Dimethyl Sulfoxide → methyl 1-(2-oxoethyl)-1H-indazole-7-carboxylate

Participants

Reaction Conditions

Reaction Steps

Oxalyl chloride (1.3 mL, 15.5 mmol) was added dropwise to a mixture of dimethyl sulfoxide (1.8 mL, 25.8 mmol) and methylene chloride (4 mL) at −78° C. After addition was complete, the mixture was stirred at −78° C. for 30 min. A solution of methyl 1-(2-hydroxyethyl)-1H-indazole-7-carboxylate (2.8 g, 12.9 mmol) from Step D above in methylene chloride (40 mL) and added dropwise while maintaining the temperature at −78° C. The reaction was then stirred at −78° C. for 1-2 h. The reaction was quenched with N,N-diisopropylethylamine, cooled to 0° C., and sat. NaHCO3 was added. The aqueous phase was extracted several times with methylene chloride and the combined organic layers were dried (Na2SO4), filtered and concentrated to give methyl 1-(2-oxoethyl)-1H-indazole-7-carboxylate as a yellow oil (3.8 g, crude): 1H NMR (300 MHz, CDCl3) δ 9.79 (s, 1H), 8.16 (s, 1H), 8.14-8.08 (m, 2H), 7.98 (d, J=7.5 Hz, 1H), 5.61 (s, 2H), 3.99 (s, 3H); MS (ESI+) m/z 219 (M+H).

Provenance & Evidence