Air-Stable and Catalytically Active Phosphinous Acid Transition-Metal Complexes

Suzuki–Miyaura Coupling Reactions of Fluorohalobenzenes

Organofluorine compounds have gained interest in the fields of pharmaceuticals, agrochemicals, diagnostics, materials, and catalysis. Suzuki–Miyaura coupling reactions of fluorinated arenes made a tremendous impact in chemical and biological research and made organofluorinated molecules more readily available. This review gives a brief summary of Suzuki–Miyaura coupling reactions of fluorinated benzene derivatives. In this context, various aspects, such as regio­selectivity, efficiency, and applications, are discussed.

1 Introduction

2 Organofluorine Compounds

3 Suzuki–Miyaura Reactions of Fluorohalobenzenes

3.1 Fluorophthalates

3.2 Reactions of Pentafluorohalobenzenes

3.3 Tetrafluorohalobenzenes

3.4 Trifluorohalobenzenes

3.5 Difluorohalobenzenes

3.6 Monofluorohalobenzenes

3.7 Halo(trifluoromethyl)benzenes

3.8 Trifluoromethyl Pyridines

4 S Summary

Suzuki-Miyaura Cross-Coupling of Bromotryptophan Derivatives at Ambient Temperature

Mild reaction conditions are highly desirable for bio‐orthogonal side chain derivatizations of amino acids, peptides or proteins due to the sensitivity of these substrates. Transition metal catalysed cross‐couplings such as Suzuki–Miyaura reactions are highly versatile, but usually require unfavourable reaction conditions, in particular, when applied with aryl bromides. Ligand‐free solvent‐stabilised Pd‐nanoparticles represent an efficient and sustainable alternative to conventional phosphine‐based catalysts, because the cross‐coupling can be performed at considerably lower temperature. We report on the application of such a highly reactive heterogeneous catalyst for the Suzuki–Miyaura cross‐coupling of brominated tryptophan derivatives. The solvent‐stabilised Pd‐nanoparticles are even more efficient than the literature‐known ADHP‐Pd precatalyst. Interestingly, the latter also leads to the formation of quasi‐homogeneous Pd‐nanoparticles as the catalytic species. One advantage of our approach is the compatibility with aqueous and aerobic conditions at near‐ambient temperatures and short reaction times of only 2 h. The influence of different N^α‐protecting groups, boronic acids as well as the impact of different amino acid side chains in bromotryptophan‐containing peptides has been studied. Notably, a surprising acceleration of the catalysis was observed when palladium‐coordinating side chains were present in proximal positions.

Coordination chemistry and catalysis with secondary phosphine oxides

Review on synthesis, coordination chemistry and catalysis with secondary phosphine oxides.

Secondary phosphine oxides stabilized Au/Pd nanoalloys: metal components-controlled regioselective hydrogenation toward phosphinyl (Z)-[3]dendralenes

A series of gold/palladium nanoalloys stabilized by secondary phosphine oxides have been prepared and applied in selective hydrogenation for the first time.

Enantioselective hydrogenation of ketones by iridium nanoparticles ligated with chiral secondary phosphine oxides

Chiral iridium nanoparticles (IrNPs) were synthesized by H₂reduction of (1,5-cyclooctadiene)(methoxy)iridium(i) dimer ([Ir(OMe)(COD)]₂) in the presence of an asymmetric secondary phosphine oxide.

Coordination Properties of Perfluoroethyl- and Perfluorophenyl-Substituted Phosphonous acids, R(f)P(OH)2

Phosphinic acids, R(f)P(O)(OH)H (R(f)=CF3, C2F5, C6F5), turned out to be excellent preligands for the coordination of phosphonous acids, R(f)P(OH)2. Addition of C2F5P(O)(OH)H to solid PtCl2 under different reaction conditions allows the isolation and full characterization of the mononuclear complexes [ClPt{P(C2F5)(OH)O}{P(C2F5)(OH)2}2] and [Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}] containing hydrogen-bridged [R(f)P(OH)O](-) and R(f)P(OH)2 units. Further deprotonation of [Pt{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] leads to the formation of the dianionic platinate, [Pt{P(C2F5)(OH)O}4](2-), revealing four intramolecular hydrogen bridges. With PdCl2 the dinuclear complex [Pd2(μ-Cl)2{[P(C2F5)(OH)O]2H}2] was isolated and characterized. The Cl(-) free complex [Pd{P(C2F5)(OH)O}2{P(C2F5)(OH)2}2] was also prepared and deprotonated to the dianionic palladate, [Pd{P(C2F5)(OH)O}4](2-). Both compounds were characterized by NMR spectroscopy, IR spectroscopy, and X-ray analyses. In addition, the C6F5 derivatives [ClPt{P(C6F5)(OH)O}{P(C6F5)(OH)2}2] and [Pd2(μ-Cl)2{[P(C6F5)(OH)O]2H}2] as well as the CF3 derivative [Pd2(μ-Cl)2 {[P(CF3)(OH)O]2H}2] were synthesized and fully characterized. Phosphonous acid complexes are inert towards air and moisture and can be stored for several months without decomposition. The catalytic activity of the palladium complexes in the Suzuki cross-coupling reaction between 1-bromo-3-fluorobenzene and phenyl boronic acid was demonstrated.

Developing five-membered heterocycle substituted phosphinous acids as ligands for palladium-catalyzed Suzuki–Miyaura and Catellani reactions

Several secondary phosphine oxides (SPOs) were prepared. Organic products with unexpected conformations (9 and 10) were obtained besides 8 from Heck-type Catellani reactions with the assistance of the selected SPO ligand 5f.

Palladium-catalyzed Suzuki-Miyaura coupling of aryl sulfamates with arylboronic acids

Readily available NHC-Pd(II)-Mp complexes 2 showed efficient catalytic activity toward the Suzuki-Miyaura coupling of aryl sulfamates with arylboronic acids or potassium phenyltrifluoroborate, giving the expected coupling products in good to high yields. It should be noted that this is the first example so far of the phosphine-free, NHC-Pd(II) complexes catalyzed Suzuki-Miyaura coupling of aryl sulfamates with arylboronic acids.