- 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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- Catalytic Deoxygenation of Amine and Pyridine N-Oxides Using Rhodium PCcarbeneP Pincer Complexes
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Rhodium PCcarbeneP pincer complexes 1-L (L = PPh3, PPh2(C6F5), PCy3) readily facilitate deoxygenation of amine and pyridine N-oxides. The resulting complexes exhibit δ2-C= O coordination of the resulting keto POP pincer ligand. These δ2-Ca? O linkages in the metalloepoxide complexes are readily reduced by isopropyl alcohol and various benzylic alcohols. Thus, efficient catalytic deoxygenation of amine and pyridine N-oxides is possible using complexes 1-L and isopropyl alcohol. This represents a pioneering example of PCcarbeneP pincer complexes being used as catalysts for catalytic deoxygenation.
- Tinnermann, Hendrik,Sung, Simon,Cala, Beatrice A.,Gill, Hashir J.,Young, Rowan D.
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p. 797 - 803
(2020/03/13)
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- Preparation method 3,5- dibromopyridine
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The invention discloses a preparation method of 3,5-dibromopyridine, and belongs to the technical field of synthesis of chemical raw materials. The preparation method comprises the following steps: with pyridine as a raw material, and concentrated sulfuric acid and sulfoxide chloride as catalysts, dropwise adding bromine under a high-temperature condition, reacting to obtain 3,5-dibromopyridine, then refining with an alcoholic solution, and performing chromatographic determination on the obtained product, wherein the purity of the obtained product is as high as about 99.8%. The preparation method has the advantages that the reaction catalysts are easy to obtain, the reaction condition is easy to control, the reaction byproducts are less, the use of catalysts, such as nickel powder, copperpowder and aluminium chloride, is avoided, emission of three wastes is reduced, and the problems that in the prior art, pollution is serious, and the yield is low are solved.
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Paragraph 0032-0036; 0048-0052; 0061-0065; 0074-0078
(2020/05/14)
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- Synthesis, catalytic activity and medium fluorous recycle of fluorous analogues of PEPPSI catalysts
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PEPPSI complexes are air and moisture stable Pd catalysts, which can be used conveniently in many coupling reactions. With the aim to obtain Pd catalysts recyclable by fluorous separation methods, we modified the structure of commercial PEPPSI complexes by per- or polyfluoroalkylation in various positions. The modifications included the use of a linear polyfluoroalkyl group instead of one aryl group on the NHC ligand, perfluoroalkylation of pyridine ligand, and substitution of chloride ligands on Pd for perfluoroalkanoates or perfluoropolyoxaalkanoates. Comparison of catalytic activity of commercial catalysts with the modified ones in Suzuki-Miyaura cross-coupling reactions showed that the fluorous modifications mostly resulted in the increase of catalytic activity. Moreover, polyfluoroalkylation enabled efficient medium fluorous recycle of the modified catalysts using a two phase aqueous DMF/HFE 7500 ether system.
- ?im?nek, Ond?ej,Rybá?ková, Markéta,Svoboda, Martin,Kví?ala, Jaroslav
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- Synthesis and Physical Properties of Strained Doubly Phosphorus-Bridged Biaryls and Viologens
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New P/N-containing π-electron systems comprising fully planar biaryl arrays are synthesized by multiple radical phosphanylation. The biaryl moiety in these highly strained planar π-systems is rigidified by double P-bridging. The electronic properties of the core biaryl entity are varied by introducing N-donor substituents or by installing N-atoms within the π-system, thereby moving to the viologen core structure. The electrochemical and photophysical properties of these compounds are discussed and compared with those of related systems.
- Greulich, Tobias W.,Yamaguchi, Eriko,Doerenkamp, Carsten,Lübbesmeyer, Maximilian,Daniliuc, Constantin G.,Fukazawa, Aiko,Eckert, Hellmut,Yamaguchi, Shigehiro,Studer, Armido
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supporting information
p. 6029 - 6033
(2017/05/08)
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- Synthetic method of 3, 5-dibromopyridine
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The invention discloses a synthetic method of 3, 5-dibromopyridine. The synthetic method comprises the following steps of: (1) bromination reaction: dissolving 4-aminopyridine and azodiisobutyronitrile in carbon tetrachloride; adding N-bromosuccinimide at the temperature of 25 DEG C, carrying out central-control monitoring using a liquid phase till the reaction is complete, and treating to obtain 3, 5-dibromo-4-aminopyridine; (2) diazotization reaction: adding the 3, 5-dibromo-4-aminopyridine into concentrated sulfuric acid, dripping nitrosylsulfuric acid at the temperature of 48-55 DEG C after completely dissolving, stopping dripping when potassium iodide starch test paper is blue and does not fade, and then reacting for 1-1.5 hours; and (3) reduction reaction: continuously adding nickel powder and anhydrous ethanol solution into the solution, then carrying out refluxing reaction, cooling and then adjusting to be weakly alkaline by using concentrated sodium-hydroxide solution, and treating to obtain the 3, 5-dibromopyridine. The synthetic method disclosed by the invention has the advantages that the reaction condition is mild, the yield is high, the materials are easily available, the cost is lower, the process route is short, and the product purity is high and has industrial prospect.
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- An Efficient Deoxgenation of Heteroaromatic N-Oxides Using Zinc Dust/Ammonium Formate Reagent System
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Heteroaromatic N-oxides were readily and selectively deoxygenated to the corresponding bases with zinc/ammonium formate reagent system.
- Balicki, Roman,Cybulski, Marcin,Maciejewski, Grzegorz
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p. 4137 - 4141
(2007/10/03)
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- A mild and selective deoxygenation of N-oxides with ammonium formate as a catalytic hydrogen transfer agent
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Ammonium formate catalytic transfer hydrogenation in the presence of raney nickel has shown utility for mild and selective deoxygenation of heteroaromatic N-oxides in neutral medium.
- Balicki, Roman,Maciejewski, Grzegorz
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p. 1681 - 1683
(2007/10/03)
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- A mild deoxygenation of heteroaromatic N-oxides by formamidinesulfinic acid
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Various heteroaromatic N-oxides were efficiently deoxygenated to the corresponding bases under mild conditions using formamidinesulfinic acid (thiourea S,S-dioxide).
- Balicki, Roman,Chmielowiec, Urszula
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p. 1105 - 1107
(2007/10/03)
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- TiCl4/NaI - A Novel, Efficient Reagent for Mild Reduction of the N-O Bond in Amine N-Oxides and Nitrones
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Heteroaromatic N-oxides and nitrones were readily and selectively deoxygenated to the corresponding bases or imines in excellent yields with the TiCl4/NaI reagent system.
- Balicki, Roman
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p. 647 - 649
(2007/10/02)
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- HOMOTRANSMETALLATION DES HALOGENO-3 PYRIDINES BROMEES EN -2 OU -4 PAR LE N-BUTYLLITHIUM. PROPOSITION D'UN NOUVEAU MECANISME DE TELESUBSTITUTION DU BROME.
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These are new examples of the homotransmetallation reaction.Instead of the ordinary bromo-metal exchange it is possible to obtain selectively from the 2-bromo 3-fluoro or 2-bromo 3-chloro pyridines the 2-bromo 3-halogeno 4-lithio pyridines, which is very interesting for synthetic utility.From the 4-bromo 3-halogeno pyridines, we can see an isomerization with an halogen dance mechanism and we obtain the 5-bromo 3-halogeno 4-lithio pyridines.In the case of the 2-bromo 3-fluoro pyridine we explain a telesubstitution of bromine from 2 to 4 by a transitory homotransmetallation reaction during the Li-Br exchange.
- Mallet, M.,Queguiner, G.
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p. 2253 - 2262
(2007/10/02)
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- BROMINATION OF PYRIDINE IN THE PRESENCE OF SOME LEWIS ACIDS
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The bromination of pyridine in the form of complexes with some Lewis acids and in the presence of catalytic amounts of the latter was studied.It is shown that bromination takes place readily at ca. 100 deg C in the presence of catalysts such as AlCl3, ZnCl2, SbCl3, InCl3, TeCl4, and HgCl2.The principal bromination products are 3-bromopyridine and 3,5-dibromopyridine.The problem of the possibility of so-called ? back-bonding in the case of elements of the higher periods (particurarly In, Te, and Sb) is discussed.
- Lokhov, R. E.,Lokhova, S. S.,Gaidarova, N. M.,Belen'kii, L. I.
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p. 923 - 926
(2007/10/02)
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