Oligopyridine derivatives

Coordination bonds, between transition metal atoms and ligating atoms, 27 72-76 Coordination chemistry, of oligopyridines, see Oligopyridines, coordination chemistry Coordination complexes covalent binding in, 5 13-15 fluorocyclic derivatives, 15 346-368 Coordination compounds... 

Some noteworthy reviews on applications of pyridines and their derivatives deal with oligopyridine liquid crystals as novel building blocks for supramolecular architectures based on metal coordination and hydrogen bonding <2000AGE2454>, enantioselective automultiplication of chiral pyridylalkanols by asymmetric autocatalysis <2000ACR382>, and photoactive mono- and polynuclear Cu(i)-phenanthrolines <2001CSR113>. 

The archetypal macrocyclic oligopyridine is cyclosexipyridine (Fig. 28). The synthesis of this molecule was achieved by Newkome and co-workers (350). The elegant synthesis reported appears to be low-yield, and, as yet, no coordination chemistry has been reported. However, 4,4" -diaryl derivatives... 

Bipyridines have also been synthesized by a number of cycloaddition methods. For example, stannylated bipyridines, (12), which can serve as Stille coupling partners for the synthesis of terpyridines and higher oligopyridines, have been generated in 77% and 83% yield by a thermally induced [4 + 2], regioselective cycloaddition between 1,2,4-triazines (11) and tributyl(ethynyl)tin derivatives (Scheme 6).51 Because of the steric interaction of the bulky tributyl tin group with the pyridine ring, less than 5% of the final product was the 3-substituted isomer. 

Terpyridine is the simplest oligopyridine capable of forming a double-stranded helicate. Copper complexes with terpyridine derivatives have been reported. In [Cu2(L17)2](PF6)2 (45) and [Cu2(Li8)2](PF6)2 (46), the ligands have essentially distributed themselves to present bidentate domains to one metal center and a single pyridine donor to the other, to give a [4 + 2] double helicate. The two copper atoms involve different coordination environments, one with a distorted tetrahedral geometry and the second in a approximately linear two-coordinate environment (Fig. 10). 

Terpyridine is the simplest oligopyridine capable of forming a double-stranded helicate. Copper(I) complexes with terpyridine derivatives have been reported. In [Cu2(Li7)2](PF6)2 (45) and [Cu2(Lig)2](PF6)2... 

Chiral bipyridine ligands have been explored for the asymmetric cyclopropanation of diazoacetate. For example, Lyle and Wilson reported that optically active C2-symmetric 2,2 -bipiridyl 248 served as a good ligand for asymmetric cyclopropanation in the presence of CuOTf and phenyl hydrazine (Scheme 1.116) [173]. Boyd et al. showed that a similar 2,2 -bipyridyl 249 also worked as an effective catalyst (Scheme 1.117) [174]. Mono-oxazoline-substituted 2,2 -bipyridyl derivatives 250-252 have been examined (Scheme 1.118) [175]. Chiral double helical oligopyridine... 

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