Synthesis of mixed aryl 2,3-diarylsulphanyl-1,4-naphthoquinones

Article abstract of DOI:10.1080/00397910802528951

The reaction of 2-arylsulphanyl-1,4-napththoquinone with aromatic thiols and sodium dithionate leads to bis-2,3-(arylsulphanyl)naphthalene-1,4-diols in high yield. Corresponding oxidized products, namely 2,3-diarylsulphanyl-1,4- naphthoquinones, are prepa

Full text of DOI:10.1080/00397910802528951

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Synthesis of Mixed Aryl
2,3-Diarylsulphanyl-1,4-
naphthoquinones
W. Marjit Singh a & Jubaraj B. Baruah a
a Department of Chemistry , Indian Institute of
Technology , Guwahati, India
Published online: 19 Mar 2009.
To cite this article: W. Marjit Singh & Jubaraj B. Baruah (2009) Synthesis of Mixed
Aryl 2,3-Diarylsulphanyl-1,4-naphthoquinones, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 39:8,
1433-1442, DOI: 10.1080/00397910802528951
To link to this article: http://dx.doi.org/10.1080/00397910802528951
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Synthetic Communications1, 39: 1433–1442, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802528951
Synthesis of Mixed Aryl 2,3-Diarylsulphanyl-
1,4-naphthoquinones
W. Marjit Singh and Jubaraj B. Baruah
Department of Chemistry, Indian Institute of Technology,
Guwahati, India
Abstract: The reaction of 2-arylsulphanyl-1,4-napththoquinone with aromatic
thiols and sodium dithionate leads to bis-2,3-(arylsulphanyl)naphthalene-1,4-
diols in high yield. Corresponding oxidized products, namely 2,3-diarylsulpha-
nyl-1,4-naphthoquinones, are prepared in near quantitative yield by a copper(II)-
catalyzed aerial oxidation reaction of bis-2,3-(arylsulphanyl)naphthalene-1,4-
diols under mild condition.
Keywords: Bis-2,3-(arylsulphanyl)naphthalene-1,4-diols, C–S bond formation,
2,3-diarylsulphanyl-1,4-naphthoquinone, oxidation reactions
INTRODUCTION
2-Arylsulphanyl-1,4-naphthoquinones are used as medicine.[1–6] They can
be prepared by reactions of thiols on 1,4-naphthoquinone.[7–17] Depending
on the stoichiometry of reactants, disubstituted derivatives of naphthoqui-
none are prepared.[18,19] The reaction of thiols with 1,4-naphthoquinone by
potassium fluoride (KF)=Celite[7] and PdCl2[18] and without a reagent[19] in
refluxing ethanol leads to 2,3-diarylsulfanyl-1,4-naphthoquinones or
2-arylsulphanyl-1,4-naphthoquinone. A recent report suggests the utility
of mixed 2,3-diarylsulphanylnaphthalene-1,4-diols as antifugal agents,
but the synthetic procedures of the compounds are not disclosed.[20]
Moreover, most of the literature reports on the simple 2,3-diarylsulphanyl-
naphthalene-1,4-diols lack spectroscopic or other related data.[18,19] It may
Received July 16, 2008.
Address correspondence to Jubaraj B. Baruah, Department of Chemistry,
Indian Institute of Technology, Guwahati 781 039, India. E-mail: juba@iitg.ernet.in
1433

1434
W. M. Singh and J. B. Baruah
be mentioned that the introduction of two different thiol substituents on
the ring of 1,4-naphthoquinone would lead to a new class of quinone com-
pounds. We describe here the synthesis of different 2,3-diarylsulphanyl-
1,4-naphthoquinones via 2,3-diarylsulphanylnaphthalene-1,4-diols that
are prepared from the reaction of aromatic thiols on 2-arylsulphanyl-1,4-
naphthoquinones. The 2,3-diarylsulphanylnaphthalene-1,4-diols are also
oxidized by copper(II) acetate monohydrate–catalyzed aerial oxidation
reactions.
RESULTS AND DISCUSSION
The reaction of 2-arylsulphanyl-1,4-naphthoquinones with various
aromatic thiols followed by reaction with sodium dithionate gave the
corresponding 2,3-diarylsulphanylnaphthalene-1,4-diols in high yield.
The method is also useful for synthesis of symmetric as well as unsymme-
trical 2,3-diarylsulfanylnaphthalene-1,4-diols (Scheme 1). Although com-
pound 1 is reported in literature, the detailed synthesis of it is not
available.[20] The reaction of 1,4-naphthoquinone with thiophenol by
potassium fluoride and Celite was reported earlier,[7] which gives 2,3-
diarylsulphanyl-1,4-naphthoquinones in low yields along with mono-sub-
stituted derivative. However, we have observed that our reaction depicted
in Scheme 1 gives exclusively bis-2,3-arylsulfanylnaphthalene-1,4-diols.
The use of sodiumdithionate in the reaction acts as a reducing agent of
the carbonyl groups that may be formed through ariel oxidation of the
products and provides a good method to isolate the diol products. The
sodium metabisulphite,[21,22] and sodium dithionate[23,24] are often used
for reduction of aromatic quinonic compounds to diols. The bis-2,3-
arylsulphanylnaphthalene-1,4-diols can be prepared directly by stirring
a methanol solution of aromatic thiol with 1,4-naphthoquinone for
few hours; however, in such reactions the product undergoes slow
oxidation to corresponding quinonic derivative and requires purification.
The other important aspect of these reactions is the ease at which the
Scheme 1. R ¼ C6H5-, R0 ¼ C6H5- (1); R ¼ 4-CH3C6H4-, R0 ¼ 4-CH3C6H4- (2);
R ¼ 4-CH3OC6H4-, R0 ¼ 4-CH3OC6H4- (3); R ¼ 4-BrC6H4-, R0 ¼ 4-BrC6H4; (4);
R ¼ C6H5-, R0 ¼ 4-CH3C6H4- (5); R ¼ C6H5-, R0 ¼ 4-CH3OC6H4- (6); R ¼ 4-
CH3C6H4-, R0 ¼ 4-CH3OC6H4- (7); R ¼ 4-CH3C6H4-, R0 ¼ 4-BrC6H4- (8).

Bis-2,3-arylsulfanyl-1,4-naphthoquinones
1435
Scheme 2. R ¼ C6H5-, R0 ¼ C6H5- (9); R ¼ 4-CH3C6H4-, R0 ¼ 4-CH3C6H4- (10);
R ¼ 4-CH3OC6H4-, R0 ¼ 4-CH3OC6H4- (11); R ¼ 4-BrC6H4-, R0 ¼ 4-BrC6H4 (12);
R ¼ C6H5-, R0 ¼ 4-CH3C6H4- (13); R ¼ C6H5-, R0 ¼ 4-CH3OC6H4- (14); R ¼ 4-
CH3C6H4-, R0 ¼ 4-CH3OC6H4- (15); R ¼ 4-CH3C6H4-, R0 ¼ 4-BrC6H4- (16).
2-arylsulphanyl-1,4-naphthoquinones can be prepared from 1,4-naphtho-
quinone,[18] which are used as starting materials in these reactions.
The bis-2,3-arylsulphanylnaphthalene-1,4-diols can be easily oxi-
dized by warming their methanol solutions (Scheme 2) with a catalytic
amount of copper(II) acetate monohydrate (10 mol%) under aerobic
conditions. Several bis-2,3-arylsulphanyl-naphthalene-1,4-diols were
oxidized by applying this oxidation procedure (Scheme 2).
The copper(II) complexes are known to oxidize hydroquinones.[25,26]
Among these, CuSO4 with alumina as a catalyst was used for oxidation of
hydroquinone in air.[26] Our compounds (1–4) also can be oxidized by
CuSO4 along with alumina as catalyst. The advantages of the oxidation
by copper(II) acetate as a catalyst for oxidation of these substrates are
the mild reaction conditions and the formation of near quantitative yield
without use of a solid support. The yields and the spectroscopic details
of the products are listed in the experimental section. The oxidation
reactions reported here do not lead to the C-S bond cleavage or over-
oxidation to form corresponding sulphoxide derivatives, and the workup
procedures for these reactions are also very simple.
In conclusion, we have developed the existing C-S bond formation
reactions on 1,4-naphthoquinones to a convenient method for synthesis
of bis-2,3-arylsulphanylnaphthalene-1,4-diols and their oxidation to
2-arylsulphanyl-1,4-naphthoquinones.
EXPERIMENTAL
The 2-arylsulphanyl-1,4-naphthoquinones were synthesized by a reported
procedure.[21,22]
Synthesis of 2,3-Diarylsulphanylnaphthalene-1,4-diols from
2-Arylsulphanyl-1,4-naphthoquinones
A solution of arylthiol and 2-arylsulphanyl-1,4-naphthoquinone (1 mmol
each) in dichloromethane (20 ml) was stirred at room temperature for 4 h.

1436
W. M. Singh and J. B. Baruah
The solution was evaporated under reduced pressure. A solution of
sodium dithionate (2 mmol) in water (20 ml) was added, followed by ethy-
lacetate (10 ml), to the crude product. The mixture was stirred for 2 h.
The organic layer was separated and washed several times with water
(10 ml each), and the products were obtained from the organic layer by
crystallization.
Spectroscopic Data for Mixed 2,3-Diarylsulphanyl-1,4-naphthalenediols
2,3-Diphenylsulphanyl-1,4-naphthalenediol (1)
Yield 91%; mp 149 ꢀC. Elemental anal. calcd. for C23H18O2S2: C, 70.74;
H, 4.65. Found: C, 70.73; H, 4.63. 1H NMR (400 MHz, CDCl3): 8.31 (m,
2H), 7.65 (m, 2H), 7.19 (s, 1H), 7.17 (s, 1H), 7.09 (m, 4H), 6.99 (m, 2H),
6.93 (m, 3H), 2.23 (s, 3H). IR (KBr, cmꢁ1): 3406 (bs), 3053 (w), 2919 (w),
1629 (w), 1573 (s), 1486 (w), 1434 (w), 1399 (s), 1260 (s), 1158 (w), 1081
(w), 1020 (w), 892 (s), 805 (w), 769 (w), 738 (w), 692 (w), 656 (w), 559 (w),
497 (w), 431 (s). UV-vis (k max, CH3CN) 341, 357 nm (1.23 ꢂ 104 and
1.31 ꢂ 104 molꢁ1 dm3 cmꢁ1).
2,3-Di-(4-methylphenyl)sulphanyl-1,4-naphthalenediol (2)
Yield 90%; mp 82ꢀC. Elemental anal. calcd. for C23H18O3S2: C, 67.96;
1
H, 4.46. Found: C, 67.95; H, 4.48. H NMR (400 MHz, CDCl3): 8.30
(m, 2H), 7.64 (m, 2H), 7.30 (s, 1H), 7.26 (s, 1H), 7.10 (m, 2H), 7.05
(d, J ¼ 8.4 Hz, 2H), 7.00 (m, 3H), 6.65 (d, J ¼ 8.4 Hz, 2H), 3.71
(s, 3H). IR (KBr, cmꢁ1): 3394 (bs), 2938 (w), 2833 (w), 1592 (w),
1568 (s), 1494 (s), 1428 (w), 1398 (s), 1245 (s), 1026 (w), 885 (w), 769
(w), 659 (w). UV-vis (k max, CH3CN) 341, 357 nm (1.33 ꢂ 104 and
1.16 ꢂ 104 molꢁ1 dm3 cmꢁ1).
2,3-Di-(4-methoxyphenyl)sulphanyl-1,4-naphthalenediol (3)
Yield 94%; mp 132ꢀC. Elemental anal. calcd. for C24H20O3S2: C, 68.54;
1
H, 4.79. Found: C, 68.56; H, 4.82. H NMR (400 MHz, CDCl3): 8.29
(m, 2H), 7.63 (m, 2H), 7.17 (s, 1H), 7.14 (s, 1H), 7.01 (m, 2H), 6.92
(m, 4H), 6.64 (m, 2H), 3.70 (s, 3H), 2.23 (s, 3H). IR (KBr, cmꢁ1): 3400
(bs), 2922 (w), 2918 (w), 1578 (s), 1491 (s), 1435 (w), 1395 (w), 1247 (s),
1168 (w), 1082 (w), 1030 (w), 886 (s), 810 (w), 656 (w). UV-vis (k max,
CH3CN) 341, 357 nm (1.28 ꢂ 104 and 1.37 ꢂ 104 molꢁ1 dm3 cmꢁ1).

Bis-2,3-arylsulfanyl-1,4-naphthoquinones
1437
2,3-Di-(4-bromophenyl)sulphanyl-1,4-naphthalenediol (4)
Yield 96%; mp 192ꢀC. Elemental anal. calcd. for C23H17O2S2Br: C, 58.85; H,
3.65. Found: C, 58.83; H, 3.66. 1H NMR (400 MHz, CDCl3): 8.32
(dd, J¼ 9.6, 3.2 Hz, 2H), 7.67 (dd, J ¼ 9.6, 3.2 Hz, 2H), 7.18 (m, 2H), 7.07
(s, 1H), 7.05 (s, 1H), 6.89 (m, 4H), 6.82 (m, 2H), 2.24 (s, 3H). IR (KBr,
cmꢁ1): 3397 (bs), 2918 (w), 1568 (s), 1472 (w), 1397 (s), 1268 (s), 1246 (s),
1080 (s), 1005 (w), 885 (s), 805 (s), 772 (w), 658 (s), 556 (w). UV-vis (k max,
CH3CN) 341, 357nm (1.76 ꢂ 104 and 1.86 ꢂ 104 molꢁ1 dm3 cmꢁ1).
2-(Phenyl)-3-(4-methylphenyl)sulphanyl-1,4-naphthalenediol (5)
Yield 90%; mp 184ꢀC. Elemental anal. calcd. for C22H16O2S2: C, 70.18; H,
4.28. Found: C, 70.20; H, 4.30. 1H NMR (400 MHz, CDCl3): 8.32
(dd, J ¼ 9.6, 3.2Hz, 2H), 7.66 (dd, J¼ 9.6, 3.2 Hz, 2H), 7.12 (s, 2H), 7.08
(m, 6H), 7.01 (m, 4H). IR (KBr, cmꢁ1): 3401 (bs), 3360 (w), 3068 (w), 2366
(w), 1629 (w), 1573 (s), 1475 (w), 1431 (s), 1399 (s), 1255 (s), 1153 (w), 1081
(w), 1015 (w), 886 (s), 738 (s), 692 (w), 656 (w), 559 (w). UV-vis (k max,
CH3CN) 341, 357 nm (1.06 ꢂ 104 and 1.12 ꢂ 104 molꢁ1 dm3 cmꢁ1).
2-(Phenyl)-3-(4-methoxyphenyl)sulphanyl-1,4-naphthalenediol (6)
Yield 92%; mp 158ꢀC. Elemental anal. calcd. for C24H20O2S2: C, 71.25; H,
1
4.98. Found: C, 71.21; H, 4.94. H NMR (400MHz, CDCl3): 8.30 (dd,
J¼ 9.6, 3.6 Hz, 2H), 7.64 (dd, J¼ 9.6, 3.6 Hz, 2H), 7.16 (s, 2H), 6.92 (s,
8H), 2.23 (s, 6H). IR (KBr, cmꢁ1): 3401 (bs), 3345 (w), 2919 (w), 2858 (w),
1573 (s), 1496 (s), 1434 (w), 1399 (s), 1255 (s), 1163 (w), 1086 (w), 1020
(w), 886 (s), 799 (s), 769 (w), 661 (w), 564 (w), 477 (w). UV-vis (k max,
CH3CN) 341, 357nm (1.74 ꢂ 104 and 1.84 ꢂ 104 molꢁ1 dm3 cmꢁ1).
2-(4-Methylphenyl)-3-(4-methoxyphenyl)sulphanyl-1,4-
naphthalenediol (7)
Yield 89 %; mp 156ꢀC. Elemental anal. calcd for C24H20O4S2. C, 66.03;
1
H, 4.62. Found; C, 66.04; H, 4.66. H NMR (400 MHz, CDCl3) 8.28:
(dd, J ¼ 9.6, 3.2 Hz; 2H) 7.63 (dd, J ¼ 9.6, 3.2 Hz, 2H), 7.26 (s, 2H),
7.00 (dd, J ¼ 8,8, 2.4 Hz, 4H), 6.65 (dd, J ¼ 8.8, 2.4 Hz, 4H), 3.71
(s, 6H). IR (KBr, cmꢁ1): 3393 (bs), 2962 (w), 2833 (w), 1593 (w), 1569
(s), 1494 (s), 1463 (w), 1398 (w), 1245 (s), 1180 (w), 1033 (s), 885 (w),
821 (w), 659 (w). UV-vis (k max, CH3CN) 342, 358 nm (0.73 ꢂ 104 and
0.76 ꢂ 104 molꢁ1 dm3 cmꢁ1).

1438
W. M. Singh and J. B. Baruah
2-(4-Methylphenyl)-3-(4-bromophenyl)sulphanyl-
1,4-naphthalenediol (8)
Yield 95%; mp 210ꢀC. Elemental anal. calcd. for C22H14O2S2Br2: C, 49.46;
H, 2.64. Found: C, 49.48; H, 2.63. 1H NMR (400 MHz, CDCl3) 8.32: (dd,
J ¼ 8.8, 3.2 Hz, 2H), 7.69 (dd, J ¼ 8.8, 3.2 Hz, 2H), 7.21 (dd, J ¼ 7.6, 2 Hz,
4H), 7.075 (s, 2H), 6.82 (dd, J ¼ 8.4, 2 Hz, 4H). IR (KBr, cmꢁ1): 3398 (bs),
1569 (s), 1472 (s), 1402 (s), 1268 (w), 1251 (s), 1165 (s), 1080 (w), 1070 (w),
1008 (s), 885 (s), 806 (s), 657 (w), 557 (w). UV-vis (k max, CH3CN) 341,
357 nm (1.71 ꢂ 104 and 1.80 ꢂ 104 molꢁ1 dm3 cmꢁ1).
General Procedure for Oxidation of Bis-2,3-arylsulphanylnaphthalene-
1,4-diol
Copper(II) acetate monohydrate (0.017g, 0.1 mmol) was added to a
solution of bis-2,3-arylsulphanylnaphthalenediol (1 mmol) in methanol
(10 ml). The mixture was refluxed at 60ꢀC for 1 h and further stirred for
4 h at room temperature. Progress of the reaction was monitored by thin-
layer chromatography (TLC) using ethyl acetate-hexane (1:5) as eluent.
Once the reaction was completed, the solvent was removed, and the crude
residue was dissolved in 30ml methanol and filtered. The filtrate was recrys-
tallized to obtain the corresponding bis-2,3-arylsulphanylnaphthoquinone.
Spectroscopic Data
Bis-2,3-phenylsulphanyl-1,4-naphthalenedione (9)
Yield 96%; mp 140ꢀC (reported 136ꢀC).[12] Elemental anal. calcd. for
C22H14O2S2: C, 70.56; H, 3.77. Found: C, 71.19; H, 3.75. 1H NMR
(400MHz, CDCl3): 7.98 (dd, J ¼ 6, 2.8 Hz, 2H), 7.68 (dd, J ¼ 5.6, 2.4 Hz,
2H), 7.37 (m, 4H), 7.29 (m, 6H). IR (KBr, cmꢁ1): 3407 (bs), 1668 (s),
1579 (w), 1498 (w), 1475 (w), 1267 (s), 1138 (w), 1081 (w), 748 (s), 706
(w), 698 (w). UV-vis (k max, CH3CN) 458nm (3.85 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2,3-(4-methoxyphenyl)sulphanyl-1,4-naphthalenedione (10)
Yield 97%; mp 91ꢀC (reported 108ꢀC),[22] Elemental anal. calcd. for
C24H18O4S2: C, 66.34; H, 4.18. Found: C, 66.33; H, 4.20. 1H NMR
(400 MHz, CDCl3): 7.95 (dd, J ¼ 5.6, 2.4 Hz, 2H), 7.64 (dd, J ¼ 5.6,
2.4 Hz, 2H), 7.38 (d, J ¼ 8.8 Hz, 4H), 6.84 (d, J ¼ 8.8 Hz, 4H), 3.81

Bis-2,3-arylsulfanyl-1,4-naphthoquinones
1439
(s, 6H). IR (KBr, cmꢁ1): 3428 (bs), 2928 (w), 1659 (s), 1590 (s), 1492 (w),
1465 (w), 1289 (w), 1271 (s), 1245 (s), 1139 (s), 1029 (w), 838 (w), 700 (w)
531 (w). LC-MS (m=e) 435, 327. UV-vis (k max, CH3CN) 458 nm
(3.76 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2,3-(4-methylphenyl)sulphanyl-1,4-naphthalenedione (11)
Yield 98%; mp 160ꢀC (reported 169ꢀC).[12] Elemental anal. calcd. for
C24H18O2S2: C, 71.61; H, 4.51. Found: C, 71.63, H, 4.50. 1H NMR
(400 MHz, CDCl3): 7.98 (dd, J ¼ 5.6, 2.4 Hz, 2H), 7.66 (dd, J ¼ 5.6,
2.4 Hz, 2H), 7.29 (d, J ¼ 8 Hz, 4H), 7.11 (d, J ¼ 8 Hz, 4H), 2.34 (s, 6H).
IR (KBr, cmꢁ1): 3433 (bw), 2921 (w), 1650 (s), 1664 (s), 1590 (w), 1492
(w), 1273 (s), 1134 (s), 1086 (w), 815 (s), 700 (w), 490 (w). UV-vis
(k max, CH3CN) 473 nm (3.83 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2,3-(4-bromophenyl)sulphanyl-1,4-naphthalenedione (12)
1
Yield 96%; mp 207ꢀC. H NMR (400 MHz, CDCl3) 7.91 (dd, J ¼ 5.6,
2.4 Hz, 2H), 7.62 (dd, J ¼ 5.6 Hz, 2.4 Hz, 2H), 7.36 (d, J ¼ 8.4 Hz, 4H),
7.17 (d, J ¼ 8.4 Hz, 4H). IR (KBr, cmꢁ1): 3435 (bw), 1666 (s), 1654 (s),
1590 (w), 1504 (w), 1471 (w), 1270 (s), 1135 (s), 1080 (w), 1006 (w), 816
(s), 708 (w), 478 (w). LC-MS (m=e) 533. UV-vis (k max, CH3CN)
457 nm (3.09 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2-(4-phenyl)-3-(4-bromophenyl)sulphanyl-1,4-naphthalenedione (13)
Yield 87%; mp 93ꢀC. Elemental anal. calcd. for C23H16O3S2: C, 68.29;
1
H, 3.99. Found: C, 68.31; H, 4.09. H NMR (400 MHz, CDCl3): 7.87
(dd, J ¼ 5.6, 2.4 Hz, 2H), 7.57 (dd, J ¼ 5.6, 2.4 Hz, 2H), 7.31 (d,
J ¼ 9.2 Hz, 4H), 6.77 (d, J ¼ 8.8 Hz, 5H), 3.73 (s, 3H). IR (KBr, cmꢁ1):
3433 (bs), 2926 (w), 1659 (s), 1590 (s), 1492 (w), 1464 (w), 1270 (s),
1245 (s), 1138 (s), 1025 (w), 809 (w), 700 (w), 530 (w). UV-vis (k max,
CH3CN) 457 nm (5.16 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2-(4-phenyl)-3-(4-methylphenyl)sulphanyl-1,4-naphthalenedione (14)
Yield 96%; mp 121ꢀC. Elemental anal. calcd. for C23H16O2S2: C, 71.10;
1
H, 4.15. Found: C, 71.22; H, 4.18. H NMR (400 MHz, CDCl3): 8.08
(dd, J ¼ 8.8, 5.6 Hz, 2H), 7.77 (dd, J ¼ 9.2, 5.2 Hz, 2H), 7.49 (d, J ¼ 8 Hz,
Hz, 2H), 7.40 (m, 5H), 7.22 (d, J ¼ 8 Hz, 2H), 2.45 (s, 3H). IR

1440
W. M. Singh and J. B. Baruah
(KBr, cmꢁ1): 3436 (bs), 2924 (w), 1664 (s), 1590 (w), 1497 (w), 1475 (w),
1264 (s), 1136 (s), 1082 (w), 812 (w), 706 (s), 503 (w). UV-vis (k max,
CH3CN) 460 nm (4.96 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2-(4-methylphenyl)-3-(4-methoxyphenyl)sulphanyl-1,4-
naphthalenedione (15)
1
Yield 88%; mp 138ꢀC. H NMR (400 MHz, CDCl3) 7.89 (dd, J ¼ 5.6,
2.8 Hz, 2H), 7.58 (dd, J ¼ 6, 3.2 Hz, 2H), 7.30 (d, J ¼ 8.8 Hz, 2H), 7.21
(d, J ¼ 8.4 Hz, 2H), 7.03 (d, J ¼ 8.4 Hz, 2H), 6.77 (d, J ¼ 7.6 Hz, 2H),
3.73 (s, 3H), 2.26 (s, 3H). IR (KBr, cmꢁ1): 3436 (bs), 2927 (w), 1664 (s),
1590 (w), 1492 (s), 1267 (s), 1138 (s), 1033 (w), 814 (w), 700 (w). LC-MS
(m=e) 420. UV-vis (k max, CH3CN) 469 nm (5.17 ꢂ 103 molꢁ1 dm3 cmꢁ1).
Bis-2-(4-methylphenyl)-3-(4-bromophenyl)sulphanyl-1,4-
naphthalenedione (16)
1
Yield 92%; mp 178ꢀC. H NMR (400 MHz, CDCl3) 7.98 (dd, J ¼ 5.6,
2.4 Hz, 2H), 7.69 (dd, J ¼ 5.6, 2.4 Hz, 2H), 7.42 (d, J ¼ 8.8 Hz, 2H),
7.26 (m, 4H), 7.12 (d, J ¼ 8.8 Hz), 2.35 (s, 3H). IR (KBr, cmꢁ1): 3435
(bs), 2922 (w), 1667 (s), 1654 (s), 1590 (w), 1503 (w), 1471 (w), 1270 (s),
1135 (s), 1080 (w), 1006 (w), 813 (w), 708 (w), 479 (w). LC-MS (m=e)
469. UV-vis (k max, CH3CN) 458 nm (3.84 ꢂ 103 molꢁ1 dm3 cmꢁ1).
ACKNOWLEDGMENTS
The authors thank the Council of Scientific and Industrial Research
(New Delhi, India) for financial assistance.
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