Metallo phosphonate catalyzed benzoin couplings: the influence of the counterion

Abstract

The phosphonate catalyzed umpolung of benzoylsilane with a glycol based phosphonate is computationally investigated using the catalyst metal free and with the counterions Li⁺, Na⁺ and K⁺. For all studied systems, the transition structures of the umpolung step exhibit the highest energies of the overall process. With lithium as a counterion, this transition structure is most stabilized. Addition steps of the catalysts to benzoylsilane and of the umpoled C-nucleophile (d¹-species) to benzaldehyde are also favoured for counterions, which act as Lewis acids, especially lithium.