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A novel and general alpha-regioselective and highly enantioselective prenylation of aldehydes.

This communication describes a novel and general method for the alpha-regioselective prenylation of carbonyl compounds. This method which employs chiral gamma-prenyl-1,5 diol as the prenyl source using a catalytic amount of Lewis or Brønsted acid affords the products in excellent enantioselectivies (up to 98% ee) and good yields (up to 95% yield). Furthermore, the reaction is highly chemoselective, reacting selectively with the aldehyde without affecting the enone and the alpha,beta-unsaturated ester functionalities. Detailed mechanistic studies disclose the facile epimerization of aromatic alcohol in dichloromethane in the presence of In(OTf)3. The use of non-polar solvents such as hexane in the presence of In(OTf)3 or TfOH effectively suppresses this epimerization.