複素環化合物の研究(第11報)Oxazolo[3,2-b]pyridazinium Perchlorateの合成と炭素求核試薬との反応

抄録

2, 6-Disubstituted oxaolo[3, 2-b]pyridazinium perchlorates (VI) were synthesized by acid-cyclization of 2-(α-oxoalkyl)-3(2H)-pyridazinones (V), derived from 6-substituted 3(2H)-pyridazinones (IV) and α-haloketones. Treatment of the quarternary salt (VIa : R¹=C₆H₅, R²=H, R³=Cl) with KOH and NaSH gave Va and 2-phenacyl-3(2H)-pyridazinethione (VIIa), respectively. The reaction of VI with the sodium salts of ethyl cyanoacetate, malononitrile, and ethyl malonate furnished pyrrolo[1, 2-b]pyridazines (IX, XIII, and XIV). This reaction seems to be initiated by the nucleophilic addition of the reagents on C-8a position of VI, followed by ring-opening and re-aromatization to afford pyrrolopyridazine systems.