[2-(N,N-Dimethylaminomethyl)ferrocenyl] as a ligand towards mercury

The diorganomercurial bis[2-(N,N-dimethylaminomethyl)ferrocenyl]mercury(II), (FcN)₂Hg (3), can be obtained by the symmetrisation of the heteroleptic (FcN)HgCl (2) with Na₂S₂O₃ or in the transmetallation reaction of 2 with (FcN)Li. By crystallisation only the crystals of rac-(FcN)₂Hg were obtained. X-ray diffraction analysis revealed linear coordinated mercury atom with two η¹-bonded FcN ligands. Additionally, weak chelate interactions exist between mercury and nitrogen atoms of the ---CH₂NMe₂ side chains. According to the ¹H-NMR findings, these interactions are not preserved in solution. Diorganomercurial 3 appears in solution as a mixture of two diastereomers with rac/meso-(FcN)₂Hg ratio of 1:1. This diastereomeric ratio in solution remains constant within a wide temperature range and in different solvents. The NMR spectroscopic data of the heteroleptic organomercurials [(FcN)HgCl]₂·H₂O (1) and (FcN)HgCl (2) indicate the chelate-free structure of this compounds in solution within the studied temperature interval (−80 to 90 °C).     

Reaction of N-vinylindazolium and N-vinylbenzotriazolium salts with nucleophiles

Reaction of N-vinylindazolium tetrafluoroborates with aqueous potassium carbonate or sodium borohydride affords 2,3-dihydroquinazolines which evolve to 1,2,3,4-tetrahydroquinazolines by intra or intermolecular nucleophilic attack. The X-ray structure of one tetrahydroquinazoline, the tricyclic compound 17a, was determined (C₁₄H₁₆N₂O₅, P2₁/n, a=6.001(4)Å, b=13.601(8)Å, c=17.452(6)Å, β=94.93(3)°, V=1419(1)ų, Z=4, R=0.078 for 1541 observed reflexions). Only open-chain compounds are obtained when these salts react with methanol. 2-Vinylindazolium and 3-vinylbenzotriazolium tetrafluoroborates react with aqueous potassium carbonate and with sodium borohydride yielding the corresponding neutral benzazoles by cleavage of the azole-vinyl bond. They add methanol to the exocyclic double bond and, in the case of indazole derivative, an expansion to a 1,2-dihydroquinazoline is observed in basic medium.A general mechanism is proposed for the reaction of vinylpyrazolium and indazolium salts with nucleophiles.     

Preparation and coordination chemistry of N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine

N-diallylaminodiphenylphosphine and N-allylaminobis(diphenyl)phosphine have been prepared by reaction of the appropriate amine with Ph₂PCl. The coordination chemistry of these phosphines has been studied with a range of metals [Pd, Pt, Rh, Ir, Au, Ru, Mo]. Whilst the majority of the complexes are simple bidentate P,P donors, in the case of N-diallylaminodiphenylphosphinecoordination can involve the CC group or the nitrogen centre.     

Basis set superposition error in N-body clusters

We present a new scheme for calculating the basis set superposition error (BSSE) in N-body clusters. It is based on the assumption that each n-body term can be expressed as a sum of only two-body contributions. The conventional Boys–Bernardi method can be used thus for calculating BSSE-corrected energy terms. The scheme is illustrated by some calculations on the hydrogen fluoride trimers and tetramers. The results are compared to the ones obtained with the site–site function counterpoise (SSFC), the hierarchical (Valiron–Mayer) function counterpoise (VMFC), the pairwise additive function counterpoise (PAFC), and the successive reaction counterpoise (SRCP) schemes.     

N-heterocyclic carbene complexes of palladium and rhodium: cis/trans-isomers

Stable carbene complexes of palladium or rhodium are readily accessible by (i) reaction of imidazolium or triazolium salts with palladium complexes bearing basic ligands or rhodium alkoxide complexes, (ii) adduct formation of the free carbene, e.g. 1,3-dimethylimidazoline-2-ylidene, with metal compounds. In the case of palladium(II) and rhodium(I), the resulting complexes show cis/trans-isomerization and can be compared to analogous phosphine complexes.     

微波辅助铜合成2-(N,N-二甲氨基)苯并噁唑衍生物

建立了一种简单实用、经济高效的以取代2-碘芳胺和N,N-二甲基氨基硫代甲酰氯为原料,以碘化亚铜为催化剂,吡啶为溶剂,100 ℃条件下,串联合成2-(N,N-二甲氨基)苯并噁唑衍生物的微波催化体系,合成了一系列中等至良好产率的2-(N,N-二甲氨基)苯并噁唑衍生物,最高产率达90%。     

Interfacially formed poly(N,N-dimethylaminoethyl methacrylate)/polysulfone composite membranes for CO2/N2 separation

Interfacially formed poly(N,N-dimethylaminoethyl methacrylate)/polysulfone (PDMAEMA/PSF) composite membranes were developed for CO₂/N₂ separation. A layer of PDMAEMA was deposited on a microporous PSF substrate by the solution coating technique, followed by crosslinking with p-xylylene dichloride (XDC) at the interface between the PDMAEMA solid layer and the crosslinking solution. The hydrophilicity and surface free energy of the membranes were analyzed by contact angle measurements with different probe liquids. The permselectivity of the membrane was shown to be affected by the PDMAEMA deposition time, interfacial crosslinking reaction time, and the PDMAEMA and XDC concentrations in the polymer coating solution and the crosslinking solution, respectively. The composite membrane showed a CO₂ permeance of 85 GPU and a CO₂/N₂ ideal separation factor of 50 at 23 °C and 0.41 MPa of CO₂ feed pressure.     

Ionic addition of t-butyl N,N-dibromocarbamate (BBC) to alkenes and cycloalkenes

The addition of t-butyl N,N-dibromocarbamate (BBC) to alkenes and cycloalkenes in the presence of BF₃·Et₂O proceeds smoothly at −20°C in CH₂Cl₂ affording upon reduction with aqueous Na₂SO₃ the corresponding β-bromo-N-Boc-amines. Immediate deprotection of these adducts with gaseous HCl yields β-bromoamine hydrochlorides in moderate yields. The regioselectivity typical for Markovnikov addition was observed for styrene. Stereospecific anti-addition of BBC to cyclohexene and (E)-hex-3-ene, as proven by ¹H NMR evidence, is compatible with an ionic addition pathway and can be rationalized by assuming the intermediate complex formation between BBC and BF₃.     

The Thionium/N-Acyliminium Ion Cyclization Cascade as a Strategy for the Synthesis of Azapolycyclic Ring Systems

A series of amidosulfoxides were prepared by the addition of thiophenol to the appropriate alkenoic acid π-bond, and this was followed by reaction of the in situ generated acyl chloride with 3,4-dimethoxyphenethyl amine. The silicon-induced Pummerer reaction of these amidosulfoxides was carried out using 1-(dimethyl-tert-butylsiloxy)-1-methoxyethylene in dry acetonitrile in the presence of a catalytic amount of ZnI₂ and led to the very clean formation of 2-thiophenyl substituted lactams. Iminium ion-aromatic π-cyclization was accomplished by treatment of the initially formed thiophenyl lactams with BF₃·2AcOH which resulted in the generation of an N-acyliminium ion. Cyclization of the iminium ion onto the tethered aromatic ring led to various azapolycyclic ring systems. A related cyclization sequence also occurred with amidosulfoxides that possess simple olefinic tethers. The method was applied toward the synthesis of a member of the protoberberine alkaloid family.     

Synthesis of N,N-bis(trifluoromethyl)amino difluoromethylene trifluorovinyl ether

The first N-containing trifluorovinyl ether monomer (CF₃)₂NCF₂OCFCF₂ was synthesized. The starting perfluoroalkyl imine CF₃–NCF₂ was converted to the perfluoroalkyl amine (CF₃)₂NH by HF. The amine was converted into the carbamoyl fluoride (CF₃)₂NC(O)F via reaction with carbonyl fluoride COF₂ in the presence of NaF. The carbamoyl fluoride was subjected to catalytic fluorination with molecular F₂ in the presence of CsF to afford the hypofluorite (CF₃)₂NCF₂(OF). The hypofluorite was added to CFClCFCl to provide a saturated halocarbon ether. Dechlorination of the ether with zinc in DMSO resulted in the title monomer. The new vinyl ether monomer readily copolymerizes with TFE.     

Asymmetric synthesis of N-aryl aziridines

The reactions of a variety of N-arylhydroxamates as nitrogen transfer reagents to acryloyl derivatives of (−)-8-phenylmenthol, (−)-quinine and (−)-Oppolzer's sultam acting as Michael acceptors was studied. Poor to modest diastereoselection was observed in the formation of aziridines. The absolute structure of one of the pure diastereomers secured from Oppolzer's auxiliary was established by X-ray crystallography and hence the absolute configuration of the derived methyl-N-phenylaziridine-2-carboxylate could be assigned. Whilst only poor facial selectivity was observed for chiral hydroxamic acid prepared from dehydroabietic acid, moderate to good enantioselection of aziridines could be achieved with the chiral quaternary salts based on cinchona alkaloids, especially with that of cinchonine. A model is presented to explain the origin of enantioselection and a mechanism is proposed for the aziridination reaction.     

N-2-亚甲基-噻酚-二茂铁基芳胺衍生物的合成、晶体结构及电化学性质

以邻、间、对-二茂铁苯胺为原料, 合成了含噻酚的二茂铁苯基席夫碱衍生物并还原得到N-2-亚甲基-噻酚-二茂铁基芳胺衍生物，通过元素分析，IR，UV，¹H NMR和X-射线单晶衍射等分析手段，确证了标题化合物的组成和结构，单晶结构解析表明，化合物2c属于单斜晶系，P2/n空间群。量化计算结果证明，化合物2c在晶体中的结构并不是它的最稳定结构；其HOMO轨道主要由Fe原子及茂环上C的原子轨道组成的；电化学实验证明所得邻、间、对化合物的电化学性质相似，氧化还原峰对应于二茂铁的氧化还原过程，Fc⁺ + e^-←→Fc；说明化合物中的二茂铁基所处的化学环境相同，苯环上取代基位置的不同，对化合物在电极表面的扩散系数影响不大, 但对反应速率常数则有较大的影响。     

Molecular and crystal structures of N,N′-propylene- and N,N′-phenylene-diylbis [3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione]

Two macrocyclic ligands, N,N′-propylene-diylbis[3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione] I and N,N′-phenylene-diylbis[3-(1-aminoethyl)-6-methyl-2H-pyran-2,4(3H)-dione] II, have been prepared by the condensation of dehydroacetic acid (3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one) with 1,2-phenylenediamine and 1,3-propylenediamine. They have been characterized by means of elemental analysis, IR spectroscopy as well as by X-ray crystallography. The molecular structures of the compounds I and II can be described as consisting of two β-enaminone-2-pyrone rings interlaced with either alkyl chain in I or phenyl ring in II. The X-ray studies confirmed the existence of strong N–HO intramolecular hydrogen bonds in both structures. Their lengths are in accordance to lengths of RAHB intramolecular hydrogen bonds in 1,3-diketones, aryl-hydrazones, β-enaminones and related heterodienes (2.5–2.6 Å) [P. Gilli, V. Bertolasi, V. Ferretti and G. Gilli, J. Am. Chem. Soc., 122 (2000) 10405].     

氮杂环卡宾催化二氧化碳羧化反应的研究进展

二氧化碳是一种来源丰富的可再生资源,科研工作者一直致力于开发能够高效转化二氧化碳的催化体系。氮杂环卡宾在有机化学中是一类非常重要的催化剂,利用氮杂环卡宾-过渡金属配合物催化实现二氧化碳的高效化学转化受到了人们的广泛关注。本文主要根据氮杂环卡宾-过渡金属配合物进行分类,总结归纳了近年来氮杂环卡宾-过渡金属配合物催化二氧化碳羧化反应的研究进展。     

Methyltrioxorhenium catalysed epoxidations: A comparative study of different N-donor ligands

This report presents a comparative study on the influence of various N-donor ligands coordinated to methyltrioxorhenium (MTO) on the catalytic activity of olefin epoxidation. A monodentate (4-tert-butylpyridine), a bidentate (4,4′-dimethyl-2,2′-bipyridine) and a Schiff-base ligand were chosen for the coordination to MTO. This report is supposed to act as a benchmark for past and future results in this type of catalysis. Until now, unfortunately, the results are often difficult to compare due to varying sets of reaction conditions. In the present examination, identical reaction conditions were applied to find the optimum in performance. Accordingly, (i) ligand concentration, (ii) reaction temperature, (iii) catalyst concentration, (iv) olefin and (v) the solvent were varied. For labile olefins such as trans-β-methylstyrene, both the monodentate and the bidentate pyridine derivates show very good selectivities and activities with a MTO/ligand ratio of 1:5 at 25 °C. The Schiff-base is only a useful additive for the epoxidation of cyclooctene. Due to phase transfer effects it is difficult to compare two-phase systems (solvent dichloromethane (DCM)) to one-phase systems (solvent tert-butanol). A correlation between rotation speed of the stirrer and the turnover frequency was observed.     

Study on structural properties and solution dynamics of zinc complexes with the (N,N-dimethylaminomethyl)ferrocenyl ligand

The reaction of {C,N-[Fe(η⁵-C₅H₅)(η⁵-C₅H₃(CH₂NMe₂)-2)]}Li, (FcN)Li, with zinc chloride affords the diorganozinc complex (FcN)₂Zn (1). In solution, 1 appears as a mixture of rac and meso diastereomers, whereas in the solid state it crystallizes solely as a rac diastereomer. The ratio of rac/meso diastereomers in solution is solvent-, temperature- and concentration-dependent, consistent with an intermolecular exchange between diastereomers. An intramolecular dynamic phenomenon involving dissociation and recoordination of Zn---N bonds was also observed. The reaction of 1 with zinc chloride yields the monoorganozinc compound (FcN)ZnCl (2) as a slightly soluble yellow microcrystalline powder.     

Chiral ferrocenyl amidophosphine ligand for highly enantioselective addition of diethylzinc to N-diphenylphosphinoylimines

The asymmetric addition of diethylzinc to N-diphenylphosphinoylimines afforded N-diphenylphosphinoylamides with enantioselectivity of up to 90% ee in the presence of a catalytic amount of chiral ligand (S)-N-ferrocenoyl-2-[(diphenylphosphino)methyl]-pyrrolidine 13 (7 mol %) and Cu(OTf)₂ (15 mol %). The remarkable improvement of enantioselectivities, as compared with the same type of chiral ligand 6, could be explained by the unique structure of ferrocenyl amidophosphine ligand combining with the reactive intermediate of this addition reaction.     

Photochemical reactions of electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine via photoinduced electron-transfer

Photoinduced electron transfer reactions of several electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields ³TMB* after rapid intersystem crossing from ¹TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), -acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants have been also obtained by calculating with Stern–Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic k_q values for CN and CrN in endergonic region may be the disturbance of exciplexs formation.     

Electronic structure of N-sulfonylimines

The electronic structure of N-sulfonylimines has been studied in detail using ab initio MO and density functional methods. The S–N rotational barriers in HS(O)₂N=CH₂ at G2MP2 and CBS-Q levels have been found to be 3.25 and 3.43 kcal/mol respectively. Complete optimization at HF/6-31+G^*, MP2(full)/6-31+G^* and B3LYP/6-31+G^* levels have shown that synperiplanar arrangement of S–O with respect to C=N is more stable. NBO analysis has been carried out to quantitatively estimate these delocalisations and charge polarization in RS(O)₂N=CH₂ (R=H, Me, Cl, F). The Lewis basic character in N-sulfonylimines is less compared to N-alkylimines due to anomeric interactions that reduce the lone pair electron density on nitrogen in 1.     

Vesicle phases from N-methyl-N-alkanoylglucamin and various co-surfactants

We have studied the phase behavior of N-methyl-N-alkanoylglucamin (GA) in water and the influence of various additives on the phases of GA. We find that GA forms a large L₁-phase that extends up to 60 wt.% of surfactant. The viscosity in this phase increases with increasing concentration and decreasing temperature. When solutions are cooled down below the Krafft-temperature (21–28 °C) T_k the samples transform into clear gels that are stable for several months. The transformation of the gel to the L₁-phase proceeds in two separate steps. Acid–base titration experiments show that the commercially produced GA is not a pure well defined compound but contains about 10% of an anionic surfactant, most likely dodecanoic acid. Solutions of GA can be continuously mixed with the anionic surfactant sodiumdodecylsulfate (SDS) or sodiumdodecylethoxysulfate (SDES) to clear and low viscous phases. Solutions of GA mixed with increasing amount of cationic surfactant tetradecyltrimethylamoniumbromide (TTABr) transform first into two phase systems and then again into low viscous single phases. The influence of several chemically different co-surfactants like n-alcohols, octanoic acid, oleic acid, 2-ethylhexylmonoglyceride (EHMG) and oleylmonoglyceride on the phase behavior of phases with 5% GA has been studied. With increasing mole fraction of the co-surfactants the well-known sequence of phases is observed, namely a L₁-phase, a two phase region L₁/L- and a L-phase. However, the properties of the L-phase for the different systems are very different. For samples with octanol the L-phase is an optically isotropic, transparent, highly viscoelastic gel. Without shear the gel like phase shows no birefringence. FF-TEM micrographs show that it consists of rather monodisperse, unilamellar vesicles with a diameter of about 500 Å. The L-phases for the other co-surfactants are turbid and have a rather low viscosity. They also contain vesicles but with a rather broad size distribution ranging from 200 to 1000 Å. For the same co-surfactant/surfactant ratio the various systems differ also in their conductivity. For some systems the conductivity is only about 20% lower than in the corresponding L₁-phase while in other systems the difference is more than a factor two. These results are an indication that small uni-lamellar vesicles contain more ionic groups at the outside than on the inside of the bilayer and that some systems are composed of uni-lamellar vesicles while others are composed of multilamellar vesicles (onions).