methyl (RS)-3-(1-cyclopropyl-prop-2-ynyloxy)-4,5-dimethoxy-benzoate → 2-Cyclopropyl-7,8-dimethoxy-2H-chromene-5-carboxylic acid methyl ester

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33.5 g of methyl (RS)-3-(1-cyclopropyl-prop-2-ynyloxy)-4,5-dimethoxy-benzoate were dissolved in 330 ml of N,N-diethylaniline, heated to 200° C. under argon and stirred at 200° C. for a further 5 hrs. The solvent was distilled off at 90° C./1 mbar and the residue was extracted: 2×1.5 l of diethyl ether, 2×1.5 l of 1N HCl, 2×1.5 l of saturated NaCl. The oil obtained was purified by silica gel chromatography with toluene, then toluene/ethyl acetate 9:1. Crystallization was effected from diethyl ether and hexane. Methyl (RS)-2-cyclopropyl-7,8-dimethoxy-2H-1 -benzopyran-5-carboxylate was obtained as white crystals.

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