Sodium borohydride, hydroperoxide

SOD see Superoxide dismutase Sodium, zeolite Na-Y photooxygenation, 870-4, 885-6, 887 Sodium borohydride, hydroperoxide determination, 687, 690, 691, 692 Sodium hypochlorite, aUyhc hydroperoxides, 673... 

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. 

The nucleophiles that are used for synthetic purposes include water, alcohols, carboxylate ions, hydroperoxides, amines, and nitriles. After the addition step is complete, the mercury is usually reductively removed by sodium borohydride, the net result being the addition of hydrogen and the nucleophile to the alkene. The regio-selectivity is excellent and is in the same sense as is observed for proton-initiated additions.17... 

Several alkenyl hydroperoxides have been successfully cyclized to five-, six- and seven-membered ring peroxides (equation 241).38s 388 Alkaline sodium borohydride reduction of these mercurials is frequently accompanied by epoxide or cyclic ether formation. 

Compound 403 is readily reduced with sodium borohydride at -78°C and yields the monoalcohol 405 (115). It also reacts with potassium t -butyl hydroperoxide at -20°C and gives the cis-enone-perester carbonate 406 in high yield (116). This last transformation can be explained by retro-Claisen fragmentation of intermediate 407 followed by the elimination of methoxide ion from 408. It is also possible that 407 undergoes a direct stereoelectronically controlled Grob type fragmentation to compound 406. 

Alkyl hydroperoxides. Peroxymercuration of alkenes proceeds cleanly and in good yield. These products previously were reduced to the desired alkyl hydroperoxides with alkaline sodium borohydride. This reduction proceeds in reasonable yield in the case of terminal alkenes, but scission to form epoxides of the original alkene predominates among products from nonterminal alkenes. This difficulty is now overcome by use of tri-n-butyltin hydride for reduction.18... 

Trichophylline, a novel alkaloid isolated from the roots of Catharanthus trichophyllus, has the structure 131, according to X-ray crystal structure analysis (145). Reduction of trichophylline with sodium borohydride gives an unsaturated lactone, formulated as 132. Oxidative fission of the C/D ring system in vincadifformine derivatives has been observed previously hence, trichophylline may arise by oxidation at C-21 of an appropriate precursor, such as a 19-hydroxytabersonine (88) or 108, to the hydroperoxide 133, followed by fission of the 20,21-bond and simultaneous migration of C-18. 

For each solvent, aldehyde and hydroperoxide reductions via the A-26, IRA-400, XE-279, and IRA-458 borohydride-form resins were investigated. Amorphous sodium borohydride and tetraethylammonium borohydride were used for comparison. Studies were run at both ambient temperature and at 45°C. Percent hydride of each resin was determined immediately prior to use. 

COBALT (7440-48-4) An extreme fire hazard. Pyrophoric particles or dust can self-ignite in air. Violent reaction with acetylene, ammonium nitrate, bromine pentafluoride, bromine trifluoride, cumene hydroperoxide, hydrogen peroxide (90%), nitryl fluoride, organic peroxides forms explosive mixture with potassium chlorate. Incompatible with sodium borohydride. Capable of promoting the decomposition of many organic materials. 

A general synthesis for all diastereomeric L-hexoses, as an example for monosaccharides that often do not occur in the chiral pool, has been worked out. The epoxidation of allylic alcohols with tertiary butyl hydroperoxide in presence of titanyl tartaric ester catalysts converts the carbon-carbon double bond stereose-lectively to a diol and is thus ideally suited for the preparation of carbohydrates. The procedure is particularly useful as a repetitive two-carbon homologiza-tion in total syntheses of higher monosaccharides and other poly hydroxy compounds. It starts with a Wittig reaction of a benzylated a-hydroxy aldehyde with (triphenylphosphoran-ylidene)acetaldehyde to produce the olefinic double bond needed for epoxidation. Reduction with sodium-borohydride... 

Alkenes may be transformed into an allyl hydroperoxide which, upon reduction (e.g. by sodium borohydride), yields an allylic alcohol (Eq. 2-7). In living systems, the formation of lipid peroxides is believed to be involved in some serious diseases and malfunctions including arteriosclerosis and cancer. 

Beckman et al (1994) used normal-phase HPLC of constituent hydroxy fatty acids followed by GC/MS analysis to reveal that the oxidized GPL in the skin of CDi mice, following application of the tumour-promoter phorbol esters, were oxidized derivatives of linoleic acid, including 9- and 13-hydroxyoctadecadienoic acids (9- and 13-HODE). Sodium borohydride reduction increased product yield by approximately 50%, suggesting the additional presence of GPL hydroperoxides in the oxidized lipids. 

From Frankel et al (1990) average analyses by preparative HPLC and by C-NMR of the isomeric hydroxyoctadecadienoate derivatives obtained by sodium borohydride reduction of the purified hydroperoxides. 

Analytical conditions Hydroperoxide isomeric mixtures from autoxidized methyl linoleate are reduced to hydroxydiene derivatives by sodium borohydride, and separated by preparative TLC on plates coated with silica gel treated with UV marker and developed with diethyl ether-hexane (6 4, v/v) and UV active hydroperoxides are eluted with diethyl ether. The dienol isomers are separated by HPLC on a preparative 6 m porous silica column with ethanol-hexane (0.5 99.5, v/v) as mobile phase with a UV detector set at 234 nm. The weight percent composition is based on the weight of each fraction collected. 

Hydroperoxy fatty acids as such cannot be separated by GC as they decompose at high temperatures, and HPLC is probabiy the preferred method for their anaiysis [168], Nonetheiess, there are times when it is advantageous to convert them to the hydroxy derivatives by means of sodium borohydride reduction and then to the TMS ethers for GC anaiysis, for exampie for identification by GC-mass spectrometry products derived from linoleic [223,341,911,946,1005], arachidonic [124,407,568, 1005] and docosahexaenoic acids [948] have been examined in this way (the list is not intended to be comprehensive). Woollard and Mallet [1005], in particular, have presented a comprehensive list of ECL data for compounds of this type. In addition, GC methods were used for the determination of the absolute configuration of hydroperoxides formed by lipoxygenase reaction [124,568,947]. 

It is well known that traces of hydroperoxides are present in commercial tetrahydrofuran. They are formed during the storage of the solvent under light. The best method for purifying tetrahydrofuran is redistillation over calcium hydride or sodium borohydride under nitrogen. 

Oxidation of -)-trans 41 with f-butyl hydroperoxide in die presence of 5% selenium dioxide on silica gel (42) in dioxane, followed by reduction of the resulting mixture of (-)-trans 51 and the overoxidized aldehyde [i-)-trans 53] with sodium borohydride, afforded the (-)-( )-hydroxymelhyl compound [(-)-trans 51]. Similarly, (+)-trms 41 was converted to the (+)-( )-hydroxymethyl compound [(+)-rramalgamated zinc in methanolic hydrochloric acid afforded (-)- and (+) norchanoclavine I (5 5), respectively, which were then converted to the (-)- and (,+)-trans methyl carbamates (57) by reaction with methyl chlm-oformate. 

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