opening to the betaine 3′a−e after irradation with UV light. Condensation of the diacetyl groups of the dihydroindolizines (DHIs) 3a−e with hydrazine hydrate in a diethyl ether/ethanol mixture gave the new pyridazinopyrrolo[1,2-b]pyridazines 4a−e. Compounds 4a−e showed no photochromism at room temperature or after cooling with liquid nitrogen. However laser flash spectroscopy was successfully used for