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

Article abstract of DOI:10.1016/S0040-4020(01)96138-1

Photolysis of a series of p-substituted phenyl azides (p-X-C₆H₄N₃; X= CO₂Me, CO₂Et, CN, CF₃, SO₂NH₂, CO₂CHPh₂, COMe, CHO, and NO₂) in 1:1 (v/v) THF-water solution produces, in the majority of cases, a 5-substituted-3H-azepine-2-one. In a like manner, 3H-azepin-2-one-3-carboxylates can be prepared from 5-substituted-2-azidobenzoates, providing the 5-substituent is electron-withdrawing. 3H-Azepin-2-one mono- and di-carboxylic acids, the former in admixture with decarboxylated material, and 6H-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.