- Ruthenium(II)-Catalyzed Oxidative Annulation Reactions of Arylimidazolium Salts via N-Heterocyclic Carbene-Directed C-H Activation
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An efficient ruthenium(II)-catalyzed oxidative annulation reaction of various arylimidazolium salts with alkynes via N-heterocyclic carbene-directed C-H activation to obtain substituted benzo[ij]imidazo[2,1,5-de]quinolizinium salts is reported. This catalytic reaction proceeds in an excellent regioselective manner when using unsymmetrical alkynes as reactants. The intermediate mono-annulated products can be obtained by reducing the amount of catalyst. Two catalytically competent N-heterocyclic carbene-based cyclometallated ruthenium(II) complexes have been isolated and characterized, which represent the key intermediates in the catalytic cycle. Moreover, most of the products show a strong fluorescent property, indicating their potential for making new light-emitting materials.
- Li, Renhe,Hu, Yang,Liu, Ran,Hu, Ruofang,Li, Bin,Wang, Baiquan
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- Synthesis of substituted benzo[ij]imidazo[2,1,5-de]quinolizine by rhodium(iii)-catalyzed multiple C-H activation and annulations
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The cascade oxidative annulation reactions of aryl imidazoles with two molecules of alkynes via multiple C-H activation proceed efficiently in the presence of [Cp?RhCl2]2 and Cu(OAc)2·H2O to give substituted benzo[ij]imidazo[2,1,5-de]quinolizine-based polyheteroaromatic compounds. This method is compatible with various functional groups, which are very useful for further synthetic transformations.
- Ge, Qingmei,Li, Bin,Wang, Baiquan
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- Rhodium(iii)-catalyzed cascade oxidative annulation reactions of aryl imidazolium salts with alkynes involving multiple C-H bond activation
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The cascade oxidative annulation reactions of aryl imidazolium salts with alkynes proceed efficiently in the presence of [CpRhCl2]2 and Cu(OAc)2·H2O to give substituted imidazo[1,2-a]-quinolinium salts and benzo[ij]imidazo[2,1,5-de]quinolizinium salts. The reactions were through the normal and abnormal N-heterocyclic carbene (NHC)-directed cyclometalation, alkyne insertion into the Rh-C bond, and reductive elimination of alkenyl and NHC ligands. The reactions are highly regioselective with unsymmetrical alkynes and can be achieved stepwise by controlling the reaction conditions. This provides a new application of NHCs as directing groups and substrates in the synthesis of fused N-heterocyclic compounds. The N-substituting group of the benzo[ij]imidazo[2,1,5-de]quinolizinium salts could be removed successfully with pyridine to afford benzo[ij]imidazo[2,1,5-de]quinolizines in excellent yields. Moreover, some of the benzo[ij]imidazo[2,1,5-de]quinolizinium salts exhibit intense fluorescence which might be useful in organic electronic materials.
- Ge, Qingmei,Li, Bin,Song, Haibin,Wang, Baiquan
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- Ligand-Controlled, Tunable Copper-Catalyzed Radical Divergent Trifluoromethylation of Unactivated Cycloalkenes
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The Cu-catalyzed high-chemoselective trifluoromethylation reactions of unactivated cycloalkenes via the modulation of appropriate ligands have been explored. The Cu(I)/appropriate ligands-catalytic systems overcome the key challenge in differentiating two pathways involving radical intermediates and provide a ligand-controlled approach for site-specific spiro-aryltrifluoromethylation and chlorotrifluoromethylation to afford trifluoromethylated spiro-tetrahydroquinoline compounds and vicinal Cl-containing trifluoromethyl cycloalkanes. Moreover, compared with reported chlorine sources, 1,2-dichloroethane is used as more green and economical feedstock for chlorotrifluoromethylation. (Figure presented.).
- Wang, Qi,Zang, Zhong-Lin,Jie, Mi,Luo, Li-Hua,Yang, Dan,Zhou, Cheng-He,Cai, Gui-Xin
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supporting information
p. 5284 - 5291
(2021/10/25)
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- Synthesis of Polysubstituted Iodoarenes Enabled by Iterative Iodine-Directed para and ortho C?H Functionalization
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Among halogenated aromatics, iodoarenes are unique in their ability to produce the bench-stable halogen(III) form. Earlier, such iodine(III) centers were shown to enable C?H functionalization ortho to iodine via halogen-centered rearrangement. The broader implications of this phenomenon are explored by testing the extent of an unusual iodane-directed para C?H benzylation, as well as by developing an efficient C?H coupling with sulfonyl-substituted allylic silanes. Through the combination of the one-shot nature of the coupling event and the iodine retention, multisubstituted arenes can be prepared by sequentially engaging up to three aromatic C?H sites. This type of iodine-based iterative synthesis will serve as a tool for the formation of value-added aromatic cores.
- Wu, Yichen,Bouvet, Sébastien,Izquierdo, Susana,Shafir, Alexandr
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supporting information
p. 2617 - 2621
(2019/01/04)
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- Ruthenium(II)-Catalyzed Synthesis of Spirobenzofuranones by a Decarbonylative Annulation Reaction
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The first decarbonylative insertion of an alkyne through C?H/C?C activation of six-membered compounds is reported. The Ru-catalyzed reaction of 3-hydroxy-2-phenyl-chromones with alkynes works most efficiently in the presence of the ligand PPh3 to provide spiro-indenebenzofuranones. Unlike previously reported metal-catalyzed decarbonylative annulation reactions, in the present decarbonylative annulation reaction, the annulation occurs before extrusion of carbon monoxide.
- Kaishap, Partha P.,Duarah, Gauri,Sarma, Bipul,Chetia, Dipak,Gogoi, Sanjib
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supporting information
p. 456 - 460
(2018/02/21)
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- Rh-Catalyzed Annulation of ortho-C?H Bonds of 2-Arylimidazoles with 1,4,2-Dioxazol-5-ones toward 5-Arylimidazo[1,2-c]quinazolines
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A Rh-catalyzed unique and direct approach for constructing a series of 5-arylimidazo[1,2-c]quinazolines in moderate to excellent yields from simple and readily available 2-arylimidazoles and 3-phenyl-1,4,2-dioxazol-5-ones was described. This procedure pro
- Wu, Xiaopeng,Sun, Song,Xu, Shengbo,Cheng, Jiang
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supporting information
p. 1111 - 1115
(2018/01/27)
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- Synthesis of Spiro-dihydroquinoline and Octahydrophenanthrene Derivatives via Palladium-Catalyzed Intramolecular Oxidative Arylation
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A method for intramolecular sp2 C-H oxidative arylation of unactivated cyclic olefins has been developed to access spiro-dihydroquinoline and octahydrophenanthrene derivatives in a straightforward and efficient manner. Bearing picolinamide as a directing group, the alkenyl anilines cyclized to afford spiro-dihydroquinolines in moderate to excellent yields via direct oxidative arylation, while the alkenyl benzylamines furnished the octahydrophenanthrene derivatives in moderate yields via sequential oxidative arylation and double acetoxylation.
- Zang, Zhong-Lin,Karnakanti, Shuklachary,Zhao, Sheng,Hu, Ping,Wang, Zhen,Shao, Pan-Lin,He, Yun
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supporting information
p. 1354 - 1357
(2017/03/23)
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- Metal-free photochemical aromatic perfluoroalkylation of α-cyano arylacetates
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We report here an operationally simple protocol for the direct aromatic perfluoroalkylation and trifluoromethylation of α-cyano arylacetates. This metal-free approach, which occurs at ambient temperature and under visible-light irradiation, is driven by t
- Nappi, Manuel,Bergonzini, Giulia,Melchiorre, Paolo
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supporting information
p. 4921 - 4925
(2014/05/20)
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- Exploring a unique reactivity of N-heterocyclic carbenes (NHC) in rhodium(III)-catalyzed intermolecular C-H activation/annulation
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Disclosed herein is the unique conjugative role of N-heterocyclic carbene (NHC) ligands as a directing group in aromatic C-H activation, coupled with a facile NHC-alkenyl annulative reductive elimination which guided the RhIII-catalyzed intermo
- Ghorai, Debasish,Choudhury, Joyanta
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supporting information
p. 15159 - 15162
(2014/12/11)
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- Catalytic arene H/D exchange with novel rhodium and iridium complexes
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Three novel pendant acetate complexes, [Rh(bdmpza)Cl3] -M+, [Rh(bdmpza)Cl2(py)], and [Ir(bdmpza)Cl3]-M+ (bdmpza = bis(3,5-dimethylpyrazol-1-yl) acetate, M+ = Li+, Na +), were synthesized. Abstraction of halide from these complexes with silver salts yielded species capable of C-H activation of arenes. The catalytic H/D exchange reaction between benzene and trifluoroacetic acid-d was optimized, and these conditions were used to evaluate H/D exchange in other arenes. Branched alkyl substituents in alkyl aromatics showed an affinity toward deuterium exchange in the β-alkyl position only. DFT calculations were performed to determine the mechanism of H/D exchange.
- Rhinehart, Jennifer L.,Manbeck, Kimberly A.,Buzak, Sara K.,Lippa, Geoffrey M.,Brennessel, William W.,Goldberg, Karen I.,Jones, William D.
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experimental part
p. 1943 - 1952
(2012/04/23)
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- Sequestered alkyllithiums: Why phenyllithium alone is suitable for betaine-ylide generation
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The key step in the trans-selective modification of the Wittig reaction is the α-lithiation of the lithium bromide coordinated ylide - aldehyde adduct (the so-called "P-betaine"). Only phenyllithium effects this deprotonation rapidly and cleanly. Alkyllithiums (in particular, butyl-, sec-butyl-, and tert-butyllithium) react only sluggishly and incompletely, being tied up in very stable mixed aggregates with the lithium alkoxide part of the betaines.
- Wang, Qian,Deredas, Dariusz,Huynh, Cyril,Schlosser, Manfred
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p. 570 - 574
(2007/10/03)
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