反应详情

A stirred solution of concentrated hydrochloric acid (3.2 mL) in water (3.6 mL) at from 0° C. to 5° C. is treated with methyl 3-amino-4-(methylthio)benzoate (1.97 g; that is prepared as described in Reference Example 52), followed by a solution of sodium nitrite (0.82 g) in water (2 mL), at such a rate that the temperature remains from 0° C. to 5° C. The mixture is then allowed to warm to room temperature and it is stirred for a further period of 1 hour. The reaction mixture is treated with water (30 mL) and then heated to 55°-60° C., until the evolution of nitrogen ceased (4 hours). The mixture is extracted with dichloromethane (2×100 mL) and the combined organic extracts are dried and concentrated. The resulting brown oil is subjected to flash chroma- tography, eluting with a mixture of diethyl ether and pentane (1:4 v/v), to give methyl 3-hydroxy-4-(methylthio)benzoate (0.6 g) in the form of a yellow solid.

1. customthat is prepared
2. customremains from 0° C. to 5° C
3. temperatureheated to 55°-60° C., until the evolution of nitrogen
4. custom(4 hours)
5. extractionThe mixture is extracted with dichloromethane (2×100 mL)
6. customthe combined organic extracts are dried
7. concentrationconcentrated
8. washeluting with a mixture of diethyl ether and pentane (1:4 v/v)