Synthesis of α-CF3-Substituted O-Heterocycles via Ligand-Controlled Cycloaddition of (E)-β-Trifluoromethylated Enones with π-Allylpalladium 1,4-Dipoles

Palladium-catalyzed and ligand-controlled cycloaddition of (E)-β-trifluoromethylated enones has been described, providing powerful synthetic strategies for two α-CF3-substituted O-heterocycles, tetrahydro-2H-pyrans and 5-oxaspiro[2.4]heptanes. The readily available substrates bearing various functional groups have shown variable product chemoselectivities. The salient features also included novel products with potential values and diverse derivatizations. The mechanistic investigations revealed the stereochemistry of the O-heterocyclic products.