Mechanistic Study of the Copper(II)-Mediated Site-Selective O-Arylation of Glycosides with Arylboronic Acids

Abstract

Glycosides having multiple free OH groups have been shown to undergo site-selective O-arylations in the presence of arylboronic acids and copper(II) acetate. Herein, a mechanistic analysis of these Chan–Evans–Lam-type couplings is presented based on reaction kinetics, mass spectrometric analysis of reaction mixtures, and substituent effect studies. The results establish that the formation of a substrate-derived boronic ester accelerates the rate-determining transmetalation step. Intramolecular transfer of the aryl group from the boronic ester is ruled out in favor of a pathway in which the key pre-transmetalation assembly is generated from a boronic ester, a copper complex, and a second equivalent of arylboronic acid.

One–Pot Three–Component Synthesis of 2,4,5–Triaryl Imidazoles using Fe3O4@BisImid−CuBr Nanocomposite as an Ecofriendly and Efficient Magnetically Reusable Catalyst

“…[20] Its affordability, widespread availability, and diverse oxidation states render copper a favored metal for chemists undertaking complex reactions. [21] This confluence of attributes positions copper and its derivatives as stalwarts in the chemist's toolbox, facilitating the realization of diverse and intricate chemical transformations. [22] Heterocyclic compounds in particular nitrogen heterocycles are abundantly seen in the structure of various medicinal compounds for veterinary and herbal medicine.…”

“…Among the pantheon of transition metals, copper stands out as a preferred choice for orchestrating chemical reactions [20] . Its affordability, widespread availability, and diverse oxidation states render copper a favored metal for chemists undertaking complex reactions [21] . This confluence of attributes positions copper and its derivatives as stalwarts in the chemist‘s toolbox, facilitating the realization of diverse and intricate chemical transformations [22] …”