<sup>1</sup>H,<sup>13</sup>C,<sup>17</sup>O NMR and quantum-chemical study of the stereochemistry of the sulfoxide and sulfone derivatives of 3-arylidene-1-thioflavan-4-one epoxides
ab initio MO study and also the examination of the 17O and 13Cchemicalshifts, calculated for the global minima structures of the sulfone isomers by the GIAO method. Analogous results, obtained for the sulfoxide isomers (4, 5), not only led to the preferred conformers but also gave evidence for the trans arrangement of the 2‐Ph group and the oxygen atom of the SO group. Chemicalshift differences
Sulfur atom of the trans, cis- and trans, trans-epoxides 1 of (Z)-3-arylidene-1-thioflavanones have been oxidized with dimethyldioxirane to afford the appropriate sulfoxides 2 and sulfones 3 depending on the amount of oxidant used.