Synthesis of sulfones using sodium perchlorate as a catalyst under neutral conditions

Article abstract of DOI:10.1039/b202380f

Sulfonylation of aromatics with p-toluenesulfonyl chloride in the presence of a catalytic amount of sodium perchlorate gives the corresponding sulfones. Selectivity and neutral condition are the attractive features of this methodology.

Full text of DOI:10.1039/b202380f

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Synthesis of sulfones using sodium perchlorate as a catalyst under
neutral conditions
B. P. Bandgar,* V. T. Kamble, D. B. Fulse and M. V. Deshmukh
Organic Chemistry Research Laboratory, School of Chemical Sciences,
Swami Ramanand Teerth Marathwada University, Nanded-431 606, India.
E-mail: vtkd@rediffmail.com; Fax: þ91-2462-29245
L e t t e r
Received (in Montpellier, France) 5th March 2002, Accepted 15th April 2002
First published as an Advance Article on the web 29th July 2002
perchlorate and sodium periodate worked equally well (Table 1,
entries 3 and 4). A plausible mechanism may involve the for-
mation of p-toluenesulfonyl perchlorate or p-toluenesulfonyl
periodate when sodium perchlorate or sodium periodate are
used as catalysts. It was decided to use sodium perchlorate as
the preferred catalyst for further study of sulfonylation.
The catalytic activity of the sodium perchlorate was then
investigated with respect to the catalyst loading. After many
studies on the sulfonylation of toluene (10 ml) with p-tolue-
nesulfonyl chloride (5 mmol) under reflux conditions, we
found that when less than 20 mol % of sodium perchlorate was
applied lower yields of the corresponding product (Table 2,
entries 2–4) resulted, whereas use of more than 20 mol % did
not improve the yield (Table 2, entries 6 and 7). When attempts
were made to carry out the sulfonylation of toluene (10 ml)
with p-toluenesulfonyl chloride (5 mmol) in the absence of
sodium perchlorate catalyst, the substrate was recovered
almost quantitatively (Table 2, entry 1). The sulfonylation of
toluene in the presence of 20 mol % of sodium perchlorate
under mild condition (25 ꢀC) failed, even after stirring the
reaction mixture for a longer period of time (20 h).
The sulfonylation of various aromatics were carried out and
the results are summarized in Table 3. It was observed that the
sulfonylation of activated aromatics required shorter reaction
times (Table 3, entries a–e) as compared to the heterocyclic
and unactivated aromatics (Table 3, entries f–l). It is important
to note that the selectivity of the reaction is impressive in the
reported examples wherein exclusively para isomers of diaryl
sulfones are obtained in good yields, without the detection or
isolation of ortho=meta isomers in trace amounts. On the
other hand, the recently reported indium(III) triflate8 catalyzed
sulfonylation of activated aromatics (e.g., anisole, toluene)
yields a mixture of isomers with the composition ortho : meta :
para ¼ 38 : 0 : 62. Aluminium chloride9 also gives mixtures
of isomers (e.g., ditolyl sulfones) with the composition ortho :
meta : para ¼ 29 : 7 : 65 and it generates enormous amounts
of solid waste. Similarly, bismuth(III) triflate7 gives a mixture
Sulfonylation of aromatics with p-toluenesulfonyl chloride in the
presence of a catalytic amount of sodium perchlorate gives the
corresponding sulfones. Selectivity and neutral condition are
the attractive features of this methodology.
As useful intermediates organosulfones have become increas-
ingly important in organic synthesis1 as well as in industrial
applications.2 The most widely used procedure for the pre-
paration of sulfones is the oxidation of sulfides and sulfoxides
or by a displacement reaction using sodium arene sulfinate. A
drawback of the former method is that foul-smelling thiols are
the basic starting materials, while the sulfinate method requires
rather long reaction times, anhydrous conditions and usually
results only in moderate yields of sulfones.3,4 Friedel–Crafts
sulfonylation provides a direct route but traditionally relies on
the use of stoichiometric promoters such as aluminium(III)
chloride, which are associated with purification problems.1a
Various efficient catalytic protocols have emerged including
the use of zeolites,5 Fe(III) exchanged montmorillonite clay6
and bismuth(III) triflate.7 Very recently, indium(III) triflate8 has
been reported to catalyze sufonylation of arenes. Although
several methods are available for the preparation of sulfones in
acidic conditions,1–8 the synthesis of sulfones under neutral
conditions is not reported so far in the literature. The increasing
demand for the development of new improved methods
prompted us to employ sodium perchlorate for the sulfonyla-
tion of arenes. In this paper we wish to highlight our results on
the synthesis of diaryl sulfones using sodium perchlorate as a
catalyst under almost neutral conditions (pH 6.9) here.
Various catalysts such as sodium perchlorate, sodium per-
iodate, and sodium perborate were tested for this transfor-
mation and we found that there was no reaction with sodium
perborate catalyst, even after heating the reaction mixture
for longer times (15 h). The starting material was recovered
even when using a stoichiometric amount of catalyst under
the reaction conditions (Table 1, entry 2), whereas sodium
Table 2 A catalytic study of NaClO4 during sulfonylation of toulene
(10 ml) with p-toluenesulfonyl chloride (5 mmol) at reflux temperature
Table 1 Sulfonylation of toulene (10 ml) with p-toluenesulfonyl
chloride (5 mmol) at reflux temperature
Entry
NaClO4=mol%
Time=h
Yield=%
1
2
3
4
5
6
7
—
5
6
6
6
6
6
6
6
—
60
65
68
80
77
77
Entry
Catalyst (mol %)
Time=h
Yield=%
10
15
20
25
30
1
2
3
4
NaBO3 (20)
NaBO3 (600)
NaClO4(2O)
NalO4 (20)
15
15
6
—
—
80
79
6.5
DOI: 10.1039/b202380f
New J. Chem., 2002, 26, 1105–1107
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Table 3 NaClO4 catalyzed sulfonylation of aromatics
Entry
a
Arene
Product
Time=h
Yielda,b
80
%
6
b
c
6
6
82
80
d
e
f
5
4
9
8
8
9
8
8
8
85
88
75
73
75
76
82
82
81
g
h
i
j
k
l
a
b
Yields are of pure isolated products. Products are characterized by their physical constants and spectral analysis.
of isomers (e.g., ditolyl sulfones) with the composition ortho :
meta : para ¼ 29 : 5 : 66. In this regard the present method is
superior because it gives selectively p-ditolyl sulfones only in
good yields (Table 3, entry a). Furthermore, an improvement
in regioselectivity is also observed using sodium perchlorate
in the sulfonylation of naphthalene with p-toluenesulfonyl
chloride, giving only the b-isomer without formation of the a-
isomer in trace amounts. On the other hand, sulfonylation of
naphthalene using Fe(III) exchanged montmorillonite clay6
catalyst gave a mixture of a- and b-isomers.
In conclusion, the present results demonstrate the efficiency
of sodium perchlorate as an catalyst for sulfonylation of
activated, heterocyclic and unactivated aromatics under almost
neutral conditions and constitutes a useful alternative to the
commonly accepted sulfonylation procedures. The effective-
ness of this protocol is manifested in its selectivity.
On completion of the reaction (TLC), the reaction mixture was
cooled and toulene was removed under reduced pressure. To
the residue chloroform (10 ml) and water (10 ml) were added.
The aqueous layer was washed with chloroform (3 ꢁ 5 ml). The
combined organic layer was dried with anhydrous Na2SO4 and
removal of the solvent under vacuum furnished crude product,
which was further purified by column chromatography (pet-
roleum ether–ethyl acetate ¼ 8 : 2 ). In the case of solid sub-
strates, nitrobenzene (10 ml) was used as a solvent.
Di-p-tolyl sulfone (3a). M.p. ¼ 156 ꢀC (lit. 156 ꢀC).10 IR
(KBr, cmꢂ1): 630, 765, 816, 990, 1035, 1100, 1180, 1360, 1460,
1500, 1600, 3421; 1H NMR (300 MHz, CDCl3): d 2.39 (s, 6H, 2
Ar–CH3), 7.27 (d, 4H, J ¼ 5 Hz, 4 Ar–H), 7.80 (d, 4H, J ¼ 5
Hz, 4 Ar–H). EI-MS: m=z ¼ 246 (Mþ). Anal. calcd. for
C14H14SO2 (246.27): C, 68.28%; H, 5.73%; S, 12.99%. Found:
C, 68.33%; H, 5.69%; S, 13.02%.
Experimental
(3,4-Dimethylphenyl)-p-tolyl sulfone (3b). M.p. ¼ 55 ꢀC. IR
(KBr, cmꢂ1): 1017, 1123, 1342, 1447, 1515, 1603; 1H NMR
(300 MHz, CDCl3): d 2.3(s, 3H, ArCH3), 2.36 (s, 3H, Ar–CH3)
2.43 (s, 3H, Ar–CH3), 7.1 (d, 1H, J ¼ 7.5 Hz, Ar–H), 7.8 (d,
1H, J ¼ 1.5 Hz, Ar–H), 8.0 (dd, 1H, J ¼ 1.5 Hz, 7.5 Hz, Ar–H)
7.5 (d, 2H, J ¼ 8.6 Hz, Ar–H), 8.1 (d, 2H, J ¼ 8.6 Hz, Ar–H)
Typical experimental procedure
A mixture of toulene (10 ml), p-toluenesulfonyl chloride (5
mmol) and sodium periodate (1 mmol) was refluxed for 6 h.
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New J. Chem., 2002, 26, 1105–1107

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7.5 (d, 2H, J ¼ 8.6 Hz, Ar–H). EI-MS: m=z ¼ 260 (Mþ). Anal.
calcd. for C15H16SO2 (260.30): C, 69.92%; H, 6.20%; S,
12.30%. Found: C, 69.88%; H, 6.24%; S, 12.26%.
d 2.33 (s, 3H, Ar–CH3) 7.06–7.15 (m, 4H, Ar–H), 7.7 (d, 2H,
J ¼ 7.7 Hz, Ar–H), 7.8 (d, 1H, J ¼ 8.1 Hz, Ar–H), 8.1 (dd, 1H,
J ¼ 1.3 Hz, 8.1 Hz, Ar–H), 8.2 (d, 1H, J ¼ 1.3 Hz, Ar–H), 8.3
(d, 2H, J ¼ 7.7 Hz, Ar–H). EI-MS: m=z ¼ 306 (Mþ). Anal.
calcd. for C19H14SO2 (306.32): C, 74.50%; H, 4.60%; S,
10.45%. Found: C, 74.56%; H, 4.56%; S, 10.51%.
(2,4-Dimethylphenyl)-p-tolyl sulfone (3c). M.p. ¼ 49 ꢀC (lit.
48–49 ꢀC).10 IR (KBr, cmꢂ1): 1028, 1110, 1175, 1355, 1455,
1505, 1610; 1H NMR (300 MHz, CDCl3): d 2.34 (s, 3H,
ArCH3), 2.38 (s, 3H, Ar–CH3) 2.41 (s, 3H, Ar–CH3), 7.01 (d,
1H, J ¼ 1.7 Hz, Ar–H), 7.16 (dd, 1H, J ¼ 1.7 Hz, 7.7 Hz, Ar–
H), 7.25 (d, 2H, J ¼ 8.8 Hz, Ar–H), 7.77 (d, 2H, J ¼ 8.8 Hz,
Ar–H), 8.08 (d, 1H, J ¼ 7.7 Hz, Ar–H). EI-MS: m=z ¼ 260
(Mþ). Anal. calcd. for C15H16SO2 (260.30): C, 69.92%; H,
6.20%; S, 12.30%. Found: C, 69.88%; H, 6.24%; S, 12.26%.
(4-Fluorophenyl)-p-tolyl sulfone (3j). M.p. ¼ 93 ꢀC (lit. 95ꢀC).11
IR (KBr, cmꢂ1): 629, 775, 816, 880, 1050, 1110, 1175, 1355, 1590,
3390; 1H NMR (300 MHz, CDCl3): d 2.42 (s, 3H, Ar–CH3), 7.20
(m, 2H, Ar–H), 7.35 (d, 2H, J¼ 8.4 Hz, Ar–H) 7.85 (d, 2H, J¼ 8.4
Hz, Ar–H), 7.91–7.98 (m, 2H, Ar–H). EI-MS: m=z ¼ 250 (Mþ).
Anal. calcd. for C13H11SO2F (250.23): C, 62.40%; H, 4.4%; S,
12.79%; F, 7.59%. Found: C, 62.37%; H, 4.39%; S, 12.84%; F,
7.65%.
(2,4,6-Trimethylphenyl)-p-tolyl sulfone (3d). M.p. ¼ 122 ꢀC
(lit. 123 ꢀC).10 IR (KBr, cmꢂ1): 810, 1011, 1150, 1350, 1460,
1
1522, 1611; H NMR (300 MHz, CDCl3): d 2.32 (s, 3H, Ar–
(4-Chlorophenyl)-p-tolyl sulfone (3k). M.p. ¼ 124 ꢀC (lit.
123 ꢀC).10 IR (KBr, cmꢂ1): 626, 772, 885, 816, 990, 1040, 1100,
1175, 1353, 1599, 3397; 1H NMR (300 MHz, CDCl3): d 2.38 (s,
3H, Ar–CH3), 7.34 (d, 2H, J ¼ 7.7 Hz, Ar–H), 7.43–7.52 (m,
2H, Ar–H), 7.82 (d, 2H, J ¼ 9.0 Hz, Ar–H), 7.86–7.92 (m, 2H,
Ar–H). EI-MS: m=z ¼ 267 (M þ 1)þ. Anal. calcd. for
C13H11SO2Cl (266.68): C, 58.55%; H, 4.1%; S, 12.00%; Cl,
13.29%. Found: C, 58.61%; H, 4.21 %; S, 11.94%; Cl,
13.35%.
CH3), 2.35 (s, 3H, Ar–CH3), 2.45 (s, 6H, 2 Ar–CH3), 7.03 (s,
2H, Ar–H), 7.62 (d, 2H, J ¼ 8.4Hz, Ar–H), 8.2 (d, 2H, J ¼ 8.4
Hz, Ar–H). EI-MS: m=z ¼ 274 (Mþ). Anal. calcd. for
C16H18SO2 (274.32): C, 70.06%; H, 6.61%; S, 11.67%. Found:
C, 69.9 8%; H, 6.57%; S, 11.73%.
(4-Methoxyphenyl)-p-tolyl sulfone (3e). M.p. ¼ 105 ꢀC; (lit.
104 ꢀC)10 IR (KBr, cmꢂ1): 683, 838, 1007, 1360, 1599, 2910,
1
3300; H NMR (300 MHz, CDCl3): d 2.36 (s, 3H, CH3), 3.81
(s, 3H, OCH3), 6.95 (d, 2H, J ¼ 7.2 Hz, Ar–H), 7.91 (d, 2H,
J ¼ 7.2 Hz, Ar–H), 7.15 (d, 2H, J ¼ 8.8 Hz, Ar–H), 8.14 (d,
2H, J ¼ 8.8 Hz, Ar–H). EI-MS: m=z ¼ 262 (Mþ) Anal. calcd.
for C14H14SO3 (262.27): C, 64.12%; H, 5.38%; S, 12.20%.
Found: C, 64.09%; H, 5.45%; S, 12.11%.
(4-Bromophenyl)-p-tolyl sulfone (3l). M.p. ¼ 136–137 ꢀC (lit.
135–136 ꢀC).11 IR (KBr, cmꢂ1): 626, 772, 816, 895, 1030, 1120,
1175, 1360, 1580, 3410; 1H NMR (300 MHz, CDCl3): d 2.49 (s,
3H, Ar–CH3), 7.48 (d, 2H, J ¼ 8.5 Hz, Ar–H), 7.76–7.91 (m,
4H, 4 Ar–H), 7.98 (d, 2H, J ¼ 8.5 Hz, Ar–H). EI-MS:
m=z ¼ 312 (M þ 1).þ Anal. calcd. for C13H11SO2Br (311.13): C,
50.19%; H, 3.56%; S, 10.29%; Br, 25.68%. Found: C,
50.25%; H, 3.62%; S, 10.27%; Br, 25.67%.
(Thiophene)-3-p-tolyl sulfone (3f). M.p. ¼ 110 ꢀC. IR (KBr,
cmꢂ1): 1160, 1310, 1500, 1610; 1H NMR (300 MHz, CDCl3): d
7.8 (d, 2H, J ¼ 8.1 Hz, Ar–H), 8.02 (d, 2H, J ¼ 8.1 Hz, ArH),
8.12–8.3 (m, 3H, Ar–H). EI-MS: m=z ¼ 238 (Mþ). Anal. calcd.
for C11H10S2O2 (238.1): C, 55.44%; H, 4.23%; S, 26.89%.
Found: C, 55.51%; H, 4.19 %; S, 26.94%.
References
(Phenyl)-p-tolyl sulfone (3g). M.p. ¼ 126 ꢀC (lit. 127 ꢀC).10
1
(a) F. R. Jensen and G. Goldman, in FriedelꢂCrafts and Related
Reactions., ed. G. Olah, Wiley Interscience, New York, 1964,
vol. III, pp 1319–1367; (b) N. S. Simpkins, Sulfones in Organic
Synthesis, Pergamon Press, Oxford, 1993 and references cited
therein.
K. M. Roy, in Ullmann’s Encyclopedia of Industrial Chemistry, ed.,
W. Gerhartz, VCH, Weinheim, 1985, vol. A 25, pp 487–501 and
references cited therein.
1
IR (KBr, cmꢂ1): 1153, 1303, 1500, 1604; H NMR (300 MHz,
CDCl3): d 2.4 (s, 3H, Ar–CH3), 7.2 (d, 2H, J ¼ 7.8 Hz, Ar–H),
7.4–7.8 (m, 5H, Ar–H), 8.01 (d, 2H, J ¼ 7.8 Hz, Ar–H) EI-MS:
m=z ¼ 232 (Mþ). Anal. calcd. for C13H12SO2 (232.24): C,
67.23%; H, 5.21%; S, 13.78%. Found: C, 67.19%; H, 5.26 %;
S, 13.84%.
2
3
C. M. Suter, T he Organic Chemistry of Sulfur, John Wiley and
Sons, New York, 1948, p. 568–773.
(Bisphenyl)-p-tolyl sulfone (3h). M.p. ¼ 155 ꢀC. IR (KBr,
cmꢂ1): 1160, 1312, 1512, 1601; 1H NMR (300 MHz, CDCl3): d
2.36 (s, 3H, Ar–CH3), 7.11–7.24 (m, 5H, Ar–H), 7.75 (d, 2H,
J ¼ 8.2 Hz, Ar–H), 7.89 (d, 2H, J ¼ 7.9 Hz, Ar–H), 8.1 (d, 2H,
J ¼ 7.9 Hz, Ar–H), 8.3 (d, 2H, J ¼ 8.2 Hz, Ar–H). EI-MS:
m=z ¼ 296 (Mþ). Anal. calcd. for C18H16SO2 (296.33): C,
72.96%; H, 5.44%; S, 10.80%. Found: C, 72.96%; H, 5.39 %;
S, 10.85%.
4
5
J. Smeek and J. S. Fowler, J. Org. Chem., 1968, 33, 3422.
K. Smith, G. M. Ewart and K. R. Randles, J. Chem. Soc., Perkin
T rans. 1, 1997, 1085.
B. M. Choudary, N. S. Chowdari, M. L. Kantam and R. Kannan,
Tetrahedron L ett., 1994, 40, 2859.
S. Rapichet, C. Le Roux and J. Dubac, J. Org. Chem., 1999, 64,
6479.
C. G. Froast, J. P. Hartley and A. J. Whittle, Synlett, 2000, 6, 830.
G. A. Olah, S. Kobayashi and J. Nishimura, J. Am. Chem. Soc.,
1973, 95, 564.
6
7
8
9
10 M. Ueda, K. Uchiyama and T. Kano, Synth. Commun., 1984, 323.
11 B. M. Choudari, N. S. Chowdari and M. L. Kantam, J. Chem.
Soc., Perkin T rans. 1, 2000, 2689.
(b-Naphthyl)-p-tolyl sulfone (3i). M.p. ¼ 164 ꢀC. IR (KBr,
1
cmꢂ1): 1155, 1305, 1509, 1607; H NMR (300 MHz, CDCl3):
New J. Chem., 2002, 26, 1105–1107
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