Synthesis of Functionalized Furans via Chemoselective Reduction/Wittig Reaction Using Catalytic Triethylamine and Phosphine

An efficient protocol for the synthesis of highly functionalized furans via intramolecular Wittig reaction has been developed using catalytic amounts of phosphine and triethylamine. Silyl chloride served as the initial promoter to activate the phosphine oxide. Reduction of the activated phosphine oxide by hydrosilane resulted in generation of phosphine, while decomposition of Et₃N·HCl resulted in regeneration of base, which mediated formation of phosphorus ylide. Remarkably, the in situ generated byproduct, Et₃N·HCl, also catalyzes reduction of phosphine oxide.