The DIBAL reduction of 2-phenylethyl 3,3,3-trifluoro-2-methylpropionate 2 at −78 °C afforded the aluminum acetal 3, and this intermediate, on worming up to 0 °C, was found to slowly decompose into the corresponding aldehyde 4, which smoothly reacted with appropriate nucleophiles in a one-pot manner in good to excellent yields with up to 93% diastereoselectivity.
[GRAPHICS]Michael addition of various enolates toward gamma -CH3-nFn-alpha,beta -unsaturated ketones (n = 1-3) was proven to smoothly furnish the 1,4-adducts with high si face selectivities which monotonously decreased by reduction in the number of fluorines. Although the Felkin-Anh model correctly anticipates the present stereochemical outcome only with E-acceptors, the hyperconjugative stabilization of transition states by electron donation from the allylic substituents (the Cieplak rule) successfully explains the pi -facial preference of both acceptors at least in a qualitative level.