Sodium borohydride reduction reactions involving

Sometimes the reaction conditions used in this reaction are too harsh since heating is involved and rearrangement reactions can occur. A milder method that gives better results is to treat the alkene with mercuric acetate [Hg(OAc)2] then sodium borohydride. The reaction involves electrophilic addition of the mercury reagent to form an intermediate mercuronium ion. This reacts with water to give an organomercury intermediate. Reduction with sodium... 

Synthesis. The parent compound, bora2iae [6569-51-3] is best prepared by a two-step process involving formation of B-trichlorobora2iQe followed by reduction with sodium borohydride. These reactions have been studied ia some detail (96). 

Gallenbeck et al. (25) has summarized the work on reductive alkylation using formaldehyde and sodium borohydride to yield dimethylated proteins. Oxidation and reduction reactions involving thiol and disulfide groups have been discussed by Ryan (13) and Feeney (11). 

Although methanol undergoes addition to the C-C double bond of an (alk-l-enyl)cyclopropane in a proton-catalyzed reaction, " generally methanol addition is carried out in a two-step reaction involving methoxymercuration followed by sodium borohydride reduction. The pure product from the first step can be isolated, but this isolation is usually not performed ... 

The first two entries in Table 23.2 illustrate reactions that involve nucleophilic addition to the carbonyl group of the open-chain form which, although present in small amounts, is continuously replenished as it reacts. Entry 1 is the sodium borohydride reduction of the carbonyl group of the aldose o-galactose. The reaction is a general one other... 

Ni(CN)3(NO)] - + iOa + HaO—[Ni(CN)3(NO)]2- + 20H-The importance of the redox nature of molybdenum centres in biological systems has been recognized in several studies. Model systems for nitrogenase, involving molybdate, catalytic amounts of iron(ii), and cysteine, effect the reduction of aliphatic nitriles to alkanes and ammonia in the presence of sodium borohydride. The reaction is accelerated by substrate concentrations of ATP, the active species being considered to be mononuclear molybdenum-thiol complexes. The dinuclear molybdenum complex (7) formed by... 

Pyridoxal Derivatives. Various aldehydes of pyridoxal (Table 3) react with hemoglobin at sites that can be somewhat controlled by the state of oxygenation (36,59). It is thereby possible to achieve derivatives having a wide range of functional properties. The reaction, shown for PLP in Figure 3, involves first the formation of a Schiff s base between the amino groups of hemoglobin and the aldehyde(s) of the pyridoxal compound, followed by reduction of the Schiff s base with sodium borohydride, to yield a covalendy-linked pyridoxyl derivative in the form of a secondary amine. 

The arenediimide anion is very likely to be involved in another type of dediazoniation, namely the reduction of arenediazonium ions by sodium borohydride (Scheme 8-54). The reaction was investigated by Musso s and Rtichardt s groups (Bloch et al., 1969 Rtichardt et al., 1970). 

The reductive replacement of mercury using sodium borohydride is a free radical chain reaction involving a mercuric hydride intermediate.18... 

The last reaction perhaps involves an intermediate such as 33a which expells a proton and dimethyl sulfide. Formation of the Schiff s base with t-butylamine, reduction with sodium borohydride and hydrogenolysis of the benzyl ether produces sulfonterol (28). Despite the fact that the methylene hydrogen of sulfonterol must be much less acidic than of the corresponding urea proton on carbuterol or the sulfonamide proton on soterenol, good bioactivity is retained. 

Two methods were used to measure the chlorine leaving-group KIE for the 5n2 reduction of benzyl chloride to toluene by sodium borohydride in DMSO at 30 °C. One procedure involved the classical IRMS technique. The second method was a new technique in which the ratio of the chlorine isotopes was obtained by fast atom bombardment mass spectrometry on silver chloride recovered from the reaction. The KIE values found by the two methods were 1.007 and 1.008, respectively,... 

Attempts to directly iodinate quinoxaline failed, and the synthesis of 2,3-diphenyl-5,8-dibromoquinoxaline is somewhat more involved (Scheme 9) [61]. Starting from ort/zo-phenylenediamine, reaction with SOCI2 gives benzothia-diazole in high yield. Bromination in HBr furnishes 4,7-dibromobenzothiadi-azole, which can be alkynylated or directly reduced [62]. Reduction of the dibromide with sodium borohydride leaves the halide substituents unmolested but opens the ring to furnish l,4-dibromo-2,3-diaminobenzene. Reaction of this intermediate with a 1,2-dione furnishes a 2,3-disubstituted 5,8-dibromo-quinoxaline. Pd-catalyzed alkynylation finishes the sequence off and removal of the TMS groups yields the desired 5,8-diethynylquinoxaline monomers (Table 9, entries 13,14). 

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