Carbon Dioxide → 1-methyl-3-[(1-methylpiperidin-4-yl)thio]-1H-indole-5-carboxylic acid

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Reaction Steps

A solution of 5-bromo-1-methyl-3-[(1-methylpiperidin-4-yl)thio]-1H-indole (19 g, prepared in Example 58) in THF (100 ml) is treated at -78° C. with a solution of butyllithium (31.5 ml, 2.5M in hexane). After 1 hour at this temperature, carbon dioxide is passed into the solution until it is saturated. After one hour, the reaction mixture is left to return to room temperature. The solvent is evaporated off and the residue is taken up with ether to give 1-methyl-3-[(1-methylpiperidin-4-yl)thio]-1H-indole-5-carboxylic acid (22.8 g) in the form of a yellow solid, which is used for the next step without purification.

Provenance & Evidence