The meisenheimer rearrangement in heterocyclic synthesis. II: Synthesis and X-Ray crystal structure of a tetrahydro-1h-2, 3-benzoxazocine and preparation of a hexahydro-2, 3-benzoxazonine

The heterocyclic derivatives, 8, 9-dimethoxy-3-methyl-1-phenyl-3, 4, 5, 6-tetrahydro-1H-2, 3-benzox- azocine (3a) and 9, 10-dimethoxy-3-methyl-1-phenyl-1, 3, 4, 5, 6, 7-hexahydro-2, 3-benzoxazonine (3b), examples of two new ring systems, have been prepared by Meisenheimer rearrangement of the corresponding 2-benzazepine and 2-benzazocine A-oxide derivatives (2a) and (2b). The Bischler- Napieralski-type cyclization reaction was used in the preparation of the tertiary amine precursors of these N-oxides; reaction conditions for the cyclization were critical and phosphorus oxychloride in refluxing butanenitrile was found to give the best yields of the seven- or eight-membered cyclic imine intermediates. Reductive cleavage of the benzoxazocine derivative (3a) with zinc in acetic acid followed by N-methylation gave the expected product, [2-{3-(dimethylamino)propyl)-4, 5-di- methoxyphenyl]phenylmethanol (12). The crystal and molecular structure of (3a) has been determined by X-ray crystallographic analysis.