2- Butene epoxidation

Epoxidation of alkenes is a stereospecific syn addition Which stereoisomer of 2 butene reacts with peroxyacetic acid to give meso 2 3 epoxybu tane Which one gives a racemic mixture of (2/ 3/ ) and (25 35) 2 3 epoxybutane ... 

When (R) 3 buten 2 ol is treated with a peroxy acid two stereoisomenc epoxides are formed in a 60 40 ratio The minor stereoisomer has the structure shown... 

Epoxidation of c -2-butene gives icio-2,3-epoxybutane tra i-2-butene gives a racemic mixture of (2R,3R) and (2S,3S)-2,3-epoxybutane. 

The application of the AE reaction to kinetic resolution of racemic allylic alcohols has been extensively used for the preparation of enantiomerically enriched alcohols and allyl epoxides. Allylic alcohol 48 was obtained via kinetic resolution of the racemic secondary alcohol and utilized in the synthesis of rhozoxin D. Epoxy alcohol 49 was obtained via kinetic resolution of the enantioenriched secondary allylic alcohol (93% ee). The product epoxy alcohol was a key intermediate in the synthesis of (-)-mitralactonine. Allylic alcohol 50 was prepared via kinetic resolution of the secondary alcohol and the product utilized in the synthesis of (+)-manoalide. The mono-tosylated 3-butene-1,2-diol is a useful C4 building block and was obtained in 45% yield and in 95% ee via kinetic resolution of the racemic starting material. 

Due to the abundance of epoxides, they are ideal precursors for the preparation of P-amino alcohols. In one case, ring-opening of 2-methyl-oxirane (18) with methylamine resulted in l-methylamino-propan-2-ol (19), which was transformed to 1,2-dimethyl-aziridine (20) in 30-35% yield using the Wenker protocol. Interestingly, l-amino-3-buten-2-ol sulfate ester (23) was prepared from l-amino-3-buten-2-ol (22, a product of ammonia ring-opening of vinyl epoxide 21) and chlorosulfonic acid. Treatment of sulfate ester 23 with NaOH then led to aziridine 24. ... 

Butylene oxide, like propylene oxide, is produced by the chlorohydri-nation of 1-butene with HOCl followed by epoxidation. The reaction conditions are similar to those used for propylene ... 

Show the stereochemistry of the epoxide (see Problem 11.42) you would obtain by formation of a bromohydrin from frnm-2-butene, followed by treatment with base. 

Problem 18.11 Reaction of rA-2-butene with m-chloroperoxvbenzoic acid yields an epoxide different from that obtained by reaction of the trans isomer. Explain. 

Epoxidation of o s-2-butene yields c/s-2,3-epoxybutane., while epoxidation... 

The cyclohexyloxy(dimethyl)silyl unit in 8 serves as a hydroxy surrogate and is converted into an alcohol via the Tamao oxidation after the allylboration reaction. The allylsilane products of asymmetric allylboration reactions of the dimethylphenylsilyl reagent 7 are readily converted into optically active 2-butene-l, 4-diols via epoxidation with dimethyl dioxirane followed by acid-catalyzed Peterson elimination of the intermediate epoxysilane. Although several chiral (Z)-y-alkoxyallylboron reagents were described in Section 1.3.3.3.3.1.4., relatively few applications in double asymmetric reactions with chiral aldehydes have been reported. One notable example involves the matched double asymmetric reaction of the diisopinocampheyl [(Z)-methoxy-2-propenyl]boron reagent with a chiral x/ -dialkoxyaldehyde87. 

Crystallite dimensions play a role in determining the rates of reactions and their control is of fimdamental importance not only for the catalytic activity, but also for the selectivity, since, with low rates of the desired reaction, the relative importance of secondary reactions may be greater. The effects of crystallite dimensions have been demonstrated for 1-butene epoxidation and for phenol hydroxylation, and they are significant for many reactions carried out with hquid phase reactants [17]. 

Reactions of the epoxide of 1-butene with CH3Li gives a 90% yield of 3-pentanol. In contrast, reaction with CH3MgBr under similar conditions gives an array of products, as indicated below. What is the basis for the difference in reactivity of these two organometallic compounds toward this epoxide ... 

By analogy to simple olefins, we propose that 0(3P) initially adds to the 1,4 or 1,2 double bonds in polybutadienes at ambient temperature. Since the rate constants for 0(3P) addition to cis-2-butene and 1-butene (as models for 1,4 and 1,2 double bonds, respectively) are in the ratio 4.2 1 at 298 K ( 6), preferential addition to the 1,4 double bonds is assumed to persist to very high vinyl contents (-8011). The biradical adducts then rearrange to epoxides and carbonyl compounds or give rise to chain rupture and/or crosslinking as a consequence of PIF, according to the scheme ... 

Peroxyacids, RCO-OOH, will also oxidise alkenes, e.g. trans 2-butene (48b), by adding an oxygen atom across the double bond to form an epoxide (49) ... 

Intramolecular oxonium ylide formation is assumed to initialize the copper-catalyzed transformation of a, (3-epoxy diazomethyl ketones 341 to olefins 342 in the presence of an alcohol 333 . The reaction may be described as an intramolecular oxygen transfer from the epoxide ring to the carbenoid carbon atom, yielding a p,y-unsaturated a-ketoaldehyde which is then acetalized. A detailed reaction mechanism has been proposed. In some cases, the oxonium-ylide pathway gives rise to additional products when the reaction is catalyzed by copper powder. If, on the other hand, diazoketones of type 341 are heated in the presence of olefins (e.g. styrene, cyclohexene, cyclopen-tene, but not isopropenyl acetate or 2,3-dimethyl-2-butene) and palladium(II) acetate, intermolecular cyclopropanation rather than oxonium ylide derived chemistry takes place 334 ). 

Figure 11.4 The overall result of epoxidation followed by acid-catalyzed hydrolysis is a stereospecific anti hydroxylation of the double bond. ds-2-Butene yields the enantiomeric 2,3-butanediols tra x-2-butene yields the meso compound.

The epoxidation of nonconjugated olefins is slow123,124 and shows reduced enantioselectivity as compared with the epoxidation of conjugated olefins. For example, enantioselectivities from the epoxidation of (Z)-l-cyclohexyl-1-propene, 3,3-dimethyl-l-butene, and geranyl acetate are 82% (with (34)), 70% (with (34)),123 and 53% (6,7-epoxide, with (26)),124 respectively, and yields of the epoxides are modest. 

Butyne-l,4-diol has been hydrogenated to the 2-butene-diol (97), mesityl oxide to methylisobutylketone (98), and epoxides to alcohols (98a). The rhodium complex and a related solvated complex, RhCl(solvent)(dppb), where dppb = l,4-bis(diphenylphosphino)butane, have been used to hydrogenate the ketone group in pyruvates to give lactates (99) [Eq. (15)], and in situ catalysts formed from rhodium(I) precursors with phosphines can also catalyze the hydrogenation of the imine bond in Schiff bases (100) (see also Section III,A,3). 

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. 

In the case of furans, the epoxidation can lead to hydroxylated furans or to ring opening and final formation of a butene-1,4-dial, which is a Michael acceptor [41]. 

The oxidative addition of hydroxide anion to nitroalkenes, e.g. ( )-2-nitro-2-butene, which leads to epoxides, proceeds by way of radical anions (equation 135)448. 

R. J. Krause, J. E. Sharer, A. A. Elfarra, Epoxide Hydrolase-Dependent Metabolism of Butadiene Monoxide to 3-Butene- 1,2-diol in Mouse, Rat, and Human Liver , Drug Metab. Dispos. 1997, 25, 1013 - 1015. 

Figure 41. A plot of sensitivity to Mo (5.4k) x-ray radiation and 20 kV electron beam radiation for several resists. EPB is epoxidized polybutadiene, P(GMA-EA) is a copolymer of glycidyl methacrylate and ethyl acrylate (COP), PGMA is poly (glycidyl methacrylate), PBS is poly (butene-1 -sulfone), FBM-1 is poly (2,2,3,3-tetrafluoropropyl methacrylate), P(MMA-MA) is a copolymer of methyl methacrylate and methacrylic acid, PMMA is poly (methyl methacrylate). (Reproduced with permission from Ref. 56J...

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