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.