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CH Activation Reactions of Ruthenium N-Heterocyclic Carbene Complexes:  Application in a Catalytic Tandem Reaction Involving CC Bond Formation from Alcohols

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posted on 21.02.2007, 00:00 by Suzanne Burling, Belinda M. Paine, Devendrababu Nama, Victoria S. Brown, Mary F. Mahon, Timothy J. Prior, Paul S. Pregosin, Michael K. Whittlesey, Jonathan M. J. Williams
A series of ruthenium hydride N-alkyl heterocyclic carbene complexes has been investigated as catalysts for a tandem oxidation/Wittig/reduction reaction to give CC bonds from alcohols. The CH-activated carbene complex Ru(IiPr2Me2)‘(PPh3)2(CO)H (9) proves to be the most active precursor catalyzing the reaction of PhCH2OH and Ph3PCHCN in 3 h at 70 °C. These results provide (a) a rare case in which N-alkyl carbenes afford higher catalytic activity than their N-aryl counterparts and (b) a novel example of the importance of NHC CH activation in a catalytic cycle.