The Pummerer-like reaction of 2,5-bis(trimethylsilyl)thiopheneS-oxide with trifluoroacetic anhydride: intermediary formation of sulfurane [10-S-4(C2O2)] (?4-sulfane)
X-Ray Crystallographic Analysis of 2,5-Bis(diphenylmethylsilyl)thiophene Monooxide and the Diels-Alder Reaction of Thiophene Monooxide with Dienophiles
X-Ray crystallographic analysis of 2,5-bis(diphenylmethylsilyl)thiophene monooxide revealed that the thiophene ring is not a planar structure and that the S-O bond is tilted ca. 14 degrees out of the ring plane. The Diels-Alder reaction of 2,5-bis(trimethylsilyl)thiophene with dienophiles gave the adducts in high yields. The stereochemical courses for the reactions are exclusively endo-orientation and syn-direction with respect to the S-O bond. This stereochemistry agrees with the results obtained from RHF and MP2MO calculations using the 6-31G(*) basis set.
Simple Procedure for the Synthesis of 2,5-Bis(silylated) Thiophene S-Oxides with m-Chloroperbenzoic Acid in the Presence of BF3(Et2O)
Oxidation of 2,5-bis(silyl)thiophenes (1) with m-chloroperbenzoic acid (m-CPBA) in the presence of BF3(Et(2)O) gave the corresponding S-oxides (2) in moderate yields, while, without BF3(Et(2)O), the oxidation gave solely the corresponding thiophene S-dioxides (3) and no S-oxide was obtained at all. This procedure was successfully applied to the synthesis of other 2,5-bis-substituted thiophene monooxides.