Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with C≡C bonds to generate bicyclicketals is presented. This reaction essentially involves the formation of an acetonide, which subsequently cyclises on the alkyne intramolecularly under gold catalysis conditions. This method could be extended to make optically pure bicyclicketals. Deuterium incorporation
Convenient Method for Epoxidation of Alkenes Using Aqueous Hydrogen Peroxide
作者:Man Kin Tse、Markus Klawonn、Santosh Bhor、Christian Döbler、Gopinathan Anilkumar、Herbert Hugl、Wolfgang Mägerlein、Matthias Beller
DOI:10.1021/ol047604i
日期:2005.3.1
[reaction: see text] The complex [Ru(tpy)(pydic)] (1a) is an active catalyst for epoxidation of alkenes by aqueous 30% hydrogenperoxide in tertiary alcohols. The protocol is simple to operate and gives the corresponding epoxides in good to excellent yields. Chiral enantiopure [Ru(tpy)(pydic)] complexes have been synthesized and successfully applied in this procedure.
Arabinose-Derived Ketones as Catalysts for Asymmetric Epoxidation of Alkenes
作者:Tony K. M. Shing、Gulice Y. C. Leung、To Luk
DOI:10.1021/jo050928f
日期:2005.9.1
Readily available arabinose-derived ketones, containing a tunable butane-2,3-diacetal as the steric blocker, displayed increasing enantioselectivity (up to 90% ee) with the size of the acetal alkyl group in catalytic asymmetricepoxidation of trans-disubstituted and trisubstituted alkenes. The stereochemical communication between our ketonecatalysts and the alkene substrates is mainly due to steric
The opening reaction of epoxides by monochloroborane-dimethylsulfide 1 proceeds by oxygen anchimeric assistance in a regio and diastereoselective manner to give the corresponding anti chlorohydrins.
Efficient Epoxidation of Alkenes with Aqueous Hydrogen Peroxide Catalyzed by Methyltrioxorhenium and 3-Cyanopyridine
作者:Hans Adolfsson、Christophe Copéret、Jay P. Chiang、Andrei K. Yudin
DOI:10.1021/jo005623+
日期:2000.12.1
The epoxidation of alkenes with 30% aqueous hydrogen peroxide is catalyzed efficiently by methyltrioxorhenium (MTO) in the presence of pyridine additives. The addition of 1-10 mol % of 3-cyanopyridine increases the system's efficiency for terminal and trans-disubstituted alkenes resulting in high isolated yields of the corresponding epoxides. The system allows for epoxidation of alkenes with various