Sodium compounds hydride

A variation of the classical reductive amination procedure uses sodium cyanoboro hydride (NaBH3CN) instead of hydrogen as the reducing agent and is better suited to amine syntheses m which only a few grams of material are needed All that is required IS to add sodium cyanoborohydride to an alcohol solution of the carbonyl compound and an amine... 

The key intermediate 124 was prepared starting with tryptophyl bromide alkylation of 3-acetylpyridine, to give 128 in 95% yield (Fig. 37) [87]. Reduction of 128 with sodium dithionite under buffered (sodium bicarbonate) conditions lead to dihydropyridine 129, which could be cyclized to 130 upon treatment with methanolic HC1. Alternatively, 128 could be converted directly to 130 by sodium dithionite if the sodium bicarbonate was omitted. Oxidation with palladium on carbon produced pyridinium salt 131, which could then be reduced to 124 (as a mixture of isomers) upon reaction with sodium boro-hydride. Alternatively, direct reduction of 128 with sodium borohydride gave a mixture of compounds, from which cyclized derivative 132 could be isolated in 30% yield after column chromatography [88]. Reduction of 132 with lithium tri-f-butoxyaluminum hydride then gave 124 (once again as a mixture of isomers) in 90% yield. 

To circumvent this problem, several methods have been developed (157). Probably, the most prominent method is treatment with sodium boro-hydride (0.1% in PBS, 30 minutes prior to staining). NaBILi is known to neutralize Schiff s bases through reduction of amine-aldehyde compounds into nonfluorescent salts. 

Complex aluminum and boron hydrides can contain other cations. The following compounds are prepared by metathetical reactions of lithium aluminum hydride or sodium borohydride with the appropriate salts of other metals sodium aluminum hydride [55], magnesium aluminum hydride [59], lithium borohydride [90], potassium borohydride [9i], calcium borohydride [92] and tetrabutylammonium borohydride [95]. 

Cyclization of the acid chloride by means of aluminum chloride gives tetralone (19-2). This is then converted to its A -methylimine (19-3) by means of methylamine and titanium tetrachloride. That intermediate is next reduced with sodium boro-hydride to give a mixture of cis and trans aminotetralins (19-4). The tmns isomer tametraline (19-5) is separated by fractional crystallization of the hydrochloride salt [20]. Detailed pharmacological investigations showed that this compound owes its antidepressant action to the inhibition of reuptake of dopamine and norepinephrine from the synaptic cleft. 

Reduction of compounds 108 and 109 with an excess of sodium boro-hydride in oxolane respectively gave (5RS)-5-C-[(RS)-dimethoxyphos-phinylJ-D-xyfo-hexofuranoses 112 (21% yield) and the 5-C-[(RS)-(meth-oxy)phenylphosphinyl] compound 113 (70% yield). The phosphinate 113 was reduced with an excess of SDMA in oxolane at 0°, to give the 5-C-[(RS)-phenylphosphinyl] derivative (41% yield after purification by t.l.c.), which, on acid hydrolysis, yielded (75%) a mixture of 5,6-di-... 

Reduction of the 2-arylidene-3-hydroxy-2,3-dihydrobenzo[ ]thio-phenes (26 R = R =C1, and R = C1, R = H) with sodium boro-hydride affords mixtures of the cis and Irons alcohols (27).222 The cis-trans isomerism exhibited by a number of 2-arylidene-2,3-dihydro-benzo[6]thiophen-3-ones (e.g., 28) and by two compounds with the... 

Asymmetric reduction of a,/ -unsaturated carbonyl compounds using chiral complexes (Section 5.4.1, p. 521) could feasibly lead to optically active allylic alcohols. Other reducing agents which have some merit of regioselectivity, but not stereoselectivity, are sodium cyanoborohydride,244 and sodium boro-hydride in the presence of lanthanide salts.245... 

To complete the total synthesis of the optically active form of veatchine, the successful resolution of the synthetic racemic ketone 244 was accomplished. Compound 244 was reduced stereoselectively with sodium boro-hydride to give the alcohol 248. The latter was heated with succinic anhydride and pyridine in xylene to yield the racemic half-ester 249. Treatment of 249 with brucine afforded the diastereoisomeric brucine salts, which were separated by fractional crystallization. The separated salts were decomposed... 

Kraus and Greer1 originally prepared a few organotin hydrides with considerable difficulty from the reaction between an organotin sodium compound and ammonium bromide or ammonium chloride in liquid ammonia. Their procedure remained the only synthetic route to these compounds for some 25 years until 1947 when Finholt, Bond, Wilzbach, and Schlesinger2 obtained the methyltin hydrides in a more facile manner by reducing a mixture of the methyltin chlorides with lithium aluminum hydride (lithium tetrahydroaluminate). 

Potassium hydride, KH.—Moissan5 prepared the hydride by a method analogous to that employed by him for the corresponding sodium derivative, the excess of potassium being dissolved by liquid ammonia. Ephraim and Michel6 passed hydrogen into potassium at 350° C., and found the reaction to be promoted by the presence of calcium. The hydride forms white crystals of density 0-80. The vapour-tension for each temperature-interval of 10° between 350° and 410° C. corresponds with the values 56, 83, 120, 168, 228, 308, and 430 mm. respectively.7 In chemical properties potassium hydride resembles the sodium compound, but is less stable. Its stability is greater than that of rubidium hydride or caesium hydride. Carbon dioxide converts it into potassium formate. 

The most important compound is lithium aluminum hydride, LiAlHt, a nonvolatile crystalline solid, stable below 120°C, that is explosively hydrolyzed by water. In the crystal there are tetrahedral AlHf ions with an average A1H distance of 1.55 A. The Li+ ions each have four near hydrogen neighbors (1.88 - 2.00 A) and a fifth that is more remote (2.16 A). Lithium aluminum hydride is soluble in diethyl and other ethers and can be solubilized in benzene by crown ethers. In ethers, the Li+, Na+, and R4N+ salts of A1H and GaH4 tend to form three types of species depending on the concentration and on the solvent, namely, either loosely or tightly bound aggregates or ion pairs. Thus LiAlHt is extensively associated in diethyl ether, but at low concentrations in THF there are ion pairs. Sodium aluminum hydride (NaAlH) is insoluble in diethyl ether. 

Yamada, K., Itoh, N., and Iwakuma. T., One-pot conversion of Mannich bases via quaternary ammonium salts into the corresponding methyl compounds with sodium cyanoboro-hydride in HMPA, J. Chem. Soc. Chem. Commun.. 1089, 1978. 

The nature of the cation is unimportant in aqueous or other highly polar solutions of borohydrides, but influences the rate of reaction in isopropanol or pyridine, where the reagent exists mainly as associated ion-pairs [44]. Lithium borohydride is more reactive than the sodium compound in these solvents Li+ can probably associate more closely than Na+ with the carbonyl oxygen, promoting polarisation of the C=0 group, and so aiding hydride transfer from the anion. Other cations [e.g. Ca +j and solvents e.g. dimethylformamide) provide variations in reactivity which can have valuable uses for selective reduction of carbonyl groups [42]. 

Thio-D-xylopyranose has been the sugar of this type most thoroughly investigated. Its synthesis was reported in 1961, independently and simultaneously from three different laboratories. With sodium thiocyanate, l,2-0-isopropylidene-5-0-p-tolylsulfonyl-a-D-xylofuranose (211) gives a thiocyanate that reacts with sodium sulfide to give l,2-0-isopropylidene-5-thio-a-D-xylofuranose (212). A better synthesis is the treatment of 211 with sodium thiosulfate, followed by reduction of the resultant Bunte salt with sodium boro-hydride. The same compound 212 is obtained by nucleophilic replacement of the 5-sulfonyloxy group in 211 by treatment with potassium thioacetate followed by deacetylation to 212, or by the reaction of 211 with sodium a-toluenethioxide, followed by scission of the resultant S-benzyl compound with sodium in liquid ammonia. 

Bogdanovic, B., Brand, R., Marjanovic, A., Schwickardi, M., Tolle, J. (2000). Metal-doped sodium aluminium hydrides as potential new hydrogen storage materials. /. Alloys Compounds 302,36-58. 

In the laboratory, alkenes are often hydrated by the oxymercura-tion procedure. When an alkene is treated with mercurydl) acetate [Hg(02CCH3)2, usually abbreviated HgOAclal in aqueous tetrahydrofuran (THF) solvent, electrophilic addition to the double bond rapidly occurs. The intermediate organomercury compound is then treated with sodium boro-hydride, NaBH4, and an alcohol is produced. For example ... 

Alkene oxymercuration is closely analogous to halohydrin formation. The reaction is initiated by electrophilic addition of (mercuric) ion to the alkene to give an intermediate mercurinium ion, whose structure resembles that of a bromonium ion (Figure 7.5). Nucleophilic attack of water, followed by loss of a proton, then yields a stable organomercury addition product. The final step, reaction of the organomercury compound with sodium boro-hydride, is not fully understood but appears to involve radicals. Note that... 

---