Efficient in situ N-heterocyclic carbene palladium(ii) generated from Pd(OAc)2 catalysts for carbonylative Suzuki coupling reactions of arylboronic acids with 2-bromopyridine under inert conditions leading to unsymmetrical arylpyridine ketones: synthesis, characterization and cytotoxic activities

N,N-Substituted benzimidazole salts were successfully synthesized and characterized by ¹H-NMR, ¹³C {¹H} NMR and IR techniques, which support the proposed structures. Catalysts generated in situ were efficiently used for the carbonylative cross-coupling reaction of 2 bromopyridine with various boronic acids. The reaction was carried out in THF at 110 °C in the presence of K₂CO₃ under inert conditions and yields unsymmetrical arylpyridine ketones. All N,N-substituted benzimidazole salts 2a–i and 4a–i studied in this work were screened for their cytotoxic activities against human cancer cell lines such us MDA-MB-231, MCF-7 and T47D. The N,N-substituted benzimidazoles 2e and 2f exhibited the most cytotoxic effect with promising cytotoxic activity with IC₅₀ values of 4.45 μg mL⁻¹ against MDA-MB-231 and 4.85 μg mL⁻¹ against MCF7 respectively.

The in situ prepared four component system Pd(OAc)₂, 1,3-dialkylbenzimidazolium halides 2a–i and 4a–i, K₂CO₃ under CO atmosphere catalyses carbonylative cross-coupling reaction of 2-bromopyridine with various boronic acids to yield unsymmetrical arylpyridine ketones.

Preparation of 3-benzyloxy-2-pyridinone functional linkers: Tools for the synthesis of 3,2-hydroxypyridinone (HOPO) and HOPO/hydroxamic acid chelators

In contrast to 2,3-dihydroxypyridine, the 3-benzyloxy protected derivative, 2, undergoes facile alkylation at ambient temperatures with a variety of functionalized alkyl halides in good yields. This alkylation has been used to prepare a number of linkers that permit the attachment of 3,2-HOPO moieties onto various scaffolds using a wide range of coupling methods. The Mitsunobu reaction of 2 with representative alcohols was found to be of limited value due to competing O-alkylation that led to product mixtures. The phthalimide 3j can be converted in two steps to HOPO isocyanate 6 in excellent yields. Isocyanate 6 can be coupled to amines at room temperature or to alcohols in refluxing dichloroethane to obtain the corresponding urea or carbamate linked ligand systems. The coupling of isocyanate 6 with TREN followed by deprotection gave the tris-HOPO 10, an interesting target as it has both cationic and anionic binding sites. The HOPO hydroxylamine linker 11 was shown to be especially valuable as its coupling with carboxylic acids proceeds with the concomitant generation of an additional hydroxamate ligand moiety in the framework. The utility of this linker was shown by the preparation of two mixed HOPO-hydroxamate chelators, 16 and 19, based on the structure of desferrioxamine, a well-known trihydroxamate siderophore.

Metal–ligand bifunctional reactivity and catalysis of protic N-heterocyclic carbene and pyrazole complexes featuring β-NH units

The metal–ligand bifunctional cooperation of protic N-heterocyclic carbene and pyrazole complexes bearing an NH unit at the position β to the metal is surveyed.