N-bromobutanimide → 4-bromo-3-{4H,5H,6H-cyclopenta[b]thiophen-2-yl}-1-methyl-1H-pyrazole-5-carbaldehyde

Participants

Reaction Steps

A solution of 3-{4H,5H,6H-cyclopenta[b]thiophen-2-yl}-5-(diethoxymethyl)-1-methyl-1H-pyrazole (37a) (1.69 g, 5.51 mmol) and N-bromosuccinimide (0.88 g, 4.96 mmol) in acetonitrile (10 mL) was stirred at room temperature for 4 hours. The reaction mixture was concentrated in vacuo. Water (10 mL) was added and the aqueous layer was extracted with ethyl acetate (2×10 mL). The organic layer was dried over sodium sulfate and concentrated in vacuo. The residue was purified by flash chromatography on silica gel (cyclohexane/ethyl acetate 100/0 to 95/5) to provide 4-bromo-3-{4H,5H,6H-cyclopenta[b]thiophen-2-yl}-1-methyl-1H-pyrazole-5-carbaldehyde (37b) (586 mg, 1.88 mmol, 34%).

Provenance & Evidence