Technical Note: A Facile and Scalable Synthesis of Versatile Trithiocarbonate Chain Transfer Agents for RAFT Polymerization

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Reversible addition–fragmentation chain transfer (RAFT) polymerization is a key tool in modern macromolecular design. Central to its success is the availability of versatile chain transfer agents (CTAs), typically based on thiocarbonylthio compounds. Herein, we report a refined, scalable, and high-yield synthesis of a family of trithiocarbonate RAFT agents based on a propanoic acid leaving group, mimicking the propagating radical of acrylic acid, which permits efficient mediation of the polymerization of a wide range of monomers. We report the synthesis of 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid (BPTC), commonly known as (Propanoic Acid)yl Butyl TrithioCarbonate (PABTC), a highly oil-soluble derivative, 2-{[(dodecylsulfanyl)carbonothioyl]sulfanyl}propanoic acid (DoPAT), and a highly water-soluble derivative, 3-[[[(1-carboxyethyl)thio]carbonothioyl]thio]propanoic acid (CETCP). By optimizing the aqueous-based reaction conditions, we achieved yields of 80% or higher of high-purity products across all three derivatives on a tens of grams scale, without the necessity of intensive organic solvent extraction or multiple recrystallization steps.