S. Yamazaki et al., CHEMICAL-TRANSFORMATIONS OF 2,7-DI-TERT-BUTYLTHIEPINE, Journal of the Chemical Society. Perkin transactions. I, (18), 1994, pp. 2631-2635
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.