Sample Paper
HL ISSN: 2231 – 3087(print) / 2230 – 9632 (Online)
(www.heteroletters.org) Vol. 1: (3), 2011, 241-245

SYNTHESIS OF 2- (6 -CHLOROBENZOTHIAZOL-2’-YL AMINO) -4- (2-CHLORO-4-TRIFLUOROMETHYL PHENYL THIOUREIDO)-6-(SUBSTITUTED THIOUREIDO)-1,3,5-TRIAZINE AS ANTIFUNGAL AGENTS

       

       

Vineeta Sareen, Vineeta Khatri and Prakash Jain

       

Department of Chemistry, University of Rajasthan,

Jaipur-302004, Rajasthan

E-mail:  sareenparmod@yahoo.com

       

       

ABSTRACT

2,4, 6-Trichloro-1,3,5-triazine has been reacted selectively with nucleophilic reagents, 2-amino -6- chlorobenzothiazole I, and then the product II so obtained is reacted with 2-chloro -4- trifluoromethyl phenyl thiourea III to give IV and then IV is reacted with different substituted thioureas V to give 2-(6-chlorobenzothiazol - 2’-yl amino) -4- (2- chloro -4- trifluoromethyl phenyl thioureido) -6-(substituted thioureido)-1, 3, 5-triazine VI. These compounds are evaluated for their antifungal activity and shown promising results. The structure of all these compounds have been confirmed by IR, 1HNMR, mass spectral data and elemental analysis. 

       

KEYWORDS

2-amino -6- chlorobenzothiazole, 2-chloro -4- trifluoromethyl phenyl thiourea, 2-(6-chlorobenzothiazol-2’-yl amino)-4,6-dichloro-1, 3, 5-triazine, 2-(6-chlorobenzothiazol - 2’-yl amino) -4- (2- chloro -4- trifluoromethyl phenyl thioureido) -6-(substituted thioureido)-1, 3, 5-triazine.

       

INTRODUCTION

Triazine nucleus has received the attention of synthetic chemists during the past few decades. Various pharmacological activities such as antibacterial, antifungal, herbicidal, metabolites and antifolatei-iv have been reported for triazine and its derivatives. The lipophilic behaviour of triazine derivatives imparts them with antimicrobial activity. S-triazines have chlorine atoms that can react with NH2 group which are capable of copolymerization and appear to be promising dentin bonding agentsv. Benzothiazole and thioureas also exhibit broad spectrum of biological activities. In continuation of our work on triazinesvi-vii we have synthesized some new derivatives of 2- (6-chlorobenzothiazol -2’-yl amino) -4- (2-chloro -4-trifluoro-methyl phenyl thioureido) -6- (substituted thioureido)-1, 3, 5-triazine VI (Scheme-I) with enhanced antifungal activity. 2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride) is reacted selectively with nucleophilic reagents. Cyanuric chloride is a weak base, if one of the chlorine is replaced by –NHR, OR or SR, the basicity is increased because of the electron releasing effect of –NHR, OR or SR substituted at a-positions of the ring nitrogen atoms. Three chlorine atoms of 2,4,6-trichloro- 1,3,5-triazine have been replaced subsequently by 2-amino-6-chlorobenzothiazole (which in turn is prepared by condensing chloroaniline with ammonium thiocyanate), 2-chloro-4-trifluoromethyl phenyl thiourea and substituted thioureas in alkaline medium selectively to give the title compound VI.2-(6-Chlorobenzothiazol-2’-yl amino) 4, 6-dichloro-1, 3, 5- triazine II has been prepared by treating cyanuric chloride in acetone with 2-amino-6-chlorobenzo-thiazole I at 0-5oC and stirring for 3 hrs. The second chlorine atom of II has been replaced by 2-chloro-4-trifluoromethyl phenyl thiourea at 30-40oC in acetone by constant stirring for 3 hrs to give 2-(6-chlorobenzothiazol-2’-yl amino)-4-(2’-chloro-4-trifluoro methyl phenyl thioureido)-6-chloro-1, 3, 5-triazine IV. The third chlorine atom of triazine has been replaced by different substituted thioureas at 80-90oC in acetone to give the title compound VI.FUNGICIDAL ACTIVITYCompounds VIa-h were screened for antifungal activity against Alternaria alternata, Aspergillus niger and Macrophomina using agar diffusion techniqueviii. Culture media were prepared using aseptic and sterilization techniques. Incubation period is 72 hrs at 28oC. All the solutions of test compounds were prepared by dissolving      1mg of testing sample in 1ml of acetone. This gives the concentration of sample 1000 μg/ml or 1000 ppm. Different dilutions such as 500 and 1000 ppm were prepared from the sample solution. Pure cultures of Alternaria alternata, Aspergillus niger and Macrophomina were raised in conical flask (100 ml) containing potato dextrose agar (PDA) medium. The spores obtained from ten days old cultures were used for testing the efficacy of test compounds against inhibition of spore germination, sterilized acetone was used as control.  

Percent spore inhibition is calculated by formula:

       

Evaluation of the fungicidal activity shows at 30-35 % activity is observed at 100 ppm, 36-50 % at 500 ppm and 55-72 % activity observed at 1000 ppm. Further, compounds VIa and VIb show maximum inhibition at all concentrations which may be attributed to, maximum fluoro substitution in these compounds. The fungicidal screening results are recorded in Table-II.

       

EXPERIMENTAL: Purity of all the compounds was checked on silica gel G plates using iodine vapour as the detecting agent. Melting points were determined in open capillary tubes using Gallenkamp melting point apparatus and are uncorrected. IR spectra were recorded on a Perkin-Elmer 577 spectrometer in KBr pellets. 1HNMR spectra were recorded on JEOL (model AL-300) spectrophotometer using TMS as an internal standard (chemical shifts are recorded in δ ppm). The mass spectra were recorded on Kratos MS-30 and MS-50 spectrometer operating at an ionization potential of 70 eV. Physical and analytical data of the compounds are recorded in

       

Table-I.  2-(6-Chlorobenzothiazol-2’-yl amino)-4, 6-dichloro 1, 3, 5-triazine II:

To 2, 4, 6-trichloro-1, 3, 5-triazine (18.4 g, 0.1mole) dissolved in acetone (100ml) cooled at 0oC, 2-amino-6-chloro-benzothiazole (17.05g, 0.1mole) dissolved in acetone (100ml) was added with stirring at 0-5oC followed by dropwise addition of sodium hydroxide (4.0g, 0.1mole) in water (50ml). Contents were stirred for 3 hrs and poured into ice water acidified with dilute HCl, filtered, washed, dried and recrystallized from ethanol, m.p. 210oC, yield (78 %).2,6-

       

Chlorobenzothiazol-2’-yl amino-4-(2-chloro-4-trifluoromethyl phenyl thioureido)-6-chloro-1, 3, 5-triazine IV. Compound II (33.2g, 0.1mole) dissolved in acetone (100ml) was added to 2-Chloro-4-trifluoromethyl Phenylthiourea (25.4g, 0.1mole) in acetone (100ml) slowly with constant stirring followed by addition of sodium hydroxide (4.0g, 0.1mole) in water (50ml) and stirred for 3 hrs at 30-40oC poured in ice water, acidified with dilute HCl, filtered washed, dried and recrystallized from ethanol, m.p. 175oC, yield 75%. 

       

2-(6-Chlorobenzothiazol-2’-yl amino)-4-(2-chloro-4-trifluoromethyl phenyl thioureido)-6-(p-fluorophenyl thioureido)-1, 3, 5-triazine VIa. 

To compound IV (5.18 g, 0.01mole) in acetone (50ml) was added p-fluorophenyl thiourea (1.6 g, 0.01 mole) and sodium hydroxide (0.01mole) in water (10ml) refluxed at 85-90oC for 2 hrs.

The contents were poured into ice water, filtered, dried and recrystallized from ethanol, m.p. 178oC, yield 74 %.

       

R = 4-FC6H4,  2-FC6H4,  2-NO2-C6H4,  2-OCH3C6H4,

4-Cl C6H4, CH2=CH-CH2, C6H5,  NH2

Scheme-I

       

       

RESULTS AND DISCUSSION

IR spectra of 2-(6-Chlorobenzothiazol-2’-yl amino)-4, 6-dichloro 1, 3, 5-triazine II shows significant characteristic absorption band in the region of νmax 3200 (>NH) cm–1, 1HNMR (CDCl3): δ 9.0 (s, 1H, >NH), 6.5-6.8 (m, 3H, aromatic) ppm. In mass spectrometry of IIa (m/z): 332.5 (M+) was observed. (Found C, 36.00; H, 1.18; N, 21.00; S, 9.60; C10H4N5SCl3 requires C, 36.09; H, 1.20; N, 21.05; S, 9.62 %);

       

IR spectra of 2,6-Chlorobenzothiazol-2’-yl amino-4-(2-chloro-4-trifluoromethyl phenyl thioureido)-6-chloro-1, 3, 5-triazine IV shows  significant characteristic absorption band in the region of νmax: 3160 (>NH) 1120 (thioureido CS), 740 (C–Cl) cm–1. 1HNMR: δ 4.80 (s, 2H, >NH CS NH), 9.5 (s, 1H, >NH), 6.5-7.2 (m, 8H, aromatic) ppm. MS (m/z): 518.5 (M+) IVa (Found C, 39.20; H, 1.60; N, 17.77; S, 11.60 C18H9N7S2Cl3F3 requires C, 39.23; H, 1.63; N, 17.80; S, 11.62 %); 

IR spectra of 2-(6-Chlorobenzothiazol-2’-yl amino)-4-(2-chloro-4-trifluoromethyl phenyl thioureido)-6-(p-fluorophenyl thioureido)-1, 3, 5-triazine VIa shows significant characteristic absorption band in the region of νmax: 3130 (>NH), 1115 (thioureido CS) cm–1, 1HNMR: δ 4.90 (s, 4H, 2 x NHCSNH), 10.20 (br, 1H, >NH), 6.85-7.45 (m, 12H, Ar-H) ppm. MS (m/z): 684 (M+). (Found: C, 43.82; H, 2.17; N, 10.29; S, 18.40. C25H15N9S3F4Cl2 requires C, 43.85; H, 2.19; N, 10.31; S, 18.42).

Compounds VIb-h were prepared similarly. Their physical and analytical data are recorded in Table-I.

Table – I

Compound

R

Mol. Formula

M.P.oC

Yield (%)

Found/(Calculated) %

C

H

N

S

VIa

4-FC6H4

C25H15N9S3F4Cl2

178

74

73.82 (73.85)

2.17 (2.19)

10.29 (10.31)

18.40 (18.42)

VIb

2-FC6H4

C25H15N9S3F4Cl2

182

72

43.80 (43.85)

2.16 (2.19)

10.28 (10.31)

18.39 (18.42)

VIc

2-NO2C6H4

C25H15N10Cl2S3O2F3

160

68

42.15 (42.19)

2.07 (2.10)

10.36 (10.38)

19.65 (19.69)

VId

2-OCH3C6H4

C26H18N9Cl2S3OF3

194

71

43.82 (43.85)

2.61 (2.63)

18.08 (18.10)

13.77 (13.79)

Vie

4-ClC6H4

C25H15N9Cl3S3F3

192

70

42.80 (42.80)

2.12 (2.14)

9.52

(9.54)

17.96 (17.98)

VIf

CH2=CH-CH2

C22H16N9Cl2S3F3

173

65

41.88 (41.90)

2.50 (2.53)

9.85

(9.88)

19.96 (20.00)

VIg

C6H5

C25H16N9Cl2S3F3

170

69

45.00 (45.04)

2.37 (2.40)

10.09 (10.11)

18.89 (18.91)

VIh

NH2

C19H13N10Cl2S3F3

165

73

37.65 (37.68)

2.10 (2.14)

10.60 (10.62)

23.10 (23.14)

       

Table-II

Fungicidal screening data of 2-(6-chlorobenzothiazol-2’-yl amino)-4-(2-chloro-4-trifluoromethyl phenyl thioureido)-6-(substituted thioureido)-1, 3, 5-triazine

Compound

Average % inhibition of spore germination after 72 hrs

Alternaria Alternata Concentration (ppm)

Aspergillus Niger Concentration (ppm)

Macrophomina Concentration (ppm)

100

500

1000

100

500

1000

100

500

1000

VIa

35

50

72

30

50

71

32

50

72

VIb

34

49

70

33

47

72

32

48

72

VIc

31

42

65

28

40

61

30

38

64

VId

32

36

60

32

45

70

31

35

68

Vie

30

35

62

33

44

69

32

37

61

VIf

30

38

68

31

44

67

30

35

69

VIg

31

37

55

30

42

64

31

34

66

VIh

32

35

68

30

43

67

31

35

67

       

       

       

       

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Graphical Abstract

       

       

Synthesis of 2- (6 -chlorobenzothiazol-2’-yl amino) -4- (2-chloro-4-trifluoromethyl phenyl thioureido)-6-(substituted thioureido)-1,3,5-triazine as antifungal agents

       

Vineeta Sareen, Vineeta Khatri and Prakash Jain

       

Department of Chemistry, University of Rajasthan,

Jaipur-302004, Rajasthan

e-mail:  sareenparmod@yahoo.com

       

2,4, 6-Trichloro-1,3,5-triazine has been reacted selectively with nucleophilic reagents, 2-amino -6- chlorobenzothiazole I, and then the product II so obtained is reacted with 2-chloro -4- trifluoromethyl phenyl thiourea III to give IV and then IV is reacted with different substituted thioureas V to give 2-(6-chlorobenzothiazol - 2’-yl amino) -4- (2- chloro -4- trifluoromethyl phenyl thioureido) -6-(substituted thioureido)-1, 3, 5-triazine VI. These compounds are evaluated for their antifungal activity and shown promising results. The structures of all these compounds have been confirmed by IR, 1HNMR, mass spectral data and elemental analysis.