Crystal structure of O-ethyl N-(ethoxycarbonyl)thiocarbamate

The title compound, C6H11NO3S, provides entries to novel carbamoyl disulfanes and related compounds of interest to our laboratory. The atoms of the central O(C=S)N(C=O)O fragment have an r.m.s. deviation of 0.1077 Å from the respective least-squares plane. While several conformational orientations are conceivable, the crystal structure shows only the one in which the carbonyl and the thiocarbonyl moieties are anti to each other across the central conjugated C—N—C moiety. Pairs of 2.54 Å N—H⋯S=C hydrogen bonds between adjacent molecules form centrosymmetric dimers in the crystal.


S1. Structural commentary
The title compound, O-ethyl N-(ethoxycarbonyl)thiocarbamate (1), C 6 H 11 NO 3 S, CAS registry # 5585-23-9, also known as (N-ethoxythiocarbonyl)urethane, was of interest to a multifaceted organosulfur research program that includes among its goals the development of amino protecting groups removable under mild conditions Barany & Merrifield;Barany et al., 2006, Barany et al., 2015. Specifically, we have shown that reaction of 1 with (chlorocarbonyl)sulfenyl chloride gives rise to the novel (chlorocarbonyl)(N-ethoxycarbonylcarbamoyl)disulfane, rather than the expected putative N-ethoxycarbonyl-1,2,4-dithiazolidine-3,5-dione (Barany et al., 2015). Variations in reaction conditions and/or the nature of sulfenyl chlorides that react with 1 result in additional unusual structures which model previously uncharacterized intermediates in the mechanisms of reactions that successfully elaborate N-alkyl-1,2,4-dithiazolidine-3,5dione heterocycles. Thiocarbamate 1 is also useful as an entry to pharmaceutically relevant heterocycles (Atkins et al., 1973), as an additive in the purification of pyrite (Shen et al., 1998), and as a precursor to compounds of interest to the agrochemical industry (Vallejos et al., 2009).
X-ray quality crystals of 1 were readily obtained after bulk purification (recrystallization from hot hexane, about 7 mL/g).
All molecular parameters of 1 are within expected ranges. Ignoring the ethyl groups, the central fragment of 1 has a r.m.s. deviation of 0.1077 Å from the least squares plane [i.e., the plane consisting of atoms O1, C1, S1, N1, C2, O2, O3].
The largest deviation of any torsion angle from 0 or 180° is 11.5 (3)° for C2-N1-C1-O1. Although there are multiple theoretically stable conformations of 1 (Vallejos et al., 2009), the molecule uniquely assumes the conformation where the carbonyl and the thiocarbonyl moieties are anti to each other across the central C-N-C moiety.
In the crystal, pairs of intermolecular N-H···S=C hydrogen bonds between two adjacent molecules form centrosymmetric dimers (see Figure 2). View of crystal packing down the a-axis, with hydrogen bonds highlighted and atoms involved in hydrogen bonding labeled and numbered.