3.4- Epoxy-2-methyl-l-butene

Isoprene epoxidized on the vinyl group (l,2-epoxy-3-methyl-3-butene, 14) would also be an attractive synthon for monoterpenoids if it were more readily accessible. Among the possible preparative methods (Scheme 2), acid-catalyzed isomerization of 2,3-epoxy-l-halo-3-methylbutanes (epoxidized prenyl halides) and dehydrohalogenation of the resulting isomers seemed the best route until chlorination of prenyl acetate (15, R = OAc) with hypochlorous acid was published. Dehydration of the mixture of products gave a maximum of the chloroacetate 16, which yielded the epoxide 14 with sodium hydroxide in methanol. ... 

These reactions proceed by initial ozone attack on the C = C bond of the olefin. An intermediate ozonide is formed, which rapidly decomposes to a carbonyl and a biradical. The biradical can be stabilized, or it can decompose. Paulson et al. (1991b) found the products methacrolein, methyl vinyl ketone, and propene, in yields of 68%, 25%, and 7%, respectively. Based on the presence of epoxides in the ozone/isoprene system, Paulson et al. concluded that 0(3P) was being formed. Calculations indicated that 0.45 0(3P) radicals were formed for every ozone/isoprene reaction. However, Atkinson et al. (1993) recently showed that the epoxides were formed directly from the reaction with ozone rather than the reaction with 0(3P). The epoxides formed were l,2-epoxy-2-methy 1-3-butene and l,2-epoxy-3-methyl-3-butene, in yields of 0.028 and 0.011, respectively. There was also definite evidence for the formation of OH radicals in the ozone system, thus causing difficulties in product analyses. Each ozone/isoprene reaction yielded 0.68 OH radicals (Paulson et al., 1991b). 

Rate coefficients for the reactions of OH and O3 with 2- and 3-methyl-3-butene-1,2-diol and l,2-epoxy-3-methyl-3-butene, the latter having been reported very recently as product from isoprene + O3 [11], were determined by use of a relative rate technique. In the O3 experiments sufficient CO was added to scavenge > 90 % of OH radicals eventually being formed. For the O3 reaction of the diols absolute measurements were carried out in addition by monitoring the decay of O3 under pseudo-first order conditions. Absolute and relative rate data were in good agreement. The average values at 295 2 K are ... 

Isoprene is fonned endogenously at the rate of 1.9 imol/kg per hour in both rats and mice. l,2-Epoxy-2-methyl-3-butene (80%) and 3,4-cpoxy-2-mcthyl-1-butene (20%) are two major metabolites in mouse liver microsomes. The 3,4-epoxide can be further metabolized to isoprene diepoxide. Both rats and mice exhibited saturation kinetics when exposed to isoprene at concentrations above 300 ppm [837 mg/m ]. The maximal rate of metabolism in vivo is more than three times greater in mice than in rats (lARC, 1994). 

Hydrogen sulfide baa been found to attack the terminal epoxide carbon of l,2 epoxy 2-methyl-3-butene as expected (Eg, bSBa). 

Epoxy-4-hydroxy-2-(3-methyl-3-buten-1 -ynyl)-2-cyclohexen-l-one, see H-10004... 

NaHCOg and a trace of 2,6 di tert-butyl-p-cresol as radical inhibitor added to a soln. of isoprene in chloroform, the stirred, ice-cooled suspension treated drop-wise under Ng with 82%-peroxyacetic acid during 6 hrs., stirring continued 24 hrs., filtered, the resulting soln. of crude 3,4-epoxy-3-methyl-l-butene (Y 80%) treated with ethyl acetate followed by CuCl2 2H20 and LiCl, and refluxed ca. 15 min. at 90° (E)-4-chloro-2-methylcrotonaldehyde (Y 78-80%). G.Eletti-Bianchi, F. Centini, and L. Re, J. Org. Chem. 41, 1648 (1976). 

Addition of Grignard reagents to 1,2 epoxy-3-butene givw mixture of alcohols, MethylmagueBium bromide, for example gives 2-penten-l-ol as the principal product, together with some 2-methyl- -buten l-ol (Eq. 837). The former can he regarded as a... 

Materials. VEC was prepared by the catalyzed addition of CO2 to 3,4-epoxy-l-butene using conditions typical of that used industrially [77], then purified by vacuum distillation. Other raw materials were used as received without any additional purification. Mixed xylenes, vinyl acetate (VA), butyl acrylate (BA), butyl methacrylate (BMA), methyl methacrylate (MMA), styrene (St), and t-butyl hydroperoxide were obtained from Aldrich Chemical Company. Lupersol 575 (t-amyl peroxy (2-ethylhexanoate)) was supplied by Elf Atochem. Vazo 67 (2,2 -azobis(2-methylbutyronitrile)) was obtained from DuPont Chemical Company. Vinyl pivalate (NE05), vinyl 2-ethylhexanoate (V2EH), Tergitol NP-40 (non-ionic surfactant) and QP-300 (hydroxy ethyl cellulose) were obtained from Union Carbide Coq)oration. Aerosol OT-75 (surfactant) was obtained from Cytec. Sodium formaldehyde sulfoxylate was obtained from Henkel Corporation. Ethyl 3-ethoxy propionate (EEP), propylene glycol monomethyl ether (PM) and PM acetate (PM Ac) are Eastman Chemical Company products. 

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