Hydrogen from sodium borohydride

Sodium or potassium hydrogen sulfite reacts with several thiiranes to give disulfides of /3-mercaptosulfonic acid salts (76EGP122086). Potassium thiocyanate in dimethylformamide or aqueous ethanol isomerizes thiiranes (Scheme 84) (72CJC3930). 1,2-Dithiols are obtained by treatment of thiiranes with NaBH2S3 obtained from sodium borohydride and sulfur (73TL1401). 

CATALYTIC HYDROGENATION WITH HYDROGEN GENERATED FROM SODIUM BOROHYDRIDE 4 ... 

Fig. 2 Apparatus for hydrogenation with hydrogen generated from sodium borohydride.

Carboxylic acids are considerably less reactive than acid chlorides, aldehydes and ketones towards reduction. They cannot be reduced by catalytic hydrogenation or sodium borohydride (NaBH4) reduction. They require the use of a powerful reducing agent, e.g. LiAlH4. The reaction needs two hydrides (H ) from LiAlITj, since the reaction proceeds through an aldehyde, but it cannot be stopped at that stage. Aldehydes are more easily reduced than the carboxylic acids, and LiAltLj reduces all the way back to 1° alcohols. 

Sodium borohydride (160) was found to serve as a hydrogen donor in the asymmetric reduction of the presence of an a,pi-unsaturated ester or amide 162 catalyzed by a cobalt-Semicorrin 161 complex, which gave the corresponding saturated carbonyl compound 163 with 94-97% ee [93]. The [i-hydrogen in the products was confirmed to come from sodium borohydride, indicating the formation of a metal enolate intermediate via conjugate addition of cobalt-hydride species (Scheme 2.17). 

Reactions [Al] and [A2] show the steps of the chemical process used to extract energy from sodium borohydride. [Al] is the simple hydrolysis of sodium borohydride to form hydrogen gas [A2] is the oxidation of that hydrogen gas, either in a fuel cell or in an internal combustion engine. Reaction [A3] is the overall process, and is equal to the sum ofReactions [Al] and [A2]. 

The triamino- and 1,2-diamino-3-chlorocyclopropenylium ions 9 were transformed into the 2,3-diaminocyclopropeneselone 10 by reaction with sodium hydrogen selenide, which was prepared from sodium borohydride and selenium (see Section S.A.S.l.). ... 

Ni boride (obtained from sodium borohydride reduction of Ni acetate in ethanol) exhibits sensitivity to substitution on the double bond, and to strained double bonds , and hence is useful for selective half-hydrogenation of dienes. Ni boride selectively hydrogenates the strained double bond of norbonene and dicyclopentadiene. Thus, a synthesis of 13-santalene involves the selective saturation of the endocyclic double bond of 7 over Ni boride, to afford 8 in 98% yield ... 

Further evidence was obtained by an examination of the homogeneous alcohols derived from sodium borohydride reduction of the respective photoisomers. Since the hydride ion would enter from the most accessible side, XXXV was deduced for the relative stereochemistry of that part of the alcohol molecules. The NMR-spectra of the two alcohols were very similar, except that the N—H resonance was anomalously low in the -alcohol [8.60 ppm, compared with 6.68 ppm (y-alcohol), 6.36 ppm (/3-lumicolchicine), and 5.70 ppm (y-lumicolchicine)], suggesting the creation of a new intramolecular hydrogen bond. On extrapolation to infinite dilution, this resonance shifted much less than the corresponding one exhibited by the y-alcohol. This clearly indicated a strong NH—OH hydrogen bond, which is only possible if the OH and NH functions... 

A number of reagents derived from sodium borohydride by replacement of one or more of the hydrogen atoms by other groups allow more-selective reduction than with sodium borohydride itself. Among the most useful are sodium cyanoborohydride and sodium triacetoxyborohydride. 

The synthesis of several sulfonamidophenethanolamines, including sotalol, has been described previously (3). The synthesis of the sulfonamidophenethanolamine compounds relied upon firstly obtaining a 2-aminoacyIsulfonanilide precursor. The alcohol formed from the ketone precursor is via either palladium-catalyzed low-pressure hydrogenation or sodium borohydride chemical reduction (3). 

Ni (0) catalyst can be produced with the aid of plasma. The activation energy of hydrogen production from sodium borohydride with this catalyst system was calculated as 51.35 kj moT With this approach the mass specific surface area can be increased from 0.0063 m g to 23.11 m g without the crystal structure deteriorating. The reason is thought to be the higher resistivity of plasma treated Ni to aggregations. Plasma treatment can enhance... 

The Co-Co B and Ni-Ni B nanocomposite systems have been obtained by a chemical reduction method. It was found that Co-Co B had higher hydrogen production rate from sodium borohydride than Ni-Ni B which were 4300 and 3400 mL min respectively. Additionally, the Co-Co B... 

Co-Mo-Pd-B and Co-Pd-B can be obtained by the chemical reduction method of metal ions. Co-Mo-Pd-B had the highest catalytic reactivity among Co-B, Co-Mo-B and Co-Pd-B. It can be concluded that Mo enhanced the hydrogen production rate. Co-Mo-Pd-B had a 6023 mL min gcataiyst hydrogen production rate at 25°C whereas Co-Pd-B had a rate of 2920 mL min at 25°C from sodium borohydride. Also the... 

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