Ethyl Vinyl Ether photochemical

The chemical sensitization effect was 0.006 (calculated from the quantum yield of the photochemical transformation of 130 to 131, the yield of 131 obtained with the oxalate/hydrogen peroxide reaction, and the moles of oxalate employed). Higher chemical sensitization efficiencies (about 0.04) were observed when the oxalate/hydrogen-peroxide system was used in the addition of ethyl vinyl ether onto phenanthrene quinone... 

The 1,4- and 1,5-benzothiazepines (421) and (423) have been prepared by the photochemical reactions of the benzoisothiazole (420) and the benzothiazole (422) respectively with ethyl vinyl ether (81TL529, 2081). The mechanisms of these reactions are not fully established but it is interesting to note that the reactions of (422) with cis- and trans-but-2-ene are stereospecific. 

This article reports on the synthesis of photosensitive polymers with pendant cinnamic ester moieties and suitable photosensitizer groups by cationic copolymerizations of 2-(cinnamoyloxy)ethyl vinyl ether (CEVE) (12) with other vinyl ethers containing photosensitizer groups, and by cationic polymerization of 2-chloroethyl vinyl ether (CVE) followed by substitution reactions of the resulting poly (2-chloroethyl vinyl ether) (PCVE) with salts of photosensitizer compounds and potassium cinnamate using a phase transfer catalyst in an aprotic polar solvent. The photochemical reactivity of the obtained polymers was also investigated. 

Carbonyl ylides (155), generated photochemically from the corresponding a,p-unsaturated, y,5-epoxy dinitriles, undergo regioselective 1,3-dipolar cycloaddition with ethyl vinyl ether, leading predominantly to the exo-adduct. The very low reactivity of seven-membered ring ylides (155) is rationalised by AMI calculations which show the ylide reactivity to depend on the LUMO energy and on the Cy.Cs separation. 

BFj-etherate in methylene chloride added to a soln. of 2,3 4,5-di-O-isopropylidene-aldehyde-D-arabinose and ethyl vinyl ether in the same solvent at —78° under argon, after 10 min the mixture treated with triethylamine, and warmed to room temp. - trans-product. Y 98%. Although yields and diastereofacial selectivities are substrate-dependent, the method surpasses photochemical [22]-cycloaddition in regio- and stereo-selectivity, and there is no racemization in the chiral residue. F.e. incl. chiral 2-arylthiooxetanes and cycloaddition to 1,1-disubst. olefins s. H. Sugimura, K. Osu-mi. Tetrahedron Letters 30, 1571-4 (1989) 2-a-silyloxetanes from 2-ethylenesilanes s. ibid. 29, 4953-6 (1988). 

The rearrangement of 2-ethoxyethylidene, generated photochemically from a non-nitrogenous precursor, leads to ethyl vinyl ether deuterium labelling demonstrated an exclusive preference for hydrogen migration (Scheme 68). ... 

Also itermolecular photochemical [2+2] cycloaddition based on 2-trifluoromethylquinazoline 1286 was studied. In a similar conditions the reaction with ethylene gives compound 1287 in 17 % yield as a sole product probably due to low solubility of ethylene in methanol. Ene-type product 1288 was isolated in 65 % yield when isobutylene was used in the reaction, showing that biradical intermediate is involved in the transformation. In a case of ethyl vinyl ether acetal 1292 was formed as product of methanolysis of intermediate azetidine 1289. Similarly was used intermediate azetidine 1290 was not isolated when dichloroethylene and its formation was proved by isolation of methanolysis product 1293 in 89 % yield. It should be noted, that treatment of product 1288 with base leads to elimination of CFs-group as in a case of 1284 (Scheme 298) [797]... 

The same group of Japanese authors studied the photochemical reaction of fluorinated quinoxalines. Photochemical cycloadditions with quinoxaline derivative 1294 occurred and C=N double of the diazine ring, leading to the formation of azetidine derivatives (Scheme 299). The presence of trifluoromethyl group in the molecule of 1294 activated the substrate towards cycloaddion, so that even electron-deficient methyl methacrylate was introdnced in the reaction [797], In the case of ethyl vinyl ether as the alkene, the addnct 1296 also as in a case with 1289 was not stable and underwent azetidine ring-opening npon action of the solvent. Ketene was also successfully introduced in [2+2] cycloaddition with trifiuoromethyl-substituted quinoxaline derivatives [797]... 

Synthesis by Selective Cationic Pofymerization of 2>(3 Phenyl-2 -norltornadiene>2-carl)onylo gr)ethyl Vinyl Ether and Photochemical Reaction of the Resulting Pofymers... 

Nishikubo, T., Kameyama, A., Kishi, K., Kawashima, T., Fujiwara, T., and Hijikata, C., Synthesis of new photoresponsive polymers bearing norbomadiene moieties by selective cationic polymerization of 2- [ [ (3-phenyl-2,5-norbomadienyl)-2-carbonyl] oxy] ethyl vinyl ether and photochemical reaction of the resulting polymers. Macromolecules, 25,4469-4475,1992. 

Other methods that have been less regularly used are the dehydration of alcohols with dimethyl sulfoxide to form symmetrical ethers, the photochemical transformation of benzylic chlorides with fert-butyl alcohol, or radical reactions of hcxafluoroacetone with alkanes, Mercury acetate promoted couplings of alcohols with vinyl acetate or vinyl ethyl ether to form vinyl... 

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