Catalyst- and solvent-free, atom- and step-economical synthesis of dithiophosphinates by one-pot domino introduction of sulfur atoms†

A catalyst-free and solvent-free domino-multicomponent reaction of diphenylphosphine, S₈ and alkenes was developed, providing a simple, green, and efficient synthesis of dithiophosphinates with up to >99/1 Markovnikov regioselectivity and 100% atom economy. Notably, by introducing two sulfur atoms with the easily available S₈, this new method allows the construction of S–C–PS with four chemical bonds in one pot, showing incomparable advantages over the reported multi-step methods both in product yield and reaction selectivity. Various alkenes including monosubstituted, disubstituted, trisubstituted and tetrasubstituted alkenes and even polyisoprene are suitable substrates, showing broad substrate scope. The method can be readily extended to alkynes and easily scaled up to the gram scale, showing the practicality of this new method. Mechanistic studies suggested that both the rapid generation of the key diphenyl phosphinodithioic acid intermediate and the electrophilic addition step contributed to the high yield and the excellent selectivity of the reaction.