Dipyridyl reagent

Mn2+, D.F.P.-ase is further activated by cysteine, histidine, thiolhistidine, and serine, histamine and 2 2 -dipyridyl. Reagents reacting with metal ions, SH groups and carbonyl groups inhibit D.F.P.-ase activity. Work is proceeding on the further elucidation of such mechanisms.1 In a somewhat similar connexion attention is called to the fact that the non-enzymic hydrolysis of D.F.P. is accelerated by heavy metals and their complexes, in particular by copper chelates of ethylene diamine, o-phenanthroline, 2 2 -dipyridyl and histidine.2... 

Alcoholic solutions of iron (III) chloride are reduced photochemically at an appreciable rate upon exposure to daylight. Reaction of the polyethylene extract with ferric chloride and 2,2 -dipyridyl reagents is carried out, therefore, in black painted... 

Identification A = sprayed with ferric chloride-dipyridyl reagent, B + C = sprayed with antimony pentachloride reagent. Photograph taken about 5 min after spraying. 

If magnesium or zinc salts are to be tested for iron, and the latter is in the tervalent state, reduction is necessary before the a, a -dipyridyl reagent is applied. Metallic zinc or magnesium may not be used, because these metals usually contain traces of iron. Hydroxylamine hydrochloride or sulfurous acid should be used. After adding the a,a -dipyridyl-hydrochloric acid reagent solution, the system should be made basic with ammonium hydroxide. 

Add 1.0 ml of dipyridyl reagent from an automatic pipette and then make the volume in the cylinder to exactly 50 ml with distilled water (Note d). Mix thoroughly. 

Note The reagent can be employed on silica gel layers, which may also be impregnated, for example, with 8-hydroxyquinoline or dibenzoylmethane [3] or with 2,2 -dipyridyl or iminodiacetic acid [4] or on cellulose layers. 

The azido mesylate may also be reduced with lithium aluminum hydride in the same manner as previously described for iodo azide reductions. The sodium borohydride/cobalt(II)tris(a,a -dipyridyl)bromide reagent may be used, but it does not seem to offer any advantages over the more facile lithium aluminum hydride or hydrazine/Raney nickel procedures. 

All such complexes can be thought of as potential. .irreversible labels of bio-molecules. A tris-chelate such as [Os(dipyridyl) 3]2+ will not behave as a reagent which has substitutional properties. Thus one limitation on the tjqpe of complex may well be that at least one or possibly two ligands should be monodentate as in [Pt(ethylenediamine)Cl2]. 

The 4,4 -dipyridyl disulfide can be used in aqueous solutions, but it has been found that modification of proteins with this reagent yields rapid disulfide bond formation. Only when 2-iminothiolane is used in tandem with 4,4 -dipyridyl disulfide can 4-dithiopyridyl groups be introduced into proteins (King et al., 1978) (Section 4.1, this chapter). This is due to disulfide interchange reactions predominating without the addition of 2-iminothiolane. 

Scheme 17 Completion of Kang s synthesis of lb. Reagents and conditions a (i) 103,2,4,6-trichlorobenzoyl chloride, Et3N, THF, rt, (ii) 109, DMAP, benzene, rt, 90% b BU4NF, THF, rt, 94% c TEMPO, NaCl02, NaH2P04 buffer (pH 6.7),NaOCl,MeCN,rt,91% d (i) 2,2 -dipyridyl disulfide, Ph3P, MeCN, (ii) CuBr2, MeCN, rt, 62% e (i) H2,10% Pd/C, MeOH, rt, (ii) aq. CH2O, HOAc, rt, 89%...

Several extensions of these reactions are possible with respect to the electrophilic reagent as well as to the structure of the adduct. Thus functionalized alkyl groups, such as 2-hydroxyethyl and 2-hydroxy-2-phenylethyl, can be introduced into the pyridine ring at the position by treating l-lithio-2-phenyI-l,2-dihydropyridine with ethylene epoxide and styrene epoxide, respectively.144 When polyhalides such as CF3I are used, bis-(substituted-pyridyl)methanes and the dimeric substituted dipyridyls are obtained along with other products.144... 

LACTAMS Di-n-butyltin oxide. Ily-droxylamine-O-sulfonic acid. Iodine azide. Sodium eyanoborohydride. (3-LAC TAMS Cyanuric chloride. Grignard reagents. Ion-exchange resins. Lithium phenylethynolate. Sodium dicarbonyl-cyclopentadienylferrate. Titanium(lll) chloride. Titanium(IV) chloride. Tri-phenylphosphino-Carbon tetrachloride. Triphenylphosphine-Die thyl azodicar-boxylate. Triphenylphosphine-2,2 -Dipyridyl disulfide. 

Dipyridyl Disulfide (Aldrithiol, Corey Reagent) Aldrichimica Acta 1971, 4,33... 

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