Chemoselective synthesis of tetrasubstituted furans via intramolecular Wittig reactions: Mechanism and theoretical analysis

An efficient synthesis of tetrasubstituted furans was achieved from the corresponding α,β-unsaturated ketone derivatives, acid chlorides, and Bu₃P in the presence of Et₃N via a chemoselective intramolecular Wittig reaction as the key step. The presence of an additional electron-withdrawing group in the α-position of Michael acceptors controlled the chemoselectivities of presumable phosphorus ylides in the intramolecular Wittig reactions, and their mechanisms were also investigated by DFT calculations.