The photolysis of o-azidobenzoic acid derivatives: a practicable synthesis of 2-alkoxy-3-alkoxycarbonyl-3H-azepines
Abstract
Photolysis of several o-azidobenzoic acid derivatives (o-N3C6H4COR; R = OH, Cl, OMe, OPh, SPh, NH2, NHAr, and OBz) in methanol, or methanol–tetrahydrofuran solution, yields in the majority of cases 3-substituted 2-methoxy-3H-azepines. Substituted methyl 2-azidobenzoates (X-2-N3C6H3CO2Me; X = Cl, OMe, NO2, Br, CO2Me, and CO2H) give the correspondingly substituted 2-methoxy-3-methoxycarbonyl-3H-azepines depending on the nature and position of the substituent group (X). In contrast, thermolysis of methyl o-azidobenzoate in alcohol solution gives mixtures of 3H-azepines and triplet nitrene derived products.