2- Bromo-2-methylstyrene

Cumene 5 2-Phenylacrolein, 25 a-bromo-methylstyrene, 10 2-phenylallyl acetate, 5... 

Bromo -1 - phenylpropylene (Cinnamyl (jenzen bromidet y bromopropenylbenzene, a-bromo-methylstyrene)... 

The initial series of major tranquilizers consists of alkylated derivatives of 4-aryl-4-hydroxypiperidines. Construction of this ring system is accomplished by a set of rather unusual reactions. Condensation of methylstyrenes with formaldehyde and ammonium chloride afford the corresponding hexahydro-1,3-oxazines (119). Heating these oxazines in the presence of acid leads to rearrangement with loss of water to the tetrahydropyridines. Scheme 1 shows a possible reaction pathway for these transformations. Addition of hydrogen bromide affords the expected 4-bromo compound (121). This last is easily displaced by water to lead to the desired alcohol (122) The side chain (123) is obtained by Friedel-Crafts acylation of p-fluorobenzene with 4-chloro-butyryl chloride. Alkylation of the appropriate arylpiperidinol with 123 affords the desired butyrophenone derivative. Thus,... 

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. 

Also examined was the copolymerization of a-methylstyrene and 4-bromo-styrene [169], again with similar effect, here using a small Buehler-type probe of 25 kHz. This did not produce any sonochemically induced polymerization of the monomer over a 24-hour period without the application of an electric potential, representing an important control experiment since ultrasound is well known to produce radical species which could themselves influence polymerization. 

High-fiurity o- and p-methylstyrenes are obtained from the corresponding bromo-toluenes by this method." Some other useful preparations are based on the arylation of l,3-dioxep-5-ene, allyl carbamates, and cyclization of vinylphosphonites. ... 

It is unlikely that a free carbocation (or a solvent-separated ion pair) is the intermediate in these addition reactions, however. Rolston and Yates studied the addition of bromine to derivatives of styrene in acetic acid and other solvents. In acetic acid, the products were found to be the 1,2-dibromo addition products plus variable amoimts of the bromoacetoxy products derived from solvent. For all of the styrene derivatives studied except ) ,) -dimethylstyrene, the solvent incorporation product in each case was exclusively the l-acetoxy-2-bromo compound—the product expected from nucleophilic attack of solvent on a benzylic carbocation. The dibromo and bromoacetoxy products were formed with different stereoselectivity. The reaction of ds-jS-methylstyrene (16) produced ( )-t/ireo-l,2-dibromo-l-phen-ylpropane (15, 58%), ( )-eryf/iro-l,2-dibromo-l-phenylpropane (14, 22%), and ( )-t/ireo-l-acetoxy-2-bromo-l-phenylpropane (17, 20%). 

In both cases, therefore, the bromoacetoxy products were those expected from anti addition, while formation of the dibromo products was much less stereoselective. Furthermore, the fraction of dibromide formed by apparent syn addition to cis-j8-methylstyrene varied with solvent polarity, from 27% in acetic acid to 55% in nitrobenzene. The results were discussed in terms of initial formation of an intimate bromo-carbocation-bromide ion pair that can undergo attachment of acetic add from the face of the ion away from the bromide ion, thus leading to anti formation of bromoacetoxy compounds. Reorientation of the bromide ion within the solvent shell for backside attachment to the bromonium ion provides time for rotation about the carbon-carbon single bond of the bromocarbocation, so the dibromo products are formed with less stereoselectivity. 

Butyl rubber (HR) is an isobutylene-based rubber which includes copolymers of isobutylene and isoprene, halogenated butyl rubbers, and isobutylene/p-methylstyrene/bromo-p-methylstyrene terpoly-mers. HR can be slurry polymerized from isobutylene copolymerized with small amounts of isoprene in methyl chloride diluent at -130 to - 148°F (-90 to - 100°C). Halogenated butyl is produced by dissolving butyl rubber in a hydrocarbon solvent and introducing elemental halogen in gas or liquid state.Cross-linked terpolymers are formed with isobutylene + isoprene + divinylbenzene. 

See p-Bromo-a-methylstyrene. Methylstyrylcarbrnol (y Bydroxy-tt-butenyh benzene, l-phenyl-l-bvtenol-B)... 

One year later, the same authors studied the biohydrolysis of seven differently substituted a-methylstyrene oxide derivatives, including the para-bromo-a-methyl styrene oxide, using ten different EHs [14]. The best results were obtained with the... 

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