- 113. Highly Regioselective Nitration of Hexamethylbenzene and Its Derivatives to Dinitroprehnitene with Excess Nitronium Tetrafluoroborate
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Hexamethylbenzene and its derivatives undergo very clean regioselective dinitration to dinitroprehnitene (1,2,3,4-tetramethyl-5,6-dinitrobenzene) with excess of nitronium tetrafluoroborate in dry CH2Cl2 solution.The mechanism of this unexpected new nitrat
- Prakash, G.K. Surya,Wang, Qi,Li, Xing-Ya,Olah, George A.
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- Synthesis and activity of 1H-benzimidazole and 1H-benzotriazole derivatives as inhibitors of Acanthamoeba castellanii
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Chloro-, bromo- and methyl- analogues of 1H-benzimidazole and 1H-benzotriazole and their N-alkyl derivatives have been synthesized and tested in vitro against the protozoa Acanthamoeba castellanii. The results indicate that 5,6-dimethyl-1H-benzotriazole (11) and 5,6-dibromo-1H-benzotriazole (14) have higher efficacy than the antiprotozoal agent chlorohexidine.
- Kopańska, Katarzyna,Najda, Andzelika,Zebrowska, Justyna,Chomicz, Lidia,Piekarczyk, Janusz,Myjak, Przemys?aw,Bretner, Maria
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p. 2617 - 2624
(2007/10/03)
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- Synthesis of Chiral Cobalt Complexes with Planoid-Tetradentate Ligand System
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The synthesis of a series of Cbl-related, achiral Co(III) complexes 9a-c as well as enantiomerically pure, C2-symmetric Co(III) complexes 15 and 18, is reported (Schemes 3, 5, and 7).The crystal structures of 9c and 15 were determined.Complex 18 acts as an enantioselective catalyst in the isomerization of 1,4-epiperoxides to hydroxycycloalkenones.
- Haerter, Ralph,Weymuth, Christophe,Scheffold, Rolf,Engel, Peter,Linden, Anthony
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p. 353 - 371
(2007/10/02)
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- Electrophilic Aromatic Substitution. Part 27. Chemical Selectivities Disguised by Mass Diffusion. Part 6. The Kinetics of Nitration in Aqueous Sulphuric Acid of Durene (1,2,4,5-Tetramethylbenzene). Nitrodurene, and Nitroprehnitene (Nitro-1,2,3,4-tetramethylbenzene). A Comparison ...
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Durene (1,2,4,5-tetramethylbenzene) is nitrated in sulphuric acid at the encounter rate.Nitrations of nitrodurene and nitroprehnitene (nitro-1,2,3,4-tetramethylbenzene) are complicated by the formation of nitrous acid, presumably as a consequence of ipso-attack, and subsequent undefinied reactions of this.When an efficient nitrous acide trap is present the complications are removed and the kinetics become straightforward.Although nitrobenzene is 108 times less reactive than benzene in nitration, nitroprehnitene and nitrodurene are only 41 and 20 times less reactive than their respective parent hydrocarbons.These reduced relative reactiviities are a consequence of the fact that prehnitene and durene react at the encounter rate.The low relative reactivity of durene and 3-nitrodurene leads to the formation of some 3,6-dinitrodurene in the nitration of durene, even under the most favourable circumstances, and if mixing is inefficient the dinitro-compound may be the main product.By measuring the yield of 3-nitrodurene, as it varies with acidity, it is possible to determine the amount formed by direct attack at C-3 as distinct from that formed by ipso-attack followed by rearrangement.As a consequence the ratio of positional selectivity between C-3 and C-1 is shown to be 1 : 3.6.Thus, positional selestivity does not disappear.The intrinsic rate constants for nitronium ion nitrations in sulphuric acid of a number of methylnitrobenzenes show an excellent linear correlation with those for nitrations with nitronium hexafluorophosphate in nitromethane deduced by application of a theoretical mixing-reaction model.Differences between the two systems are not large, but appear to be in the direction showing the electrophile in sulphuric acid to be rather more reactive and more selective than in the organic solvent.
- Manglik, Ajay K.,Moodie, Roy B.,Schofield, Kenneth,Dedeoglu, Erol,Dutly, Andreas,Rys, Paul
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p. 1358 - 1366
(2007/10/02)
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