Sodium borohydride as reducing agent

Although electrothermal atomisation methods can be applied to the determination of arsenic, antimony, and selenium, the alternative approach of hydride generation is often preferred. Compounds of the above three elements may be converted to their volatile hydrides by the use of sodium borohydride as reducing agent. The hydride can then be dissociated into an atomic vapour by the relatively moderate temperatures of an argon-hydrogen flame. 

Alkyl arsenic compounds - Electron capture or flame ionisation Use of sodium borohydride as reducing agent prior to GLC 0.21 pg L [683, 704- 720]... 

A useful method for the reductive conversion of elemental tellurium into Te anions employs complex hydrides such as sodium or potassium borohydride and tetraalkyl ammonium borohydride as reducing agents. 

A very useful variant of the hydrazone reduction is the deoxygenation of aldehydes and ketones via the hydride reduction of tosylhydrazones (Caglioti reaction) The method is mild, convenient and widely applicable. While sodium borohydride was used in the earlier procedures, considerable improvements have been achieved through the uses of sodium cyanoborohydride, catecholborane, diborane, his-benzoyloxy borane and copper borohydride as reducing agents and HMPA, DMF, sulpholane, etc. as solvents. Use of the sterically crowded 2,4,6-triisopropyl tosylhydrazone derivative has greatly facilitated the reduction in some cases (equations 61-64). ... 

Sodium borohydride reductions of gold(I) complexes give Au clusters at RT if sodium borohydride in ethanol is dropped slowly into a suspension of the Au(I) complex in the same solvent. The immediate coloring of the reaction mixture (mostly red), even after only a few drops of the borohydride have been added, indicates fast formation of Au clusters. In view of the complicated composition of these compounds the fast formation is surprising. The use of H2 and CO with HjO as reducing agents in the synthesis of gold clusters has been described (see Table 1, Method A, 8.2.2.2). 

Alkylborohydrides are also used as reducing agents. These compounds have greater steric demands than the borohydride ion and therefore are more stereoselective in situations in which steric factors come into play.72 These compounds are prepared by reaction of trialkylboranes with lithium, sodium, or potassium hydride.73 Several of the compounds are available commercially under the trade name Selectrides .74... 

The oxymercuration reaction of various 2-substituted 1,4-benzodioxin derivatives 35 in the presence of a suspension of mercuric acetate in water/THF followed by treatment in situ with sodium chloride and then with sodium borohydride as a reducing agent provided in excellent yields the expected hemiketals 36 (Scheme 2) <1997X2061 >. 

In recent years, inorganic hydrides such as lithium aluminum hydride, LiAlH4, and sodium borohydride, NaBH4, have become extremely important as reducing agents of carbonyl compounds. These reagents have considerable utility, especially with sensitive and expensive carbonyl compounds. The reduction of cyclobutanone to cyclobutanol is a good example, and you will... 

While the demercuration of (3-acyloxymercurials has not received much attention, sodium borohydride or alkaline sodium borohydride have been most widely employed for this task. Hydrolysis to the corresponding alcohol or reversion to alkene are significant side reactions, however, and they are sensitive to the solvent used.4991500 Sodium amalgam and tri-n-butyltin hydride501 have also been utilized as reducing agents. 

Sodium borohydride or dimethyl amine borane have found limited use as reducing agents because of expense. In addition, bath stability, plating rate, and deposit properties are inferior to those of formaldehyde-reduced baths. The deposit is a copper—boron alloy. Copper—hypophosphite baths have been investigated, but these are poorly autocatalytic, and deposit only very thin coatings. 

Early examples of catalytic radical cyclizations were provided by Okabe and coworkers, who subjected 2-bromoethyl propargyl ethers or bromoacetaldehyde propargyl acetals 257 to complex 255 as a catalyst and sodium borohydride as the stoichiometric reducing agent (Fig. 63, Table 5, entry 1) [307, 308]. 

Dialkyl and diaryl ditellurium compounds are easily reduced to tellurols and tellurolates. Alkali metals in liquid ammonia or in an inert organic solvent, sodium borohydride in methanol, ethanol, alcohol/benzene, THF, DMF, or in a basic aqueous medium, lithium aluminum hydride in dioxane or THF/hexamethylphosphoric triamide, and thiourea dioxide in THF/50% aqueous sodium hydroxide have been used as reducing agents (p. 164). The tellurolates are easily oxidized in air. For this reason they are almost always used in situ. 

Sodium borohydride (NaBH4), a relatively mild reducing agent, reduces epoxides only sluggishly except for nitro epoxides. In the mixed solvent f-butyl alcohol and methanol, sodium borohydride can reduce aryl-substituted epoxides, terminal epoxides and cyclohexene oxide, to the corresponding alco-hols. The regiochemistry of this reaction is nearly the same as that with LAH. For example the reduc-... 

A number of chemicals are used as reducing agents. The most common chemicals used for reduction of chromium are sulfur dioxide, sodium metabisulfite, sodium bisulfite, and ferrous salts. Other reducing agents used or which can be potentially used for water and wastewater treatment include sodium borohydride to reduce ionic mercury to metallic mercury and alkali metal hydride to alter the chemical form of lead so that it can be precipitated and also to recover silver. The common chemicals used as reducing agents are discussed on the following sections. 

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