Intermolecular couplization and cyclization of chalcones promoted by samarium in DMF

Article abstract of DOI:10.1080/00397910802431164

Under mild and neutral conditions, reductive coupling-cyclization of chalcones was promoted by samarium metal with an activator in DMF to afford products in good to excellent yields. The reaction is regioselective over the competitive carbon-carbon double

Full text of DOI:10.1080/00397910802431164

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Intermolecular Couplization
and Cyclization of Chalcones
Promoted by Samarium in DMF
Yongjun Liu a , Ningning Dai a , Yan Qi a & Shusheng
Zhang a
a Key Laboratory of Eco-chemical Engineering,
Ministry of Education, College of Chemistry and
Molecular Engineering, Qingdao University of
Science and Technology, Qingdao, China
Version of record first published: 29 Jan 2009.
To cite this article: Yongjun Liu , Ningning Dai , Yan Qi & Shusheng Zhang (2009):
Intermolecular Couplization and Cyclization of Chalcones Promoted by Samarium in
DMF, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 39:5, 799-807
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Synthetic Communications1, 39: 799–807, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802431164
Intermolecular Couplization and Cyclization
of Chalcones Promoted by Samarium in DMF
Yongjun Liu, Ningning Dai, Yan Qi, and Shusheng Zhang
Key Laboratory of Eco-chemical Engineering, Ministry of Education,
College of Chemistry and Molecular Engineering, Qingdao University of
Science and Technology, Qingdao, China
Abstract: Under mild and neutral conditions, reductive coupling–cyclization of
chalcones was promoted by samarium metal with an activator in DMF to afford
products in good to excellent yields. The reaction is regioselective over the com-
petitive carbon–carbon double-bond reduction and stereocontrolled.
Keywords: Chalcones, cycntanols, DMF, samarium
In recent decades, the expansion of synthetic methodology to lanthanide
metals including samarium reagents bloomed as a result of their particu-
lar application to the synthesis of natural products.[1] Moreover, by virtue
of samarium’s potential in synthetic chemistry, various original means
were adopted to try many organic reactions based on its excellent reduc-
tion–coupling ability, and a lot of useful reactions have been developed in
the course of these attempts lately.[2]
Carbon–carbon bond formation is the essence of organic synthesis,
and the reductive dimerization of carbonyl derivatives is one of the most
valuable methods for establishing carbon–carbon bonds. In a general
fashion, the carbonyl derivatives are aldehydes, ketones, carboxylic
esters, acid chlorides, or imines.[3] Recently, samarium(II) iodide–induced
Received May 9, 2008.
Address correspondence to Shusheng Zhang, Key Laboratory of Eco-chemical
Engineering, Ministry of Education, College of Chemistry and Molecular Engi-
neering, Qingdao University of Science and Technology, Qingdao 266042, China.
E-mail: shushzhang@126.com
799

800
Y. Liu et al.
reductive cyclodimerizationof a,b-unsatuatedketoneshasbeenreported.[4]
Although samarium diiodide is a very useful reducing reagent, there are
some drawbacks when it is used as a reductant, such as its sensitivity to
air and moisture and difficult storage. Because of consideration of atom
economy, its application in organic synthesis is, to some extent, limited.
Presently, the direct use of metallic samarium as a reducing agent in
organic transformations has attracted the attention of a great many
organic chemists.[5] To improve the activity of metallic samarium, some
additives are needed.[6] THF has been one of the most favorite reaction
media in organic reactions presented by samarium,[1,5,7] whereas we have
explored some drastically interesting characteristics of metallic samarium
as a reducing agent when N,N-dimethylformamide (DMF) was used as
the solvent.[8]
Here we report that when DMF is used as a solvent instead of THF,
metallic samarium, with iodine or TMSCl as an activator, can promote
the reductive cyclization of chalcones, affording cycntanols in good yields
at room temperature (Scheme 1).
Table 1 summarized the results of the cyclization reactions of various
substrates. Comparing to the results when TMSCl was used as the acti-
vator (entries 17–20), the yields were relatively higher when I2 was used,
but longer reaction time was required (entries 1, 3, 4, 10). Among all the
results, the yields of the products also depended on the electronic effect of
the substituents. According to the results shown in Table 1, when the sub-
strates were attached with extraordinarily electron-donating groups
(entries 2, 7, 9, 12) such as methoxyl or furyl either on Ar or Ar0, the
yields of products were lowered and longer reaction time was needed.
On the other hand, when the electron-drawing ability of substituents
strengthened, especially on Ar0, the corresponding yield decreased mark-
edly (entries 6, 11, 13, 15, 16).
The IR spectra show the infrared absorption of the arylcarbonyls of
products are much less than normal value (most of them are less than
1640 cmꢀ1; see the Experimental section), which indicates a hydrogen
Scheme 1.

Samarium-Promoted Reactions of Chalcones
801
Table 1. Coupling-cyclization of chalcones promoted by samarium metal in DMF
Entry
Ar
Ar0
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
C6H5
2-Furyl
4-CH3C6H4
4-ClC6H4
C6H5
C6H5
C6H5
C6H5
C6H5
4-CH3C6H4
4-ClC6H4
4-CH3OC6H4
4-CH3C6H4
4-CH3OC6H4
4-CH3C6H4
4-ClC6H4
4-CH3OC6H4
4-FC6H4
C6H5CH ¼ CH–
4-ClC6H4
4-NO2C6H5
C6H5
C6H5
4-ClC6H4
C6H5
3
4
82 (2a)
62 (2b)
95 (2c)
95 (2d)
81 (2e)
68 (2f)
66 (2g)
80 (2h)
66 (2i)
90 (2j)
75 (2k)
62 (2l)
32 (2m)
34 (2n)
3.5
3.5
4
4.5
5
3
4
3
3
4
4
3
4
3.5
2
2
2
2
C6H5
C6H5
4-CH3C6H4
4-CH3C6H4
4-ClC6H4
4-CH3C6H4
4-ClC6H4
C6H5
C6H5
4-ClC6H4
4-C6H4
4-CH3C6H4
4-ClC6H4
4-CH3C6H4
C6H5
b
—
—
b
83 (2c)c
80 (2d)c
74 (2k)c
66 (2a)c
aIsolated yields, based on substrates.
bA complicated mixture was afforded.
cTMSCl was used instead of I2.
bond may exist between the carbonyl and the vicinal hydroxyl; therefore,
a cis-configuration I should be presented, possibly resulting from the
coordination of samarium during the reaction process (II).[4]
In conclusion, the use of metallic samarium was successful for the
reaction type of couplization and cyclization that would typically have
employed SmI2. This reaction provides useful products from readily
obtainable starting materials in good yields.
EXPERIMENTAL
General
1
All H NMR spectra were recorded on a Bruker AV 500 spectrometer
with TMS as the internal standard. Chemical shifts are expressed in parts
per million (ppm), and J values are given in hertz (Hz). Infrared (IR)

802
Y. Liu et al.
spectra were run on a Nicolet FT-IR Magna-750 spectrometer. Elemental
analyses were performed on a Vario-ELIII equipment. Single-crystal
X-ray diffraction were performed on NONIUS-CAD4. Melting points
are uncorrected. All the reactions in this article were performed
under a nitrogen atmosphere. DMF was redistilled over calcium hydride
before use.
Typical Procedure for the Sm/Cat. I2 System–Promoted Reductive
Cyclization of Chalcones
A chalcone (2 mmol) was added to a mixture of Sm powder (2 mmol) and
iodine (0.01 mmol) in DMF (10 mL) at room temperature with magnetic
stirring under a nitrogen atmosphere. The reaction was monitored by
thin-layer chromatography (TLC). After being stirred for a given time
(Table 1), the reaction was quenched with dilute HCl (0.1 mol=L,
5 mL), and the mixture was extracted with ethyl acetate (3 ꢁ 15 mL).
The organic phase was washed with saturated brine (15 mL) and dried
over anhydrous Na2SO4. The solvents were removed under reduced pres-
sure to give the crude product, which was isolated by silica-gel chromato-
graphy using ethyl acetate and cyclohexane (1:5) as eluant.
Data
(2-Hydroxy-2,4,5-triphenylcyclopentyl)(phenyl)methanone (2a)
White solid, mp 190–192 ꢂC (lit.[4] 192–194 ꢂC); nmax=cmꢀ1 (KBr): 3437
(OH), 3028, 2923, 1641 (C¼O); dH (acetone): 2.48 (dd, 1 H), 3.10 (dd,
1 H), 3.96 (dd, 1 H), 4.23 (t, 1 H), 4.85 (d, 1 H), 5.17 (s, 1 H), 7.01–
7.03 (m, 1 H), 7.04–7.20 (m, 6 H), 7.24–7.30 (m, 4 H), 7.37–7.45 (m,
5 H), 7.62–7.65 (m, 2 H), 7.72–7.75 (m, 2 H). 13C NMR d (acetone):
202.7, 147.0, 144.7, 141.1, 138.2, 133.4, 128.63, 128.61, 126.55, 128.44,
128.34, 128.29, 127.0, 126.6, 125.6, 83.7, 64.3, 58.6, 53.3, 51.9. Anal.
calcd. for C30H26O2: C, 86.09; H, 6.26. Found: C, 86.46; H, 6.27.
(4,5-Di(furan-2-yl)-2-hydroxy-2-phenylcyclopentyl)(phenyl)methanone
(2b)
White solid, mp 134–135 ꢂC; nmax=cmꢀ1 (KBr): 3456 (OH), 3057, 2983,
2869, 1660 (C¼O); dH (CDCl3): 2.50 (dd, 1 H), 2.76 (dd, 1 H), 3.94 (m,
1 H), 4.23 (dd, 1 H), 4.59 (d, 1 H), 5.16 (S, 1 H), 5.93–6.28 (m, 4 H),

Samarium-Promoted Reactions of Chalcones
803
7.15–7.53 (m, 12 H). Anal. calcd. for C26H22O4: C, 78.37; H, 5.57. Found:
C, 78.50; H, 5.54.
(2-Hydroxy-2-phenyl-4,5-dip-tolylcyclopentyl)(phenyl)methanone (2c)
White solid, mp 188–190 ꢂC (lit.[4] 188–190 ꢂC); nmax=cmꢀ1 (KBr): 3434
(OH), 3023, 2920, 1639 (C¼O); dH (DMSO): 2.12 (s, 3 H), 2.22 (s, 3 H),
2.30 (dd, 1 H), 2.90 (dd, 1 H), 3.71 (dd, 1 H), 4.17 (t, 1 H), 4.41 (d, 1 H),
5.56 (s, 1 H), 6.92–6.94 (m, 2 H), 7.04–7.11 (m, 4 H), 7.16–7.20 (m, 3 H),
7.22–7.27 (m, 6 H), 7.32–7.34 (m, 1 H), 7.56–7.58 (m, 2 H). Anal. calcd. for
C32H30O2: C, 86.06; H, 6.77. Found: C, 86.12; H, 6.78.
(4,5-Bis(4-chlorophenyl)-2-hydroxy-2-phenylcyclopentyl)(phenyl)
methanone (2d)
White solid, mp 187–189 ꢂC (lit.[4] 192–194 ꢂC); nmax=cmꢀ1 (KBr): 3435
(OH), 3045, 2935, 1636 (C¼O); dH (DMSO): 2.34 (dd, 1 H), 2.95 (dd,
1 H), 3.77 (dd, 1 H), 4.18 (t, 1 H), 4.46 (d, 1 H), 5.68 (s, 1 H), 7.07–
7.10 (m, 2 H), 7.15–7.18 (m, 1 H), 7.21–7.27 (m, 6 H), 7.31–7.38 (m,
7 H), 7.55–7.57 (m, 2 H). Anal. calcd. for C30H24Cl2O2: C, 73.92; H,
4.96. Found: C, 73.89; H, 4.95.
(2-Hydroxy-4,5-diphenyl-2-p-tolylcyclopentyl)(p-tolyl)methanone (2e)
White solid, mp 172–174 ꢂC (lit.[4] 170–171.5 ꢂC); nmax=cmꢀ1 (KBr): 3453
(OH), 3027, 2970, 1637 (C¼O); dH (acetone): 2.18 (s, 3 H), 2.19 (s, 3 H),
2.37 (dd, 1 H), 2.98 (dd, 1 H), 3.87 (m, 1 H), 4.12 (t, 1 H), 4.80 (d, 1 H),
5.21 (s, 1 H), 6.95–6.97 (m, 3 H), 7.03–7.10 (m, 5 H), 7.17–7.19 (m,
2 H), 7.29–7.31 (m, 2 H), 7.36–7.38 (m, 2 H), 7.44–7.46 (m, 2 H), 7.56–
7.58 (m, 2 H). 13C NMR d (acetone): 203.8, 146.0, 145.6, 144.9, 142.1,
137.3, 136.7, 130.1, 129.9, 129.8, 129.6, 129.5, 129.4, 129.3, 127.9,
127.5, 126.5, 85.0, 64.6, 60.4, 53.9, 52.8, 21.9, 21.4. Anal. calcd. for
C32H30O2: C, 86.06; H, 6.77. Found: C, 86.01; H, 6.79.
(4-Chlorophenyl)(2-(4-chlorophenyl)-2-hydroxy-4,5-diphenylcyclopen-
tyl)methanone (2f)
White solid, mp 163–165 ꢂC; nmax=cmꢀ1 (KBr): 3449 (OH), 3060, 2926,
1642 (C¼O); dH (acetone): 2.43 (dd, 1 H), 3.03 (dd, 1 H), 3.88 (dd, 1 H),
4.19 (t, 1 H), 4.72 (d, 1 H), 5.14 (s, 1 H), 6.98–7.00 (m, 1 H), 7.08–7.10

804
Y. Liu et al.
(m, 3 H), 7.16–7.19 (m, 4 H), 7.23–7.25 (m, 2 H), 7.31–7.36 (m, 4 H), 7.46–
7.48 (m, 2 H), 7.67–7.69 (m, 2 H). Anal. calcd. for C30H24Cl2O2: C, 73.92;
H, 4.96. Found: C, 73.88; H, 4.95.
(2-Hydroxy-2-(4-methoxyphenyl)-4,5-diphenylcyclopentyl)
(4-methoxyphenyl)meth-anone (2g)
White solid, mp 144–145 ꢂC; nmax=cmꢀ1 (KBr): 3424 (OH), 3027, 2933,
1632 (C¼O); dH (acetone): 2.36 (dd, 1 H), 2.99 (dd, 1 H), 3.69 (s, 3 H),
3.73 (s, 3 H), 3.86 (m, 1 H), 4.12 (t, 1 H), 4.79 (d, 1 H), 5.35 (s, 1 H),
6.69–6.70 (m, 2 H), 6.79–6.81 (m, 2 H), 6.95–6.97 (m, 1 H), 7.09–7.40
(m, 9 H), 7.59–7.63 (m, 4 H). Anal. calcd. for C32H30O4: C, 80.31; H,
6.32. Found: C, 80.26; H, 6.35.
(2-Hydroxy-2,4,5-trip-tolylcyclopentyl)(p-tolyl)methanone (2h)
White solid, mp 180–182 ꢂC; nmax=cmꢀ1 (KBr): 3433 (OH), 3024, 2920,
1634 (C¼O); dH (CDCl3): 2.18 (s, 3 H), 2.27 (s, 3 H), 2.28 (s, 3 H), 2.29
(s, 3 H), 2.51 (dd, 1 H), 2.94 (dd, 1 H), 3.70 (m, 1 H), 4.04 (t, 1 H), 4.47
(d, 1 H), 5.27 (s, 1 H), 6.90–6.92 (m, 2 H), 6.96–6.98 (m, 2 H), 7.03–7.10
(m, 6 H), 7.28–7.30 (m, 2 H), 7.36–7.38 (m, 2 H), 7.43–7.45 (m, 2 H). Anal.
calcd. for C34H34O2: C, 86.04; H, 7.22. Found: C, 86.20; H, 7.24.
(2-Hydroxy-2-(4-methoxyphenyl)-4,5-di-p-tolylcyclopentyl)
(4-methoxyphenyl)meth-anone (2i)
White solid, mp 129–131 ꢂC; nmax=cmꢀ1 (KBr): 3428 (OH), 3007, 2932,
1631 (C¼O); dH (CDCl3): 2.19 (s, 3 H), 2.29 (s, 3 H), 2.51 (dd, 1 H),
2.92 (dd, 1 H), 3.68 (m, 1 H), 3.78 (s, 3 H), 3.79 (s, 3 H), 4.04 (t, 1 H),
4.41 (d, 1 H), 5.40 (s, 1 H), 6.64–6.66 (m, 2 H), 6.81–6.82 (m, 2 H), 6.91–
6.93 (m, 1 H), 7.03–7.07 (m, 5 H), 7.28–7.30 (m, 2 H), 7.47–7.49 (m, 4 H).
Anal. calcd. for C34H34O4: C, 80.60; H, 6.76. Found: C, 80.85; H, 6.80.
(4,5-Bis(4-chlorophenyl)-2-hydroxy-2-p-tolylcyclopentyl)(p-tolyl)
methanone (2j)
White solid, mp 112–114 ꢂC; nmax=cmꢀ1 (KBr): 3449 (OH), 3032, 2924,
1636 (C¼O); dH (CDCl3): 2.28 (s, 3 H), 2.30 (s, 3 H), 2.48 (dd, 1 H),
2.52 (dd, 1 H), 3.62 (m, 1 H), 3.99 (t, 1 H), 4.47 (d, 1 H), 5.27 (s, 1 H),

Samarium-Promoted Reactions of Chalcones
805
7.00–7.01 (m, 2 H), 7.06–7.11 (m, 6 H), 7.22–7.23 (m, 2 H), 7.32–7.33
(m, 2 H), 7.37–7.39 (m, 2 H), 7.43–7.45 (m, 2 H). Anal. calcd. for
C32H28Cl2O2: C, 74.56; H, 5.48. Found: C, 74.44; H, 5.46.
(4-Chlorophenyl)(2-(4-chlorophenyl)-2-hydroxy-4,5-di-p-tolylcyclopen-
tyl)methanone (2k)
White solid, mp 177–179 ꢂC; nmax=cmꢀ1 (KBr): 3443 (OH), 3024, 2921,
1642 (C¼O); dH(CDCl3): 2.16 (s, 3 H), 2.25 (s, 3 H), 2.48 (dd, 1 H),
2.87 (dd, 1 H), 3.70 (m, 1 H), 3.99 (t, 1 H), 4.33 (d, 1 H), 5.17 (s, 1 H),
6.89–6.91 (m, 2 H), 6.99–7.04 (m, 6 H), 7.11–7.13 (m, 2 H), 7.23–7.26
(m, 2 H), 7.31–7.33 (m, 2 H), 7.44–7.46 (m, 2 H). Anal. calcd. for
C32H28Cl2O2: C, 74.56; H, 5.48. Found: C, 74.68; H, 5.50.
(4,5-Bis(4-chlorophenyl)-2-hydroxy-2-(4-methoxyphenyl)cyclopentyl)
(4-methoxyph-enyl)methanone (2l)
White solid, mp 166–168 ꢂC; nmax=cmꢀ1 (KBr): 3452 (OH), 3026, 2931,
1633 (C¼O); dH (CDCl3): 2.50 (dd, 1 H), 2.93 (dd, 1 H), 3.62 (m, 1 H),
3.76 (s, 3 H), 3.78 (s, 3 H), 3.99 (t, 1 H), 4.43 (d, 1 H), 5.37 (s, 1 H),
6.67–6.68 (m, 2 H), 6.81–6.83 (m, 2 H), 7.07–7.12 (m, 4 H), 7.23–7.26
(m, 2 H), 7.30–7.32 (m, 2 H), 7.45–7.47 (m, 4 H). Anal. calcd. for
C32H28Cl2O4: C, 70.20; H, 5.16. Found: C, 70.31; H, 5.19.
(4-Fluorophenyl)(2-(4-fluorophenyl)-2-hydroxy-4,5-diphenylcyclopen-
tyl)methanone (2m)
White solid, mp 232–233 ꢂC; nmax=cmꢀ1 (KBr): 3396 (OH), 3088, 2976,
1643 (C¼O); dH (CDCl3): 2.49 (dd, 1 H), 2.84 (dd, 1 H), 3.50 (m, 1 H),
3.99 (t, 1 H), 4.44 (d, 1 H), 5.10 (s, 1 H), 6.74–6.76 (m, 2 H), 6.94–6.96
(m, 2 H), 7.04–7.11 (m, 4 H), 7.18–7.32 (m, 7 H), 7.59–7.61 (m, 1 H),
7.72–7.74 (m, 2 H). Anal. calcd. for C30H24F2O2: C, 79.28; H, 5.32.
Found: C, 79.32; H, 5.29.
(E)-1-(2-Hydroxy-4,5-diphenyl-2-(E)-styrylcyclopentyl)-3-phenylprop-
2-en-1-one (2n)
White solid, mp 214–216 ꢂC; nmax=cmꢀ1 (KBr): 3416 (OH), 3123, 3066,
2946, 1640 (C¼O); dH (CDCl3): 2.30 (dd, 1 H), 2.72 (dd, 1 H), 3.58

806
Y. Liu et al.
(m, 1 H), 3.65 (d, 1 H), 3.85 (dd, 1 H), 5.04 (s, 1 H), 6.22 (d, 1 H,
J ¼ 16 Hz), 6.39 (d, 1 H, J ¼ 16 Hz), 6.79 (d, 1 H, J ¼ 16 Hz), 7.13–7.36
(m, 21 H). Anal. calcd. for C34H30O2: C, 86.77; H, 6.43. Found: C,
86.67; H, 6.44.
ACKNOWLEDGMENT
This work was supported by the Foundation of the Key Laboratory of
Organofluorine Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences (O4B0021400), the Natural Science Foun-
dation of Shandong Province (No. Z2006B07), and the Project of Science
and Technology of Shandong Province (No. 2006GG2203024).
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