A General Platform for Visible Light Sulfonylation Reactions Enabled by Catalytic Triarylamine EDA Complexes

Abstract

Catalytic electron donor–acceptor (EDA) complexes have recently emerged as a powerful and sustainable alternative to iridium- and ruthenium-based photoredox synthetic methods. Yet, these complexes remain underexplored and reliant on the use of meticulously designed acceptors that require previous installation. Herein, we report a novel EDA complex employing tris(4-methoxyphenyl) amine as a catalytic donor for the sulfonylation of alkenes using inexpensive and readily available sulfonyl chlorides. Applying this operationally simple, visible-light-mediated general platform, we report both the redox-neutral and net-reductive functionalization of more than 60 substrates, encompassing vinylic or allylic sulfonylation, hydrosulfonylation, and sulfamoylation of activated and unactivated alkenes and alkynes.

EDA Complex-Promoted Cascade Cyclization of Alkynes Enabling the Rapid Assembly of 3-Sulfonylindoles and Vinyl Sulfone Oxindoles

“…Combining the results from mechanistic studies and previously reported − investigations together, we propose the following mechanism (Figure ). Initially, sodium 4-methylphenylsulfinate 2a combines with 4-methyl- N -(2-(phenylethynyl)­phenyl)­benzenesulfonamide 1a to form an EDA complex I in the presence of K 2 CO 3 . , Upon light irradiation, the generated EDA complex I undergoes a SET from the donor to the acceptor, , forming an oxygen-centered radical II-1 resonating with sulfonyl radical II-2 and an N -sulfonamide radical anion III .…”

“…Alternative, sulfonation via radical involved cascade cyclization processes has been developed, which is initiated by oxidation of a sulfinate anion through photoredox catalysts or excess peroxides . Despite these achievements, there is still a pressing need for general photocatalyst- and transition-metal-free strategies that enable the facile preparation of sulfone-containing indoles …”

Synthesis of Sulfone Methylene-Substituted Indolines by Radical Cascade Cyclization of 2-Alkynylaniline Derivatives

“…Recently, a variety of commonly accessible and efficient sulfonation reagents including sodium sulfite, sulfinic acid, sulfonyl chloride, and sulfonyl hydrazine have been widely studied and applied in different methodologies . Sulfuryl chloride could be reacted with numerous compounds containing unsaturated bonds due to its easy availability and high reactivity . Inspired by the references above and our interest in constructing indolines, we hypothesized whether C3-substituted indolines could be constructed using a new skeleton with sulfuryl chlorides in one-step via the 1,5-HAT process.…”