Scope and Mechanism of the Pt-Catalyzed Enantioselective Diboration of Monosubstituted Alkenes
作者:John R. Coombs、Fredrik Haeffner、Laura T. Kliman、James P. Morken
DOI:10.1021/ja4041016
日期:2013.7.31
The Pt-catalyzed enantioselective diboration of terminal alkenes can be accomplished in an enantioselective fashion in the presence of chiral phosphonite ligands. Optimal procedures and the substrate scope of this transformation are fully investigated. Reaction progress kinetic analysis and kinetic isotope effects suggest that the stereodefining step in the catalytic cycle is olefin migratory insertion
ZrCl<sub>4</sub> as an Efficient Catalyst for a Novel One-Pot Protection/Deprotection Synthetic Methodology
作者:Surendra Singh、Colm D. Duffy、Syed Tasadaque A. Shah、Patrick J. Guiry
DOI:10.1021/jo800932t
日期:2008.8.1
found to be an efficientcatalyst for the one-pot esterification and deprotection of (5S,6R)-5,6-diacetoxyoct-7-enoic acid in good yields (44−62%) with a lactone formed as a minor byproduct. ZrCl4 (10−20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl4 (1−10 mol %) also promoted diol protection as the acetonide
Analytical enantiomer separation of aliphatic diols as boronates and acetals by complexation gas chromatography
作者:V. Schurig、D. Wistuba
DOI:10.1016/s0040-4039(01)91399-1
日期:1984.1
Cyclic boronates and acetals of mono- and dialkylsubstituted 1,2-, 2,3- 1,3- & 1,4- diols have been quantitatively separated into enantiomers by complexationgaschromatography utilizing optically active metal chelates. An efficient, precise & sensitive method for determining enantiomeric purities for volatile glycols is thus available.
Cu(OTf)<sub>2</sub>-Catalyzed Selective Opening of Aryl and Vinyl Epoxides with Carbonyl Compounds to Give 1,3-Dioxolanes
作者:Pavel Krasik、Mathieu Bohemier-Bernard、Qing Yu
DOI:10.1055/s-2005-864795
日期:——
Copper(II) triflate catalyzes the ring-opening of aryl- and vinyl-substituted epoxides with various carbonyl compounds to furnish 1,3-dioxolanes under mild conditions. Alkyl- and alkoxycarbonyl-substituted epoxides remainunchanged under reaction conditions. This allows selective opening of aryl-substituted epoxides in the presence of alkyl-substituted ones.
In the presence of a catalytic amount of titanium(IV) chloride, opticallyactivestyreneoxide and its analogs are directly converted into the corresponding acetals such as acetonides or cyclopentylidene acetals keeping up high to complete optical purity on the treatment with ketones.