Enantioselective synthesis of mixed 3,3′-bisindoles via a phosphine-catalyzed umpolung γ-addition of 3′-indolyl-3-oxindoles to allenoates

Abstract

An enantioselective umpolung γ-addition reaction of 3′-indolyl-3-oxindoles to allenoates catalyzed by amino acid-derived bifunctional phosphine catalysts has been developed. A wide range of chiral mixed 3,3′-bisindoles scaffolds containing an all-carbon quaternary stereogenic center were obtained in high yields and with excellent enantioselectivities. 3,3′-Bisindoles are valuable synthetic intermediates, the employment of which led to formal total syntheses of (+)-Chimonanthine, (+)-Folicanthine and (?)-Calycanthine, as well as facile creation of useful pyrrolidinoindoline core structure. © 2020 Science China Press