Ring‐opening reactions of 5‐(aryl)thianthrenium bromides with aryl thiolates

Abstract

AbstractA series of 5‐(aryl)thianthrenium bromides (6a–e) with aryl (Ar) groups phenyl (a), p‐tolyl (b), p‐anisyl (c), p‐chlorophenyl (d) and p‐bromophenyl (e) was prepared by reaction of thianthrene 5‐oxide with the appropriate Grignard reagent ArMgBr. Reactions of 6a–e with aryl thiolates (Ar′SNa, Ar′ = phenyl, p‐tolyl and p‐chlorophenyl, 7a–c) were carried out in MeCN at room temperature. Products from 6a–c were a small amount of arene [benzene (8a) and toluene (8b)], and substantial amounts of ArSAr′ (9), thianthrene (Th) and a trisulfide, namely a 2‐(ArS)‐2′‐(Ar′S)‐diphenyl sulfide (10). Products from reactions of 6d,e were smaller amounts of 9 and 10 but substantial amounts of 1,4‐di(Ar′S)benzene (11) and a tetrasulfide (12a–c). The reactions that lead to products 9–12 are attributed to ligand coupling (LC) pathways in sulfuranes formed by attack of Ar′S− at the sulfonium S atom of 6. In the formation of 11 and 12 the halogen atom (Cl, Br) is first displaced from 6d,e by Ar′S−, giving a new thianthrenium ion (14) from which sulfurane formation (15) follows. Products 10 and 12 result from opening of the thianthrenium ring of sulfuranes 13 and 15 through LC. Products were assayed with a combination of GC and isolation with TLC, and were identified with a combination of GC (authentic compounds), x‐ray crystallography (10a), elemental analyses and high‐resolution mass spectrometry. The reactions of 6 are compared with earlier reactions of 5‐(alkoxy)‐and 5‐(alkyl)thianthrenium salts (1 and 2). Copyright © 2002 John Wiley & Sons, Ltd.