63017-87-8Relevant academic research and scientific papers
Reactions of Nitroarenes with Secondary and Tertiary Carbanions Bearing Both a Leaving Group and Electron-Withdrawing Group: An Approach to Dihydronaphth[2,1-c]isoxazole N-oxides and Dihydroisoxazolo[4,3-f]quinoline N-oxides
Maruoka, Hiroshi,Tomioka, Yukihiko
, p. 1051 - 1057 (2007/10/03)
2-Nitronaphthalene (1) and 6-nitroquinoline (2) underwent direct cyclocondensation with secondary and tertiary carbanions derived from a methylene and methine group bearing both a leaving group and electron-withdrawing group (e.g., methyl chloroacetate, ethyl chloroacetate, chloroacetonitrile, methyl 2-chloropropionate, ethyl 2-chloropropionate and 2-chloropropionitrile) in the sodium hydride/N,N-dimethylformamide system at low temperature, giving the corresponding dihydronaphth[2,1-c]isoxazole N-oxides 3 and dihydroisoxazolo[4,3-f]quinoline N-oxides 4. On the other hand, nitroarenes 1 and 2 reacted with secondary carbanions in the sodium hydride/tetrahydrofuran system to yield the corresponding conventional vicarious nucleophilic substitution (VNS) products 5 and 6.
NO2+ nitration mechanism of aromatic compounds: Electrophilic vs charge-transfer process
Tanaka, Mutsuo,Muro, Eiko,Ando, Hisanori,Xu, Qiang,Fujiwara, Masahiro,Souma, Yoshie,Yamaguchi, Yoichi
, p. 2972 - 2978 (2007/10/03)
The nitration of methylnaphthalenes with NO2BF4 and NOBF4 was examined in order to shed light on the controversial aromatic nitration mechanism, electrophilic vs charge-transfer process. The NO2+ nitration of 1,8-dimethylnaphthalene showed a drastic regioselectivity change depending on the reaction temperature, where ortho-regioselectivity at -78 °C and para- regioselectivity at 0 °C were considered to reflect the electrophilic and the direct or alternative charge-transfer process, respectively, because the NO+ nitration through the same reaction intermediates as in the NO2+ nitration via a charge-transfer process resulted in para-regioselectivity regardless of the reaction temperature. The NO2+ nitration of redox potential methylnaphthalenes higher than 1,8-dimethylnaphthalene gave a similar ortho-regioselectivity enhancement to 1,8-dimethylnaphthalene at lower temperature, thus reflecting the electrophilic process. On the other hand, the NO2+ nitration of redox potential methylnaphthalenes lower than 1,8-dimethylnaphthalene showed para-regioselectivity similar to the NO+ nitration, indicating the direct or alternative charge-transfer process. In the presence of strong acids where the direct charge-transfer process will be suppressed by protonation, the ortho-regioselectivity enhancement was observed in the NO2+ nitration of 1,8-dimethylnaphthalene, suggesting that the direct charge-transfer process could be the main process to show para- regioselectivity. These experimental results imply that the NO2+ nitration proceeds via not only electrophilic but also direct charge-transfer processes, which has been considered to be unlikely because of the high energy demanding process of a bond coordination change between NO2+ and NO2. Theoretical studies at the MP2/6-31G(d) level predicted ortho- and para-regioselectivity for the NO2+ nitration via electrophilic and charge- transfer processes, respectively, and the preference of the direct charge- transfer process over the alternative one, which support the experimental conclusion.
Charge-transfer Nitration of Naphthalene and the Methylnaphthalenes. Part 1. Direct Comparison with Electrophilic Aromatic Nitrations
Sankararaman, S.,Kochi, J. K.
, p. 1 - 12 (2007/10/02)
The various nitronaphthalenes formed in high yields from the selective photoexcitation of the EDA complexes of the naphthalene and methylnaphthalene donors (ArH) with the N-nitropyridinium and tetranitromethane acceptors are ascribed to charge-transfer nitration, arising as they do from the cation-radical pairs .+, NO2>.The nitration products from such an electron-transfer pathway are quantitatively compared with those from the electrophilic nitration (thermal), under otherwise the same conditions.The mechanistic implications to electrophilic aromatic substitution are discussed.
Nitration of Reactive Aromatics via Elelctron Transfer. V. On the Reaction between Nitrogen Dioxide and the Radical Cation Hexafluorophosphates of Some Methyl-substituted Naphthalenes
Eberson, Lennart,Radner, Finn
, p. 71 - 78 (2007/10/02)
The coupling reactions of series of methylnaphthalene radical cation hexafluorophosphates with nitrogen dioxide were studied in dichloromethane at low temperatures.Yields of nitro derivatives were generally higher with the β-methyl than with the α-methyl-substituted naphthalenes and the isomer distributions were different from those obtained in electrophilic aromatic nitration and nitrous acid catalyzed nitration.This confirm an earlier suggestion that the coupling reaction is not an elementary step of either nitration process.The high regioselectivity of the coupling reation can only partly be correlated with UHF spin densities.Pyrene+. hexafluorophosphate does not yield nitropyrenes upon treatment with nitrogen dioxide.This confirm earlier suggestions that only radical cations of aromatics with Eo values >= 1.7 V will take part in a successful (exergonic) coupling reaction with nitrogen dioxide.
