Synthesis and biological activities of some new phenothiazines, their sulfones, and ribofuranosides

Article abstract of DOI:10.1080/10426500701544557

The present communication describes the synthesis of substituted 10H-phenothiazines by reaction of 2-aminobenzenethiol 1 and o-halonitrobenzene 2 via Smiles rearrangement. These synthesized phenothiazines are used as base to prepare ribofuranosides by tre

Full text of DOI:10.1080/10426500701544557

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Phosphorus, Sulfur, and Silicon
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Synthesis and Biological
Activities of Some New
Phenothiazines, Their
Sulfones, and Ribofuranosides
Rahul Dixit a , Yogesh Dixit a , D. C. Gautam a &
Naveen Gautam b
a Department of Chemistry, University of Rajasthan,
Jaipur, India
b L.B.S. Govt. P.G. College, Kotputli, Jaipur, India
Published online: 20 Feb 2008.
To cite this article: Rahul Dixit , Yogesh Dixit , D. C. Gautam & Naveen Gautam
(2007): Synthesis and Biological Activities of Some New Phenothiazines, Their
Sulfones, and Ribofuranosides, Phosphorus, Sulfur, and Silicon and the Related
Elements, 183:1, 1-12
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Phosphorus, Sulfur, and Silicon, 183:1–12, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701544557
Synthesis and Biological Activities of Some New
Phenothiazines, Their Sulfones, and Ribofuranosides
Rahul Dixit,1 Yogesh Dixit,1 D. C. Gautam,1
and Naveen Gautam2
1Department of Chemistry, University of Rajasthan, Jaipur, India
2L.B.S. Govt. P.G. College, Kotputli, Jaipur, India
The present communication describes the synthesis of substituted 10H-
phenothiazines by reaction of 2-aminobenzenethiol 1 and o-halonitrobenzene 2
via Smiles rearrangement. These synthesized phenothiazines are used as base to
prepare ribofuranosides by treatment with sugar viz. β-D-ribofuranosyl-1-acetate-
2,3,5-tribenzoate. Sulfones are also synthesized by oxidation of 10H-phenothiazines
refluxing with H2O2 in glacial acetic acid. All synthesized compounds have been
1
13
characterized by IR, H NMR, C NMR Mass spectra and elemental analysis and
screened for antioxidant and antimicrobial activity.
Keywords Antimicrobial activity; antioxidant activity; glacial acetic acid; 10H-
phenothiazines; ribofuranosides
INTRODUCTION
In the present age of pharmacognestic too, the 10H-phenothiazines
have been given considerable interest due to a wide spectrum of biolog-
ical activities such as antihistaminic, antitussive, analgesic, antibac-
terial, calcium antagonist, anticancer, and anti AIDS. Research is also
being persuaded to develop potent anticancer agent. A slight change
in substitution pattern in phenothiazines nucleus causes distinguish-
able difference in their biological activities.1–12 Thus, we wish to report
here synthesis of some new 10H-phenothiazines their ribofuranosides
Received 17 May 2007; accepted 18 June 2007.
The authors are thankful to Head, Department of Chemistry of University of
Rajasthan, for providing necessary facilities. Thanks are due to UGC Bhopal for financial
support. Thanks are also due to SAIF, CDRI Lucknow for providing 13C NMR and Mass
spectra.
Address correspondence to Rahul Dixit, Department of Chemistry, University of
Rajasthan, Jaipur 302004, India. E-mail: rahuldixit uor@yahoo.co.in
1

2
R. Dixit et al.
and sulfones and subjected these compounds for antimicrobial13,14 and
antioxidant activity.15
RESULT AND DISCUSSION
Synthesis of 10H-phenothiazines 5b,d,e have been carried
out by Smiles rearrangement of substituted 2-formamido-2ꢀ-
nitrophenylsulfides 4,b,d,e, which have been synthesized by diphenyl
sulfide 3b,d,e, which in turn was prepared by condensation of
2-aminobenzenethiols 1 and o-halonitrobenzene 2a in ethanolic an-
hydrous sodium acetate solution. 1-nitro-10H-phenothiazines 5a,c
have been synthesized by condensation of 2-aminobenzenethiols 1 and
reactive o-halonitrobezene 2b (which have either two nitro group or
one halo and one nitro group at both ortho position to reactive halogen
atom) in alcohol in presence of sodium hydroxide where the Smiles
rearrangement occur in situ. Compound 5a–e on refluxing with 30%
hydrogen peroxide in glacial acetic acid yield phenothiazines sulfones
6a–e. The pasty mixture of 5a–b in toluene, on stirring with sugar viz.
β-D-ribofuranosyl-1-acetate-2,3,5-tribenzoate at 155–160 for 10 h in
vacuo gave corresponding ribofuranosides 7a–b (Scheme-1).
IR Spectra
All the synthesized diphenyl sulfides 3b,d,e shows two peaks in the
–1
–1
region 3395–3360 cm and 3310–3260 cm due to asymmetric and
symmetric vibration of NH2 group. Two signals are observed in the
region 1600–1570 cm–1 and 1370–1345 cm–1 are ascribed for asymmet-
ric and symmetric vibration of nitro group, respectively.
2-Formamido-2ꢀ-nitrophenylsulfides 4b,d,e shows absorption in the
–1
region 3300–3260 cm is ascribed for >N H stretching vibrations
–1
and an additional peak observed in the region 1690–1650 cm due to
>C O stretching vibration. Absorption in the region 1565–1540 cm
and 1345–1330 cm can be assigned for asymmetric and symmetric
–1
–1
vibration of nitro group, respectively.
Compounds 5a–e and 6a–e showed a band in the region 3435–3320
–1
cm due to >NH stretching vibration. The sharp absorption bands
appeared in the region 1560–1535 and 1365–1345 cm–1, were due to
asymmetric and symmetric stretching vibration of NO2 group in 5a,c,
6a–c, and 7a. Compounds 6a–e exhibit two intense peak in the region
–1
–1
1365–1345 cm and 1180–1110 cm can be assigned to asymmetric
and symmetric vibration of sulfonyl group.

3

4
R. Dixit et al.
In compound 7, the >NH band vanished completely, suggesting its
ribosylation. The band due to >C O and C O C appeared at 1760–
1750 cm−1 and 1165–1080 cm−1, respectively.
1H NMR Spectra
1H NMR spectra of 3b,d,e and 4b,d,e show resemblance with their
corresponding phenothiazine 5b,d,e. Instead of this resemblance com-
pound, 3b,d,e, show a broad signal in the region δ 4.24–3.88 ppm due to
–NH2 proton. Compound 4b,d,e exhibit a signal in the region δ 10.24–
9.86 ppm due to formyl proton and another signal observed in the region
δ 8.74–8.92 ppm due to >NH proton.
Compound 5a–e and 6a–e exhibit singlet in the region δ 9.66–8.82
ppm due to >N–H proton. multiplet observed in the region δ 8.48–
6.12 ppm corresponding to phenylic protons. Compound 5a, 6a, and 7a
exhibited doublet and multiplet in the region δ 1.36–1.27 ppm and δ
2.92–2.60 due to (CH3)2 and CH proton of isopropyl group. In ribofura-
noside 7 the signal due to >NH proton vanished completely, suggesting
its ribosylation. Aromatic proton of ribofuranosides 7a–b gave multi-
plet in the region δ 8.20–6.92. Cꢀ4–H and >CH2 proton of sugar moiety
gave multiplet in the region δ 4.42–4.80, while Cꢀ2–H and C3ꢀ –H signals
appeared in the region δ 5.62–5.83 as multiplet. The singlet at δ 6.40 is
attributed to Cꢀ1–H.
13C NMR of the Synthesized Compounds (Solvent Used CDCl3)
5a δ145.2(C9), 122 (C8), 126.3 (C7), 121.4 (C6), 130.5 (C4) 119.2 (C3),
122 (C2), 144.4 (C1).
5b δ116.4(C9), 154.3 (C8), 118.6 (C7), 125.7 (C6), 118 (C4) 138.6 (C3),
116.6 (C2), 115 (C1).

Phenothiazines, Their Sulfones, and Ribofuranosides
5
5c δ118(C9), 150.7 (C8), 119.4 (C7), 122.6 (C6), 118.7 (C4) 135.2 (C3),
112.4 (C2), 145.3 (C1).
5d δ120.3(C9), 152.8 (C8), 119 (C7), 126.2 (C6), 122 (C4) 132.4 (C3),
112.2 (C2), 118.2 (C1).
5e δ117(C9), 150.2 (C8), 120 (C7), 125.2 (C6), 124 (C4) 127.4 (C3),
124.4 (C2), 126 (C1).
7a δ146.1(C9), 123.4 (C8), 125.2 (C7), 121.8 (C6), 139.3 (C4) 118.8
(C3), 113.2 (C2), 144.9 (C1), 96.2 (Cꢀ1). 82.68. 81.26 (Cꢀ2–C3ꢀ ), 92.9
(C-4ꢀ).
7b δ117.2(C9), 155.2 (C8), 118.4 (C7), 125.2 (C6), 117.6 (C4) 139.2
(C3), 117 (C2), 115.8 (C1), 95.6 (Cꢀ1). 83.02. 88.56 (Cꢀ2–C3ꢀ ), 94.8
(C-4ꢀ).
Mass Spectra
In mass spectra of 1-nitro-10H-phenothiazines molecular ion peak are
in accordance with their molecular weights. Moieties M+–30, M+–46
and M+–47 are observed and ascribed to the loss of NO, NO2 and HNO2,
respectively.
1-Nitro-10H-phenothiazines undergo fragmentation yielding M+–17
due to the loss of OH radical by McLafferty rearrangement.16,17
SCHEME 2 Optical rotation data of compound 7a-b.
Compound 7a +24.3 (α)D24
Compound 7b −17.73 (α)D24
EXPERIMENTAL
Melting point of all the synthesized compound were determined
on an electrothermal apparatus (capillary method) and are un-
corrected. IR spectra were recorded in KBr on SHIMADZU 8400
S FTIR spectrophotometer; and 1H NMR and 13C NMR spec-
tra on JEOL AL 300 FT NMR using TMS as internal stan-
dard in CDCl3/DMSO-d6 (Table 1). Mass spectra were recorded
on JEOL SX 102/DA 6000 using Argon/Xenon as FAB gas.

6

Phenothiazines, Their Sulfones, and Ribofuranosides
7
TLC were performed using silica gel ‘G’ and the spots were visualized
by exposure to iodine vapors.
Synthesis of 2-Amino-2’-nitrodiphenylsulfides 3b,d,e
2-aminobenzenethiol 1 (0.01 mol) was dissolved in ethanol (20 ml) con-
taining (0.01 mol) of anhydrous sodium acetate in 50 ml R.B. Flask
and o-halonitrobenzene 2 (0.01 mol) in 10 ml ethanol was added. The
reaction mixture was refluxed for 4–5 h. The resultant solution was
concentrated, cooled, and kept overnight in an ice chamber overnight.
The solid separated out was filtered, washed with 30% ethanol and
recrystallized from methanol.
Synthesis of 2-Formamido-2’-nitrodiphenylsulfides 4b,d,e
The diphenylsulphides 3 (0.01 mol) was refluxed for 4 hrs. in 90% formic
acid (20 ml). The content were then poured into a beaker containing
crushed ice, a solid separated out was filtered, washed with water until
the filtrate was neutralized and crystallized from benzene.
Synthesis of Phenothiazines 5b,d,e
To a refluxing solution of formyl derivatives 4 (0.01 mol) in acetone
(15 ml) was added an alcoholic solution of potassium hydroxide (0.2 g
in 5 ml ethanol). These contents were heated for 30 min. A second lot
of potassium (0.2 g in 5 ml ethanol) was added to the reaction mixture
and refluxed for 4 h. The contents were poured into beaker containing
crushed ice and filtered. The residue obtained was repeatedly washed
with cold water and finally with 30% ethanol and then crystallized from
benzene.
Synthesis of 1-Nitro-10H-phenothiazine 5a,c
Mixture of (0.01 mol) of substituted 2-aminobenzenethiol 1, sodium hy-
droxide (0.01 mol) and 20 ml absolute alcohol were taken in a 50 ml R.B.
A flask fitted with a reflux condenser and was heated for 5 min; 0.01
mol of substituted reactive o-halonitrobenzene 2b (which contained two
nitro groups or one nitro and one halogen group at both ortho position
to halogen atom) was added with stirring to this solution. These con-
tents were refluxed for 4 h. The reaction mixture was concentrated on
water bath, cooled, and filtered. The precipitate was washed well with
hot water and finally with 20% alcohol and crystallized from acetone.

8
R. Dixit et al.
Synthesis of Phenothiazine Sulfones 6a–e
A mixture of substituted phenothiazines 5 (0.01 mol), 20 ml of glacial
acetic acid and 5 ml of 30% hydrogen peroxide was refluxed for 15 min.
Heating was stopped and another lot of hydrogen peroxide (5 ml) was
added. The reaction mixture was again refluxed for 3 hrs. The con-
tent was poured in a beaker containing crushed ice. The yellow residue
obtained was filtered and washed with water and recrystallized with
ethanol.
Synthesis of Substituted N-(2’,3’,5’-Tri-o-benzoyl)-β-
D-ribofuranosyl Phenothiazines 7a,b
β-D-ribofuranose-1-acetate-2,3,5-tribenzoate (0.002 mol) was added to
a concentrated solution of 5 (0.002 mol) in toluene and stirred, in vacuo,
on an oil both, at 155–160◦C, for 15 min. The vacuo was broken and the
reaction was protected from moisture, by using a guard tube. Stirring
was further continued for 10 h. with application of vacuum for 15 min af-
ter every h. The viscous mass thus obtained was dissolved in methanol,
boiled for 10 min, and cooled to room temperature. The reaction mixture
was filtered. The methanol was removed by distillation under reduced
pressure. The viscous residue thus obtained was dissolved in ether,
filtered, concentrated and kept in a refrigerator overnight to get crys-
talline ribofuranoside.
Physical data of synthesized compounds 5a–e, 6a–e, and 7a–b have
been recorded in Table II.
BIOLOGICAL ACTIVITY
Antioxidant Activity
All the synthesized phenothiazines 5 and their ribofuranosides 7a–b
were screened for their antioxidant activity by 1,1-diphenyl-2-picryl
hydrazyl (DPPH) radial scavenging assay.
The study reveals that ribofuranosides showed better chemopreven-
tive action and antioxidant effect than their respective bases.
DPPH Radical Scavenging Assay
Radical scavenging activity of compound 5a–e and 7a–b against sta-
ble 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical was determined spec-
trophotometerically as described by Cuendet et al.,15 A stock solution
of 1 mg/ml of the compound was prepared in methanol. 50 µl of com-
pounds were added to 5 ml of a 0.004% methanol solution of DPPH. After

9

10
R. Dixit et al.
30 minutes incubation in dark at room temperature. The absorbance
was read against a blank at 517 nm (Table III).
The assay was carried out in triplicate and the percentage of inhibi-
tion was calculated using the following formula:
(AB − AA)
% Inhibiton =
× 100
AB
AB = Absorption of blank
AA = Absorption of test
(1)
Inhibition (%) of DPPH radical scavenging activity of various com-
pounds at particular concentration. Stock solution of crude compound
was prepared as 1 mg/ml in methanol. Fifty microliters of sample of
particular concentration were added to 5 ml of 0.004% methanol solu-
tion of DPPH. After 30 min incubation in dark room temperature, the
absorbance was read against a blank at 517 nm.
Antimicrobial Activity
Newly synthesized compounds 5a–e, 6a–e, and 7a–b were screened for
their antibacterial activity against Staphyllococcus aureus and Pseu-
domonas fluorescence bacterial strain by paper disc method using Strep-
tomycin as standard drugs. Compounds are also screened for their an-
tifungal activity against Aspergillus flavus and Aspergillus niger. The
activity of each compound was compared with that of flukanozole as a
standard drug. The results of such studies are given in Table IV. An-
timicrobial activities are given in term of activity index
Inhibition diameter of test compound
Activity index =
Inhibition diameter of standard
TABLE III Antioxidant Activity of Compound
5a–e and 7a–b
DPPH% inhibition of 1 mg/ml
Compound
1 mg/ml of the compound
5a
5b
5c
5d
5e
7a
7b
42.62 0.09
22.04 0.8
56.08 0.07
38.02 0.03
18.86 1.2
58.03 0.06
36.09 0.04

Phenothiazines, Their Sulfones, and Ribofuranosides
11
TABLE IV Antimicrobial Activity of Compounds 5a–e, 6a–e, and 7a–b
Antibacterial activity Antifungal activity
Compound
no.
R1
R2 R3 R4 R5 S. aureus P. fluorescens A. niger A. flavus
5a
5b
5c
5d
5e
6a
6b
6c
6d
6e
7a
7b
(CH3)2CH
H
F
F
F
F
H
F
F
F
F
H
F
H
H
H
H
H
H
H
H
H
H
H
H
NO2
H
NO2 Cl
H
H
NO2
H
NO2 Cl
H
H
NO2
H
H
Br
1.06
0.92
0.95
1.08
0.92
0.95
0.94
0.89
0.90
1.12
1.02
1.18
0.92
0.94
1.00
0.92
1.06
0.88
0.94
1.02
0.92
0.90
1.12
1.20
0.86
1.02
0.92
0.94
0.90
0.88
1.10
0.92
0.84
1.06
1.23
1.06
0.90
0.86
0.96
1.10
0.92
0.90
0.88
0.96
0.86
0.88
1.08
1.02
H
H
H
H
Cl
H
H
(CH3)2CH
H
H
H
Br
Cl
H
H
H
(CH3)2CH
H
Br
Antimicrobial activities are given in term of activity index.
Inhibition diameter of test compound
Activity index =
.
Inhibition diameter of standard
CONCLUSION
The structures proposed to the synthesized compounds are well sup-
ported by spectroscopic data and elemental analysis. All the synthe-
sized phenothiazines 5 and their ribofuranosides 7a–b were screened
for their antioxidant activity by 1,1-diphenyl-2-picryl hydrazyl (DPPH)
radial scavenging assay.
The present study demonstrated that the synthesized compound
showed mixed radical scavenging activity in DPPH assay.
(a) Compound (5c, 7a) showed strong radical scavenging activity in
DPPH assay that have DPPH% inhibition ≥50.
(b) Compound (5a, 5d, 7b) showed moderate radical scavenging activity
in DPPH assay that have DPPH% inhibition ≥30.
(c) Compound (5b, 5e) showed mild radical scavenging activity in
DPPH assay that have DPPH% inhibition ≤30.
The antimicrobial and antioxidative studies reveals that almost in
all cases ribofuranosides showed better antimicrobial activity, chemo-
preventive action and antigenotoxic effect than their parent bases. All
compounds are moderately active against various bacteria and fungus.
REFERENCES
[1] W. Ried and W. Ochs, Physical Methods in Heterocyclic Chemistry, In RR Gupta
(Ed.) (John Wiley and Sons Inc.: New York, 1984) p. 58.

12
R. Dixit et al.
[2] R. R. Gupta, Ed., Phenothiazines and 1,4-Benzothiazines Chemical and Biomedical
Aspects (Elsevier, Amsterdam, 1988).
[3] C. S. Rasmussen, U.S. Patent, 3,476,749(1969); Chem. Abstr. 72, 217,227 (1970).
[4] H. Zenno and T. Milutani, Japanese Patent, 7,006,262 (1970); Chem. Abstr., 72,
132,759 (1970).
[5] G. Fengler, D. Arlt, K. Grothe, H. J. Zeiter, and K. Metzger, German Offen., 3, 229,
125 (1984); Chem. Abstr., 101, 7176 (1984).
[6] E. D. Clercq, Nucleosides and Nucleotides, 4, 3 (1985).
[7] G. Filocchioni, V. Nacci, and G. Stfancich, Farmaco, Ed. Sci. 31(7), 478 (1976); Chem.
Abstr. 85, 143,048 (1976).
[8] N. Gautam, R. Gupta, D. C. Gautam, and R. R. Gupta, Heterocycl. Commun., 6, 369
(2000).
[9] P. R. Sharma, R. Gupta, V. Gupta, D. C. Gautam, and R. R. Gupta, Heterocycl.
Commun., 8, 549 (2002).
[10] G. Singh, N. Kumar, A. K. Yadav, and A. K. Mishra, Heteroatom. Chemistry, 14(6),
481–486 (2003).
[11] N. Gautam and D. C. Gautam, In. J. Chem. Sci., 2(1), 84–87 (2004).
[12] N. Gautam, D. Hans, and D. C. Gautam, Oriental Journal of Chemistry, 21(2), 299–
302 (2005).
[13] J. C. Gould and J. H. Browie, Edinb. Med. J., 59, 178 (1950).
[14] C. H. Collin and P. M. Lyne, Microbial Methods (University Park Press, Baltimore,
1970).
[15] M. Cuendet, K. Hostemann, and O. Potteral, Hel. Chem. Acta, 80, 1144, 1152 (1997).
[16] F. W. Mc-Lafferty, Ed., Mass Spectrometry of Organic Ions (Academic Press, New
York, 1963).
[17] F. W. Mc-Lafferty, Anal. Chem., 31, 82 (1959).