Vinyl, alkylation

BAYLIS - HILLMAN Vinyl alkylation Amine catalyzed converelon of acrylates to a-(hydroxyalkyl) acrylates or of vinyl ketones to a-(hydroxyalkyO vinyl ketones. 

The poly(vinyl ethers), whieh were first made available in Germany before 1940, are not of importance in the plastics industry but have applications in adhesives, surfaee coatings and rubber technology. Of the many vinyl ether polymers prepared, only those from the vinyl alkyl ethers and some halogenated variants are of interest. Two methods of monomer preparations may be used. 

The vinyl alkyl ethers polymerise violently in the presence of small quantities of inorganic acids. 

Cyclic ethers Vinyl alkyl ethers jV-alkylacetamides Isothiocyanates Aliphatic nitriles... 

Durch Pyrolyse der aus Zimtaldehyd oder den (2-Aryl-vinyl)-alkyl- bzw. -aryl-ketonen mit Lithiumalanat erhaltlichen Komplexe werden Phenyl-cyclopropane erhalten (vgl. S. 173 u. 219). Als Nebenprodukte bilden sich gesattigte und ungesattigte offenkettige Kohlenwasserstoffe. 

Vinylic tellurides (generalprocedure) Elemental Te (0.6 g, 5.0 mmol) is added to a solution of the vinylic magnesium bromide (5.5 mmol) in THE (10 mL) under reflux and N2 atmosphere, and the reflux maintained for 20 min. The mixture is allowed to reach room temperature and then treated with n-butyl bromide (0.7 g, 5.0 mmol). After stirring for 10 min, the reaction mixture is cooled at 0°C, treated dropwise with saturated aqueous NH4CI, extracted with ether, dried (MgS04) and then evaporated. Kiigelrohr distillation of the residue under vacuum gives the vinyl alkyl tellurides as yellow liquids. 

The cationic polymerization of vinyl isobutyl ether at —40°C produces stereoregular polymers (structure 5.21). The carbocations of vinyl alkyl ethers are stabilized by the delocalization of p valence electrons in the oxygen atom, and thus these monomers are readily polymerized by cationic initiators. Poly(vinyl isobutyl ether) has a low Tg because of the steric hindrance offered by the isobutyl group. It is used as an adhesive and an impregnating resin. 

Similarly comb-like copolymers of vinyl pyrollidone and vinyl alkyl amines were shown [446] to influence the permeability of negatively charged phospholipid liposomes containing encapsulated carboxyfluorescein. At a pH of approximately 7, the copolymers allowed permeability and solute release due to polymer/liposome complex formation and disruption of the phospholipid membrane. 

This is also true of vinyl alkyl ethers. Thus the Tg of polyethyl vinyl ether is lower (244 K) than the Tg of polymethyl vinyl ether (263 K). However, branched alkyl groups increase the Tg, mainly through imparted steric restrictions. Hence the Tg values of polyvinyl -butyl ether, polyvinyl isobutyl ether, and polyvinyl /er/-butyl ether are 221, 255, and 361 K, respectively. 

Trifluoromethylation is the most important perfluoroalkylation reaction. Kobayashi and co-workers reported the trifluoromethylation of aryl, vinyl, alkyl halides with trifluoromethyl iodide in the presence of copper powder in aprotic solvents such as HMPA at 120-150 °C [83,84], and this methodology has been applied to the preparation of fluorinated pyrimidine and purine nucleosides [85,86] (Scheme 27). 

According to most sources, the homopolymer of the vinyl alkyl ethers react to ionizing radiation predominantly by cross-linking 18). It is safe to conclude that maleic anhydride has contributed a predominance of chain scissioning to the copolymer and that, if cross-linking does take place, it is in very small proportion. 

H.P. Siebel and H.-W. Otto, Styrene- acrylonitrile copolymers blended with graft copolymers of styrene onto butadiene-alkyl acrylate-vinyl alkyl ether terpolymers, US Patent 3280219, assigned to BASF AG, October 18,1966. 

The processing properties of poly(vinyl chloride) has been improved by copolymerizing vinyl chloride with a small amount of vinyl alkyl ether. Copolymers of vinyl alkyl ethers and maleic anhydride arc used as water soluble thickeners, paper additives, textile assistants and in cleaning formulations. 

Our recent synthetic examinations have confirmed the non-metallacarbene mechanism for Ru-H and Ru-Si complex catalyzed reactions of vinyl alkyl ethers with vinylsilanes,yielding a mixture of ( +Z)-l-silyl-2-(alkoxy)ethenes (Eq. 32). Interestingly, l-silyl-l-(alkoxy)ethene has not been found among the products [51]. 

Acetyl-ethyl- -ethylester E2, 193 1,3-Alkadienyl- E2, 144 1,2-Alkadienyl- - 2-alkinylester E2, 198 (2-A koxycarbonyl-vinyl)-alkyl- -alkylester E2,... 

Siggia, S. and Edsberg, R. L. (1948) Iodometric determination of vinyl alkyl ether, Anal. Chem. 20, 762-763. 

At the end of the nineteenth century, A. F. Favorskil and his students were studying catalytic conversions of acetylene, including those occurring in the presence of alcoholic potash. His students have continued this series with work on vinylation, hydrolysis of some of the vinyl alkyl ethers (M. F. Shostakovskil), and conversions of vinylethynylcarbinols (I. N. Nazarov). 

Shostakovskil has published research on the synthesis and utilization of vinyl alkyl ethers. Hydrolysis of these ethers to acetaldehyde is probably commercially used today in the U.S.S.R. (290). Other practical utilizations of this class of compounds have been indicated (106,107,108,-176,185,207,283,368). Shostakovskil found that a variety of acid... 

The work of Nazarov on vinyl ethynyl carbinols involves condensation of vinylacetylene with ketones in the presence of caustic potash and also their conversions, many of which are catalytic in nature. A review of his work involving polymerization, isomerization, hydrogenation, and other conversions was published by him (252). Hydration of divinylacetylenes in methanol solution in the presence of mercuric sulfate and sulfuric acid gave vinyl alkyl ketones. These can be reacted with hydrogen sulfide, amines, etc., to yield heterocyclic compounds. Substituted vinyl alkyl ketones underwent spontaneous cyclization to cyclopentenones. Nazarov summarized a decade of this research in this field in 1951 (253). His general review of organic syntheses based on acetylene is also of interest in this connection (254). 

Use of triphenylmethyl and cycloheptatrienyl cations as initiators for cationic polymerization provides a convenient method for estimating the absolute reactivity of free ions and ion pairs as propagating intermediates. Mechanisms for the polymerization of vinyl alkyl ethers, N-vinylcarbazole, and tetrahydrofuran, initiated by these reagents, are discussed in detail. Free ions are shown to be much more reactive than ion pairs in most cases, but for hydride abstraction from THF, triphenylmethyl cation is less reactive than its ion pair with hexachlorantimonate ion. Propagation rate coefficients (kP/) for free ion polymerization of isobutyl vinyl ether and N-vinylcarbazole have been determined in CH2Cl2, and for the latter monomer the value of kp is 10s times greater than that for the corresponding free radical polymerization. 

Trityl ion effectively initiates polymerization of olefins having strongly electron-releasing substituents, especially vinyl alkyl ethers (2, 16),... 

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