Hydrogenation dicyanobenzene

Radical cations can be formed by irradiation of unsubstttuted aromatic hydrocarbons such as naphthalene, and this makes possible the photochemical displacement of hydride ion by a nucleophile such ascyanide f3.10). Oxygen is not necessary for the success of this type of reaction if a good electron-acceptor is present, such as p-dicyanobenzene (3.11), which enhances the initial photoionization and also provides for reaction with the displaced hydrogen. 

A subsequent study ° from the Arnold group showed an intriguing stereoelectronic effect in oxidative benzylic carbon-hydrogen bond cleavage reactions of substrates 8 and 9 (Scheme 3.7). In this study, electron transfer reactions were conducted in the presence of a nonnucleophilic base. Radical cation formation also weakens benzylic carbon-hydrogen bonds, thereby enhancing their acidity. Deprotonation of benzylic hydrogens yields benzylic radicals that can be reduced by the radical anion of dicyanobenzene to form benzylic anions that will be protonated by solvent. This sequence of oxidation, deprotonation, reduction, and protonation provides a sequence by which epimerization can be effected at the benzylic center. In this study, tram isomer 10 showed no propensity to isomerize to cis isomer 11 (equation 1 in Scheme 3.7), but 11 readily converted to 10 (equation 2 in Scheme 3.7). The reactions were repeated in deuterated solvents to assure that these observations resulted from kinetic rather than thermodynamic factors. Trans isomer 9 showed no incorporation of deuterium (equation 3 in Scheme 3.7) whereas cis isomer 11 showed complete deuterium incorporation. The authors attributed this difference in reactivity to... 

Monomers. Diethyl terephthalimidate was prepared by mixing 7.68 g ( 0.06 mole ) of 1,4-dicyanobenzene with 9 ml absolute ethyl alcohol and 330 ml anhydrous 1,4-dioxane and by passing dry hydrogen chloride gas into the solution at 0-5 C until saturation. Then the reaction vessel was closed, and maintained at this temperature for 5 days to insure completion of reaction. The resulting white solid was filtered, washed and air-dried to yield 15.5 g ( 90% yield ) of diethyl terephthalimidate dihydrochloride. 

Benzyl phenyl sulphide, norbornene, cw-cyclooctene, and 4-vinyl-1-cyclohexene were obtained from Aldrich and (IS)-(-)-a-pinene from Fluka. Phenyl sulphide was prepared from benzene and sulphur chloride following the literature procedure[9]. Reference samples of sulphoxides and sulphones were prepared by oxidation of sulphides with sodium periodate[10] and hydrogen peroxide[ll] respectively. Reference samples of epoxides were made by following Kaneda et al.[ 2 procedure. Metal phthalocyanines[13] were prepared from appropriate metal salt, 1,2-dicyanobenzene with ammonium molybdate as catalyst and were characterized by elemental analysis. 

Photocyanation of aromatic compounds is dealt with in several papers this year. In the presence of an electron acceptor such as p-dicyanobenzene, aromatic hydrocarbons such as naphthalene (81), substituted naphthalenes, phenanthrene, or anthracene give mixtures of products on irradiation with sodium cyanide. The major products involve substitution of hydrogen by cyanide or addition of hydrogen cyanide to the aromatic hydrocarbon. When oxygen is present, the product mixture is less complex, and a good yield of cyano-substituted compound is obtained. It is proposed that the aromatic radical cation is involved in the... 

The phenanthridine ring of 45 is constmcted via a hydrogen bond-controlled enamide photocyclization. Alkyation of the enamide nitrogen is necessary, otherwise, the substrate decomposes <97SL547>. Spirocyclohexylisoquinolines are obtained photochemically from N-arylenamides of cyclohexyl aldehyde <97SC453>. A dihydroisoquinoline is formed in the photo-NOCAS reaction of isobutylene with 1,4-dicyanobenzene in acetonitrile <97JOC8432>. 

Desiraju has identified a series of recognition patterns which possess similar symmetry and directionality. The similarity in the formation of tapes by pipe-razine-2,5-dione (39), 1,4-benzoquinone (40) and 1,4-dicyanobenzene (41) can be observed in Fig. 28. The knowledge of the structure of 39 stabilized by N-H---0 hydrogen bonds can serve as a guide in anticipating the formation of tapes by 40 and 41. In the latter examples the directional properties of C-H---0 and C-H- -N hydrogen bonds are evident [68]. 

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