Anionic additions

Cationic Polymerization. For decades cationic polymerization has been used commercially to polymerize isobutylene and alkyl vinyl ethers, which do not respond to free-radical or anionic addition (see Elastomers, synthetic-BUTYLRUBBEr). More recently, development has led to the point where living cationic chains can be made, with many of the advantages described above for anionic polymerization (27,28). 

Block copolymer—These copolymers are built of chemically dissimilar terminally connected segments. Block copolymers are generally prepared by sequential anionic addition or ring opening or step growth polymerization. 

O Nucleophilic addition of hydroxide ion to the CN triple bond gives an imine anion addition product. 

In aqueous solutions diazonium salts produce products corresponding to anion addition to an intermediate carbonium ion ... 

Calcium-selective ionophore ETH 1001 Lipophilic anionic additive potassium... 

An efficient preparation of hexahydro-isoxazolo[2,3- ]pyridin-2-ones relies on the anionic addition of nucleophiles at the electrophilic carbon of the nitrone followed by cyclization of the resulting Ar-oxide. As shown by results collected in Scheme 31, various nucleophiles can be engaged in the reaction and include enolates 95 <20020L3119> or 98 <2000BML1811>, silyl acetals 101 <2003TL2817>, or ynolates 103 <20020L3119> (Scheme 31). 

The above results concerning the fractal dimension as functions of the solution temperature, the CPE exponent, and the depression parameter are demonstrated again in their other investigation of the effect of the anion addition on pit morphology of Inconel alloy 600 at elevated temperatures.54... 

The early, independent work of Starks, Markosa and Brandstrom from ca. 1965-1969, brought into focus with Starks classical paper in 1971, showed PTC to be potent and versatile synthetic tool.[1-4] Since that time, the well-documented investigations of PTC have been massive and vigorous.[5-7] In polymer chemistry PTC was effectively exploited first in anionic addition polymerization and more recently has been extended to condensation polymerization.[5,8-9] However, until a very few years ago, the use of solid-liquid PTC systems in polycondensation has for the most part escaped this intensive scrutiny. Consequently, some time ago we began a rather broad study into the use of solid-liquid PTC to effect polycondensations.[10]... 

The addition of strong nucleophile to reactive electrophile gives a relatively stable anionic addition intermediate with a lifetime long enough to diffuse through the solution and abstract a proton before it reverts to reactants (k > k i) (Scheme 2.2). 

Spontaneous polymerization of 4-vinyl pyridine in the presence of polyacids was one of the earliest cases of template polymerization studied. Vinyl pyridine polymerizes without an additional initiator in the presence of both low molecular weight acids and polyacids such as poly(acrylic acid), poly(methacrylic acid), polyCvinyl phosphonic acid), or poly(styrene sulfonic acid). The polyacids, in comparison with low molecular weight acids, support much higher initial rates of polymerization and lead to different kinetic equations. The authors suggested that the reaction was initiated by zwitterions. The chain reaction mechanism includes anion addition to activated double bonds of quaternary salt molecules of 4-vinylpyridine, then propagation in the activated center, and termination of the growing center by protonization. The proposed structure of the product, obtained in the case of poly(acrylic acid), used as a template is ... 

Intramolecular 1,3-dipolar additions of nitrones and nitrile oxides to carbohydrate alkene groups have met with success. Thus, treatment of the unsaturated heptose ether 68 (Scheme 17), which can be made following 1,3-dithianyl anion addition to C-l of 2,3,4-tri-0-benzyl-5,6-dideoxy-D-xy/o-hex-5-enose, with IV-methylhydroxylamine in refluxing methanol, affords the nitrone 69 that cyclizes to give the bicyclic isoxazolidine 70 (60% isolated) together with the epimer at the new asymmetric center carrying the methylene carbon atom (16% isolated) [35]. 

Cationic polymerization has been used commercially to polymerize isobutylene and alkyl vinyl ethers, which do not respond to free-radical or anionic addition. See also Elastomers and Rubber (Synthetic). 

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