Chlorosulfonic acid → 2-(4-Chlorosulfonyl-3-methoxy-phenyl)-2-methyl-propionic acid methyl ester

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Reaction Steps

Chlorosulfonic acid (11.5 mL) was cooled to 0° C. Then compound 21A (4.6 g, 22 mmol) was added over 15 min. The mixture was stirred at RT for 3 h and then poured into ice (100 g). The cloudy solution was extracted with CH2Cl2 (2×50 mL) The extracts were dried with MgSO4 and concentrated to give a purple oil which was passed through a short pad of silica gel to afford the desired product 21B (2.43 g 36%) as an orange oil. MS m/z 271 (M−Cl). Step 3. Preparation of 2-(4-Mercapto-3-methoxy-phenyl)-2-methyl propionic acid methyl ester (Compound 21C)

Provenance & Evidence