Biphenyl dicarboxylates from ethene and bifuran dimethyl esters

Abstract

The substrate scope of the Diels-Alder-Dehydration reaction was expanded to the deactivated bifuran structure. Dimethyl biphenyl-4,4′-dicarboxylate (1) and methyl 5- [4-(methoxycarbonyl)phenyl]-2-furoate (2) were synthesized from dimethyl 2,2′-bifuran-5,5′-dicarboxylate (3) via metal-triflate-catalyzed Diels-Alder-Dehydration reaction with ethene. A 31% yield of (1) was obtained using Sc(OTf)3 catalyst, and a 76.6% yield of (2) was obtained using La(OTf)3 catalyst under moderate reaction conditions. This approach is inherently selective to the 4,4′-dicarboxylates, and bypasses the methyl-group oxidation step of the dimethyl-biphenyl route.