Organoelectrocatalysis Enables Direct Cyclopropanation of Methylene Compounds

Abstract

Cyclopropane is a prevalent structural unit in natural products and bioactive compounds. While the transition metal-catalyzed alkene cyclopropanation of functionalized compounds such as α-diazocarbonyl derivatives has been well established and provides straightforward access to cyclopropanes, cyclopropanation directly from the more stable and simpler methylene compounds has remained an unsolved challenge despite the highly desirable benefits of minimal prefunctionalization and increased operational safety. Herein we report an electrocatalytic strategy for the cyclopropanation of active methylene compounds, employing an organic catalyst. The method shows a broad substrate scope and excellent scalability, requires no metal catalyst or external chemical oxidant, and provides convenient access to several types of cyclopropane-fused heterocyclic and carbocyclic compounds. Mechanistic investigations suggest that the reactions proceed through a radical–polar crossover process to form the two new carbon–carbon bonds in the nascent cyclopropane ring.

Regio- and stereoselective electrochemical selenoalkylation of alkynes with 1,3-dicarbonyl compounds and diselenides

“…To better understand the process of this protocol, we obtained cyclic voltammograms (see the ESI† for details). In view of the above experimental results and previous research progress, 13,14 a possible mechanism for the selenoalkylation of alkynes was proposed (Scheme 5). Dimethyl 2-fluoromalonate 2 reacted with a methanol anion generated by the reduction of methanol at the Pt cathode to form carbanion intermediate 44 .…”

“…However, the selective selenoalkylation of alkynes remains challenging and worth exploring. So herein, we report a sustainable electrochemical three-component approach for the regio- and stereoselective seleno(monofluoro)alkylation of alkynes with 1,3-dicarbonyl compounds as radical precursors 13 and diselenides as radical inhibitors 6,14 to selenated alkenes, which prevents the use of prefunctionalized substrates (Scheme 1b).…”

Electrochemical Site-Selective Alkylation of Azobenzenes with (Thio)Xanthenes

“…In recent years, electrochemical synthesis has received increasing attention for its powerful ability to forge chemical bonds, presumably due to the advantages of no external stoichiometric chemical oxidants or reductants and milder conditions over the conventional approaches [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. As a result, we speculate that electrochemistry maybe provides a unique opportunity to facilitate the functionalization of azobenzene.…”

Intermolecular Metal‐Free Cyclopropanation and Aziridination of Alkenes with XH2(X=N, C) by Thianthrenation**

“…[7] In 2022, Xu developed an electrochemistry enabled intramolecular cyclopropanation of aliphatic alkenes with active methylene compounds. [8] Intermolecular cyclopropanations of alkenes from active methylenes is unsuccessful and remains unknown. Yudin, [9] Little, [10] and Cheng [11] developed electrochemical aziridination of alkenes using N-amino-phthalimide (PhtNH 2 ) and trifluoromethylated sulfamate (HfsNH 2 ) as the source of electrophilic nitrogen source.…”