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A 100 ml 3-necked round-bottomed flask, reflux condenser, thermometer adapter, gas inlet, and Teflon stirrer were oven-dried for 12 hours at 160° C. The apparatus was rapidly assembled, fitted with a thermometer, flushed with dry nitrogen gas, sealed with rubber septa, and allowed to cool to room temperature. The cooled reaction flask was charged with anhydrous dimethyl sulfoxide (40 ml), 2, 6-difluorobenzaldehyde (5 g, 35.18 mmole), anhydrous triethylamine (2.5 equivalents, 87.95 mmole, 8,952 g, 12.33 ml) and methyl thioglycolate (1.1 equivalents, 4.10 g, 38.70 mmole). The mixture was heated to 75° C. with rapid stirring. The progress of the reaction was monitored by TLC (silica, 10% dichloromethane-hexane, UV visualization). After 19 hours the reaction mixture was cooled to room temperature and poured onto an ice/water mixture (250 ml). The resulting slurry was stirred for 20 minutes, filtered, washed with cold water (2×100 ml) and dried in vacuo to give 5.76 g (78%) of methyl 4-fluorobenzo[b]thiophene-2-carboxylate. See, A. J. Bridges, A. Lee, E. C. Madukor, and C. E. Schwartz, Tetrahedron Letters, 33:7499 (1992).

1. temperatureA 100 ml 3-necked round-bottomed flask, reflux condenser, thermometer adapter, gas inlet, and Teflon stirrer
2. customwere oven-dried for 12 hours at 160° C
3. customfitted with a thermometer
4. customflushed with dry nitrogen gas
5. customsealed with rubber septa
6. customThe cooled reaction flask
7. temperatureThe mixture was heated to 75° C. with rapid stirring
8. temperatureAfter 19 hours the reaction mixture was cooled to room temperature
9. filtrationfiltered
10. washwashed with cold water (2×100 ml)
11. customdried in vacuo