Syntheses of benzomorphan and related compounds. Part III. An alternate synthesis of 3‐substituted‐1,2,3,4,5,6‐hexahydro‐8‐hydroxy‐2,6‐methano‐6,11‐dimethyl‐3‐benzazocine

Abstract

Abstract Reduction of the appropriate Schiff bases gave 5‐benzylamino‐3‐methyl‐2‐pentene (XVII) and l‐benzylamino‐3‐methylpentane (XVIII), the condensation of which with methyl 3‐(4‐methoxyphenyl)‐2,3‐epoxypropionate afforded a mixture of the isomeric 1‐benzyl‐2‐(4‐methoxy‐benzyl)‐3,4‐dimethyl‐4‐hydroxypiperidines (XIXa and XIXb). The piperidinols were heated with hydrobromic acid, respectively, to afford 3‐benzyl‐1,2,3,4,5,6‐hexahydro‐8‐hydroxy‐2,6‐methano‐6,11‐dimethyl‐3‐benzazocine (II). Since the conversion of II to pentazocine (Ic) had already been accomplished, an alternate synthesis of Ic was achieved.