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Alkenes that are particularly amenable to asymmetric hydrogenation often feature a polar functional group adjacent to the site to be hydrogenated. In the absence of this functional group, catalysis often results in low ee's. For some unfunctionalized olefins, iridium with P,N-based ligands) have proven effective, however. Alkene substrates are ...
K. Barry Sharpless was the first to develop a general, reliable enantioselective alkene dihydroxylation, referred to as the Sharpless asymmetric dihydroxylation (SAD). Low levels of OsO 4 are combined with a stoichiometric ferricyanide oxidant in the presence of chiral nitrogenous ligands to create an asymmetric environment around the oxidant.
The rule states that with the addition of a protic acid HX or other polar reagent to an asymmetric alkene, the acid hydrogen (H) or electropositive part gets attached to the carbon with more hydrogen substituents, and the halide (X) group or electronegative part gets attached to the carbon with more alkyl substituents. This is in contrast to ...
Enantioselective synthesis, also called asymmetric synthesis, [1] is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric ( enantiomeric or diastereomeric ) products in unequal ...
Wilkinson's catalyst is best known for catalyzing the hydrogenation of olefins with molecular hydrogen. [ 11 ] [ 12 ] The mechanism of this reaction involves the initial dissociation of one or two triphenylphosphine ligands to give 14- or 12-electron complexes, respectively, followed by oxidative addition of H 2 to the metal.
Dynamic kinetic resolution of 1,4 conjugate reduction. The rate-limiting step is the copper complex interaction with the double bond and the transfer of hydrogen. 1,4 conjugate reduction to cyclic enones. Copper proved to be an excellent metal in this reaction due to its ability to complex with the oxygen when the hydrogen was added.
The Juliá–Colonna epoxidation is an asymmetric poly-leucine catalyzed nucleophilic epoxidation of electron deficient olefins in a triphasic system.The reaction was reported by Sebastian Juliá at the Chemical Institute of Sarriá in 1980, [1] with further elaboration by both Juliá and Stefano Colonna (Istituto di Chimica Industriale dell'Università, Milan, Italy).
The Heck reaction (also called the Mizoroki–Heck reaction) [1] is the chemical reaction of an unsaturated halide (or triflate) with an alkene in the presence of a base and a palladium catalyst to form a substituted alkene. It is named after Tsutomu Mizoroki and Richard F. Heck.