98170-69-5Relevant academic research and scientific papers
Development of ruthenium catalysts for the enantioselective synthesis ofP-stereogenic phosphines via nucleophilic phosphido intermediates
Chan, Vincent S.,Chiu, Melanie,Bergman, Robert G.,Toste, F. Dean
supporting information; experimental part, p. 6021 - 6032 (2009/09/24)
This work details the development of ruthenium(ll) catalysts for the enantioselective alkylation of chiral racemic secondary phosphines. The reactions proceed through the intermediacy of nucleophilic phosphido species, which have low barriers to pyramidal inversion; this allows for a dynamic kinetic asymmetric alkylation. The initially discovered [((R)-/Pr-PHOX) 2Ru(H)][BPh 4] (6) catalyst was found to be effective in the reaction with benzylic chlorides; moreover, the alkylation displayed an unusual temperature dependence. However, the limited scope of alkylation of 6 motivated further studies which led to the development of two complementary chiral mixed ligand Ru(ll) catalysts of type [L 1L 2Ru(H)] +. These catalysts were derived from a combination of one chiral and one achiral ligand, where a synergistic interaction of the two ligands creates an effective asymmetric environment around the ruthenium center. The (R)-MeO-BiPHEP/dmpe (dmpe= 1,2-bis(dimethylphosphino)ethane) catalyst (10) was found to be effec tive for the asymmetric alkylation of benzylic chlorides, while the (R)-DIFLUORPHOS/dmpe catalyst (11) was optimal for the nucleophilic substitution of less activated alkyl bromides; the scope of the respective catalysts was also explored.
