Photoredox Mediated Acceptorless Dehydrogenative Coupling of Saturated N-Heterocycles

Abstract

We report herein a direct unsymmetric coupling and controllable aromatization reaction of saturated N-heterocycles enabled by synergistic photoredox and acid catalysis. The reaction furnishes C2−C3 connected biheterocycles in a highly chemo-and regioselective manner under rather mild conditions. Mechanistic studies indicated that the reaction proceeded via enamine-iminium coupling leading to exclusively C2−C3 connection.

Cobaloxime‐Catalyzed Hydrogen Evolution in Photoredox‐Facilitated Small‐Molecule Functionalization

“…In 2019, Luo proposed the generation of iminum ions through PCET (Scheme ) in a report that combined the principles of Wu's coupling (Scheme ) with Li's dehydrogenation (Scheme ) . Here, a Ru(bpy) 3 2+ /Co(dmgH) 2 ClPy system was employed to achieve the oxidation of tetrahydroisoquinoline . After HAT, iminium/enamine tautomerism results in a mixture of enamine and iminium.…”

The Merger of Photoredox and Cobalt Catalysis

“…This chemistry was later proven to be compatible with aqueous reaction media [78]. It should also be noted here that similar cooperative catalysis can facilitate the dehydrogenative coupling of two N-heterocycles by finely tuning the reaction conditions [79]. In addition to C-N bonds, N-N bonds were able to be desaturated to afford azobenzene derivatives by a cobaloxime/photoredox system [80].…”

Synthesis of the Hexahydropyrrolo-[3,2-c]-quinoline Core Structure and Strategies for Further Elaboration to Martinelline, Martinellic Acid, Incargranine B, and Seneciobipyrrolidine

“…Instead, he proposed that dimerization occurred between a pyrrolocarbene, formed from α-elimination of dimethyl phenyl silane oxide, and the corresponding dimethyl phenyl silane enolate. Formation of the dipyrroloquinoline 241 as a side product dimer when utilizing N -phenyl pyrrolidine in reactions with oxidative conditions is today a well-known issue [ 106 , 107 , 108 , 109 , 110 , 111 , 112 ].…”