Carbon tetrabromide → HCID 18449299, compound

Participants

Reaction Conditions

Reaction Steps

Ex-1B: A solution of triphenylphosphine (8.64 g, 32.9 mmol) and CBr4 (5.4 g, 16.3 mmol) in 140 mL of dichloromethane was stirred at room temperature for 15 min. Then 2,4-dimethoxy-5-thiophen-2-yl-benzaldehyde (3.1 g, 12.5 mmol) from Ex-1A was added, and the mixture was stirred overnight. The solvent was reduced to 30 mL and then filtered through silica gel with hexanes as eluent. After evaporation of the solvents, the crude 2-[5-(2,2-dibromo-vinyl)-2,4-dimethoxy-phenyl]-thiophene was dissolved in THF (40 mL) and cooled to −78° C. Then n-butyllithium (25.6 mmol, 16 mL of a 1.6 M solution in hexanes) was added dropwise while maintaining an internal temperature below −70° C. After stirring the reaction mixture for 1 h at −78° C., the reaction was quenched with a saturated NH4Cl solution. This solution was extracted with ethyl acetate, and the organic layer was dried over anhydrous magnesium sulfate. The solvent was removed under reduced pressure, and the residue was chromatographed on silica gel (hexane/ethyl acetate, 1:1) to give 2.05 g (67%) of 2-(5-ethynyl-2,4-dimethoxy-phenyl)-thiophene as a yellow solid, m.p. 141–142° C. 1H-NMR (300 MHz, CDCl3) δ 7.73 (s, 1H), 7.38 (dd, 1H, J=3.7 and 1.3 Hz), 7.28 (dd, 1H, J=5.2 and 1.3 Hz), 7.06 (dd, 1H, J=5.2 and 3.7 Hz), 6.51 (s, 1H), 3.96 (s, 6H), 3.27 (s, 1H).

Provenance & Evidence