Alkene adducts of cyclic thiazenes. Identification of exo and endo addition of 1,3,2,4,6-dithiatriazines to 1,5-norbornadiene by 2-D NMR methods and the crystal structure of a single molecule in which both modes of addition are displayed

4-CF3—C6H4—CN3S2, 1, forms symmetrical sulfur-bound adducts with norbornene (NBE), norbornadiene (NBD), and 1-heptene (C7H14), which were studied by 1H, 13C, COSY-45, and HETCORR NMR. 1•NBE exists in solution in a single isomeric form which corresponds to that found in the solid state for 4-CH3O—C6H4—CN3S2•NBE by single-crystal X-ray diffraction: orthorhombic, P212121 with Z = 4, a = 10.224(3), b = 10.369(5), c = 14.075(5). R = 0.0475 and Rw = 0.0492 for 634 data. 1•NBD exists in solution in two isomeric forms which are not interchangeable. One of these corresponds to that found in the NBE adduct, i.e. exo addition; the other is the first example of endo addition. Two bis adducts of stoichiometry NBD•21 have been prepared and separated. They are isomers exhibiting exo-exo and exo-endo addition. The structure of the latter was confirmed by X-ray diffraction: orthorhombic, Pcab with Z = 8, a = 7.816(2), b = 17.264(3), c = 36.842(5). R = 0.068 and Rw = 0.106 for 1506 data. 1•C7H14 exists as a mixture of syn and anti isomers. NMR structure parameters derived here have been applied to published data on over 15 thiazene NBE and NBD adducts.