Cyclopentene epoxide

Andersson et al. further improved their diamine catalyst 62 by introduction of substituents on the pyrrolidine ring [63], Of various catalysts tested, the dimethy-lated compound 63 proved best (Scheme 13.32) [63], As summarized in Scheme 13.32, excellent enantiomeric excesses were achieved by use of catalyst loadings as low as 5 mol%, and even for notoriously difficult substrates such as cyclopentene epoxide. 

Prepared by addition of 4-pentenyl magnesium bromide to cyclopentanone, dehydration of the alcohol to l-(4-pentenyl)cyclopentene, epoxidation of the endocyclic double bond, and periodate epoxide cleavage.53... 

Chloro-1,2-epoxypropane (chloropropene oxide, 2-chloro-3-methyloxirane) [21947-75-1] c A-isomer [21947-76-2] frawi-isomer Cyclopentene oxide (6-oxabicyclo-[3.1.0] hexane, cyclopentane oxide, cyclopentene epoxide, 1,2-epoxycyclopentane) [285-67-6]... 

As noted in Section 2.2, when an epoxycyclopentenone 7 was formed thermally, it largely isomerized into the isomeric pyranone 8 (Scheme 3 2000 TL9189). This is a general process and FVP of the benzo-, naphtho-, and benzofuro-cyclopentene epoxides 347, 349, and 351 leads to the isocou-marins 348, and analogs 350 and 352, the last of which is related to the natural product coriandrin (Scheme 68 2000TL3677). 

Epoxides, like other ethers, are cleaved by nucleophiles under acidic conditions. For example, cyclopentene oxide produces a mixture of 1,2-cyclopentanediol stereoisomers when treated with water and sulfuric acid. 

The product of nucleophilic attack can be anticipated by examining the lowest-unoccupied molecular orbital (LUMO) on protonated cyclopentene oxide. From which direction (top or bottom) would a nucleophile be more likely to approach each epoxide carbon in order to transfer electrons into this orbital Explain. Does one carbon contribute more to the LUMO, or is the orbital evenly spread out over both epoxide carbons Assuming that LUMO shape dictates product stereochemistry, predict which stereoisomers will be obtained, and their approximate relative amounts. Is the anticipated kinetic product also the thermodynamic product (Compare energies of 1,2-cyclopentanediol stereoisomers to tell.)... 

The results of the olefin oxidation catalyzed by 19, 57, and 59-62 are summarized in Tables VI-VIII. Table VI shows that linear terminal olefins are selectively oxidized to 2-ketones, whereas cyclic olefins (cyclohexene and norbomene) are selectively oxidized to epoxides. Cyclopentene shows exceptional behavior, it is oxidized exclusively to cyclopentanone without any production of epoxypentane. This exception would be brought about by the more restrained and planar pen-tene ring, compared with other larger cyclic nonplanar olefins in Table VI, but the exact reason is not yet known. Linear inner olefin, 2-octene, is oxidized to both 2- and 3-octanones. 2-Methyl-2-butene is oxidized to 3-methyl-2-butanone, while ethyl vinyl ether is oxidized to acetaldehyde and ethyl alcohol. These products were identified by NMR, but could not be quantitatively determined because of the existence of overlapping small peaks in the GC chart. The last reaction corresponds to oxidative hydrolysis of ethyl vinyl ether. Those olefins having bulky (a-methylstyrene, j8-methylstyrene, and allylbenzene) or electon-withdrawing substituents (1-bromo-l-propene, 1-chloro-l-pro-pene, fumalonitrile, acrylonitrile, and methylacrylate) are not oxidized. 

A variety of ie.so-epoxidcs could be selectively ring-opened this way with e.e. s as high as 97% [28], The azides can be converted to 1,2-amino alcohols, which are very desirable synthetic intermediates. Surprisingly, the mechanism of the ARO (asymmetric ring-opening) was more complicated than expected [29], First, it turned out that the chloride ion in Cr-salen was replaced by azide. Secondly, water was needed and HN3 rather than Me3SiN3 was the reactant nucleophile. Thirdly, the reaction rate was found to be second order in catalyst concentration, minus one in epoxide (cyclopentene oxide), and zero order in HN3 [30],... 

The kinetics of the catalytic oxidation of cyclopentene to glutaraldehyde by aqueous hydrogen peroxide and tungstic acid have been studied and a compatible mechanism was proposed, which proceeds via cyclopentene oxide and /3-hydroxycyclopentenyl hydroperoxide. " Monosubstituted heteropolytungstate-catalysed oxidation of alkenes by t-butyl hydroperoxide, iodosobenzene, and dioxygen have been studied a radical mechanism was proved for the reaction of alkenes with t-BuOOH and O2, but alkene epoxidation by iodosobenzene proceeds via oxidant coordination to the catalyst and has a heterolytic mechanism. ... 

Long-chain derivatives of pyrazolyl pyridines coordinated to MoO(02)2 as 35 may efficiently replace the conventional Mo(CO)e in the oxidation of several double-bond typologies with TBHP, in non-polar hydrocarbon solvents . The epoxidation of cyclopentene and 2,3-dimethyl-2-butene led to the corresponding epoxides, notoriously sensitive to ring opening, in 100% and 87% yield respectively, in isoctane, with 1 hour reaction time. Recent advances in the epoxidation of a-pinene and other terpenes using the Mo-TBHP system have been reported. ... 

Illustrative of the behavior of afioyclio epoxides toward attack by hydrogen sulfide are reactions of cyclopenten oxide. and cyclo-hexene oxide.391 U B Passage of hydrogen sulfide through alkaline solutions of these substances (Eq. 641) causes first the formation of... 

Various alioyolio epoxides have been subjected to the action oJ oarbanionoid reagents. Cyclopentene oxide (Eq. 887) is unique thus far, in that it gives no lactone.870 Lactone formation is prevented b the high activation energy required to establish irwwt-fusion between two five-membered rings.870... 

Cyclopentene oxide is reported to react smoothly with methyl lithium,but higher alkyl Lithiums have not been examined with thia epoxide until now. Methyllithium likewise condenses readily with. 1,3,3-trichloro-1,2-epoxypropane487 to give the corresponding terminal addition product (Eq. 803). 

This subject has recently been reviewed.647 Several additional papers have appeared on the catalytic oxidation of alkenes by 02 in the presence of PdCl(MeCN)2N02(148).64S Terminal alkenes and trans- cyclooctene yield the corresponding ketones, cyclopentene and cyclohexene the corresponding allyl alcohol, and bicyclic alkenes the corresponding epoxide. Heterometallacy-clopentanes such as (152) have been isolated from the reaction of (148) with norbornene (dicy-clopentadiene), and characterized by X-ray crystallography.6486 Glycol monoacetates were obtained from the reaction of (148) with terminal alkenes in acetic acid.649... 

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