26216-91-1Relevant academic research and scientific papers
Mononuclear complexes of a tridentate redox-active ligand with sulfonamido groups: Structure, properties, and reactivity
Cook, Sarah A.,Bogart, Justin A.,Levi, Noam,Weitz, Andrew C.,Moore, Curtis,Rheingold, Arnold L.,Ziller, Joseph W.,Hendrich, Michael P.,Borovik
, p. 6540 - 6547 (2018)
The design of molecular complexes of earth-abundant first-row transition metals that can catalyze multi-electron C-H bond activation processes is of interest for achieving efficient, low-cost syntheses of target molecules. To overcome the propensity of these metals to perform single-electron processes, redox-active ligands have been utilized to provide additional electron equivalents. Herein, we report the synthesis of a novel redox active ligand, [ibaps]3-, which binds to transition metals such as FeII and CoII in a meridional fashion through the three anionic nitrogen atoms and provides additional coordination sites for other ligands. In this study, the neutral bidentate ligand 2,2′-bipyridine (bpy) was used to complete the coordination spheres of the metal ions and form NEt4[MII(ibaps)bpy] (M = Fe (1) or Co (1-Co)) salts. The FeII salt exhibited rich electrochemical properties and could be chemically oxidized by 1 and 2 equiv. of ferrocenium to form singly and doubly oxidized species, respectively. The reactivity of 1 towards intramolecular C-H bond amination of aryl azides at benzylic and aliphatic carbon centers was explored, and moderate to good yields of the resulting indoline products were obtained.
Chemoenzymatic preparation of optically active secondary amines: a new efficient route to enantiomerically pure indolines
Gotor-Fernandez, Vicente,Fernandez-Torres, Pedro,Gotor, Vicente
, p. 2558 - 2564 (2006)
An efficient chemoenzymatic route for the synthesis of optically active substituted indolines has been developed. Different lipases have been tested in the alkoxycarbonylation of these secondary amines, Candida antarctica lipase A (CAL-A) was found to be the best biocatalyst for 2-substituted-indolines, and C. antarctica lipase B (CAL-B) for 3-methylindoline. The combination of lipases with a variety of allyl carbonates and tert-butyl methyl ether (TBME) as solvent has allowed the isolation of the carbamate and amine derivatives with a high level of enantiopurity.
Palladium-Catalyzed Direct and Specific C-7 Acylation of Indolines with 1,2-Diketones
Xie, Guilin,Zhao, Yuhan,Cai, Changqun,Deng, Guo-Jun,Gong, Hang
supporting information, p. 410 - 415 (2021/01/26)
The indole scaffold is a ubiquitous and useful substructure, and extensive investigations have been conducted to construct the indole framework and/or realize indole modification. Nevertheless, the direct selective functionalization on the benzenoid core must overcome the high activity of the C-3 position and still remains highly challenging. Herein, a palladium-catalyzed direct and specific C-7 acylation of indolines in the presence of an easily removed directing group was developed. This strategy usually is considered as a practical strategy for the preparation of acylated indoles because indoline can be easily converted to indole under oxidation conditions. In particular, our strategy greatly improved the alkacylation yield of indolines for which only an unsatisfactory yield could be achieved in the previous studies. Furthermore, the reaction can be scaled up to gram level in the standard reaction conditions with a much lower palladium loading (1 mol %).
Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
supporting information, p. 7738 - 7744 (2021/05/07)
Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
Chiral Br?nsted Acid from Chiral Phosphoric Acid Boron Complex and Water: Asymmetric Reduction of Indoles
Yang, Kai,Lou, Yixian,Wang, Chenglan,Qi, Liang-Wen,Fang, Tongchang,Zhang, Feng,Xu, Hetao,Zhou, Lu,Li, Wangyang,Zhang, Guan,Yu, Peiyuan,Song, Qiuling
supporting information, p. 3294 - 3299 (2020/01/21)
A new chiral Br?nsted acid, generated in situ from a chiral phosphoric acid boron (CPAB) complex and water, was successfully applied to asymmetric indole reduction. This “designer acid catalyst”, which is more acidic than TsOH as suggested by DFT calculations, allows the unprecedented direct asymmetric reduction of C2-aryl-substituted N-unprotected indoles and features good to excellent enantioselectivities with broad functional group tolerance. DFT calculations and mechanistic experiments indicates that this reaction undergoes C3-protonation and hydride-transfer processes. Besides, bulky C2-alkyl-substituted N-unprotected indoles are also suitable for this system.
Asymmetric Transfer Hydrogenation of N-Unprotected Indoles with Ammonia Borane
Zhao, Weiwei,Zhang, Zijia,Feng, Xiangqing,Yang, Jing,Du, Haifeng
supporting information, p. 5850 - 5854 (2020/08/05)
A metal-free asymmetric transfer hydrogenation of unprotected indoles was successfully realized using a catalyst derived from HB(C6F5)2 and (S)-tert-butylsulfinamide with ammonia borane as a hydrogen source. A variety of indolines were achieved in 40-78percent yields with up to 90percent ee.
B(C6F5)3-Promoted hydrogenations of N-heterocycles with ammonia borane
Ding, Fangwei,Zhang, Yiliang,Zhao, Rong,Jiang, Yanqiu,Bao, Robert Li-Yuan,Lin, Kaifeng,Shi, Lei
supporting information, p. 9262 - 9264 (2017/08/21)
A transition-metal-free method for the B(C6F5)3-promoted hydrogenations of N-heterocycles using ammonia borane under mild reaction conditions has been developed. The reaction affords a broad range of hydrogenated products in moderate to good yields. The enantioselective versions for the corresponding products were also investigated via our approach, showing good feasibility.
Kinetic resolution of indolines through reductive amination of aldehydes by chiral Br?nsted acid
Wang, Yingwei,Li, Guangxun,Liu, Hongxin,Tang, Zhuo,Cao, Yuan,Zhao, Gang
supporting information, p. 2993 - 2996 (2017/07/07)
We have developed a highly efficient and practical strategy for the kinetic resolution of indoline derivatives, involving a chiral Br?nsted acid-catalyzed iminium ion formation and asymmetric transfer hydrogenation cascade process. The kinetic resolution allows the synthesis of 2-substituted N-benzylindolines in good yields with moderate to excellent enantioselectivities.
Using weak interactions to control C-H mono-nitration of indolines
Bose, Anima,Mal, Prasenjit
supporting information, p. 11368 - 11371 (2017/10/19)
An unprecedented C-H mononitration of indolines either at the -C5 or -C7 positions under mild condition is reported here. The roles of multiple weak interactions and factors such as steric factors, electronic effects, cation-π interactions, and solvent polarity were established, and we achieved a 100% regioselective electrophilic aromatic (EArS) nitration using Cu(NO3)2 or AgNO3.
Structure-activity relationships and docking studies of synthetic 2-arylindole derivatives determined with aromatase and quinone reductase 1
Prior, Allan M.,Yu, Xufen,Park, Eun-Jung,Kondratyuk, Tamara P.,Lin, Yan,Pezzuto, John M.,Sun, Dianqing
, p. 5393 - 5399 (2017/11/20)
In our ongoing effort of discovering anticancer and chemopreventive agents, a series of 2-arylindole derivatives were synthesized and evaluated toward aromatase and quinone reductase 1 (QR1). Biological evaluation revealed that several compounds (e.g., 2d, IC50 = 1.61 μM; 21, IC50 = 3.05 μM; and 27, IC50 = 3.34 μM) showed aromatase inhibitory activity with half maximal inhibitory concentration (IC50) values in the low micromolar concentrations. With regard to the QR1 induction activity, 11 exhibited the highest QR1 induction ratio (IR) with a low concentration to double activity (CD) value (IR = 8.34, CD = 2.75 μM), while 7 showed the most potent CD value of 1.12 μM. A dual acting compound 24 showed aromatase inhibition (IC50 = 9.00 μM) as well as QR1 induction (CD = 5.76 μM) activities. Computational docking studies using CDOCKER (Discovery Studio 3.5) provided insight in regard to the potential binding modes of 2-arylindoles within the aromatase active site. Predominantly, the 2-arylindoles preferred binding with the 2-aryl group toward a small hydrophobic pocket within the active site. The C-5 electron withdrawing group on indole was predicted to have an important role and formed a hydrogen bond with Ser478 (OH). Alternatively, meta-pyridyl analogs may orient with the pyridyl 3′-nitrogen coordinating with the heme group.
