[Cl:1][C:2]1[CH:3]=[C:4]([N:8]2[C:16]3[C:11](=[CH:12][CH:13]=[CH:14][CH:15]=3)[CH2:10][C:9]2=[O:17])[CH:5]=[CH:6][CH:7]=1.[CH:18](OCC)(OCC)[O:19][CH2:20][CH3:21].C([O-])([O-])[O-]>CCOCC>[Cl:1][C:2]1[CH:3]=[C:4]([N:8]2[C:16]3[C:11](=[CH:12][CH:13]=[CH:14][CH:15]=3)[C:10](=[CH:18][O:19][CH2:20][CH3:21])[C:9]2=[O:17])[CH:5]=[CH:6][CH:7]=11-(3-Chlorophenyl)-2(1H,3H)-indolone (2.4 g, 0.01 mole) and triethyl orthoformate (8.3 ml, 0.05 mole) were combined and heated at 150°±10° for 18 hours. An additional 20 ml of the orthoformate were added and heating continued 2 hours. The reaction mixture was cooled to 25°, diluted with ether, washed with H2O and then brine, dried over MgSO4, concentrated in vacuo to oily solids, and triturated with pentane to yield solids (4.2 g). The solids were chromatographed on silica gel (7.5×15 cm) with 4:1 hexane:ethyl acetate as eluant to yield purified title product, 0.5 g; m.p. 132°-134°; m/e 310/299.
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