COA of Formula: C14H21BO3On June 12, 2017, Zhu, Lei; Qi, Xiaotian; Li, Yingzi; Duan, Meng; Zou, Lufeng; Bai, Ruopeng; Lan, Yu published an article in Organometallics. The article was 《Ir(III)/Ir(V) or Ir(I)/Ir(III) Catalytic Cycle? Steric-Effect-Controlled Mechanism for the para-C-H Borylation of Arenes》. The article mentions the following:
A potential energy surface for iridium-catalyzed C-H-borylation of aromatic compounds was calculated; while bulky phosphine ligands favor Ir(I)-Ir(III) C-H activation, small amine ligands promote formation of triboryl Ir(V) intermediates. D. functional theory method N12 was used to study the mechanism of the [Ir(cod)OH]2/Xyl-MeO-BIPHEP-catalyzed para-selective C-H borylation reaction. The results revealed that the use of a bulky diphosphine ligand such as Xyl-MeO-BIPHEP was unfavorable for the previously proposed iridium(III)/iridium(V) catalytic cycle because it resulted in considerable steric repulsion in the hepta-coordinated iridium(V) intermediate. Inspired by this steric effect, we have proposed a novel iridium(I)/iridium(III)-based catalytic cycle for this transformation and shown that it can be used to account for the exptl. results. The iridium(I)/iridium(III) catalytic cycle induced by this steric effect consists of several steps, including: (i) the oxidative addition of the C-H bond of the substrate to an active iridium(I) boryl complex; (ii) the reductive elimination of a C-B bond; (iii) the oxidative addition of B2pin2 to an iridium(I) hydride complex; and (iv) the reductive elimination of a B-H bond. Notably, the computed regioselectivity of this reaction was consistent with the exptl. observations. The high para-selectivity of this reaction was also explained using structural anal. and a 2D contour model, which revealed that the strong steric repulsion between the diphosphine ligand and the meta-substituents resulted in a higher energy barrier for meta-C-H activation. The experimental process involved the reaction of 2-(4-Methoxy-3-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(cas: 214360-63-1COA of Formula: C14H21BO3)
2-(4-Methoxy-3-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane(cas: 214360-63-1) belongs to ethers.Oxygen is more electronegative than carbon, thus the alpha hydrogens of ethers are more acidic than those of simple hydrocarbons. They are far less acidic than alpha hydrogens of carbonyl groups (such as in ketones or aldehydes), however. COA of Formula: C14H21BO3
Referemce:
Ether – Wikipedia,
Ether | (C2H5)2O – PubChem