Copper complex compounds 2,2 -bipyridine

Asymmetric cyclopropanations of alkenes and alkynes with a-diazocarbonyl compounds have been extensively explored in recent years and a number of very effective chiral catalysts have been developed2. Copper complexes modified with such chiral ligands as salicy-laldimines 38202,203, semicorrins 39204 208, bis(oxazolines) 40209-2" and bipyridines 41212 have... 

Because the copper complexes with 2,2/-bipyridine, 1,10-phenanthroline, and their derivatives have a triplet MLCT excited state like that of [Ru(bpy)3]2+, the copper complexes exhibit similar photocatalyses to those of [Ru(bpy)3]2 + for instance, the trans-cis isomerization of stylbene through energy transfer [48] and the photoreduction of viologen compounds [9b,c,e,49,50] were successfully carried out with the copper complexes. Also, a Gratzel-type solar cell was constructed with the copper complexes, recently [51,52]. 

Nitroalkanes to carbonyl compounds. Copper complexes (TMEDA, 2,2-bipyridine, 1,10-phenanthroline) promote the conversion in quantitative yields. 

A radical species may also be generated by reduction of an electron-deficient compound and a classical entry to 4,4 -bipyridines is the reduction of a pyridine by sodium and subsequent rearomatization. Figure 8a illustrates the use of such a reduction in order to prepare the precursor of a sodium-ion molecular switch [30], A more general route, derived from the ancient copper-catalyzed Ullmann coupling, is the metal-induced dimerization of an aryl halide. The key step is a reductive elimination within the coordination sphere of the metal. A nickel(O) complex, in stoichiometric quantities, is usually selected for this purpose. Constable and Ward have used such a reaction to prepare a bis-terpyridine from an interesting synthon, which would have otherwise required a more specialized strategy with dedicated intermediates (Figure 8b) [31]. 

Metal compounds have found some application as desulfurization catalysts, and a novel reaction of N-phenylthiourea has been reported. The reaction of PhNCSNH2 with ethanolic Cu(OAc)2 in the presence of 2,2 -bipyridine results in the formation of the phenylcarbodiimido complex [(bipy)Cu(/i-PhN=C=N)2Cu(bipy)]. The same group have also described a related partial desulfurization of 3-methylimidazoline-2(l if)-thione to yield di( 1-methyl-imidazolyl)sulfide (41) upon reaction with copper(II) salts. These reactions are mechanistically obscure. 

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