1079-02-3Relevant academic research and scientific papers
Rhodium-Catalyzed Spiro Indenyl Benzoxazine Synthesis via C-H Activation/Annulation of 3-Aryl-2H-Benzo[b][1,4]oxazines and Alkynes
Tan, Heng,Laishram, Ronibala Devi,Zhang, Xuexin,Shi, Guangrui,Li, Kangkui,Chen, Jingchao
, p. 4542 - 4546 (2020)
The rhodium (III)-catalyzed annulation of 3-Aryl-2H-Benzo[b][1,4]oxazines with alkynes via C–H activation has been developed. This reaction afforded a series of spiro indenyl benzoxazine in high yields under mild reaction condition with good functional group tolerance.
Rhodium(III)-catalyzed [4+1] annulation of aromatic and vinylic carboxylic acids with allenes: An efficient method towards vinyl-substituted phthalides and 2-furanones
Gandeepan, Parthasarathy,Rajamalli, Pachaiyappan,Cheng, Chien-Hong
, p. 9198 - 9203 (2015)
A highly regio- and stereoselective synthesis of 3,3-disubstituted phthalides from aryl carboxylic acids and allenes using a rhodium(III) catalyst has been demonstrated. The reaction features broad functional group tolerance and provides a simple and straightforward route to the synthesis of various 3-vinyl-substituted phthalides. Furthermore, the catalytic reaction can also be applied to the synthesis of biologically active 5-vinyl-substituted 2-furanones from α,β-unsaturated carboxylic acids and allenes. The reactions proceed through a carboxylate-assisted ortho-C-H activation and [4+1] annulation. The preliminary mechanistic studies suggest that a C-H cleavage is the rate-determining step. An efficient synthesis of highly substituted phthalides and 2-furanones from aryl and vinyl carboxylic acids with allenes by using a RhIII catalyst is demonstrated (see scheme). The reactions proceed through a carboxylate-assisted ortho-C-H activation and [4+1] annulation.
Palladium-Catalyzed Electrochemical C-H Bromination Using NH4Br as the Brominating Reagent
Yang, Qi-Liang,Wang, Xiang-Yang,Wang, Tong-Lin,Yang, Xiang,Liu, Dong,Tong, Xiaofeng,Wu, Xin-Yan,Mei, Tian-Sheng
, p. 2645 - 2649 (2019)
The palladium-catalyzed electrochemical C-H bromination of benzamide derivatives under divided cells is developed, in which NH4Br serves as a brominating reagent and electrolyte. The protocol avoids the use of chemical oxidants and provides an alternative method for the synthesis of aryl bromides.
Diastereoselective [3+2] Annulation of Aromatic/Vinylic Amides with Bicyclic Alkenes through Cobalt-Catalyzed C-H Activation and Intramolecular Nucleophilic Addition
Gandeepan, Parthasarathy,Rajamalli, Pachaiyappan,Cheng, Chien-Hong
, p. 4308 - 4311 (2016)
A highly diastereoselective method for the synthesis of dihydroepoxybenzofluorenone derivatives from aromatic/vinylic amides and bicyclic alkenes is described. This new transformation proceeds through cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group. Transition-metal-catalyzed C-H activation reactions of secondary amides with alkenes usually lead to [4+2] or [4+1] annulation; to the best of our knowledge, this is the first time that a [3+2] cycloaddition is described in this context. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. Mechanistic studies imply that the C-H bond cleavage may be the rate-limiting step. [3+2] instead of [4+2] or [4+1]: The diastereoselective [3+2] annulation of secondary amides with alkenes proceeds by cobalt-catalyzed C-H activation and intramolecular nucleophilic addition to the amide functional group under mild conditions. Mechanistic studies suggest that the C-H bond cleavage is the rate-limiting step.
Cobalt-catalyzed electrochemical C–H/N–H functionalization of N-(quinolin-8-yl)benzamide with isocyanides
Chen, Jinkang,Jin, Licheng,Zhou, Jian,Jiang, Xinpeng,Yu, Chuanming
, p. 2054 - 2058 (2019)
An efficient synthesis of functionalized iminoisoindolinone derivatives has been achieved via a mild electrochemical oxidative C–H/N–H functionalization/intramolecular annulations with isocyanides in undivided cell equipped with a nickel cathode. In the presence of earth abundant cobalt catalyst, versatile iminoisoindolinone derivatives obtained in good yields and in a sustainable manner by using electricity as an oxidant in place of stoichiometric amount of silver and copper salts.
Mechanistic study of the rhodium-catalyzed carboxylation of simple aromatic compounds with carbon dioxide
Suga, Takuya,Saitou, Takanobu,Takaya, Jun,Iwasawa, Nobuharu
, p. 1454 - 1462 (2017)
A detailed mechanism of the Rh(i)-catalyzed carboxylation of simple aromatic compounds via C-H bond activation was investigated. Kinetic studies with model compounds of the postulated key intermediates revealed that 14-electron complexes, RhMe(dcype) and RhPh(dcype), participated in the C-H bond activation step and the carboxylation step, respectively. Interestingly, the undesired carboxylation of RhMe(dcype) to give acetic acid was found to be much faster than the desired C-H bond activation reaction under stoichiometric conditions, however, the C-H bond activation reaction could occur under catalytic conditions. Careful controlled experiments revealed that C-H bond activation using RhMe(dcype) became competitive with its direct carboxylation under the condition that the concentration of CO2 in the liquid phase was rather low. This factor could be controlled to some extent by mechanical factors such as the stirring rate and the shape of the reaction vessel. The resting state of the rhodium species under catalytic conditions was found to be [RhCl(dcype)]2, and the proposed intermediates such as RhMe(dcype) and Rh(OBz)(dcype) were readily converted to the most stable state, [RhCl(dcype)]2, via transmetallation with [Al]-Cl species, thus preventing the decomposition of the active catalytic species.
Copper-Promoted Thiolation of C(sp2)–H Bonds Using a 2-Amino Alkylbenzimidazole Directing Group
Liu, Shuang-Liang,Li, Xue-Hong,Shi, Tan-Hao,Yang, Guang-Chao,Wang, Hai-Li,Gong, Jun-Fang,Song, Mao-Ping
, p. 2280 - 2289 (2017)
A copper-promoted thiolation of C(sp2)–H bonds with disulfides was achieved by using 2-amino alkylbenzimidazole (MBIP amine) as a new and removable N,N-bidentate directing group. This strategy gives a variety of functionalized thioethers in moderate to excellent yields in a simple and efficient way. Importantly, the substrate scope is not limited to aromatic amides; diverse alkenyl amides are also compatible. Furthermore, this synthetic approach provides a potentially feasible way to achieve structural modification of related benzimidazole-containing compounds through direct C–H activation.
Copper/Palladium Bimetallic System for the Synthesis of Isobenzofuranones through [4 + 1] Annulation between Propiophenones and Benzoic Acids
Liang, Xiao,Xiong, Mingteng,Zhu, Heping,Shi, Keqiang,Zhou, Yifeng,Pan, Yuanjiang
, p. 9568 - 9573 (2020)
A copper/palladium-catalyzed annulation from benzoic acids and propiophenones for the synthesis of isobenzofuranones was reported. The Cu-(2,2,6,6-tetramethylpiperidin-1-yl)oxyl system showed a great ability to activate the C-H bond on the α- and β-carbons of a carbonyl group, and the in situ-generated enone intermediate in this reaction could be further transformed to construct isobenzofuranones with the catalysis of Pd(dba)2 (dba = dibenzylideneacetone). Various isobenzofuranones could be obtained in moderate to good yields, and a great atom economy was highlighted by utilizing this method.
Two methods for direct ortho-arylation of benzoic acids
Chiong, Hendrich A.,Pham, Quynh-Nhu,Daugulis, Olafs
, p. 9879 - 9884 (2007)
Two new palladium-catalyzed methods for the direct ortho-arylation of free benzoic acids have been developed. The first method employs stoichiometric silver acetate for iodide removal, aryl iodide as the coupling partner, and acetic acid solvent. This method is applicable to the arylation of electron-rich to moderately electron-poor benzoic acids and tolerates chloride and bromide substituents on both coupling partners. The second method involves the use of aryl chloride, cesium carbonate base, n-butyl-di-1-adamantylphosphine ligand, and DMF solvent and is suitable for both electron-rich and electron-poor benzoic acids. Mechanistic studies of the second method point to the heterolytic C-H bond cleavage as the rate-determining step.
Photoinduced FeCl3-Catalyzed Alkyl Aromatics Oxidation toward Degradation of Polystyrene at Room Temperature?
Zhang, Guoxiang,Zhang, Zongnan,Zeng, Rong
supporting information, p. 3225 - 3230 (2021/09/28)
While polystyrene is widely used in daily life as a synthetic plastic, the subsequently selective degradation is still very challenging and highly required. Herein, we disclose a highly practical and selective reaction for the catalytically efficient oxidation of alkyl aromatics (including 1°, 2°, and 3° alkyl aromatics) to carboxylic acids. While dioxygen was used as the sole terminal oxidant, this protocol was catalyzed by the inexpensive and readily available ferric compound (FeCl3) with irradiation of visible light (blue LEDs) under only 1 atmosphere of O2 at room temperature. This system could further facilitate the selective degradation of polystyrene to benzoic acid, providing an important and practical tool to generate high-value chemical from abundant polystyrene wastes.
