Direct Observation of the Oxidative Addition of the Aryl Carbon−Oxygen Bond to a Ruthenium Complex and Consideration of the Relative Reactivity between Aryl Carbon−Oxygen and Aryl Carbon−Hydrogen Bonds

Abstract

When RuH2(CO)(PPh3)3 was reacted with 2,2-dimethyl-1-(2-p-tolylphenyl)propan-1-one (2), the ruthenium-aryloxy complex 3 was obtained in 76% yield. The structure of this complex was determined from 1H and 31P NMR and X-ray data. Complex 3 showed the catalytic activity for the coupling of 2 with the phenylboronate 4. The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but the C-O bond cleavage is a thermodynamic one. The reaction of 2'-methoxyacetophenone with vinylsilane and organoboronate resulted in chemoselective C-C bond formation.

Metal-catalyzed activation of ethers via C–O bond cleavage: a new strategy for molecular diversity

“…32 Subsequently, Kakiuchi and Chatani shed light into the mechanism highlighted in Scheme 16 by the successful isolation of the oxidative addition complex of an aryl C-O bond using lowvalent ruthenium complexes and ketones as directing groups at the ortho position (Scheme 17, bottom right). 33 Interestingly, no Ru(II) metallacycle derived from the functionalization of ortho C-H bonds could be detected in the crude reaction mixtures. Careful monitoring of a stoichiometric reaction revealed a rather surprising finding regarding the relative reactivity of proximal C-H and C-O bonds.…”

“…31,33 In 2008, Chatani and Tobisu overcame such limitation by designing an elegant Ni-catalyzed SuzukiMiyaura coupling reaction of aryl methyl ethers with organoboron reagents (Scheme 18). 34 Practicality and novelty aside, such a method offered new vistas for the utilization of aryl methyl ethers in cross-coupling reactions, a field that has largely been dominated by the employment of highly reactive and air-sensitive Grignard reagents.…”

Chemoselectivity and the Curious Reactivity Preferences of Functional Groups

“…Although direct arylation of ArÀH or even ArÀOR substrates has received a great deal of attention in recent years, [144] the arylation of Ar À OH has not. [145] In 2008, Kang and co-workers reported that the bromophosphonium salt PyBroP can be employed as an in situ activating agent to allow the direct arylation of tautomerizable heterocycles by Suzuki-Miyaura coupling.…”

Ethereal C–O Bond Cleavage Mediated by Ni(0)-Ate Complex: A DFT Study

“…However, this breakthrough was overlooked for decades, until quite recently. After the development of improved conditions, ArOR can now be used as a coupling partner in several types of transition metal (TM)-catalyzed cross-couplings and related transformations, such as Suzuki-Miyaura-type (B), [24][25][26][27][28][29][30][31] Negishi-type (Zn or Al), [32][33][34][35][36] Murahashi-type (Li), [37][38][39][40] and other reactions. [41][42][43][44][45][46][47][48][49][50] As a continuation of our work in this area, we reported in 2012 the first ethereal Negishi-type coupling of aryl alkyl ether 36) (Chart 1(1)) and in 2016 we reported a systematic examination of ethereal Murahashi-type reaction 37) (Chart 1(2)).…”