Synthesis of nitrogen‐containing heterocycles 6 . Formation and structures of imidazolinones and related compounds through cyclization of diaminomethylenehydrazones with dimethyl acetylenedicarboxylate

Diaminomethylenehydrazones 1 of aromatic and aliphatic carbonyl compounds react with dimethyl acetylenedicarboxylate (DMAD) at room temperature to give four types of heterocycles, (5‐oxoimidazolin‐4‐ylidene) acetates 2, 3 and 6 , (2‐imino‐5‐oxoimidazolidin‐4‐ylidene) acetate 4 and 6‐oxo‐1,6‐dihydropyrimidine‐4‐carboxylates 5 according to the substitution patterns of 1 in moderate to high yields. Amino ( N,N ‐dimethylamino)methylenehydrazones of ketones give exclusively (5‐oxoimidazolin‐4‐yl‐idene) acetates, both ( Z )‐ and ( E )‐isomers 2 and 3 about the exocyclic alkenic linkage, with the ( Z )‐isomer 2 generally being predominant, while those of aldehydes give 5 . Diamino‐ and amino ( N ‐methylamino)methylenehydrazones produce 5 and/or 6 and di ( N ‐methylamino) methylenehydrazone gives (2‐imino‐5‐oxoimidazolidin‐4‐ylidene) acetate 4 as the sole cyclized product.