CHEMICAL-TRANSFORMATIONS OF 2,7-DI-TERT-BUTYLTHIEPINE

Selected chemical transformations of a monocyclic thiepine 2,7-di-tert -butylthiepine 1 have been examined. Oxidation of the thiepine 1 gave the unstable thiepine 1-oxide 3, although further oxidation to form th e thiepine 1,1-dioxide 4 did not proceed whilst S-methylation with met hyl iodide-silver tetrafluoroborate gave rearranged aromatized compoun ds. In these electrophilic reactions at sulfur, the steric repulsion b y two tert-butyl groups possibly causes the formation of the endo-sulf ur coordinated species. Bromination gave either the ring-contracted th iophene 12, or the thiopyran 17, depending on the reaction conditions. The cycloaddition with tetracyanoethylene (TCNE) gave the [4 + 2] add uct 22.