Transition metal-free one-pot cascade synthesis of 7-oxa-2-azatricyclo[7.4.0.02,6]trideca-1(9),10,12-trien-3-ones from biomass-derived levulinic acid under mild conditions

Abstract

An efficient, environmentally benign, transition-metal free, tandem C–N, C–O bond formation reaction is developed for the synthesis of tricyclic 7-oxa-2-azatricyclo[7.4.0.0^2,6]trideca-1(9),10,12-trien-3-ones and their homologs from easily available starting materials, including renewable levulinic acid, a keto acid. The reaction of keto acids with methyl chloroformate and variously substituted o-aminobenzyl alcohols using triethylamine as a base in toluene at room temperature gave good to excellent yields. This newly developed protocol was successfully utilized for the synthesis of a variety of polycyclic 7-oxa-2-azatricyclo[7.4.0.0^2,6]trideca-1(9),10,12-trien-3-ones and related compounds.