The Meisenheimer rearrangement in heterocyclic synthesis. III. Derivatives of the 1H-[1,2]oxazepino[6,5-b]indole, thieno[2,3-e][1,2]oxazepine and [l]benzothieno[3,2-e][1,2]

The new heterocyclic derivatives 3-methyl-1-phenyl-34,5,10-tetrahydro- 1H-[1,2]oxazepino[6,5-b]-indole (5c), 6-methyl-4-phenyl-4,6,7,8- tetrahydrothieno[2,3-e][1,2]oxazepine (6f), and 3-methyl-1-phenyl- 1,3,4,5-tetrahydro[1]benzothieno[3,2-e][1,2]oxazepine (7c) were prepared in good yield by thermal Meisenheimer rearrangement of the corresponding tertiary amine N-oxide precursors. No such rearrangement occurred on heating the N-oxides of the fused bicyclic systems 2,3,11,12-tetramethoxy-5,8,9,13b-tetrahydro-6H-dibenzo[a,h]quinolizine (3) and 8,9-dimethoxy-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinoline (4). The reduction of (5c), (6f) and (7c) with zinc in acetic acid is also described.