Unexpectedly Stable (Chlorocarbonyl)(N-ethoxycarbonylcarbamoyl)disulfane, and Related Compounds That Model the Zumach–Weiss–Kühle (ZWK) Reaction for Synthesis of 1,2,4-Dithiazolidine-3,5-diones

The Zumach–Weiss–Kühle (ZWK) reaction provides 1,2,4-dithiazolidine-3,5-diones [dithiasuccinoyl (Dts)-amines] by the rapid reaction of O-ethyl thiocarbamates plus (chlorocarbonyl)­sulfenyl chloride, with ethyl chloride and hydrogen chloride being formed as coproducts, and carbamoyl chlorides or isocyanates generated as yield-diminishing byproducts. However, when the ZWK reaction is applied with (N-ethoxythiocarbonyl)­urethane as the starting material, heterocyclization to the putative “Dts-urethane” does not occur. Instead, the reaction directly provides (chlorocarbonyl)­(N-ethoxycarbonylcarbamoyl)­disulfane, a reasonably stable crystalline compound; modified conditions stop at the (chlorocarbonyl)­[1-ethoxy-(N-ethoxycarbonyl)­formimidoyl]­disulfane intermediate. The title (chlorocarbonyl)(carbamoyl)­disulfane cannot be converted to the elusive Dts derivative, but rather gives (N-ethoxycarbonyl)­carbamoyl chloride upon thermolysis, or (N-ethoxycarbonyl)­isocyanate upon treatment with tertiary amines. Additional transformations of these compounds have been discovered, providing entries to both known and novel species. X-ray crystallographic structures are reported for the title (chlorocarbonyl)­(carbamoyl)­disulfane; for (methoxycarbonyl)­(N-ethoxycarbonylcarbamoyl)­disulfane, which is the corresponding adduct after quenching in methanol; for [1-ethoxy-(N-ethoxycarbonyl)­formimidoyl]­(N′-methyl-N′-phenylcarbamoyl)­disulfane, which is obtained by trapping the title intermediate with N-methylaniline; and for (N-ethoxycarbonylcarbamoyl)­(N′-methyl-N′-phenylcarbamoyl)­disulfane, which is a short-lived intermediate in the reaction of the title (chlorocarbonyl)­(carbamoyl)­disulfane with excess N-methylaniline. The new chemistry and structural information reported herein is expected to contribute to accurate modeling of the ZWK reaction trajectory.