Copper-Mediated Tandem Oxidative C(sp²)–H/C(sp)–H Alkynylation and Annulation of Arenes with Terminal Alkynes

The copper-mediated tandem oxidative C­(sp²)–H/C­(sp)–H cross-coupling and intramolecular annulation of arenes with terminal alkynes has been developed, which offers a highly efficient approach to the 3-methyleneisoindolin-1-one scaffold. In this oxidative coupling process, Cu­(OAc)₂ acts as both the promoter and the terminal oxidant. This protocol features a wide substrate scope; high functional group tolerance; exclusive chemo-, regio-, and stereoselectivity; and simple, easily available, and inexpensive reaction system. The transformation has demonstrated for the first time that Cu­(OAc)₂ can be renewable after undergoing an oxidative reaction

Copper-Mediated Tandem Oxidative C(sp²)–H/C(sp)–H Alkynylation and Annulation of Arenes with Terminal Alkynes

The copper-mediated tandem oxidative C­(sp²)–H/C­(sp)–H cross-coupling and intramolecular annulation of arenes with terminal alkynes has been developed, which offers a highly efficient approach to the 3-methyleneisoindolin-1-one scaffold. In this oxidative coupling process, Cu­(OAc)₂ acts as both the promoter and the terminal oxidant. This protocol features a wide substrate scope; high functional group tolerance; exclusive chemo-, regio-, and stereoselectivity; and simple, easily available, and inexpensive reaction system. The transformation has demonstrated for the first time that Cu­(OAc)₂ can be renewable after undergoing an oxidative reaction

Cobalt-Catalyzed Cyclization/Hydrosilylation Reaction of 1,6-Diynes Enabled by an Oxidative Cyclization–Hydrosilylation Mechanism

Transition-metal-catalyzed cyclization/hydrosilylation of 1,6-diynes is a useful method for the preparation of five-membered ring-fused silyl dienes that are useful reagents in organic synthesis. Only a handful of noble metal catalysts facilitating this transformation are known, and nonprecious metal catalysts effecting the reaction have remained elusive. Herein, we report that low-coordinate Co(0)-N-heterocyclic carbene complexes can catalyze the cyclization/hydrosilylation of 1,6-diynes with tertiary and secondary hydrosilanes, furnishing five-membered ring-fused (Z)-1-silyldienes in good yields and excellent stereoselectivity. Mechanistic study disclosed that the catalytic cycle likely has oxidative cyclization of 1,6-diynes with Co(0) species as the key step. This mechanism accounts for the high stereoselectivity and absence of uncyclized hydrosilylation byproducts in the cobalt-catalyzed cyclization/hydrosilylation reaction, which is different from the hydrosilylation-cyclization mechanism of the noble metal-catalyzed reactions

Cobalt-Catalyzed Cyclization/Hydrosilylation Reaction of 1,6-Diynes Enabled by an Oxidative Cyclization–Hydrosilylation Mechanism

Transition-metal-catalyzed cyclization/hydrosilylation of 1,6-diynes is a useful method for the preparation of five-membered ring-fused silyl dienes that are useful reagents in organic synthesis. Only a handful of noble metal catalysts facilitating this transformation are known, and nonprecious metal catalysts effecting the reaction have remained elusive. Herein, we report that low-coordinate Co(0)-N-heterocyclic carbene complexes can catalyze the cyclization/hydrosilylation of 1,6-diynes with tertiary and secondary hydrosilanes, furnishing five-membered ring-fused (Z)-1-silyldienes in good yields and excellent stereoselectivity. Mechanistic study disclosed that the catalytic cycle likely has oxidative cyclization of 1,6-diynes with Co(0) species as the key step. This mechanism accounts for the high stereoselectivity and absence of uncyclized hydrosilylation byproducts in the cobalt-catalyzed cyclization/hydrosilylation reaction, which is different from the hydrosilylation-cyclization mechanism of the noble metal-catalyzed reactions

Copper(II)-Catalyzed Dehydrogenative Cross-Coupling between Two Azoles

The copper­(II)-catalyzed dehydrogenative coupling between two different azoles for the preparation of unsymmetrical biazoles has been developed. The current catalytic system can effectively control the chemoselectivity for heterocoupling over homocoupling