Sodium borohydride acid with

Vinylamines (enamines) are reduced by alane, mono- and dichloroalane to saturated amines, and hydrogenolyzed to amines and alkenes [710]. Reduction is favored by dichloroalane while hydrogenolysis is favored by alane. Alane, chloroalane and dichloroalane gave the following results with -N-pyrrolidinylcyclohexene V-pyrrolidinylcyclohexane in 13, 15 and 22% yield, and pyrrolidine and cyclohexene in 80, 75 and 75% yields, respectively [710]. Saturated amines were also obtained by treatment of enamines with sodium borohydride [711], with sodium cyanoborohydride [103, 712] (Procedure 22, p. 210) and by heating for 1-2 hours at 50-70° with 87% or 9S% formic acid (yields 37-89%) [320]. 

Deamination studies have aided attempts to locate the positions of the O-sulfate groups in heparin. From the results of deamination and periodate-oxidation studies, it was concluded239 that half of the uronic acid residues are sulfated at C-2, and sequential periodate oxidation, reduction with sodium borohydride, acid treatment, and deamination gave 2,5-anhydro-D-mannose 6-sulfate.240,241 Sulfated O-(hexosyluronic acid)-2,5-anhydro-D-mannose and sulfated uronic acids were subsequently isolated, and the isolation (in 65% yield) of the disulfated 0-(idosyluronic acid)-2,5-anhydro-D-mannose (137) from heparin, together with the 13C n.m.r. spectra of 137 and heparin, suggested243 that at least two thirds of the heparin structure consists of the repeating unit 138. 

Sodium borohydride reacts with Lewis acids in nonprotic solvents to yield diborane [19287-45-7], B2H6 (18), which can then be used to generate other useful organoboranes such as amine boranes, alkyl boranes, and boron hydride clusters. 

Isosorbide (3) and isomannide (4) act as chiral auxiliaries for the sodium borohydride reduction of some prochiral ketones optical yields of up to 20% were achieved. It seems that the isohexides form chiral complexes with sodium borohydride, whereby the chiral information is transferred to the substrate.219 Optical active alcohols were obtained by reduction of appropriate ketones with sodium or lithium borohydride in the presence of isosor-bide.219 Asymmetric reduction of propiophenone using sodium borohydride, modified with (+)-camphoric acid and isosorbide, resulted in C -phenylethylcarbinol in 35% enantiomeric excess.2,9b... 

Reduction of amides. Sodium borohydride combined with methanesulfonic acid in DMSO reduces amides to the corresponding amines in 60-90% isolated yield. I he system also reduces acids and esters to primary alcohols. These reductions have been conducted with lithium aluminum hydride and with borane-tetrahydrofurane (5,48),2 hut with somewhat different selectivities. This new reagent, however, appears to be less hazardous than the latter reagent. 

Sodium. Slow reaction with anhydrous acid explosive reaction with aqueous acid.28 Sodium Borohydride. Reaction with concentrated sulfuric acid to yield diborane may... 

Enantioselective reduction of ketones.1 Sodium borohydride aged with L-tar-taric acid can effect enantioselective reduction of ketones bearing an a-substitueut... 

Prelab Exercise Calculate the volume of hydrogen gas generated when 3 mL of 1 M sodium borohydride reacts with concentrated hydrochloric acid. Write a balanced equation for the reaction of sodium borohydride with platinum chloride. Calculate the volume of hydrogen that can be liberated by reacting 1 g of zinc with acid. 

A suspension of sodium borohydride is essentially inert to chiral amino alcohols and is unable to reduce ketoxime O-alkyl ethers. On the other hand, when combined with a Lewis acid (e.g., ZrCb), sodium borohydride reacts with chiral amino alcohols with evolution of hydrogen to form a chiral borohydride reagent. This chirally modified borohydride has the ability to reduce the C —N double bond of ketone O-alkyl ethers to give chiral primary amines in 78-95% yield with 43-90% ee34. 

In two separate routes the aminoepoxides were obtained by highly stereoselective methods. Chlorination of iV -benzoylquinotoxine (5) with iV -chlorodiisopropylamine in 100% phosphoric acid in the dark gave an amorphous mixture of the epimeric a-chloroketones 85 and 86 (Scheme 8) [10). Reduction with sodium borohydride or with lithium tri-i-butoxyaluminum hydride afforded stereoselectively a mixture of the threo chlorohydrins 87 and 88. Treatment of 87 and 88 with aqueous potassium hydroxide at 20°C gave smoothly a mixture of the erythro iV-benzoylepoxides 89 and 90. The benzoyl groups were removed reductively with diisobutylaluminum hydride to give the aminoepoxides 81 and 82 which were cyclized in refluxing toluene-methanol (100 1). This reaction yielded 9-ep -quinine (12) and 9-epi-quinidine (13) in a ratio of 2 1. The overall yield of 12 and 13 from 87 and 88 was 50%. Only traces of the erythro products quinine and quinidine were observed. 

Diselenanes (27) are available through the reactions of 1,3-propanediselenols with aldehydes and ketones in the presence of a Lewis acid such as zinc(II) chloride (Equation (3)) <85T4793, 93TL8517>. The diselenols are normally synthesized from the corresponding diselenocyanates by reduction with, for example, sodium borohydride, or with sodium in liquid ammonia <71BSB639>. 

CHROMIC ACID, DI-fert-BUTYL ESTER (1189-85-1) A strong oxidizer. Violent reaction with reducing agents, alcohols, combustible materials, ethers, fluorine, hydrazine, powdered metals, including aluminum, magnesium, zirconium, potassium iodide, sodium tetraborate, sodium tetraborate decahydrate, sodium borohydride. Incompatible with water, steam. 

Sodium borohydride is less active but has the property of reducing aldehydes, ketones, and peroxides, and a number of other commonly encountered impurities. Aldehydes are eliminated from acetic acid and other lower monocarboxylic acids by refluxing with sodium or potassium dichromate solution and fractionation. Alcohols and esters for use as UV solvents may be treated with sodium borohydride or with 2,4-dinitrophenylhydrazine before distilling, to remove aldehydes and ketones. 

The silylenol ether formed from (47) and trimethylchlorosilane was cyclized in situ, and the reaction mixture was worked up under acidic conditions to give the ketone (558). This was subjected to reduction with sodium borohydride, acid-catalyzed elimination of water, and oxidation with dichlorodicyanobenzoquinone (DDQ) to give the bicyclic ester (560). Introduction of a methoxy substituent into the retinoid structure (560) was likewise effected via the ketone (558). When this ketone was ketalized with methyl o-formate, methanol was eliminated and the product was oxidized, its six-membered ring system undergoing aromatization to form a substituted phenyl group. 

Treating a benzene suspension of sodium borohydride (4 equiv.) With glacial acetic acid (3.25 equiv.) And refluxing the mixture for 15 min under nitrogen, after the initial rapid gas evolution subsided (ca. 3 mol of Hz liberated) [No Smoking ], gave a clear solution of NaBH(OAc)3. ... 

The enzyme is a single enantiomer of a chiral molecule and binds the coenzyme and substrate m such a way that hydride is transferred exclusively to the face of the carbonyl group that leads to (5) (+) lactic acid Reduction of pyruvic acid m the absence of an enzyme however say with sodium borohydride also gives lactic acid but as a racemic mixture containing equal quantities of the R and S enantiomers... 

The structure of the bicychc monoterpene borneol is shown in Figure 26 7 Isoborneol a stereoisomer of borneol can be prepared in the labora tory by a two step sequence In the first step borneol is oxidized to camphor by treatment with chromic acid In the second step camphor is reduced with sodium borohydride to a mixture of 85% isoborneol and 15% borneol On the basis of these transformations deduce structural formulas for isoborneol and camphor... 

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