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20th November 2011 @ 05:35
Paal-Knorr Synthesis of 2,5-dimethyl -1H-(p-trifluoromethyl)phenyl-pyrrole



2,5-hexanedione (5 mL, 42.6 mmols, 1 equiv.) and 4-(trifluoromethyl)aniline (6 mL, 46.9 mmols, 1.1 equiv.) were mixed and heated in an oil bath at 80 °C. TLC at 7 hours shows indicated reaction at completion. Reaction was removed from heat source and allowed to cool in a refrigerator overnight. The brown crystalline solid was dissolved in EtOH (25 mL), heating gently. Solution was cooled in an ice bath with fine crystals precipitating out of solution. Solution was filtered and filter cake washed with citric acid (3 × 10mL) and water (3 × 10 mL) to produce a wet paste (8.8 g). Product was dried overnight under vacuum to produce a red-brown fine grain substance (6.08g, 60%).

Collected data: 2,5-dimethyl -1H-(p-trifluoromethyl)phenyl-pyrrole

mpt: 70-73oC
1H-NMR (300 MHz, CDCl3): δ 7.75, 7.72 (d, 2H), 7.35, 7.32 (d, 2H), 5.93 (s, 2H), 2.05 (s, 6H)
13C-NMR (75 MHz, CDCl3): δ 142.26, 130.01, 128.62, 126.32, 125.75, 122.14, 106.63, 13.04
m/z (APCI+): 241 [M+H]+, 100%
IR: 607.31, 704.64, 758.81, 849.88, 1064.45, 1127.92, 1324.97, 1402.09, 1614.82, 2923.93, 3832.68

For data files, refer to Paal Knorr Synthesis of 2,5-dimethyl-1-[p-(trifluoromethyl)phenyl]-1-H-pyrrole (LMW 3-1)

References:
doi: 10.1002/cmdc.200600026
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