Hydrogen: a good partner for rhodium-catalyzed hydrosilylation

The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)‐SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH2Cl2, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under hydrogen pressure. Copyright © 2014 John Wiley & Sons, Ltd. We have shown that the performances of a rhodium complex associated with the atropisomeric diphosphine SYNPHOS® as chiral ligand can be considerably upgraded under hydrogen pressure. Most serendipitously, several ketones were found to give the products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under H2 pressure.