Sequential Catalytic Asymmetric Allylic Transfer Reaction: Enantioselective and Diastereoselective Construction of Tetrahydropyran Units

Useful tetrahydropyran units such as 3 can be prepared with high diastereoselectivity (d.r.>30:1). A key step is the catalytic asymmetric allyl-transfer reaction from 1 to achiral aldehydes catalyzed by [{(R)-binol}TiIV{OCH(CF3)2}2] to give 2 (90–97 % ee). A second allyl-transfer reaction from 2 to a carbonyl compound leads to 3. binol=2,2′-binaphthol.