Repetierbare Ringerweiterungen durch [2,3]‐sigmatropische Umlagerungen in cyclischen Allylsulfonium‐allyliden; Synthese von mittleren und grossen Thiacyclen. Vorläufige Mitteilung

Repeatable ring expansions by [2,3]‐sigmatropic shifts in cyclic allylsulfonium allylides; synthesis of medium‐ and large‐sized thiacycles Allylation of a 2‐vinyl thiacyclus with allyl bromide in 2,2,2‐trifluoroethanol followed by ylide generation by use of aqueous potassium hydroxide results in a [2,3]‐sigmatropic rearrangement with formation of a new 2‐vinyl thiacyclus enlarged by three carbon atoms (Scheme 1). In this way, starting from the 5‐membered ring 1, a series of four ring enlargement sequences leads to the 17‐membered thiacycles 9 and 10 via the 8‐, 11‐ and 14‐membered rings 4, 7 and 8 (Scheme 2).