Borohydride, sodium compounds

The nitrated model compound, 9, proved even more resistant to reduction than the polymeric analog the dissolving metal technique used to reduce 15 failed on 9, but finally the amino model, 10, was produced by treatment of with a 25-fold excess of sodium borohydride. Compound 1 serves as a difunctional initiator for NCA polymerization. 

Also reported in Scheme 24 are the PhSeBr promoted cyclization reactions of alkenyl aldimines described by De Kimpe [93,94]. As indicated by the reactions of 158 and 161, both, the 5-exo-trig and the 5-endo-trig cyclizations, can take place. The initially formed iminium salts 159 and 162 are converted into the corresponding pyrrolidines 160 and 163 by reduction with sodium borohydride. Compound 163 was obtained as an almost equimolecular mixture of two diastereomers. 

Radicals can also be synthesized by the reduction of alkylmercury salts. For example, in the presence of sodium borohydride, compound 5-2 reacts to form the radical, 5-3. 

The 7V-(o-aminobenzyl)pyrrolidine 267 (n = 0) was obtained from the pyrrolo[2,l-i>]quinazolines 124 and 186 with sodium borohydride. Compounds 330 were also prepared from 205 by reduction with lithium aluminum hydride. - - - When reduction was carried out with sodium borohydride, only the C=N bond was saturated and compounds 332 were formed. The carbonyl group of compounds of type 332 was reduced by lithium aluminum hydride to give compounds of type 330. The C=N bond of compounds of type 333 could not be reduced with sodium borohydride or by catalytic hydrogenation over palladium or Raney nickel. The methoxycarbonyl group of the pyrrolo[2,l-i>]quinazolone 334 was reduced to a hydroxymethyl group with lithium aluminum hydride in tetra-hydrofuran at... 

Compound A is a D-aldopentose. When treated with sodium borohydride, compound A is converted into an alditol that exhibits three signals in its C NMR spectrum. Compound A undergoes a Kiliani-Fischer synthesis to produce two aldo-hexoses, compounds B and C. Upon treatment with nitric acid, compound B yields compound D, while compound C yields compound E. Both D and E are optically active aldaric acids. 

The hydride is thus delivered to the ketone from the upper face and the resulting hydroxyl functionahty rests on the lower side of the ring. The solution to this problem proved to be straightforward. Prior to the addition of sodium borohydride compound 84 was treated with sodium hydroxide. The resulting carboxylate anion would experience Coulomb repulsion with the borohydride reagent and attack will occur preferentially from the opposite side of the carboxylate. Indeed, this concept proved to work out nicely, delivering diastereomer 87 as the only observable product. The synthesis was carried on to a common intermediate of thromboxane synthesis. 

Sodium borohydride and lithium aluminum hydride react with carbonyl compounds in much the same way that Grignard reagents do except that they function as hydride donors rather than as carbanion sources Figure 15 2 outlines the general mechanism for the sodium borohydride reduction of an aldehyde or ketone (R2C=0) Two points are especially important about this process... 

The elements listed in the table of Figure 15.2 are of importance as environmental contaminants, and their analysis in soils, water, seawater, foodstuffs and for forensic purposes is performed routinely. For these reasons, methods have been sought to analyze samples of these elements quickly and easily without significant prepreparation. One way to unlock these elements from their compounds or salts, in which form they are usually found, is to reduce them to their volatile hydrides through the use of acid and sodium tetrahydroborate (sodium borohydride), as shown in Equation 15.1 for sodium arsenite. 

Hydrazine—borane compounds are made by the reaction of sodium borohydride and a hydrazine salt in THF (23,24). The mono-(N2H4 BH ) and di-(N2H4 2BH2) adducts are obtained, depending on the reaction conditions. These compounds have been suggested as rocket fuels (25) and for chemical deposition of nickel—boron alloys on nonmetallic surfaces (see Metallic COATINGS) (26). 

When an aqueous effluent stream containing organomercurials cannot be recycled, it may be treated with chlorine to convert the organomercury to inorganic mercury. The inorganic compounds thus formed are reduced to metallic mercury with sodium borohydride. The mercury metal is drained from the reactor, and the aqueous solution discarded. The process utilising sodium borohydride is known as the Ventron process (27). 

With mercuric acetate (Hg(OOCCH2)2), olefins and / fZ-butyl hydroperoxide form organomercury-containing peroxides (66,100). The organomercury compound can be treated with bromine or a mild reducing agent, such as sodium borohydride, to remove the mercury. 

AletalHydrides. Metal hydrides can sometimes be used to prepare amines by reduction of various functional groups, but they are seldom the preferred method. Most metal hydrides do not reduce nitro compounds at all (64), although aUphatic nitro compounds can be reduced to amines with lithium aluminum hydride. When aromatic amines are reduced with this reagent, a2o compounds are produced. Nitriles, on the other hand, can be reduced to amines with lithium aluminum hydride or sodium borohydride under certain conditions. Other functional groups which can be reduced to amines using metal hydrides include amides, oximes, isocyanates, isothiocyanates, and a2ides (64). 

Reduction. Quinoline may be reduced rather selectively, depending on the reaction conditions. Raney nickel at 70—100°C and 6—7 MPa (60—70 atm) results in a 70% yield of 1,2,3,4-tetrahydroquinoline (32). Temperatures of 210—270°C produce only a slightly lower yield of decahydroquinoline [2051-28-7]. Catalytic reduction with platinum oxide in strongly acidic solution at ambient temperature and moderate pressure also gives a 70% yield of 5,6,7,8-tetrahydroquinoline [10500-57-9] (33). Further reduction of this material with sodium—ethanol produces 90% of /ra/ j -decahydroquinoline [767-92-0] (34). Reductions of the quinoline heterocycHc ring accompanied by alkylation have been reported (35). Yields vary widely sodium borohydride—acetic acid gives 17% of l,2,3,4-tetrahydro-l-(trifluoromethyl)quinoline [57928-03-7] and 79% of 1,2,3,4-tetrahydro-l-isopropylquinoline [21863-25-2]. This latter compound is obtained in the presence of acetone the use of cyanoborohydride reduces the pyridine ring without alkylation. 

Isoquinoline also forms Reissert compounds when treated with benzoyl chloride and alkyl cyanide (28), especially under phase-transfer conditions (29). The W-phenylsulfonyl Reissert has been converted to 1-cyanoisoquinoline with sodium borohydride under mild conditions (154). When the AJ-benzoyl-l-alkyl derivative is used, reductive fission occurs and the 1-alkyLisoquinoline is obtained. 

The reducing agents generally used in bleaching include sulfur dioxide, sulfurous acid, bisulfites, sulfites, hydrosulfites (dithionites), sodium sulfoxylate formaldehyde, and sodium borohydride. These materials are used mainly in pulp and textile bleaching (see Sulfur compounds Boron compounds). 

Pyridoxal Derivatives. Various aldehydes of pyridoxal (Table 3) react with hemoglobin at sites that can be somewhat controlled by the state of oxygenation (36,59). It is thereby possible to achieve derivatives having a wide range of functional properties. The reaction, shown for PLP in Figure 3, involves first the formation of a Schiff s base between the amino groups of hemoglobin and the aldehyde(s) of the pyridoxal compound, followed by reduction of the Schiff s base with sodium borohydride, to yield a covalendy-linked pyridoxyl derivative in the form of a secondary amine. 

Methyl borate is beheved to be the boric acid ester produced in the largest quantity, approximately 8600 metric tons per year (28). Most methyl borate is produced by Morton International and used captively to manufacture sodium borohydride [16940-66-2]. Methyl borate production was studied in detail during the 1950s and 1960s when this compound was proposed as a key intermediate for production of high energy fuels. Methyl borate is sold as either the pure compound or as the methanol azeotrope that consists of approximately a 1 1 molar ratio of methanol to methyl borate. 

Sodium Tetrahydroborate, Na[BH ]. This air-stable white powder, commonly referred to as sodium borohydride, is the most widely commercialized boron hydride material. It is used in a variety of industrial processes including bleaching of paper pulp and clays, preparation and purification of organic chemicals and pharmaceuticals, textile dye reduction, recovery of valuable metals, wastewater treatment, and production of dithionite compounds. Sodium borohydride is produced in the United States by Morton International, Inc., the Alfa Division of Johnson Matthey, Inc., and Covan Limited, with Morton International supplying about 75% of market. More than six million pounds of this material suppHed as powder, pellets, and aqueous solution, were produced in 1990. 

Synthesis. The parent compound, bora2iae [6569-51-3] is best prepared by a two-step process involving formation of B-trichlorobora2iQe followed by reduction with sodium borohydride. These reactions have been studied ia some detail (96). 

Electroless nickel—boron baths use sodium borohydride or dimethylamine borane [74-94-2] in place of sodium hypophosphite (see Boron compounds). The nickel—boron aHoy is brittle, highly stressed, and much more expensive than nickel—phosphoms aHoys. Nickel—boron is mainly used to replace gold in printed circuit board plating. 

Cationic rings are readily reduced by complex hydrides under relatively mild conditions. Thus isoxazolium salts with sodium borohydride give the 2,5-dihydro derivatives (217) in ethanol, but yield the 2,3-dihydro compound (218) in MeCN/H20 (74CPB70). Pyrazolyl anions are reduced by borohydride to pyrazolines and pyrazolidines. Thiazolyl ions are reduced to 1,2-dihydrothiazoles by lithium aluminum hydride and to tetrahydrothiazoles by sodium borohydride. The tetrahydro compound is probably formed via (219), which results from proton addition to the dihydro derivative (220) containing an enamine function. 1,3-Dithiolylium salts easily add hydride ion from sodium borohydride (Scheme 20) (80AHC(27)151). 

Hydroxymethylferrocene has been made by condensing ferrocene with N-methylformanilide to give ferrocenecarboxalde-hyde, and reducing the latter with lithium aluminum hydride, sodium borohydride, or formaldehyde and alkali. The present procedure is based on the method of Lindsay and Hauser. A similar procedure has been used to convert gramine methiodide to 3-hydroxymethylindole, and the method could probably be used to prepare other hydroxymethyl aromatic compounds. 

A complex of 9-BBN with MMA can be formed and compounded with sodium borohydride [92], Derivatives from the combination of 9-BBN with fatty acid or fatty alcohol give an initiator with improved stability [93], Stability appears to improve with increasing molecular weight, so oligomeric and polymeric analogs... 

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