Sodium borohydride Subject

Morpholiaoglucopyranosides have beea syathesized from sucrose by selective lead tetraacetate oxidatioa of the fmctofuranosyl ring to a dialdehyde (6). This product was subjected to reductive amination with sodium borohydride and a primary amine such as benzylamine to produce the /V-henzy1morpho1ino derivative (7) (99). 

When the furanones 110 (R = Ph, p-MeOC6H4, p-Cl—C6H4) were subjected to reduction using sodium borohydride, neither the glycols 111 nor the allyl alcohols 112 were formed. Instead, the corresponding 4-(arylmethylene)-2,3-(4//,5// )-furandiones 113 were obtained (Scheme 34) (86JHC199). 

Renaut et al. elaborated a synthetic route to linearly fused oxadiazoloquinazoles <2000S2009>. These authors reported that the Ar-oxide carbamate 361 can be subjected to ring closure to the unsaturated cyclized product 362 under fairly forcing conditions (220 °C, 0.1 Torr). Much milder reaction conditions are needed, however, to carry out a reductive cyclization treatment of 361 in ethanol in the presence of sodium borohydride (at 50°C) gave rise to the partially reduced product 363 in nearly quantitative yield. 

On studying the KDO content of LPS from Xanthomonas sinensis, Volk and coworkers64 found that only one KDO residue per LPS chain is present in this organism. Moreover, the authors observed the formation of 4,7- and 4,8-anhydro derivatives (39 and 40) of KDO (see Scheme 14) under the conditions used for mild hydrolysis of the LPS with acetic acid. Free KDO was also shown to yield the anhydro derivatives under analogous conditions. The structures of these unusual side-products were identified by mass spectrometry, as follows. Reduction of 39 and 40 with sodium borohydride gave the two epimeric mixtu.es, 41 and 42. These were subjected to periodate treatment followed by borohydride reduction, the products separated by paper electrophoresis, and their trimethylsilyl ether derivatives analyzed by... 

Reactivity. Chemicals that react violently with air or water are considered hazardous examples are sodium metal, potassium metal, and phosphorus. Reactive materials also include strong oxidizers such as perchloric acid, and chemicals capable of detonation when subjected to an initiating source, such as solid, dry < 10% H2O picric acid, benzoyl peroxide, or sodium borohydride. Solutions of certain cyanide or sulfides that could generate toxic gases are also classified as reactive. The potential for finding such chemicals in a refinery is... 

When subjected to mercury acetate the ynone 78 underwent a 5-endo-dig cyclization and after work-up with aqueous sodium chloride, furnished the pyrrolinones 79 and 80 in a ratio of 89/11. The mixture of pyrrolinones was reduced directly with sodium borohydride to the iST-Boc-pyrrolidinol 81 which was obtained as a single diastereoisomer. Reduction of the carbamate with lithium aluminum hydride gave (+)-preussin (2) in 37% overall yield. 

A very short and elegant synthesis of the 16-rtiembered dilactone ( )-pyrenophorin (515) has been accomplished by the dipolar cycloaddition reaction of a trialkylsilyl nitronate (81TL735). Nitromethane was added to 3-buten-2-one and the carbonyl group of the product reduced with sodium borohydride. The nitro alcohol (511) was converted to the acrylate (512) which was then subjected to a dimerization-cyclization reaction by treatment with chlorotrimethylsilane and triethylamine in dry benzene. Hydrogenation of the mixture of isoxazoline products (513) over palladium on charcoal followed by double dehydration of the intermediate bis-/3-hydroxyketone (514) led to ( )- and meso-pyrenophorin (Scheme... 

The reaction may be subject to limitations in the alkene structure similar to those of the nitrile process. Besides simple amides, one can also utilize urea and urethanes in this reaction. Demercuration is best effected by using alkaline sodium borohydride in the presence of a primary amine such as Bu"NH2. 

Singh and Mehrotra [79] have published the synthesis of spiro-(3-lactams 24 (Scheme 7) by the reaction of 2-diazo-l,2-diphenylethanone 22 with 2-phenylimi-noacenaphthenone 23 in refluxing benzene. These compounds were further subjected to reduction with sodium borohydride which afforded spiro-(3-lactams 25. This study has also revealed that the carbonyl group in the spiro-(3-lactams 24 have... 

In the total synthesis of reserpine, Woodward and collaborators (10) have reported that the quaternary iminium salt J8 was reduced with aqueous metha-nolic sodium borohydride to methyl 0-acetyl isoreserpate 09). This is the anticipated product whether the stereochemical sense of the reaction is subject to steric or thermodynamic control as pointed out by Woodward. It is also the expected one on the basis of stereoelectronic control. 

Secondary amines can be prepared from the primary amine and carbonyl compounds by way of the reduction of the derived Schiff bases, with or without the isolation of these intermediates. This procedure represents one aspect of the general method of reductive alkylation discussed in Section 5.16.3, p. 776. With aromatic primary amines and aromatic aldehydes the Schiff bases are usually readily isolable in the crystalline state and can then be subsequently subjected to a suitable reduction procedure, often by hydrogenation over a Raney nickel catalyst at moderate temperatures and pressures. A convenient procedure, which is illustrated in Expt 6.58, uses sodium borohydride in methanol, a reagent which owing to its selective reducing properties (Section 5.4.1, p. 519) does not affect other reducible functional groups (particularly the nitro group) which may be present in the Schiff base contrast the use of sodium borohydride in the presence of palladium-on-carbon, p. 894. 

In the reactions discussed and exemplified above, reactants, transient species and products are related by linear sequences of elementary reactions. The transient species can be regarded as a kinetic product and, if isolable, subject to the usual tests for stability to the reaction conditions. Multiple products, however, may also occur by a mechanism involving branching. Indeed, the case shown earlier in Fig. 9.5b, where the transient is a cul de sac species, is the one in which the branching to the thermodynamic product P and kinetic product T occurs directly from the reactant. In the absence of reversibility, the scheme becomes as that shown in Scheme 9.8a, where the stable products P and Q are formed as, for example, in the stereoselective reduction of a ketone to give diastereoisomeric alcohols. The reduction of 2-norbornanone to a mixture of exo- and cndo-2-norbornanols by sodium borohydride is a classic case. The product ratio is constant over the course of the reaction and reflects directly the ratio of rate constants for the competing reactions. The pseudo-first-order rate constant for disappearance of R is the sum of the component rate constants. 

Some metals, for example, arsenic and selenium, are difficult to analyze by atomic absorption because their analytical wavelengths are subject to considerable interference. These metals, however, are readily converted to gaseous hydrides by treatment with strong reducing reagents such as sodium borohydride. Since the hydrides can be readily separated from the sample matrix, interferences are much reduced. A typical hydride generation AAS is... 

The viscous oily product was dissolved in ethanol and after adding to the solution an excess amount of sodium borohydride, the mixture was stirred at room temperature followed by distilling off ethanol under reduced pressure. The residue was dissolved in ethyl acetate and the ethyl acetate layer recovered was washed with water, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to provide a viscous oily product. The product was subjected to a silica gel column chromatography and eluted using benzene and then a mixture of benzene and ethyl acetate of 10 1 by volume ratio to provide 5- l-hydroxy-2-[N-benzyl-2-(2-... 

To 1.17 g of (-)-7,8-difluoro-2,3-dihydro-3-hydroxymethyl-4H-[l,4] benzoxazine was added 2.77 g of thionyl chloride in pyridine. The reaction mixture was concentrated and the concentrate was subjected to column chromatography using 40 g of silica gel and eluted with chloroform to obtain 1.18 g of the reaction product as a colorless oily product. This product was dissolved in 30 ml of dimethyl sulfoxide, and 0.41 g of sodium borohydride was added thereto, followed by heating at 80-90°C for 1 hour. The reaction mixture was dissolved in 500 ml of benzene, washed with water to remove the dimethyl sulfoxide, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The concentrate was subjected to column chromatography using 40 g of silica gel and eluted with benzene to obtain 0.80 g of (-)-7,8-difluoro-2,3-dihydro-3-methyl-4H-[l,4]benzoxazine as a colorless oily product [a]D25 = -9.6° (c = 2.17, CHCI3). Optical Purity >99% e.e. 

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