Syntheses of 3-Aryl Tetrahydroisoquinolines via an Intermolecular [4 + 2] Cycloaddition of Sultines with Imines.

The development of an intermolecular aza-Diels-Alder (DA) cycloaddition of sultines and imines is reported. By exploiting sultines as o -quinodimethane precursors and aryl imines as dienophiles in the presence of Cu(OTf) 2 , an aza-DA reaction proceeds to provide a wide variety of 3-aryl tetrahydroisoquionlines in moderate to excellent yield (up to 89%). The synthetic utility of these products was demonstrated in the preparation of tetracyclic N-heterocycles, including a tetrahydroprotoberberine skeleton.