Rapid Access to Triarylmethanes (TRAMs) Enabled by Direct Electrolysis of Indolizines with Carbonyls.

A fast, scalable, transition metal-free, electrochemical sp2 geminal functionalization of carbonyls enabled by anodic oxidation of non-prefunctionalized chromone-fused indolizines to access the triarylmethanes (TRAMs) is disclosed for the first time. This momentary electrochemical approach features the use of readily available carbonyls, implantation of the C(sp3) center (well-known for dramatically improving biological active potency), a broad substrate scope, and excellent yields of TRAMs with fluorescence properties.

Electrochemical selective divergent C-H chalcogenocyanation of N-heterocyclic scaffolds.

An electrochemical direct selective C-H chalcogenocyanation approach for indolizine derivatives under mild conditions has been described. Cyclic enone-fused, chromone-fused and 2-substituted indolizines possessing EDGs (electron donating groups) and EWGs (electron withdrawing groups) were successfully reacted with NH4SCN and KSeCN under electrochemical conditions to provide a wide array of mono and bis-chalcogenocyanate-indolizines in 75-94% yields. In addition, 1-substituted imidazo[1,5-a]quinolines were also successfully chalcogenocyanated under the optimized reaction conditions providing a platform for the synthesis of pharmaceutically privileged molecules. By switching the reaction conditions, the developed protocol offers selective synthesis of C-3 thiocyanate and 1,3 bis-thiocyanate indolizines in good to excellent yields under catalyst-free conditions. On the basis of control experiments and cyclic voltammetry data, a plausible reaction pathway is also presented.

Electrochemical, Regioselective, and Stereoselective Synthesis of Allylic Thioethers and Selenoethers under Transition-Metal-Free and Oxidant-Free Conditions.

We disclose a mild, scalable, electricity-promoted cross coupling protocol between allylic iodides and disulfides/diselenides for the formation of C-S/Se bonds in the absence of transition metals, bases, and oxidants. The stereochemically different densely functionalized allylic iodides gave regio- and stereoselective diverse thioethers in good yields. This strategy demonstrates a sustainable promising approach for the synthesis of allylic thioethers in 38-80% yields. This protocol also provides a synthetic platform for the synthesis of allylic selenoethers. A single-electron transfer radical pathway was also validated with radical scavenger experiments and cyclic voltammetry data.

Electrochemical direct C-H mono and bis-chalcogenation of indolizine frameworks under oxidant-free conditions.

Herein, we disclosed a sustainable electrochemical approach for site-selective C-H mono and bis-chalcogenation (sulfenylation or selenylation) of indolizine frameworks. Diversely functionalized disulfides and diselenides possessing EDGs and EWGs were successfully reacted with a variety of indolizines to directly access sulfenylated/selenylated indolizines in 40-96% yields. A mechanistic radical pathway was also validated with control experiments and cyclic voltammogram data.

Electrochemical Bisarylation of Carbonyls: A Direct Synthetic Strategy for Bis(indolyl)methane.

An interesting electrochemical direct bisarylation of carbonyls with indole derivatives to afford the corresponding bis(indolyl)methane (BIM) derivatives is described. The developed protocol is suitable for aliphatic, aromatic, and heteroaromatic aldehydes, which react with various electron-rich and electron-poor indoles to afford the corresponding BIMs in good to excellent yields. Isatin derivatives also underwent bisarylation with various indole derivatives under the influence of current to afford the corresponding BIMs in excellent yields.

Electrochemical site-selective direct C-H sulfenylation and selenylation of a chromone-fused-indolizine (CFI) skeleton.

Herein, for the first time, we report the transition metal-free electrochemical site-selective direct C-H sulfenylation/selenylation of chromone-fused indolizine compounds (CFIs) to afford the corresponding CFIs thioethers and selenoethers   in 58-96% yields. The developed protocol offers a transition metal-free, ligand-free, catalyst-free methodology and is suitable for a variety of chalcogenide molecules (S and Se) along with various electron-rich and electron-poor chromone-fused indolizine compounds. Cyclic voltammograms and control experiments also validated the plausible reaction pathway.