2 : 3 -Dipyridyl

2-Aminopyridine (I) is converted by diazotisation in the presence of bromine and concentrated hydrobromic acid Into 2-bromopyridine (II) the latter upon treatment with copper powder in the presence of p-cymene yields 2 2 -dipyridyl (III). 

Ninhydrin (also named 1 2 3-triketoindane or 1 2 3-triketohydrindene hydrate) is prepared most simply from the inexpensive phthalic anhydride (I). The latter is condensed with acetic anhydride in the presence of potassium acetate to give phthalylacetlc acid (II) reaction of the latter with sodium methoxide in methanol yields 1 3-indanedionecarboxylic acid, which is decomposed upon warming with dilute hydrochloric or sulphuric acid to indane-1 3-dione (or 1 3-diketohydrindene) (HI). Selenium dioxide oxidation of (III) affords indane-1 2 3-trione hydrate (ninhydrin) (IV). 

1 3-Indanedioiie (III) may also be prepared by condensation of diethyl phthalate (V) with rthyl acetate in the presence of sodium ethoxide the resulting sodium 1 3-indanedione-2-carboxylic ester (VI) upon warming with sulphuric acid yields (III). 

Phthalylacetic acid. Heat a mixture of 30 g. of phthalic anhydride, 40 ml. of acetic anhydride and 5 g. of potassium acetate under reflux in an oil bath at 155-165° for 15 minutes. Pour the reaction mixture into ice-cold water, collect the yellow precipitate by suction filtration, wash it three times with 25 ml. of water and once with 10 ml. of 50 per cent, ethanol. Dry the. product at 100° the yield of crude phthalylacetic acid is 20 g. Recrystallise from hot methanol yellow needles, m.p. 245-246°, are obtained. 

Indane-1 3-dione (1 3-diketohydrindene). Method A. To a solution of sodium methoxide, prepared from 6 1 g. of sodium and 200 ml. of anhydrous methanol, add 15 g. of phthalylacetic acid and allow to stand for 1 hour at room temperature collect the yellow precipitate by suction filtration. Mix the yellow solid with 150 ml. of 10 per cent, sulphuric acid, heat on a steam bath until no more carbon dioxide is evolved (15-20 minutes), filter the hot solution and allow to cool. Collect the yellow crystals by filtration at the pump, wash with a little water and dry at 100°. The yield of crude 1 3-indanedione, m.p. 125-126°, is 7 g. Recrystallise from light petroleum, b.p. 80-100°, and thus obtain the pure pioduct, m.p. 129-130°. 

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Ci2Hi2Br2N2. Yellow crystals m.p. 335-340°C, containing water of crystallization soluble in water. Made from 2,2 -dipyridyl and... 

Cathepsin B (from human liver) [9047-22-7] Mr 27,500 [EC 3.4.22.1]. Purified by affinity chromatography on the semicarbazone of Gly-Phe-glycinal-linked to Sepharose 4B, with elution by 2,2 -dipyridyl disulfide [Rich el al. Biochem J 235 731 1986 Methods Enzymol 80 551 1981]. 

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. 

In these papers, the carboxylic acid to be protected was a stable, unsubstituted compound. Harsh conditions were acceptable for both formation and cleavage of the amide. Typically, a simple secondary amide is very difficult to cleave. As the pKa of the conjugate acid of an amide decreases, the rate of hydrolysis of amides derived from these amines increases. The dimethylamide of a cephalosporin was prepared as follows using 2,2 -dipyridyl disulfide. ... 

Reactions of the iminophosphenium cation tosylate with an equimolar amount of quinuclidine or 2,2 -dipyridyl proceed almost instantaneously and quantitatively to a bis-coordinated adduct 19 [56] (Scheme 11). 

Silverman and Dodson made the first detailed isotopic study of this exchange system using the separation afforded by the addition of 2,2 -dipyridyl at pH 5, followed by the precipitation of the ferric iron with either ammonia or 8-hydro-xyquinoline. Dodson , using this separation method, had previously obtained an overall rate coefficient of 16 l.mole" sec at 23 °C for 0.4 M perchloric acid media. The exchange in perchlorate and perchlorate-chloride media was found to conform to a rate law, first order with respect to both total ferrous and ferric ion concentrations, with an observed rate constant (k bs) dependent on the hydrogen-ion concentration, viz. 

The effect of the addition of inorganic ions has been investigated using the isotopic method ( Fe or Fe) and the 2,2 -dipyridyl separation. The rate law in the presence of inorganic anions is given by... 

Additional acceleration of acylation can be obtained by inclusion of cupric salts, which coordinate at the pyridine nitrogen. This modification is useful for the preparation of highly hindered esters.122 Pyridine-2-thiol esters can be prepared by reaction of the carboxylic acid with 2,2 -dipyridyl disulfide and triphenylphosphine123 or directly from the acid and 2-pyridyl thiochloroformate.124... 

Cul, 12mol% of 2,2 -dipyridyl, in lOvol of xylene diglyme (9 1) at 140°C with azeotropic removal of the water as it was formed. The azeotropic removal of water helped alleviate the problem of solids coating the reaction vessel walls, which led to stalling of the reaction. The reaction was complete in less than lOh, typically with 96% assay yield and 92% isolated yield for 49 after aqueous work-up and subsequent crystallization [14b-d]. It was noteworthy that this catalytic system composed of the copper(I) salt with bipyridyl ligand was recently reported to be applicable to a wide range of Ullmann-type ether formations [14d]. 

A palladium catalyst with a less electron-rich ligand, 2,2-dipyridyl-methylamine-based palladium complexes (4.2), is effective for coupling of aryl iodides or bromides with terminal alkynes in the presence of pyrrolidine and tetrabutylammonium acetate (TBAB) at 100°C in water.37 However, the reactions were shown to be faster in NMP solvent than in water under the reaction conditions. Palladium-phosphinous acid (POPd) was also reported as an effective catalyst for the Sonogashira cross-coupling reaction of aryl alkynes with aryl iodides, bromides, or chlorides in water (Eq. 4.18).38... 

A A -coordi nation was found in the zinc complex of 2,2 -dipyridyl diselenide, [ZnLCl2].214 The tridentate ligand 6-(2-aminophenyl)-2,2 -bipyridine contains two pyridyl and one aniline donor ligand to form a complex of the form [ZnL2]2+. The X-ray structure shows a distorted octahedral metal center with each ligand twisting from planar to accommodate the meridional binding.215... 

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