Aldehydes oxidative homo-coupling

Multi-component reactions open a direct access to poly-functional derivatives/ For instance, reactions of unsaturated substrates and aldehydes in the presence of EtaSiH opened a rapid access to allyllic, homo-allylic or co-unsatu-rated alcohols, and NHC-Ni complexes were recently reported to be efficient catalysts for such oxidative coupling. Mori and co-workers described the first example of such condensation in 2001. They showed that an in situ generated IPr/Ni 1 1 complex led to the stereoselective formation of (Z)-homoal-lylic silyl alcohols [eqn (10.33)], while classical Ni -PPhj catalyst produced only (Ej-coupling products. Of note, IPr/Ni 1 2 and IMes/Ni 1 2 were less efficient in this reaction. These first results were extended to silylated dienes. Interestingly, it was shown that a mixed complex [(IPr)Ni(PPh3)] stereoselectively produced (Z)-allylsilanes while [Ni(PPh3)4] led only to (Ej-isomeric products. 

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