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Abstract
A synthesis of novel hybrid molecules containing thiazole or bis(thiazoles) each bearing benzofuran and/or benzo[d]thiazole moieties by the reaction of the appropriate thioamide derivatives with the corresponding bis-bromoacetyl derivatives is reported. Mono- and bis(triazolothiadiazine) derivatives based on benzofuran or benzo[d]thiazole moieties were also synthesized in good yields by the reaction of the appropriate bis(bromoacetyl) derivatives with each of 4-amino-5-mercapto-1,2,4-triazoles and their corresponding bis-derivatives.
Graphical Abstract
Experimental
Materials and methods
Melting points were determined in open glass capillaries with a Gallenkamp apparatus. Elemental analyses were carried out at the Microanalytical Center of Cairo University, Giza, Egypt. The infrared spectra were recorded as potassium bromide disks on a Pye Unicam SP 3-300 and Shimaduz FTIR 8101 PC infrared spectrophotometer. NMR spectra were recorded with a Varian Mercury VXR-300 NMR spectrometer operating at 300 MHz (1H NMR) and 75 MHz (13C NMR), a Varian VXR spectrometer operating at 400 MHz (1H NMR) and 101 MHz (13C NMR) and a Varian VXR spectrometer operating at 500 MHz (1H NMR) and 126 MHz (13C NMR). Mass spectra (EI) were obtained at 70 eV with a type Shimadzu GCMQP 1000 EX spectrometer. Analytical thin-layer chromatography was performed using pre-coated silica gel 60,778 plates (Fluka), and the spots were visualized with UV light at 254 nm. Acetyl derivatives 1a,b,[Citation70] bromoacetyl derivatives 2a,b,[Citation70] bis(acetophenones) 9a–c,[Citation53] bis(α-bromoketones) 10a–c,[Citation53] bis(thiosemicarbazones) 12a–c,[Citation62] 4-amino-3-mercapto-1,2,4-triazole 14a,b[Citation79,Citation80] and bis(4-amino-5-mercapto-1,2,4-triazoles) 16a–d[Citation81] were prepared according to the literature procedures.
Synthesis and characterization data for selected compounds
Synthesis of 2-(2-(2-(1-(benzo[d]thiazol-2-yl)ethylidene)hydrazinyl)thiazol-4-yl)benzo[d]thiazole (5)
A mixture of 1-(benzo[d]thiazol-2-yl)-2-bromoethanone (2a) (1 mmol) and 2-(1-(benzo[d]thiazol-2-yl)ethylidene)hydrazinecarbothioamide (4a) (1 mmol) was dissolved in ethanol (20 mL) containing TEA (1 mL). The reaction mixture was heated at reflux for 3 h. The solid obtained upon cooling was filtered off and recrystallized from DMF/EtOH to afford the title compounds 5 as green powder (76% yield), mp. 268–270 °C; IR: (potassium bromide) 3525 (NH), 1566 (C=N) cm−1; 1H NMR (300 MHz, DMSO) δ 2.48 (s, 3H, CH3), 7.43–7.55 (m, 4H, ArH), 7.91 (s, 1H, thiazole-5-H), 8.00–8.13 (m, 4H, ArH), 12.26 (s, 1H, NH); 13C NMR (101 MHz, DMSO) δ 13.85, 111.57, 122.62, 122.79, 123.06, 123.50, 125.70, 126.49, 126.77, 127.00, 135.00, 135.35, 143.73, 145.48, 153.56, 154.00, 162.83, 168.03, 169.53; ms: m/z (%) 407 (M+). Anal. Calcd. for C19H13N5S3: C, 56.00; H, 3.22; N, 17.18; S, 23.60. Found: C, 55.76; H, 3.14; N, 17.09; S, 23.70%.
Synthesis of 4-(benzofuran-2-yl)-2-(2-(1-(benzofuran-2-yl)ethylidene)hydrazinyl)-thiazole (6)
A mixture of 1-(benzofuran-2-yl)-2-bromoethanone (2b) (1 mmol) and 2-(1-(benzofuran-2-yl)ethylidene)hydrazinecarbothioamide (4b) (1 mmol) was dissolved in ethanol (20 mL) containing TEA (1 mL). The reaction mixture was heated at reflux for 3 h. The obtained solid product was filtered off and recrystallized from DMF/EtOH to afford the title compounds 6 as brown powder (71% yield), mp. 249–251 °C; IR: (potassium bromide) 3325 (NH), 1543 (C=N) cm−1; 1H NMR (300 MHz, DMSO) δ 2.34 (s, 3H, CH3), 7.07 (s, 2H, benzofuran-3-H), 7.26 (s, 1H, thiazole-5-H), 7.43–7.49 (m, 4H, ArH), 7.57–7.88 (m, 4H, ArH),11.70 (s, 1H, NH); 13C NMR (126 MHz, DMSO) δ 14.21, 102.22, 105.80, 108.62, 113.44, 113.72, 115.96, 116.01, 124.22, 124.28, 127.57, 128.33, 130.88, 131.27, 153.37, 153.77, 155.33, 170.22; ms: m/z (%) 373 (M+). Anal. Calcd. for C21H15N3O2S: C, 67.54; H, 4.05; N, 11.25; S, 8.59. Found: C, 67.27; H, 3.89; N, 11.06; S, 8.33%.
Synthesis of 2-(2-(2-(1-(benzofuran-2-yl)ethylidene)hydrazinyl)thiazol-4-yl)benzo-[d]thiazole (7)
A mixture of 1-(benzo[d]thiazol-2-yl)-2-bromoethanone (2a) (1 mmol) and 2-(1-(benzofuran-2-yl)ethylidene)hydrazinecarbothioamide (4b) (1 mmol) was dissolved in ethanol (20 mL) containing TEA (1 mL). The reaction mixture was heated at refluxed for 3 h. The solid product which formed was filtered off and recrystallized from DMF/EtOH to afford the title compounds 7 as dark Green powder (73% yield), mp. 228–230 °C; IR: (potassium bromide) 3433 (NH), 1558 (C=N) cm−1; 1H NMR (300 MHz, DMSO) δ 2.36 (s, 3H, CH3), 7.27 (s, 1H, thiazole-5-H), 7.45–7.62 (m, 5 H, ArH & benzofuran-3-H), 7.84 (d, 2H, ArH, J = 7.5), 8.01 (d, 1H, ArH, J = 8.1), 8.10 (d, 1H, ArH, J = 7.8), 11.79 (s, 1H, NH); 13C NMR (101 MHz, DMSO) δ 14.30, 105.96, 110.92, 113.73, 116.03, 122.77, 123.03, 124.30, 125.65, 126.97, 128.38, 130.85, 135.00, 139.15, 145.32, 153.79, 154.02, 155.24, 163.00, 170.06; ms: m/z (%) 390 (M+). Anal. Calcd. for C20H14N4OS2: C, 61.52; H, 3.61; N, 14.35; S, 16.42. Found: C, 61.25; H, 3.53; N, 13.76; S, 16.30%.
Synthesis of 2-(1-(2-(4-(benzofuran-2-yl)thiazol-2-yl)hydrazono)ethyl)benzo[d]-thiazole (8)
A mixture of 1-(benzofuran-2-yl)-2-bromoethanone (2b) (1 mmol) and 2-(1-(benzo[d]thiazol-2-yl)ethylidene)hydrazinecarbothioamide (4a) (1 mmol) was dissolved in ethanol (20 mL), containing TEA (1 mL). The reaction mixture was heated at reflux for 3 h. The solid product which formed was filtered off and recrystallized from DMF/EtOH to afford the title compounds 8 as brown powder (70% yield), mp. 248–250 °C; IR: (potassium bromide) 3425 (NH), 1558 (C=N) cm−1; 1H NMR (300 MHz, DMSO) δ 2.45 (s, 3H, CH3), 7.10 (s, 1H, benzofuran-3-H), 7.45–7.61 (m, 5 H, ArH & thiazole-5-H), 7.89–8.09 (m, 4H, ArH), 12.20 (s, 1H, NH); ms: m/z (%) 390 (M+). Anal. Calcd. for C20H14N4OS2: C, 61.52; H, 3.61; N, 14.35; S, 16.42. Found: C, 60.98; H, 3.41; N, 14.29; S, 16.33%.