Directed meta‐Selective Bromination of Arenes with Ruthenium Catalysts

Abstract

A Ru-catalyzed direct CH activation/meta-bromination of arenes bearing pyridyl, pyrimidyl, and pyrazolyl directing groups has been developed. A series of bromo aryl pyridines and pyrimidines have been synthesized, and further coupling reactions have also been demonstrated for a number of representative functionalized arenes. Preliminary mechanistic studies have revealed that this reaction may proceed through radical-mediated bromination when NBS is utilized as the bromine source. This type of transformation has opened up a new direction for the radical non-ipso functionalization of metal with regard to future CH activation development that would allow the remote functionalization of aromatic systems.

Arene‐Ligand‐Free Ruthenium(II/III) Manifold for meta‐C−H Alkylation: Remote Purine Diversification

“…[1, 2] In sharp contrast, remote CÀHf unctionalizations continue to be scarce, [3] with notable recent progress through carboxylate-assisted [4] ruthenium [5] catalysis by Frost, [6] Huang, [7] Greaney, [8] Zhang, [9] and Ackermann, [10] among others. Thus, the arene-ligand-free complex [Ru(OAc) 2 (PPh 3 ) 2 ]e nabled remote CÀHf unctionalizations with ample scope and excellent levelso fc hemo-and positionals electivities.…”

“…[1] The control of positional selectivity is of prime importance for the development of synthetically useful transformations. [1,2] In sharp contrast, remote CÀHf unctionalizations continue to be scarce, [3] with notable recent progress through carboxylate-assisted [4] ruthenium [5] catalysis by Frost, [6] Huang, [7] Greaney, [8] Zhang, [9] and Ackermann, [10] among others. [1,2] In sharp contrast, remote CÀHf unctionalizations continue to be scarce, [3] with notable recent progress through carboxylate-assisted [4] ruthenium [5] catalysis by Frost, [6] Huang, [7] Greaney, [8] Zhang, [9] and Ackermann, [10] among others.…”

In Situ Formed IIII‐Based Reagent for the Electrophilic ortho‐Chlorination of Phenols and Phenol Ethers: The Use of PIFA‐AlCl3 System

“…51-53°C. 13 C NMR (126 MHz, CDCl 3 ): δ = 121.7, 125.5, 128.2, 147.0 ppm. 1 H NMR (500 MHz, CDCl 3 ): δ = 7.08 (dd, J = 7.9, 2.9 Hz, 1 H), 6.97 (dd, J = 9.0, 5.1 Hz, 1 H), 6.91 (ddd, J = 9.0, 7.9, 2.9 Hz, 1 H) ppm.…”

“…An efficient electrophilic chlorination for these electron-rich arenes as well as the scope of the reaction are described herein. However, due to the relative low electrophilicity at the chlorine atom, a reagent activation with Lewis bases (Ph 3 PS), [10] strong Brønsted acids (TfOH), [11] metallic Lewis acids [ZrCl 4 , [12] Ru III , [13] Pd(OAc) 2 , [14] PdCl 2 or CuCl 2 , [15] CuX 2 /Pd(OAc) 2 [16] ], nonmetallic Lewis acids (TMS-Communication Scheme 1. 485 group in organic synthesis.…”

“…. IR (KBr): ppm 13. 1,8-Dichloro-7-methoxynaphthalen-2-ol (4): The following compound was obtained according to the general procedure for chlorination by using 7-methoxy-2-napthol in 42 % yield as a dark red solid.…”