Ene-Type Reaction of Trifluoroacetaldehyde Hemiacetal with Ene Compounds in the Presence of a Lewis Acid.

Abstract Reaction of trifluoroacetaldehyde ethyl hemiacetal with ene compounds in the presence of a Lewis acid gives α-trifluoromethylated homoallyl alcohols, the same products as those from the ene reaction of trifluoroacetaldehyde, in moderate to good yields. Boron trifluoride etherate was found to be most effective in this reaction. This method eliminated many difficulties encountered on the ene reaction of trifluoroacetaldehyde, which is a gas at room temperature and polymerizes to insoluble polymer in the presence of a Lewis acid.