3 [formula omitted]-azepines and related systems. Part 4. Preparation of 3 [formula omitted]-azepin-2-ones and 6 [formula omitted]-azepino[2,1-b]quinazolin-12-ones by photo-induced ring expansions of aryl azides

Abstract

Photolysis of a series of p-substituted phenyl azides (p-X-C 6H 4N 3; X= CO 2Me, CO 2Et, CN, CF 3, SO 2NH 2, CO 2CHPh 2, COMe, CHO, and NO 2) in 1:1 (v/v) THF-water solution produces, in the majority of cases, a 5-substituted-3 H -azepine-2-one. In a like manner, 3 H -azepin-2-one-3-carboxylates can be prepared from 5-substituted-2-azidobenzoates, providing the 5-substituent is electron-withdrawing. 3 H -Azepin-2-one mono- and di-carboxylic acids, the former in admixture with decarboxylated material, and 6 H -azepino[2,1-b]quinazolin-12-ones, are obtained by irradiation of 2-azidobenzoic acid and of 5-azidoisophthalic acid, respectively. The mode of formation of the azepino-quinazolinones is discussed.