O[C:2]1[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([O:12][CH3:13])[CH:10]=2)[O:5][C:4](=[O:14])[CH:3]=1.O=P(Cl)(Cl)[Cl:17].C(N(CCCC)CCCC)CCC>C1(C)C=CC=CC=1>[Cl:17][C:2]1[C:11]2[C:6](=[CH:7][CH:8]=[C:9]([O:12][CH3:13])[CH:10]=2)[O:5][C:4](=[O:14])[CH:3]=1A stirred mixture of 4-hydroxy-6-methoxycoumarin (116 g, 0.603 mole) and POCl3 (462.29 g, 3.015 mole) in toluene is treated dropwise with tri-n-butylamine (250 mL, 1.73 mole) at 25° C., heated at 100°-110° C. and monitored by HPLC analysis. When the reaction is complete, the mixture is cooled to room temperature, poured over ice, stirred mechanically for about 2 hours and filtered. The filtercake is washed with water and toluene, dissolved in methylene chloride and filtered through diatomnaceous earth. The methylene chloride filtrate is concentrated and treated with a mixture of dimethylformamide and acetonitrile to afford crystallization. The mixture is filtered to give the title product, 81.7 g, (64% yield) identified by HPLC analysis.
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