A Palladium-Free Sonogashira Coupling Protocol Employing an In Situ Prepared Copper/Chelating 1,2,3-Triazolylidene System

Abstract

A new, palladium-free Sonogashira coupling reaction protocol using a catalytic system that comprises a simple, cheap, widely available copper salt and a chelating 1,2,3-triazolylidene ligand precursor is reported. This protocol provides the desired coupling products in moderate to very good yields.

An In‐Situ‐Formed Copper‐Based Perfluorinated Catalytic System for the Aerobic Oxidation of Alcohols

“…The influence of the organic solvent and the temperature on the reaction outcome was also studied. The reaction proceeds more efficiently in aromatic solvents, such as benzene, chlorobenzene, dichlorobenzene, anisole, cumene, and p-cymene (entries [15][16][17][18][19][20][21][22], than in polar, aprotic solvents such as DMAc or diglyme (entries 23 and 24). Actually, anisole, which is a non-toxic solvent, provides the optimum reaction conditions (entry 21), making our protocol more user-friendly and less dangerous to the environment, compared to others in the literature extensively using chlorobenzene, a quite toxic and hazardous solvent.…”

“…In the framework of our interest in sustainable catalysis, [20][21][22][23][24][25] and considering the lack of a thorough study on the catalytic activity of a simple, in situ prepared NHC/Cu-based biphasic catalytic system in alcohols oxidation, we herein report the development of such a straightforward, user-friendly protocol for the oxidation of primary and secondary alcohols. Our catalytic protocol is based on an in situ generated catalytic system consisting of copper (I) oxide, easily accessible NHCs bearing perfluorinated ponytails, as ligands, TEMPO as additive, and oxygen as the oxidant of the reaction.…”

Traceless Directing Groups in Sustainable Metal-Catalyzed C–H Activation

“…Higher yields are also observed when using Et 3 N and 1,4-dioxane at 130 • C for prolonged reaction time, even though 50% conversion was achieved after 1 h. Under the optimized conditions, structurally diverse naphthylamides were tested and it was observed that a naphthylamide with a methyl group at the C2 position led to only traces of the product, implying that steric hinderance has a detrimental effect (116). On the other hand, when the C4 position of the naphthylamide is substituted, the isolated yields are moderate to high for substrates bearing substituents that are electron-donating (117) or electron-withdrawing (118), phenyl groups bearing either electron-withdrawing or -donating moieties (119)(120)(121), naphthyl groups (122), five-membered aromatic rings (123), and a synthetically valuable alkyne unit (124). For compounds having more conjugated systems (125,126), yields are also moderate to high and, significantly, the conditions could be employed for substrates bearing either a quinoline or an isoquinoline unit (127).…”

“…Copper-catalyzed transformations involving C-H activation [119,120] are lately increasing, underlining the growing interest in expanding the gamut of earth-abundant metals used in contemporary synthetic challenges. Recent publications [121,122] dealing with the most common formal oxidation states reached by copper, namely Cu(I), Cu(II), and Cu(III), indicate the ongoing investigation of the role of copper in fundamental properties of various compounds that appear as well-defined catalysts or catalytic intermediates during Cu-catalysis.…”