p-Toluenesulfonic acid → Ethyl 11-bromoundecanoate

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Reaction Steps

This example is a method of synthesis for inventive compound no. 3556. A solution of 11-bromoundecanoic acid (available from Aldrich, 5.70 g, 22 mmol) and p-toluenesulfonic acid (0.1 g) in absolute ethanol (100 ml) was refluxed for 3 hours. Saturated aqueous sodium bicarbonate solution (40 ml) was added and the reaction mixture was extracted with dichloromethane (3×70 ml). The combined extracts were washed with water (50 ml) and saturated aqueous salt solution (50 ml), and then the solvent was evaporated to a colorless oil. Ethyl 11-bromoundecanoate (5.92 g, 94% yield) was collected during distillation (2 mm) at 135° C. A solution of the bromoester (5.92 g, 20 mmol) and 1-sodiotheobromine (4.08 g, 20 mmol) in dimethylsulfoxide (80 ml) was stirred for 18 hours at ambient temperature. The mixture was added to water (100 ml) and dichloromethane (100 ml). The aqueous layer was extracted with dichloromethane (2×80 ml). The combined organic layers were washed with water (80 ml) and saturated aqueous salt solution (80 ml), dried over magnesium sulfate, and evaporated under vacuum to a white solid. The residue was recrystallized in dichloromethane/ether/hexane, yielding 4.95 g of 1-(ethyl 11-yl-undecanoate)-3,7-dimethylxanthine (62% yield).

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