Substituent-Controlled Regioselective Photoinduced Cyclization of N-Allylbenzamides with N-Sulfonylaminopyridinium Salts

Electrochemical Benzylic C-H Amination via N-Aminopyridinium

An electrochemical protocol for benzylic C(sp3)-H aminopyridylation via direct C-H/N-H cross-coupling of alkylarenes with N-aminopyridinium triflate has been developed. This method features excellent site-selectivity, broad substrate scope, redox reagent-free and facile scalability. The generated benzylaminopyridiniums can be readily converted to benzylamines via electroreductive N-N bond cleavage.

Photoredox-catalyzed unsymmetrical diamination of alkenes for access to vicinal diamines

A photoredox-catalyzed unsymmetrical diamination of alkenes by using N-aminopyridinium salts and nitriles as the amination reagents has been developed. Various vicinal diamines were obtained in moderate to excellent yields under mild reaction conditions. Furthermore, this protocol could be applied in the late-stage modification of pharmaceuticals and natural products. Preliminary mechanistic studies suggested that this methodology may undergo a radical pathway followed by a Ritter-type reaction.

Cobalt-Promoted Photoredox 1,2-Amidoamination of Alkenes with N-Sulfonamidopyridin-1-ium Salts and Free Amines

A cobalt-promoted photoredox 1,2-amidoamination of alkenes with N-sulfonamidopyridin-1-ium salts and free amines for the synthesis of unsymmetrical vicinal diamines has been developed. The reaction handles N-(sulfonamido)pyridin-1-ium salts as the sulfonamidyl radical precursors and free amines as the nucleophilic terminating reagents to enable the formation of two new C(sp3)-N bonds in a single reaction step and offers a route to selectively producing unsymmetrical vicinal diamines with an exquisite selectivity and a good compatibility of functional groups.

Photoredox-Catalyzed Tandem Cyclization of Enaminones with N-Sulfonylaminopyridinium Salts toward the Synthesis of 3-Sulfonaminated Chromones

A photoredox-catalyzed intermolecular tandem sulfonamination/cyclization of enaminones was realized by using N-aminopyridinium salts as the sulfonaminated reagents without transition-metal catalysts or bases. The reaction exhibits a broad scope and good functional group tolerance, good yields, and regioselectivity. Preliminary mechanistic studies support the radical property of the reaction and the involvement of N-centered radical intermediates.

Electrochemical Trifluoromethylation and Sulfonylation of N-Allylamides: Synthesis of Oxazoline Derivatives

We report a new method for the synthesis of trifluoromethylated and sulfonylated oxazolines by electrochemical radical cascade cyclizations of N-allylamides with sodium trifluoromethanesulfinate or sulfonylhydrazines. This protocol provides a green and useful strategy to synthesize trifluoromethylated and sulfonylated oxazolines with a broad substrate scope under ambient conditions.

N-Chlorosulfonyl carbamate-enabled, photoinduced amidation of quinoxalin-2(1H)-ones

Reported herein is the design and development of a new photo-induced amidation protocol with the readily available N-chlorosulfonyl carbamate as an effective amidyl-radical precursor, which could be readily prepared from commercial low-cost chlorosulfonyl isocyanate (CSI) and alcohol feedstocks. The synthetic potency of this developed protocol was well demonstrated by direct amidation of various quinoxalin-2(1H)-ones. The protocol could be further streamlined by implementing a one-pot/two-step/three-component process of CSI, alcohol, and quinoxalin-2(1H)-one, with significantly improved reaction efficiency. This methodology offers an intriguing opportunity for rapid expansion of nitrogen-containing molecular complexity, thus inspiring comprehensive exploration of a new reaction mode of CSI reagent.