[CH:1]1[CH:6]=[C:5]2[C:7]([C:9]3[C:17](=[O:18])[CH:16]=[CH:15][C:13](=[O:14])[C:10]=3[C:11](=[O:12])[C:4]2=[CH:3][CH:2]=1)=[O:8].[CH2:19]=[CH:20][C:21]([Cl:23])=[CH2:22]>C(O)(=O)C.CCOCC>[Cl:23][C:21]1[CH2:22][CH:16]2[CH:15]([C:13](=[O:14])[C:10]3[C:11](=[O:12])[C:4]4[CH:3]=[CH:2][CH:1]=[CH:6][C:5]=4[C:7](=[O:8])[C:9]=3[C:17]2=[O:18])[CH2:19][CH:20]=1Quinizarinquinone (I) (1.0 g, 4.2 mmol) and chloroprene (1.12 g, 12.6 mmol) were dissolved in acetic acid (6 ml, glacial) and stirred at ambient temperature under nitrogen for 2.5 days. The reaction mixture was then diluted with ether (25 ml), the reaction mixture filtered, the retained precipitate washed with ether and dried under reduced pressure in the presence of phosphorus pentoxide to yield 9-chloro-6a,7,10,10atetrahydro-5,6,11,12-naphthacenetetraone (II) (988 mg, 72%). Recrystalization (chloroform-ether) gave the foregoing compound in analytical purity m.p. 221°-222° C.,
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