Triethylamine → rac-3,4-dihydro-2,5,7,8-tetramethyl-2-[(2-thienyl) ethynyl]-2H-1-benzopyran-6ol

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A mixture of 4.6 g (20 mmol) of rac-3,4-dihydro-2-ethynyl-2,5,7,8-tetramethyl-2H-1-benzopyran-6-ol, 6.3 g (30 mmol) of 2-iodothiophene, 0.8 g of triphenylphosphine, 0.19 g of cuprous iodide, 6 ml of triethylamine and 200 ml of acetonitrile was stirred and degassed with argon for 15 minutes. Palladium acetate, 220 mg, was then added and stirring under argon was continued for 4 hours. The solvent was removed under reduced pressure and the residue was partitioned between methylene chloride and saturated aqueous sodium bicarbonate solution. The organic phase was separated, dried and evaporated. The residue was chromatographed over 200 g of silica gel (Merck 70-230 mesh) using methylene chloride. Crystallization of the combined clean fractions from ether/hexane yielded 3.5 g (56%) of rac-3,4-dihydro-2,5,7,8-tetramethyl-2-[(2-thienyl)ethynyl]-2H-1-benzopyran-6-ol with m.p. 112°-114° C.

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