Photocyanation of Aromatic Hydrocarbons

Beneficial Micro Reactor Properties for the Photocyanation of Aromatic Hydrocarbons... 

Photocyanation of Aromatic Hydrocarbons Investigated in Micro Reactors Oiganic synthesis 43 [OS 43] Photocyanation of pyrene... 

Nitrobenzenes react with potassium cyanide in the presence of cetyltrimethylammo-nium bromide to yield benzonitriles [71], The reaction also requires the presence of chloro substituents on the ring and at least two nitro groups (Table 2.9). Diazosulphides, ArN=NSPh, are converted into the benzonitriles, ArCN, by a photochemically induced SRN1 reaction with tetra-n-butylammonium cyanide [72, 73], Yields vary from <20% to >70%. Photocyanation of aromatic hydrocarbons has been achieved using tetra-n-butylammonium cyanide in acetonitrile or dichloromethane [74, 75]. 

In many of the cases studied a nitro-group is present as a substituent in the aromatic reactant and one gets the impression that this is favourable to the reaction. On the other hand, quite a few examples are known where no nitro-group plays a role, e.g., in the reactions of anisoles (Bcirltrop et al., 1967 Nilsson, 1971 Lok and Havinga, 1973), in the photocyanation of aromatic hydrocarbons (Vink et al., 1972a), and in the photosubstitution of aromatic ketones (Letsinger and Colb, 1972). 

Beugelmans, R.,A. Ginsburg,A. Lecas,M.T. LeGoff,andG. Roussi, Use of Phase Transfer Agents for Photocyanation of Aromatic Hydrocarbons, Tetr. Lea., 3271 (1978). 

Photochemistry Photocyanation of aromatic hydrocarbons PTC carbonylation of aryl and vinyl halides under UV irradiation Reduction of nitrobenzenes to the corresponding oximes or quinones using viologens Photohydrogenation of acetylenic groups with viologen, Pt or Pd, and a photosensitizer Photochemically induced polymerization of methyl methacrylate Beugelmans et al. (1978) Brunet et al. (1983) Tomioka et al. (1986) Maidan and Willner (1986) Shimada et al. (1989, 1990)... 

The effect of entibititic residues m dairy products Photocyanation of aromatic compounds Hydrocarbon-water emulsions as fuels... 

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... 

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]. 

The PET-generated arene radical cations also undergo nucleophilic substitution via the a-complex. Photocyanation of arenes may be cited in this context as a very early example [139], where hydrogen served as the group undergoing displacement. This concept is further extended [140] for the direct amination of polynuclear aromatic hydrocarbons with ammonia or primary amines via the arene radical cation produced by irradiating arenes in die presence of DCNB. Another potentially useful application of this methodology is... 

The photocyanation of pyrene in a microchaimel through an oil-water interface was investigated by Ueno et al. [13]. The microchips employed are made of polystyrene by embossing with a silicone template. The phase transfer reaction proceeds in four steps as depicted in Figure 16.2. In the first step, a photoinduced electron transfer in the oil phase (polycarbonate) occurs from the aromatic hydrocarbon pyrene (DH) to the electron acceptor 1,4-dicyanobenzene (A). The cationic DH " radical is subsequently the target of the nucleophilic attack of the cyanide anion at the oil-water interface. The cyanated product DCN is insoluble in water and goes back into the oil phase. Experiments without a cyanide source (NaCN) in the aqueous phase show no reaction. Hence it can be excluded that the nudeophilic-substituted cyanide originates from the electron acceptor 1,4-dicyanobenzene. 

---