Half‐Sandwich (η⁶‐Benzene)Ruthenium(II) Complex of Picolyl Functionalized N‐Heterocyclic Carbene as an Efficient Catalyst for Thioether Directed C−H Alkenylation of Arenes

Abstract

In this report, a half-sandwich (η 6 -benzene)Ru(II) complex of picolyl functionalized N-heterocyclic carbene was synthesized and efficiently used for the alkenylation arenes through thioether directed CÀ H bond activation. The thioether functionality of the substrate directed a selective ortho-vinylation through CÀ H bond activation. Moreover, reaction significantly works under mild reaction conditions than the previously reported ones which use the precious noble metal catalyst including the Pd(II), Rh(III), and Ir(III). Broad substrate scope using several benzyl thioethers and vinyl were found to be well tolerated for the present catalytic reaction to produces moderate to good yields of the desired products. Moreover, it is the first report where a Ru-based catalyst was used for the alkenylation of thioethers.

Selenium-Directed Ortho C–H Activation of Benzyl Selenide by a Selenated NHC–Half-Pincer Ruthenium(II) Complex

“…The synthesis methodology for the Ru­(II) catalyst is shown in Scheme . An earlier known procedure was employed for the synthesis of 1-(2-chloroethyl)-1 H -benzimidazole (a), , and a slightly modified procedure directed us to 1-(2-(phenylselane)­ethyl)-1 H -benzimidazole (b). , Further, a reaction of 1-(2-(phenylselane)­ethyl)-1 H -benzimidazole and 2-bromomethyl pyridine resulted in N -(1-selanophenyl-2-ethyl)- N ″-(pyridine-2-ylmethyl) benzimidazolium bromide (c), which is our desired ligand for the complexation. Finally, a silver carbene transfer reaction of ligand c with Ag 2 O in CH 2 Cl 2 under a N 2 atmosphere at room temperature and in the dark, followed by the addition of a methanol suspension of [η 6 (C 6 H 6 )­RuCl­(μ-Cl)] 2 to the resulting solution of silver complex produces complex 1 .…”

“…The synthesis methodology for the Ru(II) catalyst is shown in Scheme 2. An earlier known procedure was employed for the synthesis of 1-(2-chloroethyl)-1H-benzimidazole (a), 30,31 and a slightly modified procedure directed us to 1-(2-(phenylselane)ethyl)-1H-benzimidazole (b). 30,31 Further, a reaction of 1-(2-(phenylselane)ethyl)-1H-benzimidazole and 2-bromomethyl pyridine resulted in N-(1-selanophenyl-2ethyl)-N″-(pyridine-2-ylmethyl) benzimidazolium bromide (c), which is our desired ligand for the complexation.…”

Mechanistic insights and comparative analysis of Ru(ii)–NNC pincer complexes with anionic-, protic-, and classical-NHCs for transfer hydrogenation of ketones

“…[1][2][3][4][5] Their strong σ-donor properties and ease of stereo-electronic modification at nitrogen substituent and carbon backbones of the heterocyclic skeleton have been utilized in the development of complexes with interesting properties and excellent catalytic activities. [6][7][8][9][10][11] A new subclass of NHCs, called protic-NHCs (pNHCs), which bears at least one NH functional group in the N-heterocyclic ring, has become popular in recent years with contributions from Hahn, Ikariya, Kuwata, and several other groups. [12][13][14][15][16][17][18][19][20] The pNHCs have attracted significant attention over the classical NHCs due to the existence of a proton-responsive NH group, allowing H-bonding interactions, β-deprotonations, and nucleophilic additions.…”

Ru-Catalyzed and Selenium-Directed Selective Formation of ortho- and Dialkenylated Selanes, Mixed Organoselenoethers, and Isoselenochromenes

“…5 However, chalcogen atoms have great potential to act as directing groups; moreover, these atoms also provide an inherent stability to the molecules. 6 Among the chalcogens, selenium has great potential to act as an efficient directing group without poisoning metal catalysts. 7 In 2020, Tang et al revealed the first instance of Se-directed C−H bond borylation of arene.…”