Methyl Methylstyrene, epoxidation

Such copolymers of oxygen have been prepared from styrene, a-methylstyrene, indene, ketenes, butadiene, isoprene, l,l-diphen5iethylene, methyl methacrjiate, methyl acrylate, acrylonitrile, and vinyl chloride (44,66,109). 1,3-Dienes, such as butadiene, yield randomly distributed 1,2- and 1,4-copolymers. Oxygen pressure and olefin stmcture are important factors in these reactions for example, other products, eg, carbonyl compounds, epoxides, etc, can form at low oxygen pressures. Polymers possessing dialkyl peroxide moieties in the polymer backbone have also been prepared by base-catalyzed condensations of di(hydroxy-/ f2 -alkyl) peroxides with dibasic acid chlorides or bis(chloroformates) (110). 

Finally, with the aim of discovering novel chiral oxomolybdenum catalysts able to perform enantioselective alkene epoxidations, Kuhn et al. have reported the exploration of the catalytic behaviour of a series of dioxomolybdenum(VI) complexes with chiral cw-8-phenylthiomenthol ligands derived from ( + )-pulegone. Therefore, the epoxidation of c -p-methylstyrene using t-butyl-hydroperoxide as the oxidant and performed in the presence of ( + )-(2i ,5i )-2-[1-methyl-l-(phenylthio)ethyl]-5-methylcyclohexanone oxime as the ligand, did not produce, however, a significant optical induction in these conditions. 

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. 

RuCl(dmso)(bpy)2]Cl and [RuCl(SOMePh)(bpy) ]Cl, called respectively rac-Ru-1 and A-Ru-2 by the authors, are made by microwave irradiation of cis-RuCljtbpy) with the the sulfoxide ligands. Trani-stilbene, styrene and R-styrene (R=p-MeO, a and P-methyl) were epoxidised by [RuCl(dmso)(bpy)3]Vaq. Ph(IOAc)2/CH3Cl3/40°C, while with [RuCl(SOMePh)(bpy)3]V TBHP/water-CH Cl fran -stilbene, fran -P-methylstyrene gave the (R,R) epoxides [947]. 

Studies on the epoxide of (8-methylstyrene showed that phenyl migration apparently occurred more readily than methyl migration... 

For asymmetric epoxidation of methylstyrene, dehydronaphthalene, and meta-chlorobenzoic acid in the presence of A-methylmorpholine oxide, Reger and Janda synthesized manganese complexes 33 with the salen ligand bound to the methyl ether of poly(ethylene oxide) [69]. 

Besides SMOs, recombinant E. coli expressing the xylene monooxygenase from P. putida mt-2, which typically oxidizes toluene and xylenes to the corresponding benzyl alcohol derivatives, can as well catalyze the epoxidation of styrene into (S)-styrene oxide [49, 108]. However, the substrate spectrum for the enzyme was extremely narrow. Only styrene, 3-chlorostyrene, and 4-chlorostyrene were oxidized without side reactions, yielding epoxides with 92%, 96%, and 37% ee, respectively, while 3-methylstyrene and 4-methylstyrene were primarily oxidized at the methyl moiety rather than the vinyl group [49]. 

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