by Henry reaction of aldehydes 3a-e with nitroalkanes and NH4OAc at reflux, reduction of the resulting nitroalkenes 4a-h with LAH at rt followed by protection with K2CO3 and PhSO2Cl at rt, one-pot oxidative cleavage annulation of olefins 5a-h with the one-pot combination of OsO4/NaIO4 at reflux, and hydrogenation of the corresponding enamines 6a-f. Aldehydes 3a-e was prepared from 2a and 2b in moderate yield of three-step.