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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 Sharpless asymmetric dihydroxylation [7] was developed by K. Barry Sharpless to use catalytic amounts of OsO 4 along with the stoichiometric oxidant K 3 [Fe(CN) 6]. [1] [2] [8] The reaction is performed in the presence of a chiral auxiliary. The selection of dihydroquinidine (DHQD) or dihydroquinine (DHQ) as a chiral auxiliary dictates the ...
In 1992, K.B. Sharpless showed that the asymmetric dihydroxylation conditions developed in his group could be harnessed to give either (R)- or (S)- α-hydroxy ketones from the corresponding silyl enol ethers depending on which Chinchona alkaloid-derived chiral ligands were employed. [22]
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 ...
Sharpless asymmetric dihydroxylation; Sharpless epoxidation [34] Sharpless oxyamination or aminohydroxylation; Shenck ene reaction; Shi epoxidation; Shiina esterification; Shiina macrolactonization or Shiina lactonization; Sigmatropic reaction; Simmons–Smith reaction; Simonini reaction; Simonis chromone cyclization; Simons process; Skraup ...
The Sharpless oxyamination (often known as Sharpless aminohydroxylation) is the chemical reaction that converts an alkene to a vicinal amino alcohol. The reaction is related to the Sharpless dihydroxylation , which converts alkenes to vicinal diols. [ 1 ]
Sharpless asymmetric dihydroxylation has also seen use as a method for kinetic resolution. [18] [19] This method is not widely used, however, since the same resolution can be accomplished in different manners that are more economical. Additionally, the Shi epoxidation has been shown to affect kinetic resolution of a limited selection of olefins ...
Asymmetric epoxidation is often feasible. [4] One named reaction is the Jacobsen epoxidation, which uses manganese-salen complex as a chiral catalyst and NaOCl as the oxidant. The Sharpless epoxidation using chiral N-heterocyclic ligands and osmium tetroxide. Instead of asymmetric epoxidation, alkenes are susceptible to asymmetric dihydroxylation.