Seven novel 2,3'-diacetyl spirotertrahydroindolizines (THIs) 3a-g were synthesized in low yield via the nucleophilic addition of the substituted isoquinoline derivatives 2a-g to diacetyl spirocyclopropene 1 in dry ether at -20 degrees C under nitrogen atmosphere for 3 h, which undergo ring opening the corresponding betaines 3''' a-g through betaine 3'a-g and 3"a-g as intermediates after irradiation with UV-light. The serious decomposition of these products during purification process was moderately prevented by using flash chromatography after many trials. In situ hydrazinolysis of THIs 3a-g with hydrazine in ethanol at -40 degrees C afforded a novel type of cis-fixed pyridazinopyrrolo[1,2-b]isoquinolines 4a-g in moderate yield.