Electrochemical vinylation

Gomes, R, Gosmini, C., Nedelec, J.-Y. and Perichon, J. (2002) Electrochemical vinylation of aryl and vinyl halides with acrylate esters catalyzed by cobalt bromide. Tetrahedron Lett., 43, 5901-3. 

Electrochemical Vinylation of Aryl Halides using Vinylic Acetates... 

This uses basically the same conditions, in the absence of 2,2 -bipyridine, as described previously for the electrochemical vinylation of aryl halides using vinylic acetates (Scheme 15.16) [28]. 

Conducting polymer composites have also been formed by co-electrodeposition of matrix polymer during electrochemical polymerization. Because both components of the composite are deposited simultaneously, a homogenous film is obtained. This technique has been utilized for both neutral thermoplastics such as poly(vinyl chloride) (159), as well as for a large variety of polyelectrolytes (64—68, 159—165). When the matrix polymer is a polyelectrolyte, it serves as the dopant species for the conducting polymer, so there is an intimate mixing of the polymer chains and the system can be appropriately termed a molecular composite. 

Electrochemical reduction of oxazolinium salts 36 gives the anions 37, which add efficiently to alkyl halides or, in the presence of McsSiCl, to methyl acrylate, methyl vinyl ketone, and acrylonitrile. Simple acid hydrolysis then gives the ketone products 38 and 39, and this method is quite general since the starting salts are readily prepared from carboxylic acids, R C02H (87TL4411). 

Corrosion has been encountered infrequently to date and has been a surface type, as opposed to pitting corrosion that can result in perforations. Entrapped air in the beverage or in the cans headspace increases the corrosive action of the product according to Koehler et at (21). As with beer and other canned foods, aluminum ends provide electrochemical protection when combined with tinplate or tin-free-steel can bodies. The level of iron pickup is reduced while the amount of aluminum dissolved in soft drinks increases without detrimental effect. Aluminum containers with vinyl epoxy and vinyl organosol coatings are compatible with carbonated soft drinks. 

Bipyridyl,4-methyl-4 -vinyl-electrochemical polymerization, 6,25 electropolymerization, 6,16 Bipyridyls bis(ZV-oxide) metal complexes, 2, 496 metai complexes, 2, 89, 90,93 steric effects, 2, 90 2,2 -Biquinolyl... 

Details of the conditions used in these reductions are discussed, especially the fact that this is apparently the first example in which the stereochemical aspects of an electrochemical desulphonylation reaction on a complex molecule have been examined. It is likely that further work will be profitable, given suitable substituents on a molecule, since sulphones (especially vinyl and aryl sulphones) should be good candidates for this type of reduction. 

Reactive radical ions, cations and anions are frequent intermediates in organic electrode reactions and they can serve as polymerization initiators, e.g. for vinylic polymerization. The idea of electrochemically induced polymerization of monomers has been occasionally pursued and the principle has in fact been demonstrated for a number of polymers But it appears that apart from special cases with anionic initiation the heterogeneous initiation is unfavorable and thus not competitive for the production of bulk polymers A further adverse effect is the coating of electrodes... 

With trifluoromethanesulfonic acid, all four vinyl groups are displaced at - 78°, to give a compound that was shown by Mossbauer spectroscopy to contain both Sn(II) and Sn(IV), and that was assigned the formula Sn [Sn (S03CF3)6]. Trivinyltin carboxylates have also been prepared from the reaction between tet avinyltin and mercury(I) carboxylates, which may be generated electrochemically in situ (185). 

The electrochemical reduction of 4//-thiopyrans bearing four electron-withdrawing substituents leads to 5,6-dihydro-2//-thiopyrans. Four diastereoisomers are produced, their relative proportions depending on the electrolytic conditions. Their conformations have been established using the vinylic proton as an nmr probe and confirmed in some instances by X-ray analysis <96JCS(P2)2623>. 

The syntheses and spectroscopic and electrochemical characterization of the rhodium and iridium porphyrin complexes (Por)IVI(R) and (Por)M(R)(L) have been summarized in three review articles.The classical syntheses involve Rh(Por)X with RLi or RMgBr, and [Rh(Por) with RX. In addition, reactions of the rhodium and iridium dimers have led to a wide variety of rhodium a-bonded complexes. For example, Rh(OEP)]2 reacts with benzyl bromide to give benzyl rhodium complexes, and with monosubstituted alkenes and alkynes to give a-alkyl and fT-vinyl products, respectively. More recent synthetic methods are summarized below. Although the development of iridium porphyrin chemistry has lagged behind that of rhodium, there have been few surprises and reactions of [IrfPorih and lr(Por)H parallel those of the rhodium congeners quite closely.Selected structural data for rr-bonded rhodium and iridium porphyrin complexes are collected in Table VI, and several examples are shown in Fig. 7. ... 

In contrast to the direct reduction as described above, the indirect electrochemical reduction of perfluoroalkyl halides is a versatile and novel method for generating perfluoroalkyl radicals selectively. Saveant et al. have demonstrated many successful examples. Using terephthalonitrile as a mediator, the indirect reduction of CF3Br in the presence of styrene leads to the dimer of the radical adduct obtained by the attack of CF on styrene. On the other hand, in the presence of butyl vinyl ether, the mediator reacts with the radical adduct obtained by the attack of CF3. on the olefin (Scheme 3.4) [14]. 

In 1990 we reported the synthesis of new redox-responsive crown ether molecules that contain a conjugated link between the crown ether unit and a ferrocene redox-active centre (Beer et al., 1990a). Examples of some of the species synthesized are shown in Fig. 5. The electrochemical behaviour of these species was investigated and also the electrochemical behaviour of their analogues with a saturated link between the ferrocene unit and the crown ether. The changes in the CVs of [2a] upon addition of magnesium cations are shown in Fig. 6. The metal cation-induced anodic shifts of [2a], [2b] and also their saturated analogue [3] and vinyl derivatives [4a], [4b] are shown in Table 1. 

The bis-benzo-15-crown-5 ferrocene compound [7] containing two vinylic linkages was formed in a mixture of three isomeric components, the cis-cis, cis-trans and trans-trans isomers, which proved inseparable. However, the precedent of insignificant differences found between the magnitudes of the metal cation-induced anodic shifts in the ferrocenyl redox potentials of the respective separated cis and trans isomers [2a] and [2b] led us to use the same isomeric mixture of [7] throughout the subsequent FABMS and electrochemical group 1 and 2 metal cation complexation experiments,... 

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