- Highly Chemoselective Deoxygenation of N-Heterocyclic N-Oxides Using Hantzsch Esters as Mild Reducing Agents
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Herein, we disclose a highly chemoselective room-temperature deoxygenation method applicable to various functionalized N-heterocyclic N-oxides via visible light-mediated metallaphotoredox catalysis using Hantzsch esters as the sole stoichiometric reductant. Despite the feasibility of catalyst-free conditions, most of these deoxygenations can be completed within a few minutes using only a tiny amount of a catalyst. This technology also allows for multigram-scale reactions even with an extremely low catalyst loading of 0.01 mol %. The scope of this scalable and operationally convenient protocol encompasses a wide range of functional groups, such as amides, carbamates, esters, ketones, nitrile groups, nitro groups, and halogens, which provide access to the corresponding deoxygenated N-heterocycles in good to excellent yields (an average of an 86.8% yield for a total of 45 examples).
- An, Ju Hyeon,Kim, Kyu Dong,Lee, Jun Hee
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supporting information
p. 2876 - 2894
(2021/02/01)
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- Production method of 2, 6-dichloropyridine
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The invention discloses a production method of 2,6-dichloropyridine, which comprises the following steps: introducing pyridine, inert gas and chlorine into a photochlorination reaction device, and carrying out a photochlorination reaction at 150-195 DEG C under an ultraviolet light source which only emits light with the wavelength of 300-460nm.
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Paragraph 0027-0060
(2020/05/01)
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- Catalyst-Free N-Deoxygenation by Photoexcitation of Hantzsch Ester
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A mild and operationally simple protocol for the deoxygenation of a variety of heteroaryl N-oxides and nitroarenes has been developed. A mixture of substrate and Hantzsch ester is proposed to result in an electron donor-acceptor complex, which upon blue-light irradiation undergoes photoinduced electron transfer between the two reactants to afford the products. N-oxide deoxygenation is demonstrated with 22 examples of functionally diverse substrates, and the chemoselective reduction of nitroarenes to the corresponding hydroxylamines is also shown.
- Cardinale, Luana,Jacobi Von Wangelin, Axel,Konev, Mikhail O.
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supporting information
(2020/02/15)
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- Method for preparing 2,6-dichloropyridine by pyridine liquid-phase photochlorination
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The invention relates to a method for preparing 2,6-dichloropyridine with product purity greater than or equal to 99.0% by using chlorotrifluoromethylbenzene as a solvent for a reaction between pyridine and chlorine. The preparing process comprises the steps as follows: by using the pyridine and the chlorine as initial raw materials and using the chlorotrifluoromethylbenzene as the solvent, continuously performing a chlorination reaction on the pyridine and the chlorine under the irradiation of ultraviolet light; and cooling a chlorination reaction product and the solvent to obtain pyridine chloride solution. The method has the advantages that 1, a precedent of directly preparing the 2,6-dichloropyridine in a high selectivity mode by a liquid-phase photochlorination reaction is set, and not only is the 2,6-dichloropyridine product with purity greater than or equal to 99.0% obtained, but also the method is easy for industrial production; and 2, not only is recycling of the separation solvent in the preparing process of the 2,6-dichloropyridine product with purity greater than or equal to 99.0% implemented, but also the aims of low pollution, low energy consumption and low cost in the preparing process are fulfilled.
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Paragraph 0016-0027; 0028; 0029; 0031
(2019/01/23)
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- Method and production line for preparing 2,6-dichloropyridine through gas phase photochlorination of pyridine
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The present invention relates to a method for preparing 2,6-dichloropyridine with product purity greater than or equal to 99.0% through gas phase photochlorination of pyridine by using trifluoromethyl chlorobenzene as a solvent for reaction between pyridine and chlorine gas. Gasified pyridine and heated chlorine gas are enabled to continuously experience chlorination reaction under irradiation of ultraviolet light by using gasified pyridine and heated chlorine gas as starting materials and using heated trifluoromethyl chlorobenzene as a solvent, and a gas phase reaction product and the solvent are cooled to obtain pyridine chlorination solution. Advantages: firstly, it pioneers the precedent of direct and high-selectivity preparation of 2,6-dichloropyridine through gas phase photochlorination, and not only can the 2,6-dichloropyridine product with purity greater than or equal to 99.0% be obtained, but also industrial production is facilitated; and secondly, the selectivity of pyridine chlorination is high, the chlorination solution is subjected to crude distillation to separate high-boiling-point substances, the crude distillate is subjected to cooling crystallization or rectification to separate the solvent, the solvent is reused, and not only can the 2,6-dichloropyridine product with purity greater than or equal to 99.0% be obtained, but also the purposes of no pollution, low energy consumption and low cost can be realized.
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Page/Page column 5-7
(2019/10/29)
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- Pyridine liquid phase light chlorinated preparation 2, 6 - dichloro pyridine method
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The invention relates to a kind of the trifluoromethyl chlorobenzene as the solvent, 2 - chloro pyridine and chlorine as the raw material, process for preparing the product purity ≥ 99.0% of 2, 6 - dichloro pyridine production method, in order to 2 - chloro pyridine, chlorine as the starting material, trifluoromethyl chlorobenzene as the solvent, in the 150 °C -200 °C temperature, ultraviolet light irradiation under the continuous feed of the liquid phase chlorination reaction, to obtain the chloride, wherein the chloride in pyridine 2, 6 - dichloro pyridine content ≥ 97%, chlorinated rough steaming, crystallization separation or distillation purification process, get the purity ≥ 99.0% of 2, 6 - chlorinate, yield is greater than 90%. Advantages: produced by the reaction of 2, 6 - dichloro pyridine high selectivity, adding solvent to the reaction device overcomes the problem of exhaust gas easy blockage of the pipe, reaction process is easy to control, help to realize commercial process.
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Paragraph 0012-0035
(2019/07/05)
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- An Improved Rapid and Mild Deoxygenation of Amine N-oxides
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An improved mild and selective method for the deoxygenation of a variety of amine N-oxides has been carried out in the presence of silica gel under mild conditions at room temperature to afford corresponding amines in relatively good yields without purification. The reaction is tolerant of a variety of functional groups such as hydroxyl, ester, acid, carbonyl, and cyano groups, as well as halogens. This method would be of great utility to synthesize various pyridines and amines easily.
- Rajesh
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p. 486 - 491
(2017/12/29)
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- The radical reaction from a fluorine-containing compound
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PROBLEM TO BE SOLVED: To provide a radical reaction substitute solvent for carbon tetrachloride which has been used heretofore as a radical reaction solvent. SOLUTION: A chain fluorine-containing hydrocarbon represented by formula (1): CmH2m+2-nFn(wherein m is an integer of 3-10 and n is an integer of 1 to 2m+1) or a cyclic fluorine-containing hydrocarbon represented by formula (2): CpH2p-qFq(wherein p is an integer of 3-10 and q is an integer of 1 to 2p-1) is used as a solvent for various radical reactions. COPYRIGHT: (C)2011,JPO&INPIT
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Paragraph 0033-0034
(2017/01/05)
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- Copper-catalyzed conversion of aryl and heteroaryl bromides into the corresponding chlorides
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An efficient method for the synthesis of aryl and heteroaryl chlorides is described. The reactions of aryl and heteroaryl bromides with tetramethylammonium chloride proceeded smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding chlorides in satisfactory to excellent yields.
- Feng, Xiujuan,Qu, Yiping,Han, Yanlei,Yu, Xiaoqiang,Bao, Ming,Yamamoto, Yoshinori
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supporting information
p. 9468 - 9470
(2012/10/29)
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- Reduction of amine N-oxides by diboron reagents
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Facile reduction of alkylamino-, anilino-, and pyridyl-N-oxides can be achieved via the use of diboron reagents, predominantly bis- (pinacolato)- and in some cases bis(catecholato)diboron [(pinB)2 and (catB)2, respectively]. Reductions occur upon simply mixing the amine N oxide and the diboron reagent in a suitable solvent, at a suitable temperature. Extremely fast reductions of alkylamino- and anilino-N-oxides occur, whereas pyridyl-N-oxides undergo slower reduction. The reaction is tolerant of a variety of functionalities such as hydroxyl, thiol, and cyano groups, as well as halogens. Notably, a sensitive nucleoside N-oxide has also been reduced efficiently. The different rates with which alkylamino- and pyridyl-N-oxides are reduced has been used to perform stepwise reduction of the N,N-dioxide of (S)-(-)-nicotine. Because it was observed that (pinB)2 was unaffected by the water of hydration in amine oxides, the feasibility of using water as solvent was evaluated. These reactions also proceeded exceptionally well, giving high product yields. In constrast to the reactions with (pinB)2, triethylborane reduced alkylamino-N oxides, but pyridine N-oxide did not undergo efficient reduction even at elevated temperature. Finally, the mechanism of the reductive process by (pinB)2 has been probed by 1H and 11B NMR. (Figure presented) ; 2011 American Chemical Society.
- Kokatla, Hari Prasad,Thomson, Paul F.,Bae, Suyeal,Doddi, Venkata Ramana,Lakshman, Mahesh K.
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experimental part
p. 7842 - 7848
(2011/12/01)
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- Cu(I)-mediated deoxygenation of N-oxides to amines
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A mild and highly efficient deoxygenation of variety of N-oxides using an inexpensive CuX, or a CuX-Zn or CuX-Al couple is described.
- Singh, Sunil Kumar,Srinivasa Reddy,Mangle, Mangesh,Ravi Ganesh
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p. 126 - 130
(2007/10/03)
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- Reaction of N-fluoropyridinium fluoride with isonitriles: A convenient route to picolinamides
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Reaction of N-fluoropyridinium fluoride generated in situ with a series of isonitriles led to the formation of the corresponding picolinamides in good yields. A similar reaction sequence for quinoline yielded the respective derivatives of 2-quinoline carboxylic acid. The proposed reaction mechanism involves the intermediate formation of a highly reactive carbene species.
- Kiselyov, Alexander S.
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p. 2279 - 2282
(2007/10/03)
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- Process for preparation of 2-chloropyridine
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Described are processes for producing 2-chloropyridine by reacting pyridine with molecular chlorine in the vapor phase in the presence of a catalyst which includes an organic compound which generates free radicals under the conditions of the reaction.
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Page column 4-5
(2010/01/31)
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- Unusual C-6 lithiation of 2-chloropyridine-mediated by BuLi-Me2N(CH2)2OLi. New access to 6-functional-2-chloropyridines and chloro-bis-heterocycles
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Formula Presented The reaction of 2-chloropyridine with alkylithium generally results in nucleophilic addition leading to the loss of chlorine atom while exclusive directed ortho metalation is obtained using LDA. Herein it is shown that the BuLi-Me2
- Choppin, Sabine,Gros, Philippe,Fort, Yves
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p. 803 - 805
(2007/10/03)
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- Asymmetric catalysis by a chiral ruthenium porphyrin: Epoxidation, hydroxylation, and partial kinetic resolution of hydrocarbons
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matrix presented A new member of our D2 symmetry ruthenium porphyrins is shown to be a most selective catalyst for asymmetric epoxidation of terminal and trans-disubstituted olefins. The same catalyst displays some selectivity in kinetic resolution of secondary alcohols and in what appears to be the first example of catalytic enantioselective hydroxylation of tertiary alkanes.
- Gross, Zeev,Ini, Santiago
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p. 2077 - 2080
(2008/02/10)
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- Selective deoxygenation of heteroaromatic N-oxides with olefins catalyzed by ruthenium porphyrin
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A new convenient method of deoxygenation of heteroaromatic N-oxides is described. Ruthenium porphyrin was used as a catalyst and this method expressed high yields for o-substituted pyridine N-oxides, quinoline N-oxide derivatives, acridine N-oxide, etc. under mild conditions. Moreover, nitro-, benzyloxy-, and ketone carbonyl groups, which can be affected by the usual deoxygenation methods such as catalytic hydrogenation or borane reduction, were retained.
- Nakagawa, Hiroshi,Higuchi, Tsunehiko,Kikuchi, Kazuya,Urano, Yasuteru,Nagano, Tetsuo
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p. 1656 - 1657
(2007/10/03)
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- Substituent Effect on the Chlorination of 2-Alkoxypyridines to give 2-Chloropyridines under Vilsmeier-Haack Conditions
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Various substituted 2-alkoxypyridines were converted into the corresponding 2-chloropyridines in 28-91% yields by use of POCl3 and DMF, in which the methyl, halogen, ester and nitro groups displayed an activating effect; in contrast, an amino group exhibited a deactivating effect.
- Lai, Long-Li,Lin, Pen-Yuan,Wang, Jy-Shih,Hwu, Jih Ru,Shiao, Min-Jen,Tsay, Shwu-Chen
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p. 194 - 195
(2007/10/03)
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- Preparation of substituted 2-chloropyridines
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A process for the preparation of a substituted 2-chloropyridine derivatives of the formula STR1 in which R1, R2, R3 and R4 represent hydrogen or various other radicals, which comprises reacting a pyridine-1-oxide of the formula STR2 with an aromatic carbonyl chloride in the presence of an inert organic solvent and in the presence of an acid acceptor at a temperature between about -20° C. and 200° C.
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- Process for the preparation of substituted 2-chloropyridines
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A new process has been found for the preparation of substituted 2-chloropyridine derivatives of the formula (I) STR1 wherein R1 to R4 have the meanings as defined in the description. The new process is characterized in that pyridine 1-oxides of the formula II STR2 are reacted with a chlorine-containing phosphoric acid derivative from the series of the chlorophosphoric esters and chlorophosphoramides in the presence of an inert organic solvent and in the presence of an acid acceptor at temperatures between -20° C. and 200° C., and the resulting product is separated further, if appropriate. Compound (I) is known as an intermediate product for medicaments (cf.DE-A 2,812,585) or for insecticidel nitromethylene derivatives (cf. EP-A 163,855).
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- A Convenient Synthesis of Halogenated 2-Chloropyridines by Transformation of Halogenated 2-Methoxypyridines under Vilsmeier-Haack Conditions
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Several halogenated 2-chloropyridines 2a-2h were conveniently synthesized by transformation of halogenated 2-methoxypyridines 1a-1h under Vilsmeier-Haack conditions in a yield of 50-71percent.
- Shiao, Min-Jen,Shyu, Li-Ming,Tarng, Kai-Yih,Ma, Ying-Tsun
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p. 2971 - 2977
(2007/10/02)
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- Preparation of 2-Fluoropyridines via Base-Induced Decomposition of N-Fluoropyridinium Salts
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N-Fluoropyridinium salts with either BF4-, SbF6-, or PF6- as a counteranion were treated with excess base such as triethylamine at room temperature to give 2-fluoropyridine in good yield.This method was succesfully applied to the preparation of 2-fluoropyridine derivatives possessing electron-donating or -withdrawing substituents using substituted N-fluoropyridinium tetrafluoroborates.Pyridine-F2 compounds produced through reactions of pyridines with molecular fluorine were also treated with base to give 2-fluoropyridines but in low yields.These reactions are considered to occur through a carbene mechanism as follows: a novel N-F-containing cyclic carbene (3), generated from the N-fluoropyridinium salts by 2-proton abstraction, reacts with fluorine atoms from counteranions such as BF4-, SbF6-, or PF6-, followed by elimination of F- from the N-F moiety, to yield 2-fluoropyridines.Previously reported findings in reactions of pyridines with molecular fluorine are explained on the basis of this mechanism.
- Umemoto, Teruo,Tomizawa, Ginjiro
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p. 1726 - 1731
(2007/10/02)
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- DIRECT FLUORINATION OF SUBSTITUTED PYRIDINES
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The direct fluorination of pyridines bearing alkyl, halogen, ester, or ketone functions has been employed to prepare the corresponding 2-fluoro-substituted pyridines.
- Puy, Michael Van Der
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p. 255 - 258
(2007/10/02)
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