N-bromobutanimide → 4-bromo-3-{4H,5H,6H-cyclopenta[b]thiophen-2-yl}-1-methyl-1H-pyrazole-5-carbaldehyde
Reaction equation
[S:1]1[C:5]([C:6]2[CH:10]=[C:9]([CH:11](OCC)[O:12]CC)[N:8]([CH3:18])[N:7]=2)=[CH:4][C:3]2[CH2:19][CH2:20][CH2:21][C:2]1=2.[Br:22]N1C(=O)CCC1=O>C(#N)C>[Br:22][C:10]1[C:6]([C:5]2[S:1][C:2]3[CH2:21][CH2:20][CH2:19][C:3]=3[CH:4]=2)=[N:7][N:8]([CH3:18])[C:9]=1[CH:11]=[O:12]Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Procedure
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%).