Luche reduction

The Luche reduction converts selectively α,β-unsaturated ketones to allylic alcohols using a mixture of lanthanide chlorides and sodium borohydride.

Mechanism:

The Lewis acidic cesium chloride activates methanol that replaces some of the hydrides of sodium borohydrides making it harder and more prone for a 1,2-attack on the carbonyl compounds.

 

The cesium chloride also acts as an Lewis catalyst to increase the electrophilicity of the carbonyl compound.

Literature:

Lanthanides in organic chemistry. 1. Selective 1,2 reductions of conjugated ketones. Luche, J. L. J. Am. Chem. Soc. 1978, 100, 2226-2227.

Lanthanoids in organic synthesis. 6. Reduction of .alpha.-enones by sodium borohydride in the presence of lanthanoid chlorides: synthetic and mechanistic aspects.                 Andre L. Gemal, Jean Louis Luche J. Am. Chem. Soc., 1981, 103 (18),  5454–5459.

Stereochemically Controlled Asymmetric 1,2-Reduction of Enones Mediated by a Chiral Sulfoxide Moiety and a Lanthanum(III) Ion. Shigeyasu Motohashi, Kouichi Nagase, Toshinori Nakakita, Takeshi Matsuo, Yoshikazu Yoshida, Takashi Kawakubo, Motofumi Miura*, Masaharu Toriyama, and Mikhail V. Barybin J. Org. Chem., 2011, 76 (10), 3922–3936.