Olefination with phosphorus ylides. I. Mechanism and stereochemistry of the Wittig reaction
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Using 13C-chem. shifts as a probe for the electronic environment of carbon centers, triphenylphosphoniomethanide, the model case of a reactive phosphorus ylide, have much more zwitterion than PC double bond character. Triphenylphosphoniopropenide (tripheny ...
Olefins of the formula R1XC:CR2R3 were prepd. by removal of a proton from a betaine-like intermediate, (Ph)3P+-CHR1CR2R3O-, and subsequent treatment with the desired X+. Thus, 1 mole PhLi and the phosphonium salt, (Ph)3PCH2R1.HCl, in 3 parts Et2O and 1 par ...
A review, with 6 refs., of the prepn. of olefins from phosphonium ylides and carbonyl compds. and from phosphonium ylides, carbonyl compds., org. Li compds., and reactive halogen compds., such as MeCOCH2Cl and EtI. [on SciFinder (R)] ...
Alkylidenetriphenylphosphoranes (I) tend in general towards cis olefination. The proportion of cis olefin in the isomer mixt. is highest when the ylide used is salt-free. Li salts favor the formation of the trans isomers. Salt-free I and BzH in 4:1 C6H6-pe ...
Mechanistic investigations into homogeneously catalyzed reactions are essential for the fur-ther development of synthetic methodologies. Insights in the overall reaction pathway and vital steps such as the rate-determining and selectivity-determining steps ...
Grafting of [W( NAr)(=CHtBu)(2,5-Me2NC4H2)(2)] on a silica partially clehydroxylated at 700 degrees C (SiO2-(700)) generates the corresponding monosiloxy complex [( SiO)W( NAr)(=CHtBu)(2,5-Me2NC4H2)] as the major species (approximate to 90%) along with [( ...
