Cyclization of Phenyl Azides with Homoallylic or Allylic Ortho Substituents and the Consequences of Triazoline Fragmentation

Article abstract of DOI:10.1021/jo00333a008

o-(Allyloxy)phenyl azide (1) and 14 derivatives substituted on the allyl group were thermolyzed at 110-120 deg C to form benzoxazines (16), dihydroazirinobenzoxazines (17), or 3-alkenylbenzomorpholines (18, 19) through fragmentation of intermediate triazolines.With substituted allyl groups, the geometrical isomers gave the same products in the same ratio, except in the case of o-(β,γ-dimethylallyl)phenyl azide.Rearrangement by phenyl migrations occured with the β-phenylallyl compound. o-Allylphenyl azide (27a), (o-azidophenyl)acetaldehyde (27b), and o-<(cis-1-propenyl)oxy>phenyl azide (27c) required temperatures of 155-200 deg C for thermolysis and yielded 2-methylindole, oxindole, and 2-ethylbenzoxazole, respectively, by nitrene insertion.