Furans to Benzofurans: Intramolecular Cross-Benzoin Reactions Catalysed by N-Heterocyclic Carbenes

Abstract

The first synthesis of dihydrobenzofuranones and benzofurans based on an intramolecular cross-benzoin reaction has been reported. Commercially available 3-furan carboxaldehydes are readily α-alkylated to furnish 3-formyl-2-furylcarbinols, which are further elaborated to the synthesis of benzofurans in good yields through sequential bismuth(III) chloride catalysed furfurylation and a novel NHC-promoted intramolecular cross-benzoin condensation reaction.