Mechanism of asymmetric hydrogenation of enamides with [Rh(BisP*)]+ catalyst: Model DFT study

Abstract

AbstractThe potential energy profile for the [Rh(R,R)‐Et‐BisP*]+‐catalyzed asymmetric hydrogenation of prochiral enamides, α‐acetamidoacrylonitrile, was studied by the nonlocal density functional method (B3LYP). As illustrated, this hydrogenation is exothermic and goes mainly through association of [Rh(R,R)‐Et‐BisP*]+ with α‐acetamidoacrylonitrile, oxidative addition of hydrogen, migratory insertion of an olefin carbon into a RhH bond, reductive elimination of the CH bond from the alkyl hydride, and dissociation of product–catalyst adducts with regeneration of the catalyst. The turnover‐limiting step for this reaction is the oxidative addition of hydrogen. The main product predicted theoretically is the R‐conformer. Our results are consistent with available empirical data and experiments for rhodium‐catalyzed asymmetric hydrogenation. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005