Sodium Hydroxide → 4-(4-chloro-1-methyl-1H-pyrazol-5-yl)-5-methyl-2-thiophenecarboxylic acid

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Reaction Steps

A solution of methyl 5-methyl-4-(1-methyl-1H-pyrazol-5-yl)-2-thiophenecarboxylate (2.75 g, 11.64 mmol) [Prepared in Example 99] and N-chlorosuccinimide (1.55 g, 11.64 mmol) in tetrahydrofuran (58 ml) was stirred in a sealed tube for 1 h at 70° C. Sodium hydroxide (9.70 ml, 58 mmol) was added in one portion and the solution stirred an additional 1 h. The reaction mixture was then partitioned between H2O-DCM and the pH of the aqueous phase was adjusted to 4 and washed several times with DCM. The combined organic fractions were dried over Na2SO4, concentrated then purified via column chromatography (silica, 20% EtOAc in hexanes) yielding 4-(4-chloro-1-methyl-1H-pyrazol-5-yl)-5-methyl-2-thiophenecarboxylic acid (2.3 g, 8.96 mmol, 77% yield) as a yellow oil: LCMS (ES) m/e 257, 259 (M, M+2)+.

Provenance & Evidence