Selective Cross-Dehydrogenative Coupling of Various Acyclic Enamides with Heteroarenes via Rh(III)-Catalyzed C-H Activation

Cobalt-Catalyzed Regio- and Stereoselective C(sp2)-H Alkylation of Enamides with 4-Alkyl-1,4-dihydropyridines

We report herein an efficient cobalt-catalyzed regioselective and stereoselective alkenyl C(sp2)-H alkylation of structurally diverse enamides with 4-alkyl-1,4-dihydropyridines (DHPs) as the alkyl radical precursors. This DHPs-based approach features a broad substrate scope and excellent compatibility with diverse functionalities, giving rise to geometrically defined β-alkylated enamides with an exclusive E configuration. Preliminary mechanistic studies suggest a radical-involved pathway.

An electron donor-acceptor complex-initiated C-H trifluoromethylation and perfluoroalkylation of enamides and quinoxalinones

Facilitated by an electron donor-acceptor (EDA) complex, an efficient β-trifluoromethylation and perfluoroalkylation of enamides with Togni reagent or perfluoroalkyl iodides is presented under transition-metal-free, photocatalyst-free and mild reaction conditions. Notably, using this photocatalyst-free strategy, direct trifluoromethylation and perfluoroalkylation of quinoxalin-2(1H)-one derivatives was also achieved via a photoactive electron donor-acceptor complex.

Rhodium(III)-Catalyzed Switchable β-C(sp2)-H Alkenylation and Alkylation of Acyclic Enamides with Allyl Alcohols

Herein, rhodium(III)-catalyzed β-C(sp2)-H alkenylation and alkylation of enamides are presented using readily accessible allylic alcohols by switching the reaction conditions. This tunable transformation has been applied to a wide range of substrates and typically proceeded with excellent regioselectivity and stereoselectivity as well as with good functional group tolerance. The catalytic system offers an efficient approach for synthesizing various functionalized enamides bearing N-(2Z,4E)-butadiene and (Z)-β-C(sp2)-H alkylated enamides. In addition, mechanistic experiments suggest that Rh(III)-catalyzed C-H activation is not related to the critical step.

Synthesis of Benzoselenophenes via TMSCN-Enabled Radical-Mediated Tandem Reaction Involving Enamides and Elemental Selenium

This study presents a TMSCN-enabled tandem reaction involving enamides and elemental selenium to access a diverse array of benzoselenophenes. Notably, this methodology involves the direct 2-fold C(sp2)-H bond activation without the need for preinstalled halides or boronic acids as reaction handles. The protocol offers several noteworthy features, including the absence of transition metals and strong oxidants, high reaction efficiency, broad substrate scopes, and the use of stable elemental selenium as a selenium source.