Study on the preparation of heteroaryl substituted enamines. A simple synthesis of heteroaryl substituted acetaldoximes from enamines

A comparative study of the reactivity of methyl groups towards N, N ‐dimethylformamide dimethyl acetal and tert ‐butoxybis(dimethylamino)methane was carried out on methyl substituted six‐membered nitrogen containing heterocycles 1 to give enamines 2 , which were easily transformed to oximes by treating with hydroxylamine hydrochloride in methanol. Most of them were isolated as ( E, Z )‐oximes of heteroarylacetaldehyde ( 11 ), but 5‐(1,2,4‐triazinyl) substituted derivatives as ( E, Z )‐oximes of 2,5‐dihydro‐1,2,4‐triazin‐( Z )‐5‐ylideneacetaldehyde ( 11t, 11u , and 12 ). Oximes were finally transformed to the corresponding acetonitriles 16 and 3‐(dimethylamino)acrylonitriles 17 .