First Report for the Efficient Reduction of Oximes to Amines with Zinc Borohydride in the form of (Pyridine)(tetrahydroborato)zinc Complex

(Pyridine)(tetrahydroborato)zinc complex, (Py)Zn(BH₄)₂, as a stable modification of zinc borohydride can easily reduce a variety of aromatic and aliphatic aldoximes or ketoximes to their corresponding amines in high to excellent yields in refluxing THF.     

AIPO4 Supported Zinc Borohydride as a Novel Reagent for the Hydration of Aromatic Alkenes and Alkynes

Hydration of aromatic alkenes (styrene, α-methylstyrene and E-stilbene) and alkynes (phenyl and diphenylacetylene) has been achieved by the reaction of the corresponding alkenes or alkynes on zinc borohydride combined with AIPO₄ in DME. Except in the case of α-methylstyrene, Zn(BH₄)₂/AIPO₄ provides a more efficient and selective catalytic system than the combination with SiO₂ or Al₂O₃.     

Calcium Borohydride

Calcium borohydride reduces both aliphatic and aromatic esters to alcohols completely in the presence of alkene catalysts. The intermediate borates formed during the reduction of aromatic esters are converted to aldehydes with aqueous NaOC1 in good yields.     

Zinc Powder Catalysed Formylation and Urealation of Amines Using CO2 as a C1 Building Block†

Transformation of CO₂ into valuable organic compounds catalysed by cheap and biocompatible metal catalysts is one of important topics of current organic synthesis and catalysis. Herein, we report the zinc powder catalysed formylation and urealation of amines with CO₂ and (EtO)₃SiH under solvent free condition. Using 2 mol% zinc powder as the catalyst, a series of secondary amines, both the aromatic ones and the aliphatic ones, can be formylated into formamides. When primary aromatic amines were used as the substrates, the reactions produce urea derivatives. The electronic and steric effects from the substrates on the formylation and urealation reactions were observed and discussed. The recovery and reusability of zinc powder were investigated, showing the zinc powder can be reused in the formylation reaction without loss of catalytic activity. The analysis on the reactants/products mixture after filtering out the zinc powder showed the zinc concentration in the mixture is low to 1 ppm. The pathways for the formylation and urealation of amines with this catalytic system were also investigated, and related to the different substrates.     

Efficient Reduction of Aryl Azides and Aryl Nitro Compounds to Their Corresponding Amines with Sulfurated Calcium Borohydride CA(BH2S3)2. A New Modified Borohydride Agent

Ca(BH₂S₃)₂ is easily prepared by metathetical reaction between NaBH₂S₃ and CaCl₂ in THF. Ca(BH₂S₃)₂ is much more stable than NaBH₂S₃ therefore, is a more practical reagent. Sulfurated calcium borohydride can easily reduce aryl nitro and aryl azido functions to their amines in high yields in refluxing THF. Reduction of nitro groups is accompanied with regioselectivity. Very high chemoselectivity is also observed for the reduction of an azido functional group in the presence of nitro functionality.     

Synthesis,characterization, and application of monodisperse gelatin-stabilized silver nanospheres in reduction of aromatic nitro compounds

Monodisperse colloidal silver nanospheres were synthesized by the reaction of silver nitrate, hydroxylammonium hydrosulphate (NH₂OH)₂ · H₂SO₄ and sodium hydroxide in the presence of gelatin as stabilizer. Colloidal nanospheres were characterized by UV-vis absorption spectroscopy, transmission electron microscopy, X-ray diffraction and dynamic light scattering. X-ray diffraction data confirmed that the silver nanospheres were crystalline with face-centered-cubic structure. Transmission electron microscopy analysis revealed the formation of homogeneously distributed silver nanoparticles of spherical morphology and size of the nanoparticles was in the range of 0.7–5.2 nm. Silver nanospheres were stable for more than two months when stored at ambient temperature. Size and size distribution were studied by varying pH, reaction temperature, silver ion concentration in feed solution, concentration of reducing agent and concentration of the stabilizing agent. Catalytic activity of silver nanospheres was tested for the reduction reaction of nitro compounds in sodium borohydride solution. Monodisperse silver nanospheres showed excellent catalytic activity towards the reduction of aromatic nitro compounds. The reduction rate of aromatic nitro compounds had been observed to follow the sequence 4-nitrophenol > 2-nitrophenol > 3-nitrophenol.     

CeCl3-Catalyzed Reduction of Methyl Esters of Carboxylic Acids to Corresponding Alcohols with Sodium Borohydride

A wide range of methyl esters, including esters of aromatic carboxylic acids, alkenyl carboxylic acids, aliphatic carboxylic acids, and protected amino acids, were reduced to the corresponding alcohols with NaBH₄ in ethanol in the presence of a catalytic amount of CeCl₃. The reaction was completed within 24 h at ambient temperature and showed high functional group compatibility and chemoselectivity. With esters containing nitro, methoxyl, halogen, alkenyl, and protected amino functionalities, only the ester group was reduced. The alcohols were isolated after evaporation of the solvent and routine aqueous workup in good yields (75–95%).     

Reduction of Aldehydes and Ketones with Potassium Borohydride as Reductant

A series of aldehydes and ketones were reduced by potassium borohydride in an ionic liquid/water ([bmim]PF6/H2O) biphasic system to afford corresponding alcohol with high purity in excellent yields. The ionic liquid/water biphasic system could promote the chemoselectivity and the substituents such as nitro group and chlorine remained intact. Aromatic ketones were not as active as aromatic aldhydes and cyclic ketones owing to their higher steric hindrance. The ionic liquid could be recycled and reused. This protocol has notable advantages of no need of phase transfer catalyst and organic solvents, mild conditions, simple operation, short reaction time, ease work-up, high yields and recycling of the ionic liquid.     

Reduction of nitrobenzene derivatives using sodium borohydride and transition metal sulfides

Reported here is the reduction of aromatic nitro compounds using sodium borohydride and transition metal sulfides as catalysts. The reaction conditions were optimized using the reduction of nitrobenzene as a model reaction. The catalysts studied were iron sulfide (Fe₃S₄), copper sulfide (CuS), zinc sulfide (ZnS), cobalt sulfide (Co₃S₄), and nickel sulfide (NiS). The reduction was monitored using gas chromatography. Quantitative conversions were achieved using Co₃S₄ and NiS, representing a ten-fold increase in reactivity compared to the non-catalyzed reaction. Fe₃S₄ and ZnS had no apparent effect on the reduction of nitrobenzene while the reduction using CuS showed a marginal increase. The reduction method was applied to several aryl-nitro derivatives containing either electron-withdrawing or electron-donating groups. Halogen containing aryl-nitro compounds were reduced without dehalogenation. The reduction had no effect on other functional groups such as carboxylic acids, esters, amides, or alkenes, indicating that the reduction is highly chemoselective.     

Electron impact mass spectra of some tertiary aliphatic nitro compounds. Nitrocarbonyl compounds and some analogues

The mass spectra of some tertiary aliphatic nitroaldehydes, nitroketones, nitroesters, nitronitriles and related nitrocarbonyl compounds are discussed and compared with those of some analogous nitro compounds lacking the carbonyl function. The M⁺˙ ? NO₂˙ and in several cases M⁺˙ ? HNO₂ fragmentation seem to be the most characteristic features of all tertiary aliphatic nitro compounds. In the presence of the primary nitro group, the loss of NHO₂ is always observed.     

Poly-n-(Pyrazine)Zinc Borohydride as a New Stable,Efficient and Selective Reducing Agent

Coordination polymer of unstable zinc borohydride and pyrazine is prepared and used as an stable, efficient and selective bench top reducing agent for a variety of organic compounds.     

Application of Cu(Hdmg)2 as a simple and cost‐effective catalyst for the convenient one‐pot reductive acetylation of aromatic nitro compounds

In this article, we have developed a novel and simple one‐pot reductive acetylation of aromatic nitro compounds with sodium borohydride (NaBH₄) in ethyl acetate (EtOAc) under reflux conditions in the presence of the bis(dimethylglyoximato)copper(II) complex [Cu(Hdmg)₂] as an efficient and cost‐effective copper‐containing catalyst. Notably, using the above‐mentioned one‐pot reaction, the corresponding acetamide derivatives were obtained in high to excellent yields.     

Safe and Efficient Reductive Methylation of Primary and Secondary Amines Using N-Methylpyrrolidine Zinc Borohydride

An efficient, general procedure for reductive methylation of primary and secondary amines with 37% formaldehyde using N-methylpyrrolidine zinc borohydride (ZBHNMP) as a reducing agent gave the corresponding tertiary amines in excellent yields. The reaction was carried out in tetrahydrofuran under neutral conditions at 0–10 °C.     

Reactions in microemulsion media. Borohydride reduction of mono- and dicarbonyl compounds

Microemulsions were prepared at 26° from mixtures of hexanes (O), a 50: 1 (w/w) solution (W) of 0.1 M KOH-NaBH₄, and a 1.23:1 (w/w) mixture (S) of hexadecyltrimethylammonium bromide (HTABr) and 1-butanol. A pseudoternary phase map contained a significant microemulsion (μE) region, and μE's A and B (60:35:5 and 20:10:70 S:W:O, respectively) were used for reduction of several monocarbonyl compounds [benzophenone (1a), benzaldehyde (2a), acetophenone (3a), and 1-phenyl-1-octadecanone (4a)], an α,β-unsaturated ketone [trans-4-phenyl-3-buten-2-one (6a)], and a diketone [4-(4'-benzoylphenyl)-2-butanone (7a)]at 26°. For comparison purposes, reductions were also performed in aqueous 2-propanol (2-PrOH A and 2-PrOH B) prepared by the substitution of 2-propanol for the S and O components of μE's A and B. Generally, the reductions were slightly faster in the microemulsion media than in the corresponding aqueous 2-propanol media. The significantly slower reduction of 4a relative to that of 3a in μE B indicated that the interphase is the reactive site. With enone 6a, the influence of microemulsions on the competition between 1,2- and 1,4-reduction was determined. In μE's A and B there was 8% and ll% 1,4-reduction, respectively, whereas in 2-PrOH A and B there was only a trace. With diketone 7a, the reactivity of the aromatic carbonyl group relative to that of the aliphatic carbonyl group increased on going from 2-PrOH A and B to μE's A and B, respectively. For the sodium borohydride reduction of ketones, microemulsion catalysis is more effective than phase transfer catalysis or the use of a tetraalkylammonium borohydride in a hydrocarbon solvent.     

N-（4＇-取代嘧啶-2＇-基）-取代苯氧基磺酰脲的合成及除草活性

光谱;N-（4＇-取代嘧啶-2＇-基）-取代苯氧基磺酰脲的合成及除草活性     

O2‐Mediated Oxidation of Aminoboranes through 1,2‐N Migration

In analogy to the classical reaction of C?B bonds with peroxides, the first oxidative functionalization of aminoboranes through a 1,2‐N migration was realized. Readily available aliphatic nitro compounds are thereby transformed into N‐ and O‐functionalized hydroxylamines in a single synthetic operation. Addition of hazardous peroxides is avoided. Instead, the insertion of O₂, as the terminal oxidant, into Zn?C bonds provides the necessary peroxides. The required zinc organyls, in turn, are formed through a boron‐to‐zinc exchange, from an organoboronic ester byproduct of the nitro‐to‐aminoborane transformation.     

Deoxygenation of Acylferrocenes with Sodium Borohydride and Zinc Chloride

A mild procedure for the reductive deoxygenation of α-ferrocenyl aldehydes and ketones is reported using sodium borohydride and zinc chloride. The present method allows synthesis of alkylferrocenes containing functionalized tethers and is adaptable to large-scale preparations.     

p‐Nitro­phenyl isocyanide

Achiral p‐nitro­phenyl isocyanide, C₇H₄N₂O₂, crystallizes in the orthorhombic chiral space group P2₁2₁2₁. Attractive intermolecular interactions between the nitro O atoms and both aromatic H and nitro N atoms of neighbouring mol­ecules are observed. The O⋯N interaction is surprisingly strong [N⋯O = 2.869 (2) Å] compared with other aromatic nitro compounds.     

A Recyclable bi‐functional Luminescent Zinc (II) metal–organic framework as highly selective and sensitive sensing probe for nitroaromatic explosives and Fe3+ ions

By introducing carboxyl tag to the aromatic ligands system and borrowing the organic template open framework idea, a stable fluorescent Zn metal–organic framework was successfully prepared through a rigid ligand H₆L (3,5‐bis‐(3‐carboxyphenoxy)benzoic acid) under hydrothermal conditions. The selectivity and sensitivity of the Zn‐MOF to metal ions and nitro‐aromatic compounds (NACs) were investigated by fluorescence quenching. And the Zn‐MOF showed a high sensibility of nitro‐aromatic compounds (NACs) and Fe³⁺ ions, especially for 4‐(4‐nitropheny lazo) resorcinol (NPLR). More importantly, the detection limit of the Zn‐MOF for detecting NPLR solution was found to be 1.71 ppb. Moreover, this sensor is remarkable recyclable and is promisingly applied for rapid, on‐site and sensing of explosive residuals.     

Theoretical Study of the Mechanism of the Nitro-Nitrite Rearrangement and Its Role in Gas-Phase Monomolecular Decomposition of C-Nitro Compounds

Semiempirical, ab initio, and density functional theory calculations were used to study the primary act of gas-phase monomolecular decomposition of certain C-nitro compounds and their radical cations, associated with the nitro-nitrile rearrangement. It was shown that the reaction fails to occur with all neutral molecules of aliphatic nitro compounds (except for fluoronitromethane and fluoronitroethene) and has a much lower barrier with the corresponding radical cations. An important role of the nitro-nitrile rearrangement in gas-phase decomposition of aromatic nitro compounds was demonstrated.