Sodium borohydride reaction

Timko and Cram were the first to prepare true crown ethers containing the furanyl subcyclic unit ° . Destructive distillation of sucrose yielded 2-hydroxymethyl-5-formyl-furan 7 in 41% yield. This could be reduced to the corresponding diol in 91% yield by treatment with sodium borohydride. Reaction of the diol with tetraethylene glycol dito-sylate, and potassium t-butoxide in THE solution afforded the crown in 36% yield. The approach is illustrated below as Eq. (3.26). 

Sodium borohydride, reaction with ketones and aldehydes,... 

Two years later, the same group reported a formal synthesis of ellipticine (228) using 6-benzyl-6H-pyrido[4,3-f>]carbazole-5,ll-quinone (6-benzylellipticine quinone) (1241) as intermediate (716). The optimized conditions, reaction of 1.2 equivalents of 3-bromo-4-lithiopyridine (1238) with M-benzylindole-2,3-dicarboxylic anhydride (852) at —96°C, led regioselectively to the 2-acylindole-3-carboxylic acid 1233 in 42% yield. Compound 1233 was converted to the corresponding amide 1239 by treatment with oxalyl chloride, followed by diethylamine. The ketone 1239 was reduced to the corresponding alcohol 1240 by reaction with sodium borohydride. Reaction of the alcohol 1240 with f-butyllithium led to the desired 6-benzylellipticine quinone (1241), along with a debrominated alcohol 1242, in 40% and 19% yield, respectively. 6-Benzylellipticine quinone (1241) was transformed to 6-benzylellipticine (1243) in 38% yield by treatment with methyllithium, then hydroiodic acid, followed... 

Mechanisms of sodium borohydride reactions with primary, secondary, and tertiary amides have been investigated both at the B3LYP/6-31+- -G(d,p)//B3LYP/6-31G(d,p) and B3LYP/6-31++G(d,p)//HF/6-31G(d,p) levels of theory. The predicted structures of the key intermediates were then confirmed by experiment.317 For chemoselective reductions of a-substituted and aromatic esters with sodium borohydride, agreement between experimental results and theoretical computations at the B3LYP/6-31+-1-G(d,p)//HF/6-31G(d,p) levels of theory have been reported.318... 

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

Oxoselenazoline-4(7 )-carboxylic acid 89 and 2(iJ,6)-methylselenazolidine-4(/J)-carboxylic acid 90 were prepared from selenocysteine. Selenocysteine is prepared by reduction of selenocystine using sodium borohydride. Reaction of selenocysteine with l,T-carbonyldiimidazole affords 2-oxoselenazoline-4(R)-carboxylic acid 89 and reaction with acetaldehyde gives 2(R,6)-methylselenazolidine-4(R)-carboxylic acid 90 (Scheme 21) <2001BML2911>. 

Jacobs et al. (86) have compared the electronic substituent effect on the rate of sodium borohydride reduction vis a vis the LADH-catalyzed reduction (under transient-state kinetic conditions) for a series of para-substituted benzaldehydes. In contrast to the large electronic substituent effect observed in the sodium borohydride reaction (the rate ratio ftp-ci/ p-ocHs is 100), the LADH catalyzed reaction was found to show almost no electronic substituent effect ( p-ci/ p-ocHs —... 

Diacetone allose can be formed from diacetone glucose by first oxidizing die C-3 hydroxyl carbon with acetic anhydride in dimethylsulfoxide [101], followed by reduction with sodium borohydride (reaction 4.95). The reduction forms exclusively the allose configuration. 

What reagents could you use to convert this alcohol back to butanal Hint. The sodium borohydride reaction in the previous Exercise is NOT reversible and is considered a reduction of butanal. 

Chemical Hydrides Chemical hydrides are manufactured hydrogen-containing materials that are chemically reacted with water, releasing heat and hydrogen gas. The hydrogen release process occurs upon a hydrolysis reaction with water. For example, the sodium borohydride reaction is [9]... 

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 alkaline conditions of the reduction with aqueous sodium borohydride leads to competitive reactions of the OH nucleophile, but the product usually obtained from a thiazolium salt (195) is the corresponding thiazolidine (196). 

Sodium borohydride reduces esters but the reaction is too slow to be useful Hydrogenation of esters requires a special catalyst and extremely high pressures and tern peratures it is used m industrial settings but rarely m the laboratory... 

Sodium borohydride has also been used to reduce aryl diazonium salts m reductive deam mation reactions... 

Fluoroalkjiations are frequentiy performed indirectly using tandem reactions. Arenes react with sodium borohydride in trifluoroacetic acid to afford otherwise difficult to obtain l,l,l-trifluoro-2,2-diarylethanes. Presumably sodium borohydride reacts initially with the trifluoroacetic acid to produce the trifluoroacetaldehyde or its equivalent, which rapidly undergoes Friedel-Crafts-type condensation to give an intermediate carbinol. The carbinol further alkylates ben2ene under the reaction conditions giving the observed product. The reaction with stericaHy crowded arenes such as mesitylene and durene... 

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). 

Although there is Httle toxicity information pubHshed on hydrides, a threshold limit value (TLV) for lithium hydride in air of 25 fig/has been established (52). More extensive data are available (53) for sodium borohydride in the powder and solution forms. The acute oral LD q of NaBH is 50-100 mg/kg for NaBH and 50-1000 mg/kg for the solution. The acute dermal LD q (on dry skin) is 4-8 g/kg for NaBH and 100-500 mg/kg for the solution. The reaction or decomposition by-product sodium metaborate is slightly toxic orally (LD q is 2000-4000 mg/kg) and nontoxic dermally. 

The chain-growth catalyst is prepared by dissolving two moles of nickel chloride per mole of bidentate ligand (BDL) (diphenylphosphinobenzoic acid in 1,4-butanediol). The mixture is pressurized with ethylene to 8.8 MPa (87 atm) at 40°C. Boron hydride, probably in the form of sodium borohydride, is added at a molar ratio of two borohydrides per one atom of nickel. The nickel concentration is 0.001—0.005%. The 1,4-butanediol is used to solvent-extract the nickel catalyst after the reaction. 

The relationships among the various streptovaricins were shown by the following reactions streptovaricin E (8) converts to streptovaricin C (6) upon treatment with sodium borohydride streptovaricins A (4), G (9), and K (11) yield the same triacetate derivative upon acetylation streptovaricins B (5), C (6), and J (10) yield the same tri- and tetraacetate derivatives upon acetylation streptovaricin G (9) converts to streptovaricin (12) upon treatment with base (4). The open-chain streptovaricin U (13) has also been isolated from the streptovaricin complex (5). 

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. 

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