Nitration kyodai

Adamantane can be nitrated with N02 in the presence of ozone (Kyodai nitration) to afford 1-nitroadamantane with high regioselectivity.301 Product formation is interpreted by hydrogen abstraction by NO3 followed by rapid trapping of the resulting admantyl radical by N02. 

The ozone-mediated reaction of bicumene and some derivatives (11) with nitrogen dioxide in dichloromethane (kyodai nitration) at low temperatures results in the cleavage of the central C—C bond to yield the benzyl nitrate and products therefrom, in... 

Nitrogen oxides and oxygen in combination with Beta zeolites give also high conversion but do not show a selectivity improvement with respect to the classical Kyodai nitration process. However, for the double nitration of toluene, Beta is very selective towards the 2,4-dinitro isomer. 

Mori T. and Suzuki, H. Ozone-mediated nitration of aromatic compounds with lower oxides of nitrogen (the Kyodai nitration). Synlett, 1995, 383-392. 

Peng, X. and Suzuki, H. Regioselective double Kyodai nitration of toluene and chlorobenzene over zeolites. High preference for the 2,4-dinitro isomer at the second nitration stage, Org. Lett., 2001, 3, 3431-3434. 

A novel methodology for preparative aromatic nitration in which nitrogen dioxide acts a good nitrating agent for aromatic hydrocarbons and derivatives in the presence of ozone ( kyodai nitration) [362] has been applied for azoles [363] (Scheme 44). 

At low temperature pyrazole is easily A-nitrated giving 1-nitropyrazole in contrast to classical nitration based on the use of mixed acid 4-nitropyrazole is not formed. On prolonged reaction, a mixture of 4(5)-nitro- and 1,4-dinitropyrazole is obtained, whereas the last is prepared in the kyodai nitration of 4-nitropyrazole [363], The kyodai nitration of imidazoles gave a mixture of 4-nitro- and 1,4-dini-troimidazoles and 1,2,4-triazole - only a few percent of mononitro derivatives even after prolonged reaction [363],... 

So-called Kyodai nitration - a novel methodology of nitration with nitrogen dioxide and ozone - has been applied to several benzimidazoles with formation of 1-nitrobenzimidazoles and following conversion to 1-nitrobenzotriazoles [275], The nitration of benzotriazole /V-oxide with dilute nitric acid gives the 7-nitro derivatives, whereas nitration with a mixture of nitric and acetic acids leads to 5-nitro- and 7-nitro isomers in a ratio of 1 9 [276],... 

Ozone-mediated nitration (Kyodai nitration) of imidazole under neutral condition gave poor yields of 4-nitroimi-dazole. However, the yield improved dramatically with the addition of methanesulfonic acid. The combination NO2-O3 is a much more reactive electrophilic reagent since a reaction temperature of 0°C was sufficient (Scheme 56), <1996JCM244>. The 4-nitro product 238 could also be converted into 1,4-dinitroimidazole 239 over a long period. 

The highly selective N- and 0-functionalisation of adamantane based on the nitration procedure at -78 °C has been found [17]. Because of the symmetrical nature and high stability of the carbon framework, adamantane is a good model compound for examining the behaviour of alkanes toward the Kyodai nitration. 

Ozone-mediated nitration by the Kyodai nitration is snccessfully applied for various aromatic compounds [18,25-33]. The reaction proceeds by a double mode depending on the oxidation potential of the substrate. Deactivated aromatic compounds are likely to react with in most cases via the nitronium ion forming in (Equation 5.55), but substrates of lower oxidation potential are easily oxidised by NO3 to form the corresponding radical cations ... 

Bicumenes are readily oxidised to form radical cations and can be used as probes for electron transfer processes. These componnds have been chosen to confirm involvement of the electron transfer process in the Kyodai nitration [18]. Bicumene was stable toward NO in a dilute dichloromethane solution at -20 C. However, when ozone was introdnced into this solution at the same temperature, the hydrocarbon was rapidly cleaved at the central position to produce 2-phenylpropene, 2-phenylpropan-2-ol and acetophenone ... 

The yields of (Equation 5.76) products are quite low (0.2-18%), except when R, R2 = NO, R = H (33% for 1,5,6-trinitro-benzimidazole). Benzimidazoles with electron-withdrawing substituents tend to give a higher yield of products. Pathways for the formation of products from benzimidazole by the Kyodai nitration are shown below ... 

On the assumption of NO3 being the initial electrophile for the Kyodai nitration, the reaction of aromatic compounds with the ternary mixture of NO-NO -O is of special interest because the gas-phase oxidation of NO to NO is known to involve two isomeric unstable intermediates the asymmetric (O-N-O-O) and the symmetric [0-N(0)-0] NO3 [33] ... 

The observation that the ternary mixture NO-NO -O is more effective for nitrating aromatic substrate than a binary mixture of NO -O may reveal a possible role of NOg as the initial electrophile in the Kyodai nitration. Toluene is inert towards NO alone, but in the presence of NO it slowly undergoes ring nitration and side-chain oxidation, giving a mixture of nitrotoluenes, benzyl nitrate, phenylnitromethane and benzaldehyde ... 

The application of the standard Kyodai nitration procedure for pyridine gives a mixture of 5- and 3, 5-nitropyridine in only 2-5% yield [34]. However, pyridine can be efficiently nitrated by N,0 in liquid sulphur dioxide to give 3-nitropyridine in 68% yield [35]. The role of sulphur dioxide in the process is evident from the following scheme [34] ... 

Toluene is moderately activated, so the Kyodai nitration of this hydrocarbon is always accompanied by more or less dinitration product. On inspecting the isomer composition of this byproduct in the course of the Kyodai nitration in the presence of montmorillonite KIO and zeolites HZSM-5 or HBEA-25, a considerable preponderance of 2,4-dinitrotoluene over the 2,6-dinitro isomer 2,4-12,6- = 5.1-9.3) has been discovered [38]. In the classical nitration based on mixed acids, the 2,4-dinitro and 2,6-dinitro isomers were obtained in about a 4 1 ratio. The nature of organic solvent was found to exert considerable influence on the regioselectivity of dinitration. Of the four solvents of varied polarity (n-C Hj, CCl CH Cl, MeCN), acetonitrile with a high dielectric constant exhibited the best result. The 2,4-/2,6-isomer ratio is enhanced up to 12 in acetonitrile, whereas these values are 5 in n-C Hj, 4.1 in CCl and 9.3 in CH Cl. ... 

At the dinitration of chlorobenzene, the regioselection in the presence of zeolites was again improved in favour of the 2,4-dinitro isomer 2,4-12,6- = 48) [38]. In the presence of Faujasite-712, the nitration of o-chlorobenzene with N Oj gives a mixture of l-chloro-2,4-dinitro- and l-chloro-2,6-dinitrobenzenes in about 30 1 ratio [39]. Thus, the procedure for the regioselective dinitration of toluene and chlorobenzene described above, which involves the Kyodai nitration in polar organic solvent in the presence of zeolites, provides a new efficient route to 2,4-dinitro derivatives under nonacid conditions. The method is easy to carry out, environmentally benign, and economical. 

The pathway from styrene to the side-chain nitration products in the Kyodai nitration is depicted by the following reactions ... 

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