[Hydroxy(tosyloxy)iodo]benzene: A tosyloxylating agent with selectivity for ketones in the reactions with benzalacetones

Article abstract of DOI:10.1080/00397910903321090

The treatment of enolizable ketones containing a conjugated double bond, namely benzalacetones with [hydroxy(tosyloxy)iodo]benzene, leads to regioselective tosyloxylation, thereby giving new compounds (α- tosyloxybenzalacetones).

Full text of DOI:10.1080/00397910903321090

Synthetic Communications1, 40: 2875–2879, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903321090
[HYDROXY(TOSYLOXY)IODO]BENZENE: A
TOSYLOXYLATING AGENT WITH SELECTIVITY FOR
KETONES IN THE REACTIONS WITH
BENZALACETONES
Om Prakash, Nitya Sharma, and Pooja Ranjan
Department of Chemistry, Kurukshetra University, Kurukshetra, India
The treatment of enolizable ketones containing a conjugated double bond, namely
benzalacetones with [hydroxy(tosyloxy)iodo]benzene, leads to regioselective tosyloxyla-
tion, thereby giving new compounds (a-tosyloxybenzalacetones).
Keywords: Benzalacetones; 1,3-diarylprop-2-en-1-ones (chalcones); [hydroxy(tosyloxy)iodo]benzene;
a-tosyloxybenzalacetones
INTRODUCTION
A great deal of work on the synthetic application of [hydroxy(tosyloxy)iodo]-
benzene (HTIB, Koser’s reagent) has been published in recent years.[1–4] The functio-
nalization of carbonyl compounds at a-carbon represents the most typical reaction
of HTIB, that is, to introduce the tosyloxenium ion directly onto carbon.[5–13]
Another important reaction of HTIB is the stereospecific ditosyloxylation of olefinic
compounds, including chalcones.[14] For several years, we have been carrying out
research on the use of HTIB in functionalization of carbonyl compounds.[12,15–17]
In a previous communication from our laboratory, we have reported the synthesis
and chemistry of a,b-ditosyloxyketones 4, obtained from the reaction of a,b-unsatu-
rated ketones (1,3-diarylprop-2-en-1-ones (3), chalcones) with HTIB in dichloro-
methane (Scheme 1).[17]
In continuation the research on synthetic applications of HTIB, we have exam-
ined the reaction of a,b-unsaturated ketones having enolizable moieties (i.e., benza-
lacetones) with HTIB. The aims were to ascertain the selectivity of the reaction and
achieve a-tosyloxylation of ketones. As a consequence of this effort, we report selec-
tive a-tosyloxylation of ketones in the presence of a double bond by using HTIB.
The reaction was conducted following the procedure outlined here: 1.1 eq. of
HTIB was added to dichloromethane solution of benzalacetone 1a. After being stir-
red at room temperature for about 3 h followed by workup, the reaction afforded a
single solid product, a-tosyloxybenzalacetone (2a) (Scheme 2) in 75% yield. The
Received June 4, 2009.
Address correspondence to Om Prakash, Department of Chemistry, Kurukshetra University,
Kurukshetra 136119, India. E-mail: dromprakash50@rediffmail.com
2875

2876
O. PRAKASH, N. SHARMA, AND P. RANJAN
Scheme 1. Tosyloxylation of a,b-unsaturated ketones.
=
Scheme 2. R H, CH3, OCH3, Br, Cl, F, NO2.
structure of the product was confirmed on the basis of elemental analysis and spec-
tral data. The infrared (IR) spectrum displayed a carbonyl stretch at 1695 cmꢀ1. The
1H NMR spectrum of 2a showed a characteristic singlet at 4.74 due to the methylene
group, which was further confirmed by DEPT-135 because of a negative peak.
Encouraged by the successful results, we studied the scope of new method for
the synthesis of various aryltosyloxybenzalacetones (2b–g). The reaction of various
benzalacetone derivatives (1b–g) with HTIB afforded the corresponding tosyloxy-
benzalacetones (2b–g) in good yields (Scheme 2; Table 1).
The physical data of products 4-aryl-1-tosyl-but-3-en-2-ones (2a–g) is given in
Table 1.
The a-tosyloxyketones (2a–g) obtained from this study are new compounds
and are potential precursors for the synthesis of various a-functionalized ketones
and heterocyclic compounds such as styrylthiazoles 5, which find utility in the
synthesis of compounds 6 and 7[18,19] (Scheme 3) and other thiazole derivatives.
In summary, this study demonstrates that HTIB, a tosyloxylating agent, pos-
sesses selectivity for ketones in the presence of an a,b-unsaturated conjugated double
bond. The reaction involves mild conditions and is a simple and high-yielding pro-
cedure. All the products, a-tosyloxybenzalacetones, synthesized in this study are
new compounds that are potential precursors for further chemical modification to
Table 1. Physical data of 4-aryl-1-tosyl-but-3-en-2-ones (2a–g)
Compound
R
Mp (ꢁC)
Yield (%)a
2a
2b
2c
2d
2e
2f
H
60–61
132–134
94–95
75
74
73
73
74
75
72
CH3
OCH3
Br
65–66
67–68
Cl
F
NO2
68–70
130–131
2g
aYields (%) of the products were calculated with respect to the correspond-
ing benzalacetones 1.

[HYDROXY(TOSYLOXY)IODO]BENZENE
2877
Scheme 3. Heterocyclic compounds.
synthesize the biologically active heterocyclic compounds. It is hoped that further
studies will provide useful results in the synthesis of various a-functionalized a,b-
unsaturated ketones and heterocyclic compounds.
EXPERIMENTAL
Melting points were taken in open capillaries and are uncorrected. IR spectra
1
were recorded on Perkin-Elmer IR spectrophotometer. The H NMR spectra were
recorded on a Brucker 300-MHz instrument. The chemical shifts are expressed in
parts per million downfield from an internal tetramethylsilane (TMS) standard.
Benzalacetones were prepared according to literature procedures by condensation
of acetone with substituted aldehydes in 10% aq. NaOH.[20]
General Procedure for Tosyloxylation of Benzalacetones (2a–g)
HTIB (11 mmol, 4.31 g) was added to a solution of benzalacetone 1a (10 mmol,
1.46 g) in dichloromethane. The resulting mixture was allowed to stir at room tem-
perature for 3–4 h. The solvent was evaporated in vaccuo. The gummy mass so
obtained was triturated with petroleum ether (60–80 ꢁC) to remove iodobenzene.
The colorless solid obtained was thoroughly washed with water to remove the
p-toluenesulphonic acid that formed as by-product. The solid was recrystallized from
acetonitrile to give the pure product 2a. Other derivatives 2b–g were prepared in a
similar manner.
Selected Data
4-Phenyl-1-tosyl-but-3-en-2-one (2a). IR (nmax, in KBr): 1695 cmꢀ1 (C O
=
1
str.); H NMR (CDCl3, 300 MHz, d): 2.43 (s, 3H, CH3), 4.74 (s, 2H, CH2), 6.91
(d, 1H, CH, J ¼ 16.04 Hz), 7.38–7.56 (m, 5H, Ar-H), 7.36 (d, 2H, Ar-H, J ¼ 8.1 Hz),
7.66 (d, 1H, CH, J ¼ 16.04 Hz), 7.85 (d, 2H, Ar-H, J ¼ 8.1 Hz); 13C NMR (CDCl3,
100 MHz, d): 21.70, 71.60, 120.10, 128.15, 128.79, 129.05, 130.06, 131.34, 132.41,
145.45, 191.40. Anal. calcd. for C17H16O4S: C, 64.56; H, 5.06. Found: C, 64.35;
H, 4.99. Mass, m=z: 316.
4-(4-Methylphenyl)-1-tosyl-but-3-en-2-one (2b). IR (nmax
,
in KBr):
1
1695 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.44 (s, 3H, CH3), 2.35
=

2878
O. PRAKASH, N. SHARMA, AND P. RANJAN
(s, 3H, CH3), 4.73 (s, 2H, CH2), 6.92 (d, 1H, CH, J ¼ 16.04 Hz), 7.34–7.51 (m, 4H,
Ar-H), 7.41 (d, 2H, Ar-H, J ¼ 8.3), 7.65 (d, 1H, CH, J ¼ 16.04 Hz), 7.84 (d, 2H,
Ar-H, J ¼ 8.3). Anal. calcd. for C18H18O4S: C, 65.45; H, 5.45. Found: C, 65.30; H, 5.29.
4-(4-Methoxyphenyl)-1-tosyl-but-3-en-2-one (2c). IR (nmax, in KBr):
1
1696 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.34 (s, 3H, CH3), 3.73 (s,
=
3H, OCH3), 4.73 (s, 2H, CH2), 6.92 (d, 1H, CH, J ¼ 16.04 Hz), 7.36–7.54 (m, 4H,
Ar-H), 7.39 (d, 2H, Ar-H, J ¼ 8.3), 7.63 (d, 1H, CH, J ¼ 16.04 Hz), 7.84 (d, 2H,
Ar-H, J ¼ 8.3). Anal. calcd. for C18H18O5S: C, 62.43; H, 5.20. Found: C, 62.40;
H, 4.98.
4-(4-Bromophenyl)-1-tosyl-but-3-en-2-one (2d). IR (nmax
,
in KBr):
1697 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.45 (s, 3H, CH3), 4.75 (s,
2H, CH2), 6.93 (d, 1H, CH, J ¼ 16.02 Hz), 7.28 (d, 2H, Ar-H, J ¼ 8.1), 7.36–7.53
(m, 4H, Ar-H), 7.61 (d, 1H, CH, J ¼ 16.02 Hz), 7.86 (d, 2H, Ar-H, J ¼ 8.1). Anal.
calcd. C17H15BrO4S: C, 51.65; H, 3.79. Found: C, 51.60; H, 3.79. Mass, m=z: 394.
1
=
4-(4-Chlorophenyl)-1-tosyl-but-3-en-2-one (2e). IR (nmax
,
in KBr):
1697 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.45 (s, 3H, CH3), 4.73 (s,
2H, CH2), 6.91 (d, 1H, CH, J ¼ 15.9 Hz), 7.34–7.51 (m, 4H, Ar-H), 7.41 (d, 2H,
Ar-H, J ¼ 8.4), 7.63 (d, 1H, CH, J ¼ 15.9 Hz), 7.86 (d, 2H, Ar-H, J ¼ 8.4); 13C
NMR (CDCl3, 100 MHz, d): 21.65, 72.20, 126.3, 127.8, 128.80, 129.00, 129.60,
130.60, 133.3, 133.50, 142.29, 199.50. Anal. calcd. C17H15ClO4S: C, 58.20; H, 4.27.
Found: C, 58.06; H, 4.16. Mass, m=z: 350.
1
=
4-(4-Fluorophenyl)-1-tosyl-but-3-en-2-one (2f). IR (nmax
,
in KBr):
1698 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.45 (s, 3H, CH3), 4.74 (s,
2H, CH2), 6.93 (d, 1H, CH, J ¼ 16.00 Hz), 7.36–7.55 (m, 4H, Ar-H), 7.39 (d, 2H,
Ar-H, J ¼ 8.3), 7.61 (d, 1H, CH, J ¼ 16.00 Hz), 7.84 (d, 2H, Ar-H, J ¼ 8.3). Anal.
calcd. C17H15FO4S: C, 61.08; H, 4.49. Found: C, 61.05; H, 4.31.
1
=
4-(4-Nitrophenyl)-1-tosyl-but-3-en-2-one (2g). IR (nmax
,
in KBr):
1
1700 cmꢀ1 (C O str.); H NMR (CDCl3, 300 MHz, d): 2.45 (s, 3H, CH3), 4.74 (s,
2H, CH2), 6.93 (d, 1H, CH, J ¼ 16.00 Hz), 7.39 (d, 2H, Ar-H, J ¼ 8.3), 7.61 (d,
1H, CH, J ¼ 16.00 Hz), 7.84 (d, 2H, Ar-H, J ¼ 8.3), 8.21–8.45 (m, 4H, Ar-H).
=
ACKNOWLEDGMENTS
We are thankful to Kurukshetra University, Kurukshetra, India, for the award
of a university research scholarship to Nitya Sharma and to the Council of Scientific
and Industrial Research, New Delhi, India, for the award of a senior research fellow-
ship to Pooja Ranjan for carrying out this work. The authors are also thankful to the
Council of Scientific and Industrial Research [01(2186)=07=EMR-II] for financial
support.
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