Cyclohexene oxides hydrolysis

An alternative method for generating enriched 1,2-diols from meso-epoxides consists of asymmetric copolymerization with carbon dioxide. Nozaki demonstrated that a zinc complex formed in situ from diethylzinc and diphenylprolinol catalyzed the copolymerization with cyclohexene oxide in high yield. Alkaline hydrolysis of the isotactic polymer then liberated the trans diol in 94% yield and 70% ee (Scheme 7.20) [40]. Coates later found that other zinc complexes such as 12 are also effective in forming isotactic polymers [41-42]. 

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. 

G. Bellucci, C. Chiappe, F. Marioni, Enantioselectivity of the Enzymatic Hydrolysis of Cyclohexene Oxide and ( )-l-Methylcyclohexene Oxide A Comparison between Microsomal and Cytosolic Epoxide Hydrolases , J. Chem. Soc., Perkin Trans. 1 1989, 2369 -2373. 

Monosilylation of anilines. The usual method of silylation of anilines, BuLi, ClSi(CH3)3, is inconvenient on a large scale and not widely applicable because of ready hydrolysis of some silylanilines. A new method involves reaction of the aniline with HN[Si(CH3)3]2 (3 equiv.) and catalytic amounts of ClSi(CH3)3 and Lil. After 95% silylation, the ISi(CH3)3 is quenched with cyclohexene oxide and the product isolated by distillation. Yields are 80-97%. 

Whilst ring opening of epoxides (Volume 6, Chapter 1.3) is really beyond the scope of this review, two recent papers are noteworthy poorly nucleophilic amines can be reacted very cleanly as their di-ethylaluminum derivatives,and a start has been made on chiral induction of opening of epoxides (e.g. cyclohexene oxides).Amino alcohols have been resolved by enantioselective enzymatic hydrolysis of their acetates. Ring opening of phthalimidoaziridines has bwn achieved with water, phenol and tosic acid, amongst other nucleophiles,giving products of formal N—O addition to the double bond. 

The reaction of (1) with cyclohexene oxide produces the trans-cyclohexanol derivative (6). Acetylation of (6) followed by mercuric ion-promoted hydrolysis afforded the acetoxy aldehyde (7) in 82% overall from cyclohexenc oxide. 

The method described is essentially that of Swem, Billen, Findley, and Scanlan. /mM5-l,2-Cyclohexanediol also has been prepared by hydrolysis of cyclohexene oxide. j-l,2-Cydo-hexanediol has been prepared by the reaction of cyclohexene with hydrogen peroxide in tertiary butyl alcohol with osmium tetroxide as a catalyst. Hydrogenation of catechol over Raney nickel catalyst at 150° gives a mixture (m.p. 73-77°) of cis- and trans-1,2-cyclohexanediols. ... 

The acid-catalyzed hydrolysis of p-phenyl-substituted cyclohexene oxides 49a-d yields diols resulting from cis and "trans addition of water to the epoxide group (Scheme 14). It was initially reported that the cis/trans diol ratio correlates well with the electronic effect of the / -substituent, and varied from 7.5 93.5 for p-nitro-sub-stituted oxide 49d to 95.3 4.7 for p-methoxy-substituted epoxide 49a.56 58 Later work established that methoxy-substituted diols 50a and 51a underwent isomerization under the conditions of acid-catalyzed epoxide hydrolysis, and that the cis/ trans diol ratios for hydrolysis of 49a-c are quite similar.59... 

The cis and trans diols 55b and 56b are sufficiently reactive in dilute acid solution to undergo equilibration, and the tram diol was determined to be more stable than the cis diol by a factor of 3. In this system, therefore, the major diol from acid-catalyzed hydrolysis is the less stable isomer. This result contrasts with the results from acid-catalyzed hydrolysis of phenyl-substituted cyclohexene oxides, where the major cis diol product is also more stable than the corresponding trans diol. In the hydrolysis of indene oxides 53a, b, therefore, effects that are present in the transition state but absent in the products must play major roles in controlling the cis/trans product ratio. 

The Hydrolysis of cis and trans Cyclohexene Chlorohydrin. When trans cyclohexene chlorohydrin is treated with strong alkali, trans cyclohcxene glycol is obtained. Thus inversion does not appear to have occurred during the displacement. When the reaction is carried out with the cis isomer, cyclohexanone is formed.27 These facts can be explained if it is assumed that the first step in the reaction is the removal of a proton from the hydroxyl group (XXI to XXIII and XXII to XXIV), followed by the displacement of chloride ion by the alkoxide ion of the trans form (XXII1 to XXV) and by a hydride ion in the cis form (XXIV to XXVII). Displacement by alkoxide leads to cyclohexene oxide (XXV), and this intermediate can be further attacked by hydroxide ion to give the dl trans glycol (XXVI). Cyclohexanone is produced by the hydride displacement (XXIV to XXVII) ... 

The oxidation of cyclohexene using hydrogen peroxide was chosen as a test reaction for the catalytic evaluation of the titanium modified hexagonal NaY sanq)les. Scheme I illustrates some of the typical products of cyclohexene oxidation. The epoxide and the diol which is a hydrolysis product of the epoxide, generally reflect a concerted process. In contrast the allylic alcohol and ketone are often ascribed to an autoxidation or radical process. We anticipated that some homolytic decomposition of the peroxide may be observed with these acidic zeolites. In fact, there was -74% conversion of H2O2 over calcined hexagonal NaY after heating at 55 C for 24 hours. This resulted in only a 1% conversion of... 

The y-ketone 135 can be made by reaction of 128 with cyclohexene oxide followed by oxidation. Baeyer-Villiger rearrangement gives mostly (24 1) the lactone 136 with the right regio-chemistry for elimination after hydrolysis to give26 only Z-137. 

The (very useful) hydrolysis of cyclohexene oxide 236 to give the C2 symmetrical diol 238 is difficult with the standard Co salen 235. However, this reaction can be achieved in high yield and enantiomeric excess with a special oligomeric form of the salen.54 The oligomeric form simply contains several salen complexes connected together in each molecule. This has enhanced reactivity for certain reactions. Reactions which proceed exceptionally well with a dimeric form of the catalyst are believed to make use of two active sites and thus benefit from the entropic advantage of having them both in the same species.55... 

Jacobsen and co-workers have used similar catalysts in the enantioselective opening of epoxide rings. Stereospecific hydrolysis with a cobalt acetate chelate can be used to resolve racemic epoxides.97 Propylene oxide was opened with trimethylsilylazide in the presence of a 7 7 chromium azide chelate catalyst to produce (5)-l-azido-2-trimethyl-siloxypropane in quantitative yield with 97% ee.98 Cyclohexene oxide was opened with benzoic acid in the presence of 1 mol% cobalt chelate catalyst to give the hydroxyben-zoate in 98% yield with 77% ee.99... 

Recently, encouraging progress was made in the hydrolysis of cyclopentene oxide and cyclohexene oxide using the yeast Rhodotonda glutinis195L The corresponding (R,R)-trans-diols were obtained in over 90% optical and chemical yields. However, asymmetric hydrolysis of meso-epoxides by bacterial and fungal epoxide hydrolases is still impeded by insufficient selectivities. 

The structures of the phosphorate products have not been established with certainty. They appear to contain an anhydride structure, since they react vigorously with water and with alcohols. Oxidative hydrolysis of the product from cyclohexene with 40% nitric acid liberates half of the phosphorus as phosphoric acid, and gives a phosphonic acid which can be isolated as the lead salt (28,32). The analysis of the lead salt is in agreement structure I (28,29>. It seems likely, however,... 

It is noted that an alternative. route to trans diols is available by hydrolysis of epoxides. Reaction of cyclohexene with MCPBA gives cyclohexene oxide and hydrolysis (acid or base) gives trans-1,2-cyclohexanediol. 

El-Amamy and Mill (1984) measured the effect of the surface acidity of mont-morillonite and kaolinite on the hydrolysis rate constants for a number of chemicals containing hydrolyzable functional groups that exhibit acid-catalyzed, base-catalyzed, and neutral hydrolysis. The chemicals that were studied included ethyl acetate, cyclohexene oxide, isopropyl bromide, l-(4-methoxyphenyl)-2,3-epoxypropane, and N-methyl-p-tolyl carbamate (MTC). Aqueous suspensions of... 

An optically active polycarbonate (271) has been synthesized by asymmetric synthesis copolymerization of cyclohexene oxide and CO2 with optically active Zn catalysts 272 and 273. " Through hydrolysis of the polymer giving 1,2-dihydroxycyclohexane, the absolute configuration was found to be R,R). The optical purity of the polymer was estimated to be 72% ee and 80% ee with the catalysts 272 and 273, respectively. 

Scheme 5.27) [76]. A high yield of the enantiomerically enriched product is obtained, although the enantiomeric excess is very low. The enzymatic hydrolysis of achiral cyclohexene oxide is also an important historical example [77]. Asymmetric bromination of cyclohexene catalysed by a cinchona alkaloid might involve DKR of conformational enantiomers of the olefinic substrate and/or bromonium ion intermediates [78]. 

Cyclic 1,2-diols can be produced stereoselectively from cycloalkenes. For example, a racemic mixture of the enantiomeric frflns-l,2-cyclohexanediols 7 and 8 is produced by reaction of a peracid with cyclohexene and hydrolysis of the intermediate epoxide 13 (Eq. 7.1). Oxidation of this alkene by permanganate, on the other hand, gives ds-l,2-cyclohexanediol (6), as shown in Equation 7.2. The intermediate in this process is presumably the cyclic manganese-containing species 14, which is not isolated. 

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