Synthesis of nitrogen-containing heterocycles. 7 reaction of aliphatic diaminomethylenehydrazones with hindered ethoxymethylenecyanoacetate

Article abstract of DOI:10.1002/jhet.5570330447

Aliphatic diaminomethylenehydrazones 1 were reacted with ethyl 2-cyano-3-ethoxy-2-pentenoate 2 to give a number of heterocycles in low to moderate yields, according to the substitution pattern and the size of substituent. When 1 carried a single methyl group on the terminal nitrogen, it gave preferentially 6-oxo-1,6-dihydropyrimidines 4 incorporating N(4) into the ring. In contrast, the reaction between 1c or 1d and 2 led to 6-imino- and 6-oxo-1,6-dihydropyrimidines 7 and 8 along with 3. When the alkylidene moiety was bulky, 1e and 1f, the similar reaction gave 3 in high yields without any cyclized product. Upon exposure to acid, compound 3 yielded 6-oxo-1,6-dihydropyrimidines 6, [1,2,4]triazolo[1,5-c]pyrimidine-8-carboxylate 5 and N-alkenyl-1,2,4-triazoles 9 in addition to 7 and 8 in proportions dictated by the nature of the substituents of 1. The structural assignment and reaction mechanism are discussed.