Carbonyl compounds reaction with sodium borohydride

Compound 63, the 2-formyl derivative of compound 61, undergoes a series of side-chain reactions at the carbonyl group including reduction with sodium borohydride and condensation reactions with hydroxylamine or malononitrile. The reactions afford the appropriately 2-substituted products in excellent yields <2004CHE1477>. 

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... 

Arenetellurolates, ethenetellurolates, and alkanetellurolates prepared by reduction of diorgano ditellurium compounds with sodium borohydride in ethanol, THF/ethanol, or DMSO add to acetylenes in regioselective and iran.y-stereoselcctive reactions to produce aryl ethenyl tellurium products either predominantly or exclusively as (Z)-isomers. The yields are almost always higher than 70%. In reactions with acetylenic aldehydes, ketones, carboxylic acids, and esters the arenetellurolate becomes bonded to the carbon atom in a [i-position to the carbonyl group. 

When o bonds act as nucleophiles, the electrons also have to go to one end of the c bond as they form a new bond to the electrophile. We can return to an earlier example, the reaction of sodium borohydride (NaBH4) with a carbonyl compound, and complete the mechanism. In this example, one of the atoms (the hydrogen atom) moves away from the rest of the BH4 anion and becomes bonded to the carbonyl compound. 

Poly(4-vinylpyridine) boran has b n used as a reducing agent for carbonyl compounds This polymeric reducing agent was prepared by the reaction of poly(4-vinylpyridinium hydrochloride) with sodium borohydride. 

Cyclopropyl trimethylsilyl ethers, which were readily prepared from aldehydes, ketones and esters, coupled with alkenes on treatment with mercury(II) acetate and, after reduetion with sodium borohydride, afforded chain-extended carbonyl compounds, e.g. 37, in moderate to good yields. The whole reaction could be carried out in one pot. 

It has been found possible to construct the 1,4-benzothiazine ring by direct interaction of bis-(2-aminobenzene) disulfide (96) with carbonyl compounds.139,140 The reaction is most efficient when conducted under a nitrogen atmosphere with a 1 1 ratio of reactants otherwise, the principle products are benzothiazoles. While reduction of the benzothiazine 97 with sodium borohydride gives a stable dihydro derivative, the unsaturated benzothiazines themselves were prone to autoxidation, giving rise to benzothiazoles and benzothiazine sulfoxides.141... 

Reaction media. While alcoholic solvents are used in conventional reduction of carbonyl compounds with sodium borohydride, they can be replaced with hexane if alumina or silica geF is added (heterogeneous conditions). In a refluxing mixture of DME and methanol, NaBH4 reduces methyl methoxybenzoates to the corresponding benzylic alcohols.- Stereoselectivity changes are observed in the reduction of 2-substituted cyclohexanones when conducted in DMSO. ... 

Michael addition to (+)-pu]egone [( + )-12] is not only possible with carbon nucleophiles, but also nitrogen and sulfur compounds. Thus, reaction of (+)-pulegone with benzylamine, followed by reduction of the carbonyl group with sodium borohydride, gives (1 / .3/ ,4,S )-8-(ben-zylamino)menthol (24)28, used for the formation of chiral 1.3-oxazines which react with Grignard reagents diastereoselectively (Section D. 1.3.1.4.). 

The oxy-Cope rearrangement of hexa-l,5-dien-3-ols to give Se-unsaturated carbonyl compounds often gives low yields because of the high temperatures that are needed to elfect the reaction. However, in the presence of mercury tri-fluoroacetate, the reaction proceeds at room temperature and the required Se-unsaturated carbonyls (93) are obtained bydemercuration of the intermediates (92) with sodium borohydride in good yield ( 60%). Nakai and his co-workers... 

There have been a few reports on the simple route to enamidines offerred by the Peterson reaction. Lithiation of a-silyl amidines such as 66 with Bu Li and subsequent Peterson reaction with carbonyl compounds gives the corresponding enamidines 67 (Scheme 2.42) [106,107). The enamidines 67 are converted to the amines by treatment with sodium borohydride in ethanol under slightly acidic conditions. These entire homologation processes can be performed without purification of the enamidine intermediates 67. 

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