Sodium borohydride hydrolysis

The catalyst system was obtained by the electroplating of a Co-Ni-P film on a Cu sheet. The film had amorphous morphology. NiSO concentration in the bath affected the deposition rate and catalytic activity of the catalyst system. The optimum value was 0.01 M for NiSO concentration. At this condition, hydrogen production rate was observed as 3636 mL min Bcataiyst 30°C. The activation energy was 38 kJ mol Hor sodium borohydride hydrolysis in the presence of Co-Ni-P catalyst film. Films had two distinct areas which were outer spherical particles and inner layer. These areas depended on NiSO, concentration. Increase in NiSO, concentration led to a decrease in the outer spherical catalyst particles and micro-cracks. It was concluded that catalysts production inner layer increased whereas catalyst production on the outer particles decreased. NiSO concentration increase led to an increase in Ni and P amount in the catalyst composition. However, Co amount decreased. At the optimum concentration that is 0.01 M NiSO, the composition was 80.5 at% Co, 5.0 at% Ni and 14.5 at% P. Above this point, the deposition rate increased but catalytic activity decreased [58]. Therefore, it was demonstrated that better compositional configurations should be investigated. 

Kojima et al. investigated a wide variety of catalyst carriers and active metals for sodium borohydride hydrolysis. They reported platinum predpitated onto UCo02 to be the most active formulation [100]. 

The chrysanthemyl derivative (481) has been shown to yield artemisyl and santolinyl compounds directly upon buffered hydrolysis, and this in vitro result has been presented as evidence concerning the biogenesis of these non-head-to-tail terpenoids from trans-chrysanthemyl precursors. Hydrolysis of (482) and (483) shows that head-to-head synthesis of monoterpenoids is possible from both cyclopropyl and cyclobutyl precursors. In the presence of a hydride donor such as sodium borohydride, hydrolysis of (483) gives (484) and (485) and other products in benzene-pyridine, the products are (486) and... 

Sodium borohydride hydrolysis in aqueous solution can be represented in terms of the overall stoichiometric equation (Eq. 11.1) where NaBFLj reacts with 4 molecules of water to produce 4 molecules of H2 [33]. Although the reaction of NaBH4 hydrolysis has been studied since the discovery of sodium borohydride by Stock in 1933 [34], the theoretical, calculated energy of the reaction is often cited in an incompatible manner to the application, and real experimental data are very scarce [35-38]. The thermodynamic features of the catalyzed hydrolysis in fact are not yet well understood, as the evolved energy depends on the physical state and the hydration degrees of borohydride and metaborate and on-side reactions. 

In this preparation, phenyi-2-nitropropene is reduced to phenyl-2-nitropropane with sodium borohydride in methanol, followed by hydrolysis of the nitro group with hydrogen peroxide and potassium carbonate, a variety of the Nef reaction. The preparation is a one-pot synthesis, without isolation of the intermediate. 

The mechanism of lithium aluminum hydride reduction of aldehydes and ketones IS analogous to that of sodium borohydride except that the reduction and hydrolysis... 

Sodium borohydride and potassium borohydride [13762-51 -1] are unique among the complex hydrides because they are stable in alkaline solution. Decomposition by hydrolysis is slow in water, but is accelerated by increasing acidity or temperature. 

The importance of hydrolysis potential, ie, whether moisture or water is present, is illustrated by the following example. In the normal dermal toxicity test, namely dry product on dry animal skin, sodium borohydride was found to be nontoxic under the classification of the Federal Hazardous Substances Act. Furthermore, it was not a skin sensitizer. But on moist skin, severe irritation and bums resulted. 

Industrial Synthetic Improvements. One significant modification of the Stembach process is the result of work by Sumitomo chemists in 1975, in which the optical resolution—reduction sequence is replaced with a more efficient asymmetric conversion of the meso-cyc. 02Lcid (13) to the optically pure i7-lactone (17) (Fig. 3) (25). The cycloacid is reacted with the optically active dihydroxyamine [2964-48-9] (23) to quantitatively yield the chiral imide [85317-83-5] (24). Diastereoselective reduction of the pro-R-carbonyl using sodium borohydride affords the optically pure hydroxyamide [85317-84-6] (25) after recrystaUization. Acid hydrolysis of the amide then yields the desired i7-lactone (17). A similar approach uses chiral alcohols to form diastereomic half-esters stereoselectivity. These are reduced and direedy converted to i7-lactone (26). In both approaches, the desired diastereomeric half-amide or half-ester is formed in excess, thus avoiding the cosdy resolution step required in the Stembach synthesis. 

Another viable method for the synthesis of L-foUc acid (1) starts from 6-formylpterin (23). The diester of L-glutamic acid (24) is condensed with 6-formylpterin (23). Reduction of the Schiff base with sodium borohydride is followed by hydrolysis to yield L-foUc acid (37). 

FIGURE 10.10 The reaction of tridated sodium borohydride with the aspartyl phosphate at the active site of Na, K -ATPase. Acid hydrolysis of the enzyme following phosphorylation and sodium borohydride treatment yields a tripeptide containing serine, homoserine (derived from the aspartyl-phosphate), and lysine as shown. The site of phosphorylation is Asp" in the large cytoplasmic domain of the ATPase. 

In a similar vein, acylation of the corticoid 50 with furoyl chloride gives the diacyl derivative 51. Reduction with sodium borohydride serves to convert the 11-ketone to the alcohol 52. Hydrolysis under mild acid conditions preferentially removes the acyl group at the less hindered 21 position. The hydroxyl group in that derivative (53) is then converted to the mesylate 54. Replacement by chlorine affords mometasone (55) [12]. 

Then we discovered that the addition of 2% of a cobalt salt to pellets of sodium borohydride caused rapid hydrolysis with liberation of hydrogen. 

The seleno derivative 1374, which can be readily prepared by reduction of di-phenyldiselenide with sodium borohydride then alkylation with chloromethyltri-methylsilane, is alkylated to 1375 to give, on oxidative hydrolysis, aldehydes 1376 in high yields, PhSe02H-H20 1377 [104], and 7 (Scheme 8.44). Alkylation of the commercially available methyl thiomethyl sulfoxide 1378 leads to mono- or dialkyl... 

Amides can also be deacylated by partial reduction. If the reduction proceeds only to the carbinolamine stage, hydrolysis can liberate the deprotected amine. Trichloroac-etamides are readily cleaved by sodium borohydride in alcohols by this mechanism.237 Benzamides, and probably other simple amides, can be removed by careful partial reduction with diisobutylaluminum hydride (see Section 5.3.1.1).238... 

Oxidative conversion of palmatine, berberine, and coptisine to polycarpine, polyberbine, and its analog was described in Section II,B. These products were further transformed to aporphine alkaloids having a phenolic hydroxyl group at C-2 in the bottom ring (55). Hydrolysis with concomitant air oxidation of polyberbine (66) furnished 3,4-dihydrorugosinone, which was further air-oxidized in ethanolic sodium hydroxide to give rise to rugosinone (501) (Scheme 105). Successive reduction of the enamide 68 with lithium aluminum hydride and sodium borohydride afforded a mixture of ( )-norledecorine and (+ )-ledecorine (502). N-Methylation of the former with formaldehyde and sodium borohydride led to the latter. 

The structure of narlumidine (119) was established by Dasgupta et al. (117,119) on the basis of spectral data, particularly by comparison with spectra of bicucullinine (108), and also on chemical grounds. On hydrolysis followed by oxidation-methylation, narlumidine (119) was converted to ester 147, which was also obtained from 108 by N.O-methylation. Sodium borohydride reduction gave lactone 145, identical to the lactone obtained from 108. 

Another classic reaction of pyridinium salts is reduction of the pyridine ring. Donohoe and co-workers reported the partial reduction of A-alkylpyridinium salts <060BC1071>, which is accompanied by subsequent alkylation and hydrolysis to furnish a range of 2,3-dihydropyrid-4-ones. This sequence has the potential to introduce a variety of functional groups at the C-2 position of 2,3-dihydropyrid-4-ones. Reduction of pyridinium ylides with sodium borohydride has also been reported in fair to good yields <06JHC709>. 

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