Alkenes as Ketol Surrogates−A New Approach toward Enantiopure Acyloins
作者:Bernd Plietker
DOI:10.1021/ol0362663
日期:2004.1.1
paper describes the use of cyclic ruthenates for the first catalytic regioselective oxidation of vic-diols to alpha-ketols. The combination of RuCl3/Oxone/NaHCO3 was used in a two-step sequence of asymmetric dihydroxylation and regioselective monooxidation for the synthesis of a broad scope of enantiopure acyloins.
Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes
作者:Lichao Fang、Lu Yan、Fredrik Haeffner、James P. Morken
DOI:10.1021/jacs.5b13174
日期:2016.3.2
Catalytic enantioselective diboration of alkenes is accomplished with readily available carbohydrate-derived catalysts. Mechanistic experiments suggest the intermediacy of 1,2-bonded diboronates.
A New Practical Method for the Osmium-Catalyzed Dihydroxylation of Olefins using Bleach as the Terminal Oxidant
作者:Matthias Beller、Gerald M. Mehltretter、Santosh Bhor、Markus Klawonn、Christian Döbler、Uta Sundermeier、Markus Eckert、Hans-Christian Militzer
DOI:10.1055/s-2003-36826
日期:——
A general procedure for the osmium-catalyzed dihydroxylation of various olefinsusing bleach as oxidant is reported for the first time. Aromatic and aliphatic olefins yield the corresponding cis-1,2-diols in the presence of dihydroquinine or dihydroquinidine derivatives (Sharpless ligands) with good to excellent chemo- and enantioselectivities under optimized pH conditions. In the presence of a small
Osmium-Catalyzed Asymmetric Dihydroxylation of Olefins by H<sub>2</sub>O<sub>2</sub>; Dual Role of the Cinchona Alkaloid Ligand
作者:Sandra Y. Jonsson、Hans Adolfsson、Jan-E. Bäckvall
DOI:10.1021/ol016450t
日期:2001.11.1
[reaction: see text]. A novel application of the cinchona alkaloid derivative (DHQD)2PHAL in the osmium-catalyzed asymmetricdihydroxylation of olefins is presented. In a triple catalytic system using H2O2 as the terminal oxidant, the alkaloid ligand has a dual function in providing stereocontrol in the addition step and, via its N-oxidized form, acting as reoxidant for the in situ generated osmium(VI)
alkaloid derivative, which can be recovered and reused in the same way as the reported soluble polymer-supported cinchona alkaloid-derived ligands, was applied to the homogeneous asymmetricdihydroxylation of olefins. The molar ratio of ligand/olefin was 5%, being much lower than that required for the corresponding soluble polymer-supported ligands (10–25%). Yields of 82–93% and ees of 89–99% have been obtained