All the chemicals and solvents used in studies were of GR grade, dried Selleckchem MS-275 and purified before use. The purification of synthesized compounds was performed by recrystallization with appropriate solvent system. Melting points of the synthesized compounds were determined by open capillary method and are uncorrected. The purity of the compounds was checked using precoated TLC plates (MERCK, 60F) using ethyl acetate: hexane (8:2) solvent system. The developed chromatographic plates were visualized under UV at 254 nm. IR spectra were recorded using KBr with FTIR Shimadzu IRPrestige-21 model Spectrum One Spectrophotometer, 1H NMR,
13C NMR spectra were recorded using DMSO/CDCl3 with Varian-300 spectrometer NMR instrument using TMS as internal standard.
Mass spectra were recorded in Agilent 6520 Accurate-Mass Q-TOF LC/MS. Preparation for diazonium salt of aniline was carried out as per reported procedure.17 Synthesis of formazans – cold diazotized solution was added drop wise to a well cooled (0–5 °C) stirring mixture of Schiff bases of 3,4-dimethyl-1H-pyrrole-2-carbohydrazide (0.01 M) and dry pyridine (10 mL). The reaction mixture was stirred in ice-bath for 1 h and then poured into ice water. The dark colored solid formed was collected by filtration, washed with water till it was free from pyridine and dried. The product was crystallized from ethanol (2a–j). Yellow powder, yield: 86%; mp: 304–306 °C; IR (KBr,
cm−1): 3320 (N–H), 2990 (Ar–CH), Trichostatin A research buy 1700 (C O), 1570 (C N), 1550 (N N); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 1.55 (S, 3H, CH3), 2.43–2.46 (d, 3H, CH3), 7.25 (s, 2H, ArH), 7.40–7.54 (m, 5H, ArH), 7.80–7.92 (m, 4H, ArH), 9.14 (s, 1H, Pyrrolic NH), 11.42 (s, 1H, CONH); 13C NMR (75 MHz, DMSO-d6) δ (ppm): 8.5, 10.1, 121.3, 122.8, 127.6, 129.1, 129.8, 130.4, 135.8, 152.5, 158.1; MS (ESI) m/z: 346.17 [M + H]+. Yellow powder, yield: 90%; mp: 312–314 °C; IR (KBr, cm−1): 3250 (N–H), 2990 (Ar–CH), however 1720 (C O), 1560 (C N), 1520 (N N), 2790 (OCH3); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 2.31–2.34 (d, 6H, CH3), 3.81 (s, 3H, OCH3), 7.02–7.05 (d, 2H, ArH), 7.46–7.84 (m, 7H, ArH), 8.24 (s, 1H, Pyrrolic ArH), 11.58 (s, 2H, Pyrrolic NH & CONH); 13C NMR (75 MHz, DMSO-d6) δ (ppm): 8.5, 10.0, 55.2, 114.3, 121.6, 126.2, 127.0, 128.6, 129.4, 129.9, 132, 152.7, 157.0, 160.8; MS (ESI) m/z: 376.19 [M + H]+. Yellow powder, yield: 88%; mp: 314–316 °C; IR (KBr, cm−1): 3350 (N–H), 2990 (Ar–CH), 1700 (C O), 1590 (C N), 1560 (N N), 750 (C–Cl); 1H NMR (300 MHz, DMSO-d6) δ (ppm): 2.31–2.49 (d, 6H, CH3), 7.40–7.58 (m, 6H, ArH), 7.82–7.85 (d, 2H, ArH), 8.01–8.04 (t, 1H, ArH), 8.63 (s, 1H, Pyrrolic ArH), 11.56 (s, 1H, pyrrolic NH), 11.89 (s, 1H, CONH); 13C NMR (75 MHz, DMSO-d6) δ (ppm): 8.5, 10.1, 121.6, 123.4, 125.