O,S-Dimethyl Carbonodithioate as Phosgene Substitute for the Preparation of S-Methyl Alkylcarbamothioates and Dialkylcarbamothioates

O,S-dimethyl carbonodithioate is proposed as a suitable and safely handled reagent that can be used as a replacement for phosgene in the synthesis of S-methyl alkyl- and dialkylcarbamothioates. The former were opbatined by a two-step procedure, which can also be carried out in a one-pot fashion without isolating the intermediates O-methyl alkylcarbamothioates; the overall yields of the pure S-methyl alkylcarbamothioates were 94-98%. Optimal conditions for the synthesis of S-methyl dialkylcarbamothioates involved a one-step procedure in a solvent-free system in the presemnce of triethyl(methyl)ammonium methyl carbonate as a catalyst; yields of the pure products were 85-98%. A mechanism is proposed for the carbamothioate-formation reaction.