General Papers ARKIVOC 2008 (xi) 64-74
Experimental Section
General Procedures. All chemicals were purchased from Merck or Fluka chemical companies. Silica gel 60, 0.063-0.200 mm (70-230 mesh ASTM) was used as support. All known compounds were identified by comparison of their melting points and 1H NMR data with the authentic samples. The 1H NMR (250 MHz) spectra were run on a Bruker Avanced DPX-250, FT-NMR spectrometer. Mass spectra were recorded on a Shimadzu GC MS-QP 1000 EX apparatus. Microanalyses were performed on a Perkin-Elmer 240-B microanalyzer. Melting points were recorded on a Büchi B-545 apparatus in open capillary tubes.
Preparation of P2O5/SiO2 catalytic system. A mixture of SiO2 (2 g) and P2O5 (1 mmol, 0.142 g) was ground vigorously to give P2O5/SiO2 catalytic system as a white powder (2.142 g).
Condensation of sulfonamides with aldehydes under solvent-free conditions. To a well ground mixture of sulfonamide (1 mmol) and P2O5/SiO2 (0.536 g) in a 10 mL round-bottomed flask connected to a reflux condenser was added aldehyde (1.1 mmol). The mixture was stirred in an oil-bath (110 °C) for the times reported in Table 4. Afterward, the reaction mixture was cooled to room temperature and the solid mixture was poured on a Celite pad and washed with acetone (20 mL). The solvent was evaporated and the crude product was dissolved in warm ethyl acetate (2 mL), treated with n-hexane (6 mL), and was allowed to stand at room temperature for 5-6 h. During this time, the target molecules were produced and then collected by filtration, washed with n-hexane and dried. (E)-N-Benzylidene-4-methylbenzenesulfonamide (3a). Colorless solid; yield: 0.237 g (91%); mp 108-109 °C (Lit.9a mp 108 °C); 1H NMR (CDCl3): d 2.33 (3H, s), 7.25 (2H, d, J = 8.2 Hz),
7.48 (2H, t, J = 7.8 Hz), 7.51 (1H, t, J = 6.2 Hz), 7.80-7.84 (4H, m), 8.99 (1H, s). (E)-N-(4-Isoperopyl-benzylidene)-4-methylbenzenesulfonamide (3b). Colorless solid; yield: 0.278 g (92%); mp 110-112 °C (Lit.28 mp 113-115 °C); 1H NMR (CDCl3): d 1.20 (6H, d, J = 7 Hz), 2.33 (3H, s), 2.93 (1H, m), 7.18-7.80 (8H, m), 8.91 (1H, s). (E)-N-(4-Methoxy-benzylidene)-4-methylbenzenesulfonamide (3c). Colorless solid; yield: 0.260 g (90%); mp 127-129 °C (Lit.11 mp 128-129 °C); 1H NMR (CDCl3): d 2.36 (3H, s), 3.78 (3H, s), 6.93 (2H, d, J = 8.5 Hz), 7.29 (2H, d, J = 7.8 Hz), 7.81 (2H, d, J = 7.5 Hz), 7.85 (2H, d, J = 7.6 Hz), 8.90 (1H, s). (E)-N-(2,5-Dimethoxy-benzylidene)-4-methylbenzenesulfonamide (3d). Colorless solid; yield: 0.277 g (87%); mp 125-127 °C (Lit.9a mp 124-126 °C); 1H NMR (DMSO-d6): d 2.39 (3H, s), 3.69 (3H, s), 3.93 (3H, s), 7.14-7.82 (7H, m), 9.30 (1H, s). (E)-N-(4-Nitro-benzylidene)-4-methylbenzenesulfonamide (3e). Yellow solid; yield: 0.250 g (82%); mp 164-166 °C (Lit.29 mp 162-164 °C); 1H NMR (CDCl3): d 2.39 (3H, s), 7.29 (2H, d, J = 7.8 Hz), 7.78 (2H, d, J = 7.8 Hz), 7.95 (2H, d, J = 8.5 Hz), 8.16 (2H, d, J = 8.5 Hz), 9.17 (1H, s). ISSN 1551-7012 Page 70 ©ARKAT USA, Inc.
