Sodium borohydride purification

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. 

Greater selectivity in purification can often be achieved by making use of differences in chemical properties between the substance to be purified and the contaminants. Unwanted metal ions may be removed by precipitation in the presence of a collector (see p. 54). Sodium borohydride and other metal hydrides transform organic peroxides and carbonyl-containing impurities such as aldehydes and ketones in alcohols and ethers. Many classes of organic chemicals can be purified by conversion into suitable derivatives, followed by regeneration. This chapter describes relevant procedures. 

This group of reagents is commercially available in large quantities some of its members - notably lithium aluminium hydride (LiAlH4), calcium hydride (CaH2), sodium borohydride (NaBH4) and potassium boro-hydride (KBH4) - have found widespread use in the purification of chemicals. 

Dimethylformamide (DMF), dioxane, piperidine, methylene chloride, acetonitrile, trimethyl orthoformate (TMOF), sodium borohydride, diisopropylcarbodiimide, and trifluoroacetic acid (TFA) were purchased from Aldrich Chemical Company, Inc. and used without further purification. All of the diversity reagents were purchased from Aldrich except for Fmoc-glycine-OH, which was purchased from Novabiochem. 

Diels-Alder reaction of the furoindole 544 with 3,4-pyridyne (1193), generated in situ via two different ways, led to a mixture of the two possible cycloadducts 1194 and 1195 in approximately equal amounts. Without purification, the crude adducts 1194 and 1195 were treated with basic sodium borohydride (NaBH4) to afford a separable mixture of ellipticine (228) and isoellipticine (1196) in 23% and 29% yield, respectively (527) (Scheme 5.197). 

Sodium borohydride was purchased from Avocado, and used without purification. 

Sodium borohydride (99%, powder) is used as received. Ammonium sulfate (anhydrous, 99 + %) is used without further purification 1 however, it is very important that it is ground to a very fine powder. Tetraethylene glycol dimethyl ether (tetraglyme, 2,5,8,ll,14-pentaoxapentadecane)(99%) must be vacuum distilled (110-120°C, < 100 //Torr) from molten sodium before use. 

The preparation of conjugated dienes from pyridines is exemplified by the transformation of 2-picoline into the sex pheromone (669) of Lobesia botrana, a major pest of vineyards (Scheme 154) (80TL67). Thus, the lithio salt of 2-picoline was alkylated by 2-(5-chloropentyl-oxy)tetrahydropyran, the resulting pyridine (665) N-methylated, and the pyridinium salt reduced by sodium borohydride. Quaternization of the 1,2,3,6-tetrahydropyridine (666) and Hofmann elimination gave the (7 , 9Z)-undecadien-l-ol (667) as the sole isomer. Protection of the alcohol and treatment of the corresponding ammonium salt (668) of the amine with lithium dimethylcuprate gave pure (669) after hydrolysis, acetylation and HPLC purification. 

The interest in papain increased enormously after the publication by Kimmel and Smith D ] of a modification of the purification procedure of Balls and Lineweaver [5j. This modification permitted the isolation of pure papain from papaya dried latex and was used for many years as the standard method for the production of papain. The crystalline papain of Kimmel and Smith consists of three components active papain, reversibly oxidized papain, and irreversibly oxidized papain. Reversibly oxidized papain can be converted into active papain by reduction of the active-site thiol by low molecular weight thiols [10], sodium borohydride [11], or CN [12]. In active papain, the Cys-25, which is essential far catalytic activity, is present in a reduced form, while in reversibly oxidized papain the Cvs-25 forms a mixed disulfide with cysteine. Drenth et al. reported that in irreversibly oxidized papain the Cys-25 has been oxidized to the sulfuric acid... 

Purification of arachidonic acid (5,8,11,14-eicosatetraenoic acid) Peroxides are removed from commercially available arachidonic acid by addition of 15 mg of sodium borohydride to 100 mg fatty acid dissolved in 3 ml toluene. The mixture is incubated for 30 min with occasional stirring before addition of 3 ml water and 0.7 ml 1 M citric acid. After vortex-mixing, the phases are separated and the organic phase removed and washed with 1 ml of water. Peroxide free arachidonic acid is dried over anhydrous sodium sulphate and stored at 4°C after addition of 2 ml of 10 mM BHT. 

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