Ring-expansion of azidobenzenesulphonamides and azidobenzamides

Abstract

4-Azidobenzenesulphonamides and 2-and 4-azidobenzamides undergo phototransformation to 2-alkoxy-3H-azepines in alcohols but the yields are low. Ring-expansion of 4-azidobenzenesulphonamide and 4-azidobenzenesulphonylguanidine in aqueous tetrahydrofuran to 3H-azepin-2(1H)-ones proceeds via a singlet nitrene pathway;thermolysis of 4-azidobenzenesulphonamide in aqueous dioxane gave only the triplet-derived product, sulphanilamide. Efficient de-azidation of 4-azidobenzenesulphonamides and 4-azidobenzamides can be accomplished by heating the azides at 105 °C in hydrazine hydrate.

The crystallographic analysis of 5-sulphamoyl-3H-azepin-2(1H)-one shows the molecule to be nonplanar with the azepine ring puckered in a boat form. The lactam configuration is confirmed with the carbonyl group having a bond length of 1.231 Å.