Activity In Coupling Reactions Research Articles

Formation of exceptional monomeric YPhos-PdCl2 complexes with high activities in coupling reactions.

The use of well-defined palladium(ii) complexes as precatalysts for C-X cross-coupling reactions has improved the use of palladium catalysts in organic synthesis including large-scale processes. Whereas sophisticated Pd(ii) precursors have been developed in the past years to facilitate catalyst activation as well as the handling of systems with more advanced monophosphine ligands, we herein report that simple PdCl2 complexes function as efficient precatalysts for ylide-substituted phosphines (YPhos). These complexes are readily synthesized from PdCl2 sources and form unprecedented monomeric PdCl2 complexes without the need for any additional coligand. Instead, these structures are stabilized through a unique bonding motif, in which the YPhos ligands bind to the metal through the adjacent phosphine and ylidic carbon site. DFT calculations showed that these bonds are both dative interactions with the stronger interaction originating from the electron-rich phosphine donor. This bonding mode leads to a remarkable stability even towards air and moisture. Nonetheless, the complexes readily form monoligated LPd(0) complexes and thus the active palladium(0) species in coupling reactions. Accordingly, the YPhos-PdCl2 complexes serve as highly efficient precatalysts for a series of C-C and C-X coupling reactions. Despite their simplicity they can compete with the efficiency of more complex and less stable precatalysts.

Palladium-Catalyzed Amide N-C Hiyama Cross-Coupling: Synthesis of Ketones.

N-Acylglutarimides and arylsiloxanes reacted in the presence of Pd(OAc)2/PCy3, Et3N·3HF, and LiOAc to provide the corresponding arylketones in good yields. Aryl-, vinyl-, and alkyl-substituted N-acylglutarimides showed good activity in the coupling reactions of arylsiloxanes. The reaction had a broad substrate scope and showed good functional group tolerance. N-Benzoylsuccinimide and N-protected N-phenylbenzamides showed good activities in coupling reactions with phenylsiloxane. The employment of CuF2 as an activor afforded the decarbonylative products at 160 °C.

Solvent-free, microwave-assisted highly efficient, rapid and simple synthesis of biphenyl compounds by using silica based Pd(II) catalyst

ABSTRACTTo maintain catalytic performance of any catalyst for a long time, the selection of support material is a very important parameter for heterogeneous catalytic systems, and this performance makes the catalyst valuable. In view of its low cost and availability, silica can be considered as a good support material for transition metal ions in the cross coupling reactions. Therefore, this study describes i) silica-gel based palladium catalyst with a long-term catalytic performance, ii) rapid, simple, economic, and green procedure which was developed for Suzuki reactions. The catalyst showed superior reusability (ten runs) and catalytic efficiency against coupling reactions under mild conditions (50°C, 5 min and air atmosphere). Moreover, the catalyst gave partially good reaction yields with aril chlorides which have poor activity in coupling reactions. In addition, an excellent turnover number (TON: 66000) and frequency (TOF: 825000) were obtained using very small catalyst loading (1.5 × 10−3 mol %). This paper concludes that silica-gel based Pd(II) catalyst and the protocol of synthesis of biaryls were suitable for coupling reactions.

ChemInform Abstract: Fluoride‐Free Hiyama Coupling Reaction Catalyzed by Linear Polystyrene‐Stabilized PdO Nanoparticles in Water: Specific Reactivity of PdO Nanoparticles over Pd Nanoparticles.

AbstractThe catalytic system exhibits high activity in coupling reactions of aryltrimethoxysilanes with a range of bromoarenes affording the corresponding biphenyls.

Efficient catalytic aryl amination of bromoarenes using 3-iminophosphine palladium(II) chloride

While pursuing the development of new hydroamination catalysts, a 3-iminophosphine palladium(II) chloride complex [(3IP)PdCl2] was synthesized that has subsequently proven to be an effective precatalyst for the aryl amination of bromoarenes. This (3IP)PdCl2 complex has been utilized in the catalytic aryl amination of both bromobenzene and bromopyridine derivatives, specifically yielding excellent activity in coupling reactions involving bromobenzene, 4-bromotoluene, and 2-bromopyridine. Using a standard set of catalytic conditions, many alkyl and aryl amines have been investigated as coupling partners in the aryl amination of bromoarenes. In general, secondary alkyl amines and ortho-substituted anilines proved to be the best substrates for this reaction, commonly giving quantitative conversion to products, while primary amines and other anilines gave only poor to moderate results. Catalytic screening data, product yields, and full characterization of isolated products are included.

Magnetite nanoparticles immobilized Salen Pd (II) as a green catalyst for Suzuki reaction

Abstract In this work, we described a methodology to immobilize Salen Pd (II) complex on the surface of magnetite nanoparticles. The palladium catalyst exhibited efficient catalytic activity in coupling reactions with aryl iodides or bromides and phenylboronic acid at 100 °C for 1–3 h under DMF/H2O. Furthermore, the catalyst could be magnetically isolated with a permanent magnet and the yields achieved above 85% after reused at least 5 times.

2-Phenylimidazole−PdCl2 and 2-Phenylimidazoline−PdCl2 Complexes: Single-Crystal and Powder X-ray Diffractometry, 1H NMR Spectra, and Comparison of Catalytic Activities in Coupling Reactions

Single-crystal X-ray diffractometry and powder X-ray diffractometry of the complexes dichlorobis(2-phenyl-1H-imidazole)palladium(II) (1) and dichlorobis(2-phenyl-4,5-dihydro-1H-imidazole)palladium(...

A recombinant cyclodextrin glycosyltransferase cloned from Paenibacillus sp. strain RB01 showed improved catalytic activity in coupling reaction between cyclodextrins and disaccharides

Recombinant cyclodextrin glycosyltransferase (CGTase) was obtained by cloning the PCR gene fragment from thermotolerant Paenibacillus sp. strain RB01 screened from hot spring area in Thailand and cloned into the Escherichia coli expression vector. The nucleotide sequence was analyzed and aligned. Nucleotide sequence of the recombinant CGTase contained an open reading frame of 2139 bp encoding 713 amino acid residues. The recombinant required one-third of culture time and neutral pH to produce CGTase compared to wild type. CGTases from both wild type and transformant were purified in parallel by starch adsorption and DEAE cellulose column. Their biochemical properties such as molecular weight, optimum pH and temperature were quite similar. However, the recombinant enzyme showed improved catalytic activity in the coupling reaction between cyclodextrins (CDs) and some disaccharides. Among several sugars tested with excess βCD, cellobiose was the best substrate followed by leucrose. Very low activity was observed with trehalose, lactose and mellibiose. Sucrose and raffinose showed no activity. The K m and other kinetic parameters of recombinant enzyme were determined for cellobiose and several cyclodextrin derivatives. Recombinant CGTase showed lower K m for βCD and its derivatives, with improved activity compared to wild type enzyme.

1,1′-Bis(oxazolinyl)ferrocene-based palladium catalysts: Synthesis, X-ray structures and applications in Suzuki and Heck coupling reactions

1,1′-Bis(oxazolinyl)ferrocene-based palladium dichloride complexes 2a and 2b were synthesized. X-ray single-crystal diffraction analyses showed that they are of the N, N′-chelating type, and that the coordination mode of 2a, which has an isopropyl group, is of the cis type, whereas that of 2b, which has a tert-butyl group, is the trans one. These two complexes were employed as catalysts for Suzuki and Heck reactions, and showed high catalytic activities in coupling reactions with various aryl halides and counterparts (phenylboronic acid or n-butyl acrylate). Particularly, the catalyst 2a afforded the coupled product of aryl bromide with phenylboronic acid at room temperature.

Organonitrile ligated silver complexes with perfluorinated weakly coordinating anions and their catalytic application for coupling reactions

Homogeneous catalytic processes mediated by silver(I) complexes are relatively rare. This work describes the synthesis and characterization of acetonitrile ligated silver salts with three weakly coordinating anions [B(C6F5)4]−, [B{C6H3(CF3)2}4]− and [(C6F5)3B–C3H4N2–B(C6F5)3]−. The silver cation is coordinated either by four or by two acetonitrile ligands. All examined Ag(I) complexes show catalytic activity in coupling reactions of terminal alkynes with aldehydes and amines.