An efficient synthesis of cyclic urethanes from Boc-protected amino acids through a metal triflate-catalyzed intramolecular diazocarbonyl insertion reaction

A simple and efficient synthesis of cyclic urethanes and related oxazinanones 1a–l from diazoketones 3a–l is described. The transformation involves generation of carbenes by activation of diazo groups using metal triflates in intramolecular diazocarbonyl insertion reactions in high overall yields.