Alkenes and allyl alcohols

High ees have been obtained for several different catalytic systems for an extended range of substrates. 

Lightfoot et have developed one of these iridium-based systems for the 

Good methods for the chiral reduction of tetrasubstituted and terminal alkenes have yet to be fully developed. 

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The oxidation of alkenes and allylic alcohols with the urea-EL202 adduct (UELP) as oxidant and methyltrioxorhenium (MTO) dissolved in [EMIM][BF4] as catalyst was described by Abu-Omar et al. [61]. Both MTO and UHP dissolved completely in the ionic liquid. Conversions were found to depend on the reactivity of the olefin and the solubility of the olefinic substrate in the reactive layer. In general, the reaction rates of the epoxidation reaction were found to be comparable to those obtained in classical solvents. 

Hexafluoroacetone and hydrogen peroxide in buffered aqueous solution can epoxidize alkenes and allylic alcohols.101 N, Af-Dialkylpiperidin-4-one salts are also good catalysts for epoxidation.102 The polar effect of the quaternary nitrogen enhances the... 

Based on these calculations, one can conclude that TSs for epoxidation of alkenes and allylic alcohols with peroxy acids, dioxiranes, and Re-peroxo complexes share a spiro geometry in which the plane of the attacking peroxo... 

The peroxotungstate [W203(02)4(H20)2], immobilized on dihydroimidazolium-based ionic liquid-modifed Si02 has been employed for alkene and allylic alcohol epoxidation... 

The hydroxymercuration-demercuration of conjugated dienes generally does not afford monohydration products selectivity, but diols can sometimes be obtained in reasonable yield. The direction of addition of H—OH is that expected by extrapolation from simple alkenes and allylic alcohols. 

Methodology has been found that allows for the asymmetric oxidation of alkenes and allyl alcohol to the corresponding epoxides or diols. The HKR method is beginning to be used to access chiral epoxides. Although asymmetric oxidations are now being used at scale, they are not used nearly as often as asymmetric reductions. 

This process occurs for X = O only in two special cases, which have been developed into synthetic methods for alkenes and allylic alcohols. Reaction of BusSnH with 1,2-bis-MDC derivatives gave al-kenes from diols in a process which was independent of the geometry of the starting diol. Examples are the conversions of (84) to (85) and of (86) to (87). 

On the down side, catalyst activity of W-based systems is often only high enough to meet technoeconomic demands in case of reactive alkenes, such as electron-rich alkenes and allylic alcohols. 

Schiff s base complexes of vanadium were encapsulated in the supercages of zeolite NaY and their catalytic activities were tested in the epoxidation of several alkenes and allylic alcohols with /er/-butylhydroperoxide The complexes investigated were VO(HPS) (vanadyl-N-(2-hydroxyphenyl)salicylideneimine) and VO(salen) (vanadyl-N,N (bis)salicylidene-imine). Particular attention was devoted to the question of leaching of vanadium during reaction. 

Rearrangement-coupling. This effective synthetic process involving an alkene and allylic alcohol in juxtaposition is applicable to the synthesis of (+)-equilenin. Solvent determines the diastereoselectivity. 

These two reactions were elegantly combined in the deoxydehydration of diols and polyols to alkenes and allylic alcohols catalyzed by ReCp Os/PPhs, which provides a useful means of reducing oxygen-rich organics like carbohydrates. ... 

Asymmetric Epoxidation.—[V(0)(0R)20gBu ] is reported to be the active catalyst in the asymmetric epoxidation of /ra j-oct-2-ene by t-butyl hydroperoxide in the presence of menthol, ROH, and [Y(OXacac)2]. t-Butyl hydroperoxide also effects asymmetric epoxidation of alkenes and allyl alcohols in the presence of (56) and bis[(+)-3-trifluoroacetylcamphoratol]oxovanadium, respectively, Other studies in this area are summarized in Table 4. 

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