Efficient, protection-free Suzuki–Miyaura synthesis of ortho-biphenyltetrazoles

Ferrocenylimine Palladium (II) Complexes: Synthesis, Characterization and Application in Mizoroki-Heck and Suzuki-Miyaura Cross-Coupling Reactions

Carbon-carbon cross-coupling reactions are essential synthetic tools for synthesizing polymers, natural products, agrochemicals, and pharmaceuticals. Therefore, new catalysts that function with greater efficiency and functional group tolerance are being researched. We have prepared new ferrocenylimine monodentate N and P donor ligands and N^N and N^P bidentate chelating ligands (L1 to L4) employed in stabilizing palladium ions for application in Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions. The ferrocenylimine ligands were successfully synthesized by Schiff base condensation reactions of acetyl ferrocene with hydrazine monohydrate to afford ferrocenyl hydrazone (L1). Ligand L1 was further treated with aldehydes to give ferrocenyl(2-diphenylphosphino)imine (L3) and ferrocenyl(pyridyl)imine (L3), while phosphination of L1 with chlorodiphenylphosphine afforded L2. The ligands were used to prepare new palladium(II) complexes (C1 to C4) by complexation with [PdCl2(MeCN)2]. All the ligands and complexes were fully characterized using standard spectroscopic and analytical techniques, including 1H NMR and 13C NMR spectroscopy, FT-IR spectroscopy, mass spectrometry and elemental analysis. The complexes (C1 to C4) were tested for efficacies in catalyzing Mizoroki-Heck and Suzuki-Miyaura C-C cross-coupling reactions and proved to be suitable catalyst precursors. Ferrocenyl(2-diphenylphosphine)imino and ferrocenyl-methyl hydrazone palladium(II) complexes C2 and C3 showed the best activities at TONs of up to 201. The ferrocenyl palladium(II) (pre)catalysts demonstrated moderate activity in Mizoroki-Heck reactions involving substrates with substituents on the olefin and aryl halide (including 4-Cl, 4-CH3, -CO2Me and -CO2Et). Density Functional Theory was used to study the mechanism of the Mizoroki-Heck cross-coupling reactions and have led to confirmation of the widely accepted catalytic cycle. Catalyst precursors (C1 to C4) also displayed good activity and selectivity in Suzuki-Miyaura cross-coupling reactions, at 0.5 mol% catalyst loading, with good tolerance to functional groups present on the aryl halide and boronic acid substrates (such as 4-Cl, 4-CHO, 4-COOH, 3-NO2, 3,5-dimethoxy and 4-CH3).

A Molecular Torsion Balance Study: A Nearby Anionic Group Exerts Little Influence on Hydrophobic Interactions between Nonpolar Surfaces

Polar groups have a solvent ordering effect on water and therefore may affect hydrophobic binding energies for nearby lipophilic surfaces. This would mean that determinations of excess surface free energy association energies require consideration of nearby polar functional groups. This paper reports results of a study to measure this possible effect. It was concluded from the models used here that an anionic polar group nearby a hydrophobic surface has little or no effect on the magnitude of hydrophobic association.

Synthesis of a 200-member library of squaric acid N-hydroxylamide amides

We report here the parallel synthesis of 200 compounds based on squaric acid template. These compounds are obtained via a one-step solution-phase procedure starting from three squaric acid N-hydroxylamide esters precursors. The set of diverse reagents qualified (amines, anilines, amino-alcohols and amino-esters) makes this strategy suitable for the search of biologically active compounds. The library was screened on the zinc metalloenzyme ADAMTS-5 and hits with IC(50) in the range of 1-50 microM were identified.