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Highly Enantioselective and Regioselective Nickel-Catalyzed Coupling of Allenes, Aldehydes, and Silanes

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journal contribution
posted on 25.05.2005, 00:00 by Sze-Sze Ng, Timothy F. Jamison
A complex derived from Ni(cod)2 and NHC−IPr catalyzes a three-component coupling reaction involving allenes, aldehydes, and organosilanes and transfers the axial chirality of the allene to a stereogenic center in the product with very high fidelity. An unexpected regioselectivity is observed; favored are allylic rather than homoallylic alcohol derivatives, corresponding to the unusual process of coupling two electrophilic atoms:  the allene sp and aldehyde carbon atoms. In all cases, high enantioselectivity, high Z/E selectivity, and, with differentially substituted allenes, high site selectivity are observed. This transformation represents the first enantioselective multicomponent coupling process of allenes.