It is known that early main group complexes show lanthanide-like reactivity and coordination behavior, thus it is not surprising that heavier alkaline-earth metals are often compared to early f-block lanthanides.<i>Attention has been focused on calcium-catalyzed reactions as calcium, the fifth most abundant element in the earth's crust, is not only a cheaper alternative to lanthanide salts, but also, due to its high biocompatibility, it is a less toxic alternative to lanthanides.Hence, the use of calcium complexes to catalyze a broad range of applications in organic synthesis has increased tremendously over the past two decades.[ii]The Luche reduction, for instance, is one of the standard protocols to regioselectively reduce a,�-unsaturated carbonyls (1) to allylic alcohols (2).[iii] The use of cerium(III) chloride as a stoichiometric additive however, is not desirable on an industrial scale. Successful reaction conditions for a calcium-mediated regioselective 1,2-reduction of challenging enones, such as 2-cyclopententone, to the corresponding allylic alcohol in 92:8 selectivity (allylic alcohol:saturated alcohol) have been developed. Preliminary studies have shown that the stereoselective reduction of a,�-aziridinyl ketone (3) to the alcohol (4) in the presence of calcium triflate gave excellent diastereoselectivity. Furthermore, preliminary investigations into the reaction pathway of the 1,2-reduction of 2-cyclopentenone, through kinetic modelling are underway. <i> Datta, S.; Roesky, P. W.; Blechert, S. Organometallics 2007  , 26, 4392-4394.[ii] Harder, S. Chem. Rev. 2010  , 110, 3852-3876.[iii] Gemal, A. L.; Luche, J.-L. J. Am. Chem. Soc. 1981  , 103, 5454-5459.

Lanthanide replacement in organic chemistry: Calcium-mediated selective Luche reduction

244th National Meeting (2012)

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