- An "ortho effect" in electrophilic aromatic nitrations: Theoretical analysis and experimental validation
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Usually, a π-donor substituent acts as an ortho/para directing group in an electrophilic aromatic substitution reaction, and a π-acceptor substituent acts as a meta directing group. Interestingly, when a π-acceptor substituent is meta to a π-donor substituent, certain electrophilic aromatic nitration occurs ortho to the π-acceptor substituent rather than para . The "ortho effect", highlighted in various textbooks, has been tentatively analyzed here based on ab initio calculations. The reliability of the calculations was verified by the corresponding experimental data, including a newly-designed electrophilic aromatic nitration that also gave reasonable product distributions.
- Li, Hui-Jing,Wu, Yan-Chao,Dai, Jian-Hong,Song, Yan,Cheng, Runjiao,Qiao, Yuanyuan
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p. 1307 - 1312
(2015/02/05)
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- Regioselectivity nitration of aromatics with N2O5 in PEG-based dicationic ionic liquid
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Regioselective mononitration of simple aromatic compounds has been investigated with N2O5 as nitrating agent and a new PEG200-based dicationic acidic ionic liquid (PEG200-DAIL) as catalyst. The results of experiments show that this nitration system can significantly improve the para-selectivity of alkyl-benzenes and the ortho-selectivity of halogenated-benzenes. The PEG200-DAIL exhibits recyclable temperature-dependant phase behavior in CCl4 solvent, and it can be recycled without apparent loss of catalytic activity, and only 5% loss of weight is observed after six times recycling.
- Wang, Peng-Cheng,Lu, Ming
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supporting information; experimental part
p. 1452 - 1455
(2011/05/16)
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- Aromatic nitration using nitroguanidine and EGDN
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Acid catalyzed nitration has been examined using a variety of novel nitration agents: guanidine nitrate (GN) and nitroguanidine (NQ) as well as the simple nitrate ester, ethylene glycol dinitrate (EGDN). Reactions with either activated or deactivated aromatic substrates proceed rapidly and in high yield. Regioselectivity was similar for all nitrating agents examined. The synthetic advantages of liquid EGDN include high solubility in organic solvents, strong nitration activity and ease of preparation.
- Oxley, Jimmie C.,Smith, James L.,Moran, Jesse S.,Canino, Jonathan N.,Almog, Joseph
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p. 4449 - 4451
(2008/12/21)
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- Urea nitrate and nitrourea: powerful and regioselective aromatic nitration agents
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Urea nitrate (UN) and nitrourea (NU), easily prepared from urea and nitric acid, convert deactivated aromatic compounds to the corresponding nitrated derivatives with a high yield and a high regioselectivity under very mild conditions. The performance of the two reagents is quite similar indicating that NU is an intermediate in the UN nitration process.
- Almog, Joseph,Klein, Asne,Sokol, Anat,Sasson, Yoel,Sonenfeld, Dana,Tamiri, Tsippy
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p. 8651 - 8652
(2007/10/03)
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