An efficient catalytic system for Sonogashira-Hagihara-type reactions displaying ligand acceleration in the copper-catalyzed formation of C(sp²)-C(sp) bonds is described. The structure of the ligand plays a key role for the coupling efficiency. Various copper sources show excellent catalytic activity, even in sub-mol% quantities. A wide variety of substituents is tolerated in the substrates. Mechanistic details have been revealed by kinetic measurements and DFT calculations.

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A convenient transition metal-free procedure for the direct thiolation of 1,3,4-oxadiazole C-H bonds using diaryl disulfides has been developed. Other substrates including indole, benzothiazole, N-phenylbenzimidazole, and caffeine were also thiolated in this manner, providing the corresponding products in good to excellent yields.

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An oxidative cross-coupling reaction between aldehydes and sulfoximines involving dual C À H/N À H functionalization has been developed. This reaction process is facilitated by a simple copper catalyst (1 mol% loading) and tert-butyl hydroperoxide (TBHP) as the oxidant and proceeds under mild reaction conditions to afford a series of valuable N-acylated sulfoximine derivatives in excellent yields.

A method to access α‐thioaryl ketones and α‐thioaryl esters employing copper acetate (hydrate) as catalyst and readily accessible diaryl disulfides and β‐diketones (or β‐keto esters) has been developed. Both alkyl‐ and aryl‐substituted carbonyl compounds can be prepared.magnified image

An efficientc obalt(III)-catalyzed C-2-selective indole C-Hh ydroarylation of acrolein, enones,a nd glyoxylates was achieved under mild reaction conditions.T he versatilec obalt(III) catalyst displayed excellent positional selectivity with the assistance of pyrimidinyl, pyridyl, andp yrazolyl directing groups,t hus overcoming the inherent C-3 selectivity of an electrophilic indole derivatization. This approachp rovides an expedient route to indolyl-substituteda ldehydes,k etones,a nd estersw ith wide functional group tolerance.I naddition, it also features high step-and atom-economy.

Developing methods for the direct functionalization of quinones for assembly of highly functionalized quinones or bioactive natural products is an essential topic in the field of direct C–H functionalization. Quinone units are key motifs in many bioactive compounds and materials, and many innovative methods have been elaborated for the generation of these units. A major part of the established synthetic strategies combines installation of substituents on hydroquinones, phenols, or phenyl ethers through different coupling reactions with oxidation to produce the desired quinones. Most of these above‐mentioned methods introduce multiple chemical steps; however, the synthesis of quinoid compounds through the direct C–H functionalization of simple quinones remains challenging. This minireview summarizes the recently developed achievements for assembly of functionalized quinones through direct functionalization of simple quinones. Our focus will be on the methods and mechanism of these reactions that have appeared in the last two decades.