2,2 -bipyridyl N-oxide

Both enantiomers of a series of 2,2 -bipyridyl-N,N -dioxide (274) were prepared in a very elegant fashion described in the following sequence. Bipyridyls 270 reacted with optically pure binaphthyl diacylchloride (R)-271 to give the kinetic diesters 272 that were oxidized followed by a further hydrolysis yielding optically pure (S)-274. 

The Boekelheide reaction has been applied to the synthesis of non-natural products with the preparation of quaterpyridines serving as an example. The sequence began with the 2,4-linked bipyridyl-N-oxide 25. Execution under the typical reaction conditions produced the expected bis-pyridone 26. Treatment with POCI3 afforded the corresponding dichloride that was submitted to a palladium-catalyzed coupling with 2-stannyl pyridine to produce the desired quaterpyridine 27. 

A unique CL reagent, /n.v(2,2 -bipyridyl)rut.hcnium(II) [Ru(bpy)32+] for the postcolumn CL reaction, was applied to HPLC detection. The oxidative-reduction reaction scheme of CL from Ru(bpy)32+ is shown in Figure 17. When the production of light following an oxidation of Ru(bpy)32+ to Ru(bpy)33+ at an electrode surface is measured, this CL reaction is termed electrogenerated chemiluminescence (ECL). The CL intensity is directly proportional to the amount of the reduc-tant, that is, the analyte. 

The electroreduction of some typically inorganic compoimds such as nitrogen oxides is catalysed by the presence of polymeric osmium complexes such as [Os(bipy)2(PVP)2oCl]Cl, where bipy denotes 2,2 -bipyridyl and PVP poly(4-vinylpyridine). This polymer modifies the reduction kinetics of nitrite relative to the reaction at a bare carbon electrode, and provides calibration graphs of slope 0.197 nA with detection limits of 0.1 pg/mL and excellent short-term reproducibility (RSD = 2.15% for n = 20). The sensor performance was found to scarcely change after 3 weeks of use in a flow system into which 240 standards and 30 meat extracts were injected [195]. 

Since complexes of 2,2 -bipyridyl and 1,10-phenanthroline with chromium in oxidation states I and 0 can be obtained by reduction (Scheme 64) of the chromium(n) complexes, these oxidation states will be considered together. Oxidation, as shown in Schemes 65 and 68 of Section 35.4.2.5, gives chromium(III) complexes, which are often best prepared in this way. Earlier work has been extensively reviewed, and few complexes of 2,2 6, 2"-terpyridyl are known.32 A chromium(I) phthalocyanine derivative is mentioned in Section 35.4.9.3. 

Recently, [Ruin(amp)(bipy)H20]Cl-2H20, where H2amp is N-(hydroxy-phenyl) salicyldiimine and bipy is 2,2 -bipyridyl, was reported to show remarkably high catalytic activity, using tm-BuOOH as the oxidant, for the oxidation of benzene to phenol and benzoquinones [36-38] (Fig. 8). 

Oxidation.— Two copper-catalysed reactions have been described for the degradation of the 22-aldehyde (298) to give a pregnan-20-one (299). Oxygenation of a solution of the aldehyde with the copper(n) acetate-2,2 -bipyridyl complex and diazabicyclo-octane in dimethylformamide gave the 20-ketone in 90% yield. A free-radical mechanism is proposed (Scheme 14). 

On the basis of spectroscopic data, chemical properties, and compa-rision with synthetic compounds with similar structural features, the structures of the orellanines were determined by Antkowiak and Gessner 293,294) in the late 1970s. According to their findings, orellanine, the main toxin of C. orellanus, has the structure 3,3, 4,4 -tetrahydroxy-2,2 -bipyridyl-1,1 -dioxide, whereas orellinine and the nontoxic orelline are its monode-A -oxide and dide-N-oxide derivatives, respectively. The structural propositions were well documented, mainly on the basis of UV,... 

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