Pd-catalyzed silicon hydride reductions of aromatic and aliphatic nitro groups

[reaction: see text] Room-temperature reduction of aromatic nitro groups to amines can be accomplished in high yield, with wide functional group tolerance and short reaction times (30 min) using a combination of palladium(II) acetate, aqueous potassium fluoride, and polymethylhydrosiloxane (PMHS). Replacing PMHS/KF with triethylsilane allows aliphatic nitro groups to be reduced to their hydroxylamines.     

Selective catalytic hydrogenation of nitro groups in the presence of activated heteroaryl halides

Chemoselective reduction of nitro groups in the presence of activated heteroaryl halides was achieved via catalytic hydrogenation with a commercially available sulfided platinum catalyst. The optimized conditions employ low temperature, pressure, and catalyst loading (<0.1 mol % Pt) to afford heteroaromatic amines with minimal hydrodehalogenation byproducts.     

Selective reduction of aromatic nitro compounds containing o- and n-benzyl groups with hydrazine and raney nickel

The selectiity in the catalytic reduction of aromatic nitro compounds containing O-benzyl, N-benzyl or chlorine with hydrazine and Raney nickel was studied.     

Selective reduction of one, two, or three nitro groups in 1,3,5-trinitrobenzene with hydrazine hydrate

A method was developed for successive selective reduction of one, two, or three nitro groups in 1,3,5-trinitrobenzene with hydrazine hydrate in the presence of iron chloride and charcoal. This method provides an approach to the one-pot synthesis of 3,5-dinitroaniline, 1,3-diamino-5-nitrobenzene, or 1,3,5-triaminobenzene from 1,3,5-trinitrobenzene. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 904–905, May, 2006.     

Nucleophilic displacement of aromatic nitro groups

The relative nucleofugicity of the nitro group in many aromatic nucleophilic substitution reactions rivals, and in some cases surpasses, that of the fluorine atom. The use of the nitro function as a leaving group in such reactions facilitates the synthesis of novel substituted benzene derivatives and simplifies the synthesis of a wide variety of heterocycles.     

Selective hydrogenation of nitro derivatives of hydroquinolines

By catalytic hydrogenation of p-nitrophenylhydroquinolines with 5-oxo- and 5-oxime functional groups in the presence of heterogeneous palladium complex catalysts, we have obtained the corresponding amino derivatives.Scientific-Research Institute of Chemistry at Saratov State University, Saratov 410026. Translated from Khimiya Geterotsildicheskikh Soedinenii, No. 8, pp. 1138–1140, August, 1995. Original article submitted June 8, 1995.     

Semimicro determination of nitro groups by reduction with titanous sulphate

Summary A simple and rapid procedure for the determination of nitro groups in organic compounds, based on the usual macro method of reduction with titanous sulphate, has been described. 20–25 mg sample, dissolved in glacial acetic or in aldehyde free ethanol (if the sample was steam volatile), was heated for 15 to 30 minutes with an excess of titanous sulphate, after reduction the excess reducing agent being estimated by back titration against standard solution of ferric ammonium sulphate. The entire operation was carried out in an atmosphere of nitrogen.

---

Zusammenfassung Ein Verfahren zur einfachen und schnellen Bestimmung von Nitrogruppen in organischen Verbindungen in Probemengen von 20–25 mg ist auf Grund der Reduktion mit Titan(III)-sulfat ausgearbeitet worden. Die Probe wird in Eisessig (wasserdampfflüchtige Substanzen in aldehydfreiem Äthanol) gelöst; mit einem Überschuß an Titan(III)-sulfat 15 bis 30 min erhitzt, und nach erfolgter Reduktion wird der Überschuß des Reduktionsmittels mit Eisen(III)-ammoniumsulfatlösung zurücktitriert. Es wird in Stickstoffatmosphäre gearbeitet.

     

Microdetermination of nitro groups in organic compounds

Summary A simple procedure for microdetermination of nitro groups in organic compounds is described. It is based on reduction with palladium-on-carbon catalyst in acetic acid in a modified Roth apparatus.

---

Zusammenfassung Ein einfaches Verfahren zur Mikrobestimmung von Nitrogruppen in organischen Verbindungen wurde beschrieben. Es beruht auf der Reduktion in Essigsäure mit Palladium-Kohle als Katalysator in einem modifizierten Apparat nachRoth.

     

Studies on substitution of nitro groups in 1,3,5-trinitrobenzene with NH-azoles

Conditions were found under which NH-azoles (benzotriazole and its derivatives, 1,2,3- and 1,2,4-triazoles, pyrazole and its derivatives) replace one nitro group in 1,3,5-trinitrobenzene (TNB) to form the corresponding N-(3,5-dinitrophenyl)azoles in the presence of inorganic bases in aprotic dipolar solvents. The reaction pathway was found to depend on the structure of the starting azole. The benzotriazolyl and 1,2,4-triazolyl fragments activate the replacement of the meta-nitro group to virtually the same extent as the nitro group in TNB, which made it possible to successively replace all three nitro groups in TNB.     

Observations on the reduction of aryl nitro groups with palladium-sodium borohydride

The reduction of aryl nitro groups by the palladium-sodium borohydride system can be controlled in some instances to give products differing from those of catalytic hydrogenation. With six equivalents of borohydride added to the catalyst 2,2′-dinitrobiphenyl formed only 2,2′-diaminobiphenyl. With added sodium hydroxide and varying amounts of borohydride and catalyst, the reduction can be controlled to give benzo[c]cinnoline, benzo[c]cinnoline 5-oxide or benzo[c]cinnoline 5,6-dioxide. In a closed system, the reagents reduce both the nitro and olefin functional groups in 6-nitro-5,8-dimethoxy-1,4-dihydro-1,4-ethano-naphthalene. In an open flask flushed with argon, the reduction is confirmed to the nitro group. Reduction of 2-chloro and 4-chloronitrobenzene with palladium-borohydride gives substantial yields of the appropriate chloroanilines. In contrast, hydrogen and palladium give aniline as the major product from each of these. These results suggest that the addition of sodium borohydride to palladium on carbon produces a reductive entity differing from that of catalytic hydrogenation.     

Nonempirical calculations of the major force constants of the nitro groups in nitro compounds

Conclusions The nonempirical LCAO MO SCF method in the STO-3GF and 4-31GF bases was used to calculated the major force constants of nitro groups of several aliphatic nitro compounds, their salts, and nitroylides. The differences in the force constants in this series were analyzed and the maximum relative changes were found to occur for the off-diagonal elements of the force matrix.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 947–949, April, 1985.     

Periodic mesoporous organosilica with large heterocyclic bridging groups

Periodic mesoporous organosilica with a heterocyclic bridging group of large molecular weight, tris[3-(trimethoxysilyl)propyl]isocyanurate, is reported. Incorporation of an organic moiety into the silica framework afforded material attractive for adsorption of mercury and related heavy metal ions from aqueous solutions.     

Preparation of mesoporous silicon dioxide with high specific surface area

The influence of the reactant ratio on the specific surface area, total pore volume, and mean pore diameter of mesoporous silicon dioxide prepared by the sol-gel method was examined. The optimal reactant ratio for preparing the material with a high specific surface area was determimed.     

Synthesis of novel unsymmetrical phthalocyanines substituted with crown ether and nitro groups

This work reports on the synthesis of new unsymmetrically substituted phthalocyanines (M = Zn, Cu, Co, Ni) bearing three benzo-15-crown-5 units through oxy bridges and a nitro group. Phthalocyanines were prepared by a statistical condensation of 4-nitro phthalonitrile and 1-{[(benzo-15-crown-5)-4′-yl]oxy}phthalonitrile in the presence of anhydrous metal salts. All the target unsymmetrical phthalocyanines were separated by column chromatography and characterized elemental analyses, ¹H NMR, IR, mass and UV–Vis spectral data. Electrochemical behaviors of Cu (II) phthalocyanine by cyclic voltammetry and differential pulse voltammetry techniques gave two common phthalocyanine ring reductions and one ring oxidation processes. Peak-to-peak separation of the processes II and III (388 mV) and the measure of gap (1.672 V) between the HOMO and LUMO for the complex, fits a phthalocyanine with electrochemically inactive metal center.     

碳-硅复合介孔磺酸催化剂的制备及其在缩醛(酮)反应中的应用

采用浸渍法将糠醇负载在铝改性的SBA-15介孔孔道中,经550℃不完全碳化制备了结构规整、含多苯环的中空管状硅碳复合介孔材料.结果表明,通过温和磺酸化作用可使磺酸基团成功取代在多苯环上,其酸量随着多苯环涂层厚度变化在0.38~0.84 mmol/g范围内可控调变.相比于蔗糖作为糖源的复合固体酸,所制碳多苯环-硅酸催化剂具有中空碳纳米管堆积的类似CMK-5介孔结构,以及较大的反应空间、稳定的机械性能、较高的比表面和大量可以接触的质子酸中心,因而在大分子缩醛(酮)反应中表现了良好的催化性能.     

A fundamental study on the fluorescence-quenching effect of nitro groups in tetraphenylethene AIE dyes with electron-withdrawing groups

A nitro group is a common fluorescence quencher, but its quenching efficiency can be easily affected by the surrounding environment. To date, there has been no systematic study on the effects of electronwithdrawing groups on the quenching efficiency of nitro groups. Herein, by virtue of experimental validation and theoretical calculations, we found that strong electron-withdrawing groups, such as pyridinium and dicyanovinyl groups, are detrimental to the quenching effect of nitro groups. Decreasing the electron-withdrawing ability could restore the nitro group's quenching effect.