Additionen von 2,2‐Dimethyl‐3‐dimethylamino‐2 H ‐azirin an 2‐Formyl‐cycloalkanone und Sulfinsäuren

2,2‐Dimethyl‐3‐dimethylamino‐2 H ‐azirine ( 1 ) reacts with the formyl‐cycloalkanones 4 – 8 in boiling benzene to give the 1:1 adducts 13 – 17 in 60–99% yield (Table). These adducts are N′‐[(2‐oxo‐cycloalkylidene)‐methyl] derivatives of 2‐amino‐N, N‐dimethylisobutyramide. The reaction mechanism (Scheme 6) is analogous to the mechanism of the reaction of 1 with carboxylic acids and cyclic enolisable 1,3‐diketones [1]. Sulfinic acids and 1 undergo a similar reaction at −15° to yield 2‐sulfinamido‐N, N‐dimethylisobutyramides (Schemes 4 and 7), while sulfonic acids and the azirine 1 lead to a dimeric salt of type 20 , which with sodium hydroxide gives the dihydropyrazine 21 (Scheme 5).