1694-57-1Relevant academic research and scientific papers
Kinetic Energy Release and Position of Transition State During the Intramolecular Substitution of Ionized 2-Benzoyl Pyridines
Schubert, Ralf,Gruetzmacher, Hans-Friedrich
, p. 122 - 130 (1980)
The loss of substituents X from molecular ions of ortho substituted 2-benzoyl pyridines has been investigated as a function of the dissociation energy of the C-X bond.Comparison of unimolecular and collisional induced decompositions of the resulting + ions and reference ions arising from 3-hydroxypyridoindole shows that cyclic fragment ions are formed in every case by an intramolecular substitution reaction with the exception of the parent compound (X=H), which gives rise to a mixture of + ions with different structures.The heat of formation of the cyclic ion has been estimated experimentally and by calculation using thermochemical data, and from this value and the appearance energies, the activation energies of the reverse reactions have been evaluated for the different reaction systems.Measurement of the kinetic energy release during the substitution reactions shows that only part of the reverse activation energy is released as kinetic energy.The energy partitioning quotient varies from 0.37 to 0.08 depending on the dissociation energy of the C-X bond or the reaction enthalpy.A sudden change in the energy partitioning quotient is observed with increasing exothermicity of the reaction, paralleling the behaviour of similar reaction systems.These results are interpreted as a demonstration of the influence of the variation of transition state position on the energy partitioning quotient.
Atroposelective Synthesis of Axially Chiral Styrenes via an Asymmetric C–H Functionalization Strategy
Jin, Liang,Yao, Qi-Jun,Xie, Pei-Pei,Li, Ya,Zhan, Bei-Bei,Han, Ye-Qiang,Hong, Xin,Shi, Bing-Feng
, p. 497 - 511 (2020/02/20)
Axially chiral styrenes, which exhibit a chiral axis between a substituted alkene and an aromatic ring, have been largely overlooked. The hurdle is the lower barriers to rotation compared with that of their biaryl counterparts, rendering their asymmetric synthesis more difficult. We report herein the highly atroposelective synthesis via a C?H functionalization strategy of axially chiral styrenes with an open-chained alkene. Various axially chiral styrenes were produced by Pd(II)-catalyzed C?H alkenylation and alkynylation in good yields (up to 99%) and enantioselectivities (up to 99% ee) by using L-pyroglutamic acid as an inexpensive chiral ligand. The potent application of the styrene atropisomers is demonstrated by a Co(III)-catalyzed enantioselective C?H amidation of ferrocene with axially chiral styrene-type acid as chiral ligand. Experimental and computational studies were conducted to elucidate the reaction mechanism. The chiral induction model of the enantioselectivity-determining C?H bond activation step was also provided based on DFT calculations. Atropisomerism, which stems from the hindered rotation around a chiral axis, is widely present in natural products, pharmaceuticals, and chiral catalysts or ligands. In contrast to the well-investigated biaryl atropisomers, the asymmetric synthesis of axially chiral styrenes bearing a chiral axis between an alkene and an aromatic ring remains a significant challenge. Here, we report a highly atroposelective synthesis of styrene atropisomers with open-chained alkene by asymmetric C?H functionalization by using available L-pyroglutamic acid as a chiral ligand. This strategy enables rapid access to a broad range of enantio-enriched axially chiral styrenes under mild conditions in an atom- and step-economical manner. The resulting axially chiral styrenes are important precursors for further elaborations, including the transformation into axially chiral styrene-type acids, which were demonstrated to be efficient chiral ligands in Co(III)-catalyzed enantioselective C?H amidation reactions. An asymmetric C–H functionalization strategy with L-pGlu-OH as chiral ligand has been developed for the atroposelective synthesis of styrene atropisomers with open-chained alkene. The strategy allows quick access to a wide range of enantio-enriched axially chiral styrenes in high yields and enantioselectivities. The axially chiral styrene-derived chiral acids have been demonstrated to be an efficient type of chiral ligands in Co(III)-catalyzed enantioselective C?H amidation reactions.
Ortho-halogenated phenylpyridine ketone compound and preparation method thereof
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Paragraph 0110-0113, (2019/12/25)
The invention relates to an ortho-halogenated phenylpyridine ketone compound and a preparation method thereof. According to the invention, dibromohydantoin or dichlorohydantoin is taken as a halogenating reagent, and the ortho-halogenation of a diarylketo
Bifunctional Oxo-Tethered Ruthenium Complex Catalyzed Asymmetric Transfer Hydrogenation of Aryl N-Heteroaryl Ketones
Wang, Baigui,Zhou, Haifeng,Lu, Guoren,Liu, Qixing,Jiang, Xiaolan
supporting information, p. 2094 - 2097 (2017/04/28)
A facile asymmetric transfer hydrogenation of ortho-substituted aryl N-heteroaryl ketones and non-ortho-substituted N-oxide of aryl N-heteroaryl ketones using a readily available oxo-tethered ruthenium complex as a catalyst and sodium formate as a hydrogen source in an aqueous solution has been discovered. A variety of chiral aryl N-heteroaryl methanols were obtained with up to 99.9% ee.
Chlorpheniramine Analogues Reverse Chloroquine Resistance in Plasmodium falciparum by Inhibiting PfCRT
Deane, Karen J.,Summers, Robert L.,Lehane, Adele M.,Martin, Rowena E.,Barrow, Russell A.
supporting information, p. 576 - 581 (2014/06/09)
The emergence and spread of malaria parasites that are resistant to chloroquine (CQ) has been a disaster for world health. The antihistamine chlorpheniramine (CP) partially resensitizes CQ-resistant (CQR) parasites to CQ but possesses little intrinsic antiplasmodial activity. Mutations in the parasite's CQ resistance transporter (PfCRT) confer resistance to CQ by enabling the protein to transport the drug away from its site of action, and it is thought that resistance-reversers such as CP exert their effect by blocking this CQ transport activity. Here, a series of new structural analogues and homologues of CP have been synthesized. We show that these compounds (along with other in vitro CQ resistance-reversers) inhibit the transport of CQ via a resistance-conferring form of PfCRT expressed in Xenopus laevis oocytes. Furthermore, the level of PfCRT-inhibition was found to correlate well with both the restoration of CQ accumulation and the level of CQ resensitization in CQR parasites.
Facile one-pot synthesis of [1,2,3]triazolo[1,5-a]pyridines from 2-acylpyridines by copper(II)-catalyzed oxidative N-N bond formation
Hirayama, Tasuku,Ueda, Satoshi,Okada, Takahiro,Tsurue, Norihiko,Okuda, Kensuke,Nagasawa, Hideko
, p. 4156 - 4162 (2014/04/17)
An efficient and simple method for the synthesis of various [1,2,3]triazolo[1,5-a]pyridines has been established. The method involves a copper(II)-catalyzed oxidative N-N bond formation that uses atmospheric oxygen as the terminal oxidant following hydrazonation in one pot. The use of ethyl acetate as the solvent dramatically promotes the oxidative N-N bond-formation reaction and enables the application of oxidative cyclization in the efficient one-pot reaction. A mechanism for the reaction was proposed on the basis of the results of a spectroscopic study. In the same pot: [1,2,3]Triazolo[1,5-a] pyridines are synthesized from the corresponding 2-acylpyridines by a one-pot method, consisting of hydrazonation followed by oxidative cyclization through copper(II)-catalyzed N-N bond formation (see scheme).
CuII-catalyzed asymmetric hydrosilylation of diaryl- and aryl heteroaryl ketones: Application in the enantioselective synthesis of orphenadrine and neobenodine
Sui, Yao-Zong,Zhang, Xi-Chang,Wu, Jun-Wen,Li, Shijun,Zhou, Ji-Ning,Li, Min,Fang, Wenjun,Chan, Albert S. C.,Wu, Jing
, p. 7486 - 7492 (2012/07/27)
With certain amounts of sodium tert-butoxide and tert-butanol as additives, catalytic amounts of an inexpensive and easy-to-handle copper source Cu(OAc)2·H2O, a commercially available and air-stable non-racemic dipyridylphosphine ligand, as well as the stoichiometric desirable hydride donor polymethylhydrosiloxane (PMHS), formed a versatile in situ catalyst system for the enantioselective reduction of a broad spectrum of prochiral diaryl and aryl heteroarylketones in air, in high yields and with good to excellent enantioselectivities (up to 96 %). In particular, the practical viability of this process was evinced by its successful applications in the asymmetric synthesis of optically enriched potent antihistaminic drugs orphenadrine and neobenodine. Copyright
Ruthenium-catalyzed enantioselective hydrogenation of aryl-pyridyl ketones
Tao, Xiaoming,Li, Wanfang,Ma, Xin,Li, Xiaoming,Fan, Weizheng,Xie, Xiaomin,Ayad, Tahar,Ratovelomanana-Vidal, Virginie,Zhang, Zhaoguo
experimental part, p. 612 - 616 (2012/03/26)
Various substituted aryl-pyridyl ketones were hydrogenated in the presence of Ru-XylSunPhos-Daipen bifunctional catalytic system with enantiomeric excesses up to 99.5%. Upon introduction of a readily removable ortho-bromo atom to the phenyl ring, enantiomerically enriched 4-chlorophenylpyridylmethanol was obtained by hydrogenation method with 97.3% ee, which provided an important chiral intermediate for some histamine H1 antagonists.
Preparation and C-X reductive elimination reactivity of monoaryl Pd IV-X complexes in water (X = OH, OH2, Cl, Br)
Oloo, Williamson,Zavalij, Peter Y.,Zhang, Jing,Khaskin, Eugene,Vedernikov, Andrei N.
supporting information; experimental part, p. 14400 - 14402 (2011/01/04)
Monohydrocarbyl palladium(IV) complexes bearing OH, OH2, Br, and Cl ligands at the metal and supported by facially chelating 1-hydroxy-1,1-bis(2-pyridyl)methoxide were readily prepared in water at 0 °C. These complexes reductively eliminate Ar-
