Chloroform → 8-(beta-Chloroallyl)-7-butyroxy-4-methylcoumarin

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Rearrangement of CAMC was accomplished in high yield by refluxing the allyl ether from Step 2 (143.5 gm; 0.55 mole) in a mixture of p-diisopropylbenzene (Aldrich, 1000 ml) and butyric anhydride (96 ml, 92.8 gm; 0.59 mol, Aldrich) under argon for 18 hours. The cooled reaction mixture was diluted with chloroform, washed with water and then saturated sodium bicarbonate, dried (MgSO<) then evaporated under reduced pressure. Following recrystallization from ethanol, 79.9 grams of mixed 6 and 8-(β-chloroallyl)-7-butyroxy-4-methylcoumarin (BCAMC,15) were obtained. HPLC analysis (Beckman; C18-ODS reverse phase column, isocratic elution with 60% CH3OH/40% H2O) showed the mixture to contain 85.7% of the desired 8-substituted isomer, of which a sample was purified by column chromatography (60-200 mesh silica gel, elution with CH2Cl2). The structures of the two isomers were confirmed by NMR. NMR (CDCl3) d 7.56 (1H, d), 7.11 (1H, d), 6.26 (1h, d), 5.05-5.19 (2H, m), 3.84 (2H, m), 2.55-2.62 (2H, m), 2.43 (3H, d), 1.78-1.82 (2H, m), 1.01-1.09 (3H, t).

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