83% |
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To a stirred solution of 5-nitrofurfural (2g) (0.449 g, 3.18 mmol) in 80% formic acid (3.5 mL) were added p-toluenesulfinic acid (0.497 g, 3.18 mmol) and 80% formic acid (3.5 mL), and the resulting mixture was stirred at room temperature for 15 min. To the obtained solution semicarbazone of 5-nitrofurfural [(E)-1g] (0.504 g, 2.54 mmol) and 80% formic acid (5.4 mL) were added, and the reaction mixture was stirred at room temperature for 24 h. The suspension was cooled, the precipitate was filtered, washed with cold EtOH, ice-cold H2O, petroleum ether, and dried to give sulfone (E)-4g (1.009 g, 83%) as a yellow solid. The crude product was obtained in analytically pure form. Mp 135.5-136 C (decomp); IR (Nujol) nmax 3397 (s), 3156 (m), 3135 (s), 3093 (br s) (NH), 1693 (vs) (amide-I), 1592 (s), 1578 (m), 1537 (s), 1510 (s), 1498 (vs) (C]N, amide-II,NO2, CCarom), 1353 (vs), 1341 (vs) (NO2), 1140 (s) (SO2), 813 (s)(CHarom in Ts) cm-1; 1H NMR (300.13 MHz, DMSO-d6) d 11.23 (br s,1H, NHeN), 8.03 (d, 3J 10.5 Hz, 1H, NH), 7.90 (s, 1H, CH]N), 7.82 (d, 3J 4.0 Hz, 1H, H-4 in furan moiety), 7.71-7.77 (m, 2H, ArH), 7.74(d, 3J 3.8 Hz, 1H, H-4 in furan moiety), 7.43-7.49 (m, 2H, ArH), 7.28 (d, 3J 4.0 Hz, 1H, H-3 in furan moiety), 7.20 (d, 3J 3.8 Hz, 1H,H-3 in furan moiety), 6.65 (d, 3J 10.5 Hz, 1H, CHeN), 2.41 (s, 3H,CH3); 13C NMR (75.48 MHz, DMSO-d6) d 152.8 (C]O), 152.0 (C),151.8 (C), 151.7 (C), 148.0 (C), 145.7 (C), 132.8 (C), 130.8 (CH]N),130.0 (2CH), 129.2 (2CH), 116.1 (CH), 114.9 (CH), 114.3 (CH), 113.6(CH), 67.8 (CHeN), 21.2 (CH3). Anal. Calcd for C18H15N5O9S: C, 45.29;H, 3.17; N, 14.67. Found: C, 45.44; H, 3.19; N, 14.70. |