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

Abstract

Ring Enlargement of 1,2‐Thiazol‐3(2 H )‐one‐1,1‐dioxides and 3‐Amino‐2 H ‐azirines to 4 H ‐1,2,5‐Thiadiazocin‐6‐one‐1,1‐dioxides Reaction of 3‐amino‐2 H ‐azirines 2 with the 1,1‐dioxides 4 and 7 of 1,2‐thiazol‐3(2 H )‐ones and 1,2‐thiazoli‐din‐3‐ones, respectively, in i‐PrOH at room temperature leads to 4 H ‐1,2,5‐thiadiazocin‐6(5 H )‐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‐ 15 N)‐labelled aminoazirine 2a *.