N-hydroxyimides as efficient ligands for the copper-catalyzed N-arylation of pyrrole, imidazole, and indole

An experimentally simple, efficient, and inexpensive catalyst system was developed for the N-arylation of pyrroles, indoles, and imidazole with aryl and heteroaryl iodides, bromides, and chlorides by applying CuI as catalyst, N-hydroxysuccinimide (L1), N-hydroxymaleimide (L2), or N-hydroxyphthalimide (L3) as ligand, CH3ONa as base, and DMSO as solvent. A variety of functional groups are tolerated in the reaction, including those that are not compatible with Pd-catalyzed amidation methodology.     

Reaction kinetics of the ethene tetramerization catalyst system CrCl3(THF)3, Ph2PN(iPr)PPh2 and MAO: The unexpected and unusual formation of odd-numbered 1-olefins

This paper describes a kinetic investigation of the ethene tetramerization catalyst system comprising CrCl₃(THF)₃, a bis(diphenylphosphino)isopropylamine Ph₂PN(ⁱPr)PPh₂ as ligand and MAO as catalyst activator. The main focus of the experimental study lied on the influence of the ligand to chromium molar ratio on the catalyst performance and the selectivity towards 1-octene. It was found that a sub-stoichiometric ligand/Cr ratio leads to a Schulz–Flory product distribution, while unusual odd-numbered 1-olefins as by-products were formed.     

POLYKETONE FROM ETHYLENE WITH CARBON MONOXIDE CATALYZED BY NOVEL CATALYST SYSTEMS BASED ON COPPER WITH BIDENTATE PHOSPHORUS CHELATING LIGANDS

Copolymerization of ethylene with carbon monoxide was pertormed with Cu catalyst systems. Novel catalystsystems based on Cu (Cu(CH_3COO)_2/ligand/acid) were firstly reported for the copolymerization of ethylene with carbonmonoxide, in which the ligand was a bidentate phosphorus chelating ligand. The experimental results showed that this kindof Cu catalyst system exhibited high activity. When DPPP (1, 3-bis(diphenylphosphine)propane) and CH_3COOH were usedas ligand and acid, the corresponding catalyst system had the best activity of 108.1 g copolymer/(gCu·h). The novel Cu catalyst system had the advantages of high stability and low cost.     

Highly reactive, general and long-lived catalysts for palladium-catalyzed amination of heteroaryl and aryl chlorides, bromides, and iodides: scope and structure-activity relationships

We describe a systematic study of the scope and relationship between ligand structure and activity for a highly efficient and selective class of catalysts containing sterically hindered chelating alkylphosphines for the amination of heteroaryl and aryl chlorides, bromides, and iodides. In the presence of this catalyst, aryl and heteroaryl chlorides, bromides, and iodides react with many primary amines in high yields with part-per-million quantities of palladium precursor and ligand. Many reactions of primary amines with both heteroaryl and aryl chlorides, bromides, and iodides occur to completion with 0.0005-0.05 mol % catalyst. A comparison of the reactivity of this catalyst for the coupling of primary amines at these loadings is made with catalysts generated from hindered monophosphines and carbenes, and these data illustrate the benefits of chelation. Studies on structural variants of the most active catalyst indicate that a rigid backbone in the bidentate structure, strong electron donation, and severe hindrance all contribute to its high reactivity. Thus, these complexes constitute a fourth-generation catalyst for the amination of aryl halides, whose activity complements catalysts based on monophosphines and carbenes.     

CuI催化的酰胺和溴苯的偶联反应研究

本文报道了一种新的催化体系 (CuI / 氨基酸 / K₃PO₄) 催化胺和芳香溴代化合物之间的交叉偶联反应，对于不同的底物都以较好的产率得到了产物。该反应操作简单，适用性广，并且试剂价格便宜。     

In situ Generated Ruthenium Catalyst Systems Bearing Diverse N‐Heterocyclic Carbene Precursors for Atom‐Economic Amide Synthesis from Alcohols and Amines

The transition‐metal‐catalyzed direct synthesis of amides from alcohols and amines is herein demonstrated as a highly environmentally benign and atom‐economic process. Among various catalyst systems, in situ generated N‐heterocyclic carbene (NHC)‐based ruthenium (Ru) halide catalyst systems have been proven to be active for this transformation. However, these existing catalyst systems usually require an additional ligand to achieve satisfactory results. In this work, through extensive screening of a diverse variety of NHC precursors, we discovered an active in situ catalyst system for efficient amide synthesis without any additional ligand. Notably, this catalyst system was found to be insensitive to the electronic effects of the substrates, and various electron‐deficient substrates, which were not highly reactive with our previous catalyst systems, could be employed to afford the corresponding amides efficiently. Furthermore, mechanistic investigations were performed to provide a rationale for the high activity of the optimized catalyst system. NMR‐scale reactions indicated that the rapid formation of a Ru hydride intermediate (signal at δ=?7.8 ppm in the ¹H NMR spectrum) after the addition of the alcohol substrate should be pivotal in establishing the high catalyst activity. Besides, HRMS analysis provided possible structures of the in situ generated catalyst system.     

Identification of an activated catalyst in the iridium-catalyzed allylic amination and etherification. Increased rates, scope, and selectivity

Studies were conducted to determine possible intermediates in the highly enantioselective, iridium-catalyzed amination and etherification of allylic carbonates, and these studies revealed that cyclometalation of the phosphoramidite ligand is likely to generate the active catalyst. The square-planar [Ir(COD)(L1)Cl] (L1 = P(BINOL)(bisphenethylamine)) did not react with cinnamyl carbonate, but did react with amine to generate an Ir(I) trigonal bipyramidal complex coordinated by COD, a cyclometalated kappa2-phosphoramidite, and a kappa1-phosphoramidite. This complex reacted with phosphines to generate products from replacement of the kappa1-phosphoramidite. These cyclometalated complexes were highly active catalysts for allylic amination and etherification and retained the high selectivity of the original catalyst system. In addition, these complexes combined with [Ir(cod)Cl]2 catalyzed reactions of amines with lower loadings, catalyzed reactions of alkylamines and aromatic amines that did not react with the original catalyst system, and catalyzed reactions of phenoxides under milder conditions.     

Simple, efficient catalyst system for the palladium-catalyzed amination of aryl chlorides, bromides, and triflates

Palladium complexes supported by (o-biphenyl)P(t-Bu)(2) (3) or (o-biphenyl)PCy(2) (4) are efficient catalysts for the catalytic amination of a wide variety of aryl halides and triflates. Use of ligand 3 allows for the room-temperature catalytic amination of many aryl chloride, bromide, and triflate substrates, while ligand 4 is effective for the amination of functionalized substrates or reactions of acyclic secondary amines. The catalysts perform well for a large number of different substrate combinations at 80-110 degrees C, including chloropyridines and functionalized aryl halides and triflates using 0.5-1.0 mol % Pd; some reactions proceed efficiently at low catalyst levels (0.05 mol % Pd). These ligands are effective for almost all substrate combinations that have been previously reported with various other ligands, and they represent the most generally effective catalyst system reported to date. Ligands 3 and 4 are air-stable, crystalline solids that are commercially available. Their effectiveness is believed to be due to a combination of steric and electronic properties that promote oxidative addition, Pd-N bond formation, and reductive elimination.     

Modulation of Multifunctional N,O,P Ligands for Enantioselective Copper‐Catalyzed Conjugate Addition of Diethylzinc and Trapping of the Zinc Enolate

In this work, we have successfully synthesized a new family of chiral Schiff base–phosphine ligands derived from chiral binaphthol (BINOL) and chiral primary amine. The controllable synthesis of a novel hexadentate and tetradentate N,O,P ligand that contains both axial and sp³‐central chirality from axial BINOL and sp³‐central primary amine led to the establishment of an efficient multifunctional N,O,P ligand for copper‐catalyzed conjugate addition of an organozinc reagent. In the asymmetric conjugate reaction of organozinc reagents to enones, the polymer‐like bimetallic multinuclear Cu? Zn complex constructed in situ was found to be substrate‐selective and a highly excellent catalyst for diethylzinc reagents in terms of enantioselectivity (up to >99 % ee). More importantly, the chirality matching between different chiral sources, C₂‐axial binaphthol and sp³‐central chiral phosphine, was crucial to the enantioselective induction in this reaction. The experimental results indicated that our chiral ligand (R,S,S)‐ L1 ‐ and (R,S)‐ L4 ‐based bimetallic complex catalyst system exhibited the highest catalytic performance to date in terms of enantioselectivity and conversion even in the presence of 0.005 mol % of catalyst (S/C=20 000, turnover number (TON)=17 600). We also studied the tandem silylation or acylation of enantiomerically enriched zinc enolates that formed in situ from copper‐ L4 ‐complex‐catalyzed conjugate addition, which resulted in the high‐yield synthesis of chiral silyl enol ethers and enoacetates, respectively. Furthermore, the specialized structure of the present multifunctional N,O,P ligand L1 or L4 , and the corresponding mechanistic study of the copper catalyst system were investigated by ³¹P NMR spectroscopy, circular dichroism (CD), and UV/Vis absorption.     

Ruthenium Complexes with Dendritic Ferrocenyl Phosphanes: Synthesis,Characterization, and Application in the Catalytic Redox Isomerization of Allylic Alcohols

An efficient system for the catalytic redox isomerization of the allylic alcohol 1‐octen‐3‐ol to 3‐octanone is presented. The homogeneous ruthenium(II) catalyst contains a monodentate phosphane ligand with a ferrocene moiety in the backbone and provides 3‐octanone in quantitative yields. The activity is increased by nearly 90 % with respect to the corresponding triphenyl phosphane ruthenium(II) complex. By grafting the catalyst at the surface of a dendrimer, the catalytic activity is further increased. By introducing different spacers between ferrocene and phosphorus, the influence on the electronic properties of the complexes is shown by evaluating the electrochemical behavior of the compounds.     

Synthesis and catalytic activity of a poly(N,N-dialkylcarbodiimide)/palladium nanoparticle composite: a case in the Suzuki coupling reaction using microwave and conventional heating

Poly(N,N-dialkylcarbodiimide) was found to be an effective polymeric ligand system for preparing and stabilizing palladium nanoparticles (1-5 nm). The composite material prepared in situ was found to be a robust catalyst for the Suzuki coupling reaction under microwave or regular heating.     

A novel palladium catalyst for the synthesis of hydrogen peroxide from carbon monoxide, water and oxygen

The synthesis of hydrogen peroxide from carbon monoxide, water and oxygen in a biphasic system using palladium complexes with bidentate nitrogen ligands as catalysts was investigated. After testing a series of phenanthroline derivatives, 2,9-dimethyl-4,7-diphenylphenanthroline (8) was selected as the most efficient ligand. The palladium complex with ligand 8 showed high stability and catalytic activity (turnover number up to 600 moles of hydrogen peroxide per mole of palladium per hour) and, on the basis of a preliminary study, carried out in continuous operation mode, it appears a promising catalyst for the development of an industrial process.     

Biguanidine‐functionalized chitosan to immobilize palladium nanoparticles as a novel,efficient and recyclable heterogeneous nanocatalyst for Suzuki–Miyaura coupling reactions

Biguanidine‐functionalized chitosan was synthesized and combined with palladium nanoparticles to yield a recyclable, environmentally benign, heterogeneous catalytic system for the Suzuki–Miyaura C–C coupling reaction. The catalyst was characterized using various techniques. The catalyst was used in Suzuki cross‐coupling reactions of various aryl halides, including less reactive chlorobenzenes, with phenylboronic acid to give biaryls without any additive or ligand. A reusability test demonstrated that the catalyst was highly efficient even after six runs. Solid‐phase poisoning and leaching tests indicated that the catalyst has a heterogeneous nature. Copyright © 2016 John Wiley & Sons, Ltd.     

Efficient and selective peracetic Acid epoxidation catalyzed by a robust manganese catalyst

A manganese catalyst containing a tetradentate ligand derived from triazacyclononane exhibits high catalytic activity in epoxidation reactions using peracetic acid as oxidant. The system exhibits broad substrate scope and requires small (0.1-0.15 mol %) catalyst loading. The catalyst is remarkably selective toward aliphatic cis-olefins. Mechanistic studies point toward an electrophilic oxidant delivering the oxygen atom in a concerted step.     

A novel dicationic phenoxaphosphino-modified Xantphos-type ligand: a ligand for highly active and selective, biphasic, rhodium catalysed hydroformylation in ionic liquids

A highly active and regioselective catalyst obtained from a novel dicationic ligand (1) and Rh(CO)2(acac) for hydroformylation of 1-hexene and 1-octene in ionic liquids is reported. Optimisation studies of various reaction parameters led to an unprecedentedly active (TOFs > 6200 mol mol(-1) h(-1), T= 100 degrees C), selective (l/b ratios > 40) and stable hydroformylation procedure. No catalyst leaching (Rh-loss < 0.07% of initial rhodium intake, P-loss < 0.4% of the initial phosphorus intake) or losses in performance could be measured during 1-octene hydroformylation recycle experiments in 1-butyl-3-methylimidazolium hexafluorophosphate. At low catalyst loadings activities and regioselectivities competitive with one-phase catalysis in conventional solvents were observed. At high catalyst loadings the system is extremely stable and has a long shelf-life as a result of the formation of stable, if inactive rhodium dimers.     

Impregnated palladium on magnetite as catalyst for multicomponent reductive amination reactions and other related reducing processes

The impregnated palladium on magnetite catalyst is a versatile system for different reduction processes using inexpensive polymehtylhydrosiloxane, including multicomponent reductive amination reactions, and aldehyde, imine, sulfinimide and sulfoxide reductions. This catalyst avoids the use of any type of expensive and quite expensive organic ligand, showing excellent yields, under mild reaction conditions. The catalyst is easily removed from the reaction medium, just by using a magnet. The catalytic system is very selective permitting the discrimination between ketones and aldehydes in the reductive amination process.     

High turnover number and rapid, room-temperature amination of chloroarenes using saturated carbene ligands

[equation--see text] A catalytic system for the mild amination of aryl chlorides is described. This system consists of a Pd(0) precursor and a dihydroimidazoline carbene ligand, which is generated in situ from its protonated tetrafluoroborate salt (2). Using this catalyst, aryl and heteroaryl chlorides react with secondary amines and anilines within hours at room temperature. Turnover numbers as high as 5000 are obtained at elevated temperatures for reaction of morpholine with an unactivated aryl chloride.     

Amide‐Substituted Titanocenes in Hydrogen‐Atom Transfer Catalysis

Two new catalytic systems for hydrogen‐atom transfer (HAT) catalysis involving the N?H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtree's catalyst to yield an efficient bimetallic system for radical generation and HAT catalysis.     

Chiral Ansa metallocenes with Cp ring-fused to thiophenes and pyrroles: syntheses, crystal structures, and isotactic polypropylene catalysts.

Syntheses, crystal structures, and polymerization data for new isospecific metallocenes (heterocenes) having cyclopentenyl ligands b-fused to substituted thiophenes (Tp) and pyrroles (Pyr) are reported. The C2- and C1-symmetric heterocenes are dimethylsilyl bridged, have methyl groups adjacent to the bridgehead carbon atoms, and have aryl substituents protruding in the front. rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2/MAO (MAO = methyl alumoxanes) is the most active metallocene catalyst for polypropylene reported to date. rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2 and rac-Me2Si(2,5-Me2-1-Ph-4-Cp[b]Pyr)2ZrCl2 have the same structure, and the former is 6 times more active, produces half the total enantiofacial errors, and is 3.5 times less regiospecific in propylene polymerizations at the same conditions. rac-Me2Si(2-Me-4-Ph-1-Ind)2ZrCl2/MAO is 3.5 times lower in activity than rac-Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2 catalyst, and while the former is the more stereospecific and the less regiospecific, the sum of these two enantioface errors is the same for both species. Fine-tuning the heterocene sterics by changing selected hydrogen atoms on the ligands to methyl groups influenced their catalyst activities, stereospecificites, regiospecificites, and isotactic polypropylene (IPP) Mw. Thus, both substituting a hydrogen atom adjacent to the phenyl ring with a methyl group on an azapentalenyl ligand system and replacing one and then two hydrogens on the phenyl ring with methyls on thiopentalenyl ligands provided increased polymer Tm and Mw with increasing ligand bulk. Polymer molecular weights are sensitive to and inversely proportional to MAO concentration, and the catalyst activities increase when hydrogen is added for molecular weight control. The polymer Tm values with the thiopentalenyls as TIBAL/[Ph3C][B(C6F5)4] systems were higher than with MAO as catalyst activator. A racemic C1, pseudo-meso complex with a hybrid dimethylsilyl-bridged 2-Me-4-Ph-1-Ind/2,5-Me2-4-Ph-1-Cp[b]Pyr ligand produced the first sample of IPP with all the steric pentad intensities fitting the enantiomorphic site control model. Speculative mechanistic considerations are offered regarding electronic effects of the heteroatoms and steric effects of the ligand structures, the preferred phenyl torsion angles, and anion effects.