Visible-Light-Driven Nitrogen Radical-Catalyzed [3 + 2] Cyclization of Vinylcyclopropanes and N-Tosyl Vinylaziridines with Alkenes

Abstract

A visible light photoredox-promoted and nitrogen radical catalyzed [3 + 2] cyclization of vinylcyclopropanes and Ntosyl vinylaziridines with alkenes is developed. Key to the success of this process is the use of the readily tunable hydrazone as a nitrogen radical catalyst. Preliminary mechanism studies suggest that the photogenerated nitrogen radical undergoes reversible radical addition to the vinylcyclopropanes and N-tosyl vinylaziridines to enable their ring-opening C−C and C−N bond cleavage and ensuing cyclization with alkenes.

Visible-Light Photoredox-Catalyzed Formal [5 + 1] Cycloaddition of N-Tosyl Vinylaziridines with Difluoroalkyl Halides

“…By utilizing nucleophilic ring-opening and metal-catalyzed ring-opening strategies, the synthesis of diverse N-heterocycles from vinylaziridines through [3 + 1], [3 + 2], [3 + 3], [3 + 4], and [5 + 2] cycloadditions with different synthons is well-known. In sharp contrast, radical initiated selective ring-opening functionalization of aziridines via nitrogen-centered radical − remains underdeveloped. Recently, Maruoka developed the thiyl-radical-catalyzed [3 + 2] cyclization ring opening of vinylaziridines and alkenes .…”

“…Recently, Maruoka developed the thiyl-radical-catalyzed [3 + 2] cyclization ring opening of vinylaziridines and alkenes . Remarkably, identical transformations were also achieved through nitrogen radical catalysis by Chen . Therefore, developing new radical reactivities and novel [5 + 1] cycloaddition reactions of vinylaziridines is highly desired.…”

Photoredox Generation of Isothiouronyl Radical Cations: A New Platform in Covalent Radical Catalysis

“…Spirooxindole‐based VCPs are also unreactive substrates in this transformation ( 4 j ). In the meantime, the reported catalytic system has proved to be competitive with previous approaches relying on hydrazonyl [17] and bromyl radicals [18] since proceeding with short reaction times and with high functional group tolerance.…”

Visible‐Light‐Mediated Ring‐Opening Reactions of Cyclopropanes

“…(Scheme 40). [86] A combination of photocatalyst [Ir(ppy) 2 dtbbpy]PF 6 and hydrazone-based NCR catalyst C2, derived from acetone and p-toluenesulfonyl hydrazide, delivered the products 59 in excellent yields with moderate diastereoselectivity. In general, the reaction of vinyl cyclopropanes with electron-deficient alkenes gives excellent yields compared to the reaction with electron-rich alkenes.…”