Carbon Dioxide → 6-Methoxy-2-(4-methoxyphenyl)-3-carboxybenzo[b]thiophene

Participants

Reaction Conditions

Reaction Steps

6-Methoxy-2-(4-methoxyphenyl)-3-bromobenzo[b]thiophene (15.0 g, 42.9 mmol) was dissolved in 300 mL of anhydrous THF under N2 and cooled to −70° C. To this solution was added nBuLi (29.6 mL, 47.4 mmol, 1.6 M solution in hexanes) dropwise via syringe. After stirring at −70° C. for 20 min, a steady stream of CO2 (g) was introduced into the reaction mixture for 15 min. The mixture was allowed to gradually warm to 0° C. and then quenched by pouring the mixture into cold 1 N HCl (500 mL). The aqueous layer was extracted with EtOAc (3×300 mL). The organic layer was dried (Na2SO4) and concentrated in vacuo to a solid. The crude product was chromatographed (SiO2, 25% EtOAc/hexanes) to provide 9.35 g (69%) of 6-methoxy-2-(4-methoxyphenyl)-3-carboxybenzo[b]thiophene as a white solid. mp 166-170° C. 1H NMR (DMSO-d6) δ (doubling due to rotamers) 13.0-12.8 (bs), 8.10 and 7.68 (d, J=8.1 Hz, 1H), 7.63 and 7.47 (d, J=8.6 Hz, 2H), 7.59 and 7.54 (d, J=2.0 Hz, 1H), 7.10 and 6.97 (dd, J=8.1, 2.0 Hz, 1H), 7.02 (d, J=8.6 Hz, 2H), 3.83 and 3.79 (s, 3H), 3.82 and 3.80 (s, 3H). FD mass spec: 315. Anal. Calcd. for C17H14O4S: C, 64.95; H, 4.49. Found: C, 65.19; H, 4.32.

Provenance & Evidence