Naphthalenes dicyano

Azomethine ylids can be generated photochemically by irradiating N-protected bis(trimethylsilylmethyl)amines in the presence of a sensitizer (1,4-dicyano-naphthalene, DCN ) in methanol as the solvent. The ylid reacted with a series of dipolarophiles to give adducts in moderate to good yields.446,447... 

Pandey has tentatively proposed the involvement of enolates in the photo-induced electron transfer oxidation of arylacetones by the system 1,4-dicyano-naphthalene (8 mol%)/acetonitrile/aqueous NaOH [1 ]. The corresponding benzofurans were obtained in 50-60% yield, but the mechanism is speculative since no oxidant in stoichiometric amounts was present. It was assumed that cyclization takes place on the stage of the a-carbonyl radical. 

Some aromatizations are accomplished with agents other than those previously mentioned. Thus tetralin is converted quantitatively into naphthalene by refluxing with 2,3-dix hloro-5,6-dicyano-p-benzoquinone [970], and 1,2,3,4-tetrahydrocarbazoles are transformed into carbazoles in 50-95% yields by refluxing with chloranil in xylene [969], Anhydrous aluminum chloride in refluxing carbon disulfide is used in the preparation of coronene [408]. 

A solution of 0.65 g (0.005 mol) of tetralin and 1.14 g (0.005 mol) of 2,3-dichloro-5,6-dicyano-p-benzoquinone in 5 mL of benzene is refluxed for 45 min, during which period the initidly red solution becomes colorless. A solution of an additional 1.14 g (0.005 mol) of the quinone in 2 mL of benzene is added, and the refluxing is continued for an additional 75 min. After dilution with light petroleum, the solution is filtered, passed through a column of alumina, and evaporated to give 0.42 g (70%) of naphthalene, mp 79-80 °C. The petroleum-insoluble residue yields 0.7 g (61%) of colorless 2,3-dichloro-5,6-dicyanohydroquinone, mp 263 °C (dec), after crystallization from aqueous ethanol. 

Cyclic vicinal diazides undergo a thermal ring fission with formation of dinitriles. In this manner 1,2-diazidobenzenes yielded (in ca. 80% yield) cis, cw-l,4-dicyano-1,3-butadienes (78), and 1,2-diazido-naphthalene yielded as-2-cyanocinnamonitrile (79)... 

The oxidation of hydroarenes to arenes by quinones such as 2,3-dichloro-5,6-dicyano-l,4-quinone (DDQ) is frequently used for the synthesis of aromatic compounds. Brower et al. have already shown that the dehydrogentaion 1,4-cyclo-hexadiene to benzene [128] or tetraline to naphthalene [129] by thymoquinone is accelerated by pressure giving a negative volume of activation ((AV = —33 (75 °C) and —28 (175 °C) cm mol respectively). A similar effect of pressure has been observed for the oxidation of leuco crystal violet with p-chloranil ((AV = -25 cm mol (21 °C) [130]. The pressure-dependent kinetic isotope effect of this reaction (29 °C kn/ D = H-5 (1 bar) and 8.2 (1.5 kbar)) indicates that hydrogen transfer occurs in the rate-determining step. The large kn/ko value at 1 bar and it pressure dependence was attributed to a quantum mechanical tunneling. 

A 1 1 0.5 mixture of 4-benzoylhepta-1,6-diene, diphenyl diselenide, and 1,4-dicyano-naphthalene in aq. acetonitrile irradiated in a Rayonet photochemical reactor fitted with 300 nm lamps - product. Y 65%. F.e. inch ring closure of ethylene-alcohols and -phenols s. G. Pandey et al., J. Chem. Soc. Chem. Commun. 1989, 416-7. 

Quinones, as oxidation products of aromatic systems, are capable of being reduced back to aromatic systems and some quinones are used particularly for this purpose. For example, as shown in Scheme 6.79, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) can be used to oxidize 1,2,3,4-tetrahydronaphthalene (tetraUn, CioFli2) to naphthalene (CioHg) while it is reduced to the corresponding phenol, 2,3-dichloro-5,6-dicyanohydroquinone (DDQ H2). Further, while reduced to the same product, DDQ is also capable of oxidizing 1,3,5-cycloheptatriene to the corresponding, aromatic cycloheptatrienyl cation and, if the oxidation is carried out in perchloric acid, the perchlorate of the cation is an isolable salt (Scheme 6.79). 

Although it has not yet been studied by quantum-chemical calculations, preliminary results indicate that these A, A -dicyano-l,4-anthraquinonediimines should present an interesting photoinduced electron transfer from the donor naphthalene moiety to the acceptor unit located on the DCNQI ring in agreement with that observed for the TCNQ analogues recently reported [24]. 

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