A-Methylstyrene, derivatives

Wang s approach for the synthesis of enyne-allenes focused on ene-allenyl iodide 45 (Scheme 14.12) [24]. Palladium-catalyzed Sonogashira reaction of 45 with terminal alkynes 46 (R= Ph or CH2OH) proceeded smoothly under mild reaction conditions in the presence of the cocatalyst cuprous iodide and n-butylamine. The initially formed enyne-allene 47b with substituent R= CH2OH cyclized spontaneously to the corresponding a-methylstyrene derivative 48. 

Similarly, isomerized carbenium ions are formed in polymerizations of a-methylstyrene derivatives by either a 1,3-intramolecular or bimolecular methide anion shift, or by reaction of carbenium ion with an exo-unsatu-rated oligomer [cf., Eq. (10)] [13]. 

H5P, an a-methylstyrene derivative, seems to have a low ceiling temperature and consequently did not homopolymerize but underwent copolymerization with styrene, methyl methacrylate, and n-butyl acrylate. Based on the homopolymerization attempts, it appears that 2H5P is present as isolated monomer units in these copolymers. The co-polymerization parameters of 2H5V and 2H5P with styrene, methyl methacrylate, and n-butyl acrylate have also been determined. The results are shown in Figure 3 The copolymerization experiments were done to 5 conversions. 

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). 

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

Several alkenes are converted to aziridines by treating with oxaziridine (52) at elevated temperatures. Styrene, a-methylstyrene and their derivatives substituted in the benzene ring react smoothly, and so do 1,1-diphenylethylene, indene and acrylonitrile (74KGS1629). 

The pn- and p -values for electrophilic bromine additions to arylolefins are in the same range as those for other reactions via analogous benzylic carbocations. However, generally the comparisons are only qualitative because of significant differences in the experimental conditions and in the mechanisms. For example, as has already been mentioned, the reaction constant of t-cumyl chloride methanolysis is —4.82 (Okamoto et al., 1958), i.e. slightly higher than that for a-methylstyrene bromination in methanol, where the intermediate resembles that in the solvolysis of cumyl derivatives (Scheme 13). 

In comparison with the platinum catalysts, rhodium catalysts are much more reactive to effect addition of bis(catecholato)diboron even to non-strained internal alkenes under mild reaction conditions (Equation (5)).53-55 This higher reactivity prompted trials on the asymmetric diboration of alkenes. Diastereoselective addition of optically active diboron derived from (li ,2i )-diphenylethanediol for />-methoxystyrene gives 60% de (Equation (6)).50 Furthermore, enantioselective diboration of alkenes with bis(catecolato)diboron has been achieved by using Rh(nbd)(acac)/(A)-QUINAP catalyst (Equation (7)).55,56 The reaction of internal (A)-alkenes with / //-butylethylene derivatives gives high enantioselectivities (up to 98% ee), whereas lower ee s are obtained in the reaction of internal (Z)-alkenes, styrene, and a-methylstyrene. 

The aromatic mono-olefins have been studied more extensively and intensively than any other class of monomers. Styrene, in particular, has received much attention, but nuclear and side-chain substituted styrenes are still largely unexplored, except in regard to copolymerization. The only other aromatic monomers which have been studied in any detail are a-methylstyrene [1] and 1,1-diphenylethylene and some of its derivatives [10]. It is strange that even readily available monomers, such as indene [80] and acenaphthylene [54b, 81], have hardly been investigated. 

The 2 1 adduct 308 obtained from 303 with 2-chloro-2-phenylpropane (reaction 42) is probably derived from the addition of 303 to a-methylstyrene (307)626. 

With conventional techniques and electrolytes, it was not possible to obtain living anions because they are rapidly protonated by tetraalkylammonium salts and residual water. The first report of the production of living polymers by an electrolytic method has to be attributed to Yamazald et al. [247], who used tetrahydrofuran as solvent, and LiAlH4 or NaAl(C2H5)4 as electrolyte for the polymerization of a-methylstyrene. A similar technique was used to polymerize styrene as well as derivatives [248-252]. 

The abstraction ability from cyclohexane of radicals derived from dialkyl peroxides has been reported. The experiments were performed with and without the trapping agent MSD (a-methylstyrene dimer), the abstracting species being alkoxy radicals derived from the peroxides. However, some dehydro dimer yields indicated that abstraction was also occurring by alkyl radicals. 

The hydrosilylation of alkenes with trialkylsilanes in the presence of Lewis acid catalysts under mild conditions gives the corresponding (trialkylsilyl)alkanes [Eq. (22)]. Reaction with terminal alkenes such as 1-hexene and 1-dodecene at room temperature gives hydrosilylation products in 57 and 58% yields, respectively. Reactions with activated styrene derivatives such as styrene, / -chlorostyrene, and a-methylstyrene at —20°C afford hydrosilylated products in 55-61% yields. ... 

Arylalkenes can undergo various reactions when treated with sodium, since compounds such as a-methylstyrene are both olefins with allylic hydrogens and styrenes, both of which are reactive. The reaction of a-methylstyrene with sodium has been reported by Bergmann et al. (6i) to yield tetramers. More recent work by Kolobielski and Pines (56) has shown that dimers and products derived from dimers are formed when this compound is heated with a sodium-benzyl-sodium catalyst. Some of the major products were cumene (VII), p-terphenyl (VIII), and 1-methyl-1,3-diphenyl-cyclopentane (IX). 

Radical-anions derived from styrene derivatives are nucleophilic in character. Electrochemical reduction of a-methylstyrene 5 gives the radical-anion intermediate, which in the absence of other electrophiles is sufficiently nucleophilic to attack dimethylfonnamide or acetonitrile [19], The radical-anion from styrene 6 under-... 

Hydrocarbon resins comprise a range of low-molecular-weight products (M < 3000) used as adhesives, hot-melt coatings, tackifying agents, inks, and additives in rubber. These include products based on monomers derived from petroleum as well as plant sources. The petroleum-derived products include polymers produced from various alkenes, isoprene, piperylene, styrene, a-methylstyrene, vinyltuolene, and dicyclopentadiene. The plant-derived products include polyterpenes obtained by the polymerization of dipentene, limonene,... 

Photolysis of l-methylnaphtho[l,8-de]triazine (32, R = Me) also results in extrusion of nitrogen and formation of a diradical intermediate (167). Thus, reaction in cyclohexane as solvent gives, among other products, bicyclohexyl and 1-methylaminonaphthalene, while 8-phenyl-1-methylaminonaphthalene is the only product formed when benzene is used as solvent. Photochemical decomposition of 32, R = Me, in the presence of olefins results in an unusual ring transformation, and with a-methylstyrene, for example, the triazine is converted into the dihydroazaphenalene derivative (168). When vinyl bromide and trans-... 

Styrene and its derivatives, such as a-methylstyrene, atropic acid, cinnamic acid, and cinnamyl alcohol, were readily reduced (acids were added as their salts), yielding the corresponding dihydro derivatives (Table I). However, propenyl-benzene, tmst/m-diphenylethylene, and stilbene absorbed no hydrogen. 

Cumene oxidized relatively slowly, at about 1/13 the rate of p-xylene. This was not caused by the formation of phenol, as might be expected by an acid-catalyzed rearrangement of cumene hydroperoxide. No phenol or product clearly derived from phenol, as by radical attack or by oxidation to a quinone, was detected at any time in the reaction mixture. The two major products were a-methylstyrene and 2-phenylpropylene oxide their concentrations increased with time. The group at Shell also observed the formation of a-methylstyrene and 2-phenylpropylene oxide among the products of cumene oxidation in butyric acid at 140°C. with cobalt and manganese catalysts (30). 

The copolymerization equation is valid if all propagation steps are irreversible. If reversibility occurs, a more complex equation can be derived. If the equilibrium constants depend on the length of the monomer sequence (penultimate effect), further changes must be introduced into the equations. Where the polymerization is subjected to an equilibrium, a-methylstyrene was chosen as monomer. The polymerization was carried out by radical initiation. With methyl methacrylate as comonomer the equilibrium constants are found to be independent of the sequence length. Between 100° and 150°C the reversibilities of the homopolymerization step of methyl methacrylate and of the alternating steps are taken into account. With acrylonitrile as comonomer the dependence of equilibrium constants on the length of sequence must be considered. 

Figure 11 shows a compilation of the compositions of the polymers which have been polymerized from different monomer mixtures as a function of polymerization temperature. The curves plotted next to the measured points were calculated at temperatures below 100 °C by Equation 33 and at temperatures above 100 °C by Equation 17. The dotted curves for temperatures above 100 °C were calculated by Equation 33. In addition to the measured values taken from Tables III and V, Figure 11 also contains some measured points at 0°C. Polymerization was done in flasks which were stored in a thermally controlled room for a long time (e.g.y with 30 mole % a-methylstyrene, 34 days, with 50 and 70 mole %, 166 days). It is apparent that the curve derived by Equation 17 agrees well with the measured points. However, the dotted curve at higher temperatures, calculated by Equation 33 shows significant deviations. 

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