Dicyanovinyl group

Uncharged styryl (methine) disperse dyes were originally introduced to provide greenish yellow colours on cellulose acetate fibres. One such dye still in use is Cl Disperse Yellow 31 (6.226), which is made by condensing 4-(N-butyl-N-chloroethylamino)benzaldehyde with ethyl cyanoacetate. Suitable compounds for polyester usually contain the electron-accepting dicyanovinyl group, introduced with the aid of malononitrile. An increased molecular size leads to improved fastness to sublimation, as in the case of Cl Disperse Yellow 99 (6.227). A novel polymethine-type structure of great interest is present in Cl Disperse Blue 354 (6.228), which is claimed to be the most brilliant blue disperse dye currently available [85]. 

An analogous investigation was made [27] with donor-acceptor pairs such as those depicted in Fig. 7. The donor-acceptor pairs I-V presented in this figure are separated by various numbers, n, of similar chemical bonds, a so-called "n-bond system. The more electron-attracting group is the dicyanovinyl group. In ref. 27, the n-bond systems were investigated for n = 4, 6, 8, 10, 12. Pulse radiolysis experiments under conditions similar to... 

The irreversible wave at high cathodic potential (1, 5, 8, 9, 11) can be attributed to reduction processes of the dicyanovinyl group [7]. For the Fp-substituted compounds 1-4 all the oxidation steps display complete electrochemical irreversibility and can be related to the Fe-Si skeleton. Introduction of the Fp donor results in distinct lowering of the oxidation potentials (2-4 compared... 

Hutchings et al. also synthesized donor/acceptor-substituted bithiophenes and their measurement of the linear and non-linear optical properties corroborated by theoretical calculations confirm the results found by Effenberger et al. Thus e.g. bithiophene 441 substituted in the a,a -positions by a dimethylhydrazono and a dicyanovinyl group showed a bathochromic shift of the longest wavelength absorption, a slightly reduced dipole moment, and a hyperpolarizability... 

In most cases it is easy to rationalize the products obtained from vinyl azide reactions which do not involve the loss of molecular niaogen. For example, the substitution of the azido group by a nucleophilic reagent in the 2-azidovinyl ketone 73 (R = H) and the )3-dicyanovinyl... 

The impact of alkyl side chain substituents on conjugated pol5uners on the photovoltaic properties of bulk heterojimction solar cells has been studied extensively (128). However, their impact on small molecules has not received adequate attention. In order to assess the effect of side chains, a series of star-shaped molecules based on a triphenylamine core, bithiophene, and dicyanovinyl units deriva-tized with various alkyl end-capping groups of methyl, ethyl, hexyl and dodecyl have been S5mthesized. These molecules were studied to get structure-property relationships. 

More-extended Jt-electron systems than pNA have been also widely investigated. In styrene derivatives, those with an amino or methoxy group attached to the benzene ring and two cyano or cyano and alkoxycarbonyl groups attached to the vinyl part have been synthesized, and 2-(2,2-dicyanovinyl)anisol (DIVA) without strong absorption in the visible region was studied as a purple laser generation material. ... 

One of the first derivatives reported was an n-octyl substituted septithio-phene end-capped with dicyanovinyl functional groups (42). The synthesis of compound 42 is shown in Figure 5.26. The septithiophene core (7T) is grown from the inside out via a series of nickel-catalyzed Kumada... 

The energy difference (MP2/6-311G ) of 2- and 3-isomers of (l-hydroxy-2,2-dicyanovinyl)-l-methylpyrroles is 2.2 kcal/mol in favor of the 3-isomer [449]. One of the reasons of 2-isomer destabilization is a probable steric repulsion of the N-methyl group and functionalized vinyl substituent. High stability of 3-isomers is in agreement with decrease of their hydroxyl group acidity (by 0.5 un. pAT as compared to... 

Similar aminopyrrolizines have been obtained by substitution of the methylthio group in 2-(2,2-dicyano-l-methylthiovinyl)pyrrole with secondary amine and the subsequent cyclization of 2-(l-amino-2,2-dicyanovinyl)pyrrole 29 in the presence of tertiary amine [575]. 

The reaction of 2-(l-ethylthio-2-cyanovinyl)pyrroles with ethylhydrazine proceeds much slower (80% conversion of reagents is reached by boiling in methanol for 10 h) (Scheme 2.106). The predominant direction of the reaction of 2-(l-ethylthio-2,2-dicyanovinyl)pyrrole 27a is intramolecular cyclization into l-ethylthio-3-iminopyrrolizine 28a including the exchange of 1-ethylthio group for ethylhydrazine moiety. Ultimately, a mixture of pyrrolizine and pyrazole in 3 1 ratio is formed (48% overall yield). In the case of 2-(l-ethylthio-2-carbamoyl-2-cyanovinyl)pyrrole 27b on the contrary, the main reaction route is formation of pyrazole (pyrrolizine-pyrazole ratio is 1 2.5). 

The only pathway of the reaction of pyrrolizines bearing a nitrile group, 3-imino-2-pyrrolizinecarbonitriles, with hydroxylamine in methanol is the substitution of an ethylthio moiety for hydroxylamine to deliver l-hydroxylamino-3-imino-2-pyrro-lizinecarbonitriles (Scheme 2.119, Table 2.13) [582]. The latter are unstable in DMSO solutions and gradually transform to 2-(l-hydroxylamino-2,2-dicyanovinyl)pyrroles. 

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