9-Oxobenzomorphans. II. A versatile process for the synthesis of 9-oxo-6,7-benzomorphans

Abstract

The synthesis of 5-allyl-2′-methoxy-2-methyl-9-oxo-, 2′-methoxy-2,5-dimethyl-9-oxo-, 5-allyl-2-cyclopropylmethyl-2′-methoxy-9-oxo-, and 5-(3-ethylenedioxy)butyl-2′-methoxy-3-methyl-9-oxo-6,7-benzomorphans (5a–d) by an improved process is described. It involves bromination of the 5,9b-dihydrobenz[e]indolines to the bromoiminium bromides, followed by hydrolysis with ammonium bicarbonate which converted them to 4-bromo-5,9b-dihydro-benz[e]indolines (in a fast step). These underwent hydration (in a slow step) followed by rearrangement to 5a–d. The course of these reactions was different when sodium, potassium, and ammonium hydroxides were substituted for ammonium bicarbonate.