Smiles Rearrangement in Hydrazonyl Systems: Extension of a Recent 4H-1,3,4-Benzoxadiazine Synthesis

Abstract

Hydrazonyl aryl ethers derived from hydrazonyl halides Ar1CBr = NNHC6H3XY (2, 4) and (a) o-and p-nitrophenols or (b) pentachlorophenol undergo a facile base-catalyzed Smiles rearrangement to N-aroyl-N′,N′-diarylhydrazines typified by:[Formula: see text]e.g. 6 → 7, 8 → 9, 10 → 11.If the 2-substituent X is Br or F and the 4-substituent Y is electron attracting, the N-aroyl-N′,N′-diaryl-hydrazines can be cyclized under basic conditions to 4-aryl-4H-1,3,4-benzoxadiazines by displacement of X, i.e. 7 → 13, 9 → 14. However, in the analogous cyclization of N′-benzoyl-N′-(2,4-dibromophenyl)-N′-pentachlorophenylhydrazine (11), chlorine rather than bromine is displaced and the migrating ring (Ar2 = C6Cl5) in 10 → 11 becomes the benzene ring of the benzoxadiazine, i.e. 11 → 15.Independent syntheses of two 4-aryl-4H-1,3,4-benzoxadiazines (13a and 14), from 7-bromo-2-phenyl-4H-1,3,4-benzoxadiazine (5a) and o- and p-fluoronitrobenzene respectively, are reported.