Ethynyltributyltin → ethyl 8-chloro-6-ethynyl-2-(trifluoromethyl)-2H-chromene-3-carboxylate

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To 0.86 g (2.0 mmole) of ethyl 8-chloro-6-iodo-2-(trifluoromethyl)-2H-chromene-3-carboxylate was added 46 mg (0.040 mmole) tetrakis(triphenylphosphine)palladium(0), 6 mLs degassed toluene and 0.64 mL (0.69 g, 2.2 mmole) tributyl(ethynyl)tin. The stirred mixture was heated to reflux for 3 h. After allowing the reaction to cool, the mixture was washed with 20% aq. ammonium fluoride and the aqueous layer extracted three times with diethyl ether. The combined extracts were filtered through silica, the silica washed with diethyl ether and the organic fractions concd in vacuo. Chromatographic purification (70 g silica, 5% ethyl acetate/hexanes) afforded a solid which was triturated with hexanes to give 0.50 g (75.6%) of a crystalline solid: 1H NMR (d6-acetone/400 MHz) 1.32 (t, 3H, J=7.1 Hz), 3.73 (s,1H), 4.32 (m, 2H), 6.04 (q, 1H, J=6.9 Hz), 7.60 (m, 2H), 7.90 (s, 1H); 19F NMR (d6-acetone/400 MHz) −79.6 (d, 3F, J=6.8 Hz); MS(ESI+) 331 (M+1, 100, one Cl pattern).

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