Potassium borohydride oxidation

The reduction of iminium salts can be achieved by a variety of methods. Some of the methods have been studied primarily on quaternary salts of aromatic bases, but the results can be extrapolated to simple iminium salts in most cases. The reagents available for reduction of iminium salts are sodium amalgam (52), sodium hydrosulfite (5i), potassium borohydride (54,55), sodium borohydride (56,57), lithium aluminum hydride (5 ), formic acid (59-63), H, and platinum oxide (47). The scope and mechanism of reduction of nitrogen heterocycles with complex metal hydrides has been recently reviewed (5,64), and will be presented here only briefly. 

Ostroff, A., Sanderson, R. 1957. Oxidation and thermal decomposition of sodium and potassium borohydrides. J Inorg Nuclear Chem 4 230-231. 

Following the periodate oxidation, the 2,3-dialdehyde celluloses were either reduced with potassium borohydride to form the dialcohol or oxidized with sodium chlorite to give dicarboxyl celluloses. The strength loss of the former products was kept lower than 27% and that of the latter 37%. 

Because of this low oxidation-reduction potential, the number of methods available for reducing ferredoxin is limited. Apart from hydrogen gas, ferredoxin may be reduced with organic reductants, such as pyruvate or hypoxanthine in the presence of the appropriate enzymes. Ferredoxin can be reduced nonenzymically with sodium hydrosulfite (dithionite) (Tagawa and Arnon (99) Fry et al. (45)), potassium borohydride (D Eustachio and Hardy (40)), and formamidine sulfinic acid (Shashoua (90)). It can be reduced also by illuminated chloroplasts (Whatley, Tagawa, and Arnon (114)) and, under these conditions, the reduction of ferredoxin is most complete (Bachofen and Arnon (12)). 

A facile synthetic method for a series of macrocycles containing a phosphine oxide group and two selenium atoms was published < 2001J(P 1)1140>. Macrocycles 263 were obtained by a one-pot reaction from 235, which was generated in situ by the previously described procedure from a mixture of potassium selenide and potassium diselenide and dibromides 232. Without isolation, diselenide 235 was treated with potassium borohydride and sodium hydroxide to form a diselenide anion 262, which was allowed to react with various dibromides to give macrocycles 263 with moderate yields. 

An interesting reduction of aromatic nitro compounds which uses glucose in an alkaline medium (equation 7) has received little attention. The advantages of this reaction include high yields, rapid rate and ease of product isolation from oxidation by-products. Other reagents which bring about the reduction of nitroanenes to azoxy compounds include potassium borohydride, sodium arsenate, phosphine and yellow phosphorus. Electrolytic methods have also been utilized. ... 

Quaternization of the pyrimidine ring of quinazolines enhances its reactivity toward nucleophiles. This reactivity has been used to advantage for preparing 1,2,3,4-tetrahydro derivatives. Methylation of 4-phenylquinazoline occurred at N-1 and N-3 (7 1) and was the first example in which it was shown that alkylating at two different sites in quinazolines was possible. The l-methyl(and 3-methyl)quinazolinium salt that was formed was reduced with sodium borohydride to l-methyl(and 3-methyl)-4-phenyl-l,2,3,4-tetra-hydroquinazoline. Potassium permanganate oxidized the latter compound to l-methyl-4-phenylquinazolin-2(lH)-one. 

Starting from onium compounds, the introduction of oxo groups in low yield is accomplished by reduction using potassium borohydride and subsequent oxidation with potassium permanganate to give products 1 and 247 (see Section 7.2.1.2.1.3.). 

Reactions of Indoles. 2-Arylindoles react with tosyl azide under phase-transfer conditions to give 3-diazo-compounds (148). The phenylazoindole (149 R = N2Ph) is converted into the nitroindole (149 R = NO2) by ipso-nitration. Indoles are oxidized by thallium(III) nitrate to mixtures of oxindoles and isatins. Sensitized photo-oxygenation of the indole (150) yields the hydroperoxide (151), which forms compound (152) on treatment with methanolic potassium borohydride. Vilsmeier-Haack formylation of... 

Reaction of arsenious oxide with potassium borohydride in sodium hydroxide solution... 

Recently, a novel graphene-copper nanoparticle composite was prepared by the in situ chemical reduction of a mixture containing graphene oxides and copper(II) ions using potassium borohydride as a reductant. It was mixed with paraffin oil and packed into one end of the fused capillary to fabricate microdisk electrodes for sensing carbohydrates [14]. The results indicated that copper nanoparticles with an average diameter of 20.8 nm were successfully deposited on the graphenes to form a well-interconnected hybrid network. 

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