The Diels-Alder reaction of 2,3-bis-(phenylthio)-1,3-butadiene (4), derivedin situ by thermal extrusion of sulfur dioxide from 3,4-bis-(phenylthio)-2,5-dihydrothiophene-1,1-dioxide (3), with dimethyl fumarate gavetrans-1,2-bis-(phenylthio)-4,5-dimethoxycarbonyl-1-cyclohexene (1). Similarly, the reaction of4 with maleic anhydride gavecis-4,5-bis-(phenylthio)-4-cyclohexene-1,2-dicarboxylic anhydride(5), which was converted intocis-1,2-bis-(phenylthio)-4,5-dimethoxycarbonyl-1-cyclohexene (2). The characterization of1 and2 included a single-crystal X-ray diffraction study of 1, simulations of portions of their1H NMR spectra, and homonuclear decoupling experiments. The cyclohexene rings of1 and2 are in half-chair conformations with diequatorial and axial-equatorial diester groups, respectively.