1232006-42-6Relevant articles and documents
Photosolvolysis reactions of 3-alkoxypyridinium tetrafluoroborate salts
Penkett, Clive S.,Simpson, Iain D.
, p. 6183 - 6204 (1999)
Irradiation of a series of 3-alkoxypyridinium tetrafluoroborate salts in alcohol solution resulted in the formation of cyclopentenone ketals by diastereoselective incorporation of the alcohol solvent under the basic conditions of the photolysis reaction. In a second series of photochemical reactions, the same 3-alkoxypyridinium salts were irradiated in water to yield β-hydroxycyclopentanones stereoselectively.
On the absolute photoionization cross section and dissociative photoionization of cyclopropenylidene
Holzmeier, Fabian,Fischer, Ingo,Kiendl, Benjamin,Krueger, Anke,Bodi, Andras,Hemberger, Patrick
, p. 9240 - 9247 (2016)
We report the determination of the absolute photoionization cross section of cyclopropenylidene, c-C3H2, and the heat of formation of the C3H radical and ion derived by the dissociative ionization of the carbene. Vacuum ultraviolet (VUV) synchrotron radiation as provided by the Swiss Light Source and imaging photoelectron photoion coincidence (iPEPICO) were employed. Cyclopropenylidene was generated by pyrolysis of a quadricyclane precursor in a 1 : 1 ratio with benzene, which enabled us to derive the carbene's near threshold absolute photoionization cross section from the photoionization yield of the two pyrolysis products and the known cross section of benzene. The cross section at 9.5 eV, for example, was determined to be 4.5 ± 1.4 Mb. Upon dissociative ionization the carbene decomposes by hydrogen atom loss to the linear isomer of C3H+. The appearance energy for this process was determined to be AE0K(c-C3H2; l-C3H+) = 13.67 ± 0.10 eV. The heat of formation of neutral and cationic C3H was derived from this value via a thermochemical cycle as ΔfH0K(C3H) = 725 ± 25 kJ mol-1 and ΔfH0K(C3H+) = 1604 ± 19 kJ mol-1, using a previously reported ionization energy of C3H.
Etherification of heterocyclic compounds by nucleophilic aromatic substitutions under green chemistry conditions
Lloung, Matthieu,Loupy, André,Marque, Sylvain,Petit, Alain
, p. 297 - 308 (2004)
Solid-liquid phase transfer catalysis coupled with microwave irradiation was shown to be an efficient method for SNAr reaction of halogenated quinoline and pyridine with alkoxides and phenoxides. Whereas for phenoxylation there is no need for any solvent, the addition of small amount of non-polar solvent is necessary during methoxylation for accurate monitoring of temperatures. Yields and conditions involved here constitute a noticeable improvement over classical methods within the frame of Green Chemistry. Specific MW effects were evidenced for phenoxylation and interpreted in terms of late position of the transition state along the reaction coordinates.
New methods of preparing cyclopentenone ketals: The photosolvolysis of 3-alkoxypyridinium tetrafluoroborates
Penkett,Simpson
, p. 93 - 95 (1999)
A new base catalysed method of ketal formation is reported, such that substituted cyclopentenone ketals are prepared from 3-alkoxypyridinium tetrafluoroborate salts.
Visible-Light Promoted C–O Bond Formation with an Integrated Carbon Nitride–Nickel Heterogeneous Photocatalyst
Vijeta, Arjun,Casadevall, Carla,Roy, Souvik,Reisner, Erwin
supporting information, p. 8494 - 8499 (2021/03/08)
Ni-deposited mesoporous graphitic carbon nitride (Ni-mpg-CNx) is introduced as an inexpensive, robust, easily synthesizable and recyclable material that functions as an integrated dual photocatalytic system. This material overcomes the need of expensive photosensitizers, organic ligands and additives as well as limitations of catalyst deactivation in the existing photo/Ni dual catalytic cross-coupling reactions. The dual catalytic Ni-mpg-CNx is demonstrated for C–O coupling between aryl halides and aliphatic alcohols under mild condition. The reaction affords the ether product in good-to-excellent yields (60–92 %) with broad substrate scope, including heteroaryl and aryl halides bearing electron-withdrawing, -donating and neutral groups. The heterogeneous Ni-mpg-CNx can be easily recovered from the reaction mixture and reused over multiple cycles without loss of activity. The findings highlight exciting opportunities for dual catalysis promoted by a fully heterogeneous system.
A highly stable all-in-one photocatalyst for aryl etherification: The NiIIembedded covalent organic framework
Chen, Hao,Dong, Wenbo,Hu, Jianxiang,Rao, Li,Wang, Pei,Wang, Shengyao,Xiang, Yonggang,Yang, Yi
, p. 5797 - 5805 (2021/08/23)
The efficient conversion of aryl bromides to the corresponding aryl alkyl ethers by dual nickel/photocatalysis has seen great progress, but difficulties of recycling the photosensitizer or nickel complexes cause problems of sustainability. Here, we report the design of a novel, highly stable vinyl bridge 2D covalent organic framework (COF) containing Ni, which combines the role of photosensitizer and reactive site. The as-prepared sp2c-COFdpy-Ni acts as an efficient heterogeneous photocatalyst for C-O cross coupling. The sp2c-COFdpy-Ni can be completely recovered and used repeatedly without loss of activity, overcoming the limitations of the prior methods. Preliminary studies reveal that strong interlayer electron transfer may facilitate the generation of the proposed intermediate sp2c-COFdpy-NiI in a bimolecular and self-sustained manner. This all-in-one heterogeneous photocatalyst exhibits good compatibility of substrates and tolerance of functional groups. The successful attempt to expand the 2D COFs with this new catalyst into photocatalytic organic transformation opens an avenue for photoredox/transition metal mediated coupling reactions.
Photorelease of Pyridines Using a Metal-Free Photoremovable Protecting Group
Dong, Zaizai,Fang, Xiaohong,Kou, Xiaolong,Tan, Weihong,Tang, Xiao-Jun,Wu, Yayun,Zhang, Zhen,Zhao, Rong,Zhou, Wei
supporting information, p. 18386 - 18389 (2020/08/24)
The photorelease of bioactive molecules has emerged as a valuable tool in biochemistry. Nevertheless, many important bioactive molecules, such as pyridine derivatives, cannot benefit from currently available organic photoremovable protecting groups (PPGs). We found that the inefficient photorelease of pyridines is attributed to intramolecular photoinduced electron transfer (PET) from PPGs to pyridinium ions. To alleviate PET, we rationally designed a strategy to drive the excited state of PPG from S1 to T1 with a heavy atom, and synthesized a new PPG by substitution of the H atom at the 3-position of 7-dietheylamino-coumarin-4-methyl (DEACM) with Br or I. This resulted in an improved photolytic efficiency of the pyridinium ion by hundreds-fold in aqueous solution. The PPG can be applied to various pyridine derivatives. The successful photorelease of a microtubule inhibitor, indibulin, in living cells was demonstrated for the potential application of this strategy in biochemical research.
Ionic Liquids as “Masking” Solvents of the Relative Strength of Bases in Proton Transfer Reactions
Zappacosta, Romina,Di Crescenzo, Antonello,Ettorre, Valeria,Fontana, Antonella,Pierini, Marco,Siani, Gabriella
, p. 35 - 41 (2018/02/09)
Equilibrium constants for the proton transfer reaction between pyridines and trifluoroacetic acid were measured in room-temperature ionic liquids (ILs) of different cation–anion compositions. The experimental equilibrium constants for ion-pair formation were corrected according to the Fuoss equation. The calculated equilibrium constants for the formation of free ions were taken as a quantitative measure of the base strength in IL solutions and compared with the relative constants in water. The effect of IL composition is discussed for a series of fixed IL anions and fixed IL cations. Finally, the sensitivity of the proton transfer reaction to the electronic effects of the substituent groups on the pyridine ring was quantified by applying the Hammett equation. A more marked levelling effect on the base strength was observed in ILs than in water. The Hammett reaction constants ρ were then correlated with solvent parameters according to a multi-parametric analysis, which showed that both specific hydrogen-bond donor/acceptor and non-specific interactions play an important role, with α and permittivity being the main parameters affecting the ability of the IL to differentiate the strength of the base.
Preparation method of cisapride key intermediate
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Paragraph 0026; 0027; 0032; 0033; 0038; 0039; 0044; 0045, (2019/01/06)
The invention provides a preparation method of a cisapride key intermediate. The preparation method includes the steps of adopting 3-pyridine as an initial raw material, 3-methoxypyridine is synthesized through nucleophilic substitution, 4-nitryl-3-methoxypyridine is prepared through a nitration reaction, a 4-nitryl-3-methoxyl-N-(3-(4-fluorophenoxy)propyl) quaternized pyridinium is prepared through quaternization, and the cisapride key intermediate, namely (cis)-N-(3-(4-fluorophenoxy)propyl)-4-amino-3-methoxy piperidine, is prepared through catalytic hydrogenation at last. The preparation method has the advantages of being low in cost, easy to operate and the like.
Synthesis method of heterocyclic compound 3-methoxypyridine
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Paragraph 0023, (2017/08/17)
The invention discloses a synthesis method of a heterocyclic compound 3-methoxypyridine. The method comprises the following steps: putting raw materials, i.e., 3-halogenated pyridine, hydrogen peroxide and acetic acid into a three-mouth flask, carrying out reaction for 4-8h at the temperature of 40-80 DEG C under the condition of stirring, recovering the acetic acid, adding a saturated sodium carbonate solution and stirring to enable a system to be alkaline, evaporating to remove water, then adding chloroform for washing, and carrying out vacuum distillation to obtain N-oxide-3-halogenated pyridine; respectively adding the N-oxide-3-halogenated pyridine, metal salt of alkyl alcohol, a catalyst A and alcohol into the three-mouth flask, carrying out reflux reaction for 5-8h under the condition of stirring, then cooling, neutralizing a product to be neutral, and carrying out distillation to obtain N-oxide-3-alkyloxypyridine; respectively adding the N-oxide-3-alkyloxypyridine, ferric trichloride, hydrazine hydrate, activated carbon and ethanol into the three-mouth flask, carrying out reaction at the temperature of 70 DEG C for 3h, cooling to room temperature, and carrying out vacuum distillation to obtain the 3-methoxypyridine. The synthesis method is high in intermediate conversion rate, mild in reaction conditions, safe in operation, low in price of raw materials and easy in raw material obtaining, thus being suitable for industrial production.
