“…We have previously reported that 2-acetyl-5,5-dimethylpyrazolidin-3-one (1) undergoes photochemical reaction upon irradiation to give 1 -acetamidoazetidin-2-one (2) in 65% yield.1 Since that time, we have found that irradiation of l-acetyl-5,5-dimethylpyrazolidin-3-one (3) gives 2 also, in 30% yield. Furthermore, irradiation of the nitrogen unsubstituted 5,5-dimethylpyrazolidin-3-one (4) gives the parent system l-aminoazetidin-2-one (5) in 15% yield.…”