The first synthesis of 4-trifluoromethyl-2H-pyrans by palladium-catalyzed cyclization of (E)-3-alkynyl-3-trifluoromethyl allylic alcohols

The cross-coupling of (Z)-3-iodo-3-trifluoromethyl allylic alcohols 4 with terminal alkynes 5 in the presence of Pd(PPh3)4 and CuI gave conjugated (E)-3-alkynyl-3-trifluoromethyl allylic alcohols 2 in high yield. 4-Trifluoromethyl-2H-pyrans 7 were prepared from the cyclization of 2 using PdCl2(CH3CN)2 catalysis.