The reaction of 1,3-adamantanedicarbonamide with chlorocarbonylsulfenyl chloride in hot toluene gives two new oxathiazolone derivatives that have had their structures confirmed crystallographically: 1,3-bis(1,3,4-oxathiazol-2-on-5-yl)-adamantane and 1-cyano-3-(1,3,4-oxathiazol-2-on-5-yl)-adamantane. (Crystal data: C10H14(COC(O)SN)2: P21/m, a = 10.447(2), b = 7.119(3), c = 10.684(2) Angstroem, β = 112.98(1) deg, V = 731.5(3) Angstroem3, z = 2, Dc = 1.536 g cm-3, R = 0.034, Rw = 0.029; (NC)C10H14(COC(O)SN): P21/c, a = 9.153(2), b = 19.134(2), c = 7.130(3) Angstroem, β = 105.38(2) deg, V = 1204(1) Angstroem3, z = 4, Dc = 1.447 g cm-3, R = 0.038, Rw = 0.035).The reaction of the precursor with dimethyl acetylenedicarboxylate (DMAD) in refluxing chlorobenzene gave a mixture that was resolved into pure compounds by Kugelrohr sublimation; these were shown to be sulfur, tetramethyl thiophenetetracarboxylate, 1,3-adamantanedinitrile, 1,3-bis(4,5-bis(methoxycarbonyl)-isothiazol-3-yl)-adamantane, and 1-cyano-3-(4,5-bis(methoxycarbonyl)-isothiazol-3-yl)-adamantane.The structures of the two new isothiazole derivatives were confirmed crystallographically. (Crystal data: C10H14(CNS*DMAD)2: Pca21, a = 15.857(4), b = 11.562(4), c = 13.602(4) Angstroem, V = 2494(2) Angstroem3, z = 4, Dc = 1.424 g cm-3, R = 0.057, Rw = 0.038; C10H14(CN)(CNS*DMAD): P21/c, a = 19.683(2), b = 11.566(3), c = 7.727(3) Angstroem, β = 93.30(2) deg, V = 1756(1) Angstroem3, z = 4, Dc = 1.363 g cm-3, R = 0.079, Rw = 0.076).The pattern of reactivity indicates that the synthetic equivalent of the bis(nitrile sulfide) may be present in solution but has a very short lifetime and failed to react at all with 1,3-adamantanedinitrile.Key words: oxathiazolone, nitrile sulfide, cycloaddition, isothiazole.