A Structure and Mechanism Correction

It was reported in 1993 that reaction of Ar-(2-bromoethyl)phthalimide with the dianion of isobutyric acid gave the aroylaziridine 1, and that treatment of 1 with hydrazine in ethanol at 60°C gave the phthalazin-1 (2//)-one 2. Tentative mechanisms were suggested for the formation of 1 and 2. It was subsequently rapidly established, however, that while the condensation of the phthalimide with the dianion was fully reproducible (almost quantitative crude yield), the structure of the product was not 1 as claimed. It was shown that the correct structure for the 

Give mechanisms for the formation of 3 and the conversion of 3 into 2. Show also that acceptable mechanisms can be drawn for the formation of 1 and for its conversion into 2. 

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