Vinylic carbon function

The relative ease of the cyclization step from A to C may also be linked to the nucleophilic or coordinative ability of the heteroatom bound to the metal. The reaction of 7 with diphenylacetylene (Ph2C2) leads to the seven-membered derivatives 68 and 69 after prior isolation of the monoinsertion product 24, treatment with a silver salt, followed by the usual thermolytic conditions. This is another rare example of an intramolecular formation of a C-S bond within the coordination sphere of a transition metal and a novel, albeit limited to one alkyne, route to the rare family of dibenzo[bd] thiepins. With the closely related 8, which differs from 7 only by the tertiary amine unit in the metallacyclic framework instead of a thioether function, a carbocyclic product 71 is obtained (see under carbocycle reactions, next section). The formation of the seven-membered S-heterocycles is attributed to the good coordinative ability of the thioether group in 7. The S-atom remains close to the vinylic carbon function before the cyclization. With the poorly coordinating, readily displaced amine function in 8, the N-atom is detached from the metal and ultimately affords a spirocyclic product (see Scheme 18). 

PureVision is a copolymer of tris-(trimethylsiloxy)-silyl-propylvinyl carbamate (TRIS-VC), N-vinylpyrrolidone, a vinyl carbonate functional polydimethylsiloxane (PDMS) macromer, and a vinyl carbamate derivative of alanine. Eor more information, see Nicolson, P. C. Vogt, J. Biomaterials 2001, 22, 3273. 

Much less has been done with the functionalized halides than with the functionalized olefins. The only two-carbon compound in this group is vinyl bromide (or iodide). This is a very useful reactant with secondary amines because terminal allylic amines are usually major or exclusive products. We have used this halide for synthesizing the pheromone of the Red Bollworm Moth, 9,11-docecadien-l-ol as follows (9). Of the four three-carbon functionalized vinylic halides listed,... 

Nucleophilic vinylic substitutions of 4//-pyran-4-onc and 2,6-dimethyl-4//-pyran-4-one with a hydroxide ion in aqueous solution were calculated by the density functional theory (B3LYP) and ab initio (MP2) methods using the 6-31+G(d) and 6-31G (d) basis sets. The aqueous solution was modelled by a supermolecular approach, where 11 water molecules were involved in the reaction system. The calculations confirmed a different addition-elimination mechanism of the reaction compared with that in the gas phase or non-polar solution. Addition of OH- at the C(2) vinylic carbon of the pyranone ring with an activation barrier of 10-11 kcalmol-1 (B3LYP) has been identified as the rate-determining step, in good quantitative and qualitative agreement with experimental kinetics. Solvent effects increase the activation barrier of the addition step and, conversely, decrease the barrier of the elimination step.138... 

When (Z)-(j5-fluoro-j5-trifluoromethylvinyl)phenyliodonium triflate is mixed with sodium phenoxide or sodium 2-phenylethoxide in dichloromethane, substitution is directed to the jft-carbon atom of the vinyl ligand, while the iodonium function remains intact (equation 200)136. With the 4-ter/-butylbenzenethiolate ion, however, substitution occurs at both vinyl carbon atoms (equation 201)136. 

Similarly, DD-Na lead to macromonomer by reaction with a variety of chlo-rosilanes bearing carbon-functional groups (Fig. 3). The substituent R on silicon is exemplified with hydroxyl, amino, epoxy, carboxyl, or vinyl functional group. 

The mechanism proposed by Ddtz involves the insertion of a carbon monoxide into the vinyl carbene complex intermediate with the formation of the vinyl ketene complex (255). Electrocyclic ring closure of (255) leads to the cyclohexadienone complex (252), which is related to the final tenzannulation product by a tautomerizadon when R is hydrogen. The mechanism proposed by Casey differs from that of Ddtz in that the order of the steps involving carbon monoxide insertion and cyclization to the aryl or alkenyl substiment is reversed. < Specifically, the vinyl carbene complex intermediate (248) first undergoes cyclization to the metallacyclohexadiene (249), followed by cartion monoxide insertion to give the intermediate (251), and finally reductive elimination to give cyclohexadienone intermediate (252). At this time the circumstantial evidence favors the intermediacy of vinyl ketene intermediates since they can be trapped from these reactions and isolated where the metal is dispaced from the vinyl ketene functionality however, there is not any evidence which can rule out the alternative mechanism. 

Appropriate quenching of a reductively formed lithium enolate with a carboxylic acid anhydride, chloride, methyl chloroformate or diethyl phosphorochloridate yields the corresponding enol esters, enol carbonates or enol phosphates. These derivatives may be transformed into specific alkenes via reductive cleavage of the vinyl oxygen function, as illustrated by the example in Scheme 8. 

Thiols add to alkenes under photochemical conditions to form thioethers, and the reaction can be done intramolecularly to give cyclic thioethers. Thiols also add to alkynes and with a palladium catalyst, vinyl sulfides can be formed. Thio-carbonates function as thiol surrogates, converting alkenes to alkyl thiol in the presence of TiCl4 and CuO. °... 

Alkenes substituted by two or more different functional groups joined to vinylic carbons or to carbon atoms remote from the double bond undergo addition of dibromocarbene to form 1,1-dibromocyclopropanes some examples are given in Table 33. 

Polymers with pendant cyclic carbonate functionality were synthesized via the free radical copolymerization of vinyl ethylene carbonate (4-ethenyl-l,3-dioxolane-2-one, VEC) with other imsaturated monomers. Both solution and emulsion free radical processes were used. In solution copolymerizations, it was found that VEC copolymerizes completely with vinyl ester monomers over a wide compositional range. Conversions of monomer to polymer are quantitative with complete incorporation of VEC into the copolymers. Cyclic carbonate functional latex polymers were prepared by the emulsion copolymerization of VEC with vinyl acetate and butyl acrylate. VEC incorporation was quantitative and did not affect the stability of the latex. When copolymerized with acrylic monomers, however, VEC is not completely incorporated into the copolymer. Sufficient levels can be incorporated to provide adequate cyclic carbonate functionality for subsequent reaction and crosslinking. The unincorporated VEC can be removed using a thin film evaporator. The Tg of VEC copolymers can be modeled over the compositional range studied using either linear or Fox models with extrapolated values of the Tg of VEC homopolymer. 

Limited information exists in the literature, however, on the homo- or copolymerization of vinyl ethylene carbonate, 1 (VEC or 4-ethenyl-l,3-dioxolane-2-one) for the preparation of cyclic carbonate functional polymers. A few comments regarding polymerization of VEC are given in an early patent [9], In the only reported study of the copolymerization behavior of VEC, Asahara, Seno, and Imai described the copolymerization of VEC with vinyl acetate, styrene, and maleic anhydride and determined reactivity ratios [10. Their results indicated that VEC would copolymerize well with vinyl acetate, but in copolymerizations with styrene, little VEC could be incorporated into the copolymer. VEC appeared to copolymerize with maleic anhydride, however the compositions of the copolymers was not reported. Our goal was to further explore the use of VEC in the synthesis of cyclic carbonate functional polymers. 

VEC copolymerizes well with vinyl ester monomers over a range of compositions. To a more limited extent, VEC can also be incorporated into acrylic copolymers, however, we have not achieved quantitative incorporation. In the presence of styrene, essentially no VEC is incorporated into the copolymer. VEC can also be easily incorporated into a vinyl acetate/butyl acrylate latex, yielding a latex polymer containing cyclic carbonate functionality. The Tg of the copolymers can be modeled using extrapolated values for the Tg of a VEC homopolymer. 

The Heck reaction, a palladium-catalyzed vinylic substitution, is conducted with olefins organohalides or pseudohalides are frequently used as organopalladium precursors [143]. One of the strengths of the method is that it enables direct mono-functionalization of a vinylic carbon, which is difficult to achieve by other means. The Heck arylation in Scheme 15.74, reported in 1996, was the first example of a microwave-promoted, palladium-catalyzed C-C bond formation [18]. The power... 

W. Wang, Y. Li, and Y.P. Sun, Poly(N-vinyl carbazole)-functionalized single-waUed carbon nanotubes Synthesis, characterization, and nanocomposite thin films. Polymer, 46, 8634-8640 (2005). 

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