1.3- Dioxolane styrene

Homochiral pyridyl, bipyridyl, and phosphino derivatives of 2,2-dimethyl-1,3-dioxolane (113)-(115) were prepared from T-(+)-tartrate. These compounds were assessed in metal-catalyzed asymmetric hydroformylation of styrene enantioselectivity was generally low.342... 

Experiment [20], however, shows that when a great excess of styrene is used, sequences of up to four styrene units can be formed, although the formation of styrene sequences is under all conditions much less probable than the formation of dioxolan sequences. Thus both reaction mechanisms require a reaction step such as (F) whereby sequences of styrene units can be formed ... 

The remarkably high molecular weights of copolymers of dioxolan and styrene, which were achieved by Yamashita, are also easily intelligible in terms of the insertion mechanisms shown in schemes (D) and (E) the fact that cationically produced polystyrenes have low molecular weights is mainly due to proton transfer to monomer from the P-carbon at the growing end of a chain. If there is no growing end but a cyclic oxonium ion, this reaction cannot occur, and thus the principal chainbreaking reaction is frustrated. 

Very interesting results were published in respect of application of copolymers of 4-methylene-2-phenyl-2-(4-vinylphenyl)-l,3 dioxolane with styrene as a template ... 

Type II (slow homodimerization) Styrene, allylstannanes" Styrene, 2° allylic alcohols, vinyl dioxolanes, vinyl boronates Styrenes (large ortho substit.) " " 2° allylic alcohols, vinyl epoxides, unprotected 3° allylic alcohols, acrylates, acrylamides, acrylic acid, acrolein, vinyl ketones, vinyl boronates perfluorinated alkane olefins ... 

The terpolymer of the radical ring-opening polymerization monomer, 5-methyl-ene-2-phenyl-l,3-dioxolan-4-one, (I), with styrene, and methyl methacrylate was also prepared. 

Cationic [5 + 2]cycloaddition involving a styrene and p-benzoquinone ketals in the presence of a Lewis acid is the key reaction to a number of neolignans fe nin [187]. The oxygen atoms of the dioxolane function in the cycloaddend rrinforce the a character of their neighboring carbons, and this character is transmitted to the termini which participate in the C-C bond formations. 

Insoluble styrene-divinylbenzene copolymer containing (4R, 5R)-2-[p-phenyl-4,5-bis(5-H-dibenzophosphol-5-ylmethyl)]-l,3-dioxolane groups (J. K. Stille, personal communication) ... 

Rakova and Korotkov compared the rates of homopolymerization and copolymerization of styrene and butadiene [226], Styrene polymerizes very rapidly and butadiene slowly. Their copolymerization is slow at first, with preferential consumption of butadiene. When most of the butadiene is consumed, the reaction gradually accelerates yielding a product with a high styrene content. In the authors opinion, this is caused by selective solvation of the active centres by butadiene only after butadiene has polymerized, does styrene gain access to the centres [227], A similar behaviour was observed by Medvedev and his co-workes [228] and by many others. In our laboratory we observed this kind of behaviour in the cationic polymerization of trioxane with dioxolane. Although trioxane is polymerized much more rapidly than dioxolane, their copolymerization starts slowly, and is accelerated with progressing depletion of dioxolane from the monomer mixture [229],... 

Some heterocyclic monomers may undergo random copolymerization with vinyl monomers. This is a case of cyclic acetals (e.g., 1,3-dioxolane) which forms the random copolymers with styrene [308,309] or isoprene [310], Apparently, the oxycarbenium ions, being in equilibrium with tertiary oxonium ions (cf., Section II.B.6.b), are reactive enough to add styrene ... 

When the reaction is carried out in pure alcohol, the corresponding acetal is formed. Styrene was converted to the cyclic acetal of phenylacetaldehyde in 90% yield in ethylene glycol, whereas a mixture of products was obtain in ethanol. Interestingly, acrylonitrile was oxidized to l,3-dioxolan-2-ylacetoni-trile (1) in ethylene glycol (equation 2). - 2,2-Dimethoxypropionitrile was obtained in methanol. - Methyl acrylate behaves similarly. 

Anhydrous RuCb catalyzes the reaction of epoxides with acetone (in acetone under reflux, 1.5-5 h) to give 1,3-dioxolanes [64]. The same catalyst, in the presence of ammonium thiocyanate, converts epoxides into thiiranes. The reaction takes place with inversion of configuration (R)-(-r)-styrene oxide was converted into (5)-(-)-sty-rene sulfide of 78 % optical purity [65]. This transformation is also mediated by catalytic amounts (2 %) of an Fe(III) pentafluorophenylporphyrin complex [66]. Chloro-hydrins are formed on treatment of epoxides with stoichiometric amounts of FeCl3 in ether [67]. 

Mg-Al oxides with a Mg/Al ratio of 5, calcined at 400 °C, are the most active catalysts for the reaction of CO2 and styrene oxide, and DMF is the best solvent. Using this Mg-Al oxide, various kinds of epoxides could be quantitatively converted into the corresponding cyclic carbonates. This addition reaction proceeds with retention of the stereochemistry of epoxides the reaction of CO2 with (R)- and (S j-benzyl glycidyl ether gave and ( Sj-4-(benzyloxymethyl)-l,3-dioxolane-2-one with >99% e.e., respectively. 

L. W. Zatorskil, P. T. Wierzchowski, Zeolite-catalyzed synthesis of 4-phenyl-l,3-dioxolanes from styrene oxide, Catal. Lett. 10 (1991) 211. 

Since the 4-phenyl-2-methylene-l,3-dioxolane (XXl) underwent much more extensive ring opening than did the unsubstituted 2-methylene-l,3-dioxolane (I), it was reeisoned that a benzyl ketene acetal would be a more effective chain transfer agent than diethyl ketene acetal. Thus vhen methyl benzyl ketene acetal was used with styrene, a complete addition-elimination occurred to produce an oligomer of styrene. 

The extruder can be used for a variety of polymerizations even if no preformed polymer is present.89 These include the continuous anionic polymerization of caprolactam to produce nylon 6,90 anionic polymerization of capro-lactone 91 anionic polymerization of styrene 92 cationic copolymerization of 1,3-dioxolane and methylal 93 free radical polymerization of methyl methacrylate 94 addition of ammonia to maleic anhydride to form poly(succin-imide) 95 and preparation of an acrylated polyurethane from polycaprolactone, 4,4 -methylenebis(phenyl isocyanate), and 2-hydroxyethyl acrylate.96 The technique of reaction injection molding to prepare molded parts is slightly different. Polyurethanes can be made this way by... 

Asymmetric induction in the palladium-catalyzed hydroesterification of z-methylstyrene, styrene and other alkenes in the presence of ligands with rigid 5//-dibenzophospholyl units linked to chiral cyclobutane, dioxolane or cyclohexane skeletons (CBDBP, DIPHOL, CHDBP) is compared with the effect of the analogous diphenylphosphane ligands18 23. 

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