Studies on the syntheses of analgesics. Part XXXII . An alternative synthesis of 1,2,3,4,5,6‐Hexahydro‐8‐hydroxy‐6,11‐dimethyl‐3‐(3‐methyl‐2‐butenyl)‐2,6‐methano‐3‐benzazoeine [Studies on the syntheses of heterocyclic compounds. Part CDLXXX ]

Bischler‐Napieralski reaction of the amides (VIII and IX), derived from the 3‐methyl‐3‐pentenylamine (III) with the phenylacetic acid derivatives (V ∼ VII), gave the 5,6‐dihydropyridines (XII and XIII), which were reduced, followed by N ‐benzylation, to afford the 1,2,5,6‐tetrahydropyridines (XIX ∼ XXI). Grewe‐type cyclization of these compounds gave 3‐benzyl‐3‐benzazocine (II), which was already converted into pentazocine (Ic). Moreover, the 1,2,5,6‐tetrahydropyridines (XIX ∼ XXI) were also obtained from the 2‐benzylidene‐1,2,5,6‐tetrahydropyridine (XVII ∼ XVIII) from the N ‐benzylamine (IV) of III via the amides (X and XI).