189195-36-6

The synthesis of 5′-methyl-2,2′-bipyridine-6-carboxylic acid is described starting from the pivotal 5′-methyl-6-bromo-2,2′-bipyridine building block. Functionalisation of the latest at the 5′-methyl position gives access to the 5′-bromomethyl, 5′-hydroxymethyl and 5′-aminomethyl derivatives. Upon nucleophilic substitution, the hydroxy and amino derivatives react with the 5′-bromomethyl compound to give quasi-linear and podand type intermediates. Thanks to a carboalkoxylation reaction at the 6-bromo position of the different intermediates, followed by a saponification reaction, mono-, bis- and tris-tridentate ligands are obtained, which are particularly well suited for the complexation of lanthanide(III) cations.

Various heterocycles have been introduced on the 3-picoline nucleus via a regioselective BuLi-Me2N(CH2)2OLi (BuLi-LiDMAE) mediated para-lithiation. Useful methyl-polyheterocycles were efficiently prepared by a one-pot lith

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Enantioconvergent intramolecular coupling of α-(2-bromobenzoylamino)benzylboronic esters was achieved using a copper catalyst having helically chiral macromolecular bipyridyl ligand, PQXbpy. Racemic α-(2-bromobenzoylamino)benzylboronic esters were converted into (R)-configured 3-arylisoindolinones with high enantiopurity using right-handed helical PQXbpy as a chiral ligand in a toluene/CHCl3 mixed solvent. When enantiopure (R)- and (S)-configured boronates were separately reacted under the same reaction conditions, both afforded (R)-configured products through formal stereoinvertive and stereoretentive processes, respectively. From these results, a mechanism involving deracemization of organocopper intermediates in the presence of PQXbpy is assumed. PQXbpy switched its helical sense to left-handed when a toluene/1,1,2-trichloroethane mixed solvent was used, resulting in the formation of the corresponding (S)-products from the racemic starting material.

The synthesis of a rigid ditopic ligand incorporating a 1,10-phenanthroline directly connected through its 3-position to the 5-position of a 2,2′:6′,2″-terpyridine is described. The synthesis is based on a series of palladium(0)-catalyzed cross-coupling reactions (Stille and Suzuki couplings) starting from 1,10-phenanthroline and bromo-substituted pyridines.

A set of ligands bearing 6-bromo-2,2′-bipyridine pendant arms attached in the 5′-position are described. Transformation of the bromo to an ester was performed by a carboethoxylation reaction promoted by low-valent Pd(0), while saponification followed by acidification gave the acids. The introduction of an appended function 3-nitrobenzyl, benzamidomethyl, and tert-butylacetyl opens the way to further functionalize these scaffolds for potential labeling of biological material. The synthetic protocols represent a valuable approach to the rational design of ligands bearing oxophilic and anionic sidearms.

The synthetic scope of asymmetric 5′,6-disubstituted-2,2′-bipyridines in the preparation of flexible multitopic ligands has been investigated. The preparation of the pivotal 6-bromo-5′-bromomethyl-2,2′-bipyridine building block involved a Kr?hnke protocol

Oligo-tridentate ligands based on alternating pyridines and pyrimidines were synthesised by Stille-type carbon-carbon bond-forming reactions. The terpyridine-like sites are designed to coalign upon metal complexation, giving rise to organized and rigidly spaced metal ions. Peripheral functionalization of the basic bis-tridentate framework was explored. The heterocycles in the ligands are in an all-trans conformation about the interannular bonds as indicated by comparison of their 1H NMR spectra. An X-ray crystal structure analysis of the nonchiral tris-tridentate ligand 2a reveals a helical structure in the solid state. The seven heterocycles form a helical structure with resulting overlap of the terminal pyridines. Their centroid-to-centroid distance is 4.523 A with 38.8° between the planes. NMR investigations support a helical conformation in solution as well. Electrochemical and UV absorption measurements indicate that the LUMO resides on the pyrimidine moiety of the ligands.