Ruthenium Complexes with Strongly Electron-Donating Terpyridine Ligands: Effect of the Working Electrode on Electrochemical and Spectroelectrochemical Properties.

The combination of 2,2':6',2''-terpyridines (tpy) and Ru is known to deliver molecular and supramolecular assemblies with remarkable properties. Here new Ru complexes, with modified tpy ligands substituted with varying numbers of dimethlyamino groups, are presented. Electrochemistry shows that the incorporation of the strongly electron-donating groups on the tpy ligands leads to a negative shift of the Ru oxidation potential by close to 1 V.

Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes.

Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions.

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides - scope and limitations.

The scope of a flexible route to unsymmetrically functionalized bipyridines is described. Starting from 1,3-diketones 1a-e, the corresponding β-ketoenamines 2a-e were converted into different β-ketoenamides 3a-g by N-acylation with 2-pyridinecarboxylic acid derivatives. These β-ketoenamides were treated with a mixture of TMSOTf and Hünig's base to promote the cyclocondensation to 4-hydroxypyridine derivatives.

A Flexible Terpyridine Derivative Interacts Specifically with G-Quadruplexes.

G-quadruplexes formed by nucleic acids are implicated in pathologies ranging from cancers to neurodegenerative diseases. We evaluated interactions of 29 bi- and terpyridine derivatives with G-quadruplexes and duplexes. FRET-melting, circular dichroism, and (1) H NMR spectroscopy showed that one terpyridine derivative interacted very selectively with G-quadruplexes.

Unprecedented strong Lewis bases--synthesis and methyl cation affinities of dimethylamino-substituted terpyridines.

A versatile method for the synthesis of functionalized 2,2':6',2''-terpyridines by assembly of the terminal pyridine rings is presented. The cyclization precursors-bis-β-ketoenamides-are prepared from 4-substituted 2,6-pyridinedicarboxylic acids and acetylacetone or its corresponding enamino ketone. Treatment with trimethylsilyl trifluoromethanesulfonate induces a twofold intramolecular condensation providing an efficient access to 4,4''-di- and 4,4',4''-trifunctionalized 6,6''-dimethyl-2,2':6',2''-terpyridines.

The Flögel-three-component reaction with dicarboxylic acids - an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives.

An extension of the substrate scope of the Flögel-three-component reaction of lithiated alkoxyallenes, nitriles and carboxylic acids is presented. The use of dicarboxylic acids allowed the preparation of symmetrical bis(β-ketoenamides) from simple starting materials in moderate yields. Cyclocondensations of these enamides to 4-hydroxypyridine derivatives or to functionalized pyrimidines efficiently provided symmetrically and unsymmetrically substituted fairly complex (hetero)aromatic compounds containing up to six conjugated aryl and hetaryl groups.

Per(2-thienyl)pyridines: synthesis and properties.

Starting from an easily available pyridinol derivative, a route to penta(2-thienyl)pyridine and related symmetrical compounds is reported. Key reactions are activation of the pyridine core and metal-catalyzed couplings proving the efficacy of these methods even in sterically highly encumbered systems. UV/vis and fluorescence spectra as well as first cyclovoltametric measurements of the synthesized novel thiophene-pyridine conjugates are reported.

In search of oligo(2-thienyl)-substituted pyridine derivatives: a modular approach to di-, tri- and tetra(2-thienyl)pyridines.

Herein, we describe our attempts to systematically prepare a series of oligo(2-thienyl)-substituted pyridine derivatives. The crucial starting material, a β-alkoxy-β-ketoenamide, is easily available on a large scale by the reaction of lithiated methoxyallene with thiophene-2-carbonitrile and thiophene-2-carboxylic acid. This three-component reaction is followed by intramolecular cyclization to yield the suitably functionalized 2,6-di(2-thienyl)-substituted pyridine derivates.

Three-component synthesis of perfluoroalkyl- or perfluoroaryl-substituted 4-hydroxypyridine derivatives and their palladium-catalyzed coupling reactions.

A three-component reaction with lithiated alkoxyallenes, nitriles, and perfluorinated carboxylic acids as precursors led to a series of perfluoroalkyl- or perfluoroaryl-substituted 4-hydroxypyridine derivatives. These compounds were converted into 4-pyridyl nonaflates which can be employed as versatile building blocks for the synthesis of pi-conjugated compounds with use of palladium-catalyzed couplings. Suzuki reactions at C-4 and C-3 of the pyridine ring proceeded with moderate to high yields.