Forging C−S Bonds on the Azetidine Ring by Continuous Flow Photochemical Addition of Thiols and Disulfides to Azetines

A strategy for anti-Markovnikov hydroalkyl/aryl thiolation and disulfidation of 2-azetines under continuous flow conditions has been developed. Thiyl radicals are generated from thiols or disulfides and subsequently propagate into the azetine unsaturation to forge the C−S bond and shape a secondary radical intermediate. This carbon-centered radical chain transfers to another thiol via hydrogen atom transfer (HAT) or another disulfide to regenerate the key thiyl radical intermediates. The use of flow technology ensures efficient irradiation of the reaction mixture leading to extremely fast, robust, and scalable protocols. Furthermore, ethyl acetate was adopted as an environmentally responsible solvent.