Lewis acid-catalyzed diastereoselective carbofunctionalization of bicyclobutanes employing naphthols

Abstract

Traditional radical-mediated ring-opening of bicyclo[1.1.0]butanes (BCBs) for cyclobutane synthesis suffers from poor diastereoselectivity. Although few reports on BCB ring-opening via polar mechanisms are available, the Lewis acid-catalyzed diastereoselective ring-opening of BCBs using carbon nucleophiles is still underdeveloped. Herein, we report a mild and diastereoselective Bi(OTf)₃-catalyzed ring-opening of BCBs employing 2-naphthols. The anticipated carbofunctionalized trisubstituted cyclobutanes were obtained via a bicoordinated bismuth complex and the products are formed in good to excellent yields with high regio- and diastereoselectivity. The scope of the reaction was further extended using electron-rich phenols and naphthylamine. The functionalization of the synthesized trisubstituted cyclobutanes shows the synthetic utility of the present method.