One-pot synthesis of indene derivatives by CF3SO 3H-promoted reactions of benzylic alcohols and 1,3-dicarbonyl compounds

Article abstract of DOI:10.1016/j.tetlet.2013.01.088

An efficient and convenient one-pot synthesis of indene derivatives was achieved in moderate to high yields by the CF₃SO₃H promoted coupling/cyclization reaction of benzylic alcohols and 1,3-dicarbonyls for the first time. For the reactions of methoxy- or methyl-substituted diarylmethanols with 1,3-dicarbonyls, 2 equiv of CF₃SO₃H was needed to reach the best results; but for the reactions of methoxy-substituted arylethanols with 1,3-dicarbonyls, 0.6 equiv of CF ₃SO₃H at lower temperatures was capable of promoting the reaction finished.

Full text of DOI:10.1016/j.tetlet.2013.01.088

Tetrahedron Letters 54 (2013) 1747–1750
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
One-pot synthesis of indene derivatives by CF3SO3H-promoted reactions
of benzylic alcohols and 1,3-dicarbonyl compounds
⇑
Wenxue Zhang, Yisi Dai, Haizhen Zhu, Wei Zhang
State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient and convenient one-pot synthesis of indene derivatives was achieved in moderate to high
yields by the CF3SO3H promoted coupling/cyclization reaction of benzylic alcohols and 1,3-dicarbonyls
for the first time. For the reactions of methoxy- or methyl- substituted diarylmethanols with
1,3-dicarbonyls, 2 equiv of CF3SO3H was needed to reach the best results; but for the reactions of
methoxy-substituted arylethanols with 1,3-dicarbonyls, 0.6 equiv of CF3SO3H at lower temperatures
was capable of promoting the reaction finished.
Received 31 October 2012
Revised 13 January 2013
Accepted 21 January 2013
Available online 30 January 2013
Keywords:
Indene
Ó 2013 Elsevier Ltd. All rights reserved.
Benzylic alcohols
1,3-Dicarbonyls
One-pot coupling/cyclization reaction
Indene frameworks are frequently observed in many molecules
with important biological activities such as natural products1–8
and pharmaceuticals,9–15 and are also extensively used as ligands
in metallocenes in the catalysis of olefin polymerization.16–18 In
addition, indene derivatives are also of important applications in
functional materials.19–21 As a result, various methods to construct
indene ring systems have been reported, such as iron-catalyzed
annulation of N-benzylic sulfonamides with disubstituted
alkynes,22 palladium-catalyzed carboannulation 2-(2-(1-alky-
nyl)phenyl)malonate with arylhalides,23 BF3ꢀEt2O-mediated
cycloaddition of methylenecyclopropanes with aldehydes,24
a simple and efficient method for the synthesis of 2-benzyl-1,3-
dicarbonyls,34–36 and the cyclocondensation of methyl 3-benzylace-
toacetates for the synthesis of methyl indene-2-carboxylates was
also reported recently.37 As continuation of the construction of
cyclic compounds by cyclocondensation,38 we report in this paper
a one-pot synthesis of 2-acylindenes by the combination of the
coupling of benzylic alcohols and 1,3-dicarbonyls and cycloconden-
sation (Scheme 1). To the best of our knowledge, the present work
provides the first example of Brunsted acid-catalyzed one-pot
synthesis of indene derivatives from benzylic alcohols and
1,3-dicarbonyls.
copper-catalyzed [3+2] cycloaddition of
a
-aryldiazoesters with
Initial attempts at the coupling/cyclization reaction were made
with benzylic alcohols 1a and ethyl acetoacetate 2a as substrates
because the efficient coupling or intramolecular cyclization reac-
tions in the previous studies32,33,37 were limited to arylmethanols
in which aromatic rings bear an electron-donating group, such as
an alkyl or an alkyloxy group.
Of the catalysts and solvents screened (Table 1), only trifluoro-
methanesulfonic acid (TfOH) gave the desired cyclization product
3a as the main product, and the best result (65% yield) was obtained
from the combination of 2.0 equiv of TfOH and dichloromethane
(entry 5), while reactions under other conditions gave lower yields
of 3a or no 3a (entries 1–4 and 6–10). Apparently, these conditions
were different from conditions reported by Ohwada for the cycliza-
tion of ethyl 3-arylmethylacetoacetate in which the large quantity
of TfOH (10–50 equiv) was needed.37 Comparatively, treating sub-
strate 1a and 2a with TiCl4 in dichloromethane leads to only the
coupling product 5a (entry 1), and 3a was not detected even after
a prolonged reaction time or elevating the reaction temperature.
Similarly, treating substrate 1a and 2a with PPA also gave only
terminal alkynes,25 Cu(OTf)2-catalyzed rearrangement of
vinylcyclopropenes,26 FeCl3-catalyzed Friedel–Crafts reaction of
arylated allylic alcohols,27 gold (I)-catalyzed intramolecular
carboalkoxylation,28 ruthenium-mediated ring-closing metathe-
sis,29 iodonium-promoted 5-endo-dig carbocyclization of 2-(2-eth-
ynylphenyl)malonates,30 and photochemical cyclization of
tetrafluoropyridinyl (TFP)-substituted enediynes.31 Moreover, PPA
(polyphosphoric acid)-mediated cyclocondensation reaction of
4-arylbutan-2-ones is also a traditional but efficient method for
the synthesis of indene derivatives.32,33 Although so many methods
have been established to construct the indene structure, the
synthesis of indene derivatives by Br
condensation of the coupling products from benzylic alcohols and
1,3-dicarbonyls is rare. It is well known that the Lewis and Br nsted
unsted acid catalyzed cyclo-
u
acid catalyzed coupling of benzylic alcohols with 1,3-dicarbonyls is
⇑
Corresponding author. Tel.: +86 931 891 2582.
E-mail address: zhangwei6275@lzu.edu.cn (W. Zhang).
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.01.088

1748
W. Zhang et al. / Tetrahedron Letters 54 (2013) 1747–1750
3
4
R
R
3
R
O
1
OH
R
O
O
O
1
TfOH
CH Cl
1
2
R
R
R
5
3
R
R
5
4
5
+
R
R
R
2
2
2
4
R
R
2
O
R
Scheme 1. Synthesis of 2-acylindene derivatives by the one-pot reaction of benzylic alcohols and 1,3-dicarbonyls.
Table 1
Screening catalysts and optimization of reaction conditions
Ph
O
O
Ph
OH
Ph
O
MeO
MeO
MeO
O
O
O
MeO
OEt
acid
OH
OEt
OEt
5a
2a
Acid
4a
1a
3a
Entry
Solvent
t (h)
T (°C)
Product
Yield (%)
a
a
a
a
a
a
1
2
3
4
5
6
7
8
9
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
2 Equiv TiCl4
2 Equiv SnCl4
0.5 Equiv TfOH
1.0 Equiv TfOH
2.0 Equiv TfOH
10 Equiv TfOH
2.0 Equiv TfOH
2.0 Equiv TfOH
5 Equiv PPA
12
12
12
12
2
0–rt
0–rt
0–rt
0–rt
0–rt
0–rt
0–rt
0–rt
rt
5a
3a + 5a
5a
3a + 5a
3a
3a + 4a
5a
Complex
5a
5a
32
40 + 10
55
50 + 20
65
13 + 20
40
—
84
85
2
CH3CNa
DCEa
12
12
24
12
Noneb
Nonec
10
5 Equiv PPA
60
a
The reaction was carried out with 1a (1.0 mmol), 2a (1.2 mmol), and 0.5–10 equiv of catalyst which was slowly added in solvent (20 mL) at 0 °C, and
the reactions mixture was allowed to reach to room temperature.
b
The reaction was carried out with 1a (1.0 mmol), 2a (1.2 mmol), and 5 equiv of PPA (polyphosphoric acid) with no solvent at room temperature.
The reaction was carried out with 1a (1.0 mmol), 2a (1.2 mmol), and 5 equiv of PPA with no solvent at room temperature and the reactions mixture
c
was allowed to reach to 60 °C.
Table 2
One-pot coupling/cyclization reaction of benzylic alcohols and 1,3-dicarbonyls promoted by trifluoromethanesulfonic acida
R3
R4
R3
R3
R3
O
R1
R2
O
R1
R2
OH
R3
O
O
O
O
R1
R2
+
0.6-2 equiv TfOH
CH2Cl2 0-r.t °C
or -10-r.t °C
+
R5
+
OH
R1
OH
R1
+
R5
R4
R5
R4
R2
R2
R4
R4
4'q,t
1a-j
2a-d
3a-u
4d, 4h-i, 4k, 4q, 4t
3'q-u
Entry
Substrate
R3
Time (h)
Product
3:4
Yield (%)
R1
R2
R4
R5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1a
1a
1a
1a
1b
1b
1b
1b
1c
1c
1d
1e
1f
OMe
OMe
OMe
OMe
OMe
OMe
OMe
OMe
Cl
H
H
H
H
OMe
OMe
OMe
OMe
H
H
H
H
OMe
OMe
OMe
OMe
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Me
Me
Me
Me
Me
Ph
2a
Me
Me
Me
Ph
Me
Me
Me
Ph
Me
Me
Me
Me
Me
Me
Me
Ph
OEt
Me
Ph
OEt
OEt
Me
Ph
OEt
OEt
Me
OEt
OEt
OEt
Me
Ph
2
12
12
12
1
3a
3b
3c
3d + 4d
3e
65
70
55
53
84
90
50
55
2b
2c
2d
2a
2b
2c
2d
2a
2b
2a
2a
2a
2b
2c
2d
2a
4:1
1
8
3f
3g
12
24
24
24
12
2
12
12
12
12
3h + 4h
3i + 4i
3j
3k + 4k
3l
3m
3n
3o
3p
3q + 4q
3q0 + 4q’
3r + 3r0
3s + 3s0
3t + 4t
3t0
3u + 3u0
5i
5j
7:1
1:1
38
40
60
Cl
H
4:1
OMe
OMe
OMe
OMe
OMe
Me
40b
60b
80b
84b
60b
51
1f
1f
1f
1g
OEt
OEt
Me
3q:3q0 = 2:1
4q:4q0 = 2:1
3r:3r0 = 2:1
3s:3s0 = 2:1
3t:3t0 = 2:1
18
19
20
1g
1g
1h
Me
Me
Me
H
H
Me
Ph
Ph
Ph
2b
2c
2a
Me
Me
Me
Me
Ph
OEt
12
12
24
72
64
72
21
22
23
1h
1i
1j
Me
H
H
Me
OMe
Me
Ph
Ph
Ph
2b
2a
2b
Me
Me
Me
Me
OEt
Me
24
24
24
3u:3u0 = 2:1
—
—
87
c
c
a
The reaction was carried out with 1 (1.0 mmol), 2 (1.2 mmol), and 2 equiv of TfOH which was slowly added in CH2Cl2 (20 mL) at 0 °C, and the reactions mixture was
allowed to reach to room temperature.
b
The reaction was carried out with 1 (1.0 mmol), 2 (1.2 mmol), and 0.6 equiv of TfOH which was slowly added in CH2Cl2 (20 mL) at ꢁ10 °C, then the reactions mixture was
allowed to reach to room temperature.
c
Yield of the coupling product 5 and no cyclization products 3 and 4 were formed.

W. Zhang et al. / Tetrahedron Letters 54 (2013) 1747–1750
1749
group (R1 = R2 = OMe) favored both the coupling reaction and the
cyclization reaction. In contrast, the substrate bearing the elec-
tron-attracting substituent on the aromatic ring (R1 = Cl) gave a
poor result (Table 2, entries 9 and 10). Comparatively, the reaction
of ethyl acetoacetate (2a) generally gave the cyclization products 3
in lower yields than the reaction of acetoacetone (2b); and the
reaction of diarylmethanols (1a–d) generally gave the cyclization
products 3 in higher yields than the reaction of arylethanols
(1e–1f). Unexpectedly, for the para-methyl-, para-methoxy-substi-
tuted diarylmethanol, the cyclization reactions were totally
blocked (Table 2, entries 22 and 23), and only the coupling
reactions could proceed normally. All these observations are in
accordance with the previously reported results for the cyclization
of 2-benzyl-1,3-dicarbonyls.32,33,37
In addition, it was also observed from Table 2 that the TfOH-
promoted coupling/cyclization reaction of ethyl 2-acylacetate (2a
and 2d) affords the products as a mixture of ester (3d, 3h, 3i, 3k)
and carboxylic acid (4d, 4h, 4i, 4k) (entries 4, 8, 9, and 11). While
the less reaction time (entries 1 and 5) or the smaller quantity of
TfOH could stop the formation of acid (entries 12, 13, and 16).
Reactions of the unsymmetric methyl-substituted substrate
1g–h with 2a–c also afforded the products as mixtures (Table 2).
The products were not only derived from the hydrolysis of ester,
but also from a different regioselectivity which was different from
that in the reactions of methoxy-substituted substrates 1a–f with
2a–d. All products were fully identified by 1H NMR, 13C NMR, IR,
and HRMS and the structure of 3c was further confirmed by
X-ray crystallography (Fig. 1).39
A plausible mechanism was proposed for the formation of in-
dene derivatives from the TfOH-promoted coupling/cyclization
reactions of benzylic alcohols and 1,3-dicarbonyl compounds
according to the results and Ohwada’s study38 (Scheme 2).
In summary, we have developed a mild and efficient method for
the one-pot synthesis of indene derivates in moderate to
high yields by trifluoromethanesulfonic acid (TfOH)-promoted
Figure 1. X-ray crystal structure of product 3c.
the coupling product 5a (entries 9 and 10), even at an elevated tem-
perature. Thus, using 2.0 equiv of TfOH as the promoter in dichloro-
methane at 0 °C was selected as the optimized condition for the
synthesis of 3a.
Under the optimized condition described above, the reactions of
a group of benzylic alcohols 1a–h and 1,3-diarbonyls 2a–d were
examined.39 In most cases, the substrates underwent the one-pot
reaction smoothly to afford the corresponding products 3 in mod-
erate to good yields (Table 2, entries 1–11). Moreover, the better
results could be obtained for the reactions of 1-arylethanol 1e–f
with 2a–d under the catalysis of only 0.6 equiv of trifluorometh-
anesulfonic acid (TfOH) at ꢁ10 °C in CH2Cl2 (Table 2, entries
12–16).
Among these results, the reaction of substrate 1b with 2b gave
the best result (Table 2, entry 6). Obviously, the electron-donating
OH
O
Ph
O
OH
OEt
MeO
MeO
MeO
OEt
2a
TfOH
-H2O
Ph
Ph
HO
1a
Ph
Ph OH
OH
MeO
-H2O
TfOH
MeO
OEt
OEt
H2O
HO
Ph
MeO
O
OEt
TfO-
Ph
Ph
MeO
OH
3a
-TfOH
MeO
OH
OEt
TfO-
-TfOH
OEt
Ph
MeO
O
OHEt
H
-EtOH
Ph
Ph
H2O
MeO
MeO
O
TfO-
O
OH
-TfOH
4a
Scheme 2. A plausible reaction mechanism for the formation of 2-acylindenes in the presence of trifluoromethanesulfonic acid.

1750
W. Zhang et al. / Tetrahedron Letters 54 (2013) 1747–1750
19. Barberá, J.; Rakitin, O. A.; Ros, M. B.; Torroba, T. Angew. Chem., Int. Ed. 1998, 37,
296–299.
20. Yang, J.; Lakshmikantham, M. V.; Cava, M. P. J. Org. Chem. 2000, 65, 6739–6742.
21. Akbulut, U.; Khurshid, A.; Haciog˘lu, B.; Toppare, L. Polymer 1990, 31, 1343–
1351.
22. Liu, C. R.; Yang, F. L.; Jin, Y. Z.; Ma, X. T.; Cheng, D. J.; Li, N.; Tian, S. K. Org. Lett.
2010, 12, 3832–3835.
23. Guo, L. N.; Duan, X. H.; Bi, H. P.; Liu, X. Y.; Liang, Y. M. J. Org. Chem. 2006, 71,
3325–3327.
coupling/cyclization reaction of benzylic alcohols and 1,3-dicar-
bonyls. For the reactions of methoxy- or methyl-substituted diaryl-
methanols with 1,3-dicarbonyls, 2 equiv of TfOH was needed to
give better results; but for the reactions of methoxy-substituted
arylethanols with 1,3-dicarbonyls, 0.6 equiv of TfOH at lower tem-
peratures was capable of promoting the reaction finished.
24. Shi, M.; Xu, B.; Huang, J. W. Org. Lett. 2004, 6, 1175–1178.
25. Park, E. J.; Kim, S. H.; Chang, S. J. Am. Chem. Soc. 2008, 130, 17268–17269.
26. Shao, L. X.; Zhang, Y. P.; Qi, M. H.; Shi, M. Org. Lett. 2007, 9, 117–120.
27. Wang, J. L.; Zhang, L. X.; Jing, Y. F.; Huang, W.; Zhou, X. G. Tetrahedron Lett.
2009, 50, 4978–4982.
28. Dubé, P.; Toste, F. D. J. Am. Chem. Soc. 2006, 128, 12062–12063.
29. Coyanis, E. M.; Panayides, J. L.; Fernandes, M. A.; Koning, C. B.; Willem, A. L. J.
Organomet. Chem. 2006, 691, 5222–5239.
Acknowledgment
We are grateful to the National Nature Science Foundation of
China (Grant No. 20872056) for financial support.
Supplementary data
30. Khan, Z. A.; Wirth, T. Org. Lett. 2009, 11, 229–231.
31. Alabugin, I. V.; Kovalenko, S. V. J. Am. Chem. Soc. 2002, 124, 9052–9053.
32. Ahn, J. H.; Shin, M. S.; Jung, S. H.; Kang, S. K.; Kim, K. R.; Rhee, S. D.; Jung, W. H.;
Yang, S. D.; Kim, S. J.; Woo, J. R.; Lee, J. H.; Cheon, H. G.; Kim, S. S. J. Med. Chem.
2006, 49, 4781–4784.
33. Romines, K. R.; Lovasz, K. D.; Mizsak, S. A.; Morris, K.; Seest, E. P.; Han, F.;
Tulinsky, J.; Judge, T. M.; Gammill, R. B. J. Org. Chem. 1999, 64, 1733–1737.
34. Thirupathi, P.; Kim, S. S. Tetrahedron 2010, 66, 2995–3003.
35. Huang, W.; Wang, J. L.; Shen, Q. S.; Zhou, X. G. Tetrahedron Lett. 2007, 48, 3969–
3973.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2013.01.
088.
References and notes
1. Majetich, G.; Shimkus, J. J. Nat. Prod. 2010, 73, 284–298.
2. Liang, G. X.; Xu, Y.; Seiple, I. B.; Trauner, D. J. Am. Chem. Soc. 2006, 128, 11022–
11023.
3. Wang, Y.; Mo, S. Y.; Wang, S. J.; Li, S.; Yang, Y. C.; Shi, J. G. Org. Lett. 2005, 7,
1675–1678.
4. Korte, A.; Legros, J.; Bolm, C. Synlett 2004, 13, 2397–2399.
5. Zhang, H. J.; Tan, G. T.; Santarsiero, B. D.; Mesecar, A. D.; Hung, N. V.; Cuong, N.
M.; Soejarto, D. D.; Pezzuto, J. M.; Fong, H. H. S. J. Nat. Prod. 2003, 66, 609–615.
6. Beukes, D. R.; Davies-Coleman, M. T.; Kelly-Borges, M.; Harper, M. K.; Faulkner,
D. J. J. Nat. Prod. 1998, 61, 699–701.
7. Harrowven, D. C.; Newman, N. A.; Knight, C. A. Tetrahedron Lett. 1998, 39, 6757–
6760.
8. Aknin, M.; Miralles, J.; Kornprobst, J. M.; Faure, R.; Gaydou, E. M.; Esnault, N.;
Koto, B. Y.; Clardy, J. Tetrahedron Lett. 1990, 31, 2979–2982.
9. Koike, T.; Hoashi, Y.; Takai, T.; Nakayama, M.; Yukuhiro, N.; Ishikawa, T.; Hirai,
K.; Uchikawa, O. J. Med. Chem. 2011, 54, 3436–3444.
10. Yang, L. H.; Butora, G.; Jiao, R. X.; Pasternak, A.; Zhou, C. Y.; Parsons, W. H.;
Mills, S. G.; Vicario, P. P.; Ayala, J. M.; Cascieri, M. A.; MacCoss, M. J. Med. Chem.
2007, 50, 2609–2611.
11. Clegg, N. J.; Paruthiyil, S.; Leitman, D. C.; Scanlan, T. S. J. Med. Chem. 2005, 48,
5989–6003.
12. Watanabe, N.; Ikeno, A.; Minato, H.; Nakagawa, H.; Kohayakawa, C.; Tsuji, Jun-
ichi J. Med. Chem. 2003, 46, 3961–3964.
13. Park, C. H.; Siomboing, X.; Yous, S.; Gressier, B.; Luyckx, M.; Chavatte, P. Eur. J.
Med. Chem. 2002, 37, 461–466.
14. Reich, S. H.; ohnson, T.; Wallace, J. M. B.; Kephart, S. E.; Fuhrman, S. A.;
Worland, S. T.; Matthews, D. A.; Hendrickson, T. F.; Chan, F.; Meador, J., III;
Ferre, R. A.; Brown, E. L.; DeLisle, D. M.; Patick, A. K.; Binford, S. L.; Ford, C. E. J.
Med. Chem. 2000, 43, 1670–1683.
15. Ouimet, N.; Chan, C. C.; Charleson, S.; Claveau, D.; Gordon, R.; Guay, D.; Li, C. S.;
Ouellet, M.; Percival, D. M.; Riendeau, D.; Wong, E.; Zamboni, R.; Prasit, P.
Bioorg. Med. Chem. Lett. 1999, 9, 151–156.
36. Yasuda, M.; Somyo, T.; Baba, A. Angew. Chem., Int. Ed. 2006, 45, 793–796.
37. Kurouchi, H.; Sugimoto, H.; Otani, Y.; Ohwada, T. J. Am. Chem. Soc. 2010, 132,
807–815.
38. Zhou, Y. H.; Qian, L. F.; Zhang, W. Synlett 2009, 5, 843–847.
39. Synthesis of 3a: A 50 mL round-bottom flask was charged with 1a (1 mmol), 2a
(1.2 mmol), anhydrous CH2Cl2 (20 mL) and a stirring bar. After the solution was
cooled to 0 °C and stirred for 10 min, CF3SO3H (2 mmol) was added portion
wise, and the reactions mixture was allowed to reach rt. The mixture was
stirred for 2 h at room temperature till 1a disappeared completely, 2 mL water
poured into the flask, and the mixture extracted with ethyl acetate
(3 ꢂ 15 mL). The combined organic layers were dried with anhydrous
Na2SO4, and concentrated in vacuo. The residue was isolated by flash column
chromatography on silica gel to give the products 3a (65%).
Compound 3a: Yellow grease; 1H NMR (400 MHz, CDCl3) d: 7.40 (d, J = 8.4 Hz,
1H), 7.24–7.16 (m, 3H), 7.06–7.04 (m, 2H), 6.87 (dd, J = 2.4, 8.4 Hz, 1H), 6.72 (d,
J = 2.4 Hz, 1H), 4.76 (d, J = 2.0 Hz, 1H), 4.13 (dt, J = 3.6, 7.2 Hz, 1H), 4.02 (dt,
J = 3.6, 7.2 Hz, 1H),3.74 (s, 3H), 2.58 (d, J = 2.0 Hz, 3H), 1.09 (t, J = 7.2 Hz, 3H)
ppm. 13C NMR (100 MHz, CDCl3) d: 165.3, 160.7, 151.9, 151.2, 139.9, 136.9,
132.7, 128.3, 127.9, 126.5, 121.9, 113.1, 109.9, 59.5, 55.7, 55.4, 14.1, 12.5 ppm.
IR (KBr): 3023, 2925, 2854, 1671, 1427, 908, 737 cmꢁ1. ESI-HRMS: m/z Calcd
for C20H20O3+H+: 309.1485. Found 309.1487.
Compound 3c: Yellow grease; 1H NMR (400 MHz, CDCl3) d: 7.64 (d, J = 7.2 Hz,
2H), 7.48 (t, J = 7.6 Hz, 1H), 7.41–7.35 (m, 3H), 7.24–7.11 (m, 2H), 7.09–7.05 (m,
2H), 6.93 (dd, J = 2.4, 8.4 Hz, 1H), 6.78 (d, J = 1.6 Hz, 1H), 5.14 (d, J = 1.6 Hz, 1H),
3.76 (s, 3H),3.10 (d, J = 2.0 Hz, 3H) ppm. 13C NMR (100 MHz, CDCl3) d: 194.4,
160.6, 151.0, 147.2, 142.8, 140.3, 138.9, 137.4, 131.9, 128.7, 128.5, 128.2, 128.0,
126.7, 122.0, 113.6, 109.8, 56.8, 55.5, 13.6 ppm. IR (KBr): 3061, 3003, 2916,
1654, 1223, 910, 133 cmꢁ1. ESI-HRMS: m/z Calcd for C24H20O2+H+: 341.1536.
Found 341.1539.
Crystal data for compound 3c (recrystallized from ethanol):
C24H20O2,
Mr = 380.25, trigonal, a = 28.7569(13) Å, b = 28.7569(13) Å, c = 11.5446(10) Å,
b = 90.00°, V = 8267.8(9) Å3, clear light yellow plate, Dc = 1.375 g cmꢁ3, T = 296
16. Cadierno, V.; Diez, J.; Pilar, G. M.; Gimeno, J.; Lastra, E. Coord. Chem. Rev. 1999,
147, 193–195.
17. Zargarian, D. Coord. Chem. Rev. 2002, 157, 233–234.
18. Leino, R.; Lehmus, P.; Lehtonen, A. Eur. J. Inorg. Chem. 2004, 16, 3201–3222.
(2) K, space group P2(1)/c, Z = 4, l
(MoKa) = 0.71073 mmꢁ1, 2hmax = 52.64, 4107
reflection collected, 2382 unique (Rinit = 0.0838) which was used in all
calculations. Final wR(F2) = 0.1381 (all data). CCDC file No. 899272.