Vinyl ethers bifunctional

Electron-rich bifunctional vinyl ethers (e.g. ethylene glycol divinyl ether) react with electron-poor alkenes (e.g. TCNE) to produce cyclobutanes in good yields via tetramethylene zwitterion intermediates. In some cases, cyclobutanes reacted with the solvent (MeCN) to yield tetrahydropyridines.9 Trifluoromethanesulfonimide is an... 

The synthesis, starting from a bifunctional initiator followed by quenching the double-headed living ends, gives homotelechelic polymers (method B). Carboxylate-capped telechelic poly(isobutyl vinyl ether) has been obtained in this way [82], where the adduct of a bifunctional vinyl ether with trifluoroacetic acid is the initiator, and the quencher is the malonate anion. For method C, a bifunctional trimethylsilyl enol ether, CH2=C[OSi(CH3)3]C6H4OCH2CH20C6H4[(CH3)3SiO]C=CH2, is a useful terminator (chain coupler) for vinyl ethers [142,147] and a-methyl-styrene [159] (see also Section VI.B.4). 

Such a synthesis is feasible in living cationic polymerization of vinyl ethers [208], For bifunctional vinyl ethers (20), a series of compounds are examined (Scheme 11), among which 20a turned out the best, probably due to the appropriate rigidity and length of the spacer. By adjusting reaction... 

Scheme 11 Synthesis of multiarmed polymers by the polymer-linking reaction with a bifunctional vinyl ether [208].

Because initiation of vinyl ethers with HI/I2 yields polymers with extremely narrow poly-dispersities," " bifunctional vinyl ethers can be used in combination with HI/I2 to polymerize vinyl ethers and produce a,co-diiodo telechelics (Scheme 39). This method has been used to produce telechelics from ethyl vinyl ether, methyl vinyl ether and hexadecyl (cetyl) vinyl ether. Treatment of the living poly(ethyl vinyl ether) with mono- and di-amines yields telechelics with amino end groups (Scheme 39, equation 41). More jecently, telechelic poly(vinyl ether)s with terminal malonate or carboxy groups were synthesized using both a functional initiator and a functional terminator according to Scheme 40." ... 

Amphiphilic Star-Shaped Block Copolymers By Reaction with Bifunctional Vinyl Ethers... 

Resctions with Alkenes and Aromatics. Unsymmetrically substituted olefins form head-to-head dimers selectively. We mention the classic vinylcarba-zole," vinyl ethers,indenes, and p-methoxystyrene. The regio-chemistry of the addition is compatible with a stepwise mechanism proceeding via a singly linked 1,4-bifunctional radical cation, in which spin and charge are separated (see above). Several dimerizations have quantum yields greater than... 

M. Sawamoto, T. Enoki, and T. Higashimura, End-functionalized polymers by living cationic polymerization. 1. Mono- and bifunctional poly(vinyl ethers) with terminal malonate or carboxyl groups, Macromolecules, 20(l) l-6, January 1987. 

Propenyl Ethers and Unsaturated Cyclic Ethers Propenyl ethers (CH3—CH=CH—OR R = ethyl, isobutyl, etc. cis- and trans-isomers) and 3,4-dihydrofuran are linear and cyclic a,/3-unsaturated ethers, that can be regarded as / -substituted vinyl ether derivatives. For these monomers a few controlled/living cationic polymerizations have been reported. The HI/I2 system is generally effective for both linear and cyclic monomers [181,182,183], whereas a recent study by Nuyken indicates that the IBVE-HI adduct coupled with nBu4NC104 is suited for 3,4-dihydrofuran (see Section V.A.4) [184]. A variety of mono- and bifunctional propenyl ethers can readily be prepared by the ruthenium complex-catalyzed isomerization of corresponding allyl ethers [185]. 

The development of living cationic polymerization systems for vinyl ethers also enabled the incorporation of functional end groups as well as the control of the polymer architecture. Telechelic polymers have been prepared based on bifunctional initiating systems [59, 50, 60] while... 

The free-radical copolymerization of electron-donor olefinic monomers, including commercial allyl and vinyl ethers, was quite frequently reported and studied during last years and seems to present interesting potentialities for the synthesis of new bio-sourced polymers. However the only publication devoted to donor-acceptor copolymerization of monomers from biomass was focused on the photopolymerization of divi-nylfumarate, a bifunctional monomer bearing both type of double... 

To obtain telechelic polymers—that are, those carrying a same reactive molecular group at each of their ends—the most direct method is to use bifunctional initiators. Examples of such initiators can be found for all living chain addition polymerizations the example shown below illustrates the bifunctional initiation of living cationic polymerization of vinyl ethers ... 

Cationic polymerization has also progressed considerably in the direction of controlled living polymerization. For example, advances have been made in the polymerization of isobutylene and vinyl ethers. These include controlled initiation processes, the use of ini-fers, binifers, trinifers, the preparation of bifunctional monomers, macromonomers, functional monomers and telechelic polymers based on isobutylene and the vinyl ethers. 

A new bifunctional H-bond directing dienamine organocatalyst has been designed to catalyse the 2 -l- 2-cycloaddition reaction of a, -unsaturated aldehydes and nitroethenes to yield cyclobutanes with four contiguous centres. The 2-1-2-cycloaddition of 1,2-bis(trifluoromethyl)ethene-l,2-dicarbonitrile with vinyl ethers produced cyclobutanes... 

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