Pyridazines. XXXV. Preparation of some novel pyrimido[4,5‐c]pyridazine derivatives from 3‐alkylamino‐ and 3‐arylamino‐4‐pyridazinecarboxamides

Abstract

Facile syntheses of pyrimido[4,5‐c]pyridazine‐5,7(6H,8H)diones 4, pyrimido[4,5‐c]pyridazin‐5(8H)‐ones 7–10, and dihydropyrimido[4,5‐c]pyridazin‐5(6H)ones 5,6 starting from 3‐chloro‐4‐pyridazinecarbonitrile 1 via aminocarbonitriles 2 and aminocarboxamides 3 are described. In addition, a convenient access to the new aminopyridazinecarbonitrile 11 from the chloronitrile 1, employing the tetrazolo[1,5‐b]pyridazine 12 as the key intermediate, is reported.