Palladium-catalyzed C-H functionalization of N-arylpropiolamides with aryliodonium salts: Selective synthesis of 3-(1-arylmethylene)oxindoles

Article abstract of DOI:10.1021/jo8008808

(Chemical Equation Presented) A selective and efficient method for the synthesis of 3-(1-arylmethylene)oxindoles by palladium-catalyzed C-H functionalization of anilides with aryliodonium salts has been developed. In the presence of Pd(OAc)₂ and Et₃N, a variety of anilides underwent the reaction with aryliodonium salts to afford the corresponding 3-(1-arylmethylene)oxindoles in moderate to good yields. It is noteworthy that the reaction can be conducted providing moderate yields even without bases. The mechanism of the reaction was also discussed.

Full text of DOI:10.1021/jo8008808

Palladium-Catalyzed C-H Functionalization of
N-Arylpropiolamides with Aryliodonium Salts: Selective Synthesis of
3-(1-Arylmethylene)oxindoles
Shi Tang,†,‡ Peng Peng,† Ping Zhong,§ and Jin-Heng Li*,†,§
College of Chemistry and Materials Science, Wenzhou UniVersity, Wenzhou, 325035, China, Key
Laboratory of Chemical Biology & Traditional Chinese Medicine Research (Ministry of Education), Hunan
Normal UniVersity, Changsha 410081, China, and Technical Institute of Physics and Chemistry, Chinese
Academy of Sciences, Beijing 100080, China
jhli@hunnu.edu.cn
ReceiVed April 23, 2008
A selective and efficient method for the synthesis of 3-(1-arylmethylene)oxindoles by palladium-catalyzed
C-H functionalization of anilides with aryliodonium salts has been developed. In the presence of Pd(OAc)2
and Et3N, a variety of anilides underwent the reaction with aryliodonium salts to afford the corresponding
3-(1-arylmethylene)oxindoles in moderate to good yields. It is noteworthy that the reaction can be
conducted providing moderate yields even without bases. The mechanism of the reaction was also
discussed.
SCHEME 1. Three Protocols for the Synthesis of Oxindoles
with Pd Catalysts
Introduction
The construction of the oxindole skelecton is of immense
interest in organic synthesis due to the prevalence of this
structure motif in a myriad of biological and pharmaceutical
compounds, and these compounds display potential utiliza-
tions in many major therapeutic areas, such as oncology,
inflammation, CNS, immunology, and endocrinology.1 As a
result, considerable effort has been devoted to the develop-
ment of new and efficient methods for the synthesis of
3-methyleneindolin-2-ones.1,2,3,4 One of the reliable ap-
proaches for the preparation of this class of compounds is
† Hunan Normal University.
‡ Chinese Academy of Sciences.
§ Wenzhou University.
(1) (a) Mohammadi, M.; McMahon, G.; Sun, L.; Tang, C.; Hirth., P.; Yeh,
B. K.; Hubbard, S. R.; Schlessinger, J. Science 1997, 276, 955. (b) Sun, L.;
Tran, N.; Liang, C.; Tang, F.; Rice, A.; Schreck, R.; Waltz, K.; Shawver, L. K.;
McMahon, G.; Tang, C. J. Med. Chem. 1999, 42, 5120. (c) Hare, B. J.; Walters,
W. P.; Caron, P. R.; Bemis, G. W. J. Med. Chem. 2004, 47, 4731. (d) Noble,
M. E. M.; Endicott, J. A.; Johnson, L. N. Science 2004, 304, 1800. (e) Liao,
J. J.-L. J. Med. Chem. 2007, 50, 409. (f) Drugs Future 1990,15, 898. (g)
Robinson, R. P.; Reiter, L. A.; Barth, W. E.; Campeta, A. M.; Cooper, K.; Cronin,
B. J.; Destito, R.; Donahue, K. M.; Falkner, F. C.; Fiese, E. F.; Johnson, D. L.;
Kuperman, A. V.; Liston, T. E.; Malloy, D.; Martin, J. J.; Mitchell, D. Y.; Rusek,
F. W.; Shamblin, S. L.; Wright, C. F. J. Med. Chem. 1996, 39, 10. (h) Andreani,
A.; Burnelli, S.; Granaiola, M.; Leoni, A.; Locatelli, A.; Morigi, R.; Rambaldi,
M.; Varoli, L.; Kunkel, M. W. J. Med. Chem. 2006, 49, 6922. (i) Graczyk, P. P.
J. Med. Chem. 2007, 50, 5773.
palladium-catalyzed domino reactions (Scheme 1).2 Player
and co-workers,2a for instance, demonstrated a Heck-car-
5476 J. Org. Chem. 2008, 73, 5476–5480
10.1021/jo8008808 CCC: $40.75 2008 American Chemical Society
Published on Web 06/17/2008

SelectiVe Synthesis of 3-(1-Arylmethylene)oxindoles
TABLE 1. Screening Optimal Conditionsa
bocyclization/Suzuki-coupling sequence protocol for the
synthesis of (E)-3,3-(diarylmethylene)indolinones in the
presence of Pd(PPh3)4 and CuTC (copper(I) thiophene-2-
carboxylate), but the selectivity is not desirable. Subse-
quently, Takemoto and co-workers2b have reported a selective
method for the synthesis of oxindoles by Pd(OAc)2/PPh3-
catalyzed Heck/Suzuki, Heck/Heck, and Heck/carbonylation/
Suzuki domino reactions of N-(2-iodophenyl)propiolamides
with arylboronic acids or alkenes. However, the above two
methods require the use of 2-iodoanilides as the starting
materials besides the requirement of some additives, such
as phosphine ligands and CuTC (eq 1 in Scheme 1). To
overcome these drawbacks, Zhu and co-workers have devel-
oped a Pd(OAc)2-catalyzed domino carbopalladation/C-H
activation/C-C bond-forming process that uses an anilide
sp2 C-H bond as one of the coupling partners for selectively
synthesizing 3-(diarylmethylene)oxindoles (eq 2).2c,d Very
recently, we developed a novel palladium-catalyzed C-H
functionalization process for the preparation of (E)-(2-
oxindolin-3-ylidene)phthalimides and (E)-(2-oxoindolin-3-
ylidene)methyl acetates in the presence of PhI(OAc)2 (eq
3).2i,j We were interested to observe that 3-(1-phenylmeth-
ylene)oxindoles were isolated as byproduct in our previous
experiments. This prompts us to explore the feasibility of
the use of both anilides and aryliodonium salts as the coupling
partners to construct the oxindole skelecton. Here, we wish
to report a simple and efficient protocol for the synthesis of
3-(1-arylmethylene)oxindoles by palladium-catalyzed C-H
functionalization of anilides with aryliodonium salts (eq 4).
entry
additive
t (°C)
solvent
MeCN
MeCN
MeCN
MeCN
MeCN
ClCH2CH2Cl
THF
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
THF/MeCN (1:4)
yield (%)
1b
2b
3
80
100
100
120
100
100
100
100
100
100
100
100
100
100
100
100
17
35
54
55
55
5
53
59
57
51
79
19
76
77
60
0
4
5c
6
7
8
9
10
11
12
13d
14e
15f
16g
NaOAc
NaHCO3
Et3N
NMP
Et3N
Et3N
Et3N
Et3N
a Reaction conditions: 1a (0.2 mmol), Pd(OAc)2 (5 mol %),
PhI(OAc)2 (2 equiv), and additive (2 equiv) in solvent (3 mL) at 100 °C
for 10 h. b PhI(OAc)2 (1.2 equiv). c PhI(OAc)2 (3 equiv). d PdCl2 (5 mol
%) instead of Pd(OAc)2. e Pd(CH3CN)2Cl2 (5 mol %) instead of Pd(OAc)2.
f Pd(PPh3)4 (5 mol %) instead of Pd(OAc)2. g Without Pd(OAc)2.
of PhI(OAc)2 affected the reaction slightly. Subsequently, the
solvent effect was examined (entries 5-8, Table 1). We found
that a mixture of THF and MeCN provided the best results (entry
8, Table 1). A number of bases, such as NaOAc, NaHCO3, Et3N,
and NMP (4-(N,N-dimethyl)pyridine), were also tested (entries
9-12, Table 1). NaOAc, the reported efficient base, displayed
no activity for the reaction (entry 9, Table 1), and Et3N provided
the best results (entry 11, Table 1). To our surprise, both
NaHCO3 and NMP disfavored the reaction (entries 10 and 12,
Table 1). Finally, a series of other Pd catalysts, including PdCl2,
Pd(CH3CN)2Cl2, and Pd(PPh3)4, were investigated (entries
13-15, Table 1). Identical results to those of Pd(OAc)2 were
obtained by using PdCl2 or Pd(CH3CN)2Cl2, but Pd(PPh3)4 was
less efficient. It is noteworthy that no reaction takes place
without Pd catalysts (entry 16, Table 1).
Results and Discussion
As listed in Table 1, the optimal reaction conditions for the
reactions of N-methyl-N,3-diphenylpropiolamide (1a) with PhI(O-
Ac)2 (2a) were screened. In the presence of 5 mol % of
Pd(OAc)2, treatment of amide 1a with 2a in MeCN at 80 °C
afforded the target product 3 in a 17% yield after 10 h (entry 1,
Table 1). The results showed that both the reaction temperature
and the amount of PhI(OAc)2 affected the yield to some extent
(entries 2-4, Table 1). It turned out that 100 °C combined with
2 equiv of PhI(OAc)2 was the best reaction conditions for the
reaction, and both further increasing temperature and loading
With the standard reaction conditions in hand, we then
focused on the examination of scope of N-arylpropiolamides
by reacting with PhI(OAc)2 (Table 2). We found that N-benzyl-
N,3-diphenylpropiolamide (1b) still underwent the reaction with
PhI(OAc)2, Pd(OAc)2, and Et3N in THF/MeCN to afford the
target product 4 in 82% yield (entry 1, Table 2), but the N-benzyl
group replaced by the acetyl or hydrogen group was found to
be unsuitable for the C-H functionalization reaction (entries 2
and 3, Table 2). Subsequently, the effect of substitutes on the
N-aryl ring was evaluated, and the results demonstrated that a
series of functional substitutes, such as chloro, bromo, nitro,
methoxy, or methyl groups, on the aromatic motif were tolerated
well. Amides 1f-j, bearing a chloro group or two chloro groups
on the N-aryl ring, all worked with PhI(OAc)2 well in good
yields under the standard conditions (entries 4-6, Table 2). The
C-H functionalization reaction of substrate 1h having an
o-bromo group was still conducted successfully in 53% yield
(entry 7, Table 2). To our delight, the other amides with either
electron-deficient or electron-rich N-aryl groups underwent the
reaction smoothly to afford the corresponding target products
(2) For papers on the synthesis of oxindoles with Pd catalysts, see (a) Cheung,
W. S.; Patch, R. J.; Player, M. R. J. Org. Chem. 2005, 70, 3741. (b) Yanada, R.;
Obika, S.; Inokuma, T.; Yanada, K.; Yamashita, M.; Ohta, S.; Takemoto, Y. J.
Org. Chem. 2005, 70, 6972. (c) Pinto, A.; Neuville, L.; Retailleau, P.; Zhu, J.
Org. Lett. 2006, 8, 4927. (d) Pinto, A.; Neuville, L.; Zhu, J. Angew. Chem., Int.
Ed. 2007, 46, 3291. (e) Couty, S.; Lie´gault, B.; Meyer, C.; Cossy, J. Org. Lett.
2004, 6, 2511. (f) D’Souza, D. M.; Rominger, F.; Mu¨ller, T. J. J. Angew. Chem.,
Int. Ed. 2005, 44, 153. (g) Tang, S.; Yu, Q.-F.; Peng, P.; Li, J.-H.; Zhong, P.;
Tang, R.-Y. Org. Lett. 2007, 9, 3413. (h) Yanada, R.; Obika, S.; Oyama, M.;
Takemoto, Y. Org. Lett. 2004, 6, 2825. (i) Tang, S.; Peng, P.; Pi, S.-F.; Liang,
Y.; Wang, N.-X.; Li, J.-H. Org. Lett. 2008, 10, 1179. (j) Tang, S.; Peng, P.;
Wang, Z.-Q.; Tang, B.-X.; Deng, C.-L.; Li, J.-H.; Zhong, P.; Wang, N.-X. Org.
Lett. 2008, 10, 1875.
(3) For papers on the synthesis of oxindoles with Rh as the catalysts and
2-alkynylaryl isocyanates as the substrates, see: (a) Shintani, R.; Yamagami, T.;
Hayashi, T. Org. Lett. 2006, 8, 4799. (b) Miura, T.; Takahashi, Y.; Murakami,
M. Org. Lett. 2007, 8, 5075. (c) Miura, T.; Takahashi, Y.; Murakami, M. Org.
Lett. 2008, 10, 1743.
(4) For papers on the other methods for the synthesis of oxindoles, see:(a)
Mori, M.; Ban, Y. Tetrahedron Lett. 1979, 20, 1133. (b) Sun, L.; Liang, C.;
Shirazian, S.; Zhou, Y.; Miller, T.; Cui, J.; Fukuda, J. Y.; Chu, J.-Y.; Nematalla,
A.; Wang, X.; Chen, H.; Sistla, A.; Luu, T. C.; Tang, F.; Wei, J.; Tang, C.
J. Med. Chem. 2003, 46, 1116. (c) Wang, L.; Zhang, Y.; Hu, H.-Y.; Fun, H. K.;
Xu, J.-H. J. Org. Chem. 2005, 70, 3805. (d) Kalinski, C.; Umkehrer, M.; Schmidt,
J.; Ross, G.; Kolb, J.; Burdack, C.; Hiller, W.; Hoffmann, S. D. Tetrahedron
Lett. 2006, 47, 4683. (e) Xing, X.; Wu, J.; Luo, J.; Dai, W.-M. Synlett 2006,
2099. (f) Yang, T.-M.; Liu, G. J. Comb. Chem. 2007, 9, 86.
J. Org. Chem. Vol. 73, No. 14, 2008 5477

Tang et al.
TABLE 2. Palladium-Catalyzed C-H Functionalization Reactions of Amides 1 with PhI(OAc)2 (2a)a
a Reaction conditions: 1 (0.2 mol), Pd(OAc)2 (5 mol%), PhI(OAc)2 (2 equiv), and Et3N (2 equiv) in THF/CH3CN (v/v 1:4, 3 mL) was stirred under
air at 100 °C.
in good yields (entries 8 and 9, Table 2). For example, N-(2,4-
dimethoxyphenyl)-N-methyl-3-phenylpropiolamide (1j), a bulky
and electron-rich amide, was treated with PhI(OAc)2, Pd(OAc)2,
and Et3N providing 74% yield (entry 9, Table 2). Finally,
substitutes at the terminal of the Ct C bond of N-methyl-N-
arylpropiolamides were also evaluated. The results showed that
N-methyl-N-arylpropiolamides 1k-m, having either a aryl group
or a alkyl group, underwent the reaction with PhI(OAc)2 in good
yields (entries 10-12, Table 2). However, N-methyl-N-phenyl-
propiolamide (1n) was not a suitable substrate under the standard
conditions (entry 13, Table 2).
The scope of aryliodonium diacetates was also explored, and
the results are summarized in Table 3. The results showed that
a variety of aryliodonium diacetates, either electron-deficient
or electron-rich, all underwent the C-H functionalization
reaction with N-methyl-N,3-diphenylpropiolamide (1a) and
Pd(OAc)2 smoothly in moderate to good yields (entries 1-9,
Table 3). (p-Methylbenzene)iodonium diacetate (2b), for in-
stance, was treated with amide 1a smoothly to afford the target
product 17 in 75% yield (entry 1, Table 3). Interestingly, the
bulky iodonium diacetate 2j reacted with amide 1a was still
conducted successfully in 27% yield (entry 9, Table 3). The
other amide, N-methyl-N-phenylbut-2-ynamide (1m), was also
reacted with (p-acetylbenzene)iodonium diacetate (2i) smoothly
in 60% yield under the standard conditions (entry 10, Table 3).
As demonstrated in Scheme 2, a series of diphenyliodonium
salts were also tested in the presence of Pd(OAc)2. The results
indicated that both diphenyliodonium chloride and diphenyli-
odonium bromide also displayed high efficient activity for the
C-H functionalization reaction with N-methyl-N,3-diphenyl-
propiolamide (1a) with Et3N as the base. However, the other
diphenyliodonium salts, including [Ph2I]I, [Ph2I]OTf, and
[Ph2I]BF4, were less active in terms of the yields. Interestingly,
both diphenyliodonium chloride and diphenyliodonium bromide
are more efficient when Et3N was replaced by NaOAc.
Four controlled reactions were conducted to elucidate the
mechanism, and the results are summarized in Scheme 3. We
found that treatment of N-methyl-N,3-diphenylpropiolamide (1a)
5478 J. Org. Chem. Vol. 73, No. 14, 2008

SelectiVe Synthesis of 3-(1-Arylmethylene)oxindoles
TABLE 3. Palladium-Catalyzed C-H functionalization Reactions
SCHEME 4. Two Possible Mechanisms
of Amides (1) with Aryliodonium Diacetates (2)a
entry
R
Ar
time (h) isolated yield (%)
1
2
3
4
5
6
7
8
9
Ph (1a) p-CH3C6H4 (2b)
Ph (1a) o-CH3C6H4 (2c)
Ph (1a) p-CH3OC6H4 (2d)
Ph (1a) o-CH3OC6H4 (2e)
Ph (1a) p-NO2C6H4 (2f)
Ph (1a) o-ClC6H4 (2g)
Ph (1a) m-CH3COC6H4 (2h)
Ph (1a) p-CH3COC6H4 (2i)
Ph (1a) 2,4,6-(CH3)3C6H4 (2j)
Me (1n) p-CH3COC6H4 (2i)
9
20
20
24
24
15
24
24
48
24
75(17)
54(18)
73(19)
48(20)
63(21)
82(22)
56(23)
65(24)
27(25)
60(26)
10
a All reaction were run under the following conditions: 1 (0.2 mol),
Pd(OAc)2 (5 mol %), ArI(OAc)2 2 (2 equiv), and Et3N (2 equiv) in
THF/CH3CN (v/v 1:4, 5 mL) under air at 100 °C.
SCHEME 2. Palladium-Catalyzed C-H Functionalization
Reactions of N-Methyl-N,3-diphenylpropiolamide(1a) with
Ph2IY (2)
7
1
was determined in situ by H NMR analysis. The reaction of
PhI(OAc)2 with 2 equiv of Et3N was conducted in CDCl3 at
room temperature. The results showed that 38% of PhI(OAc)2
was decomposed by Et3N to PhI after about 1 h, and 75% of
PhI(OAc)2 was decomposed after 10 h.
Based on the previously reported mechanisms2,3,5 and the
present results.7 the C-H functionalization reaction may proceed
via two possible processes as outlined in Scheme 4. In the
presence of base (Et3N), ArI(OAc)2 is readily decomposed to
generate ArI, and ArI then reacts with amide 1 via Zhu’s process
to afford the target product. However, we cannot rule out another
possible process because the reaction can occur without bases:
Coordination of PdII with alkyne and nitrogen readily occurred
to afford intermediate A, followed by cis-addition of intermedi-
ate A with Pd and ArI(OAc)2 to afford intermediate B in the
absence or presence of Et3N. The PdII intermediate B is then
oxidized by ArI(OAc)2 to give a PdIV intermediate C. The PdIV
intermediate D is formed by activation of the o-C-H bond of
intermediate C.5 The reductive elimination of intermediate D
occurs readily to yield the target product and the active PdII
species.
SCHEME 3. Four Controlled Reactions
Conclusions
In summary, we have developed a novel protocol for the
synthesis of 3-(1-arylmethylene)oxindoles via palladium-
catalyzed C-H functionalization of N-arylpropiolamides with
with iodobenzene and Pd(OAc)2 afforded the desired product
3 in 11% GC yields under the present conditions (Zhu’s
conditions: Pd(OAc)2, NaOAc, and DMF at 110 °C),2c and
PdCl2 provided only 4% GC yield of 3 after 10 h. While
satisfactory yields were obtained from the reaction of amide
1a with PhI by using Pd(OAc)2/PPh3 or Pd(PPh3)4 as the catalyst
(Zhu’s conditions: Pd(PPh3)4, NaOAc, and DMF at 110 °C),2d
the results of Table 1 showed that Pd(PPh3)4 instead of Pd(OAc)2
reduced the yield of the reaction between amide 1a with
PhI(OAc)2 (entry 15, Table 1). Compared with the Zhu’s results,
the results suggested that the present reaction is conducted via
a different process from that of Zhu to some extent. To further
elucidate the mechanism, the reaction of PhI(OAc)2 with Et3N
(5) For selected recent reviews and papers on the PdII/PdIV process, see:(a)
Yu, J.-Q.; Giri, R.; Chen, X. Org. Biomol. Chem. 2006, 4, 4042. (b) Deprez,
N. R.; Sanford, M. S. Inorg. Chem. 2007, 46, 1924. (c) Thu, H.-Y.; Yu, W.-Y.;
Che, C.-M. J. Am. Chem. Soc. 2006, 128, 9048. (d) Liu, G.; Stahi, S. S. J. Am.
Chem. Soc. 2006, 128, 7179. (e) Tong, X.; Beller, M.; Tse, M. K. J. Am. Chem.
Soc. 2007, 129, 4906. (f) Welbes, L. L.; Lyons, T. W.; Cychosz, K. A.; Sanford,
M. S. J. Am. Chem. Soc. 2007, 129, 5836. (g) Whitfield, S. R.; Sanford, M. S.
J. Am. Chem. Soc. 2007, 129, 15142. (h) Muniz, K. J. Am. Chem. Soc. 2007,
129, 14542. (i) Muniz, K.; Hovelmann, C. H.; Streuff, J. J. Am. Chem. Soc.
2008, 130, 763.
(6) The structure of the products were unambiguously assigned by X-ray
analysis of the product 3, see the Supporting Information. The configuration of
the tetrasubstituted double bond was determined according to the authoritative
5-H and/or 8-H shift data of oxindoles in refs 2-4.
(7) 1H NMR spectra of the reaction of PhI(OAc)2 with Et3N are summarized
in the Supporting Information.
J. Org. Chem. Vol. 73, No. 14, 2008 5479

Tang et al.
Hz, 2H), 7.10 (d, J ) 8.0 Hz, 2H), 7.04 (t, J ) 7.6 Hz, 1H), 6.68
(d, J ) 8.0 Hz, 1H), 6.63 (t, J ) 7.2 Hz, 1H), 6.40 (d, J ) 7.6 Hz,
1H), 4.88 (s, 2H), 2.30 (s, 3H); 13C NMR (100 MHz) δ 166.8,
154.9, 142.5, 141.4, 139.9, 137.1, 133.3, 130.2, 129.4 (2C), 129.2,
129.0, 128.7, 128.4, 127.9, 127.5, 124.1, 123.4, 123.2, 121.4, 108.7,
43.3, 21.1; LRMS (EI, 70 eV) m/z (%) 401 (M+, 100); HRMS
(EI) for C29H23NO (M+) calcd 401.1780, found 401.1779.
aryliodonium salts. In the presence of Pd(OAc)2 and Et3N, a
variety of anilides underwent the reaction with aryliodonium
salts to afford the corresponding 3-(1-arylmethylene)oxindoles
in moderate to good yields. Efforts to study the detailed
mechanism and extend the application of the transformation in
organic synthesis are underway in our laboratory.
Experimental Section
Acknowledgment. We would like to thank the Program of
Science and Technology of Zhejiang Province (No. 2008C33065),
Zhejiang Provincial Natural Science Foundation of China
(Y407116), Specialized Research Fund for the Doctoral Program
of Higher Education (No. 20060542007), National Natural
Science Foundation of China (No. 20572020), and New Century
Excellent Talents in University (No. NCET-06-0711) for
financial support.
Typical Experimental Procedure for the Palladium-Catalyzed
C-H Functionalization of N-Arylpropiolamides with Aryliodo-
nium Salts. A mixture of propiolamides 1 (0.2 mmol), aryliodonium
salt 2 (2 equiv), Pd(OAc)2 (5 mol %), and Et3N (2 equiv) in THF/
CH3CN (v/v 1:4, 3 mL) was stirred under air at 100 °C for the
desired time until complete consumption of starting material as
monitored by TLC. Then the mixture was washed with saturated
NaCl and extracted with diethyl ether. The organic layers were dried
with Na2SO4 and evaporated under vacuum, the residue was purified
by flash column chromatography to afford the pure product (hexane/
ethyl acetate).
Supporting Information Available: General experimental
procedures, characterization data for compounds 3, 4, 7-15,
and 17-26, and copies of spectra. This material is available
free of charge via the Internet at http://pubs.acs.org.
1-(p-Methylbenzyl)-3-(diphenylmethylene)indolin-2-one (4).
Yellow solid, mp 171.2-172.3 °C (uncorrected); H NMR (400
MHz) δ 7.44-7.42 (m, 3H), 7.38-7.32 (m, 7H), 7.22 (d, J ) 8.0
1
JO8008808
5480 J. Org. Chem. Vol. 73, No. 14, 2008