20062-22-0

An environmental friendly approach for two-step synthesis of hexanitrostilbene (HNS) has been studied here. In the first step from trinitrotoluene (TNT) to hexanitrobienzyl (HNBB), commercial NaClO was employed as oxidant in mixed solvent of ethyl acetate/ethanol (0.25 mL/1.25 mL per mmol of TNT) instead of benzene/ethanol. In the second step from HNBB to HNS, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/FeCl2 was used as an effective catalytic system with O2 in DMSO solvent. A complex of metal ion and O2 [M(n+1)OO?] was supposed to be the active agent, and TEMPO itself was difficult to initiate dehydrogenation of HNBB but could promote the catalytic cycle of complex M(n+1)OO?. Finally, we increased the scale from 30 to 1000 g to investigate the feasibility of production. The total yield of two steps would be unprecedentedly as high as 70%.

Hexanitrostilbene (HNS) was efficiently produced through the dehydrogenation of hexanitrobibenzyl (HNBB) with oxygen catalyzed by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)/ferrous chloride (FeCl2) in 80% yield, and up to a 308 turnover number was achieved. First, TEMPO is used in the dehy-drogenation and the influence of reaction time, temperature, solvent and the catalyst were discussed. A possible mechanism of this catalytic process is proposed and it is obtained that Fe(II) can abstract hydrogen from HNBB and the function of the function of TEMPO is to oxidize Fe(II)OOH to Fe(III)OO..

The invention relates to a preparation method of o-nitrobenzaldehyde. The preparation method comprises the following steps: reacting o-nitrobenzyl triphenylphosphonium bromide with the required product o-nitrobenzaldehyde as raw materials to generate 1, 2-bis (o-nitrophenyl) ethylene, and oxidizing with ozone to obtain o-nitrobenzaldehyde. The preparation method has the beneficial effects that only a proper amount of alkali is used for catalysis in a condensation reaction, and an intermediate product 1, 2-bis (o-nitrophenyl) ethylene can be efficiently obtained by catalysis of an alkaline water reaction; and gas-liquid reaction is performed by using a micro-channel reactor to finally obtain the required nitrobenzaldehyde. The method has the advantages of less used raw materials, high reaction yield, less by-products and impurities, simple and feasible purification operation, and convenience for industrial production in workshops. Under the condition that the current chemical engineering environment protection and safety situation is severe, the process route can stably supply the important chemical intermediates of the type in an environment-friendly mode with the extremely high atom utilization rate.

The invention relates to a preparation method of o-nitrobenzaldehyde, which comprises the following steps: preparing 1,2-bis(o-nitrophenyl)ethylene by using required products nitrobenzaldehyde and nitrotoluene as raw materials, and carrying out high-efficiency oxidation by using ozone with proper concentration to obtain the final product nitrobenzaldehyde. The preparation method has the beneficialeffects that only a proper amount of alkali is used for catalysis in the condensation reaction, and the intermediate product 1,2-bis(o-nitrophenyl)ethylene can be efficiently obtained by using a conventional solvent to carry out a reaction with water; a gas-liquid reaction then is carried out by using a micro-channel reactor to finally obtain the required nitrobenzaldehyde. The method has the advantages of low use amount of raw materials, high reaction yield, few byproducts and impurities, simple and feasible purification operation and convenience for industrial production in workshops.

The invention discloses a synthetic method of hexanitrostilbene (HNS). The method is used for solving the problems of high quality requirement, difficult weighing and irritant gas generation of liquid bromine used in the process for synthesizing the HNS from hexanitrobibenzyl. The HNS is prepared from the hexanitrobibenzyl under the action of a solid dehydrogenating agent by using a mixed solvent as a solvent. The method is mainly used for synthesizing the HNS.

The present invention relates to a 2,2',4,4',6,6'-hexanitro diphenylethylene preparation method, which comprises that: (1) 2,4,6-trinitrotoluene and sodium hypochlorite are subjected to a reaction in a reaction solvent to prepare hexanitro bibenzyl, wherein the reaction solvent is a mixing solution of ethanol and benzene, and (2) the hexanitro bibenzyl and bromine are subjected to a reaction in a reaction solvent to prepare 2,2',4,4',6,6'-hexanitro diphenylethylene, wherein the reaction solvent is a mixing solution of dichloroethane and pyridine, the reaction solutions in the step (1) and the step (2) can be filtered to collect the filtrates, and the filtrates can be used as the reaction solvent of the corresponding steps. Compared with the preparation method in the prior art, the preparation method of the present invention has the following characteristics that: the coupling reaction solvents can be recycled, the solvent loss in the dehydrogenation reaction is less, and the pyridine consumption is less.

A simple and effective oxidative dehydrogenation of nitro derivatives of bibenzyl was developed using a mixture of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and metal salts as catalyst under an atmospheric pressure of oxygen. The oxidation of several nitro derivatives of bibenzyl led to corresponding nitro stilbene in good yields, and the yields increased with the increase in the substituted nitro group on the bibenzyl. For example, the aerobic dehydrogenation of 2,2,4,4,6,6-hexanitrobibenzyl in the presence of a catalytic amount of TEMPO with metal salts gave 2,2,4,4,6,6-hexanitrostilbene in 81 % yield and 4,4-dinitrostilbene-2,2-disulfonic acid (75 %) was obtained from 4,4-dinitrobibenzyl-2,2-disulfonic acid. Iranian Chemical Society 2012.

Previous work on a Shipp-Kaplan type synthesis of hexanitrostilbene (HNS) using a Kenics static mixer (ref1, from Chemineer Ltd., Cranmer Road, West Meadows, Derby DE21 6XT, UK; www.chemineer.com) has been extended by using a larger mixer (9.5 mm vs 4.75 mm OD), enabling the scale to be increased from 2.5 g to 25 g of trinitrotoluene (TNT) for the same mixing time (2SO4 and NaOH solutions, and (iii) pH control using aqueous RNH3Cl and RNH2 solutions. Other parameters that have been varied are the ratio of NaOCl to TNT (0.5-1.2) and the concentration of both reactants. The yields of crude HNS that have been achieved, whilst not outstanding, are an improvement over the conventional batch process. It has been demonstrated that the yield and selectivity of the HNS synthesis can be considerably increased if, during the after-reaction period, the reaction conditions are pH controlled. The yield and selectivity are also significantly enhanced by using more dilute reaction solutions.

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