International Scholarly Research Notices
Volume 2014 (2014), Article ID 186207, 7 pages
http://dx.doi.org/10.1155/2014/186207

Research Article

An Efficient and Facile Synthesis of 1,2,4-Aryl Triazoles and 4-Thiazolidinones Bearing 6-Fluorochroman Nucleus

Piyush B. Vekariya, Jalpa R. Pandya, and Hitendra S. Joshi

Chemical Research Laboratory, Department of Chemistry, Saurashtra University, Rajkot 360005, India

Received 14 April 2014; Accepted 5 July 2014; Published 30 October 2014

Academic Editor: Xin Wang

Copyright © 2014 Piyush B. Vekariya et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

A new generation of chroman bearing heterocyclic five membered ring such as 1,2,4-triazoles and thiazolidinones was designed and synthesized. New chroman based nucleus 5-(6-fluorochroman-2-yl)-4-aryl-4H-1,2,4-triazole-3-thiol and 6-fluorochroman-N-(4-oxo-2-arylthiazolidinin-3-yl) chroman-2-carboxamides were synthesized. Aryl triazole compounds 4a–4j were synthesized from 6-fluorochroman-2-carbohydrazide 2 on reaction with base in methanol and CS₂ followed by reaction with substituted aniline. Thiazolidinone compounds 5a–5j were synthesized from 6-fluorochroman-2-carbohydrazide 2 on reaction with substituted aryl aldehyde and thioglycolic acid.

1. Introduction

The design and synthesis of hybrid molecules encompassing two pharmacophores in one molecular scaffold is a well-established approach to the synthesis of more potent drugs with dual activity. With this aspect, 6-fluorochroman-2-carboxylic acid derivatives in connection with thiazolidinone and 1, 2, 4-triazoles were found as a promising target for the current research project. 1, 2, 4-Triazoles and 4-thiazolidinones are the broadly investigated molecules. They have proved to be the most useful framework for biological activities among nitrogen containing five membered heterocycles. Amongst the diverse classes of heterocyclic compounds chroman, a class of oxygen containing heterocycle forms an important part of many pharmacologically active compounds. For example, the chroman ring is a constituent of various bioactive compounds that are sodium channel blocker [1], inhibitor [2], and so forth. Commercially available antihypertensive drugs of chroman repinotan [3], robalzotan [4], and specifically 6-fluorochroman nebivolol [5] are well known. Hence, the synthesis of 6-fluorochroman derivatives is currently of significant interest in organic synthesis.

Aryl triazoles comprise various heterocyclic compounds possessing promising biological activity and are found as potential antimicrobial [6, 7] and adenosine receptor antagonist [8]. According to the green chemistry approach there are many solvent free reactions of 1, 2, 4-aryl triazoles that have been reported [9, 10].

4-Thiazolidinones have been widely explored for their applications in the field of medicine and agriculture [11]. They are also known as promising antimicrobial [12], antiinflammatory [13, 14], antimalerial [15], anticancer [16], tuberculostatic [17], and antiviral agents [18]. Several one-pot multicomponent syntheses of 4-thiazolidinone have been reported [19–21].

2. Result and Discussion

The syntheses of triazole and thiazolidinone derivatives have been previously reported by many researchers, and they normally required additional additives and long reaction time. So in this paper, we described an efficient and safe procedure for the synthesis of 4-aryl triazole containing chroman nucleus, using 6-fluorochroman-2-carboxylic acid. 6-Fluorochroman-2-carboxylic acid on esterification with methanol in the presence of concentrated H₂SO₄ at room temperature gave compound 1 (Scheme 1) with good yield which on reaction with hydrazine hydrate (99%) gave compound 2. Compound 2 on reaction with carbon disulphide in the presence of KOH in methanol at RT afforded compound 3. This on further reaction with substituted aniline without use of any solvent in fused condition yielded compounds 4a–4j (Scheme 1). ¹H and ¹³C NMR spectra of the products clearly indicated the formation of triazoles 4a–4j in 75–95% yields (Table 1). The formation of thiol group –SH was identified by a sharp singlet at around  ppm. By the ¹³C NMR spectrum also supported the presence of –SH group from the deshielding value of carbon attached to –SH group at 168.71 ppm.

Table 1: Physical data for 4a –4j.

Entry
Substitution R
Yield (%)

4a
4-CH₃ phenyl
89

4b
3-Cl phenyl
86

4c
4-F phenyl
78

4d
2,5-Dimethyl phenyl
95

4e
3,4-Dimethyl phenyl
84

4f
2-F phenyl
79

4g
2-Cl phenyl
76

4h
3-Cl-4-F phenyl
87

4i
2-OCH3 phenyl
90

4j
2,5-Difluoro phenyl
75

Scheme 1: Reaction scheme for the synthesis of 4a–4j.

Here we introduce the one-pot synthesis of thiazolidinone from hydrazide (Scheme 2) with thioglycolic acid, substituted aryl aldehydes in toluene using a Dean-Stark assembly to synthesized compounds 5a–5j (Scheme 2). ¹H and ¹³C NMR spectra of the products clearly indicated the formation of 4-thiazolidinone 5a–5j in 71–95% yields (Table 2). The formation of –NH group was identified by a sharp singlet at around 10.46–10.43 ppm, which is further supported by D₂O exchange. ¹³C NMR spectrum also supported the presence of amide group from the deshielding value of carbon attached to –CONH group at 169.3 ppm and carbonyl group (part of a five member ring) at 169.47 ppm.

Table 2: Physical data for 5a –5j.

Entry
Substitution R
Yield (%)

5a
4-OCH₃ phenyl
85

5b
2-NO₂ phenyl
95

5c
4-F phenyl
89

5d
3-Cl phenyl
77

5e
4-Br phenyl
90

5f
4-OH phenyl
73

5g
4-CH₃ phenyl
84

5h
2-Cl phenyl
71

5i
4-NO₂ phenyl
79

5j
3-Br phenyl
88

Scheme 2: Reaction scheme for the synthesis of 5a–5j.

3. Conclusion

In summary, an efficient protocol for the synthesis of new 1, 2, 4-aryl triazoles and 4-thiazolidinones has been described. Herein, we are reporting the solvent free protocol for the synthesis of N-substituted 1, 2, 4-aryl triazoles (4a–4j) from potassium salt (3) . In literature, the synthesis of 4-thiazolidinones was carried out via 2 steps, but, to avoid multisteps and to make it more viable, we have developed a single-step reaction for the synthesis of 4-thiazolidinones (5a-5j) from hydrazide (2) .

4. Experimental

Melting points were determined in open capillary tubes and are uncorrected. Formation of the compounds was checked by TLC on silica gel-G plates of 0.5 mm thickness. IR spectra were recorded on Shimadzu FT-IR-8400 instrument using DRS (diffusive reflectance system) method. Mass spectra were recorded on Shimadzu GC-MS system (model QP-2010) using direct inlet probe technique. ¹H NMR and ¹³C NMR were determined in CDCl₃ and DMSO-d₆ on a Bruker AC 400 MHz and 100 MHz spectrometer. Elemental analysis of all the synthesized compounds was carried out on Euro EA 3000 elemental analyzer and the results are in agreement with the structures assigned.

4.1. General Procedure for the Synthesis of Functionalized 1, 2, 4-Aryl Triazoles  (4a–4j)

To a stirred solution of 6-fluorochroman-2-carboxylic acid (0.01 mol) in methanol at room temperature, concentrated H₂SO₄ (0.01 mol) was added and reaction mixture was allowed to stir at RT for 10 hours. After completion of the reaction, solvent was evaporated and the resulting mass was poured on to ice, neutralized with saturated sodium bicarbonate solution. Separated solid precipitate was filtered, washed with water, and dried to afford methyl 6-fluorochroman-2-carboxylate 1.

Compound 1 (0.01 mol) in absolute ethanol was taken into the RBF and cooled at (−5)°C. To the previously cooled solution hydrazine hydrate (99%, 0.08 mol) was added and reaction mixture was allowed to stir at 0–(−5)°C for 10 hours. After the completion of reaction separated solid residues were filtered, washed with cold ethanol, and dried to afford 6-fluorochroman-2-carbohydrazide 2, yield: 2.0 g (98%).

To a mixture of compound 2 (0.1 mol) and potassium hydroxide (0.15 mol) in methanol carbon disulphide (0.15 mol) was added dropwise. Reaction mass was allowed to stir at RT for 22–24 hours. After completion of reaction the obtained solid was filtered, washed with diethyl ether, and dried to afford compound 3. There is no need to purify the salt for further reaction.

An equimolar mixture of potassium 2-[(6-fluorochroman-2-yl) carbonyl] hydrazine carbodithioate 3 (0.01 mol) and substituted aniline (0.01 mol) was taken in RBF and heated at 140–150°C for 12–15 hours until the evolution of H₂S gas ceased. After completion of reaction solid residue was dissolved in DMF, treated with dilute HCl, and poured on crushed ice. The product was isolated and crystallized from ethanol to give compounds 4a–4j as analytical pure product.

4.1.1. 5-(6-Fluorochroman-2-yl)-4-(-tolyl)-4-1, 2, 4-triazole-3-thiol (4a)

Yield 89%, mp 170–172°C; IR (DRS): 3076(Ar, C–H str.), 2924(C–H str.), 2573(–SH str.), 1735(C=O str.), 1087(C–N str.), 1041(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.02–2.44(m, 5H, 2CH, 3CH), 2.65–2.96(m, 2H, 2CH), 4.83–4.90(dd,  Hz, 6 Hz, 1H, CH), 6.60–6.64(m, 1H, ArH), 6.73–6.76(m, 2H, ArH), 7.05–7.49(m, 4H, ArH), 11.43(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃):  ppm 20.3(CH₃), 26.27(CH₂), 28.87(CH₂), 85.3(CH), 108.52(CH), 112.98(CH), 116.81(CH), 119.54(CH), 129.2(C), 131.16(C), 133.09(CH), 136.12(C), 139.69(C), 155.8(C), 158.29(C), 173.99(C). MS: m/z = 341 [M]⁺; Anal. Calcd for C₁₈H₁₆FN₃OS: C, 63.32; H, 4.72; N, 12.31. Found: C, 63.23; H, 4.41; N, 12.28%.

4.1.2. 4-(3-Chlorophenyl)-5-(6-fluorochroman-2-yl)-4-1, 2, 4-triazole-3-thiol (4b)

Yield 86%, mp 205–207°C; IR (DRS): 3066(Ar, C–H str.), 2914(C–H str.), 2850(C–H str.), 2533(–SH str.), 1558(Ar, C=C bend.), 1375(C–H ben), 800(C–Cl str.), 1087(C–N str.), 1041(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.27–2.30(m, 2H, 2CH), 2.82–2.95(m, 2H, 2CH), 4.92–4.95(dd,  Hz, 12 Hz, 1H, CH), 6.50–6.54(m, 1H, ArH), 6.75–6.79(m, 2H, ArH), 7.41–7.43(m, 1H, ArH), 7.53–7.55(m, 3H, ArH), 14.0(s, 1H, SH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 25.27(CH₂), 28.27(CH₂), 85.3(CH), 112.98(CH), 116.81(CH), 120.08(CH), 122.3(CH), 125.68(CH), 129.2(C), 133.41(CH), 138.88(C), 139.69(C), 142.37(C), 155.8(C), 158.29(C), 173.99(C) MS: m/z = 361 [M]⁺; Anal. Calcd for C₁₇H₁₃ClFN₃OS: C, 56.43; H, 3.62; N, 11.61. Found: C, 56.18; H, 3.49; N, 11.59%.

4.1.3. 5-(6-Fluorochroman-2-yl)-4-(4-fluorophenyl)-4-1, 2, 4-triazole-3-thiol (4c)

Yield 78%, mp 188–190°C; IR (DRS): 3030(Ar, C–H str.), 2558(–SH str.), 1581(–C=C–, str.), 1225(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.88–4.93(dd,  Hz, 6 Hz, 1H, CH), 6.51–6.55(m, 1H, ArH), 6.77–6.81(m, 2H, ArH), 7.53–7.57(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃): 26.27(CH₂), 28.87(CH₂), 85.3(CH), 108.52(CH), 112.98(CH), 116.81(CH), 118.6(CH), 122.97(CH), 129.2(C), 133.7(C), 139.69(C), 155.8(C), 158.29(C), 160.51(C), 173.99(C). MS: m/z = 345 [M]⁺; Anal. Calcd for C₁₇H₁₃F₂N₃OS: C, 59.12; H, 3.79; N, 12.17. Found: C, 59.02; H, 3.53; N, 12.01%.

4.1.4. 4-(2, 5-Dimethylphenyl)-5-(6-fluorochroman-2-yl)-4-1, 2, 4-triazole-3-thiol (4d)

Yield 95%, mp 123–125°C; IR (DRS): 3074(Ar, C–H str.), 2984(C–H str.), 1645(–C=C–, str.), 1468(C–H bending) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 1.92(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.85–4.92(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.29–7.43(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃):  ppm 17.98(CH₃), 26.87(CH₂), 28.87(CH₂), 30.2(CH₃), 85.3(CH), 108.52(CH), 116.81(CH), 118.6(CH), 112.98(CH), 124.19(CH), 132.61(CH), 134.95(C), 138.13(C), 140.75(C), 146.2(C), 155.8(C), 158.29(C), 175.05(C). MS: m/z = 355 [M]⁺; Anal. Calcd for C₁₉H₁₈FN₃OS: C, 64.21; H, 5.10; N, 11.82. Found: C, 64.16; H, 4.93; N, 11.78%.

4.1.5. 4-(3, 4-Dimethylphenyl)-5-(6-fluorochroman-2-yl)-4-1, 2, 4-triazole-3-thiol (4e)

Yield 84%, mp 163–165°C; IR (DRS): 3081(Ar, C–H str.), 2975(C–H str.), 2575(–SH str.), 1641(C–H bending), 1579(–C=C–, str.), 1142(C–F str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.85–4.92(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.29–7.43(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃):  ppm 19.0(CH₃), 20.01(CH₃), 26.27(CH₂), 28.87(CH₂), 85.3(CH), 112.98(CH), 116.81(CH), 117.91(CH), 124.04(CH), 129.2(C), 132.85(C), 133.52(C), 139.69(C), 141.78(C), 143.79(C), 155.8(C), 158.29(C), 173.998(C). MS: m/z = 355 [M]⁺; Anal. Calcd for C₁₉H₁₈FN₃OS: C, 64.21; H, 5.10; N, 11.82. Found: C, 64.09; H, 5.03; N, 11.50%.

4.1.6. 5-(6-Fluorochroman-2-yl)-4-(2-fluorophenyl)-4-1, 2, 4-triazole-3-thiol (4f)

Yield 79%, mp 108–110°C; IR (DRS): 3080(Ar, C–H str.), 2983(C–H str.), 2561(–SH str.), 1629(C–H bending), 1572(C–H bending), 1525(–C=C–, str.) 1196(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.90–4.97(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.24–7.75(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃):  ppm 26.27(CH₂), 28.87(CH₂), 85.3(CH), 108.52(CH), 112.98(CH), 116.81(CH), 119.7(C), 119.58(CH), 129.2(C), 129.95(CH), 130.09(CH), 130.97(CH), 139.69(C), 155.8(C), 158.29(C), 162.56(C), 173.99(C). MS: m/z = 345 [M]⁺; Anal. Calcd for C₁₇H₁₃F₂N₃OS: C, 59.12; H, 3.79; N, 12.17. Found: C, 58.96; H, 3.67; N, 12.06%.

4.1.7. 4-(2-Chlorophenyl)-5-(6-fluorochroman-2-yl)-4-1, 2, 4-triazole-3-thiol (4g)

Yield 76%, mp 192–194°C; IR (DRS): 3077(Ar, C–H str.), 2978(C–H str.), 2563(–SH str.), 1563(–C=C–, str.), 1464(H–C–H bend), 1310(C–O str.), 870(C–Cl str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.90–4.97(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.39–7.50(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃):  ppm 26.27(CH₂), 28.87(CH₂), 85.3(CH), 108.52(CH), 112.98(CH), 116.81(CH), 127.83(CH), 126.39(C), 128.04(CH), 129.2(C), 131.85(CH), 132.57(CH), 140.8(C), 142.53(C), 155.8(C), 158.29(C), 175.1(C). MS: m/z = 361 [M]⁺; Anal. Calcd C₁₇H₁₃ClFN₃OS: C, 56.43; H, 3.62; N, 11.61. Found: C, 55.97; H, 3.55; N, 11.59%.

4.1.8. 4-(3-Chloro-4-fluorophenyl)-5-(6-fluorochroman-2-yl)-4-1,2,4-triazole-3-thiol (4h)

Yield 87%, mp 139–141°C; IR (DRS): 3075(Ar, C–H str.), 2553(–SH str.), 1581(–C=C–, str.), 1423(H–C–H bend), 1281(C–O str.), 870(C–Cl str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.90–4.97(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.18–7.79(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 26.27(CH₂), 28.87(CH₂), 85.3(CH), 108.52(CH), 112.98(CH), 116.81(CH), 120.08(CH), 121.91(CH), 124.85(C), 125.71(CH), 129.2(C), 139.69(C), 141.09(C), 155.8(C), 156.41(C), 158.29(C), 173.99(C). MS: m/z = 379 [M]⁺; Anal. Calcd for C₁₇H₁₂ClF₂N₃OS: C, 53.76; H, 3.18; N, 11.06. Found: C, 53.69; H, 3.07; N, 10.90%.

4.1.9. 5-(6-Fluorochroman-2-yl)-4-(2-methoxyphenyl)-4-1, 2, 4-triazole-3-thiol (4i)

Yield 90%, mp 251–253°C; IR (DRS): 3075(Ar, C–H str.), 2553(–SH str.), 1581(–C=C–, str.), 1423(H–C–H bend), 1281(C–O str.), 870(C–Cl str.), 1080(C–F str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 3.83(s, 3H, OCH3), 4.90–4.97(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 6.99–7.51(m, 4H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 26.27(CH₂), 28.87(CH₂), 56.32(CH₃), 85.3(CH), 108.52(CH), 112.98(CH), 115.51(CH), 116.81(CH), 120.83(CH), 123.69(CH), 129.2(C), 131.19(CH), 134.73(C), 139.24(C), 155.8(C), 157.76(C), 158.29(C), 173.54(C). MS: m/z = 357 [M]⁺; Anal. Calcd for C₁₈H₁₆FN₃O₂S: C, 60.49; H, 4.51; N, 11.76. Found: C, 60.39; H, 4.29; N, 11.37%.

4.1.10. 4-(2, 5-Difluorophenyl)-5-(6-fluorochroman-2-yl)-4-1,2,4-triazole-3-thiol (4j)

Yield 75%, mp 229–231°C; IR (DRS): 3061(Ar, C–H str.), 2951 (C–H str.), 2535(–SH str.), 1589(–C=C–, str.), 1462(H–C–H bend), 1520(C–O str.), 1075(C–F str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.34(s, 6H, 3CH, 3CH), 2.21–2.46(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 3.83(s, 3H, OCH3), 4.90–4.97(dd,  Hz, 6 Hz, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.13–7.22(m, 3H, ArH), 13.05(s, 1H, SH). ¹³C NMR (100 MHz, CDCl₃): 26.27(CH2), 28.87(CH2), 85.3(CH), 108.29(CH), 108.69(CH) 112.98(CH), 116.81(CH), 117.32(CH), 118.79(C), 127.11(CH), 129.2(C), 139.69 (C), 155.8(C), 158.29(C), 159.93(C), 173.54(C). MS: m/z = 363 [M]⁺; Anal. Calcd for C₁₇H₁₂F₃N₃O₂S: C, 56.19; H, 3.33; N, 11.56. Found: C, 56.06; H, 3.14; N, 11.32%.

4.2. General Procedure for the Synthesis of Functionalized 4-Thiazolidinones 5a–5j

An equimolar mixture of 6-fluorochroman-2-carbohydrazide 2 (0.01 mol) and different aryl aldehydes (0.01 mol) was taken in RBF and to this, thioglycolic acid (mercaptoacetic acid) (0.29 mol) in toluene was added. Then reaction mixture was allowed to reflux in a Dean-Stark assembly with continuous stirring. After completion of the reaction (48 hrs monitoring by TLC), the content was cooled to room temperature and then neutralized with saturated sodium bicarbonate solution. The organic extracts were washed with water and dried over Na₂SO4. The solvent was evaporated in vacuo and the resulting crude product was purified by column chromatography to give the analytical pure compounds 5a–5j. Column chromatography was carried out in hexane: ethyl acetate solvent system. Pure compound was eluted in 23% ethyl acetate in hexane.

4.2.1. 6-Fluoro--(2-(4-methoxyphenyl)-4-oxothiazolidine-3-yl) chroman-2-carboxamide (5a)

Yield 85%, mp 98–100°C; IR (DRS): 3383(Amide–NH str.), 3081(Ar, C–H str.), 2958(C–H str.), 1714(C=O str.), 1688(amide C=O str.), 1542(–NH bend), 1365(C–F str.), 1278(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.15–2.40(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 3.83(s, 3H, OCH3), 4.69–4.72(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.69–4.72(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 6.87–7.84(m, 4H, ArH), 8.0(s, 1H, NH), ¹³C NMR (100 MHz, DMSO-d₆):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 55.33(CH₃), 70.50(CH), 85.58(CH), 108.7(CH), 112.44(CH), 114.1(CH), 116.43(CH), 126.91(CH), 129.9(C), 133.68(C), 154.35(C), 157.18 (C), 155.8(C), 158.08(C), 165.35(C), 169.36(C). MS: m/z = 402 [M]⁺; Anal. Calcd for C₂₀H₁₉FN₂O₄S: C, 59.69; H, 4.76; N, 6.96. Found: C, 59.23; H, 4.61; N, 6.88%.

4.2.2. 6-Fluoro--(2-(2-nitrophenyl)-4-oxothiazolidine-3-yl) chroman-2-carboxamide (5b)

Yield 95%, mp 190–192°C; IR (DRS): 3392(Amide–NH str.), 3205(Ar, C–H str.), 1712(C=O str.), 1678(amide C=O str.), 1523(–NH bend), 1590(N=O str.), 1259(C–O–C str.), 1190(C–F str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 1.81–2.05(m, 2H, 2CH), 2.61–2.74(m, 2H, 2CH), 3.68–3.72(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.66–4.69(dd,  Hz, 3.2 Hz, 1H, CH), 6.12(s, 1H, CH), 6.72–6.79(m, 1H, ArH), 6.84–6.91(m, 2H, ArH), 7.60–7.63(t, 1H, ArH), 7.78–7.87(m, 2H, ArH), 8.04–8.06(d,  Hz, 1H, ArH), 10.43–10.46(d,  Hz, 1H, NH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 68.3(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 123.91(CH), 125.5(C), 129.87(CH), 129.9(C), 127.85(CH), 132.06(C), 149.87(C), 154.35(C), 157.18 (C), 169.36(C). MS: m/z = 417 [M]⁺; Anal. Calcd for C₁₉H₁₆FN₃O₅S: C, 54.67; H, 3.86; N, 10.07. Found: C, 54.58; H, 3.49; N, 9.99%.

4.2.3. 6-Fluoro--(2-(4-fluorophenyl)-4-oxothiazolidine-3-yl) chroman-2-carboxamide (5c)

Yield 89%, mp 106–110°C; IR (DRS): 3487(Amide–NH str.), 3041(Ar, C–H str.), 1710(C=O str.), 1676(amide C=O str.), 1537(–NH bend), 1201(C–O–C str.), 1190(C–F str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 1.82–2.02(m, 2H, 2CH), 2.56–2.70(m, 2H, 2CH), 3.59–3.78(m, 2H, 2CH), 4.45–4.58(dd,  Hz, 11.52 Hz, 1H, CH), 5.79–5.83(d,  Hz, 1H, CH), 6.54–6.72(m, 3H, ArH), 6.86–6.90(t, 1H, ArH), 6.99–7.03(t, 1H, ArH), 7.20–7.22(t, 1H, ArH), 7.33–7.36(t, 1H, ArH), 8.05–8.13(d,  Hz, 1H, NH). ¹³C NMR (100 MHz, CDCl₃):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 70.52(CH), 85.58(CH), 108.7(CH), 113.27(CH), 114.1(CH), 116.43(CH), 127.64(CH), 129.9(C), 136.68(C), 154.35(C), 157.18 (C), 160.07(C), 165.35(C), 169.36(C). MS: m/z = 390 [M]⁺; Anal. Calcd for C₁₉H₁₆F₂N₂O₃S: C, 58.45; H, 4.13; N, 7.18. Found: C, 58.02; H, 4.03; N, 7.10%.

4.2.4. -(2-(3-Chlorophenyl)-4-oxothiazolidine-3-yl)-6-fluorochroman-2-carboxamide (5d)

Yield 77%, mp 151–153°C; IR (DRS): 3401(Amide–NH str.), 3200(Ar, C–H str.), 1717(C=O str.), 1645(amide C=O str.), 1550(–NH bend), 1245(C–F str.), 1201(C–O–C str.), 820(C–Cl str.) cm⁻¹; ¹H NMR (400 MHz, DMSO):  ppm 2.15–2.40(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.66–4.69(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.69–4.72(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.24–7.43(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, CDCl₃):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 71.78(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 124.5(CH), 124.93(CH), 126.41(CH), 128(CH), 132.25(C), 140.45(C), 145.35(C), 157.18 (C), 165.35(C), 169.36(C). MS: m/z = 406 [M]⁺; Anal. Calcd for C₁₉H₁₆ClFN₂O₃S: C, 56.09; H, 3.96; N, 6.89. Found: C, 55.90; H, 3.83; N, 6.83%.

4.2.5. -(2-(4-Bromophenyl)-4-oxothiazolidine-3-yl)-6-fluorochroman-2-carboxamide (5e)

Yield 90%, mp 118–120°C; IR (DRS): 3452(Amide–NH str.), 3000(Ar, C–H str.), 1725(C=O str.), 1640(amide C=O str.), 1545(–NH bend), 1345(C–F str.), 1251(C–O–C str.), 520(C–Br str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.15–2.40(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.12–7.85(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 70.50(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 120.41(C), 126.7(CH), 129.36(CH), 129.9(C), 138.93(C), 154.35(C), 157.18 (C), 165.35(C), 169.36(C). MS: m/z = 452 [M+1]⁺; Anal. Calcd for C₁₉H₁₆BrFN₂O₃S: C, 50.56; H, 3.57; N, 6.21. Found: C, 50.45; H, 3.28; N, 6.11%.

4.2.6. 6-Fluoro--(2-(4-hydroxyphenyl)-4-oxothiazolidine-3-yl) chroman-2-carboxamide (5f)

Yield 73%, mp 132–134°C; IR (DRS): 3452(Amide–NH str.), (–OH, broad), 3011(Ar, C–H str.), 1728(C=O str.), 1645(amide C=O str.), 1545(–NH bend), 1352(C–F str.), 1278(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.15–2.40(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.35(s, 1H, OH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.14–7.86(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 55.33(CH₃), 70.50(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 116.68(C), 125.81(CH), 129.9(C), 132.68(C), 154.35(C), 157.46 (C), 157.18(C), 165.35(C), 169.36(C). MS: m/z = 388 [M]⁺; Anal. Calcd for C₁₉H₁₇FN₂O₄S: C, 58.75; H, 4.41; N, 7.21. Found: C, 58.56; H, 4.34; N, 7.06%.

4.2.7. 6-Fluoro--(4-oxo-2-(-tolyl) thiazolidin-3-yl) chroman-2-carboxamide (5g)

Yield 84%, mp 89–91°C; IR (DRS): 3328(Amide–NH str.), 2998(Ar, C–H str.), 2900(C–H str.), 1741(C=O str.), 1652(amide C=O str.), 1548(–NH bend), 1371(C–F str.), 1300(C–O–C str.) cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆):  ppm 2.15–2.32(m, 2H, 2CH), 2.34(s, 3H, 3CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.11(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, DMSO-d₆):  ppm 21.03(CH₃), 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 70.50(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 126.73(CH), 127.98(CH), 129.9(C), 136.48(C), 136.52(C), 154.35(C), 157.18(C), 165.35(C), 169.36(C). MS: m/z = 386 [M]⁺; Anal. Calcd C₂₀H₁₉FN₂O₃S: C, 62.16; H, 4.96; N, 7.25. Found: C, 62.07; H, 4.55; N, 7.09%.

4.2.8. -(2-(2-Chlorophenyl)-4-oxothiazolidine-3-yl)-6-fluorochroman-2-carboxamide (5h)

Yield 71%, mp 158–160°C; IR (DRS): 3412(Amide–NH str.), 3212(Ar, C–H str.), 1725(C=O str.), 1685(amide C=O str.), 1558(–NH bend), 1251(C–F str.), 1228(C–O–C str.), 800(C–Cl str.), 770(o-di substituted) cm⁻¹; ¹H NMR (400 MHz, DMSO):  ppm 2.15–2.32(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.17–7.65(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, CDCl₃):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 67.50(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 125.18(CH), 125.89(CH), 127.02(CH), 127.26(CH), 129.9(C), 131.68(C), 133.39(C), 154.35(C), 157.18 (C), 165.35(C), 169.36(C). MS: m/z = 406 [M]⁺; Anal. Calcd for C₁₉H₁₆ClFN₂O₃S: C, 56.09; H, 3.96; N, 6.89. Found: C, 55.93; H, 3.77; N, 6.84%.

4.2.9. 6-Fluoro--(2-(4-nitrophenyl)-4-oxothiazolidine-3-yl) chroman-2-carboxamide (5i)

Yield 79%, mp 207–209°C; IR (DRS): 3398(Amide–NH str.), 3212(Ar, C–H str.), 1728(C=O str.), 1688(amide C=O str.), 1543(–NH bend), 1595(N=O str.), 1272(C–O–C str.), 1290(C–F str.) 790(p-di substituted) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.15–2.32(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.49–8.14(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, CDCl₃):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 70.52(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 122.91(CH), 126.32(CH), 129.9(C), 144.08(C), 145.35(C), 154.35 (C), 157.18(C), 165.35(C), 169.36(C). MS: m/z = 417 [M]⁺; Anal. Calcd for C₁₇H₁₄FN₃O₂: C, 54.67; H, 3.86; N, 10.07. Found: C, 54.39; H, 3.79; N, 9.89%.

4.2.10. -(2-(3-Bromophenyl)-4-oxothiazolidine-3-yl)-6-fluorochroman-2-carboxamide (5j)

Yield 88%, mp 166–168°C; IR (DRS): 3482(Amide–NH str.), 3110(Ar, C–H str.), 1745(C=O str.), 1590(amide C=O str.), 1485(–NH bend), 1354(C–F str.), 1281(C–O–C str.), 680(m-di substituted), 520(C–Br str.) cm⁻¹; ¹H NMR (400 MHz, CDCl₃):  ppm 2.15–2.32(m, 2H, 2CH), 2.75–2.85(m, 2H, 2CH), 4.63–4.66(d,  Hz, 1H, CH), 3.91–3.95(d,  Hz, 1H, CH), 4.63–4.66(dd,  Hz, 3.2 Hz, 1H, CH), 5.92(s, 1H, CH), 6.72–6.95(m, 3H, ArH), 7.22–7.41(m, 4H, ArH), 8.0(s, 1H, NH). ¹³C NMR (100 MHz, CDCl₃):  ppm 25.25(CH₂), 26.19(CH₂), 34.2(CH₂), 70.32(CH), 85.58(CH), 108.7(CH), 114.1(CH), 116.43(CH), 120.91(C), 127.55(CH), 127.95(CH), 128.17(CH), 128.74(CH), 129.9(C), 140.65(C), 154.35(C), 157.18 (C), 165.35(C), 169.36(C).MS: m/z = 452 [M+1] ⁺; Anal. Calcd for C₁₉H₁₆FN₃O₅S: C, 50.56; H, 3.57; N, 6.21. Found: C, 50.17; H, 3.14; N, 6.12%.

Conflict of Interests

The authors do not have a direct financial relation with the commercial identity mentioned in the paper that might lead to a conflict of interests for any of the authors.

Acknowledgments

The authors are thankful to the department of chemistry for providing laboratory facilities. The authors are thankful for facilities and grants given under UGC-SAP for Department Research Support (DRS) and Department of Science and Technology (DST) New Delhi for Fund for Improvement of Science and Technology (FIST). The authors are also thankful to RSIC Chandigarh for providing ¹H NMR and ¹³C NMR spectral analysis of the compounds.

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