Naphthalene, cyanation

Figure 1. Influence of P(C6H5)3 concentration on the cyanation of 1-chloro-naphthalene in ethanol at 55°C (see Table VI)...

There have been several recent investigations into the mechanism of photo-cyanation of aromatic hydrocarbons. The process with naphthalene, biphenyl, and phenanthrene has been subjected to a kinetic analysis the reactions in dry or aqueous methyl cyanide are shown to involve two transient species, the first of which is an ionic complex formed from a triplet excimer of the arene, or, in the presence of an electron acceptor, from a triplet exciplex. Reaction of the transient complex with the cyanide ion yields the radical ArHCN, and in aqueous methyl cyanide this second transient reacts with itself to produce dihydrocyano- and cyano-compounds. In dry methyl cyanide the radical species is oxidized to the cyano product. 

The best conditions for nuclear cyanation involve the use of emulsions, typically CH2Cl2-H20-NaCN, with a phase-transfer agent. This has been described in detail for the monocyanation of naphthalene and anisole with isolated yields in the region 50-70% [222,223]. For dimethoxybenzenes the yields are somewhat lower [223]. 

Ellis, S., Fletcher, D., Gough, P. and Korn, S.R. (1982) Electrosynthesis in systems of two immiscible liquids and a phase transfer catalyst. I - the anodic cyanation of naphthalene. Journal of Applied Electrochemistry, 12, 687-691. 

Yan Hong-qiang, Wang Hua-qing, and Cheng Jie. Interpenetrating polymer networks from the novel bismaleimide and cyanate containing naphthalene Cure and thermal characteristics. Eur. Polym. J. 45 no. 8 (2009) 2383-2390. 

Photochemical cyanation of aromatic hydrocarbons in acetonitrile solution is a higher yield process when the potassium cyanide complex of 18-crown-6 is the cyanide ion source [31] compared to similar reactions in mixed organic aqueous solvent systems [32] (see Eq. 7.16). A ten-fold excess of 18-crown-6/KCN over the aromatic hydrocarbon (present in 10 " M) was used. The yield improvements were attributed to increased activity of cyanide due to diminished hydration of the ion. Biphenyl, naphthalene, phenanthrene, and anthracene were photocyanated in 50%, 15%, 25% and 20% yields respectively the latter being an equimolar mixture of mono and dicyanation products [31]. 

Phase transfer agents have been added to organic solutions in order to solubilize salts which comprise supporting electrolytes in electrolytic syntheses [33]. Both naphthalene and anisole were anodically cyanated in dichloromethane according to equation 7.17. The reaction was found to be clean, and high yield, although in both cases, mixtures of positional isomers were isolated. The fact that the reaction was not current efficient was compensated by the inexpensive nature of the supporting electrolyte. 

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