An efficient one-step synthesis of fulleroisoxazolines and fulleropyrazolines mediated by (diacetoxyiodo)benzene

Article abstract of DOI:10.1016/j.tetlet.2010.09.038

An efficient one-step strategy for the synthesis of fulleroisoxazolines/ fulleropyrazolines from fullerene and aldoximes/hydrazones mediated by PhI(OAc)₂ has been described.

Full text of DOI:10.1016/j.tetlet.2010.09.038

Tetrahedron Letters 51 (2010) 6056–6059
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Tetrahedron Letters
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An efficient one-step synthesis of fulleroisoxazolines and
fulleropyrazolines mediated by (diacetoxyiodo)benzene
⇑
Hai-Tao Yang , Xiao-Jiao Ruan, Chun-Bao Miao, Xiao-Qiang Sun
Faculty of Chemistry and Chemical Engineering, Changzhou University, Changzhou 213164, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 July 2010
Revised 12 September 2010
Accepted 14 September 2010
Available online 17 September 2010
An efficient one-step strategy for the synthesis of fulleroisoxazolines/fulleropyrazolines from fullerene
and aldoximes/hydrazones mediated by PhI(OAc)2 has been described.
Ó 2010 Elsevier Ltd. All rights reserved.
Chemical modification is one of the most important research
fields in the fullerene chemistry. 1,3-Dipolar cycloaddition plays
an important role in the preparation of modified fullerenes for
application in medicinal chemistry and materials science. Up to
now various 1,3-dipoles including azomethine ylides, diazo com-
pounds, azides, nitrile oxides, nitrile ylides, nitrile imines, pyrazo-
linium ylides, and carbonyl ylides have been reported to react with
fullerenes.1 Although fulleropyrrolidines have been by far the most
studied and versatile derivatives obtained from 1,3-dipolar cyc-
loadditions, other fullerene-fused pentagonal heterocyclic rings,
such as fulleroisoxazolines or fulleropyrazolines, are also known
to show appealing chemical, electrochemical, and photophysical
properties. For example, fulleroisoxazolines undergo an efficient
retro-cycloaddition reaction in the presence of an excess of a die-
nophile and Cu(II) catalysis, which can be selectively used in the
presence of malonate or pyrrolidine cycloadducts.2 The electro-
chemical properties of the fulleroisoxazoline and fulleropyrazoline
compounds in which a heteroatom is directly linked to the C60 cage
were investigated to show the same or better acceptor character
cur upon conventional heating. Isoxazoline-fused fullerenes can
also be prepared from the reactions of [60]fullerene with N-silyl-
oxynitrones, formed from nitoalkene and Me3SiCl/Et3N, after acid
treatment.7 Irngartinger also reported that the nitrile oxides gener-
ated from ester of glycine hydrochloride using NaNO2.8 Despite so
many ways for preparation of fulleroisoxazolines or fulleropyrazo-
lines, the scope of these protocols is limited by two-step processes,
basic and anhydrous condition. Herein, we developed a convenient
method to achieve fulleroisoxazolines or fulleropyrazolines by a
one-step reaction of [60]Fullerene with aldoximes or hydrazones
mediated by (diacetoxyiodo)benzene.
Hydrazone has a vinyl C–H and an N–H bond and aldoxime has
a vinyl C–H and an O–H bond. Their structures are similar to enam-
ine and enol, respectively (Fig. 1). It was reported that the
Mn(OAc)3Á2H2O can mediate the oxidative radical cycloaddition
of b-keto esters, beta-diketones, and b-enamino compounds to
9
C60
.
Considering the structure similarities, we presumed that this
reaction may also be applicable to hydrazone or aldoxime sub-
strates. The first substrate examined was benzaldoxime 1a. When
than C60. It is different from fulleropyrrolidines which usually exhi-
a mixture of C60 (36.0 mg), benzaldoxime 1a (1 equiv), and
3
bit a decrease in electron affinity with respect to the parent C60
.
Mn(OAc)3Á2H2O (1 equiv) was stirred in 20 mL toluene for 24 h at
room temperature, no reaction occurred. While the reaction tem-
perature was raised to 100 °C, the desired product 2a was isolated
in 13% yield along with several by-products after 4 h of stirring.
The result was not so satisfying. Then we considered using
PhI(OAc)2 as an oxidant, which has been used as a common and
unique oxidant in many reactions,10 to substitute for Mn(OAc)3Á
2H2O. In earlier documents PhI(OAc)2 has also been used in the
Fulleroisoxazolines or fulleropyrazolines have been readily ob-
tained by addition of nitrile oxides or nitrilimine to [60]fullerene
in moderate yields through different methods. Meier firstly re-
ported the addition reaction of C60 with nitrile oxides which was
generated through dehydration of nitroalkanes with phenylisocya-
nate and Et3N.4 The most commonly used method for the prepara-
tion of fulleroisoxazolines or fulleropyrazolines includes two steps:
first synthesis of hydroximinoyl halides or hydrazonoyl halides
from aldoxime or hydrazone using NCS or NBS and then reacting
with fullerene through dehydrohalogenation in the presence of or-
ganic base.5 An alternative procedure involved the generation of
corresponding dipole from hydrazones under microwave irradia-
tion.6 It should be noted that this microwave process does not oc-
R3
O
HN
O
OH
R2
N
R1
R1
N
N
H
OH
R1
R2
R1
R2
enamine
hydrazone
Figure 1.
enol
oxime
⇑
Corresponding author. Tel./fax: +86 519 86330257.
E-mail address: yanght898@yahoo.com.cn (H.-T. Yang).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.038

H.-T. Yang et al. / Tetrahedron Letters 51 (2010) 6056–6059
6057
cycloaddition reaction of nitrile oxide or nitrilimine with electron
deficient olefins such as ethyl acrylate or acrylonitrile.11 Das has
reported the hypervalent iodine-mediated interaction of aldoxime
with activated alkene including Baylis–Hillman adducts and intra-
molecular [3+2] reaction for reparation of benzopyrano and furo-
pyrano-2-isoxazoline derivatives.12 Gan has reported the
PhI(OAc)2-mediated reaction of amino acid ester with C60, from
which pyrrolidino[60]fullerene and aziridino[60]fullerene could
be formed selectively controlled by iodine.13 Most recently, Ciufo-
line reported the PhI(OAc)2-mediated tandem oxidative dearoma-
tization of phenols/intramolecular nitrile oxide cycloaddition
sequences leading to useful synthetic intermediates.14
To our satisfaction, when a mixture of C60 (36.0 mg), ben-
zaldoxime 1a (1 equiv), and PhI(OAc)2 (1 equiv) was stirred in
20 mL toluene for 100 min at room temperature (Table 1), the de-
sired fulleroisoxazolines 2a was obtained in good yield (51%). The
process was greatly accelerated by using PhI(OAc)2 compared to
using Mn(OAc)3Á2H2O. This is a simple method of constructing
isoxazoline cycle on fullerene through 1,3-dipolar reaction. The
condition was so mild and convenient that we hope to discover
the scope of this methodology.
In order to extend the utility of this reaction, we carried out the
reaction using different kinds of aldoximes (1b–h) under the same
condition (Scheme 1). The results, summarized in Table 1, showed
that all the reactions proceeded smoothly whether the R1 was aryl,
furyl, alkyl, or ester group, and gave moderate to good yields in
short time at room temperature.15 The yield of the reaction is high-
er when R1 is a phenyl than when R1 is an aliphatic, furyl, or ester
N
N
R1
R2
R3
O
N
3
N
R2
R3
1
N
H
R1CH NOH
PhI(OAc)2
toluene, R.T.
H
PhI(OAc)2
toluene, R.T.
2
4
Scheme 1.
Table 1
Results of the reaction of C60 with aldoximes or hydrazones promoted by (diacetoxyiodo)benzene at room temperaturea,15
b
Substrate
Product
Time (min)
Yield (%)
Recovered C60 (%)
42
1a
1b
2a5a
100
51
46
N
HO
OCH3
CH3
Cl
2b5a
2c
90
90
90
90
43
39
54
55
N
HO
1c
1d
1e
44
42
37
N
HO
2d
N
HO
NO2
2e
N
HO
1f
2f5d
2g4
90
15
28
70
59
N
O
HO
N
CH3
1g
170
HO
O
C
1h
3a
2h
90
60
17
34
74
55
N
HO
OCH(CH3)2
4a16
N
N
H
OCH3
3b
3c
3d
3e
4b
45
35
35
60
20
36
19
27
72
55
70
65
N
N
N
H
NO2
4c17
4d17
4e5m
N
H
CH3O
O2N
N
N
H
N
N
H
a
All reactions were performed in toluene at room temperature; molar ratio of C60:1 or 3:PhI(OAc)2 = 1:1:1.
Isolated yield.
b

6058
H.-T. Yang et al. / Tetrahedron Letters 51 (2010) 6056–6059
Kitamura, H.; Kokubo, K.; Oshima, T. Org. Lett. 2007, 9, 4045; (g) Ioutsi, V. A.;
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R
R
C
C
N
N
A
A
N
O
A
R
Ph
PhI(OAc)2
-HOAc
C60
R
N
H
-HOAc
-PhI
C
H
I
O
C
H
A
2 or 4
A = O or ArN
1 or 3
2. Martín, N.; Altable, M.; Filippone, S.; Martín-Domenech, A.; Martínez-Alvarez,
R.; Suarez, M.; Plonska-Brzezinska, M. E.; Lukoyanova, O.; Echegoyen, L. J. Org.
Chem. 2007, 72, 3840.
Scheme 2.
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4. Meier, M. S.; Poplawska, M. J. Org. Chem. 1993, 58, 4524.
group. The electronic property of the substituent group on the phe-
nyl ring had little influence on the reaction. It is an easy and effi-
cient method to prepare fulleroisoxazolines directly from
aldoximes.
5. (a) Meier, M. S. Tetrahedron 1996, 52, 5043; (b) Meier, M. S.; Poplawska, M. J.
Am. Chem. Soc. 1994, 114, 7044; (c) Perez, L.; El-Khouly, M. E.; de la Cruz, P.;
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P.; Espíldora, E.; González-Cortés, A.; de la Hoz, A.; López-Arza, V. J. Org. Chem.
2000, 65, 8675; (e) Illescas, B.; Rife, J.; Ortuno, R. M.; Martín, N. J. Org. Chem.
2000, 65, 6246; (f) Irngartinger, H.; Weber, A.; Escher, T. Eur. J. Org. Chem. 2000,
1647; (g) Delgado, J. L.; Cardinali, F.; Espildora, E.; Torres, M. R.; Langa, F.;
Martín, N. Org. Lett. 2008, 10, 3705; (h) Oswald, F.; de la Cruz, P.; Langa, F.
Synlett 2007, 1051; (i) Gouloumis, A.; Oswald, F.; El-Khouly, M. E.; Langa, F.;
Araki, Y.; Ito, O. Eur. J. Org. Chem. 2006, 2344; (j) Langa, F.; Gomez-Escalonilla,
M. J.; Rueff, J.-M.; Duarte, T. M. F.; Nierengarten, J.-F.; Palermo, V.; Samori, P.;
Rio, Y.; Accorsi, G.; Armaroli, N. Chem. Eur. J. 2005, 11, 4405; (k) Modin, J.;
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J.; Langa, F.; Rueff, J.-M.; Oswald, L.; Nierengarten, J.-F. Tetrahedron Lett. 2002,
43, 7507; (m) Espildora, E.; Delgado, J. L.; de la Cruz, P.; de la Hoz, A.; Lopez-
Arza, V. Tetrahedron 2002, 58, 5821.
Encouraged by these results, we further extended the
PhI(OAc)2-mediated 1,3-dipolar reaction to hydrazones 3a–e and
C60 (Scheme 1). When a mixture of C60 (36.0 mg), hydrazones
3a–e (1 equiv), and PhI(OAc)2 (1 equiv) was stirred in 20 mL tolu-
ene for a designated time at room temperature, fulleropyrazolines
4a–e could also be obtained (Table 1). Yields were fair to good. The
substituent group R2 or R3 on the phenyl ring had little influence
on the yield. This makes it clear that PhI(OAc)2 is a very good oxi-
dant to mediate the 1,3-dipolar reaction of C60 with hydrazones or
aldoximes. A plausible mechanism for the generation of nitrile oxi-
des and nitrile imines is illustrated in Scheme 2.
6. de la Cruz, P.; Diaz_Ortiz, A.; Garcia, J. J.; Gomez_Escalonilla, M. J.; de la Hoz, A.;
Langa, F. Tetrahedron Lett. 1999, 40, 1587.
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Tsunenishi, Y.; Eguchi, S. Chem. Commun. 1999, 827.
All of the known products were confirmed by comparison of
their spectral data with those reported in the literature. The iden-
tification of new compounds 2c–e, 2h, and 4b was fully confirmed
by their MS, 1H NMR, 13C NMR, FT-IR, and UV–vis spectra. Take 2c
as an example. The MALDI-TOF mass spectrum of 2c showed the
molecular ion peak at m/z 853. The 1H NMR spectrum of 2c dis-
played two doublets at 7.31 and 8.03 ppm for the phenyl ring
and a singlet at 2.44 ppm for the CH3 group. In the 13C NMR spec-
trum of 2c there were 34 peaks in the range of 126–148 ppm due
to the sp2 carbons of the C60 skeleton and phenyl ring and two
peaks at about 72 and 102 ppm for the two sp3 carbons of the
C60 along with a peak at 153.18 ppm for the C@N, fully consistent
with the Cs symmetry of its molecular structure. The UV–vis spec-
trum of 2b exhibited a peak at 427 nm, which is a diagnostic
absorption for the mono-adduct of C60 at the 6:6-junction. The
other new compounds (2c–e, 2h, and 4b) were characterized in a
similar way.
8. Irngartinger, H.; Weber, A.; Escher, T. Liebigs Ann. 1996, 1845.
9. (a) Wang, G.-W.; Li, F.-B. Org. Biomol. Chem. 2005, 3, 794; (b) Li, C.; Zhang, D.;
Zhang, X.; Wu, S.; Gao, X. Org. Biomol. Chem. 2004, 2, 3464; (c) Wang, G.-W.;
Yang, H.-T.; Miao, C.-B.; Xu, Y.; Liu, F. Org. Biomol. Chem. 2006, 4, 2595.
10. (a) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 2523; (b) Müller, P.; Fruit, C.
Chem. Rev. 2003, 103, 2905; (c) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2008,
5299.
11. (a) Song, L.-P.; Zhu, S.-Z. J. Fluorine Chem. 2003, 124, 211; (b) Xia, M.; Pan, X.-J.
Synth. Commun. 2004, 34, 3521; (c) Huang, X.; Zhu, Q. Synth. Commun. 2001, 31,
111.
12. (a) Das, B.; Holla, H.; Mahender, G.; Banerjee, J.; Reddy, R. Tetrahedron Lett.
2004, 45, 7347; (b) Das, B.; Holla, H.; Mahender, G.; Venkateswarlu, K.;
Bandgar, B. P. Synthesis 2005, 1572.
13. Zhang, X.; Gan, L.; Huang, S.; Shi, Y. J. Org. Chem. 2004, 69, 5800.
14. Mendelsohn, B. A.; Lee, S.; Kim, S.; Teyssier, F.; Aulakh, V. S.; Ciufolini, M. A. Org.
Lett. 2009, 11, 1539.
15. Typical procedure for the synthesis of fulleroisoxazolines
2
and
fulleropyrazolines 4: a mixture of C60 (36.0 mg, 0.05 mmol), aldoximes 1 or
hydrazones 3 (0.05 mmol), and PhI(OAc)2 (0.05 mmol) was dissolved in 20 mL
of toluene and stirred at room temperature for a desired time. The solvent was
then evaporated in vacuo, and the residue was separated on a silica gel column
using CS2 or CS2–toluene as the eluent to afford unreacted C60 and adduct 2 or
4. Compound 2a: 1H NMR (500 MHz, CS2–CDCl3) d 8.15–8.13 (m, 2H), 7.52–7.50
(m, 3H); 2b: 1H NMR (500 MHz, CS2–CDCl3) d 8.12 (d, J = 8.8 Hz, 2H), 7.02 (d,
J = 8.8 Hz, 2H), 3.86 (s, 3H); 2c: 1H NMR (500 MHz, CS2–CDCl3) d 8.03 (d,
J = 8.2 Hz, 2H), 7.30 (d, J = 8.0 Hz, 2H), 2.44 (s, 3H); 13C NMR (125 MHz, CS2–
CDCl3, all 2C unless indicated) d 153.18 (1C, C@N), 147.72 (1C), 147.22 (1C),
146.36, 146.23, 146.21, 145.96, 145.90, 145.89, 145.58, 145.39, 145.19, 145.11,
144.88, 144.78, 144.62, 144.39, 144.07, 142.97, 142.82 (4C), 142.45 (4C),
142.32, 142,27, 142.09, 141.68, 140.78 (1C, aryl C), 140.29, 140.27, 136.98,
136.64, 129.76 (aryl C), 128.83 (aryl C), 126.23 (1C, aryl C), 104.01 (1C, sp3-C of
In summary, we have explored a useful procedure for the syn-
thesis of fulleroisoxazolines/fulleropyrazolines from fullerene and
aldoximes/hydrazones mediated by PhI(OAc)2, which represents
a significant improvement over existing methods. It is practical
with many advantages such as one-step reaction, no demanding
anhydrous operation, short reaction time, and wide utility.
C
60), 79.29 (1C, sp3-C of C60), 21.63 (1C, CH3); UV–vis (CHCl3) kmax nm 256, 316,
427, 679; FT-IR
/cmÀ1 (KBr) 2919, 2852, 1509, 1300, 1183, 979, 864, 813, 619,
Acknowledgments
m
569, 526; MS (MALDI-TOF) m/z 853; 2d: 1H NMR (500 MHz, CS2–CDCl3) d 8.13
(d, J = 8.6 Hz, 2H), 7.49 (d, J = 8.6 Hz, 2H); 13C NMR (125 MHz, CS2–CDCl3, all 2C
unless indicated) d 153.28 (1C, C@N), 147.74 (1C), 147.24 (1C), 146.38, 146.25,
146.23, 145.97, 145.92, 145.83, 145.61, 145.39, 145.21, 145.13, 144.76, 144.72,
144.47, 144.39, 144.07, 142.98, 142.84 (4C), 142.46 (4C), 142.32, 142,27,
142.09, 141.70, 140.33, 140.30, 137.02, 136.65, 130.61(1C, aryl C), 129.09 (1C,
aryl C), 129.03 (aryl C), 128.87 (aryl C), 104.16 (1C, sp3-C of C60), 79.21 (1C, sp3-
The authors are grateful for the financial support from the Na-
tional Natural Science Foundation of China (Nos. 20902039 and
20872051) and Natural Science Foundation of Jiangsu Province
(BK2009543).
C of C60); UV–vis (CHCl3) kmax nm 256, 317, 427, 678; FT-IR m
/cmÀ1 (KBr) 2921,
Supplementary data
2852, 1506, 1303, 1180, 1094, 979, 862, 823, 570, 526; MS (MALDI-TOF) m/z
873; 2e: 1H NMR (500 MHz, CS2–CDCl3) d 8.44 (d, J = 9.0 Hz, 2H), 8.37 (d,
J = 8.9 Hz, 2H); 13C NMR (125 MHz, CS2–CDCl3, all 2C unless indicated) d 151.86
(1C, C@N), 148.90 (1C, aryl C), 147.77 (1C), 147.31 (1C), 146.44, 146.30 (4C),
146.04, 145.98, 145.73, 145.28 (6C), 145.16, 144.55, 144.41, 144.00, 143.78,
143.69, 143.04, 142.93, 142.91, 142.49 (4C), 142.24 (4C), 141.98, 141.73,
140.45, 140.41, 137.31, 136.58, 135.17 (1C, aryl C), 129.59 (aryl C), 124.09 (aryl
C), 105.14, (1C, sp3-C of C60), 78.19 (1C, sp3-C of C60); UV–vis (CHCl3) kmax nm
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.09.038.
References and notes
256, 317, 426, 678; FT-IR m
/cmÀ1 (KBr) 2920, 2852, 1511, 1338, 1304, 1181,
1. For book, see: (a) Hirsch, A.; Brettreich, M. Fullerenes: Chemistry and Reactions;
Wiley-VCH Verlag GmbH & Co.: KGaA, 2005; (b) Langa, F.; Nierengarten, J.-F.
Fullerenes: Principles and Applications; RSC Publishing, 2007; For review, see: (c)
Hirsch, A. Synthesis 1995, 895; (d) Yurovskaya, M. A.; Trushkov, I. V. Russ. Chem.
Bull. Int. Ed. 2002, 51, 367; For some recent papers see: (e) Liu, F.; Du, W.; Liang,
Q.; Wang, Y.; Zhang, J.; Zhao, J.; Zhu, S. Tetrahedron Lett. 2010, 66, 5467; (f)
1105, 982, 846, 770, 747, 688, 606, 526; MS (MALDI-TOF) m/z 884; 2f: 1H NMR
(500 MHz, CS2–CDCl3) d 7.65 (d, J = 1.8 Hz, 1H), 7.38 (d, J = 3.5 Hz, 1H), 6.63 (dd,
J = 3.5, 1.8 Hz, 1H); 2g: 1H NMR (500 MHz, CS2–CDCl3) d 2.74 (s, 3H); 2h: 1H
NMR (500 MHz, CS2–CDCl3) d 5.38 (sept, J = 6.2 Hz, 1H), 1.49 (d, J = 6.2 Hz, 6H);
13C NMR (125 MHz, CS2–CDCl3, all 2C unless indicated) d 159.10 (1C, COO),

H.-T. Yang et al. / Tetrahedron Letters 51 (2010) 6056–6059
6059
147.80 (1C, C@N), 147.20 (1C), 147.17 (1C), 146.99, 146.38, 146.36, 146.34,
145.99 (4C), 145.71, 145.32, 145.20, 145.19, 144.59, 144.21, 144.20, 143.76,
143.09, 142.89 (4C), 142.84, 142.70, 142.49, 142.48, 142.41, 142.19, 141.86,
141.78, 140.28, 140.16, 136.97, 136.49, 106.04 (1C, sp3-C of C60), 79.49 (1C, sp3-
C of C60), 71.19 (1C, OCH), 21.86 (CH3); UV–vis (CHCl3) kmax nm 256, 316, 431,
141.80, 140.20, 139.62, 136.32, 136.23, 130.32 (aryl C), 129.19 (aryl C), 124.89
(1C, aryl C), 123.68 (aryl C), 114.24 (aryl C), 91.82 (1C, sp3-C of C60), 81.86 (1C,
sp3-C of C60), 55.08 (1C, OCH3); UV–vis (CHCl3) kmax nm 257, 316, 426, 679; FT-
IR m
/cmÀ1 (KBr) 2924, 2853 1606, 1594, 1579, 1510, 1489, 1325, 1255, 1176,
1100, 1022, 837, 829, 763, 752, 692, 587, 546, 526; MS (MALDI-TOF) m/z 944;
4c: 1H NMR (500 MHz, CS2–CDCl3) d 8.54 (d, J = 9.0 Hz, 2H), 8.28 (d, J = 9.0 Hz,
2H), 7.89 (d, J = 7.6 Hz, 2H), 7.43 (t, J = 7.9 Hz, 2H), 7.23 (t, J = 7.4 Hz, 1H); 4d:
1H NMR (500 MHz, CS2–CDCl3) d 8.21 (d, J = 7.5 Hz, 2H), 7.71 (d, J = 8.7 Hz, 2H),
7.44 (t, J = 7.1 Hz, 2H), 7.39 (t, J = 7.0 Hz, 1H), 6.92 (d, J = 8.7 Hz, 2H); 4e: 1H
NMR (500 MHz, CS2–CDCl3) d 8.28 (d, J = 9.4 Hz, 2H), 8.24 (d, J = 9.4 Hz, 2H),
8.19–8.17 (m, 2H), 7.52–7.50 (m, 3H).
677; FT-IR m
/cmÀ1 (KBr) 2922, 2852, 1739, 1713, 1584, 1508, 1370, 1172, 1151,
1094, 1003, 829, 767, 606, 571, 526; MS (MALDI-TOF) m/z 849; 4a: 1H NMR
(500 MHz, CS2–CDCl3) d 8.21 (d, J = 7.2 Hz, 2H), 7.87 (d, J = 7.6 Hz, 2H), 7.46 (t,
J = 7.6 Hz, 1H), 7.43 (t, J = 7.6 Hz, 2H), 7.40 (t, J = 7.9 Hz, 2H), 7.17 (t, J = 7.4 Hz,
1H); 4b: 1H NMR (500 MHz, CS2–CDCl3) d 8.16 (d, J = 8.9 Hz, 2H), 7.87 (d,
J = 7.7 Hz, 2H), 7.39 (t, J = 7.8 Hz, 2H), 7.16 (t, J = 7.4 Hz, 1H), 6.96 (d, J = 8.9 Hz,
2H), 3.84 (s, 3H); 13C NMR (125 MHz, CS2–CDCl3, all 2C unless indicated) d
160.40 (1C, Aryl C), 147.50 (1C), 147.10 (1C), 146.49, 146.29, 146.16, 145.99,
145.90, 145. 83, 145.77, 145.75, 145.62, 145.31, 145.16 (4C), 145.09, 145.07,
144.24, 144.22, 143.09, 142.83, 142.78, 142.38, 142.35, 142.28, 142.22, 142.12,
16. Matsubara, Y.; Tada, H.; Nagase, S.; Yoshida, Z.-I. J. Org. Chem. 1995, 60, 5372.
17. Reinov, M. V.; Yurovskaya, M. A.; Davydov, D. V.; Streletskii, A. V. Chem.
Heterocycl. Compd. 2004, 40, 188.