- Synthesis and smooth muscle calcium channel antagonist effects of alkyl 1,4-dihydro-2,6-dimethyl-4-(pyridinyl)-5-[2-(4,5-dihydro-4,4-dimethylo xazolin-2-yl)]-3-pyridinecarboxylates
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A group of racemic alkyl 1,4-dihydro-2,6-dimethyl-4-(3- or 4-pyridinyl)-5-[2-(4,5-dihydro-4,4-dimethyloxazolin-2-yl)]-3-pyridinec arboxylates 11a-e were prepared by using the Hantzsch reaction involving condensation of the Knoevenagel adducts 9a-e with 1-[2-(4,5-dihydro-4,4-dimethyloxazolin-2-yl)]-1-propen-2-amine (10). In contrast, the 4-(2-pyridinyl) analogue 11f was prepared by thionyl chloride mediated cyclization of the 5-{N-(1,1-dimethyl-2-hydroxyethyl)aminocarbonyl} moiety of 16 to the 5-[2-(4,5-dihydro-4,4-dimethyloxazolin-2-yl)] ring system (11f). In vitro calcium channel antagonist activity was determined by using the guinea pig ileum longitudinal smooth muscle (GPILSM) assay. Compared to the reference drug nifedipine (IC50=1.43 x 10-8 M), the title compounds 11 exhibited weak calcium channel antagonist activity (10-5 to 10-6 M range). A comparison of compounds 11 having a C-4 3-pyridinyl substituent showed that with respect to the alkyl ester R2-substituent, the relative potency order was i-Bu (11c)≤i-Pr (11e)>Me (11a). The point of attachment of the C-4 pyridinyl substituent in the isopropyl ester isomeric series of compounds was a determinant of activity where the potency profile was 4-py (11d)≤3-py (11e)>2-py (11f). Although less effective, the 4,5-dihydro-4,4-dimethyloxazolin-2-yl moiety acts as a bioisostere of the alkyl ester substituent present in classical 1,4-dihydropyridine calcium channel antagonists. The 4,5-dihydro-4,4-dimethyl-oxazolin-2-yl ring system is not an effective bioisostere of the 3-nitro group present in 1,4-dihydropyridine calcium channel agonists since isopropyl 1,4-dihydro-2,6-dimethyl-4-(2-pyridinyl)-5-[2-(4,5-dihydro-4,4-dimethy loxazolin-2-yl)]-3-pyridinecarboxylate (11f) produced a modest 10% increase in the in vitro contractile force of guinea pig left atrium at a concentration of 1.64 x 10-7 M, relative to the reference 3-nitro analogue 1 (EC50=9.6 x 10-6 M).
- Anana, Raymond D.,Knaus, Edward E.
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- Reductive Amination Revisited: Reduction of Aldimines with Trichlorosilane Catalyzed by Dimethylformamide─Functional Group Tolerance, Scope, and Limitations
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Aldimines, generated in situ from aliphatic, aromatic, and heteroaromatic aldehydes and aliphatic, aromatic, and heteroaromatic primary or secondary amines, can be reduced with trichlorosilane in the presence of dimethylformamide (DMF) as an organocatalys
- Campbell, Joanna L. P.,Davies, Christopher D.,Ho?ek, Jan,Ko?ovsky, Pavel,Kysilka, Ond?ej,Popov, Kirill K.,Pour, Milan
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p. 920 - 943
(2022/01/27)
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- SERS/TERS Characterization of New Potential Therapeutics: The Influence of Positional Isomerism, Interface Type, Oxidation State of Copper, and Incubation Time on Adsorption on the Surface of Copper(I) and (II) Oxide Nanoparticles
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The aim of this study was to investigate how the oxidation state of copper (Cu(I) vs Cu(II)), the nature of the interface (solid/aqueous vs solid/air), positional isomerism, and incubation time affect the functionalization of the surface of copper oxide nanostructures by [(butylamino)(pyridine)methyl]phenylphosphinic acid (PyPA). For this purpose, 2-, 3-, and 4-isomers of PyPA and the nanostructures were synthesized. The nanostructure were characterized by UV-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), Raman spectroscopy (RS), and X-ray diffraction (XRD) analysis, which proved the formation of spherical Cu2O nanoparticles (Cu2ONPs; 1500-600 nm) and leaf-like CuO nanostructures (CuONSs; 80-180/400-700 nm, width/length). PyPA isomers were deposited on the surface of NSs, and adsorption was investigated by surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS). The changes of adsorption on the surface of copper oxide NSs caused by the above-mentioned factors were described and the enhancement factor on this substrate was calculated.
- Olszewski, Tomasz K.,Proniewicz, Edyta
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supporting information
p. 4387 - 4400
(2022/03/16)
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- Molybdenum (VI) Complexes Containing Pyridylimine Ligands: Effect of the Imine Nitrogen Substituent in the Epoxidation Reaction
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A series of pyridylimine ligands with variations of the substituent at the imine nitrogen were synthesized and coordinated to the [MoCl2O2] core. The novel molecular structures of the complexes were fully characterized by 1H and 13C NMR, FT-IR, ESI, EA, and X-ray crystallography, and their catalytic activity was studied for the epoxidation of alkenes using tert-butyl hydroperoxide (TBHP) as the oxidant. The new complexes showed excellent catalytic activity and fine selectivity in the epoxidation reaction compared with similar homogeneous molybdenum complexes. The results demonstrated that there is a significant change in the catalytic performance, depending on the alkyl arm on the structure of the pyridilimine ligand. The catalytic results indicated that complex [MoCl2O2(L)] (L: N-(2-Pyridinylmethylene)-1-tert-butylimine) C5 is the best catalytic precursor in the epoxidation of cyclohexene (TON: 92920 and TOF: 30974 h?1).
- Martínez-Martínez, Daniel,Santiago, M. León,Toscano, Rubén A.,Amézquita-Valencia, Manuel
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supporting information
p. 243 - 251
(2020/12/30)
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- Dynamic Covalent Switches and Communicating Networks for Tunable Multicolor Luminescent Systems and Vapor-Responsive Materials
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Molecular switches are an intensive area of research, and in particular, the control of multistate switching is challenging. Herein we introduce a general and versatile strategy of dynamic covalent switches and communicating networks, wherein distinct states of reversible covalent systems can induce addressable fluorescence switching. The regulation of intramolecular ring/chain equilibrium, intermolecular dynamic covalent reactions (DCRs) with amines, and both permitted the activation of optical switches. The variation in electron-withdrawing competition between the fluorophore and 2-formylbenzenesulfonyl unit afforded diverse signaling patterns. The combination of switches in situ further enabled the creation of communicating networks for multistate color switching, including white emission, through the delicate control of DCRs in complex mixtures. Finally, reversible and recyclable multiresponsive luminescent materials were achieved with molecular networks on the solid support, allowing visualization of different types of vapors and quantification of primary amine vapors with high sensitivity and wide detection range. The results reported herein should be appealing for future studies of dynamic assemblies, molecular sensing, intelligent materials, and biological labeling.
- Zou, Hanxun,Hai, Yu,Ye, Hebo,You, Lei
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p. 16344 - 16353
(2019/10/16)
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- Ligand-Tuned C–H Bond Activation/Arylation of 2-Arylpyridines over Pyridine-Based N,O/N,N Ligated Ruthenium–Arene Complexes
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Water-soluble ruthenium(II)–arene complexes [(η6-arene)Ru(κ2-L)]n+ (n = 0, 1) ([Ru]-1–[Ru]-10) containing pyridine-based bischelating N,O/N,N donor ligands (L1–L5) are synthesized and employed for the catalytic C–H bond activation/arylation of a wide range of 2-phenylpyridines and aryl halides in water, affording the corresponding mono- and biarylated products. Exploring the reactivity of the synthesized complexes, our investigations, including time-dependent 1H NMR spectroscopic studies with ruthenium–arene catalysts, demonstrate a remarkable structure–activity relationship for the ligand-tuned C–H activation/arylation of 2-phenylpyridine, where the complexes with bischelating N,O donor-based ligands (acteylpyridine and picolinate) outperform those with N,N donor ligands (iminopyridine). Moreover, among the N,O donor ligands, a distinct effect of the nature of the coordinating oxygen donor on the catalytic activity is also observed, where ruthenium–arene complexes having N,O donor ligands (acetylpyridine) with neutral oxygen-donor atoms exhibit enhanced catalytic activity over those with anionic oxygen-donor atoms (picolinate). The observed trend in the catalytic activity is attributed to the ligand-promoted facile deprotonation and coordination–decoordination interconversion behavior. In addition, molecular structures for a few of the representative complexes ([Ru]-2, [Ru]-4, and [Ru]-5) are authenticated by single-crystal X-ray diffraction studies.
- Binnani, Chinky,Rai, Rohit K.,Tyagi, Deepika,Mobin, Shaikh M.,Singh, Sanjay K.
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supporting information
p. 1435 - 1445
(2018/04/06)
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- Cyclopentadienyl-Ru(II)-Pyridylamine Complexes: Synthesis, X-ray Structure, and Application in Catalytic Transformation of Bio-Derived Furans to Levulinic Acid and Diketones in Water
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A series of cationic half-sandwich cyclopentadienyl-ruthenium(II)-pyridylamine complexes, [(η5-C5H5)Ru(κ2-L)(PPh3)]+ (L = Namine-substituted pyridylamine ligands) ([Ru]-1-[Ru]-6), along with the analogous cyclopentadienyl-ruthenium(II)-N-isopropylpyridylimine complex [(η5-C5H5)Ru(κ2-L)(PPh3)]+ (L = N-isopropylpyridylimine) ([Ru]-7), have been synthesized in good yields. Structural identities of all the complexes have been authenticated by 1H, 13C, and 31P NMR, mass spectrometry, and X-ray crystallography. The synthesized complexes exhibited high catalytic activity for the transformation of the bio-derived furans, 2-furfural (furfural), 5-methyl-2-furfural (5-MF), and 5-hydroxymethyl-2-furfural (5-HMF) to levulinic acid (LA) and the diketones, 3-hydroxyhexane-2,5-dione (3-HHD), 1-hydroxyhexane-2,5-dione (1-HHD), and hexane-2,5-dione (HD) in water. Efficient transformation of furfural to LA over a range of η5-Cp-Ru-pyridylamine complexes is substantially affected by the Namine-substituents, where a η5-Cp-Ru-N-propylpyridylamine complex ([Ru]-2) exhibited higher catalytic activity in comparison to other η5-Cp-Ru-pyridylamine and η5-Cp-Ru-pyridylimine complexes. The relative catalytic activity of the studied complexes demonstrated a substantial structure-activity relationship which is governed by the basicity of Namine, steric hindrance at Namine, and the hemilabile nature of the coordinated pyridylamine ligands.
- Dwivedi, Ambikesh D.,Sahu, Vinod K.,Mobin, Shaikh M.,Singh, Sanjay K.
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supporting information
p. 4777 - 4787
(2018/04/25)
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- Dipicolylamine coupled rhodamine dyes: New clefts for highly selective naked eye sensing of Cu2+ and CN- ions
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The dipicolylamine (DPA) motif which is known as a binder of Zn(ii) ions, has been utilized in devising rhodamine labelled compounds 1 and 2. Compound 1 acts as a FRET sensor and shows excellent selectivity for Cu(ii) ions over a series of other cations in CH3CN/H2O by exhibiting a colour change (colourless to pink) of the solution. The spectral and colour changes are recovered in the presence of CN- ions and thus, the ensemble 1·Cu2+ in CH3CN/H2O is established as the medium for selective detection of CN- ions. In contrast, the modified compound 2 with the dipicolylamine motif as the principal binding site has been established as the colorimetric sensor of Cu(ii) ions and the fluorometric sensor of Hg(ii), Zn(ii) and Cd(ii) ions. Both the compounds 1 and 2 are cell permeable and are successfully employed for the detection of intercellular metal ions through bright field and fluorescence imaging.
- Ghosh, Kumaresh,Tarafdar, Debojyoti,Majumdar, Anupam,Daniliuc, Constantin G.,Samadder, Asmita,Khuda-Bukhsh, Anisur Rahman
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p. 47802 - 47812
(2016/06/06)
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- Cu ion-exchanged and Cu nanoparticles decorated mesoporous ZSM-5 catalysts for the activation and utilization of phenylacetylene in a sustainable chemical synthesis
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Mesoporous ZSM-5 was synthesized using a 1,4-diazabicyclo[2.2.2]octane based multi-cationic surfactant as a structure directing agent. Cu2+ exchanged mesoporous ZSM-5 was prepared by the ion-exchange process. Cu nanoparticles decorated mesoporous ZSM-5 was prepared using NaBH4 as a reducing agent. Materials were characterized by the complementary combination of X-ray diffraction, N2-adsorption, UV-visible, and scanning/transmission electron microscopic techniques. For comparative purposes, Cu2+ exchanged ZSM-5, HY, and NaY; and Cu nanoparticles decorated conventional ZSM-5, SBA-15, and Al2O3 samples were also prepared. A sustainable catalytic process was developed for the selective synthesis of indolizine, chalcone, and triazole derivatives using a mesoporous ZSM-5 based heterogeneous catalyst. A multi-component synthetic strategy is reported here for the selective synthesis of the above mentioned chemicals that involves phenylacetylene as one of the building blocks. Control experiments were performed to ascertain the proposed reaction pathways. Recycling and leaching experiments were performed to demonstrate the sustainability and robustness of the catalytic process. Among these catalysts, Cu nanoparticles decorated mesoporous ZSM-5 exhibited the highest activity in all these reactions. The catalyst was found to be highly stable and it was possible to recycle the catalyst five times with no appreciable loss in the activity. A wide range of indolizine, chalcone, and 1,2,3-triazole derivatives were prepared in high yields using this catalyst.
- Sarmah, Bhaskar,Satpati, Biswarup,Srivastava, Rajendra
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p. 87066 - 87081
(2016/09/23)
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- A highly active and air-stable ruthenium complex for the ambient temperature anti-markovnikov reductive hydration of terminal alkynes
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The conversion of terminal alkynes to functionalized products by the direct addition of heteroatom-based nucleophiles is an important aim in catalysis. We report the design, synthesis, and mechanistic studies of the half-sandwich ruthenium complex 12, which is a highly active catalyst for the anti-Markovnikov reductive hydration of alkynes. The key design element of 12 involves a tridentate nitrogen-based ligand that contains a hemilabile 3-(dimethylamino) propyl substituent. Under neutral conditions, the dimethylamino substituent coordinates to the ruthenium center to generate an air-stable, 18-electron, κ3-complex. Mechanistic studies show that the dimethylamino substituent is partially dissociated from the ruthenium center (by protonation) in the reaction media, thereby generating a vacant coordination site for catalysis. These studies also show that this substituent increases hydrogenation activity by promoting activation of the reductant. At least three catalytic cycles, involving the decarboxylation of formic acid, hydration of the alkyne, and hydrogenation of the intermediate aldehyde, operate concurrently in reactions mediated by 12. A wide array of terminal alkynes are efficiently processed to linear alcohols using as little as 2 mol % of 12 at ambient temperature, and the complex 12 is stable for at least two weeks under air. The studies outlined herein establish 12 as the most active and practical catalyst for anti-Markovnikov reductive hydration discovered to date, define the structural parameters of 12 underlying its activity and stability, and delineate design strategies for synthesis of other multifunctional catalysts.
- Zeng, Mingshuo,Li, Le,Herzon, Seth B.
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supporting information
p. 7058 - 7067
(2014/06/09)
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- General, green, and scalable synthesis of imines from alcohols and amines by a mild and efficient copper-catalyzed aerobic oxidative reaction in open air at room temperature
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A general, green, and scalable synthesis of the useful imines and a,b-unsaturated imines is successfully achieved by a low-loading and powerful, mild and efficient copper-catalyzed aerobic oxidative reaction of alcohols and amines in the open air at room temperature under base- and dehydrating reagent-free conditions. This practical reaction can use air as the economic and green oxidant, tolerates a wide range of substrates, can afford high yields of the target imines on a large scale, and produces water as the only by-product, and thus being the best imination method as yet using alcohols and amines directly.
- Tian, Haiwen,Yu, Xiaochun,Li, Qiang,Wang, Jianxin,Xu, Qing
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supporting information
p. 2671 - 2677,7
(2012/12/12)
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- Direct and mild palladium-catalyzed aerobic oxidative synthesis of imines from alcohols and amines under ambient conditions
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By ligand, TEMPO, and base screening, we developed a mild and green one-pot imine synthesis from alcohols and amines via a low-loading palladium-catalyzed tandem aerobic alcohol oxidation-dehydrative condensation reaction that can be readily carried out in open air at room temperature.
- Jiang, Lan,Jin, Luolu,Tian, Haiwen,Yuan, Xueqin,Yu, Xiaochun,Xu, Qing
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supporting information; experimental part
p. 10833 - 10835
(2011/11/04)
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- Aminophosphinic acids in a pyridine series: Cleavage of pyridine-2- and pyridine-4-methyl(amino)phosphinic acids in acidic solutions
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The synthesis of a series of new pyridine aminomethylphosphinic acids is described. These compounds were obtained in the reaction of the corresponding pyridine aldehydes with primary amines and with ethyl phenylphosphinate, or methylphosphinate, in the presence of bromotrimethylsilane. In aqueous, strong acid solutions, pyridine aminophosphinic acids were split, forming the phenyl-, or methylphosphonic, acid and the corresponding secondary pyridyl-alkylamines. The kinetics of some observed cleavages were measured, and a mechanism of the cleavage has been proposed. Copyright Taylor & Francis Group, LLC.
- Boduszek, Bogdan,Olszewski, Tomasz,Goldeman, Waldemar,Konieczna, Magdalena
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p. 787 - 795
(2007/10/03)
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- Aminophosphine oxides in a pyridine series. Studies on the cleavage of pyridine-2- and pyridine-4-yl-(N-benzylamino)-methyldiphenylphosphine oxides in acidic solutions
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The synthesis and reactions of 1-(N-benzylamino)-1-(2-pyridyl)- and 1-(N-benzylamino)-1-(4-pyridyl)-methyldiphenylphosphine oxides are described. It was found that these compounds were exceptionally easy to cleave in aqueous sulfuric acid solutions to form diphenylphosphinic acid and the corresponding N-(pyridylmethyl)-benzylamines. The structure of a single diastereoisomer, that is, the (R)-(+)-1-[N-(α-methylbenzylamino)]-1-(4-pyridyl)-(S)-methyldiphen ylphosphine oxide was determined by X-ray crystallography. The acidic alcoholysis of the selected model chiral pyridine aminophosphine oxides was investigated by means of 31P NMR spectroscopy. The cleavage kinetics were also studied. On the basis of the obtained results, a mechanism of the cleavage was formulated.
- Goldeman, Waldemar,Olszewski, Tomasz K.,Boduszek, Bogdan,Sawka-Dobrowolska, Wanda
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p. 4506 - 4518
(2007/10/03)
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- Room temperature atom transfer radical polymerization of glycidyl methacrylate mediated by copper(I)/N-alkyl-2-pyridylmethanimine complexes
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The homogeneous controlled/"living" free radical polymerization of glycidyl methacrylate (GMA) by atom transfer radical polymerization (ATRP) using Cu(I)X/N-alkyl-2-pyridylmethanimine complexes with various initiators R-X (X = Cl, Br) and solvents was investigated. Most of these systems display characteristics of a living radical polymerization as indicated by (a) linear first-order kinetic plots of ln[M]0/[M] vs time, (b) an increase in the number-average molecular weight (Mn) vs conversion, and (c) relatively narrow polydispersities indicating a constant number of propagating species throughout the polymerization with negligible contribution of termination or transfer reactions. The dependence of the rate of polymerization on the concentrations of initiator, ligand, and temperature is presented. We observed comparable rates of polymerization linear increase of molecular weight with conversion and low polydispersities in polar solvents. No polymerization was observed in nonpolar solvents such as toluene and xylene at room temperature. The order of controlled polymerization with different initiator system is CuBr/BPN > CuCl/BPN > CuBr/ClPN, and the polymerization did not proceed with CuCl/ClPN initiator system at room temperature. The high functionality of bromine end groups present in the polymer chains was confirmed by ESI MS analysis. The thermal stability of PGMA prepared by the CuBr/PPMI/BPN initiation system is higher than by the other three systems, indicating the high regioselectivity and the virtual absence of termination reactions in the former case. The ligand alkyl chain length from R = propyl to octyl did not affect the rate of polymerization. The molecular weight (Mn) increases linearly with conversion, and these polymers showed narrow polydispersities.
- Krishnan,Srinivasan
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p. 3614 - 3622
(2007/10/03)
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- The acidic cleavage of pyridylmethyl(amino)phosphonates. Formation of the corresponding amines
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Hydrolysis of 3-pyridylmethyl(amino)phosphonates by means of 20% aq. hydrochloric acid gave corresponding 3-pyridimethyl(amino)phosphonic acids, as expected. However, hydrolysis of 2- and 4-pyridylmethyl(amino)phosphonates led to decomposition of the phosphonates with a cleavage of C-P bond and formation of the corresponding amines. The leaving phosphorus moiety was identified as phosphoric acid. The scope of the reaction is limited to 2- and 4-pyridylmethyl derivatives of aminophosphonic acids and their esters, as well as to the derivatives possessing similar structure. On the contrary, the basic hydrolysis of 2- and 4-pyridylmethyl(amino)phosphonates led to the corresponding monoalkyl esters of the aminophosphonates, and no cleavage of C-P bond was observed in those cases.
- Boduszek, Bogdan
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p. 12483 - 12494
(2007/10/03)
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- Kinetics and Mechanism of Ring Closure for a Series of Photoproduced Intermediates (M = Cr, Mo, or W; L = Pyridine 2-Carbaldehyde Imine Ligand)
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Light irradiation of a solution of (M = Cr, Mo, or W) in the presence of a pyridine 2-carbaldehyde imine ligand 2-C5H4NCHNR (L; R = Ph, But, Bun, or Pri) produced a transient complex , in which the normally bidentate ligand is co-ordinated in a monodentate fashion.The photoproduced complex complex subsequently extrudes CO thermally to form a bidentate product ; this process is relatively slow and its time-dependent behaviour has been monitored with a diode-array u.v.-visible spectrophotometer for each of the ligands L.Kinetic data obtained for these chelation reactions indicate that the pyridine nitrogen atom in L preferentially scavenges the photoproduced intermediate.Rate and activation energy parameters closely relate to the nature of the ligand L and imply varying degrees of associative character in the ring-closure transition state.
- Chan, Lisa,Lees, Alistair J.
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p. 513 - 518
(2007/10/02)
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