Dipyridyls

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

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

The residue in the flask is said to contain 4-amino- and 2 6-diamino-pyridine, YY dipyridyl and aa -dipyridylamine in varying amounts. 

Supplement (combined with Volumes XXIV and 1936 3458-3793 methane, 25. Pyrimidine, 89. Pyrazine, 91. Nicotine, 110. Dipyridyl, 199. Phenanthroline, 227. Hydroxy compounds, 348 Cinchonine, 424. Quinine, 511. Indigo white, i... 

Eight-membered rings may be formed thermally or photochemically (see PhotochemicalTOCHNOLOGy). Excellent yields can be obtained with ferric acetylacetonate—triethylaluminum—dipyridyl (43). 

Silver(II) Compounds. Sdver(II) is stabilized by coordination with nitrogen heterocychc bases, such as pyridine and dipyridyl. These cationic complexes are prepared by the peroxysulfate oxidation of silver(I) solutions in the presence of an excess of the ligand. An extensive review of the higher oxidation states of silver has beenpubhshed (21). 

Viologen (4,4 -dipyridyl dihydrochloride) [27926-72-3] M 229.1, m >300 . Purified by pptn on adding excess of acetone to a concentrated solution in aqueous MeOH. It has also been recrystd several times from MeOH and dried at 70° under vacuum for 24h [Prasad et al. 5 Am Chem Soc 108 5135 7986], and recrystd three times from MeOH/isopropanol [Stramel and Thomas J Chem Soc, Faraday Trans 82 799 1986]. 

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]. 

Two highly flexible crown ethers have recently been designed and reported for quite different reasons. The first of these is a dipyridyl system reported by Rebek and cowork-... 

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. 

Nicotelline, CjoHgN2 2 3 -Dipyridyl, CioHgN2 worNicotine, C2H12N2 Nicotoine, CgHjjN. ... 

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. 

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. ... 

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