Synthesis of Highly Substituted Imidazo[1,5-a]quinoxalines Through a Multicomponent Reaction Followed by Deprotection-Cyclization

摘要

An operationally simple and efficient, one-pot, two-step methodology has been developed for the assembly of medicinally important imidazo[1,5-a]quinoxalines. The protocol involves the multicomponent reaction of aryl aldehydes, ortho-N-Boc-phenylenediamines and azidochalcones in the presence of erbium triflate as a Lewis acid catalyst, followed by deprotection-cyclization with 10% trifluoroacetic acid, furnishing the desired compounds in moderate to good yields. By virtue of their convergence, two aromatic rings and four new bonds are generated during the course of this reaction protocol. The structure of one of the compounds was proved by X-ray crystallography.