An efficient copper-catalyzed coupling reaction of pyridin-2-ones with aryl and heterocyclic halides based on Buchwald's protocol

An efficient copper-catalyzed coupling reaction based on the Buchwald's protocol has been established for pyridin-2-ones with aryl iodides, aryl bromides, and heterocyclic bromides.     

An improved protocol for synthesis of N-arylamides and benzoxazoles by the copper-catalyzed reaction of aryl halides with nitriles

An improved protocol for the synthesis of N-arylamides and benzoxazoles by the copper-catalyzed reaction of aryl halides with nitriles has been developed. Use of acetaldoxime as the hydrolysis reagent instead of H₂O facilitates the operation of the reaction. The significantly decreased amount of nitriles, along with use of weak base K₂CO₃ instead of strong base KOH, makes this transformation atom-efficient and environmentally benign. A variety of N-arylamides and benzoxazole derivatives can be synthesized according to this approach.     

Kinetics and mechanism of hydroboration reactions of HBBr2 · SMe2 and HBCl2 · SMe2 - Application of B NMR spectroscopy

The kinetics and mechanism of the hydroboration reactions of 1-octene with HBBr₂ · SMe₂ and HBCl₂ · SMe₂, in CH₂Cl₂ as a solvent, were studied. Rates of hydroboration were monitored using ¹¹B NMR spectroscopy. The reactions exhibited simple second-order kinetics of the form . The HBCl₂ · SMe₂ was found to be 20 times more reactive than the HBBr₂ · SMe₂. The overall activation parameters (ΔH^≠, ΔS^≠) for the reaction of HBBr₂ · SMe₂ with 1-octene were found to be 82 ± 1 kJ mol⁻¹, −18 ± 4 J K⁻¹ mol⁻¹ and with 1-hexyne were 78 ± 4 kJ mol⁻¹ −34 ± 12 J K⁻¹ mol⁻¹. For the reaction of HBCl₂ · SMe₂ with 1-octene, ΔH^≠ and ΔS^≠ were 104 ± 5 kJ mol⁻¹ and 43 ± 16 J K⁻¹ mol⁻¹, respectively. The activation parameters (ΔH^≠, ΔS^≠) for the dissociation of Me₂S from HBBr₂ · SMe₂ were found to be 104 ± 2 kJ mol⁻¹, +33 ± 8 J K⁻¹ mol⁻¹, respectively. Based on the activation parameters, it was concluded that the detaching of Me₂S from the boron centre follows a dissociative mechanism, while the hydroboration process follows an associative pathway. It was also concluded that the dissociation of Me₂S from the boron centre is the rate determining step.     

New versatile organyltellurium(IV) halides: Synthesis and X-ray structural features of the telluronium tellurolate salts [PhTe(CH3)2]2[TeX6] (X = Cl, Br) and [Ph3Te][PhTeX4] (X = Cl, Br, I)

TeX₄ (X = Cl, Br) react in HCl/HBr with [Ph(CH₃)₂Te]X (X = Cl, Br) to give [PhTe(CH₃)₂]₂[TeCl₆] (1) and [PhTe(CH₃)₂]₂[TeBr₆] (2). The reaction of PhTeX₃ (X = Cl, Br, I) in cooled methanol with [(Ph)₃Te]X (X = Cl, Br, I) leads to [Ph₃Te][PhTeCl₄] (3), [Ph₃Te][PhTeBr₄] (4) and [Ph₃Te][PhTeI₄] (5). In the lattices of the telluronium tellurolate salts 1 and 2, octahedral TeCl₆ and TeBr₆ dianions are linked by telluronium cations through Te?Cl and Te?Br secondary bonds, attaining bidimensional (1) and three-dimensional (2) assemblies. The complexes 3, 4 and 5 show two kinds of Te?halogen secondary interactions: the anion-anion interactions, which form centrosymmetric dimers, and two identical sets of three telluronium-tellurolate interactions, which accomplish the centrosymmetric fundamental moiety of the supramolecular arrays of the three compounds, with the tellurium atoms attaining distorted octahedral geometries. Also phenyl C-H?halogen secondary interactions are structure forming forces in the crystalline structures of compounds 3, 4 and 5.     

Diphenylphosphinite ionic liquid (IL-OPPh2): A solvent and ligand for palladium-catalyzed silylation and dehalogenation reaction of aryl halides with triethylsilane

The use of an imidazolium-based phosphinite ionic liquid (IL-OPPh₂) as both solvent and ligand for Pd offers an efficient catalytic system for silylation of aryl iodides, bromides and also chlorides by triethylsilane in the presence of Cs₂CO₃. In the absence of base, this system is also performed for catalytic dehalogenation of aryl halides. The ionic liquid containing its corresponding Pd(0) complex can be easily recovered and reused in several runs without losing its efficiency.     

New examples of mixed organochalcogene compounds: Synthesis, structural features and spectroscopic data of [PhSe(etu)][PhTeX4] (Ph = phenyl; etu = ethylenethiourea; X = Br, I)

(PhSe)₂ reacts with Br₂, ethylenethiourea and PhTeBr₃, further with I₂, ethylenethiourea and PhTeI₃, to give [PhSe(etu)][PhTeBr₄] (1) (Ph = phenyl; etu = ethylenethiourea) and [PhSe(etu)][PhTeI₄] (2) in very good yields.The tellurium centers present a distorted octahedral configuration, achieved through dimerization involving secondary, reciprocal Te···X interactions.In both compounds the anionic dimmers are linked through X···X interactions, attaining a one-dimensional, polymeric assembly along the b axis. Cations and anions are linked through short Se···X contacts. In addition to single crystal X-ray data, multinuclear NMR results for 1 and 2 are also presented and discussed.     

Two new metal derivates of the alumosiloxane [Ph2SiO]8[AlO(OH)]4: [Ph2SiO]8[AlO2(Na)]4 · 5(THF) and [Ph2SiO]8[AlO(OH)]2[AlO2]2[Zn(OH)]2 · 2(OEt2)

When the polycyclic alumosiloxane [Ph₂SiO]₈[AlO(OH)]₄ is allowed to react with either cyclopentadienyl sodium in tetrahydrofuran or with dimethyl zinc in diethyl ether the organic ligands on the metal elements are eliminated as cyclopentadiene or methane and the metals are bonded to oxygen atoms in the alumosiloxane forming [Ph₂SiO]₈[AlO₂(Na)]₄ · 5(THF) or [Ph₂SiO]₈[AlO(OH)]₂[AlO₂]₂[Zn(OH)]₂ · 2(OEt₂), respectively. X-ray structure determinations reveal that in the sodium derivative the original polycycle rests almost unchanged while in the zinc derivative the inner skeleton is rearranged.     

New effective reagent [Cp2ZrH2 · ClAlEt2]2 for alkene hydrometallation

New bimetallic complex [Cp₂ZrH₂ · ClAlEt₂]₂ (1) was synthesized, and its reactivity in hydrometallation reaction with the following alkenes was studied: hept-1-ene, okt-1-ene, α-methylstyrene, (1S)-β-pinene, (+)-camphene. Complex 1 shows the highest reactivity among the other known Al,Zr-bimetallic complexes: [Cp₂ZrH₂ · ClAlBuⁱ₂]₂ (2), [Cp₂ZrH₂ · AlEt₃]₂ (3), [Cp₂ZrH₂ · AlBuⁱ₃]₂ (4) and [Cp₂ZrH₂ · HAlBuⁱ₂] (5) as well as organoaluminium compounds (OAC): ⁱBu₂AlH, ⁱBu₃Al and ⁱBu₂AlCl in presence of Zr catalysts. Chlorine containing complexes 1 and 2 appear to be more effective in alkene hydrometallation, and relative hydrometallation rates are (1S)-β-pinene ? (+)-camphene < α-methylstyrene < oct-1-ene < hept-1-ene. Hydrometallation of (1S)-β-pinene and its subsequent oxidation with I₂ run with high diastereoselectivity and yield trans-myrtanol. However, the diastereoselectivity of (+)-camphene hydrometallation is less than that for (1S)-β-pinene, and the reaction gives predominately endo-camphanol.     

X-ray and multinuclear NMR study of the mixed aggregate [(Ph2P(O)N(CH2Ph)CH3) · LiOC6H2-2,6-{C(CH3)3}2-4-CH3) · C7H8]2: a model for the directed metalation of phosphinamides

The addition of LiBuⁿ to a toluene solution of Ph₂P(O)N(CH₂Ph)CH₃1 and 2,6-di-tert-butyl-4-methylphenol 5 leads to the formation of the mixed dimer [(Ph₂P(O)N(CH₂Ph)CH₃) · LiOC₆H₂-2,6-{C(CH₃)₃}₂-4-CH₃) · C₇H₈]₂6. The single crystal X-ray structure shows that two lithium aryloxide moieties dimerize giving rise to a Li₂O₂ core in which each lithium atom is additionally coordinated to a phosphinamide 1 ligand. The multinuclear magnetic resonance study (¹H, ⁷Li, ¹³C, ³¹P) indicates that the solid-state structure is preserved in toluene solution. Complex 6 may be considered as a model for the pre-complexation step preceding the metalation of phosphinamides by an organolithium base.     

Reactivity studies of phenylcalcium iodide towards THF yielding phenyl-free cage compounds - Crystal structures of [{(thf)Ca(O-CHCH2)2}4 · CaO · CaI2] and [(CaO)4 · 4 (thf)3CaI2]

THF proved to be the favoured solvent for the direct synthesis of phenylcalcium iodide. However, ether degradation is the major side reaction in this solvent. Zinc-mediated degradation of THF leads to the formation of the cage compound [{(thf)Ca(O-CHCH₂)₂}₄ · CaO · CaI₂] (1) besides the zincate [(thf)₆Ca] [ZnEt₂Ph₂]. The structure of 1 shows an oxygen-centered Ca₆ octahedron with iodine atoms bound to two opposite corners. Heating of phenylcalcium iodide in THF solution for several hours yields [(CaO)₄ · 4 (thf)₃CaI₂] (2) with a central Ca₄O₄ heterocubane unit. NMR monitoring of the reaction shows that the phenyl groups are converted to benzene due to α-deprotonation of THF.     

Stabilisation of heterobimetallic networks by crown ethers and hydrogen-bonding in [Ni(H2O)6][Cu3Cl8(H2O)2] · (15-crown-5)2 · 2H2O: Structure and magnetism

[Ni(H₂O)₆][Cu₃Cl₈(H₂O)₂] · (15-crown-5)₂ · 2H₂O can be conveniently prepared by the interaction of NiCl₂ · 6H₂O, CuCl₂ · 2H₂O and 15-crown-5 in water. The X-ray crystal structure reveals an ionic complex involved in a hydrogen-bonded two dimensional network with the [Ni(H₂O)₆]²⁺ and [Cu₃Cl₈(H₂O)₂]²⁻ ions sandwiched between the 15-crown-5 macrocycles. The magnetic susceptibility data (4–300 K) and magnetisation isotherms (2–5.5 K; 0–5 T) are best interpreted in terms of intra-trimer ferromagnetic coupling within the [Cu₃Cl₈(H₂O)₂]²⁻ moieties, with J ∼ 6 cm⁻¹, and antiferromagnetic coupling between the trimers, the latter mediated by H-bonding pathways. Comparisons are made to other reported quaternary ammonium salts of [Cu₃Cl₈]²⁻ and [Cu₃Cl₁₂]⁶⁻, most of which display structures that involve close stacking of such Cu(II) trimers, rather than being of the present isolated, albeit H-bonded, types.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

[PdCl2{8-(di-tert-butylphosphinooxy)quinoline)}]: a highly efficient catalyst for Suzuki-Miyaura reaction

The complex [PdCl₂(P-N)] containing the basic and sterically demanding 8-(di-tert-butylphosphinooxy)quinoline ligand (P-N) is a highly efficient catalyst for the coupling of phenylboronic acid with aryl bromides or aryl chlorides. The influence of solvent and base has been investigated, the highest rates being observed at 110 °C in toluene with K₂CO₃ as the base. With aryl bromides the reaction rates are almost independent on the electronic properties of the para aryl substituents, on the contrary, reduced reaction rates are observed when bulky substituents are present on the substrate. Nevertheless the coupling of 2-bromo-1,3,5-trimethylbenzene with phenylboronic acid can be carried out to completion in 2 h using a catalyst loading of 0.02 mol %. Under optimized reaction conditions, turnover frequencies as high as 1900 h⁻¹ can be obtained in the coupling of 4-chloroacetophenone with phenylboronic acid; lower reaction rates are obtained with substrates bearing EDG substituents on the aryl group.     

均相催化体系对CO2与环氧化物耦合反应的研究进展

二氧化碳(CO₂)是造成温室效应的主要因素,同时也是集储量丰富、无毒和可再生等优点的C1资源。其与环氧化物的耦合反应具有高的原子经济性,产物环状碳酸酯作为高极性、低挥发性和良好生物降解性溶剂,可广泛应用于萃取剂、医药中间体和聚合物单体等研究方向。本文首先对CO₂与环氧化物耦合反应发生的机理进行了分析,然后鉴于均相催化体系易制备、高活性等优点,重点从设计思路、催化参数、催化效率等方面,系统综述了催化该耦合反应的不同均相催化体系。最后,总结了为实现均相催化体系可长久发展所必须逾越的阻碍和后续研究方向,希望能够为探索新型、高催化性能的催化体系提供一定的参考价值。     

Preparation, crystal structures, EPR and reflectance spectra of two new charge-transfer salts, [CpFeCpCH2N(CH3)3]4[XMo12O40] · nCH3CN (n = 0 for X = P or n = 1 for X = Ge)

Two new charge-transfer salts, [CpFeCpCH₂N(CH₃)₃]₄[PMo₁₂O₄₀] · CH₃CN (1) and [CpFeCpCH₂N(CH₃)₃]₄[GeMo₁₂O₄₀] (2), were synthesized by the traditional solution synthetic method and their structures were determined by single-crystal X-ray analysis. Salt 1 belongs to the triclinic space group P1, and salt 2 belongs to the triclinic space group . There exist the complex interactions of the cationic ferrocenyl donor and Keggin polyanion in the solid state. The solid state UV-Vis diffuse reflectance spectra indicate the presence of a charge-transfer band climbing from 450 nm to well beyond 900 nm for 1, a charge-transfer band from 460 to 850 nm with λ_max = 630 nm for 2.The EPR spectra of salts 1 and 2 at 77 K show a signal at g = 2.0048 and 1.9501, respectively, ascribed to the delocalization of one electron in reduced Keggin ion in salt 1 and the Mo^VI in [GeMo₁₂O₄₀]⁴⁻ is partly reduced to Mo^V owing to the charge-transfer transitions taking place between the ferrocenyl donors and the POM acceptors. The two compounds were also characterized by IR spectroscopy and cyclic voltammetry.     

Kinetics of the CH3 + HCl/DCl → CH4/CH3D + Cl and CD3 + HCl/DCl → CD3H/CD4 + Cl reactions: An experimental H atom tunneling investigation

The kinetics of the radical reactions of CH₃ with HCl or DCl and CD₃ with HCl or DCl have been investigated in a temperature controlled tubular reactor coupled to a photoionization mass spectrometer. The CH₃ (or CD₃) radical, R, was produced homogeneously in the reactor by a pulsed 193 nm exciplex laser photolysis of CH₃COCH₃ (or CD₃COCD₃). The decay of CH₃/CD₃ was monitored as a function of HCl/DCl concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature, typically from 188 to 500 K. The rate constants of the CH₃ and CD₃ reactions with HCl had strong non-Arrhenius behavior at low temperatures. The rate constants were fitted to a modified Arrhenius expression k = QA exp (−E_a/RT) (error limits stated are 1σ + Students t values, units in cm³ molecule⁻¹ s⁻¹): k(CH₃ + HCl) = [1.004 + 85.64 exp (−0.02438 × T/K)] × (3.3 ± 1.3) × 10⁻¹³ exp [−(4.8 ± 0.6) kJ mol⁻¹/RT] and k(CD₃ + HCl) = [1.002 + 73.31 exp (−0.02505 × T/K)] × (2.7 ± 1.2) × 10⁻¹³ exp [−(3.5 ± 0.5) kJ mol⁻¹/RT]. The radical reactions with DCl were studied separately over a wide ranges of temperatures and in these temperature ranges the rate constants determined were fitted to a conventional Arrhenius expression k = A exp (−E_a/RT) (error limits stated are 1σ + Students t values, units in cm³ molecule⁻¹ s⁻¹): k(CH₃ + DCl) = (2.4 ± 1.6) × 10⁻¹³ exp [−(7.8 ± 1.4) kJ mol⁻¹/RT] and k(CD₃ + DCl) = (1.2 ± 0.4) × 10⁻¹³ exp [−(5.2 ± 0.2) kJ mol⁻¹/RT] cm³ molecule⁻¹ s⁻¹.     

Imidazolium-based phosphinite ionic liquid (IL-OPPh2) as Pd ligand and solvent for selective dehalogenation or homocoupling of aryl halides

The use of an imidazolium-based phosphinite ionic liquid (IL-OPPh₂) as ligand for Pd offers an efficient reagent system for the selective dehalogenation or homocoupling of aryl halides in the presence of NaOPrⁱ or Et₃N, respectively. This ionic liquid plays a dual role as both the reaction media and also as the potential complexing agent with Pd via its phosphinite carrying group. The ionic liquid containing its corresponding Pd complex can be easily recovered and reused in several runs.     

Triorganoantimony(V) carboxylates: Synthesis, characterization and crystal structure of [Me3Sb(O2C-C5H4N)2] · H2O

Reactions of [R₃Sb(OPrⁱ)₂] with N-heterocylic carboxylic acids gave compounds of the type [R₃Sb(O₂C-Ar)₂] (1) (R = Me, Et, Prⁱ, Ph; Ar = 2-C₅H₄N, 2-C₉H₆N). The mono-bromo compound [Me₃Sb(Br)(O₂C-C₅H₄N)] (2) exists in equilibrium with [Me₃Sb(O₂C-C₅H₄N)₂] and [Me₃SbBr₂]. All new compounds have been characterized by IR and NMR (¹H and ¹³C{¹H}) spectral data. X-ray structural analysis of one example, [Me₃Sb(O₂C-C₅H₄N)₂], isolated as its monohydrate, revealed an essentially trigonal bipyramidal geometry for the antimony atom defined by three equilaterally disposed methyl groups and two oxygen atoms from monodentate carboxylate groups, in apical positions. The crystal structure is consolidated into a three-dimensional network by cooperative O-H?O, O-H?N and C-H?O interactions.     

Reverse Kocheshkov reaction - Redistribution reactions between RSn(OCH2CH2NMe2)2Cl (R = Alk, Ar) and PhSnCl3: Experimental and DFT study

A series of organotin compounds bearing two intramolecular N → Sn coordination bonds RSn(OCH₂CH₂NMe₂)₂Cl (R = Me (4), n-Bu (5), Mes (6)) were synthesized in good yields. These compounds as well as 2 (R = Ph) react with PhSnCl₃ to give redistribution products RPhSnCl₂ and (Me₂NCH₂CH₂O)₂SnCl₂ (3). The direction of redistribution reactions is reverse to Kocheshkov reaction. DFT calculations have shown that the driving force of the reactions is formation of intramolecular N → Sn coordination bonds in (RO)₂SnCl₂ (3), the Lewis acid stronger than RSn(OR)₂Cl (2, 4-6). The mechanism of the redistribution reaction between 2 and PhSnCl₃ consists of two steps: (1) initial exchange of OCH₂CH₂NMe₂ and Cl to give PhSn(OCH₂CH₂NMe₂)Cl₂ (7) followed by (2). Ph and OCH₂CH₂NMe₂ exchange.