AbstractThe reaction of 3,4‐di‐tert‐butylthiophene (6a) with N‐[(p‐tolylsulfonyl)imino]‐phenyliodinane (TsN=IPh) in the presence of Cu(MeCN)4PF6 in MeCN at room temperature provided 3,4‐di‐tert‐butyl‐1‐[(p‐tolylsulfonyl)imino]‐1,1‐dihydrothiophene (3b),3,4‐di‐tert‐butyl‐1,1‐bis[(p‐tolylsulfonyl)imino]‐1,1‐dihydrothiophene (5a), and 1‐(p‐tolylsulfonyl)‐3,4‐di‐tert‐butylpyrrole (7a) as the principal products. The use of 20 molar amounts of 6a gave 3b in an increased yield of 61%. Treatment of 3,4‐di‐tert‐butylthiophene 1‐oxide (1a) with (CF3CO)2O or (CF3SO2)2O, followed by reactions with RSO2NH2, ROC(=O)NH2, or RCONH2, furnished a series of S‐imino derivatives (3b,c,e–h) of 6a, which carry an electron‐withdrawing substituent on the imino nitrogen atom. Treatment of the S‐imino derivative 3f (substituent on the nitrogen atom = COBu) with CF3CO2H gave an aminosulfonium salt (13), whose deprotonation led to the parent N‐unsubstituted 1‐imide derivative (3n). Treatment of 2,4‐di‐tert‐butylthiophene 1‐oxide (1b) with TsN=IPh in the presence of Cu(MeCN)4PF6 in MeCN at room temperature provided 2,4‐di‐tert‐butyl‐1‐[(p‐toluenesulfonyl)imino]‐1,1‐dihydrothiophene 1‐oxide (4e) in 81% yield. Hydrolysis of 4e by concentrated H2SO4 at room temperature furnished 2,4‐di‐tert‐butyl‐1‐imino‐1,1‐dihydrothiophene 1‐oxide (4f) in 89% yield. A pair of enantiomers of 4f were separated by high‐performance liquid chromatography (HPLC) on a chiral column, and their absolute configurations were determined by an X‐ray crystallographic analysis. Structures of sulfilimine, sulfone diimine, and sulfoximine derivatives of monocyclic thiophenes, obtained in these ways, are discussed based on spectroscopies (IR and 1H and 13C NMR) and X‐ray crystallographic analyses. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:333–348, 2001