Synthesis, Characterization and Antimicrobial Activity of Thiazolo-Oxazine Fused Heterocyclic Derivatives Based on Benzene Sulfonyl Hydrazide

Introduction

Recently, the chemistry of sulfohydrazide (-SO₂NHNH₂) received more attention by the chemists and biochemists.^1-4 Various heterocyclic compounds are documented from aryl sulfonyl hydrazides^5-7 and tested for their potent biological activities. The aryl sulfonyl hydrazones are found to be antitubercular and anticancer agents.^8-10 The pyrrole derivatives are more pertinent to antitubercular activity reported recently.¹¹ It was found regarding the Schiff bases of benzene sulfonyl hydrazide with common benzaldehyde not being heterocyclised as well as fused derivatives. However, the disubstituted benzaldehyde-based Schiff bases of benzene sulfonyl hydrazide have been reported as antitumor agents.¹² With these excellent medicinal properties of heterocyclic derivatives of aryl sulfonyl hydrazides^5-11 were explored in the field of hetereocyclization with Schiff bases of benzene sulfonyl hydrazides.  Thus, the study comprises with the post heterocyclization of Schiff bases of benzene sulfonyl hydrazide. The Schematic diagram of the synthesis scheme is shown in Results and discussion part.    

Material and methods

Analytical grade chemicals were used in all experiments. The melting point (uncorrected) of all compounds were determined by using an open capillary method. TLC method was used for purity of compounds. All compounds were scanned for FTIR and ¹H NMR spectra were scanned on Bruker using DMSO-d6 solvent and TMS as reference. Elemental content of all compounds determined by Thermofinigan Flash EA (Italy). The sulfur and halogen determined by Carious method. The antibacterial activity of all the three series of compounds were evaluated by agar cup method^13-15 against the gram-positive and gram-negative bacteria shown in Table – 1.

General procedure

Step I

(i) Synthesis of benzenesulfonyl hydrazide Schiff base formation of (1a-e):

The Schiff base (1a-e) were prepared (Scheme-1) by refluxing a solution of benzene sulfonyl hydrazide and benzaldehyde derivatives (shown is Scheme – 1) in THF solvent for 6 hr. The solvent THF was vacuum distilled. The solid was washed by water and used for further reaction.

(ii) Preparation of N-(4-oxo-2-substituted thiazolidin-3-yl) benzenesulfonamide (2a-e):

The mixture of Schiff base (1a-e) (0.01 mole), Mercapto acetic acid (0.0125 mole), DMF Solvent (10 ml) with a little of dry zinc chloride was heated up to boiling for 8 to 9 hours.

The product was then isolated from reaction mixture and washed. The product obtained was purified by chromatographically. Finally crystallized from methanol to give 4-thiazolidinones (2a-e), which were obtained in 70-80% yield.

Step II

Synthesis of (Z)-N-(5-((5-nitrofuran-2-yl) methylene)-4-oxo-2-substituted thiazolidin-3-yl) benzenesulfonamide (3a-e):

A mixture of 4-thiazolidinone derivatives (2a-e) (0.01 mole) and 5-Nitro-2-furaldehyde (0.01 mole) in ethanolic sodium hydroxide solution (35 ml) was boiled for 5 hr.

The solid mass was isolated from reaction mixture and washed. Finally recrystallized from ethanol to get 5-(5-nitrofurylidine) derivatives (3a-e).

Step III

Synthesis of N-(7-(5-nitrofuran-2-yl)-2-substituted phenyl-5-(phenylamino)-2H-thiazolo [5,4-e][1,3]oxazin-3(7H)-yl)benzenesulfonamide (4a-e):

5-nitrofurylidine thiazolidinone (3a-e) (0.02 mole) and N-phenyl urea (0.02 mole) were dissolved in sodium ethanolate solution in ethanol (30ml). The resultant solution was stirred on magnetically for 4 hrs and then added to crushed ice with gentle stirring for 4 hr. It was kept in cooling chamber (15℃) for 24 hr. The crystals were obtained and further recrystallised from ethyl alcohol.

Results and discussion

Scheme 1 Click here to View Scheme

Schematic diagram of preparation of thiazolidinone and thiazolo-oxazine fused derivatives based on Schiff bases of benzene sulfonyl hydrazide

2a

N-(4-oxo-2-phenylthiazolidin-3-yl)benzenesulfonamide-Product: 75%, m.p. 203-205℃, FT-IR (KBr): 1725-1758 (Cyclic C=O), 1200-1250 (S=O), 3310-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.85, 3.95 (d, 2H, -CH₂ Thiazolidinone), 5.91 (s, 1H, -CH Thiazolidinone), 7.26-7.71 (m, 10H, Aromatic), LC-MS : m/z 335.40, Theoretical for C₁₅H₁₄N₂O₃S₂ : C-53.87, H-4.22, N-4.22, N-8.38, S-19.18 Obtained: C-53.90, H-4.20, N-8.40, S-19.20%

2b

N-(2-(4-chlorophenyl)-4-oxothiazolidin-3yl)benzenesulfonamide-Product: 76%, m.p. 196-199℃, FT-IR (KBr): 1725-1755 (Cyclic C=O), 1200-1245 (S=O), 3310-3340 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.80, 3.92 (d, 2H, -CH₂ Thiazolidinone), 5.90 (s, 1H, -CH Thiazolidinone), 7.26-7.65 (m, 9H, Aromatic), LC-MS : m/z 369.90, Theoretical for C₁₅H₁₃ClN₂O₃S₂ : C-48.84, H-3.55, N-7.59, S-17.39, Cl-9.61% Obtained: C-48.90, H-3.50, N-7.50, S-17.40, Cl-9.60%.

2c

N-(2-(4-bromophenyl)-4-oxothiazolidin-3yl)benzenesulfonamide-product: 74%, m.p. 188-190℃, FT-IR (KBr: 1727-1757 (Cyclic C=O), 1210-1250 (S=O), 3310-3345 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.85, 3.90 (d, 2h, -CH₂ Thaizolidinone), 5.85 (s, 1H, -CH Thiazolidinone), 7.20-7.60 (m, 9H, Aromatic), LC-MS : m/z 423.31, Theoretical for C₁₅H₁₃BrN₂O₃S₂ : C-43.59, H-3.17, N-6.78, S-15.52, Br-19.33% Obtained: C-43.60, H-3.00, N-6.80, S-15.50, Br-19.30%.

2d

N-(2-(4-fluorophenyl)-4-oxothiazolidin-3-yl)benzenesulfonamide-Product: 75%, m.pm. 178-182℃, FT-IR (KBr): 1725-1755 (Cyclic C=O), 1205-1250 (S=O), 3310-3347 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.84, 3.92 (d, 1H, -CH₂ Thiazolidinone), 5.83 (s, 1H, -CH Thiazolidinone), 7.81-7.55 (m, 9H, Aromatic), LC-MS : m/z 352.40, Theoretical for C₁₅H₁₃FN₂O₃S₂ : C-51.12, H-3.72, N-7.95, S-18.20, F-5.39% Obtained: C-51.10, H-3.70, N-8.00, S-18.20, Br-5.40%.

2e

N-(2-(3-nitrophenyl)-4-oxothiazolidin-3-yl)benzenesulfonamide-Product: 73%, m.p. 205-208℃, FT-IR (KBr): 1735-1765 (Cyclic C=O), 1210-1250 (S=O), 3320-3355 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.85, 3.98 (d, 2H, -CH₂ Thiazolidinone), 5.93 (s, 1H, -CH Thiazolidinone), 7.25-7.65 (m, 9H, Aromatic), LC-MS : m/z 379.41 Theoretical for C₁₅H₁₃N₃O₅S₂ : C-47.48, H-3.45, N-11.08, S-16.90% Obtained: C-47.50, H-3.50, N-11.00, S-16.90%.

3a

N-(5-((5-nitrofuran-2-yl)methylene)-4-oxo-2-pheynlthiazolidin-3-yl)benzenesulfonamide-Product: 87%, m.p. 155-157℃, FT-IR (KBr): 1568 (C=C), 1730-1670 (C=O), 1250-1200 (S=O), 3310-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 7.71 (s, 1H, CH=C), 5.91 (s, 1H, -CH Thiazolidinone), 7.26-7.71 (m, 10H, Aromatic), LC-MS : m/z 458.50, Theoretical for C₂₀H₁₅N₃O₆S₂ : C-52.51, H-3.30, N-9.19, S-14.02 Obtained: C-52.50, H-3.30, N-9.20, S-14.00%.

3b

N-(2-(4-chlorophenyl)-5-((5-nitrofuran-2-yl)methylene)4-oxothiazolidin-3-yl)-benzene sulfonamide-Product: 88%, m.p. 153-155℃, FT-IR (KBr): 1569 (C=C), 1720-1660 (C=O), 1250-1200 (S=O), 3315-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 7.73 (s, 1H, CH=C), 5.90 (s, 1H, -CH Thiazolidinone), 7.30-7.70 (m, 9H, Aromatic), LC-MS : m/z 492.90, Theoretical for C₂₀H₁₄ClN₃O₆S₂: C-48.83, H-2.87, N-8.54, S-13.04, Cl-7.21 Obtained: C-48.80, H-2.90, N-8.50, S-13.10, Cl-7.20%.

3c

N-(2-(4-bromophenyl)-5-((5-nitrofurnan-2-yl)methylene)-4-oxothiazolidin-3-yl)-benzene sulfonamide-Product: 89%, m.p. 145-147℃, FT-IR (KBr): 1570 (C=C), 1730-1650 (C=O), 1240-1200 (S=O), 3325-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 7.65 (s, 1H, CH=C), 5.85 (s, 1H, -CH Thiazolidinone), 7.40-7.70 (m, 9H, Aromatic), LC-MS : m/z 536.5, Theoretical for C₂₀H₁₄BrN₃O₆S₂: C-44.78, H-2.63, N-7.83, S-11.96, Br-14.90 Obtained: C-44.80, H-2.60, N-7.80, S-12.00, Br-14.90%.

3d

N-(2-(4-fluorophenyl)-5-((5-nitrofuran-2-yl)methylene)-4-oxothiazolidin-3-yl)-benzene sulfonamide-Product: 90%, m.p. 142-145℃, FT-IR (KBr): 1560 (C=C), 1740-1660 (C=O), 1240-1190 (S=O), 3320-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 7.70 (s, 1H, CH=C), 5.75 (s, 1H, -CH Thiazolidinone), 7.40-7.70 (m, 9H, Aromatic), LC-MS : m/z 476.50, Theoretical for C₂₀H₁₄FN₃O₆S₂: C-50.52, H-2.97, N-8.84, S-13.49, F-4.00 Obtained C-50.50, H-3.00, N-8.80, S-13.50, F-4.00%.

3e

N-(2-(3-nitrophenyl)-5-((5-nitrofuran-2-yl)methylene)-4-oxothiazolidin-3-yl)-benzenesulfonamide-Product: 92%, m.p. 158-160℃, FT-IR (KBr): 1570 (C=C), 1750-1670 (C=O), 1245-1185 (S=O), 3320-3350 (-NH), ¹H NMR (400 MHZ, DMSO-d₆): ẟ 7.60 (s, 1H, CH=C), 5.70 (s, 1H, -CH Thiazolidinone), 7.45-7.75 (m, 9H, Aromatic), LC-MS, m/z 503.50, Theoretical for C₂₀H₁₄N₄O₈S₂: C-47.81, H-2.81, N-11.15, S-12.76 Obtained: C-47.80, H-2.80, N-11.10, S-12.80%.

4a

N-(7-(5-nitrofuran-2yl)-2-phenyl-5-(phenylamino)-2H-thiazolo[5,4-e][1,3]oxazin-3(7H)-yl)benzenesulfonamide-Product: 64%, m.p. 182-185℃, FT-IR (KBr): 1158 (C-N), 1024, 1126 (C-O-C), 1460, 1510, 1585 (C=C), 1250-1200 (S=O), 3310-3350 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.7 (s, 1H, oxazin ring), 4.0 (s broad, 1H, -NH), 4.23 (s, 1H, Thiazolo ring), 6.43-7.86 (m, 17H, Aromatic & furan), LC-MS : m/z 576.60, Theoretical for C₂₇H₂₁N₅O₆S₂ : C-56.34, H-3.68, N-12.17, S-11.14 Obtained: C-56.30, H-3.70, N-12.20, S-11.10%.

4b

N-(2-(4-chlorophenyl)-7-(5-nitrofuran-2-yl)-5-(phenylamino)-2H-thiazolo[5,4-e][1,3]oxazin-3(7H)-ylbenzenesulfonamide-Product: 65%, m.p. 178-180℃, FT-IR (KBr): 1156 (C-N), 1025, 1228 (C-O-C), 1458, 1505, 1580 (C=C), 1240-1200 (S=O), 3310-3345    (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.65 (s, 1H, oxazin ring), 4.2 (s broad, 1H, -NH), 4.25 (s, 1H, Thiazolo ring), 6.40-7.85 (m, 16H, Aromatic & furan), LC-MS : m/z 611.10 Theoretical for C₂₇H₂₀ClN₅O₆S₂ : C-53.16, H-3.30, N-11.48, S-10.51, Cl-5.81 Obtained: C-53.20, H-3.30, N-11.50, S-10.50, Cl-5.80%.

4c

N-(2-(4-bromophenyl)-7-(5-nitrofuran-2-yl)-5-(phenylamino)-2H-thiazolo[5,4-e][1,3]oxazin-3(7H)-ylbenzenesulfonamide-Product: 66%, m.p. 164-166℃, FT-IR (KBr): 1155 (C-N), 1022, 1230, (C-O-C), 1462, 1507, 1568 (C=C), 1245-1200 (S=O), 3310-3347   (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.67 (s, 1H, oxazin ring), 4.15 (s broad, 1H, -NH), 4.30 (s, 1H, Thiazolo ring), 6.45-7.80 (m, 16H, Aromatic & furan), LC-MS : m/z 655.50 Theoretical for C₂₇H₂₀BrN₅O₆S₂ : C-49.55, H-3.08, N-10.70, S-9.80, Br-12.21 Obtained: C-49.60, H-3.00, N-10.70, S-9.70, Br-12.20%. 

4d

N-(2-4-fluorophenyl)-7-(5-nitrofuran-2yl)-5-(phenylamino)-2H-thiazolo[5,4-e][1,3]oxaxzin-3(7H)-yl)benzenesulfonamide-Product: 65%, m.p. 154-156℃, FT-IR (KBr): 1152 (C-N), 1020, 1234 (C-O-C), 1461, 1508, 1583 (C=C), 1247-1208 (S=O), 3310-3343    (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.64 (s, 1H, oxazin ring), 4.12 (s broad, 1H, -NH), 4.28 (s, 1H, Thiazolo ring), 6.48-7.78 (m, 16H, Aromatic & furan), LC-MS : m/z 594.60 Theoretical for C₂₇H₂₀FN₅O₆S₂ : C-54.63, H-3.40, N-11.80, F-3.20 Obtained: C-54.70, H-3.50, N-11.80, S-10.80, Br-3.20%.

4e

N-(2-(3-nitrophenyl)-7-(5-nitrofuran-2-yl)-5-(phenylamino)-2H-thiazolo[5,4-e][1,3]oxazin-3-(7H)-yl)benzenesulfonamide-Product: 67%, m.p. 162-164℃, FT-IR (KBr): 1157 (C-N), 1022, 1236, (C-O-C), 1465, 1512, 1580 (C=C), 1247-1208 (S=O), 3310-3345 (-NH), ¹H NMR (400 MHz, DMSO-d₆): ẟ 3.62 (s, 1H, oxazin ring), 4.12 (s broad, 1H, -NH), 4.28 (s, 1H, Thiazolo ring), 6.48-7.75 (m, 16H, Aromatic & furan), LC-MS : m/z 621.60, Theoretical for C₂₇H₂₀N₆O₈S₂ : C-52.25, H-3.25, N-13.54, S-10.33 Obtained: C-52.20, H-3.20, N-13.50, S-10.30%. 

Antibacterial Activity:

All the three series of compounds viz; 2a-e, 3a-e and 4a-e were monitored for antimicrobial activity. The common gram +Ve and -Ve bacteria (Shown in Table – 1) were used for the study. Sample solution in DMF was placed in a petri dish with nutrient agar and culture media. The zone of inhibition of growth of bacteria by a compound was measured. After on day incubation at 27℃. The result (Table – 1) are compared with standard Neomycin.

The inspection of the results of the all derivatives reveals that the derivatives 2b,c; 3b,c and 4b,c have excellent toxicity for bacteria used. The other derivatives have moderate toxicity for bacteria. The more toxicity of 2b,c; 3b,c and 4b,c may be responsible to presence of halogen in the structure. 

Table 1: Result of Antibacterial activity of 2a-e, 3a-e and 4a-e derivatives

Compound code	Zone of Inhibition of Growth of Bacteria (in mm)
	Gram +Ve		Gram -Ve
	Sta. Au.	Bac. sub.	Pse. Aer.	E. coli.
2a	8	7	9	7
2b	16	15	16	14
2c	19	18	17	18
2d	15	14	13	12
2e	10	11	11	12
3a	7	8	8	6
3b	17	15	15	15
3c	20	19	16	17
3d	15	14	14	13
3e	11	10	10	12
4a	8	9	7	6
4b	14	16	16	15
4c	18	18	17	18
4d	13	14	15	16
4e	10	12	13	14
Neomycin (Standard Drug)	23	24	24	23

 

 Bacterial full names are shown in Figures 1 to 3 as histogram

Figure 1: Histogram of Antibacterial Activity of derivatives 2(a-e). Click here to View Figure

Figure 2: Histogram of Antibacterial Activity of derivatives 3(a-e). Click here to View Figure

Figure 3: Histogram of Antibacterial Activity of derivatives 4(a-e). Click here to View Figure

Conclusion

Schiff Bases of Benzene sulfonyl hydrazide (SBSZ) were prepared and then post heterocyclization to 4-thiazolidinone derivatives. Further, fused heterocyclised derivatives i.e. thiazolo-oxazine were prepared by condensation of 4-thiazolidinone with 5-nitrofuraldehyde / phenyl urea. All these compounds were characterised duly. The antibacterial activity of all these compounds is good and more particularly chlorine containing derivatives have more antibacterial activity.

Acknowledgement

The Authors are grateful to Principal, Sheth M. N. Science College, H.N.G.U, Patan for giving us the access to required resources for this research work.

Conflict of Interest

There is no any conflict of interest.

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