Ruthenium(II)-Catalyzed Regioselective 1,2-Hydrosilylation of N-Heteroarenes and Tetrel Bonding Mechanism was written by Behera, Deepak;Thiyagarajan, Subramanian;Anjalikrishna, Puthannur K.;Suresh, Cherumuttathu H.;Gunanathan, Chidambaram. And the article was included in ACS Catalysis in 2021.Category: quinoxaline This article mentions the following:
An efficient regioselective dearomatization of N-heteroarenes using a ruthenium precatalyst [Ru-(p-cymene)(PCy3)Cl2] 1 is achieved. Reactions were performed under mild and neat conditions. A wide variety of N-heteroarenes undergo the addition of silanes in the presence of precatalyst 1, leading to exclusive N-silyl-1,2-dihydroheteroarene products. This catalytic method displays a broad substrate scope; quinolines, isoquinolines, benzimidazoles, quinoxalines, pyrazines, pyrimidines, and pyridines undergo highly selective 1,2-dearomatization. Both electron-donating and electron-withdrawing substituents on N-heteroaromatics are well tolerated in this protocol. Mechanistic studies indicate the presence of [Ru-(p-cymene) (PCy3)HCl] 4 in the reaction mixture, which may be the resting state of the catalyst. The complete catalytic cycle as revealed from d. functional theory (DFT) studies show that the product formation is governed by N → Si tetrel bonding. Initially, PCy3 dissociates from 1, and further reaction of [(p-cymene)RuCl2] 20 with silane generates the catalytically active intermediate [(p-cymene)RuHCl] 7. Heteroarene coordinates with 7, and subsequent dearomative 1,3-hydride transfer to the C2 position of the heteroaryl ligand generates an amide-ligated intermediate in which the reaction of silane occurs through a tetrel bonding and provides a selective pathway for 1,2-addition DFT studies also revealed that ruthenium-catalyzed 1,4-hydroboration of pyridines is a facile process with a free energy barrier of 3.2 kcal/mol, whereas a pathway for the 1,2-hydroboration product is not observed due to the steric effects exerted by Me groups on pinacolborane (HBpin) and p-cymene. Notably, enabled by the amine-amide inter-conversion of the coordinated heteroarene ligand, the +2 oxidation state of ruthenium intermediates remains unchanged throughout the catalytic cycle. In the experiment, the researchers used many compounds, for example, 6-Chloroquinoxaline (cas: 5448-43-1Category: quinoxaline).
6-Chloroquinoxaline (cas: 5448-43-1) belongs to quinoxaline derivatives. Quinoxaline derivatives are important constituents of pharmacologically active compounds, including antibacterial, antibiotic and antineoplastic, antifungal, anti-inflammatory and analgesic drugs. Quinoxaline-1,4-di-N-oxide derivatives have shown to improve the biological results and are endowed with anti-viral, anti-cancer, anti-bacterial, and anti-protozoal activities with application in many other therapeutic areas.Category: quinoxaline
Referemce:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider