Ringerweiterung von 1,2‐Thiazol‐3(2H)‐on‐1,1‐dioxiden und 3‐Amino‐2H‐azirinen zu 4H‐1,2,5‐Thiadiazocin‐6‐on‐1,1‐dioxiden

Ring Enlargement of 1,2‐Thiazol‐3(2H)‐one‐1,1‐dioxides and 3‐Amino‐2H‐azirines to 4H‐1,2,5‐Thiadiazocin‐6‐one‐1,1‐dioxides Reaction of 3‐amino‐2H‐azirines 2 with the 1,1‐dioxides 4 and 7 of 1,2‐thiazol‐3(2H)‐ones and 1,2‐thiazoli‐din‐3‐ones, respectively, in i‐PrOH at room temperature leads to 4H‐1,2,5‐thiadiazocin‐6(5H)‐one‐1,1‐dioxides 5 (Scheme 2, Table) and the corresponding 7,8‐dihydro derivatives 8 (Scheme 4), respectively. The structure of some of the new 8‐membered heterocycles as well as the structure of the minor by‐product 6 (Scheme 3) have been established by X‐ray crystallography (Chapt. 4). The proposed reaction mechanism for the ring expansion to 5 and 8 (Scheme 2) is in accordance with previously published results of reactions of 2 and NH‐acidic heterocycles and is further supported by the results of the reaction of 4a and the (1‐15N)‐labelled aminoazirine 2a*.