Iodine-catalyzed mild and efficient method for the synthesis of chalcones

Article abstract of DOI:10.1080/00397910802654724

Molecular iodine is found to catalyze the condensation of acetophenones with various aromatic aldehydes to prepare chalcones.

Full text of DOI:10.1080/00397910802654724

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Iodine-Catalyzed Mild and
Efficient Method for the
Synthesis of Chalcones
Koneni V. Sashidhara a , Jammikuntla N. Rosaiah a &
Abdhesh Kumar a
a Division of Medicinal and Process Chemistry,
Central Drug Research Institute, Lucknow, India
Version of record first published: 01 Jun 2009.
To cite this article: Koneni V. Sashidhara , Jammikuntla N. Rosaiah & Abdhesh Kumar
(2009): Iodine-Catalyzed Mild and Efficient Method for the Synthesis of Chalcones,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 39:13, 2288-2296
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Synthetic Communications1, 39: 2288–2296, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802654724
Iodine-Catalyzed Mild and Efficient Method for
the Synthesis of Chalcones
Koneni V. Sashidhara, Jammikuntla N. Rosaiah, and
Abdhesh Kumar
Division of Medicinal and Process Chemistry, Central Drug Research
Institute, Lucknow, India
Abstract: Molecular iodine is found to catalyze the condensation of acetophe-
nones with various aromatic aldehydes to prepare chalcones.
Keywords: Chalcone synthesis, Claisen–Schmidt reaction, iodine catalyst
INTRODUCTION
For the synthesis of chalcones, the Claisen–Schmidt (CS) condensation of
a ketone with an aldehyde had been carried out in the presence of aq.
[5]
NaOH,[1,2] Potassium hydroxide (KOH),[3,4] Ba(OH)2 hydrotalcites,
zeolites,[6] LiHDMS,[7] and calcined NaNO3=natural phosphates.[8,9]
The acid-catalyzed methods include the use of AlCl3,[10] dry HCl,[11]
Zn(bpy)(OAc)2,[12] TiCl4,[13] Cp2ZrH2=NiCl2,[14] and RuCl3.[15] Recently,
BF3 ꢀ Et2O,[16,17] SOCl2=EtOH,[18] and Brønsted acidic ionic liquid
catalysts[19] have been used to effect this reaction.
Because of its mild Lewis acidity, molecular I2 has recently received
considerable attention as an inexpensive, nontoxic, readily available
catalyst for various organic transformations.[20–31]
Received August 13, 2008.
Part 4 in the series Studies on Novel Synthetic Methodologies. CDRI
Communication No. 7418.
Address correspondence to Koneni V. Sashidhara, Division of Medicinal and
Process Chemistry, Central Drug Research Institute, Lucknow 226 001, India.
E-mail: sashidhar123@gmail.com
2288

Chalcone Synthesis
2289
Scheme 1. Iodine-catalyzed synthesis of chalcones.
RESULTS AND DISCUSSION
As a preliminary study, we treated 4-ethoxy benzaldehyde 1a with
acetophenone 1b in dry dioxane in the presence of I2 (5 mol %) at 40ꢁC
to form chalcone 2a in 85% yield (Scheme 1) and characterized the
products through NMR, mass, and infrared (IR) spectroscopic
studies.
To optimize the iodine requirements, 1 mol%, 5 mol%, 10 mol%,
and 20 mol % were employed, and the best results were obtained with
5 mol% of iodine in terms of yield and duration. In the absence of
iodine, the reaction did not proceed. We next investigated the scope
and generality of the reaction in which several chalcones were success-
fully synthesized 2b to 2k (Table 1) in high yields, illustrating this
novel and rapid procedure. In all cases, the reactions proceeded rapidly
Table 1. Chalcones and yields
Substrate
Aldehyde Ketone
Isolated
yield
(%)
Time
(min)
Mp
(ꢁC)
Entry
Producta
2a
20
25
15
85
90
84
52–53
95–96
2b
2c
105–106
2d
15
86
125–126
(Continued )

2290
K. V. Sashidhara, J. N. Rosaiah, and A. Kumar
Table 1. Continued
Substrate
Aldehyde Ketone
Isolated
Time
(min)
yield
(%)
Mp
(ꢁC)
Entry
Producta
2e
20
15
88
90
53–54
Liquid
Liquid
75–76
2f
2g
2h
25
25
86
85
2i
20
15
15
84
86
82
124–125
2j
114–115
104–105
2k
aAll the products were characterized 1H NMR, 13C NMR, and mass spectroscopy.
bIsolated yields after column chromatography.
under mild conditions at 40ꢁC. Most of the products were formed within
15–25 min.
To our knowledge, there are no reports of I2-catalyzed Claisen–
Schmidt reaction for the synthesis of chalcones. Other researchers[32,33]
have recently reported that iodine catalyzed the two-component conden-
sation of cycloalkanones and aryladehydes to afford the corresponding
a,a1-bis (arylmethylidene) cycloalkanones.
CONCLUSION
In conclusion, we have developed a simple and efficient synthesis of
substituted chalcones via Claisen–Schmidt condensation using molecular
I2 as a catalyst.

Chalcone Synthesis
2291
EXPERIMENTAL
Melting points were recorded on a Buchi-530 capillary melting-point
apparatus and are uncorrected. IR spectra of the compounds were
1
recorded on a Perkin-Elmer AC-1 spectrometer. H NMR spectra were
run on Bruker Avance DPX 300-MHz spectrometer in CDCl3, and tetra-
methylsilane (TMS) was used as the internal standard. Electrospray ioni-
zation (ESI) mass spectra were recorded on a Jeol S X 102=DA-6000
instrument. Silica gel (60–120 mesh) was used as a stationary phase to
isolate the compounds.
General Procedure for the Preparation of 3-(4-Ethoxy-phenyl)-
1-phenyl-propenone 2a
A mixture of a 4-ethoxy benzaldehyde 1a (150 mg, 1.0 mmol), acetophe-
none 1b (120 mg, 1.0 mmole), and iodine (5 mol%) in dry dioxane was
stirred at room temperature (40ꢁC). The reaction was monitored by
thin-layer chromatography (TLC), and on completion, excess iodine
was quenched by adding saturated sodium thiosulfate solution (5 mL)
and extracted with chloroform. The organic phase was washed with
saturated NaHCO3 solution, dried over anhydrous Na2SO4, and then
concentrated to give 2a (214 mg, 85%).
Selected Data
3-(4-Ethoxyphenyl)-1-phenylpropenone (2a)
1H NMR (CDCl3, 300 MHz) d 8.01 (d, J ¼ 7.2 Hz, 2H), 7.79 (d,
J ¼ 15.9 Hz, 1H), 7.57–7.38 (m, 6H), 6.89 (d, J ¼ 7.9 Hz, 2H), 4.01 (q,
J ¼ 7.5, 6.8 Hz, 2H), 1.40 (t, J ¼ 6.7 Hz, 3H); 13C NMR (75 MHz) d
190.48, 161.20, 144.74, 138.52, 132.66, 130.30, 128.59, 128.43, 127.37,
119.50, 114.93, 63.52, 14.54; ESI (m=z) 252 [M þ H]þ; IR (KBr cmꢂ1):
3021, 2927, 1656, 1596, 1216, 760.
3-(4-Ethoxyphenyl)-1-p-tolylpropenone (2b)
1H NMR (CDCl3, 300 MHz) d 7.94 (d, J ¼ 7.6 Hz, 2H), 7.79 (d,
J ¼ 15.2 Hz, 1H), 7.57 (d, J ¼ 8.7 Hz, 2H), 7.41 (d, J ¼ 15.2 Hz, 1H),
7.27 (d, J ¼ 7.6 Hz, 2H), 6.90 (d, J ¼ 8.1 Hz, 2H), 4.02 (q, J ¼ 7.5,

2292
K. V. Sashidhara, J. N. Rosaiah, and A. Kumar
6.8 Hz, 2H), 1.40 (t, J ¼ 6.7 Hz, 3H); 13C NMR (75 MHz) d 189.87,
161.11, 144.33, 143.33, 135.90, 130.18, 129.28, 128.61, 127.47, 119.46,
114.84, 63.70, 21.71, 14.85; ESI (m=z) 267 [M þ H]þ; IR (KBr cmꢂ1):
3030, 2977, 1648, 1563, 1217.
3-(4-Ethoxyphenyl)-1-(4-methoxyphenyl)-propenone (2c)
1H NMR (CDCl3, 300 MHz) d 8.05 (d, J ¼ 9.0 Hz, 2H), 7.79 (d,
J ¼ 15.4 Hz, 1H), 7.59 (d, J ¼ 7.9 Hz, 2H), 7.43 (d, J ¼ 15.4 Hz, 1H),
7.0–6.91 (m, 4H), 4.08 (q, J ¼ 7.5, 6.8 Hz, 2H), 3.89 (s, 3H), 1.44 (t,
J ¼ 6.7 Hz, 3H); 13C NMR (75 MHz) d 188.88, 163.30, 160.91, 143.93,
131.42, 130.71, 130.16, 127.62, 119.42, 114.88, 113.81, 63.52, 55.62,
14.54; ESI (m=z) 283 [M þ H]þ; IR (KBr cmꢂ1): 3019, 1657, 1601,
1216, 1028, 759.
1-(4-Chlorophenyl)-3-(4-ethoxyphenyl)-propenone (2d)
1H NMR (CDCl3, 300 MHz) d 7.95 (d, J ¼ 9.0 Hz, 2H), 7.77 (d,
J ¼ 15.7 Hz, 1H), 7.56 (d, J ¼ 7.9 Hz, 2H), 7.44 (d, J ¼ 15.8 Hz, 2H),
7.35 (d, J ¼ 15.8 Hz, 1H), 4.05 (q, J ¼ 7.5, 6.8 Hz, 2H), 1.42 (t, J ¼ 6.7 Hz,
3H); 13C NMR (50 MHz) d 189.79, 162.06, 146.03, 139.32, 137.26, 130.8,
130.29, 129.3, 127.65, 119.31, 115.35, 64.15, 15.17; ESI (m=z) 287
[M þ H]þ; IR (KBr cmꢂ1): 3019, 1657, 1601, 1216, 1028, 759.
3-(2-Methoxyphenyl)-1-phenylpropenone (2e)
1H NMR (CDCl3, 300 MHz) d 8.17 (d, J ¼ 15.4 Hz, 1H), 8.04 (d,
J ¼ 7.7 Hz, 2H), 7.67–7.45 (m, 5H), 7.34 (t, J ¼ 7.7 Hz, 1H), 6.99–
6.94 (t, J ¼ 7.7 Hz, 1H), 6.89 (d, J ¼ 9.0 Hz, 1H), 3.84 (s, 3H); 13C
NMR (75 MHz) d 191.01, 158.96, 140.51, 138.55, 132.79, 132.01,
129.26, 128.61, 128.53, 123.90, 122.72, 120.89, 111.34, 55.62; ESI
(m=z) 239 [M þ H]þ; IR (KBr cmꢂ1): 3061, 2956, 2837, 1659, 1597,
1340, 1248, 1209, 1018, 753.
3-(2-Methoxyphenyl)-1-p-tolylpropenone (2f)
1H NMR (CDCl3, 200 MHz) d 8.14 (d, J ¼ 16.5 Hz, 1H), 7.91 (d,
J ¼ 8.0 Hz, 2H), 7.63–7.55 (m, 2H), 7.32–7.18 (m, 3H), 6.94–6.80 (m,
2H), 3.77 (s, 3H), 2.29 (s, 3H); 13C NMR (50 MHz) d 190.66, 159.18,
143.72, 140.12, 136.29, 132.11, 129.72, 129.41, 129.05, 124.32, 122.97,

Chalcone Synthesis
2293
121.17, 111.65, 55.81, 22.12; ESI (m=z) 253 [M þ H]þ; IR (KBr, cmꢂ1):
3019, 2932, 1654, 1601, 1216, 1026, 760.
3-(2-Methoxyphenyl)-1-(4-methoxyphenyl)-propenone (2g)
1H NMR (CDCl3, 300 MHz) d 8.13 (d, J ¼ 16.1 Hz, 1H), 8.05 (d,
J ¼ 9.3 Hz, 2H), 7.68–7.62 (m, 2H), 7.38 (t, J ¼ 8.1 Hz, 1H), 7.0–6.94
(m, 4H), 3.92 (s, 3H), 3.89 (s, 3H); 13C NMR (75 MHz) d 189.40,
163.29, 158.77, 139.55, 131.60, 131.41, 130.85, 129.20, 124.16, 122.70,
120.77, 113.76, 111.27, 55.55, 55.48; ESI (m=z) 268 [M þ H]þ; IR (KBr,
cmꢂ1): 3017, 2935, 1655, 1599, 1501, 1218, 1168, 1026, 758.
1-(4-Chlorophenyl)-3-(2-methoxyphenyl)-propenone (2h)
1H NMR (CDCl3, 300 MHz) d 8.13 (d, J ¼ 14.8 Hz, 1H), 7.94 (d, J ¼ 9.2 Hz,
2H), 7.61 (d, J ¼ 8.3 Hz, 1H), 7.54 (s, 1H), 7.42 (d, J ¼ 7.3 Hz, 2H), 7.36 (t,
J¼ 7.4 Hz, 1H), 6.99–6.89 (m, 2H), 3.88 (s, 3H); 13C NMR (50 MHz) d
190.06, 159.44, 141.23, 139.29, 137.18, 132.47, 130.4, 129.69, 129.25,
124.06, 122.56, 121.24, 111.68, 55.93; ESI (m=z) 273 [M þ H]þ; IR (KBr,
cmꢂ1): 3017, 2935, 1655, 1599, 1501, 1218, 1168, 1026, 758.
3-(3-Ethoxy-4-hydroxyphenyl)-1-p-tolylpropenone (2i)
1H NMR (CDCl3, 300 MHz) d 7.94 (d, J ¼ 8.4 Hz, 2H), 7.74 (d, J¼ 15.4 Hz,
1H), 7.40 (d, J¼ 4.2 Hz, 1H), 7.28 (d, J¼ 8.4 Hz, 2H), 7.20 (d, J ¼ 7.7 Hz,
1H), 7.11 (s, 1H), 6.96 (d, J ¼ 7.7 Hz, 1H), 4.16 (q, J ¼ 6.9, 6.9 Hz, 2H),
2.43 (s, 3H), 1.47 (t, J ¼ 6.8 Hz, 3H); 13C NMR (50 MHz) d 190.24,
148.44, 146.18, 145.06, 143.44, 135.86, 129.34, 128.62, 127.46, 123.17,
119.61, 114.90, 111.04, 65.02, 22.08, 14.82; ESI (m=z) 283 [M þ H]þ; IR
(KBr, cmꢂ1): 3524, 3017, 1588, 1512, 1441.
3-(3-Ethoxy-4-hydroxyphenyl)-1-(4-methoxyphenyl)-propenone (2j)
1H NMR (CDCl3, 300 MHz) d 8.03 (d, J ¼ 9.4 Hz, 2H), 7.74 (d,
J ¼ 15.9 Hz, 1H), 7.39 (d, J ¼ 15.9 Hz, 1H), 7.20 (d, J ¼ 8.7 Hz, 1H),
7.11 (s, 1H), 6.98–6.95 (m, 3H), 4.15 (q, J ¼ 6.9, 6.9 Hz, 2H), 3.87 (s,
3H), 1.46 (t, J ¼ 6.8 Hz, 3H);13C NMR (50 MHz) d 189.34, 163.73,
148.82, 146.72, 145.07, 131.82, 131.27, 127.96, 123.54, 119.79, 115.31,
114.21, 111.49, 65.1, 55.93, 15.48; ESI (m=z) 299 [M þ H]þ; IR (KBr,
cmꢂ1): 3012, 2925, 1675, 1594, 1218, 1166, 1022.

2294
K. V. Sashidhara, J. N. Rosaiah, and A. Kumar
1-(4-Chlorophenyl)-3-(3-ethoxy-4-hydroxyphenyl)-propenone (2k)
1H NMR (CDCl3, 300 MHz) d 7.95 (d, J ¼ 7.9 Hz, 2H), 7.76 (d,
J ¼ 15.9 Hz, 1H), 7.47 (d, J ¼ 7.9 Hz, 2H), 7.40–7.29 (m, 2H), 7.21 (d,
J ¼ 7.9 Hz, 1H), 7.12 (s, 1H), 6.95 (d, J ¼ 7.1 Hz, 1H), 6.21 (s, 1H), 4.18
(q, J ¼ 6.9, 6.9 Hz, 2H), 1.49 (t, J ¼ 6.8 Hz, 3H); ESI (m=z) 303 [M þ H]þ;
; IR (KBr, cmꢂ1): 3016, 2932, 1665, 1594, 1531, 1218, 1026, 748.
ACKNOWLEDGMENTS
The Authors are grateful to the director, CDRI, Lucknow, India, for
constant encouragement for the drug development program, SAIF for
300-MHz NMR and mass spectral data, and S. P. Singh for technical
support. J. N. R. and A. K. thank the University Grants Commission
and the Council of Scientific and Industrial Research, New Delhi, India,
respectively for financial support.
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