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%。     

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.     

Photochemistry of N-acetyl and N-benzoyl carbazoles: photo-Fries rearrangement and photoinduced single electron transfer

The photochemistry of two N-acyl carbazoles, N-acetyl and N-benzoyl carbazole, in different pure and mixed organic solvents is studied. Depending on the properties of the medium, photo-Fries rearrangement and photoinduced single electron transfer (PSET) processes are observed yielding the former 1-acyl and 3-acyl carbazoles and the latter 3-chloro-N-acyl carbazole. k_SV, k_Q and φ for fluorescence emission, conversion of N-acyl carbazole and product formation yields have been measured as well as the properties of the N-acyl carbazole radical cations formed during the PSET process (laser flash photolysis experiments). The Rehm-Weller equation is used in order to evaluate the ΔG°_ET of the PSET processes.     

Synthesis of N-perfluoroalkanesulfonyl aromatic imines

N-Sulfinyl perfluoroalkanesulfonamides, R_fSO₂NSO, prepared by refluxing perfluoroalkanesulfonamideswith thionyl chloride, react easily with aromatic aldehydes giving N-perfluoroalkanesulfonyl aromatic imines, R_fSO₂N=CHAr, through elimination of sulfurdioxide.     

Quantitative analysis of transport process of cerium(III) ion through polymer inclusion membrane containing N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as carrier

The facilitated transport mechanism of cerium(III) ions through polymer inclusion membrane (PIM) consisting of cellulose triacetate (CTA) as a polymer matrix, 2-nitrophenyl n-octyl ether (NPOE) as a solvent and N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) as a carrier was studied. In order to evaluate the mass transport phenomena in the PIM, a mathematical model was derived from the Fick's first law and the equations for the extraction and the material balance. Methods to determine the values of the transport parameters such as the diffusion coefficient are described, and the dependency of the flux on the experimental condition was calculated. The model is very useful as a design tool to analyze and optimize the concentration process of low level radioactive wastewater using the PIM.     

Novel examples of the N-methyl effect on cyclisations of N-Boc derivatives of amino alcohols. A theoretical study

New examples of the N-methyl effect on the cyclisation of N-tert-butoxycarbonyl derivatives of amino alcohols are reported. Ab initio studies for the displacement step with formation of the five-membered heterocycle indicate that the increase of the nucleophile character of the carbonyl oxygen of the carbamate group with the N-methyl substitution is responsible for the acceleration of the cyclisation step.     

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.     

Reactions of N, N-dichloroalkylamines with solid base as studied by FTIR combined with DFT calculations

Products of vacuum gas–solid reactions of N, N-dichloroalkylamines with KOH have been identified by FTIR spectroscopy and DFT calculations. It has been found that the reactions consist of elimination of two Cl atoms accompanied with migration of an H atom, a ring carbon or a methyl group from the -carbon to the N atom and unstable imines with a C=N double bond are formed.     

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].     

New preparation of N(1)- and N(2)- alkylated tetrazoles via displacement of activated alcohols

A facile and convenient synthesis of N(1)- and N(2)-alkyltetrazoles is described. Tetrazole in the presence of zinc triflate reacts smoothly with activated alcohols to give the corresponding alkyltetrazole in high yield.     

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.     

Excited state intramolecular charge transfer in N,N-heterocyclic-4-aminobenzonitriles: a DFT study

The excited state intramolecular charge transfer (ICT) reaction in a series of N,N-heterocyclic 4-aminobenzonitriles is investigated theoretically by a combination of density functional theory and multi-reference configuration interaction (DFT/MRCI). Experimentally, increasing ICT emission is observed with increasing ring size. Formation of both a planar and twisted ICT (PICT and TICT) state are energetically unfavorable in the small systems due to high inversion barriers. With increasing ring size, the TICT state is more stabilized than the PICT state. A good agreement of the computed TICT state dipole moment is found with experimental values. The red-shifted fluorescence of all systems is explained by the TICT model due to both arguments.     

Effect of ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) on the growth, stabilization and morphology of silver nanoparticles

The effect of ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetic acid (EGTA) in stabilizing different shapes of silver nanoparticles have been examined by electronic absorption spectroscopy and transmission electron microscopy. The silver nanoparticles were prepared by two methods, i.e. γ-irradiation and chemical reduction method. Two types of effects of EGTA were identified which lead to the formation of truncated triangular silver nanoplates and chain—like silver aggregates respectively. Time-dependent infrared attenuated total reflectance (ATR-FTIR) studies showed that the nature of adsorption of EGTA on the silver nanoparticle surface influences the shape of the nanoparticles. Pulse radiolysis studies showed the mechanism of formation of the initial silver nanoclusters.     

Electrophilic cyclization of N-alkenylamides using a chloramine-T/I2 system

A new protocol for the cyclization of N-alkenylamides using chloramine-T and iodine is described. When N-alkenylsulfonamides are treated with chloramine-T and iodine, three- to six-membered N-heterocycles are obtained with complete stereoselectivity. The method is compatible with the cyclization of the allylbenzamide or allylbenzthioamide to afford an oxazoline or thiazoline derivative, respectively. Mechanistic studies indicate that the chloramine-T/I₂ system functions as an effective iodonium species.     

Indium-mediated diastereoselective addition of allyl bromides to enantiomerically pure N-tert-butylsulfinyl aldimines

The reaction of different N-tert-butylsulfinyl aldimines 1 with allyl bromides 2 and indium powder in THF at 60 °C affords, after hydrolysis with water, the corresponding N-tert-butylsulfinylamines 3 with high chemical yields and diastereoselectivities.     

Synthesis of 2-oxazolines mediated by N,N′-diisopropylcarbodiimide

N-(β-Hydroxy)amides can be cyclised by reaction with diisopropylcarbodiimide (DIC) to give the corresponding 2-oxazolines in high yields. The reaction requires only very mild Lewis-acid catalysis (5 mol % Cu(OTf)₂) and can be accomplished with simple heating, or in very short reaction times under microwave irradiation.     

A new route to the indolopyridonaphthyridine ring system: synthesis of N-benzyl-13b,14-dihydronauclefine and N-benzyl-13b,14-dihydroangustine

The indolo[2:3,3':4']pyrido[1,2-b]naphthyridine ring system, which is present in several alkaloids, has been prepared in a single reaction between the lithio derivative of a 3-cyano-4-methylpyridine and N-benzyl-3,4-dihydro-β-carboline in the presence of trimethylsilyl trifluoromethanesulfonate. Using appropriately substituted starting materials, N-benzyl-13b,14-dihydronaucléfine and N-benzyl-13b,14-dihydroangustine have been made in this way. A new preparation of the synthetic intermediate 9-benzyl-3,4-dihydro-β-carboline is also described.     

Conformational study of N-substituted 8-azabicyclo[3.2.1]octan-3-ones

N-Substituted 8-azabicyclo[3.2.1]octan-3-ones have been studied by ¹H and ¹³C NMR spectroscopy. In CDCl₃ solutions, these ketones display the same preferred conformation. The pyrrolidine and piperidone rings adopt a flattened N-8 envelope and distorted chair conformation, puckered at N-8 and flattened at C-3, respectively, with the N-substituent in axial position with respect to the piperidone ring.     

Vinyl polymerization of norbornene with nickel catalysts bearing [N,N] six-membered chelate ring: Important influence of ligand structure on activity

Norbornene polymerizations with nickel complexes bearing [N,N] six-membered chelate ring activated with methylaluminoxane were investigated. The influence of ligand structure such as β-diimine, β-diketiminate, fluorinated β-diketiminate, and anilido-imine ligand on catalytic activities for norbornene polymerization was evaluated in detail. Ligands led to different electrophilicity of the nickel metal center, and a relatively positive nickel metal center would result in high catalytic activities for norbornene polymerization. The influences of polymerization temperature and Al/Ni ratio on norbornene polymerization with nickel catalysts bearing β-diimine, β-diketiminate, and fluorinated β-diketiminate ligands were also examined. All of the obtained polymers catalyzed by these nickel catalysts bearing [N,N] ligand are vinylic addition polynorbornenes with different molecular weights.