Search results
Results From The WOW.Com Content Network
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 2001 he was awarded a half-share of the Nobel Prize in Chemistry for his work on chirally catalyzed oxidation reactions (Sharpless epoxidation, Sharpless asymmetric dihydroxylation, Sharpless oxyamination). The other half of the year's Prize was shared between William S. Knowles and Ryōji Noyori (for their work on stereoselective ...
In the Sharpless dihydroxylation reaction the chirality of the product can be controlled by the "AD-mix" used. This is an example of enantioselective synthesis using asymmetric induction Key: R L = Largest substituent; R M = Medium-sized substituent; R S = Smallest substituent Two enantiomers of a generic alpha amino acid
The two letters AD, stand for asymmetric dihydroxylation. The mix is available in two variations, "AD-mix α" and "AD-mix β" following ingredient lists published by Barry Sharpless. [1] The mixes contain: Potassium osmate K 2 OsO 2 (OH) 4 as the source of Osmium tetroxide; Potassium ferricyanide K 3 Fe(CN) 6, which is the re-oxidant in the ...
N-Methylmorpholine N-oxide (more correctly 4-methylmorpholine 4-oxide), NMO or NMMO is an organic compound.This heterocyclic amine oxide and morpholine derivative is used in organic chemistry as a co-oxidant and sacrificial catalyst in oxidation reactions for instance in osmium tetroxide oxidations and the Sharpless asymmetric dihydroxylation or oxidations with TPAP. [1]
The Upjohn dihydroxylation is an organic reaction which converts an alkene to a cis vicinal diol. It was developed by V. VanRheenen, R. C. Kelly and D. Y. Cha of the Upjohn Company in 1976. [ 1 ] It is a catalytic system using N -methylmorpholine N -oxide (NMO) as stoichiometric re-oxidant for the osmium tetroxide .
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]