Diastereoselective Epoxidation of Cyclohexene Derivatives by Dioxiranes Generated in Situ. Importance of Steric and Field Effects
作者:Dan Yang、Guan-Sheng Jiao、Yiu-Chung Yip、Man-Kin Wong
DOI:10.1021/jo9821978
日期:1999.3.1
In this paper, diastereoselective epoxidation of substituted cyclohexenes (substrates 1-7) by dioxiranes generated in situ from ketones and Oxone was systematically investigated. The results revealed that the diastereoselectivity was determined by the steric and field effects of both dioxiranes and substrates, and high diastereoselectivity can be achieved by tuning the ketone structure. Among the ketones
Epoxidation of Olefins with a Silica-Supported Peracid
作者:Rossella Mello、Ana Alcalde-Aragonés、María Elena González Núñez、Gregorio Asensio
DOI:10.1021/jo300533b
日期:2012.8.3
Anhydrous [2-percarboxyethyl] functionalized silica (2a) is an advantageous oxidant for performing the epoxidation of olefins 1. Epoxides 3 do not undergo the ring-opening reactions catalyzed by the acidic silica surface, except for particularly activated cases such as styrene oxide. The hydrophilic and acidic character of the silica surface does not interfere with the directing effects exerted by
Epoxidation of Olefins with a Silica-Supported Peracid in Supercritical Carbon Dioxide under Flow Conditions
作者:Rossella Mello、Ana Alcalde-Aragonés、Andrea Olmos、María Elena González-Núñez、Gregorio Asensio
DOI:10.1021/jo300532f
日期:2012.5.18
2-percarboxyethyl-functionalized silica (2b), a recyclable supported peracid, is a suitable reagent to perform the epoxidation of alkenes 1 in supercriticalcarbondioxide at 250 bar and 40 °C underflowconditions. This procedure simplifies the isolation of the reaction products and uses only carbondioxide as a solvent under mild conditions. The solid reagent 2b can be easily recycled by a reaction with
Highly Diastereoselective Epoxidation of Allyl-Substituted Cycloalkenes Catalyzed by Metalloporphyrins
作者:Wing-Kei Chan、Peng Liu、Wing-Yiu Yu、Man-Kin Wong、Chi-Ming Che
DOI:10.1021/ol0496475
日期:2004.5.1
Highly diastereoselectiveepoxidations of allyl-substituted cycloalkenes including allylic alcohols, esters, and amines using sterically bulky metalloporphyrins [Mn(TDCPP)Cl] (1) and [Ru(TDCPP)CO] (2) as catalysts have been achieved. The "1 + H(2)O(2)" and "2 + 2,6-Cl(2)pyNO" protocols afforded trans-epoxides selectively in good yields (up to 99%) with up to >99:1 trans-selectivity.