[N+:1]([C:4]1[O:8][C:7]([C:9]2[C:13]([CH:14]=[O:15])=[CH:12][NH:11][N:10]=2)=[CH:6][CH:5]=1)([O-:3])=[O:2].[H-].[Na+].[CH:18](Br)([CH3:20])[CH3:19].C(O)(=O)C>CN(C)C=O.O>[CH:18]([N:11]1[CH:12]=[C:13]([CH:14]=[O:15])[C:9]([C:7]2[O:8][C:4]([N+:1]([O-:3])=[O:2])=[CH:5][CH:6]=2)=[N:10]1)([CH3:20])[CH3:19]
Add 10 g of 3-(5-nitro-2-furyl)-1H-pyrazole-4-carboxaldehyde to a suspension of 1.6 g of 80% sodium hydride in 100 ml of dimethylformamide under nitrogen at 10° to 20° C. Add 7.1 g of isopropyl bromide to the resulting admixture and then stir it for 4 hours at 40° C and 7 hours at 50° C. Mix 0.8 ml of glacial acetic acid therein to obtain (after addition to 190 g of ice and water) 8.9 g of product. Recrystallize three times from dimethylformamide and water to obtain 1-isopropyl-3-(5-nitro-2-furyl)pyrazole-4-carboxaldehyde [m.p. 168.5° to 170.5° C]. Evaporate the mother liquor and chromatograph the residue to obtain 1-isopropyl-5-(5-nitro-2-furyl)pyrazole-4-carboxaldehyde.
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