Diisopropylamine → Methyl 2-acetyl-7-benzyloxy-8-n-propylchroman-2-carboxylate

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Reaction Conditions

Reaction Steps

A 100 ml 3 neck roundbottom flask was fitted with a magnetic stirring bar, dropping funnel, serum cap, and gas inlet tube, flushed with argon and flame dried. 1.11 g or 1.54 ml (11 mmole) of diisopropylamine and 30 ml dry tetrahydrofuran were added. After cooling to -20° C., 6.43 ml of 1.71M n-butyl lithium (11 mmole) was added dropwise via syringe. The solution was stirred 15 minutes at -10° C. and then cooled to -70° C. 3.40 g (10 mmole) of the product of Example 22 in 20 ml tetrahydrofuran at -70° C. was added dropwise over a period of half hour. After stirring one additional hour at -70° C., 1.27 g (11.5 mmole) of acetylimidazole in 10 ml tetrahydrofuran was added and the reaction mixture allowed to warm slowly to -10° C. 0.5M potassium hydrogen sulfate solution was added until the pH reached 2.0, the layers were separated and 100 ml ethyl acetate was added. The organic layer was washed with 0.5M potassium hydrogen carbonate, twice with water and then dried with anhydrous magnesium sulfate. After filtration, the ethyl acetate was removed by rotary evaporation and the residual oil purified by high pressure liquid chromatography (10% ethyl acetate-hexane) to give 2.42 g (63%) of the title compound as an oil. Calc: C, 72.22; H, 6.85; Found: C, 72.43; H, 6.86.

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