Reaction of Benzyl Grignard Reagents with Trifluoroacetyldihydropyrans and Other Cyclic β-Alkoxy-α,β-Unsaturated Trifluoromethylketones

Benzyl Grignard reagents react with cyclic β-alkoxy-α,β-unsaturated trifluoromethyl ketones by 1,2-addition to afford unsaturated allylic alcohols in high yield. The factors determining the balance between 1,2- and 1,4-addition to unsaturated ketones are discussed. The structures of major and minor products are established by single crystal X-ray diffraction studies.