نتایج جستجو برای: phosphines
تعداد نتایج: 579 فیلتر نتایج به سال:
This review surveys the literature regarding the development of catalytic versions of the Wittig and aza-Wittig reactions. The first section summarizes how arsenic and tellurium-based catalytic Wittig-type reaction systems were developed first due to the relatively easy reduction of the oxides involved. This is followed by a presentation of the current state of the art regarding phosphine-catal...
The bacterial phosphotriesterase has been shown to catalyze the stereoselective hydrolysis of phosphinate esters. The wild-type enzyme preferentially hydrolyzes the SP-enantiomers of methyl phenyl p-X-phenylphosphinate esters by 3 orders of magnitude. The mutant enzyme, I106T/F132A/H254G/H257W, exhibits the opposite stereoselectivity and hydrolyzes the RP-enantiomer up to 30 times faster than t...
Bidentate phosphine ligands have been prepared on polystyrene beads modified with polyether dendron spacers. When complexed to Pd(0), these systems exhibited a negative dendritic effect on Heck catalysis (contrary to the analogous monodentate phosphine systems), but mostly a positive influence on carbonylation. This opposite influence of the dendronization falls into line with other differences...
Transition-metal (TM) complexes of new phosphines, readily prepared by a straight forward three-step modular synthesis, were successfully employed in difficult crosscoupling reactions conducted under mild conditions (water, “open-flask”, low temperature) that aspire to meet green chemistry criteria. High yielding catalyzed by bismuth or rhodium complexes oxidative arylation of naphthoquinone ga...
The catalytic asymmetric methylation of fluoroalkylated pyruvates is shown with dimethylzinc as a methylating reagent in the presence of a copper catalyst bearing a chiral phosphine ligand. This is the first catalytic asymmetric methylation to synthesize various α-fluoroalkylated tertiary alcohols with CF3, CF2H, CF2Br, and n-C n F2n+1 (n = 2, 3, 8) groups in good-to-high yields and enantiosele...
A method for the preparation of chiral β-aminophosphines having substituted P-aryl groups is described. Ring-opening of cyclic sulfamidates with metal diarylphosphinites yields β-aminophosphine oxides, which are then reduced to the corresponding phosphines. Effects of the diarylphosphinite countercation on the regioselectivity of the ring-opening reaction (P- versus O-alkylation) are discussed....
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