L-Methylstyrene

The results obtained in reactions involving the two first examples showed a reduced catalytic activity compared to the homogeneous catalyst, a situation that may be due to diffusion problems. Enantioselectivity was similar or slightly lower than in solution, with 80% ee [21] and 58% ee [22] in the epox-idation of ds-/l-methylstyrene with NaOCl providing the best results. Only in the last example was an improvement in enantioselectivity reported from 51% to 91% ee in the epoxidation of a-methylstyrene. Recovery of the catalyst was only considered in one case [21] and a significant decrease in enantioselectivity was observed on reuse. 

Ortiz de Montellano PR, JA Eruetel, JR Collins, DL Camper, GH Loew (1991) Theoretical and experimental analysis of the absolute stereochemistry of ci5-[l-methylstyrene epoxidation by cytochrome P-450,j . JAm Chem Soc 113 3195-3196. 

Lead(IV) in acidic media has been found to promote oxidative addition of Cl-, CF3CO2-, AcO-, MeS03- and CIO4- to cyclohexene, 1-hexene and styrene433. Sonochemical switching from ionic to radical pathway in the reactions of styrene and fraws-/l-methylstyrene with (AcO Pb has been observed434. 

Indene derivatives 264a and 264b are formed by the intramolecular reaction of 3-methyl-3-phenyl-l-butene (263a) and 3,3,3-triphenylpropylene (263b) [237]. Two phenyl groups are introduced into the /3-substituted -methylstyrene 265 to form the /3-substituted /3-diphenylmethylstyrene 267 via 266 in one step[238]. Allyl acetate reacts with benzene to give 3-phenylcinnamaldehyde (269) by acyl—O bond fission. The primary product 268 was obtained in a trace amount[239]. 

Eriedel-Crafts reaction of naphthalene or tetrahydronaphthalene derivatives with those of styrene or alkylbenzenes has been used in the preparation of high viscous fluids for traction drive (195). Similarly, Eriedel-Crafts reaction of tetraline and a-methylstyrene followed by catalytic hydrogenation provided l-(l-decalyl)-2-cyclohexyl propane, which is used as a highly heat resistant fluid (196). 

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). 

Gumylphenol. -Cumylphenol (PGP) or 4-(1-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acid catalysis. a-Methylstyrene is a by-product from the production of phenol via the cumene oxidation process. The principal by-products from the production of 4-cumylphenol result from the dimerization and intramolecular alkylation of a-methylstyrene to yield substituted indanes. 4-Cumylphenol [599-64-4] is purified by either fractional distillation or crystallization from a suitable solvent. Purification by crystallization results in the easy separation of the substituted indanes from the product and yields a soHd material which is packaged in plastic or paper bags (20 kg net weight). Purification of 4-cumylphenol by fractional distillation yields a product which is almost totally free of any dicumylphenol. The molten product resulting from purification by distillation can be flaked to yield a soHd form however, the soHd form of 4-cumylphenol sinters severely over time. PGP is best stored and transported as a molten material. 

Dicumjlphenol (2,4-DCP) or 2,4-bis(l-methyl-l-phenylethyl)phenol is produced by the alkylation of phenol with a-methylstyrene under acidic catalysis. The cmde alkylation product contains 4-cumylphenol, 2,4-dicumylphenol, and 2,4,6-tricumylphenol along with some olefin oligomers. Pure... 

Dimercapto-l,3,4-thiadiazole derivatives, accelerated by amines, are used to cross-link chlorinated polyethylene. Polyisobutylene containing brominated i ra-methylstyrene cure functionahty can be cross-linked in polymer blends with dimercapto-1,3,4-thiadiazole derivatives accelerated with thiuram disulfides. Trithiocyanuric acid is suggested for use in polyacrylates containing a chlorine cure site and in epichlorohydrin mbbers. 

It is typical, for instance, of syndiotactic polystyrene (s-PS) [7-9] and syndiotactic poly- p-methylstyrene (s-PPMS) [10] to present crystalline forms with a transplant conformation of the chains (shown for s-PS in Fig. 1) as well as crystalline forms with sequences of dihedral angles of the kind TTG+G+ (or the equivalent G G TT), corresponding to a s(2/l)2 helical symmetry of the chains (shown for s-PS in Fig. 1). 

Fetters L.J. and Morton M., Synthesis and properties of block pol3miers. I. Poly(a-methylstyrene)-polyisoprene-poly(a-methylstyrene). Macromolecules, 2, 453, 1969. 

In the presence of In powder 2-cycIohexen-l-one is converted by allyl iodide and Me3SiCI 14, in 63% yield, into the 1,4-addition product 2179 [84], which is also obtained in 73% yield by Sakurai 1,4-addition ofallyltrimethylsilane 82 to 2-cyclohexene-l-one in the presence of excess Me3SiCl 14 and catalytic amounts of InCl3 [85] (Scheme 13.25). Ytterbium] 111) triflate-catalyzed imino-ene reactions of N-tosylaldimines with a-methylstyrene are dramatically accelerated on addition of Me3SiCl 14 [85 a]. 

The regiochemistry of Al-H addition to unsymmetrically substituted alkynes can be significantly altered by the presence of a catalyst. This was first shown by Eisch and Foxton in the nickel-catalyzed hydroalumination of several disubstituted acetylenes [26, 32]. For example, the product of the uncatalyzed reaction of 1-phenyl-propyne (75) with BujAlH was exclusively ds-[3-methylstyrene (76). Quenching the intermediate organoaluminum compounds with DjO revealed a regioselectivity of 82 18. In the nickel-catalyzed reaction, cis-P-methylstyrene was also the major product (66%), but it was accompanied by 22% of n-propylbenzene (78) and 6% of (E,E)-2,3-dimethyl-l,4-diphenyl-l,3-butadiene (77). The selectivity of Al-H addition was again studied by deuterolytic workup a ratio of 76a 76b = 56 44 was found in this case. Hydroalumination of other unsymmetrical alkynes also showed a decrease in the regioselectivity in the presence of a nickel catalyst (Scheme 2-22). 

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 reactions of a number of substituted styrenes have also been investigated. The majority give rise to analogues of either (61) or (62). trans-(3-Methylstyrene gave only l,2,3,4-tetrafluoro-10-methylphenan-threne and no cyclo-adducts were obtained with (3, (3-dimethylstyrene. We assume that the steric requirement of the as-(3-methyl group prevents the formation of the transition state leading to the initial cyclo-adduct. 

The determination of large values of the rate constant ratio ks/kpfrom the low yields of alkene product that forms by partitioning of carbocations in nucleophilic solvents. These rate constant ratios may then be combined with absolute rate constants for the overall decay of the carbocation to give absolute values of kp (s ).14 16 For example, the reaction of the l-(4-methylphenyl)ethyl carbocation in 50/50 (v/v) trifluoroethanol/water gives mainly the solvent adducts and a 0.07% yield of 4-methylstyrene from proton transfer to solvent, which corresponds to kjkp = 1400. This can be combined with ks = 6 x 109 s V4 to give kp = 4.2 x 106 s l (Table 1). 

The precipitated silica (J. Crosfield Sons) was heated in vacuo at 120° for 24h. before use. Two grades of surface areas 186 and 227 m g l (BET,N2), were used during this project. Random copolymers, poly(methyl methacrylates) and polystyrene PS I were prepared by radical polymerization block polymers and the other polystyrenes were made by anionic polymerization with either sodium naphthalene or sodium a methylstyrene tetramer as initiator. The polymer compositions and molecular weights are given in Table I. 

The extent of asymmetric induction was low. L 1 was the most effective to induce asymmetry in the adduct of a-methylstyrene and methyl-... 

Methyldichlorosilane was by far the most reactive in hydrosilation of 1,1-disubstituted olefins. Trialkylsilanes did not add at all, even at 120°C. Trichlorosilane gave complicated results involving isomerization of olefins and dimerization of a-methylstyrene, and products were not optically active. 2-Methylbutene-2 and trichlorosilane gave two adducts, 2-meth-ylbutyltrichlorosilane and 3-methylbutyltrichlorosilane. The latter required isomerization of the olefin. 2,3-Dimethylbutene-l gave one adduct in 70% yield, and it was optically slightly active [0.8% (R) isomer]. 

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