On reacting the 3‐aminopyridazines 1a,d,e with dimethyl acetylenedicarboxylate (DMAD), the pyrimido[1,2‐b]pyridazin‐2‐(2H)‐ones 2e‐g, whereas starting from 1f, the 4(4H)‐ones 5a and 3b,d were prepared. In the 2(2H)‐one series, the reactions of 2b with various amino compounds resulted in various types of products. The reaction of N‐methylaminopyridazines 1g,h with DMAD led to the endo‐N‐substituted derivatives 8a,b, whereas 1h with diethyl ethoxymethylenemalonate (DEM) gave the exo‐N‐substituted compound 1k. The constitution of the compounds was proved by spectroscopic and chemical evidences.
ASJC Scopus subject areas
- Organic Chemistry