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14th November 2013 @ 17:58
4-(2,5-dimethyl-1H-pyrrol-1-yl)benzenesulfonamide: Sulfanilamide (1.72 g, 10 mmol), 2,5-hexanedione (1.4 mL, 12 mmol) and sulfamic acid (50 mg, 0.5 mmol, 5 mol%) combined in capped tube and heated to 130 °C overnight. Solid recrystallized from hot ethanol to give a beige powder. 1H NMR (400 MHz, CDCl3): 8.04 (d, 2H), 7.37 (d, 2H), 5.93 (s, 2H), 5.25 (br s, 2H), 2.05 (s, 6H).  4-(3-formyl-2,5-dimethyl-1H-pyrrol-1-yl)benzenesulfonamide: Cold DMF (0.8mL) was stirred in an ice bath under nitrogen atmosphere. Phosphoryl chloride (0.19mL, 1.54mmol, 1.2 equiv.) was added dropwise and reaction was stirred for 25 minutes. A solution of 4-(2,5-dimethyl-1H-pyrrol-1-yl)benzenesulfonamide (0.32g, 1.28 mmol, 1.0 equiv) and DMF (0.8mL) was added dropwise over five minutes, then brought to rt until complete (30 min; monitored with TLC). Poured over ice (16mL) and stirred until melted. Reaction pH was 1. Reaction was neutralized with NaOH (3.4mL, 10%NaOH) until it held a pH of 6. Reaction was filtered using vacuum filtration, and was rinsed with cold clean water; yielded a sandy-brown powder (0.191g). Recrystallization in acetonitrile gave similar brown solid (0.105g, 33%). Melting point: 202.6-206.7°C; IR: peaks not labeled, however, spectra showed benzene ring, carbonyl peak, the presence of single and double carbon-carbon bonds, and amine; 1H NMR (400 MHz, CDCl3): 9.89 (s, 1H), 8.07 (d, 2H), 7.32 (d, 2H), 6.41 (s, 1H), 3.19 (s, 2H), 3.10 (s, 2H), 2.3 (m, 3H), 2.01 (m, 3H). Knoevenagel Condensation: (Z)-2-((3-phenyl)imino)thiazolidin-4-one (0.078 g, 0.375 mmol) was dissolved in ethanol (7 mL) at rt. Piperidine (0.06 mL, 0.5625 mmol) and 2,5-dimethyl-N-phenyl(4-sulfamine)-pyrrole-3-carbaldehyde (0.10 g, .0375 mmol) were added. Solution refluxed overnight at 60°C and cooled to rt. Vacuum filtration (ethanol) afforded brown solid crystals (0.0696 g, 67%). MP: Decomposed at 250.4°C. IR: 3401, 3094, 3054, 2943, 2744, 1628, 1590, 1537, 1497 cm-1. 1H NMR (400 MHz, CDCl3) δ 9.884 (s, 1H), 8.198-8.016 (m, 2H), 7.284-7.141 (m, 8H), 3.193-3.085 (d, 2H). Spectrum retaken in DMSO-d6 at 50 C (attached), and was much cleaner.
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