[OH:1][N:2]1[C:6](=[O:7])[C:5]2=[CH:8][CH:9]=[CH:10][CH:11]=[C:4]2[C:3]1=[O:12].[CH3:13][O:14][C:15]([CH3:17])=[CH2:16]>CC#N.C([O-])(O)=O.[Na+].C1(C)C=CC(S(O)(=O)=O)=CC=1>[CH3:13][O:14][C:15]([CH3:17])([O:1][N:2]1[C:3](=[O:12])[C:4]2[C:5](=[CH:8][CH:9]=[CH:10][CH:11]=2)[C:6]1=[O:7])[CH3:16]To a solution of 20 g (123 mmol) of N-hydroxyphthalimide in 360 ml of CH3CN, 26.42 ml (276 mmol) of 2-methoxypropene and 42.36 mg (0.246 mmol) of anhydrous p-toluenesulfonic acid are added in portions at r.t. After stirring for 1 h, the mixture is diluted with 25 ml of sat. NaHCO3 and concentrated under reduced pressure. The residue is extracted with EtOAc and the organic layer is washed with H2O and brine, dried over MgSO4 and concentrated under reduced pressure to give 21.84 g of 2-(1-methoxy-1-methyl-ethoxy)isoindole-1,3-dione as a white solid; NMR (CDCl3): 1.57 (s, 6H), 3.61 (s, 3H), 7.75 (dd, 2H, J=5.56 Hz, J=3.0 Hz), 7.83 (dd, 2H, J=5.56 Hz, J=3.0 Hz).
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