[C:1]1(=[O:11])[NH:5][C:4](=[O:6])[C:3]2=[CH:7][CH:8]=[CH:9][CH:10]=[C:2]12.[K].Br[CH2:14][C:15](=[O:20])[C:16]([CH3:19])([CH3:18])[CH3:17]>C1(C)C=CC=CC=1>[CH3:17][C:16]([CH3:19])([CH3:18])[C:15](=[O:20])[CH2:14][N:5]1[C:1](=[O:11])[C:2]2[C:3](=[CH:7][CH:8]=[CH:9][CH:10]=2)[C:4]1=[O:6]Potassium phthalimide (82.86 g, 0.447 mol) is added to a stirred solution of bromopinacolone (80.10 g, 0.447 mol) in toluene (300 ml). The-suspension is refluxed for 19 h, cooled, and then the precipitate is filtered off and discarded. The filtrate is cooled in an ice-bath and treated with petroleum ether (550 ml). The resulting precipitate is collected by filtration. The mother liquor is reduced to circa 100 ml by evaporation in vacuo, and a further quantity of precipitate which forms is collected by filtration and combined with the first crop, giving 2-(3,3-dimethyl-2-oxo-butyl)-isoindole-1,3-dione (total yield 83.5 g, 76%) as colourless crystals, m.p. 96-99° C.
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