Sulfinates from Amines: A Radical Approach to Alkyl Sulfonyl Derivatives via Donor–Acceptor Activation of Pyridinium Salts

Abstract

Synthetically versatile alkyl sulfinates can be prepared from readily available amines, using Katritzky pyridinium salt intermediates. In a catalyst-free procedure, primary, secondary, and benzylic alkyl radicals are generated by photoinduced or thermally induced single-electron transfer (SET) from an electron donor–acceptor (EDA) complex, and trapped by SO2 to generate sulfonyl radicals. Hydrogen atom transfer (HAT) from Hantzsch ester gives alkyl sulfinate products, which are used to prepare a selection of medicinal chemistry relevant sulfonyl-containing motifs.

DABSO – A Reagent to Revolutionize Organosulfur Chemistry

“…Willis and co-workers developed a method for the synthesis of alkyl sulfinates and their derivatives from Katritzky pyridinium salts (Scheme 31). 93 This method forms alkyl radicals by photo-or thermally induced SET from an EDA (electron donor-acceptor) complex formed between a Katritzky salt, a Hantzsch ester and an amine additive. This method was shown to have good functional group tolerance, and conditions were developed for use with secondary, -primary and benzylic starting materials.…”

Aliphatic sulfonyl fluoride synthesis via reductive decarboxylative fluorosulfonylation of aliphatic carboxylic acid NHPI esters

“…1Bc). 14 Despite these invaluable advances, the development of general and efficient methods for aliphatic sulfonyl fluoride synthesis is still in high demand.…”

Photocatalytic fluorosulfonylation of aliphatic carboxylic acid NHPI esters

“…17 For example, the Willis group reported a radical approach toward primary and secondary alkylsulfonyl derivatives via donor–acceptor activation of pyridinium salts which were trapped by DABSO to generate sulfonyl radicals (Scheme 1, II, A). 18 Hence, the SO 2 radical insertion/fluorination strategy became a popular method for the construction of the fluorosulfonyl group, with special synthetic advantages in the direct synthesis of sulfonyl fluorides via C–SO 2 F bond formation. 8 Very recently, the Weng group reported a photocatalytic decarboxylative fluorosulfonylation approach for converting aldoxime esters to the corresponding sulfonyl fluorides, 17 f which was enabled by energy-transfer-mediated photocatalysis and N–O bond homolysis.…”