3.1. General Procedures

Chemical reagents and solvents were procured from S D Fine or Sigma Aldrich suppliers in India. Thin layer chromatography (TLC) was used to monitor the reaction at each step and TLC was carried out on Merck pre-coated Silica Gel 60 F254 by using mixture of suitable mobile phase. Melting point of the intermediates and final compounds were obtained from VEEGO, MODEL: VMP-DS Melting Point apparatus by open capillary method and are uncorrected. Purity of all the final products were confirmed by Agilent 1200 high-performance liquid chromatography (HPLC) system; software—EZ chrome Elite; chromatographic column—HemochromIntsil A31 C18 5U 150 mm × 4.6 mm Sn-B180127; detection at 300 nm; detector—UV-visible; flow rate—1 mL/min; oven temperature—30 °C; gradient elution run time—10 min; mobile phase—methanol: formic Acid (1%) (formic acid: in 1000 mL double distilled water 1 mL formic acid was added) in 80:20/90:10 ratio. The structures of intermediates were confirmed by FTIR and ¹H-NMR and that of the final compounds by FTIR, ¹H-NMR, ¹³C-NMR and Mass spectrometry. FTIR was recorded on Schimadzu FT/IR-8400S by direct sampling technique. ¹H-NMR spectra were recorded by Bruker Avance 400 MHz spectrometer with DMSO-d₆. All shifts are reported in δ (ppm) units relative to the signals for solvent DMSO (δ- 2.50 ppm). All coupling constants (J values) are reported in hertz (Hz). NMR abbreviations are: bs, broad singlet; s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet; and dd, doublet of doublets. ¹³C-NMR was recorded on Bruker Avance spectrometer at 100 MHz with DMSO-d₆. Mass spectrum was determined on LC-MS Agilent Technologies 1260 Infinity instrument.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(6-nitrobenzo[d]thiazol-2-yl) acetamide (PB1). Yield 0.6 g (53%). M.P. 250 °C (charred). White color solid. IR (cm⁻¹) 3340 (NH str.), 1739 (C=O str. of cyclic amide), 1658, 1612, 1573, 1548 (C=C str¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.68 (s, 2H), 7.31–7.35 (m, 1H), 7.46–7.49 (m, 1H), 7.55–7.57 (m, 1H), 7.92–8.00 (m, 3H), 8.04 (s, 1H), 8.81 (d, J = 4.4 Hz, 1H), 13.27 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.41, 166.40, 165.89, 162.76, 159.00, 151.56, 149.86, 145.84, 138.17, 133.56, 130.17, 128.57, 126.82, 125.70, 125.18, 125.05, 124.80, 121.48, 43.34, 36.25. Theoretical mass: 441.44; LCMS (m/z, I%): 440.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.55, Retention Time 6.32 min.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(4-methylbenzo[d]thiazol-2-yl)acetamide (PB2). Yield 0.5 g (46%). M.P. 260 °C (charred). White color solid. IR (cm⁻¹) 3323 (NH str.), 1737 (C=O str. of cyclic amide), 1656, 1614, 1595, 1554 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.59 (s, 3H), 4.68 (s, 2H), 7.20–7.28 (m, 2H), 7.46–7.49 (m, 1H), 7.80 (d, J = 7.6 Hz, 1H), 7.92–8.00 (m, 2H), 8.04 (s, 1H), 8.80 (d, J = 4.4 Hz, 1H), 12.95 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.41, 165.95, 156.96, 151.55, 149.86, 148.03, 138.16, 131.63, 130.55, 130.15, 128.57, 127.21, 125.72, 124.79, 124.26, 119.67, 43.41, 18.38. Theoretical mass: 410.47; LCMS (m/z, I%): 409.1 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.11, Retention Time 5.96 min.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(6-methylbenzo[d]thiazol-2-yl)acetamide (PB3). Yield 0.7 g (67%). M.P. charred at 300 °C. White color solid. IR (cm⁻¹) 3323 (NH str.), 1730 (C=O str. of cyclic amide), 1693, 1664, 1616, 1546 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.40 (s, 3H), 4.68 (s, 2H), 7.24–7.27 (m, 1H), 7.44–7.47 (m, 1H), 7.65 (d, J = 8.4 Hz, 1H), 7.75 (s, 1H), 7.91 (d, J = 7.6 Hz, 1H), 7.94–8.02 (m, 1H), 8.03 (s, 1H), 8.79 (d, J = 4.4 Hz, 1H), 12.78 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.42, 165.91, 156.96, 151.54, 149.84, 146.93, 138.12, 133.80, 132.09, 130.51, 130.13, 128.54, 128.04, 125.71, 124.76, 121.86, 120.86, 43.45, 21.44. Theoretical mass: 410.47; LCMS (m/z, I%): 409.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.25, Retention Time 5.56 min.

N-(4-chlorobenzo[d]thiazol-2-yl)-2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)acetamide (PB4). Yield 0.75 g (72%). M.P. 273 °C (charred). White color solid. IR (cm⁻¹) 3342 (NH str.), 1745 (C=O str. of cyclic amide), 1680, 1631, 1604, 1573, 1548 (C=C str.) 705 (C-Cl str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.69 (s, 2H), 7.31–7.35 (m, 1H), 7.46–7.49 (m, 1H), 7.55–7.57 (m, 1H), 7.92–8.00 (m, 3H), 8.04 (s, 1H), 8.80 (d, J = 4.4 Hz, 1H), 13.26 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.41, 166.40, 165.89, 162.77, 159.00, 151.54, 149.86, 145.84, 138.17, 133.56, 130.17, 128.57, 126.82, 125.70, 125.18, 125.05, 124.80, 121.48, 43.44, 36.25, 31.24. Theoretical mass: 430.89; LCMS (m/z, I%): 428.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.60, Retention Time 4.99 min.

N-(4,6-difluorobenzo[d]thiazol-2-yl)-2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)acetamide (PB5). Yield 0.8 g (85%). M.P. 294 °C (charred). White color solid. IR (cm⁻¹) 3360 (NH str.), 1728 (C=O str. of cyclic amide), 1672, 1614, 1577, 1552 (C=C str.), 1383, 1145 (C-F str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.69 (s, 2H), 7.37–7.42 (m, 1H), 7.46–7.49 (m, 1H), 7.81–7.83 (m, 1H), 7.92–8.00 (m, 2H), 8.04 (s, 1H), 8.80 (d, J = 4.0 Hz, 1H), 13.14 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.42, 166.43, 165.89, 158.36, 157.51, 157.41, 151.53, 149.86, 138.17, 135.23, 130.17, 128.57, 125.71, 124.81, 105.22, 104.99, 102.86, 102.64, 102.57, 102.35, 43.42. Theoretical mass: 432.42; LCMS (m/z, I%): 431.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.23, Retention Time 5.96 min.

N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)acetamide (PB6). Yield 0.52 g (58%). M.P. 295 °C (charred). White color solid. IR (cm⁻¹) 3259 (NH str.), 1741 (C=O str. of cyclic amide), 1668, 1614, 1577, 1552 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.32 (d, J = 4.4 Hz, 6H), 4.66 (s, 2H), 7.48–7.57 (m, 2H), 7.72 (s, 1H), 7.94–7.98 (m, 2H), 8.04 (s, 1H), 8.80 (s, 1H), 12.75 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.42, 165.92, 165.78, 156.88, 151.56, 149.87, 147.54, 138.17, 135.45, 133.22, 130.13, 129.32, 128.57, 125.72, 124.80, 122.02, 121.56, 43.44, 20.16, 20.02. Theoretical mass: 424.50; LCMS (m/z, I%): 422.8 [(M-2H)⁺, 100%]. HPLC Purity: % Area 98.58, Retention Time 6.92 min.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(4-methoxybenzo[d]thiazol-2-yl)acetamide (PB7). Yield 0.4 g (53%). M.P. 220–222 °C. White color solid. IR (cm⁻¹) 3296 (NH str.), 1737 (C=O str. of cyclic amide), 1680, 1597, 1562 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.91 (s, 3H), 4.66 (s, 2H), 7.02 (d, J = 8.0 Hz, 1H), 7.28 (t, J = 8.0 Hz, 1H), 7.48 (t, J = 6.0 Hz, 1H), 7.54 (d, J = 8.0 Hz, 1H), 7.93–8.01 (m, 2H), 8.04 (s, 1H), 8.80 (d, J = 4.8 Hz, 1H), 12.96 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.45, 165.94, 165.88, 151.58, 149.88, 138.18, 130.09, 128.57, 125.80, 125.31, 124.80, 114.06, 108.28, 56.31, 43.45, 29.49. Theoretical mass: 426.47; LCMS (m/z, I%): 425.1 [(M-H)⁺, 100%]. HPLC Purity: % Area 98.67, Retention Time 5.52 min.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(6-ethoxybenzo[d]thiazol-2-yl)acetamide (PB8). Yield 0.57 g (55%). M.P. 230 °C (charred). White color solid. IR (cm⁻¹) 3259 (NH str.), 1737 (C=O str. of cyclic amide), 1666, 1599, 1552, 1535 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 1.32–1.36 (m, 3H), 4.03–4.08 (m, 2H), 4.67 (s, 2H), 7.01–7.04 (m, 1H), 7.45–7.48 (m, 1H), 7.55 (s, 1H), 7.65 (d, J = 8.8 Hz, 1H), 7.91–7.99 (m, 2H), 8.03 (s, 1H), 8.79 (d, J = 4.4 Hz, 1H), 12.71 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.43, 165.92, 165.75, 156.02, 155.73, 151.54, 149.84, 142.92, 138.13, 133.26, 130.13, 128.55, 125.71, 124.77, 121.81, 115.94, 105.83, 64.08, 43.40, 15.15. Theoretical mass: 440.50; LCMS (m/z, I%): 438.8 [(M-2H)⁺, 100%]. HPLC Purity: % Area 98.57, Retention Time 4.37 min.

2-(2,4-dioxo-5-(pyridin-2-ylmethylene)thiazolidin-3-yl)-N-(6-fluorobenzo[d]thiazol-2-yl)acetamide (PB9). Yield 0.64 g (60%). M.P. 265 °C (charred). White color solid. IR (cm⁻¹) 3246 (NH str.), 1732 (C=O str. of cyclic amide), 1689, 1651, 1612, 1566, 1554 (C=C str.), 1390 (C-F str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.70 (s, 2H), 7.26–7.31 (m, 1H), 7.43–7.46 (m, 1H), 7.75–7.79 (m, 1H), 7.87–7.90 (m, 2H), 7.93–7.97 (m, 1H), 8.01 (s, 1H), 8.78 (d, J = 4.4 Hz, 1H), 12.88 (s, 1H). ¹³C NMR (400 MHz, DMSO-d₆): 171.43, 166.18, 165.89, 160.43, 158.05, 157.86, 151.51, 149.81, 145.65, 138.09, 133.26, 133.15, 130.16, 128.53, 125.68, 124.74, 122.37, 122.29, 114.96, 114.71, 108.86, 108.60, 43.41. Theoretical mass: 414.43; LCMS (m/z, I%): 413.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.13, Retention Time 4.89 min.

2-(5-benzylidene-2,4-dioxo thiazolidine-3-yl)-N-(4-chlorobenzo[d]thiazol-2-yl)acetamide (GB1) Yield 0.53 g (55%); M.P. 279–295 °C. White color solid. IR (cm⁻¹) 3340 (NH str.), 1745 (C=O str. of cyclic amide), 1691, 1666, 1595, 1556 (C=C str.), 761 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.69 (s, 2H), 7.26–7.28 (m, 1H), 7.63–7.67 (m, 3H), 7.69–7.78 (m, 3H), 7.78 (s, 1H), 8.01 (s, 1H), 12.78 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 40.13, 43.54, 120.89, 120.96, 124.54, 124.68, 126.31, 129.40, 130.17, 130.83, 132.78, 133.04, 133.79, 145.31, 158.45, 165.09, 165.74, 167.04. Theoretical mass: 429.90; LCMS (m/z, I%): 428.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.63, RT 8.57 min.

N-(4-chlorobenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB2) Yield 0.6 g (58%); M.P. 292–294 °C. White color solid. IR (cm⁻¹) 3340 (NH str.), 1739 (C=O str. of cyclic amide), 1691, 1664, 1595, 1562 (C=C str.), 771 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.39 (s, 3H), 4.70 (s, 2H), 7.32–7.36 (m, 1H), 7.39–7.41 (m, 1H), 7.56–7.59 (m, 2H), 7.96 (s, 2H), 7.98–7.99 (m, 1H), 8.31 (s, 1H), 13.27 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 21.10, 30.75, 35.76, 79.12, 130.06, 130.29, 162.31; Theoretical mass: 443.93; LCMS (m/z, I%): 441.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 98.9, RT 11.41 min.

N-(4-chlorobenzo[d]thiazol-2-yl)-2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB3) Yield 0.5 g (55%); M.P. charred above 300°C. White color solid. IR (cm⁻¹) 3346 (NH str.), 1741 (C=O str. of cyclic amide), 1683, 1666, 1597, 1554 (C=C str.), 817, 771 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.34 (t, J = 8.0 Hz, 1H), 7.57 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 8.4 Hz, 2H), 7.78 (d, J = 8.4 Hz, 2H), 7.99–8.00 (m, 2H), 13.26 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 145.17, 133.21, 132.60, 132.43, 131.96, 126.35, 124.75, 124.31, 121.76, 120.98. UV Spectrum (10 ppm, λ_max—330 nm, absorbance—0.723). Theoretical mass: 464.34; LCMS (m/z, I%): 463.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 98.7, RT 4.4 min.

2-(5-(4-bromobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(4-chlorobenzo[d]thiazol-2-yl)acetamide (GB4) Yield 0.6 g (62%); M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3335 (NH str.), 1737 (C=O str. of cyclic amide), 1697, 1651, 1595, 1554 (C=C str.), 765 (C-Cl str.), 609 (C-Br str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.32–7.36 (m, 1H), 7.56–7.58 (m, 1H), 7.62–7.64 (m, 2H), 7.77–7.79 (m, 2H), 7.99–8.0 (m, 2H), 13.26 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 120.98, 121.76, 124.31, 124.75, 126.35, 131.96, 132.43, 132.60, 133.21, 145.17; Theoretical mass: 508.80; LCMS (m/z, I%): 507.8 [(M-H)⁺, 100%]. HPLC Purity: % Area 98.14, RT 9.1 min.

N-(4-chlorobenzo[d]thiazol-2-yl)-2-(5-(2,4-difluorobenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB5) Yield 0.45 g (51%). M.P. 288–289 °C. White color solid. IR (cm⁻¹) 3392 (NH str.), 1745 (C=O str. of cyclic amide), 1691, 1681, 1612, 1604, 1589, 1562 (C=C str.), 817 (C-Cl str.), 1276, 1143 (C-F str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.70 (s, 2H), 7.31–7.33 (m, 1H), 7.40 (d, J = 8.0 Hz, 1H), 7.43 (s, 1H), 7.56 (d, J = 8.0 Hz, 1H), 7.94 (d, J = 12.4 Hz, 2H), 7.99 (d, J = 8.0 Hz, 1H), 13.27 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.15, 165.19, 162.31, 145.32, 140.25, 137.57, 134.00, 133.04, 131.37, 130.51, 130.38, 127.68, 126.34, 124.72, 124.57, 120.98, 119.41, 79.12, 43.47, 19.46, 19.35. UV Spectrum (10 ppm, λ_max—328 nm, absorbance—0.442). Theoretical mass: 465.88; LCMS (m/z, I%): 463.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.02, RT 4.01 min.

N-(4-chlorobenzo[d]thiazol-2-yl)-2-(5-(3,4-dimethylbenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB6) Yield 0.61 g (65%); M.P. 214–216 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1743 (C=O str. of cyclic amide), 1687, 1668, 1597, 1564 (C=C str.), 773 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.30 (s, 6H), 4.70 (s, 2H), 7.39–7.41 (m, 1H), 7.43 (m, 1H), 7.5–7.57 (m, 1H), 7.92–7.96 (m, 3H), 7.98–8.0 (m, 1H), 13.27 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 19.46, 30.75, 35.76, 43.47, 79.12, 119.41, 120.98, 124.57, 124.72, 126.34, 127.68, 130.38, 130.51, 131.37, 133.04, 134.0, 137.57, 140.25, 145.32, 162.31, 165.19, 167.15 Theoretical mass: 457.95; LCMS (m/z, I%): 456.1 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.05, RT 5.77 min.

2-(5-(4-bromobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(4,6-difluorobenzo[d]thiazol-2-yl) acetamide (GB7) Yield 0.63 g (59%); M.P. charred above 300°C. White color solid. IR (cm⁻¹) 3275 (NH str.), 1743 (C=O str. of cyclic amide), 1691, 1660, 1608, 1573 (C=C str.), 1288, 1153 (C-F str.), 596 (C-Br str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.37–7.42 (m, 1H), 7.62 (d, J = 8.4 Hz, 2H), 7.78 (d, J = 8.4 Hz, 2H), 7.80–7.83 (m, 1H), 7.99 (s, 1H), 13.15 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 166.83, 165.68, 165.03, 132.6, 132.42, 132.0, 131.95, 124.42, 121.74, 104.43, 79.12, 43.56. UV Spectrum (10 ppm, λ_max—326 nm, absorbance—1.817). Theoretical mass: 510.33; LCMS (m/z, I%): 509.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.20, RT 4.78 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(4-methoxybenzo[d]thiazol-2-yl)acetamide (GB8) Yield 0.54 g (60%); M.P. 157–159 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1741 (C=O str. of cyclic amide), 1681, 1602, 1568 (C=C str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.93 (s, 3H), 4.68 (s, 2H), 7.01–7.03 (m, 1H), 7.27–7.31 (m, 1H), 7.52–7.60 (m, 4H), 7.67–7.69 (m, 2H), 8.02 (s, 1H), 12.97 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 55.81, 107.79, 113.56, 120.98, 124.87, 129.43, 130.19, 130.85, 132.81, 133.74, 165.17, 167.13; Theoretical mass: 425.48; LCMS (m/z, I%): 424.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.59, RT 2.98 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(4-methylbenzo[d]thiazol-2-yl)acetamide (GB9) Yield 0.59 g (55%). M.P. 272–273 °C. White color solid. IR (cm⁻¹) 3323 (NH str.), 1743, 1712 (C=O str. of cyclic amide), 1672, 1608, 1537 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.59 (s, 3H), 4.70 (s, 2H), 7.21–7.29 (m, 2H), 7.53–7.60 (m, 3H), 7.67 (d, J = 7.2 Hz, 2H), 7.80 (d, J = 7.6 Hz, 1H), 8.01 (s, 1H), 12.96 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.09, 165.14, 156.28, 147.53, 133.79, 132.79, 131.12, 130.85, 130.19, 130.09, 129.42, 126.73, 123.80, 120.90, 119.17, 43.49, 17.87. UV Spectrum (10 ppm, λ_max—326 nm, absorbance—0.929). Theoretical mass: 409.48; LCMS (m/z, I%): 408.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.73, RT 3.67 min.

2-(5-(4-fluorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(4-methylbenzo[d]thiazol-2-yl)acetamide (GB10) Yield 0.6 g (64%); M.P. 225–227 °C. White color solid. IR (cm⁻¹) 3344 (NH str.), 1741 (C=O str. of cyclic amide), 1687, 1633, 1595, 1510 (C=C str.), 1149 (C-F str.), 771 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.74 (s, 3H), 4.69 (s, 2H), 7.21–7.29 (m, 2H), 7.40–7.45 (m, 2H), 7.74–7.81 (m, 2H), 7.96 (s, 1H), 8.03 (s, 1H), 12.96 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 17.86, 30.75, 35.76, 43.52, 116.50, 116.72, 119.17, 120.60, 123.81, 126.73, 129.50, 130.09, 131.12, 132.68, 132.73, 132.77, 147.52, 161.85, 162.312, 165.10, 165.20, 165.31, 166.98; Theoretical mass: 427.47; LCMS (m/z, I%): 426.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.97, RT 3.34 min.

2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(4,6-difluorobenzo[d]thiazol-2-yl)acetamide (GB11) Yield 0.52 g (55%); M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3267 (NH str.), 1743 (C=O str. of cyclic amide), 1693, 1662, 1608, 1573 (C=C str.), 1153, 1101 (C-F str.), 729 (C-Cl str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.36–7.42 (m, 1H), 7.62–7.64 (m, 2H), 7.68–7.71 (m, 2H), 7.80–7.83 (s, 1H), 8.01 (s, 1H), 13.15 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 43.55, 102.15, 104.47, 104.74, 121.64, 129.48, 131.68, 131.82, 132.50, 135.48, 152.11, 157.78, 165.02, 165.67, 166.84; Theoretical mass: 465.88; LCMS (m/z, I%): 463.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 97.72, RT 4.40 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(4,6-difluorobenzo[d]thiazol-2-yl)acetamide (GB12) Yield 0.57 g (60%); M.P. 280–282 °C. White color solid. IR (cm⁻¹) 3335 (NH str.), 1751 (C=O str. of cyclic amide), 1685, 1626, 1595, 1579 (C=C str.), 1149, 1107 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.40–7.42 (m, 1H), 7.53–7.60 (m, 2H), 7.67–7.69 (m, 3H), 7.81–7.83 (s, 1H), 7.95 (s, 1H), 13.15 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 30.75, 35.75, 43.52, 120.89, 129.42, 130.19, 130.87, 132.78, 133.83, 162.31, 165.13, 165.68, 167.09; Theoretical mass: 431.44; LCMS (m/z, I%): 429.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 95.82, RT 3.31 min.

2-(5-(2,4-difluorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-methylbenzo[d]thiazol-2-yl)acetamide (GB13) Yield 0.65 g (68%); M.P. 266–268 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1745 (C=O str. of cyclic amide), 1685, 1604, 1585, 1548 (C=C str.), 1143, 1107 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.42 (s, 3H), 4.70 (s, 2H), 7.27–7.29 (m, 1H), 7.31–7.36 (m, 1H), 7.49–7.55 (m, 1H), 7.66–7.74 (m, 2H), 7.78 (s, 1H), 7.93 (s, 1H), 12.78 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 20.94, 79.12, 105.17, 112.99, 120.41, 121.38, 123.50, 124.24, 127.60, 130.77, 133.39, 164.84, 166.70; Theoretical mass: 445.46; LCMS (m/z, I%): 444.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.33, RT 3.7 min.

N-(6-methylbenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB14) Yield 0.49 g (56%). M.P. 268–269 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1739, 1701 (C=O str. of cyclic amide), 1660, 1593, 1546, 1512 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.39 (s, 3H), 2.41 (s, 3H), 4.69 (s, 2H), 7.28 (d, J = 8.0 Hz, 2H), 7.39 (d, J = 8.0 Hz, 2H), 7.57 (d, J = 8.0 Hz, 2H), 7.67 (d, J = 8.0 Hz, 1H), 7.78 (s, 1H), 12.78 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.11, 165.21, 146.41, 141.28, 133.87, 133.37, 131.59, 130.28, 130.05, 127.58, 121.37, 120.40, 119.64, 43.50, 21.10, 20.94. UV Spectrum (10 ppm, λ_max—331 nm, absorbance—0.543). Theoretical mass: 423.51; LCMS (m/z, I%): 422.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.87, RT 4.31 min.

2-(5-(3,4-dimethylbenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-methylbenzo[d]thiazol-2-yl) acetamide (GB15) Yield 0.62 g (65%). M.P. 285–286 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1739, 1701 (C=O str. of cyclic amide), 1658, 1593, 1548, 1502 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.30 (s, 6H), 2.41 (s, 3H), 4.68 (s, 2H), 7.28 (d, J = 8.0 Hz, 1H), 7.34 (d, J = 7.6 Hz, 1H), 7.40 (d, J = 8.0 Hz, 1H), 7.44 (s, 2H), 7.66 (d, J = 8.0 Hz, 1H), 7.78 (s, 1H), 12.78 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.16, 165.22, 146.41, 140.25, 137.58, 133.98, 133.37, 131.59, 131.37, 130.52, 130.40, 127.68, 127.59, 121.38, 120.40, 119.42, 43.48, 20.94, 19.47, 19.35. UV Spectrum (10 ppm, λ_max—334 nm, absorbance—1.079). Theoretical mass: 437.53; LCMS (m/z, I%): 436.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.08, RT 5.36 min.

2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-methylbenzo[d]thiazol-2-yl) acetamide (GB16) Yield: 0.39 g (48%). M.P. 283–284 °C. White color solid. IR (cm⁻¹) 3304 (NH str.), 1739, 1703 (C=O str. of cyclic amide), 1662, 1602, 1585 (C=C str.), 858 (C-Cl str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.39 (s, 3H), 4.70 (s, 2H), 7.34 (t, J = 8.0 Hz, 1H), 7.40 (d, J = 8.0 Hz, 1H), 7.56–7.59 (m, 2H), 7.96 (s, 1H), 7.98–7.99 (m, 1H), 8.31 (s, 1H), 13.27 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 162.31, 130.29, 130.06, 79.12, 35.76, 30.75, 21.10. UV Spectrum (10 ppm, λ_max—330 nm, absorbance—1.196). Theoretical mass: 443.93; LCMS (m/z, I%): 441.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.02, RT 5.45 min.

2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-ethoxybenzo[d]thiazol-2-yl) acetamide (GB17) Yield 0.47 g (49%). M.P. 260.5–261.5 °C. White color solid. IR (cm⁻¹) 3304 (NH str.), 1741 (C=O str. of cyclic amide), 1666, 1604, 1587, 1566, 1548 (C=C str.), 815 (C-Cl str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 1.33–1.37 (m, 3H), 4.05–4.08 (m, 2H), 4.69 (s, 2H), 7.04 (dd, J = 2.8, 8.8 Hz, 1H), 7.57 (d, J = 2.4 Hz, 1H), 7.63–7.72 (m, 5H), 8.02 (s, 1H), 12.71 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 166.84, 165.06, 155.54, 135.47, 132.47, 131.83, 131.71, 129.50, 121.67, 121.37, 115.50, 105.37, 79.12, 63.60, 43.52, 14.65. UV Spectrum (10 ppm, λ_max—329 nm, absorbance—0.622). Theoretical mass: 473.95; LCMS (m/z, I%): 472.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.63, RT 4.30 min.

N-(4,6-difluorobenzo[d]thiazol-2-yl)-2-(5-(4-fluorobenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB18) Yield 0.53 g (57%); M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1741 (C=O str. of cyclic amide), 1695, 1662, 1622, 1599 (C=C str.), 1286, 1149, 1101 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H), 7.37–7.45 (m, 3H), 7.74–7.77 (m, 2H), 7.80–7.83 (m, 1H), 8.31 (s, 1H), 13.15 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 30.75, 35.75, 43.52, 79.12, 102.09, 102.37, 104.49, 104.73, 116.50, 116.72, 120.60, 129.47, 132.68, 132.77, 157.69, 161.86, 162.30, 164.36, 165.09, 166.98; Theoretical mass: 449.43; LCMS (m/z, I%): 447.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 95.31, RT 3.34 min.

N-(4,6-difluorobenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB19) Yield 0.53 g (58%); M.P. 295–297 °C. White color solid. IR (cm⁻¹) 3348 (NH str.), 1741 (C=O str. of cyclic amide), 1664, 1624, 1575 (C=C str.), 1147, 1103 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.38 (s, 3H), 4.70 (s, 2H), 7.37–7.41 (m, 1H), 7.55–7.57 (m, 2H), 7.80–7.82 (m, 1H), 7.97 (m, 1H), 8.31 (s, 1H), 13.15 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆): 21.09, 30.74, 35.75, 43.46, 79.12, 101.85, 102.08, 102.36, 104.43, 104.70, 133.89, 134.64, 134.72, 141.28, 152.11, 154.50, 154.64, 156.92, 157.03, 157.67, 162.30, 165.18, 167.11; Theoretical mass: 445.46; LCMS (m/z, I%): 444.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.99, RT 4.19 min.

N-(4,6-difluorobenzo[d]thiazol-2-yl)-2-(5-(3,4-dimethylbenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB20) Yield 0.63 g (65%); M.P. 271–273 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1741 (C=O str. of cyclic amide), 1697, 1664, 1641, 1622 (C=C str.), 1284, 1147 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.30 (s, 6H), 4.70 (s, 2H), 7.34–7.36 (m, 1H), 7.37–7.44 (m, 2H), 7.81–7.83 (m, 1H), 7.93–7.96 (m, 2H), 13.14 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆): 19.84, 31.25, 36.26, 43.97, 79.62, 119.93, 128.18, 130.89, 131.03, 131.87, 134.51, 138.09, 140.77, 162.82, 165.70, 167.67; Theoretical mass: 459.49; LCMS (m/z, I%): 458.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.49, RT 5.21 min.

N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB21) Yield 0.52 g (53%). M.P. 283–285 °C. White color solid. IR (cm⁻¹) 3246 (NH str.), 1741 (C=O str. of cyclic amide), 1697, 1664, 1593, 1550 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.32 (d, J = 6.4 Hz, 6H), 2.39 (s, 3H), 4.67 (s, 2H), 7.39 (d, J = 8.0 Hz, 2H), 7.57 (d, J = 8.0 Hz, 3H), 7.73 (s, 1H), 7.97 (s, 1H), 12.75 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.12, 165.21, 146.95, 141.27, 133.85, 132.77, 130.28, 130.06, 121.51, 119.65, 21.10, 19.65, 19.51. UV Spectrum (10 ppm, λ_max—332 nm, absorbance—0.388). Theoretical mass: 437.53; LCMS (m/z, I%): 435.8 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.85, RT 5.47 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(5,6-dimethylbenzo[d]thiazol-2-yl)acetamide (GB22) Yield 0.57 g (60%); M.P. 276–278 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1743 (C=O str. of cyclic amide), 1666, 1597, 1548 (C=C str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.32 (d, J = 6.4 Hz, 3H), 2.39 (s, 3H), 4.67 (s, 2H), 7.39 (d, J = 8.0 Hz, 2H), 7.57 (d, J = 8.0 Hz, 3H), 7.73 (s, 2H), 7.97 (s, 1H), 12.75 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.12, 165.21, 146.95, 141.27, 133.85, 132.77, 130.28, 130.06, 121.51, 119.65, 21.10, 19.65, 19.51. Theoretical mass: 423.51; LCMS (m/z, I%): 421.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 97.41, RT 4.62 min.

2-(5-(4-bromobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(5,6-dimethylbenzo[d]thiazol-2-yl)acetamide (GB23) Yield 0.59 g (60%); M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1747 (C=O str. of cyclic amide), 1697, 1655, 1604, 1546 (C=C str.), 650 (C-Br str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 2.42 (s, 6H, CH₃), 4.70 (s, 2H, CH₂), 7.27–7.36 (m, 2H, ArH), 7.49–7.55 (m, 1H, ArH), 7.66–7.78 (m, 3H, ArH and benzylidene proton), 7.93 (s, 1H, ArH), 12.78 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 166.8, 165.0, 135.4, 133.3, 132.4, 131.8, 131.6, 129.4, 127.6, 121.6, 121.3, 120.3, 43.9, 19.9, 19.8. Theoretical mass: 502.40; LCMS (m/z, I%): 501.7 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.22, RT 5.93 min.

2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(5,6-dimethylbenzo[d]thiazol-2-yl) acetamide (GB24) Yield 0.63 g (68%). M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1745, 1701 (C=O str. of cyclic amide), 1666, 1604, 1587, 1546 (C=C str.), 854 (C-Cl str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.32 (d, J = 6.0 Hz, 6H), 4.69 (s, 2H), 7.57 (s, 1H), 7.63–7.65 (m, 2H), 7.69–7.73 (m, 3H), 8.01 (s, 1H), 12.76 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 166.84, 165.05, 135.46, 135.00, 132.78, 132.46, 131.83, 131.71, 129.50, 121.67, 121.52, 19.65, 19.52. UV Spectrum (10 ppm, λ_max—329 nm, absorbance—0.219). Theoretical mass: 457.95; LCMS (m/z, I%): 455.7 [(M-H)⁺, 90%]. HPLC Purity: % Area 95.52, RT 5.04 min.

N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-(5-(4-fluorobenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB25) Yield 0.54 g (59%); M.P. 298–299 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1745 (C=O str. of cyclic amide), 1699, 1662, 1597 (C=C str.), 1141 (C-F str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 2.32–2.33 (d, J=2 Hz, 6H, CH₃), 4.69 (s, 2H, CH₂), 7.57 (s, 1H, benzylidene proton), 7.63–7.73 (m, 5H, ArH), 8.01 (s, 1H, ArH), 12.76 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 167.3, 167.2, 155.9, 138.4, 138.3, 130.9, 130.6, 126.8, 126.1, 125.1, 121.0, 120.7, 119.6, 119.5, 111.5, 67.3, 16.0, 13.4. Theoretical mass: 441.50; LCMS (m/z, I%): 440.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.31, RT 4.0 min.

N-(5,6-dimethylbenzo[d]thiazol-2-yl)-2-(5-(3,4-dimethylbenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB26) Yield 0.59 g (60%); M.P. 284–286 °C. White color solid. IR (cm⁻¹) 3335 (NH str.), 1741 (C=O str. of cyclic amide), 1697, 1658, 1593, 1546 (C=C str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 2.74 (m, 6H, CH₃), 2.90 (m, 6H, CH₃), 4.70 (s, 2H, CH₂), 7.34–7.38 (m, 1H, ArH), 7.39–7.44 (m, 2H, ArH), 7.81–7.83 (m, 1H), 7.93–7.96 (d, J=10.8 Hz, 2H, ArH), 13.14 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 165.7, 165.6, 162.8, 140.7, 138.0, 134.5, 131.8, 131.0, 130.8, 128.1, 119.9, 79.6, 43.9, 19.9, 19.8. Theoretical mass: 451.56; LCMS (m/z, I%): 450.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 98.14, RT 6.48 min.

N-(4-methoxybenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB27) Yield 0.59 g (63%). M.P. 249–251 °C. White color solid. IR (cm⁻¹) 3342 (NH str.), 1745, 1708 (C=O str. of cyclic amide), 1687, 1631, 1599, 1566, 1514 (C=C str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.59 (s, 3H), 3.92 (s, 3H), 4.68 (s, 2H), 7.01 (d, J = 7.6 Hz, 1H), 7.28 (t, J = 8.0 Hz, 1H), 7.42 (t, J = 8.8 Hz, 2H), 7.54 (d, J = 8.0 Hz, 1H), 7.73–7.77 (m, 2H), 8.02 (s, 1H), 12.97 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.01, 165.12, 164.34, 161.85, 156.11, 151.93, 138.26, 132.82, 132.75, 132.67, 129.50, 129.46, 124.86, 120.68, 116.72, 116.50, 113.54, 107.79, 43.57. UV Spectrum (10 ppm, λ_max—322 nm, absorbance—0.473). Theoretical mass: 439.51; LCMS (m/z, I%): 438.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.65, RT 3.05 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(4-methylbenzo[d]thiazol-2-yl)acetamide (GB28) Yield 0.60 g (62%); M.P. 278–280 °C. White color solid. IR (cm⁻¹) 3321 (NH str.), 1741 (C=O str. of cyclic amide), 1693, 1666, 1599, 1548 (C=C str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.59 (s, 3H), 4.70 (s, 2H), 7.21–7.29 (m, 2H), 7.53–7.60 (m, 3H), 7.67 (d, J = 7.2 Hz, 2H), 7.80 (d, J = 7.6 Hz, 1H), 8.01 (s, 1H), 12.96 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 167.09, 165.14, 156.28, 147.53, 133.79, 132.79, 131.12, 130.85, 130.19, 130.09, 129.42, 126.73, 123.80, 120.90, 119.17, 43.49, 17.87. Theoretical mass: 409.48; LCMS (m/z, I%): 408.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.09, RT 3.46 min.

N-(4,6-difluorobenzo[d]thiazol-2-yl)-2-(5-(2,4-difluorobenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB29) Yield 0.62 g (70%); M.P. 274–276 °C. White color solid. IR (cm⁻¹) 3392 (NH str.), 1743 (C=O str. of cyclic amide), 1693, 1666, 1612, 1573 (C=C str.), 1244, 1192, 1145, 1199 (C-F str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 4.69 (s, 2H, CH₂), 7.02 (dd, J=2.8Hz, 2.4 Hz, 1H, ArH), 7.57–7.72 (m, 4H, ArH and benzylidene proton), 8.02 (s, 1H, ArH), 12.71 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 167.1, 165.2, 146.9, 141.2, 133.8, 132.7, 130.2, 130.0, 121.5, 119.6, 43.9. Theoretical mass: 467.42; LCMS (m/z, I%): 466.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.63, RT 3.62 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(4-fluorobenzo[d]thiazol-2-yl)acetamide (GB30) Yield 0.63 g (68%); M.P. 272–274 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1753 (C=O str. of cyclic amide), 1705, 1668, 1604, 1554 (C=C str.), 1147 (C-F str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 4.69 (s, 2H, CH₂), 7.21–7.29 (m, 2H, ArH), 7.40–7.45 (t, 2H, ArH), 7.74–7.81 (m, 3H, ArH and benzylidene proton), 7.96 (s, 1H, ArH), 12.96 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 166.9, 165.3, 165.2, 165.1, 162.3, 161.8, 147.5, 132.7, 132.6, 131.1, 130.0, 129.5, 126.7, 123.8, 120.6, 119.1, 116.7, 116.5, 43.5, 17.8. Theoretical mass: 413.45; LCMS (m/z, I%): 412.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.28, RT 3.05 min.

2-(5-(4-bromobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-methylbenzo[d]thiazol-2-yl)acetamide (GB31) Yield 0.62 g (65%); M.P. 292–294 °C. White color solid. IR (cm⁻¹) 3265 (NH str.), 1753 (C=O str. of cyclic amide), 1703, 1693, 1666, 1602 (C=C str.), 688 (C-Br str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 2.41 (s, 3H, CH₃), 4.69 (s, 2H, CH₂), 7.26–7.28 (m, 1H, ArH), 7.63–7.78 (m, 6H, ArH and benzylidene proton), 8.01 (s, 1H, ArH), 12.78 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 166.8, 165.6, 165.0, 132.6, 132.4, 132.0, 131.9, 124.4, 121.7, 104.4, 79.1, 43.5, 21.7. Theoretical mass: 488.38; LCMS (m/z, I%): 487.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.35, RT 4.85 min.

N-(6-fluorobenzo[d]thiazol-2-yl)-2-(5-(4-methylbenzylidene)-2,4-dioxothiazolidin-3-yl) acetamide (GB32) Yield 0.52 g (58%). M.P. 274–275 °C. White color solid. IR (cm⁻¹) 3259 (NH str.), 1737, 1703 (C=O str. of cyclic amide), 1658, 1591, 1552 (C=C str.), 1139 (C-F str.). ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 2.74 (s, 3H), 4.69 (s, 2H), 7.21–7.29 (m, 2H), 7.43 (t, J = 8.8 Hz, 2H), 7.74–7.81 (m, 2H), 7.96 (s, 1H), 8.03 (s, 1H), 12.96 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 166.98, 165.31, 165.20, 165.10, 162.31, 161.85, 147.52, 132.77, 132.73, 132.68, 131.12, 130.09, 129.50, 126.73, 123.81, 120.60, 119.17, 116.72, 116.50, 43.52, 35.76, 30.75, 17.86. UV Spectrum (10 ppm, λ_max—329 nm, absorbance—0.843). Theoretical mass: 427.47; LCMS (m/z, I%): 425.9 [(M-H)⁺, 100%]. HPLC Purity: % Area 95.94, RT 3.98 min.

2-(5-(4-chlorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(6-fluorobenzo[d]thiazol-2-yl)acetamide (GB33) Yield 0.63 g (65%); M.P. 290–292 °C. White color solid. IR (cm⁻¹) 3387 (NH str.), 1739 (C=O str. of cyclic amide), 1704, 1664, 1600, 1585 (C=C str.), 1139 (C-F str.), 705 (C-Cl str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 4.71 (s, 2H, CH₂), 7.36–7.42 (m, 1H, ArH), 7.62–7.71 (dd, J=8.4 Hz, 8.8 Hz, 2H, ArH), 7.80–7.83 (m, 4H, ArH and benzylidene proton), 8.01 (s, 1H, ArH), 12.97 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 167.1, 165.2, 146.4, 141.2, 133.8, 133.3, 131.5, 130.2, 130.0, 127.5, 121.3, 120.4, 119.6, 43.5. Theoretical mass: 447.89; LCMS (m/z, I%): 445.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 95.97, RT 3.98 min.

N-(6-fluorobenzo[d]thiazol-2-yl)-2-(5-(4-fluorobenzylidene)-2,4-dioxothiazolidin-3-yl)acetamide (GB34) Yield 0.64 g (68%); M.P. 260–262 °C. White color solid. IR (cm⁻¹) 3398 (NH str.), 1741 (C=O str. of cyclic amide), 1712, 1674, 1589, 1545 (C=C str.), 1195, 1138 (C-F str.); ¹H-NMR (400 MHz, DMSO-d₆, δ ppm): 4.68 (s, 2H, CH₂), 7.37–7.42 (m, 1H, ArH), 7.61–7.63 (d, J=8.4 Hz, 2H, ArH), 7.77–7.83 (m, 4H, ArH and benzylidene proton), 7.99 (s, 1H, ArH), 13.14 (bs, 1H, NH). ¹³C-NMR (100 MHz, DMSO-d₆): 167.1, 165.2, 146.4, 140.2, 137.5, 133.9, 133.3, 131.5, 131.3, 130.5, 130.4, 127.6, 127.5, 121.3, 120.4, 119.4, 43.4. Theoretical mass: 431.44; LCMS (m/z, I%): 430.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 97.87, RT 3.04 min.

2-(5-(4-fluorobenzylidene)-2,4-dioxothiazolidin-3-yl)-N-(4-methoxybenzo[d]thiazol-2-yl)acetamide (GB35) Yield 0.58 g (60%); M.P. 172–172 °C. White color solid. IR (cm⁻¹) 3279 (NH str.), 1743 (C=O str. of cyclic amide), 1687, 1597, 1566, 1554 (C=C str.), 1147 (C-F str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 3.92 (s, 3H), 4.68 (s, 2H), 7.01–7.02 (m, 1H), 7.26–7.30 (m, 1H), 7.40–7.44 (m, 2H), 7.53–7.55 (m, 1H), 7.73–7.77 (m, 2H), 8.02 (s, 1H), 12.97 (s, 1H); ¹³C NMR (100 MHz, DMSO-d₆): 43.57, 55.80, 79.12, 107.79, 113.54, 116.50, 116.72, 120.68, 124.86, 129.46, 129.50, 132.67, 132.75, 132.82, 138.26, 151.93, 156.11, 161.85, 164.34, 165.12, 167.01; Theoretical mass: 443.47; LCMS (m/z, I%): 441.9 [(M-2H)⁺, 100%]. HPLC Purity: % Area 96.52, RT 3.05 min.

2-(5-benzylidene-2,4-dioxothiazolidin-3-yl)-N-(6-ethoxybenzo[d]thiazol-2-yl)acetamide (GB36) Yield 0.55 g (59%); M.P. charred above 300 °C. White color solid. IR (cm⁻¹) 3265 (NH str.), 1739 (C=O str. of cyclic amide), 1695, 1666, 1599, 1550 (C=C str.); ¹H NMR (400 MHz, DMSO-d₆, δ ppm): 1.33–1.37 (m, 3H), 4.05–4.08 (m, 2H), 4.69 (s, 2H), 7.04 (dd, J = 2.8, 8.8 Hz, 1H), 7.57 (d, J = 2.4 Hz, 2H), 7.63–7.72 (m, 5H), 8.02 (s, 1H), 12.71 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆): 166.84, 165.06, 155.54, 135.47, 132.47, 131.83, 131.71, 129.50, 121.67, 121.37, 115.50, 105.37, 79.12, 63.60, 43.52, 14.65. Theoretical mass: 439.51; LCMS (m/z, I%): 438.0 [(M-H)⁺, 100%]. HPLC Purity: % Area 96.27, RT 2.94 min.