Copper borohydride, preparation

Since sodium borohydride usually does not reduce the nitrile function it may be used for selective reductions of conjugated double bonds in oc,/l-un-saturated nitriles in fair to good yields [7069,1070]. In addition some special reagents were found effective for reducing carbon-carbon double bonds preferentially copper hydride prepared from cuprous bromide and sodium bis(2-methoxyethoxy)aluminum hydride [7766], magnesium in methanol [7767], zinc and zinc chloride in ethanol or isopropyl alcohol [7765], and triethylam-monium formate in dimethyl formamide [317]. Lithium aluminum hydride reduced 1-cyanocyclohexene at —15° to cyclohexanecarboxaldehyde and under normal conditions to aminomethylcyclohexane, both in 60% yields [777]. 

Reduction of cuprous chloride with sodium borohydride gives copper hydride which is a highly selective agent for the preparation of aldehydes from acyl chlorides [775]. 

The oxazolidin-2-ones 53 (R = H=CCH=CH2 or COEt) are obtained in a one-pot reaction of amino alcohol carbamates 52 with sodium hydroxide, followed by allyl bromide or propi-onyl chloride (94TL9533). A modified procedure for the preparation of chiral oxazolidin-2-ones 56 from a-amino acids 54, which avoids the hazardous reduction of the acids with borane and the intermediacy of water-soluble amino alcohols, is treatment of the methyl ester of the amino acid with ethyl chloro-formate to give 55, followed by reduction with sodium borohydride and thermal ring-closure of the resulting carbamate f95SC561). The 2-prop-ynylcarbamates 57 (R = Ts, Ac, Bz, Ph or allyl) cyclize to the methyleneoxazolidinones 58 under the influence of silver cyanate or copper(I) chloride/triethylamine (94BCJ2838). 

In the preparation of handsheets, the NBS NBH furnish was soaked for 2 h in 0.0005% Ca(OH)2 solution prior to the beating step. The pulp was then beaten in deionized water containing sodium borohydride (0.1% pulp weight) and 0.02% calcium hydroxide or 2.5% calcium carbonate (22). A Craftool Hollander laboratory beater was employed. Handsheets were prepared with a Noble and Wood brass sheet-making machine, which had been painted to prevent the contact of pulp with brass. The metal wire was overlaid with polyester fiber screening (75 mesh). Handsheets were also prepared from the same pulp furnish with the Noble and Wood brass sheet-forming machine before it had been painted. These papers had a copper content of 150 ppm as a result of contamination from the brass. 

Bis(triphenyiphosphine)copper(I) tetrahydroborate (55), readily prepared from cuprous chloride, triphenylphosphine and sodium borohydride in chloroform-ethanol solution, reduces aliphatic and aromatic acid chlorides to the corresponding aldehydes in good yields (Eq. 121) The ideal solvent is acetone, and in most cases. 

There are many examples of borohydride compounds of these metals, e.g., Cu, Ag, Zn and Cd-BH as neutral and anionic complexes in which the mode of bonding of BH is dependent on the coordination number of the metaP. Higher borane anions also combine with Cu and Ag, yielding both neutral and anionic complexes. Although no borohydrides of Au are isolated, treatment of Au-halide complexes with, e.g., NaBH, is a standard method for the preparation of Au-cluster compounds Copper(I) hydride, first reported in 1844, has the ZnS structure [d(Cn-H) = 0.173 nm (1.73 A) d(Cu-Cu) = 0.289 nm (2.89 A)] and decomposes to the elements when heated. At >100°C the decomposition is explosive. 

Incorporation of copper chloride in about 10% of the molar quantity of nickel before the borohydride reduction step further improved the selectivity of the Ni(B) catalysts. Copper improves the selectivity of Raney nickel catalysts in phenylacetylene semihydrogenation but not to the extent obtained using the copper-modified Ni(B) catalysts. The Cu-Ni(B) catalysts were more selective than the Cu(B) catalysts prepared by the borohydride reduction of copper chloride. Adding zinc or iron salts to a Ni(B) catalyst had only a slight effect on phenylacetylene semihydrogenation selectivity. ... 

Dehydrooenation 1,4-Benzoquinone. Chloranil. o-Chloranil. Copper chromite. Copper-Chromium oxide. Diethyl azodicarboxylate. 2,3-Dichloro-3,6-dicyano-I,4-benzoquinone. DIphenylpIcrylhydrazyl, N-Lithioethylenediamlne. Mercuric acetate. Nickel catalyst. Oleic add, Palladium. Perbenmic acid. Potassium l-butoxide. Pyrldinium hydrobromide per-bramlda, Balinlum. Selenium dioxide. Sodium borohydride. Sulfdr (sm 1,2-Naphthalic anhydridli preparation). Tetracyanoethylene. Thionyl chloride. Trityl perchlorate. 

An improved method for the preparation of methyl 2-oxo-5-vinyl-cyclopen-tanecarboxylate (389) by treatment of dimethyl ( )-2-hexenedioate (390), with the cuprate made from vinyllithium and copper(I) cyanide (77-85%), led to a short synthesis of mitsugashiwalactone (391) (Scheme 34), another noriridoid isolated from Boschniaka rossica Borohydride reduction and dehydration gave methyl 5-vinyl-l-cyclopentenecarboxylate (392), and this could be cyclized by hydroboration and extended treatment with hydrogen peroxide—conditions for the highest yield in the cyclization seem to be with hydroboration in base— then a separate acid-catalyzed cyclization. The methyl group was added with lithium dimethyl cuprate. ... 

The reduction of metal salts with borohydride or trialkylborohydride is a widely used colloid synthesis method. The preparation of platinum microcrystals having a mean diameter of 28 A by the reduction of chloroplatinic add with sodium borohydride has been reported as a reprodudble standardized preparation. [52] PVP stabilized copper sols have been prepared by borohydride reduction of copper salts. [53, 54] In some cases, however, the formation of metal... 

Colloidal copper, prepared by borohydride reduction of copper(II) salts in the presence of protective polymers and with particle sizes of 5.0-15.0 nm (depending on preparation details), is an active catalyst for the hydration of unsaturated nitriles to their corresponding unsaturated amides with 100% selectivity. [53, 268] The copper particle size was unaffected by the catalytic process. The catidyst performance was optimized in a detailed study of the effects of polymer molecular weight, polymer/metal ratio, and the chemical constitution of the polymer. [268, 269]... 

Colloids of alloys have been made by the chemical reduction of the appropriate salt mixture in the solution phase. Thus, Ag-Pd and Cu-Pd colloids of varying composition have been prepared by alcohol reduction of mixtures of silver nitrate or copper oxide with palladium oxide (Vasan and Rao 1995). Fe-Pt alloy nanocrystals have been made by thermal decomposition of the Fe and Pt acetylac-etonates in high-boiling organic solvents (Sun et al. 2000). Au-Ag alloy nanocrystals have been made by co-reduction of silver nitrate and chloroauric acid with sodium borohydride (Sandhyarani et al. 2000 He et al. 2002). 

Recently, a novel graphene-copper nanoparticle composite was prepared by the in situ chemical reduction of a mixture containing graphene oxides and copper(II) ions using potassium borohydride as a reductant. It was mixed with paraffin oil and packed into one end of the fused capillary to fabricate microdisk electrodes for sensing carbohydrates [14]. The results indicated that copper nanoparticles with an average diameter of 20.8 nm were successfully deposited on the graphenes to form a well-interconnected hybrid network. 

The transfonnations of gm-dihalocyclopropanes are synthetically useful because the cyclopropanes are readily prepared by the addition of dihalocarbene to olefins. In most of dehalogenation reactions to monohalocyclopropanes, the reagents are limited to metallic reductants such as organotin hydride, lithium aluminum hydride, sodium borohydride, Grignard reagent, and zinc-copper couple [1-9]. A versatile method for the reduction of gm-dibromocyclopropanes 3 with an organic reductant is achieved by use of diethyl phosphonate (commercially named diethyl phosphite) and triethylamine to give the monobromocyclopropanes 4 (Scheme 2.2) [10]. 

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