Green Synthesis of α-Keton Thiol Ester via Photocatalytic Oxidative Radical Addition of Thioic Acid to Alkene

Abstract

α-Keton sulfides are versatile building blocks in organic synthesis. From thioic acids and alkenes, we were able to develop the direct synthesis of α-keton thiol esters via photocatalytic oxidative radical additions. This reaction well matches the idea of green chemistry. It takes the advantage of thioxanthone as an inexpensive organic photocatalyst, O2 as a green oxidant, EtOAc as a green solvent, and visible light as a sustainable energy source, and the only byproduct is water.

Additive-free aerobic oxidative difunctionalization of alkenes with P4S10 and alcohols to access β-hydroxy phosphorodithioates

“…On the basis of the above experiments and referring to previous reports, 13,17–19 a possible reaction mechanism was proposed as shown in Scheme 4. First, the reaction of P 4 S 10 with EtOH gave the O , O -diethyl S -hydrogen phosphorodithioate 5a .…”

“…13,17 Subsequently, 5a was oxidized by dioxygen in air to afford the thiyl radical 6a along with the generation of hydroperoxide radical species. 18 Then, the selective addition of radical 6a to styrene 1a produced alkyl radical 7a , which was trapped by the hydroperoxide radical to form the hydroperoxide intermediate 8a . Finally, the hydroperoxide intermediate 8a was reduced by EtOH to form the β-hydroxy phosphorodithioate 4aa .…”

Metal-free hydrophosphorodithiolation of alkynes with P4S10 and alcohols leading to vinyl phosphorodithioates

“…Based on the above experiments and related reports, 12,15,16 we proposed a possible reaction mechanism as described in Scheme 3. First, the interaction of P 4 S 10 with EtOH formed the dialkylphosphorodithioate 5 .…”

Ambient-Light-Promoted Stereospecific Synthesis of (Z)-Vinyl Thioesters under Solvent- and Catalyst-Free Conditions

“…We envisioned that a similar bond dissociation behavior may take place between thioacid and olefin, which could lead to a more feasible COS–H bond homolytic cleavage to produce a carbonyl thiyl radical (Scheme b). As a continuation of our interest in photochemistry based on electron donor–acceptor complexes, we present herein an ambient-light-promoted stereospecific synthesis of vinyl thioesters (rather than alkyl thioesters) under solvent- and catalyst-free conditions (Scheme c).…”