Styrene-diphenylethylene

The second electronic transfer to the oxygen produces the diradical (C) which evolves into monomer formation. The latter possibility (IV) is a homolytlc cleavage giving another anion radical. If the process follows scheme III or IV, we must obtain monomer formation after the oxidation reaction in all cases. We have carried out the oxidation of carbanionic dimers derived from isoprene, crmethylstyrene, styrene, 1,1-diphenylethylene. 

These ructions, which are not well kr wn in organic solvents, are important for the polymerization of monomers of low nucleophilicity (e.g. styrene, 1,1-diphenylethylene ) but can apparently be ne ected when a strong nucleo-phik is present. For this group of nurnomers, the following equilibria must be considered ... 

An SET process involving formation of unstable intermediates (285) is suggested to account for the products observed on irradiation of certain nitroarenes in the presence of styrene, 1,1-diphenylethylene or E-stilbene. High yields of nitrones (286) are isolated when styrene is used. Nitrobenzene, or 4-iodonitrobenzene, in the presence of 1,1-diphenylethylene give the nitrone (287)... 

Molecular oxygen can add to the double bonds of olefins such as styrene, 1,1-diphenylethylene, dimethyl- and diethyl-ketene, vinyl acetate, cyclopentadiene and cyclohexadiene with formation of polymeric peroxy compounds. The course of the reaction corresponds to that of a mixed polymerization 1 r>2 3 4b d... 

Trapping the bicyclic allene 213 with styrene, 1,1-diphenylethylene, furan and several 1,3-dienes also affords [2+2] cycloadducts, such as 214... 

The oxidative coupling of alkenes which have two substituents at the 2 posi-tion, such as isobutylene, styrene, 2-phenylpropene, 1,1-diphenylethylene, and methyl methacrylate, takes place to give the 1,1,4.4-tetrasubstituted butadienes 285 by the action of Pd(OAc)2 or PdCF in the presence of sodium acetate[255-257]. Oxidation of styrene with Pd(OAc)2 produces 1.4-diphenylbutadiene (285, R = H) as a main product and a- and /3-acetoxystyrenes as minor pro-ducts[258]. Prolonged oxidation of the primary coupling product 285 (R = Me) of 2-phenylpropene with an excess of Pd(OAc)2 leads slowly to p-... 

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). 

Dimsyl anion 88 is known to add to styrene, and to 1,1-diphenylethylene in the presence of a base, forming 3-arylpropyl methyl sulfoxides121. Treatment of ( )-3,3-dimethyl thiacyclo-oct-4-ene-l-oxide 89 with n-BuLi gave exo-4,4-dimethyl-2-thiacyclo-[3.3.0]octane 2-oxide 90, a bicyclic addition product of the internal double bond. A similar cyclization was observed in the reaction of 91 with n-BuLi122. 

Two pieces of direct evidence support the manifestly plausible view that these polymerizations are propagated through the action of car-bonium ion centers. Eley and Richards have shown that triphenyl-methyl chloride is a catalyst for the polymerization of vinyl ethers in m-cresol, in which the catalyst ionizes to yield the triphenylcarbonium ion (C6H5)3C+. Secondly, A. G. Evans and Hamann showed that l,l -diphenylethylene develops an absorption band at 4340 A in the presence of boron trifluoride (and adventitious moisture) or of stannic chloride and hydrogen chloride. This band is characteristic of both the triphenylcarbonium ion and the diphenylmethylcarbonium ion. While similar observations on polymerizable monomers are precluded by intervention of polymerization before a sufficient concentration may be reached, similar ions should certainly be expected to form under the same conditions in styrene, and in certain other monomers also. In analogy with free radical polymerizations, the essential chain-propagating step may therefore be assumed to consist in the addition of monomer to a carbonium ion... 

S-b-MM was prepared according to the published procedures (4-6). Molecular weights in the desired range and with narrow, unimodal distibutions were obtained without resorting to extensive monomer purification (ljL) or capping of the styrene block with diphenylethylene (4,5,7-10). The S-b-MM contained about 10 mol% MM, and was conveniently characterized by 1H NMR and IR spectroscopy. 

Enantioselective carbenoid cyclopropanation can be expected to occur when either an olefin bearing a chiral substituent, or such a diazo compound or a chiral catalyst is present. Only the latter alternative has been widely applied in practice. All efficient chiral catalysts which are known at present are copper or cobalt(II) chelates, whereas palladium complexes 86) proved to be uneflective. The carbenoid reactions between alkyl diazoacetates and styrene or 1,1 -diphenylethylene (Scheme 27) are usually chosen to test the efficiency of a chiral catalyst. As will be seen in the following, the extent to which optical induction is brought about by enantioselection either at a prochiral olefin or at a prochiral carbenoid center, varies widely with the chiral catalyst used. 

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. 

Probably the largest body of systematic evidence concerning the occurrence of cationic and pseudocationic reactions is that of Evans and his co-workers [12-15]. It indicates that 1,1-diphenylethylene and its derivatives are very suitable for an exploration of the conditions under which these reaction modes may occur. It is worth noting that even for those systems, in which the dimerisation takes place in the absence of ions, these are formed at the end of the reaction this same behaviour is found in the pseudocationic polymerisation of styrene by perchloric acid [5]. 

Already, at an early stage of the studies on the captodative effect, Viehe s group (Lahousse et ai, 1984) measured relative rates for the addition of t-butoxyl radicals to 4,4 -disubstituted 1,1-diphenylethylenes and to substituted styrenes. This study did not reveal a special character of captodative-substituted olefins in such reactions. It might be that the stability of the radical to be formed does not influence the early transition state of the addition step. The rationalization of the kinetic studies mentioned above in terms of the FMO model indicates, indeed, an early transition state for these reactions, with the consequence that product properties should not influence the reactivity noticeably. 

Reetz et al. 16) were the first to recover and recycle a dendritic catalyst through a precipitation procedure. The dimethylpalladium complex of the phosphine-functionalized DAB-dendr-[N(CH2PPh2)2]i6 dendrimer (la) is an active catalyst for the Heck reaction of bromobenzene and styrene to give trara-stilbene (89% trans-stilbene and 11% 1,1-diphenylethylene, at a conversion of 85—90%, Scheme 8). 

The general characteristics of anionic copolymerization are very similar to those of cationic copolymerization. There is a tendency toward ideal behavior in most anionic copolymerizations. Steric effects give rise to an alternating tendency for certain comonomer pairs. Thus the styrene-p-methylstyrene pair shows ideal behavior with t = 5.3, fy = 0.18, r fy = 0.95, while the styrene-a-methylstyrene pair shows a tendency toward alternation with t — 35, r% = 0.003, i ii 2 — 0.11 [Bhattacharyya et al., 1963 Shima et al., 1962]. The steric effect of the additional substituent in the a-position hinders the addition of a-methylstyrene to a-methylstyrene anion. The tendency toward alternation is essentially complete in the copolymerizations of the sterically hindered monomers 1,1-diphenylethylene and trans-, 2-diphe-nylethylene with 1,3-butadiene, isoprene, and 2,3-dimethyl-l,3-butadiene [Yuki et al., 1964]. 

The complex participation model has been tested in the radical copolymerizations of 1,1-diphenylethylene-methyl acrylate, styrene-P-cyanoacrolein, vinyl acetate-hexafluoroace-tone, A-vinylcarbazole diethyl fumarate, A-vinylcarbazole funiaronitrile, maleic anhydride-vinyl acetate, styrene-maleic anhydride [Burke et al., 1994a,b, 1995 Cais et al., 1979 Coote and Davis, 2002 Coote et al., 1998 Dodgson and Ebdon, 1977 Fujimori and Craven, 1986 Georgiev and Zubov, 1978 Litt, 1971 Lift and Seiner, 1971 Yoshimura et al., 1978]. 

Naphthalene lithium (0.5 mmol) in THE is added quickly to a cooled (-78 °C) solution of styrene (5 g) in THE (50 ml).The mixture immediately turns orange. Stirring at -78 °C is continued for 30 min. A small sample may be taken from the mixture with a syringe and quenched in degassed methanol.This sample can be used to measure the molar mass of the styrene block (by GPC).The mixture is allowed to warm to -18 °C, then a solution of 1,1-diphenylethylene (108 mg, 0.6 mmol) in THE (1 ml) is added whereupon the... 

It is conceivable that a carbonyl compound with an n,n triplet energy lower than that of benzophenone could yield the photocycloaddition product in some of these cases. A reaction which may illustrate this point is the photocycloaddition of ethyl glyoxylate to styrene and 1,1-diphenylethylene.66 Unfortunately, the triplet energy of ethyl glyoxalate has not been measured however, there is adequate reason to believe it is lower than that of benzophenone (see Table VI). 

The structure-reactivity behavior found for similar organosodium polymerization initiators of styrene [27] or that for addition reactions with 1,1-diphenylethylene [28] is almost identical with that found for the lithium initiators of Table 3.1. It is interesting to note from Table 3.1 that the reactivity of lithium... 

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. 

---