Br[CH2:2][CH2:3][O:4][C:5]([O:20][CH2:21][CH2:22]Br)([C:12]([C:14]1[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1)=[O:13])[C:6]1[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=1.[C:24]1(=[O:34])[NH:28][C:27](=[O:29])[C:26]2=[CH:30][CH:31]=[CH:32][CH:33]=[C:25]12.[K]>CN(C=O)C>[C:24]1(=[O:34])[N:28]([CH2:2][CH2:3][O:4][C:5]([O:20][CH2:21][CH2:22][N:28]2[C:27](=[O:29])[C:26]3=[CH:30][CH:31]=[CH:32][CH:33]=[C:25]3[C:24]2=[O:34])([C:12]([C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)=[O:13])[C:6]2[CH:11]=[CH:10][CH:9]=[CH:8][CH:7]=2)[C:27](=[O:29])[C:26]2=[CH:30][CH:31]=[CH:32][CH:33]=[C:25]12Benzil-di(β-bromoethyl)ketal (8.84 g) and 7.4 g of potassium phthalimide were dissolved in 50 ml of DMF, and reacted at 50° to 60° C. for 6 hours. When the reaction mixture was poured into 100 ml of ice water, white crystals formed. The crystals were collected by filtration, well washed with water, and dried to give 11 g of benzil-di(β-phthalimidoethyl)ketal in a yield of 96%. Recrystallization from a mixture of ethanol and chloroform afforded crystals having a melting point of 132° to 134° C. The product is referred to as initiator 2.
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