Methanol → Methyl 3-chloro-6-methoxybenzo[b]thiophene-2-carboxylate

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Reaction Steps

Crude 6-methoxy-3-chlorobenzo[b]thiophene-2-carbonyl chloride (2 g, 7.67 mmoles) was transferred to a 100 ml round bottomed flask. Anhydrous methanol (Aldrich, 50 ml) was added and the acid chloride dissolved by stirring. To this stirred solution was added chlorotrimethylsilane (2.5 equivalents, 19.16 mmole, 2.08 g, 2.43 ml). The reaction mixture was stirred overnight at room temperature. TLC analysis (Silica, 1:1 hexane:ethyl acetate, UV visualization) indicated complete conversion of the acid chloride to the methyl ester. The resulting slurry was concentrated in vacuo to give a yellow solid, which was shown by 1H NMR (DMSO-D6, 400 MHz) to be the desired material. The crude methyl ester was dissolved in hot ethanol (200 ml), the volume was reduced to 150 ml, and allowed to cool to room temperature. The resulting orange ethanolic solution was cooled to -10° C. for 15 minutes. The resulting precipitate was filtered off and dried in vacuo to give 1.25 g of the ester as an off-white solid.

Provenance & Evidence