- Nitration of deactivated aromatic compounds via mechanochemical reaction
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A variety of deactivated arenes were nitrated to their corresponding nitro derivatives in excellent yields under high-speed ball milling condition using Fe(NO3)3·9H2O/P2O5 as nitrating reagent. A radical involved mechanism was proposed for this facial, eco-friendly, safe, and effective nitration reaction.
- Wu, Jian-Wei,Zhang, Pu,Guo, Zhi-Xin
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supporting information
(2021/05/05)
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- Continuous-Flow Nitration of o-Xylene: Effect of Nitrating Agent and Feasibility of Tubular Reactors for Scale-Up
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Continuous-flow nitration of o-xylene has been studied with different nitrating agents over a wide range of conditions for different parameters such as temperature, residence time, and concentrations. A nitrating mixture comprising sulfuric acid and fuming nitric acid was seen to yield higher selectivity for the isomer 1,2-dimethyl-3-nitrobenzene over the isomer 1,2-dimethyl-4-nitrobenzene and also a non-negligible quantity of dinitro derivatives of o-xylene. With only fuming nitric acid as the nitrating agent, the reaction was selective for 1,2-dimethyl-4-nitrobenzene over 1,2-dimethyl-3-nitrobenzene. Impurities mainly come from nitration of mononitro derivatives, and this occurs more from nitration of the 3-nitro isomer because of its higher reactivity with nitric acid. An economic analysis of the continuous-flow reactor for the production of 1,2-dimethyl-4-nitrobenzene at 100 and 500 kg/h in a jacketed tubular reactor showed that numbering-up is a more economical approach for higher production capacity. A combination of large- and small-sized tubes depending upon the relative rates of heat generation during a reaction will achieve more profit and a shorter payback period than having the entire reactor made of a single tube size.
- Sharma,Joshi,Kulkarni
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p. 1138 - 1147
(2015/09/28)
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- On the role of guests in enforcing the mechanism of action of gated baskets
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We designed and prepared a spacious and gated basket of type 2 (V = 318 A3) in ten synthetic steps. With the assistance of 1H NMR spectroscopy, we found that the pyridine gates at the rim of 2 form a seam of N-H...N hydrogen bonds, t
- Ruan, Yian,Wang, Bao-Yu,Erb, Jeremy M.,Chen, Shigui,Hadad, Christopher M.,Badjic, Jovica D.
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supporting information
p. 7667 - 7675
(2013/11/06)
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- Thiourea-enhanced flavin photooxidation of benzyl alcohol
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Upon irradiation, flavin oxidises 4-methoxybenzyl alcohol to the corresponding aldehyde using aerial O2 as the terminal oxidant. We have observed that this reaction is significantly accelerated by the presence of thiourea. A series of thiourea-functionalised flavins has been prepared from flavin isothiocyanates and their photocatalytic efficiencies have been monitored by NMR. The alcohol photooxidation proceeds rapidly and cleanly with high turnover numbers of up to 580, exceeding previously reported performances. A likely mechanistic rationale for the more than 30-fold acceleration of the photo-redox reaction by thiourea has been derived from spectroscopic, electrochemical, and kinetic studies. Thus, thiourea acts as an electron-transfer mediator for the initial photooxidation of 4-methoxybenzyl alcohol by the excited flavins. This mechanism has similarities to electron-relay mechanisms in flavoenzymes, for which cysteine sulfenic acid intermediates are proposed. The observation that thiourea mediates flavin photo-redox processes is valuable for the design of more sophisticated photocatalysts based on Nature's best redox chromophore.
- Svoboda, Jiri,Schmaderer, Harald,Koenig, Burkhard
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supporting information; scheme or table
p. 1854 - 1865
(2009/04/06)
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- A Fast, High-Yield Preparation of Vicinal Dinitro Compounds Using HOF·CH3CN
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HOF·CH3CN, a very efficient oxygen-transfer agent, was reacted with various aliphatic and aromatic vicinal diamino compounds. The products were the rare, vicinal dinitro derivatives formed in excellent yields and short reaction times. This is in contrast to other oxygen-transfer agents which tend to break the central C-C bond of the diamino precursor. This reaction was also used for making dinitro compounds with all four oxygens, being the [18]O isotope.
- Golan, Elizabeth,Rozen, Shlomo
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p. 9170 - 9172
(2007/10/03)
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- Efficient syntheses of a flavin and an 8-hydroxy-5-deazaflavin amino acid and their incorporation into oligopeptides
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We report a convenient synthesis for the cofactor amino acids (S)-3 and (S)-4 in which the C5-ribose chain of the original riboflavin and ribo-5- deazaflavin cofactors is replaced by a C5-amino acid side chain. Both cofactor amino acids are available in enantiomerically pure form in gram quantities and can be incorporated into oligopeptides using a standard Fmoc- based solid-phase peptide synthesis protocol. The benzyl-protecting group of the 8-hydroxy-5-deazaflavin can be cleaved by hydrogenolysis directly on the peptide. This allows the investigation of the properties of the peptide bound redox active OH- and the deprotonated O- form of the deazaflavin. Due to the electron- and energy-transfer properties of both cofactors, applications of both amino acid in the preparation of peptide- and protein-based biosensors, of catalytically active peptides, or as chemical rulers for distance measurements in biopolymers based on the fluorescence resonance energy- transfer technology can be envisaged.
- Carell, Thomas,Schmid, Holger,Reinhard, Markus
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p. 8741 - 8747
(2007/10/03)
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- Towards artificial DNA-repair enzymes: Incorporation of a flavin amino acid into DNA-binding oligopeptides
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Mimicking DNA photolyases: Model proteins containing the flavin amino acid L-1 within the DNA-binding domain of a transcription factor are capable of completely repairing damage from the formation of pyrimidine dimers in single-stranded oligonucleotides.
- Carell,Butenandt
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p. 1461 - 1464
(2007/10/03)
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- ipso Nitration. XXVI. Nitration of 1,2-dimethyl-4-nitrobenzene. Formation and reactions of adducts
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Nitration of 1,2-dimethyl-4-nitrobenzene in a mixture of acetic anhydride and trifluoroacetic anhydride gives the diastereoisomers of 4,5-dimethyl-2,4-dinitrocyclohexa-2,5-dienyl acetate (50percent), in addition to the 1,2-dimethyldinitrobenzenes.In moderate and more strongly acid conditions the adduct gives 4-nitro-, 3,4-dinitro-, and 3,5-dinitro-o-xylene.In neutral and weakly acid solutions 4-nitro- and 3,5-dinitro-o-xylene are formed by a radical and a sigmatropic pathway.The adduct reacts facilely with nucleophiles by allylic substitution to give a 5,6-dimethyl-6-nitrocyclohexa-2,4-dienyl derivative which, in many instances, undergoes a second allylic substitution to a new 4,5-dimethyl-2,4-dinitrocyclohexa-2,5-dienyl derivative.Depending on the nature of the introduced substituent, these 2,4- and 2,5-dienyl products may eliminate nitrous acid, under the reaction conditions, to give the corresponding aromatic compound.The dienyl acetates undergo acid-catalysed transesterification to the corresponding dienols.
- Fischer, Alfred,Henderson, George N.,Iyer, Lokanathan M.
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p. 2390 - 2400
(2007/10/02)
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