Synthesis of 1-aroyl-1,2-dihydro-3H-indol-3-ones via cyclization of N-[2-(2-chloroacetyl)phenyl]benzamides with triethylamine in the presence of DI-tert-butyl dicarbonate

Article abstract of DOI:10.3987/COM-16-13450

1-Aroyl-1,2-dihydro-3H-indol-3-ones can now be conveniently obtained from 2-aryl-4-(Z)-(chloromethylidene)-4H-3,1-benzoxazines using an easy operated three-step sequence under mild conditions. Thus, the starting materials are hydrolyzed with dilute hydroc

Full text of DOI:10.3987/COM-16-13450

HETEROCYCLES, Vol. 92, No. 6, 2016, pp. -. © 2016 The Japan Institute of Heterocyclic Chemistry
Received, 29th February, 2016, Accepted, 4th April, 2016, Published online, 8th April, 2016
DOI: 10.3987/COM-16-13450
SYNTHESIS OF 1-AROYL-1,2-DIHYDRO-3H-INDOL-3-ONES VIA
CYCLIZATION OF N-[2-(2-CHLOROACETYL)PHENYL]BENZAMIDES
WITH TRIETHYLAMINE IN THE PRESENCE OF DI-tert-BUTYL
DICARBONATE
Kazuhiro Kobayashi,* Daiki Kado, and Kohei Nishikawa
Division of Applied Chemistry, Department of Chemistry and Biotechnology,
Graduate School of Engineering, Tottori University, 4-101 Koyama-minami,
Tottori 680-8552, Japan; E-mail: kkoba@chem.tottori-u.ac.jp
Abstract – 1-Aroyl-1,2-dihydro-3H-indol-3-ones can now be conveniently
obtained from 2-aryl-4-(Z)-(chloromethylidene)-4H-3,1-benzoxazines using an
easy operated three-step sequence under mild conditions. Thus, the starting
materials are hydrolyzed with dilute hydrochloric acid at 0 ˚C to
N-[2-(2-chloroacetyl)phenyl]benzamides, of which treatment with triethylamine
in the presence of di-tert-butyl dicarbonate at room temperature, followed by
deprotection with trifluoroacetic acid at room temperature, provides the desired
products.
INTRODUCTION
1,2-Dihydro-3H-indol-3-one derivatives are an important class of heterocycles. Some of these derivatives
have been utilized in the synthesis of a number of more structurally complex and/or biologically
important compounds.1 An interesting natural product having this skeleton has been found in nature.2
Accordingly, some practical methods for the preparation of this class of heterocycles have been
developed.3-6 Recently, Shu et al. demonstrated the use of gold-catalyzed intermolecular oxidation of
o-ethynylanilines,7 and more recently Gandy et al. reported a synthesis of 1-acetyl-1,2-dihydro-3H-indol-
3-ones by the reaction of N-(2-cyanophenyl)glycine ethyl esters with acetic anhydride.8 On the other hand,
we previously reported that N-(2,2-dichloroethenyl)(het)arenecarboxamides underwent intramolecular
cyclization
on
treatment
with
sodium
hydride
to
afford
2-(het)aryl-4-(Z)-
(chloromethylidene)-4H-3,1-benzoxazines (1).9 As an extensive investigation of this study, we wish to
describe here a convenient synthetic approach to 1,2-dihydro-3H-indol-3-one derivatives. We have found

that 1-(het)aroyl-1,2-dihydro-3H-indol-3-ones (4) can be formed by cyclization of
N-[2-(2-chloroacetyl)phenyl](het)arenecarboxamides (2), which can be readily obtained by acid
hydrolysis of 1.
RESULTS AND DISCUSSION
Our synthesis of 4 from 1 was carried out according to the sequence illustrated in Scheme 1. The first step
in the present procedure was hydrolysis of 1, which were easily prepared from
2-(2,2-dichloroethenyl)benzenamines according to the procedure reported previously by us.9 These
amines were easily accessible from readily available starting materials, 2-nitrobenzaldehydes, by the
established procedure.10 Hydrolysis of 1 with 10% aqueous hydrochloric acid in THF proceeded smoothly
and cleanly at 0 ˚C to give 2 in generally good yields as compiled in Table 1, while the yield of the
pyridine-3-carboxamide derivative (2i) was moderate (Entry 9).
Cl
O
OBoc
R
R
Cl
(Boc)2O
R
10% aq. HCl
THF, 0 ˚C
O
N
COAr
2 Et3N, THF, rt
NHCOAr
N
Ar
3
2
1
O
R
TFA, rt
N
COAr
4
Scheme 1
Table 1. Preparation of 1,2-dihydro-3H-indol-3-ones (4)
Entry
1
2
Yield/%a
94
98
4
Yield/%a,b
1
2
3
1a (R = H, Ar = Ph)
1b (R = H, Ar = m-Tol)
1c (R = H, Ar = p-Tol)
2a
2b
2c
2d
2e
2f
2g
2h
2i
4a
4b
4c
4d
4e
4f
4g
4h
4i
63
59
60
57
59
75
59
62
56
60
35c
97
91
93
94
90
98
56
72
4
5
6
7
8
9
10
11
1d (R = H, Ar = 2-ClC6H4)
1e (R = H, Ar = 4-ClC6H4)
1f (R = H, Ar = 2,4-Cl2C6H4)
1g (R = H, Ar = 3-MeOC6H4)
1h (R = H, Ar = thiophen-2-yl)
1i (R = H, Ar = pyridin-3-yl)
1j (R = Cl, Ar = 4-ClC6H4)
2j
2k
4j
4k
1k (R = OMe, Ar = Ph)
83
a
b
c
Yields of isolated products. Overall yields from 2. This products was obtained directly from 2k on
treatment with NaH in DME at 0 ˚C.

The second part of the sequence was cyclization of 2. In 1979, Sugasawa et al. reported the synthesis of
1-acetyl-1,2-dihydro-3H-indol-3-one by the reaction of N-[(2-chloroacetyl)phenyl]acetamide with sodium
hydride in 1,2-dimethoxyethane (DME) at 0 ˚C in relatively good yield.5 We first subjected substrate (2a)
to these reaction conditions. Unfortunately, however, the reaction did proceed uncleanly to give the
desired corresponding product 1-benzoyl-1,2-dihydro-3H-indol-3-one (4a) only in 15% yield. The
reaction was then conducted using triethylamine in DMF at 0 ˚C; only 10% yield of 4a was obtained.
Subsequently, cyclization of 2a with two equivalents of triethylamine in DMF at room temperature in the
presence of an equivalent of di-tert-butyl dicarbonate was attempted. By using these conditions,
compounds 2a was converted into 1-benzoyl-1H-indol-3-yl 1,1-dimethylethyl carbonate (3a) in 69%
yield. It is thought that the protection as 1,1-dimethylethyl carbonate depresses the self-condensation of
the initially formed 4a. This carbonate was converted into 4a in an almost quantitative yield through
deprotection with trifluoroacetic acid (TFA) at room temperature.
In order to make this methodology more practical, the two steps were carried out without isolation of 3a.
Thus, the crude reaction mixture containing 3a was subjected to the deprotection without any purification
after aqueous workup. The desired product 4a was isolated in 63% overall yield from 2a (Table 1, Entry
1). Other nine N-[2-(2-chloroacetyl)phenyl] amides (2b–2j) were similarly converted into the
corresponding 1-(het)aroyl-1,2-dihdro-3H-indol-3-ones (4b–4j) in comparable yields (Entries 2-10).
It is notable that the treatment of N-[2-(2-chloroacetyl)phenyl]-4-methoxybenzamide (2k) with
di-tert-butyl dicarbonate under the above-mentioned cyclization conditions resulted in the formation of a
considerably intractable mixture of products and that only a trace amount of the corresponding
3-(tert-butoxycarbonyloxy)-1H-indole derivative (3k) was observed in it as judged by TLC analyses on
silica gel. However, when 2k was treated with sodium hydride in 1,2-dimethoxyethane (DME) at 0 ˚C,
1-benzoyl-5-methoxy-1,2-dihydro-3H-indol-3-one (4k) was directly obtained albeit in relatively low
yield (Scheme 2). This different reactivity of 2k from the other N-[2-(2-chloroacetyl)phenyl] amides
(2a–2j) is incomprehensible; we cannot provide any reasons for it.
O
O
MeO
MeO
Cl
NaH, DME, 0 ˚C
N
COPh
NHCOPh
4k
2k
Scheme 2
In conclusion, a convenient procedure for the synthesis of 1-(het)aroyl-1,2-dihydro-3H-indol-3-ones has
been developed. As the procedure is experimentally very simple and the reactions can be run under mild
reaction conditions, it is of value in organic synthesis. Further elaboration of the aforementioned

N-[(2-chloroacetyl)phenyl](het)arenecarboxamides to functionalized heterocycles, hard to prepare by
previous methods, is under way.
EXPERIMENTAL
All melting points were obtained on a Laboratory Devices MEL-TEMP II melting apparatus and are
1
uncorrected. IR spectra were recorded with a Perkin–Elmer Spectrum 65 FTIR spectrophotometer. H
13
NMR and C NMR spectra were recorded in CDCl3 using TMS as an internal reference with a JEOL
ECP500 FT NMR spectrometer operating at 500 and 125 MHz, respectively. High-resolution MS spectra
were measured by a Thermo Scientific Exactive spectrometer (DART or ESI, positive) or a JEOL
JMS-T100GCV (EI, TOF; 70eV) spectrometer. Elemental analyses were performed with an Elementar
Vario EL II instrument. TLC was carried out on Merck Kieselgel 60 PF254. Column chromatography was
performed using WAKO GEL C-200E. All of the organic solvents used in this study were dried over
appropriate drying agents and distilled prior to use.
Starting Materials. 2-(2,2-Dichloroethenyl)benzenamine10 and 5-methoxy-2-nitrobenzaldehyde11 were
prepared according to the reported procedure. All other chemicals used in this study were commercially
available.
4-Chloro-2-(2,2-dichloroethenyl)benzenamine.
This
compound
was
prepared
from
5-chloro-2-nitrobenzaldehyde by the same
procedure for
the
preparation
of
2-(2,2-dichloroethenyl)benzenamine from 2-nitrobenzaldehyde.10 Yield: 69%; a yellow oil: Rf 0.42
(AcOEt/hexane 1:5); IR (neat) 3474, 3391, 1623 cm–1; 1H NMR δ 3.70 (br s, 2H), 6.64 (d, J = 8.6 Hz, 1H),
6.68 (s, 1H), 7.09 (dd, J = 8.6, 2.3 Hz, 1H), 7.31 (d, J = 2.3 Hz, 1H). HR-MS (EI). Calcd for C8H6Cl3N
(M): 220.9566. Found: m/z 220.9574.
2-(2,2-Dichloroethenyl)-4-methoxybenzenamine. This compound was prepared from 5-methoxy-2-
nitrobenzaldehyde11 by the same procedure for the preparation of 2-(2,2-dichloroethenyl)benzenamine
from 2-nitrobenzaldehyde.10 Yield: 60%; a yellow oil: Rf 0.30 (CH2Cl2/hexane 5:1); IR (neat) 3437, 3364,
3225, 1609 cm–1; 1H NMR δ 3.45 (br s, 2H), 3.76 (s, 3H), 6.67 (d, J = 8.6 Hz, 1H), 6.76 (dd, J = 9.2, 2.9
Hz, 1H), 6.78 (s, 1H), 6.95 (d, J = 2.9 Hz, 1H). HR-MS (EI). Calcd for C9H9Cl2NO (M): 217.0061.
Found: m/z 217.0053.
2-Aryl-4-(Z)-(chloromethylidene)-4H-3,1-benzoxazines (1). These compounds were prepared from the
respective
2-(2,2-dichloroethenyl)benzenamines
and
(het)aroyl
chlorides,
via
N-[2-(2,2-dichloroethenyl)phenyl](het)arenecarboxamides, according to the reported procedure.9 The
physical, spectral, and analytical data for new compounds follow.
N-[2-(2,2-Dichloroethenyl)phenyl]-3-methylbenzamide: yield 82%; a white solid; mp 86–88 ˚C
(hexane/CH2Cl2); IR (KBr) 3198, 1639, 1601 cm–1; 1H NMR δ 2.46 (s, 3H), 6.90 (s, 1H), 7.22 (t, J = 7.4

Hz, 1H), 7.40–7.45 (m, 5H), 7.65 (d, J = 6.3 Hz, 1H), 7.71 (s, 1H), 8.08 (d, J = 8.0 Hz, 1H). Anal. Calcd
for C16H13Cl2NO: C, 62.76; H, 4.28; N, 4.57. Found: C, 62.74; H, 4.46; N, 4.51.
4-(Z)-(Chloromethylidene)-2-(3-methylphenyl)-4H-3,1-benzoxazine (1b): yield: 62%; a white solid;
mp 105–107 ˚C (hexane/CH2Cl2); IR (KBr) 3114, 1638, 1611 cm–1; 1H NMR δ 2.44 (s, 3H), 5.96 (s, 1H),
7.20 (td, J = 8.0, 2.3 Hz, 1H), 7.35–7.39 (m, 5H), 8.05 (d, J = 8.0 Hz, 1H), 8.06 (s, 1H); 13C NMR δ 21.43,
92.44, 119.41, 121.12, 125.19, 126.87, 127.68, 128.36, 128.47, 130.78, 130.91, 132.85, 138.17, 138.26,
146.22, 154.22. HR-MS (EI). Calcd for C16H12ClNO (M): 269.0607. Found: m/z 269.0617.
N-[2-(2,2-Dichloroethenyl)phenyl]-4-methylbenzamide: yield: 83%; a white solid; mp 142–144 ˚C
(hexane/CH2Cl2); IR (KBr) 3309, 1641, 1612 cm–1; 1H NMR δ 2.45 (s, 3H), 6.89 (s, 1H), 7.22 (dd, J = 8.0,
7.4 Hz, 1H), 7.32 (d, J = 8.0 Hz, 2H), 7.41 (dt, J = 8.0, 7.4 Hz, 1H), 7.44 (d, J = 8.0 Hz, 1H), 7.71 (br s,
1H), 7.78 (d, J = 8.0 Hz, 2H), 8.09 (d, J = 8.0 Hz, 1H). HR-MS (EI). Calcd for C16H13Cl2NO (M):
305.0374. Found: m/z 305.0376.
4-(Z)-(Chloromethylidene)-2-(4-methylphenyl)-4H-3,1-benzoxazine (1c): yield: 72%; a white solid;
1
mp 97–99 ˚C (hexane/CH2Cl2); IR (KBr) 3121, 1639, 1613 cm–1; H NMR δ 2.42 (s, 3H), 5.94 (s, 1H),
7.19 (ddd, J = 8.0, 7.4, 1.7 Hz, 1H), 7.28 (d, J = 8.6 Hz, 2H), 7.33–7.36 (m, 3H), 8.14 (d, J = 8.6 Hz, 2H);
13C NMR δ 21.66, 92.33, 119.34, 121.11, 126.78, 127.52, 127.98, 128.09, 129.19, 130.89, 138.36, 142.58,
146.24, 154.17. Anal. Calcd for C16H12ClNO: C, 71.25; H, 4.48; N, 5.19. Found: C, 70.99; H, 4.52; N,
5.13.
2-Chloro-N-[2-(2,2-dichloroethenyl)phenyl]benzamide: yield: 89%; a white solid; mp 90–93 ˚C
1
(hexane/CH2Cl2); IR (KBr) 3210, 1644, 1615 cm–1; H NMR δ 6.95 (s, 1H), 7.25 (t, J = 7.4 Hz, 1H),
7.41–7.50 (m, 5H), 7.87 (dd, J = 7.4, 1.7 Hz, 1H), 7.94 (br, 1H), 8.13 (d, J = 8.6 Hz, 1H). Anal. Calcd for
C15H10Cl3NO: C, 55.16; H, 3.09; N, 4.29. Found: C, 55.13; H, 3.21; N, 4.07.
4-(Chloromethylidene)-2-(2-chlorophenyl)-3,1-benzoxazine (1d): yield: 67%; a white solid; mp 93–95
1
˚C (hexane/CH2Cl2); IR (KBr) 3107, 1645, 1618 cm–1; H NMR δ 5.98 (s, 1H), 7.26 (t, J = 7.6 Hz, 1H),
7.36–7.44 (m, 5H), 7.50 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 7.4 Hz, 1H); 13C NMR δ 92.88, 119.31, 121.11,
126.74, 127.07, 128.46, 130.84, 130.94, 130.99, 131.21, 131.87, 133.41, 137.61, 146.17, 153.89. HR-MS
(DART). Calcd for C15H10Cl2NO (M+H): 290.0134. Found: m/z 290.0132.
4-Chloro-N-[2-(2,2-dichloroethenyl)phenyl]benzamide: yield: 89%; a white solid; mp 143–145 ˚C
(hexane/CH2Cl2); IR (KBr) 3267, 1655, 1616 cm–1; 1H NMR δ 6.88 (s, 1H), 7.24 (dd, J = 8.0, 7.4 Hz, 1H),
7.42 (dd, J = 8.0, 7.4 Hz, 1H), 7.44 (d, J = 8.0 Hz, 1H), 7.50 (d, J = 8.6 Hz, 2H), 7.68 (br s, 1H), 7.82 (d,
J = 8.6 Hz, 2H), 8.04 (d, J = 8.0 Hz, 1H). Anal. Calcd for C15H10Cl3NO: C, 55.16; H, 3.09; N, 4.29.
Found: C, 55.14; H, 3.38; N, 4.07.

4-(Chloromethylidene)-2-(4-chlorophenyl)-3,1-benzoxazine (1e): yield: 64%; a yellow solid; mp
1
162–165 ˚C (hexane/CH2Cl2); IR (KBr) 3104, 1644, 1613 cm–1; H NMR δ 5.97 (s, 1H), 7.24 (ddd, J =
13
8.6, 8.0, 1.7 Hz, 1H), 7.35–7.41 (m, 3H), 7.46 (d, J = 9.2 Hz, 2H), 8.19 (d, J = 9.2 Hz, 2H); C NMR δ
92.73, 119.30, 121.14, 126.91, 127.94, 128.74, 129.26, 129.30, 131.00, 137.91, 138.22, 146.01, 153.03.
HR-MS (EI). Calcd for C15H9Cl2NO (M): 289.0061. Found: m/z 289.0061.
2,4-Dichloro-N-[2-(2,2-dichloroethenyl)phenyl]benzamide: yield: 89%; a white solid; mp 127–129 ˚C
1
(hexane/CH2Cl2); IR (KBr) 3173, 1654 cm–1; H NMR δ 6.92 (s, 1H), 7.25 (dd, J = 8.0, 7.4 Hz, 1H),
7.40–7.47 (m, 3H), 7.51 (d, J = 1.7 Hz, 1H), 7.84 (d, J = 8.0 Hz, 1H), 7.95 (br s, 1H), 8.10 (d, J = 8.0 Hz,
1H). Anal. Calcd for C15H9Cl4NO: C, 49.90; H, 2.51; N, 3.88. Found: C, 49.90; H, 2.84; N, 3.81.
4-(Chloromethylidene)-2-(2,4-dichlorophenyl)-3,1-benzoxazine (1f): yield: 64%; a white solid; mp
1
154–156 ˚C (hexane/CH2Cl2); IR (KBr) 3116, 1635, 1618 cm–1; H NMR δ 5.97 (s, 1H), 7.26 (ddd, J =
13
8.0, 7.4, 1.7 Hz, 1H), 7.34–7.40 (m, 4H), 7.52 (d, J =1.7 Hz, 1H), 7.87 (d, J = 8.6 Hz, 1H); C NMR δ
93.07, 119.32, 121.14, 127.13 (two overlapped Cs), 128.62, 129.19, 130.91, 131.04, 132.17, 134.47,
137.45, 137.49, 146.10, 152.93. Anal. Calcd for C15H8Cl3NO: C, 55.51; H, 2.48; N, 4.32. Found: C,
55.31; H, 2.74; N, 4.26.
N-[2-(2,2-Dichloroethenyl)phenyl]-3-methoxybenzamide: yield: 94%; a white solid; mp 112–114 ˚C
1
(hexane/CH2Cl2); IR (KBr) 3241, 1635, 1621 cm–1; H NMR δ 3.90 (s, 3H), 6.90 (s, 1H), 7.11–7.14 (m,
1H), 7.23 (td, J = 7.4, 1.1 Hz, 1H), 7.39–7.47 (m, 5H), 7.74 (br, 1H), 8.10 (d, J = 8.0 Hz, 1H). HR-MS
(EI). Calcd for C16H13Cl2NO2 (M): 321.0323. Found: m/z 321.0318.
4-(Chloromethylidene)-2-(3-methoxyphenyl)-3,1-benzoxazine (1g): yield: 85%; a pale-yellow solid;
mp 108–110 ˚C (hexane/CH2Cl2); IR (KBr) 3108, 1637, 1615 cm–1; 1H NMR δ 3.91 (s, 3H), 5.95 (s, 1H),
7.09 (dd, J = 8.0, 1.7 Hz, 1H), 7.19–7.22 (m, 1H), 7.34–7.40 (m, 4H), 7.79 (d, J = 1.1 Hz, 1H), 7.85 (dd, J
13
= 8.0, 1.1 Hz, 1H); C NMR δ 55.37, 92.50, 112.36, 118.51, 119.37, 120.49, 121.11, 126.90, 127.79,
129.46, 130.92, 132.14, 138.10, 146.12, 153.78, 159.53. Anal. Calcd for C16H12ClNO2: C, 67.26; H, 4.23;
N, 4.90. Found: C, 67.32; H, 4.09; N, 4.66.
N-[2-(2,2-Dichloroethenyl)phenyl]pyridine-3-carboxamide: yield: 87%; a yellow oil; Rf 0.36
1
(AcOEt/hexane 5:1); IR (neat) 3263, 1652 cm–1; H NMR δ 6.90 (s, 1H), 7.26 (t, J = 7.4 Hz, 1H),
7.41–7.50 (m, 3H), 7.78 (br s, 1H), 8.04 (d, J = 7.4 Hz, 1H), 8.22 (d, J = 8.0 Hz, 1H), 8.81 (dd, J = 4.6,
1.1 Hz, 1H), 9.10 (s, 1H). HR-MS (EI). Calcd for C14H10Cl2N2O (M): 292.0170. Found: m/z 292.0160.
4-(Chloromethylidene)-2-(pyridin-3-yl)-3,1-benzoxazine (1i): yield: 56%; a white solid; mp 104–106
˚C (hexane/CH2Cl2); IR (KBr) 3087, 1640, 1616 cm–1; 1H NMR δ 5.99 (s, 1H), 7.24 (td, J = 6.9, 1.7 Hz,
13
1H), 7.27–7.43 (m, 4H), 8.48 (ddd, J = 8.0, 2.3, 1.7 Hz, 1H), 8.76 (d, J = 3.4 Hz, 1H), 9.45 (s, 1H); C
NMR δ 93.19, 119.50, 121.91, 123.21, 126.90, 127.09, 128.30, 131.06, 135.17, 137.61, 145.84, 149.43,

152.22, 152.39. Anal. Calcd for C14H9ClN2O: C, 65.51; H, 3.53; N, 10.91. Found: C, 65.45; H, 3.46; N,
10.83.
4-Chloro-N-[4-chloro-2-(2,2-dichloroethenyl)phenyl]benzamide: yield: 74%; a white solid; mp
1
153–154 ˚C (hexane/CH2Cl2); IR (KBr) 3271, 1652 cm–1; H NMR δ 6.82 (s, 1H), 7.38 (dd, J = 8.6, 2.3
Hz, 1H), 7.43 (d, J = 2.3 Hz, 1H), 7.50 (d, J = 8.6 Hz, 2H), 7.63 (br s, 1H), 7.80 (d, J = 8.6 Hz, 2H), 8.03
(d, J = 8.6 Hz, 1H). Anal. Calcd for C15H9Cl4NO: C, 49.90; H, 2.51; N, 3.88. Found: C, 49.67; H, 2.76; N,
3.79.
6-Chloro-4-(chloromethylidene)-2-(4-chlorophenyl)-3,1-benzoxazine (1j). This compound was
isolated by filtration and washing with water after addition of saturated aqueous NH4Cl to the reaction
mixture in 85% yield; a white solid; mp 223–225 ˚C (THF); IR (KBr) 3119, 1645, 1617 cm–1. This
compound was of quite insolubility in most organic solvents. HR-MS (EI). Calcd for C15H8Cl3NO (M):
322.9671. Found: m/z 322.9687.
N-[2-(2,2-Dichloroethenyl)phenyl-4-methoxy]benzamide: yield: 86%; a white solid; mp 131–133 ˚C
1
(hexane/ CH2Cl2); IR (KBr) 3335, 1645, 1616 cm–1; H NMR δ 3.83 (s, 3H), 6.88 (s, 1H), 6.95 (dd, J =
8.6, 2.9 Hz, 1H), 7.04 (d, J = 2.9 Hz, 1H), 7.51 (t, J = 7.4 Hz, 2H), 7.58 (t, J = 7.4 Hz, 1H), 7.59 (br s,
1H), 7.80 (d, J = 8.6 Hz, 1H), 7.87 (d, J = 7.4 Hz, 2H). HR-MS (EI). Calcd for C16H13Cl2NO2 (M):
321.0323. Found: m/z 321.0318.
4-(Chloromethylidene)-6-methoxy-2-phenyl-3,1-benzoxazine (1k): yield: 99%; a white solid; mp
92–94 ˚C (hexane/ CH2Cl2); IR (KBr) 3110, 1642, 1613 cm–1; 1H NMR δ 3.83 (s, 3H), 5.93 (s, 1H), 6.82
(d, J = 2.9 Hz, 1H), 6.94 (dd, J = 8.6, 2.9 Hz, 1H), 7.32 (d, J = 8.6 Hz, 1H), 7.46–7.52 (m, 3H), 8.23 (dd,
13
J = 7.4, 1.7 Hz, 2H); C NMR δ 55.59, 92.44, 105.30, 117.22, 120.11, 127.68, 128.31, 128.41, 131.03,
131.60, 131.99, 146.20, 152.26, 158.93. Anal. Calcd for C16H12ClNO2: C, 67.26; H, 4.23; N, 4.90. Found:
C, 66.99; H, 4.29; N, 4.83.
Typical Procedure for the Preparation of N-[2-(2-Chloroacetyl)phenyl]benzamides (2).
N-[2-(2-Chloroacetyl)phenyl]benzamide (2a). A solution of 1a (1.1 g, 4.4 mmol) in THF (12 mL)
containing 10% aqueous HCl (1.5 mL) was stirred at rt for 5.5 h. Saturated aqueous NaHCO3 (30 mL)
was added and the mixture was extracted with AcOEt (3 × 25 mL). The combined extracts were washed
with brine (30 mL), dried (Na2SO4), and concentrated by evaporation. The residual solid was
recrystallized from hexane/CH2Cl2 to give 2a (1.1 g, 94%); a white solid; mp 136–138 ˚C; IR (KBr) 3240,
1674, 1661, 1611 cm–1; 1H NMR δ 4.85 (s, 2H), 7.20 (ddd, J = 8.0, 7.4, 1.1 Hz, 1H), 7.53–7.59 (m, 3H),
7.69 (ddd, J = 8.5, 7.4, 1.1 Hz, 1H), 7.90 (dd, J = 8.0, 1.1 Hz, 1H), 8.07 (dd, J = 8.0, 1.1 Hz, 2H), 9.03 (d,
J = 8.5 Hz, 1H), 12.33 (s, 1H). Anal. Calcd for C15H12ClNO2: C, 65.82; H, 4.42; N, 5.12. Found: C, 65.70;
H, 4.64; N, 4.96.

N-[2-(2-Chloroacetyl)phenyl]-3-methylbenzamide (2b): a pale-yellow solid; mp 138–140 ˚C
(hexane/CH2Cl2); IR (KBr) 3238, 1671, 1657, 1605 cm–1; 1H NMR δ 2.47 (s, 3H), 4.82 (s, 2H), 7.19 (dd,
J = 8.0, 7.4 Hz, 1H), 7.39 (t, J = 7.4 Hz, 1H), 7.42 (t, J = 7.4 Hz, 1H), 7.68 (t, J = 8.0 Hz, 1H), 7.85–7.90
(m, 3H), 9.02 (d, J = 8.6 Hz, 1H), 12.26 (br s, 1H). HR-MS (EI). Calcd for C16H14ClNO2 (M): 287.0713.
Found: m/z 287.0724.
N-[2-(2-Chloroacetyl)phenyl]-4-methylbenzamide (2c):
a
white solid; mp 136–138 ˚C
(hexane/CH2Cl2); IR (KBr) 3275, 1673, 1660, 1612 cm–1; 1H NMR δ 2.44 (s, 3H), 4.83 (s, 2H), 7.18 (dd,
J = 8.0, 7.4 Hz, 1H), 7.33 (d, J = 8.0 Hz, 2H), 7.67 (dd, J = 8.0, 7.4 Hz, 1H), 7.89 (dd, J = 8.0, 1.1 Hz,
1H), 7.99 (d, J = 8.0 Hz, 2H), 9.03 (d, J = 8.0 Hz, 1H), 12.28 (br s, 1H). Anal. Calcd for C16H14ClNO2: C,
66.79; H, 4.90; N, 4.87. Found: C, 66.93; H, 5.30; N, 4.56.
2-Chloro-N-[2-(2-chloroacetyl)phenyl]benzamide (2d): a pale-yellow solid; mp 102–105 ˚C
(hexane/CH2Cl2); IR (KBr) 3238, 1689, 1664 cm–1; 1H NMR δ 4.81 (s, 2H), 7.22 (ddd, J = 8.0, 7.4, 1.1 Hz,
1H), 7.38 (td, J = 7.4, 1.1 Hz, 1H), 7.43 (td, J = 7.4, 1.7 Hz, 1H), 7.48 (dd, J = 8.0, 1.1 Hz, 1H), 7.65 (dd,
J = 7.4, 1.7 Hz, 1H), 7.69 (ddd, J = 8.6, 7.4, 1.7 Hz, 1H), 7.87 (dd, J = 8.0, 1.1 Hz, 1H), 8.98 (d, J = 8.6
Hz, 1H), 11.81 (br s, 1H). HR-MS (EI). Calcd for C15H11Cl2NO2 (M): 307.0167. Found: m/z 307.0170.
4-Chloro-N-[2-(2-chloroacetyl)phenyl]benzamide (2e): a pale-yellow solid; mp 135–138 ˚C
(hexane/CH2Cl2); IR (KBr) 3242, 1671, 1663, 1610 cm–1; 1H NMR δ 4.85 (s, 2H), 7.20 (ddd, J = 8.0, 7.4,
1.1 Hz, 1H), 7.50 (d, J = 8.6 Hz, 2H), 7.68 (ddd, J = 8.0, 7.4, 1.1 Hz, 1H), 7.89 (dd, J = 8.0, 1.1 Hz, 1H),
8.01 (d, J = 8.6 Hz, 2H), 8.99 (d, J = 8.0 Hz, 1H), 12.34 (s, 1H). Anal. Calcd for C15H11Cl2NO2: C, 58.47;
H, 3.60; N, 4.55. Found: C, 58.31; H, 3.64; N, 4.22.
2,4-Dichloro-N-[2-(2-chloroacetyl)phenyl]benzamide (2f):
a
white solid; mp 150–152 ˚C
1
(hexane/CH2Cl2); IR (KBr) 3240, 1687, 1666, 1607 cm–1; H NMR δ 4.79 (s, 2H), 7.23 (dd, J = 8.0, 7.4
Hz, 1H), 7.37 (dd, J = 8.6, 1.1 Hz, 1H), 7.51 (d, J = 1.1 Hz, 1H), 7.61 (d, J = 8.0 Hz, 1H), 7.70 (dd, J =
8.0, 7.4 Hz, 1H), 7.88 (d, J = 8.0 Hz, 1H), 8.94 (d, J = 8.6 Hz, 1H), 11.8 (br s, 1H). HR-MS (EI). Calcd
for C15H10Cl3NO2 (M): 340.9777. Found: m/z 340.9769.
N-[2-(2-Chloroacetyl)phenyl]-3-methoxybenzamide (2g):
a
white solid; mp 154–156 ˚C
(hexane/CH2Cl2); IR (KBr) 3270, 1673, 1662, 1605 cm–1; 1H NMR δ 3.90 (s, 3H), 4.83 (s, 2H), 7.12 (dd,
J = 8.0, 2.9 Hz, 1H), 7.18 (ddd, J = 8.0, 7.6, 1.1 Hz, 1H), 7.44 (dd, J = 8.0, 7.4 Hz, 1H), 7.60 (d, J = 2.3
Hz, 1H), 7.63 (d, J = 7.4 Hz, 1H), 7.69 (td, J = 7.4, 1.1 Hz, 1H), 7.88 (d, J = 7.4 Hz, 1H), 8.90 (d, J = 8.0
Hz, 1H), 12.31 (s, 1H). Anal. Calcd for C16H14ClNO3: C, 63.27; H, 4.65; N, 4.61. Found: C, 63.32; H,
4.42; N, 4.45.
N-[2-(2-Chloroacetyl)phenyl]thiophene-2-carboxamide (2h): a white solid; mp 124–126 ˚C
(hexane/CH2Cl2); IR (KBr) 3235, 1655, 1608 cm–1; 1H NMR δ 4.85 (s, 2H), 7.15–7.18 (m, 2H), 7.60 (dd,

J = 4.6, 1.1 Hz, 1H), 7.65 (td, J = 7.4, 1.1 Hz, 1H), 7.85–7.88 (m, 2H), 8.91 (dd, J = 7.4, 1.1 Hz, 1H),
12.34 (br s, 1H). HR-MS (DART). Calcd for C13H11ClNO2S (M+H): 280.0199. Found: m/z 280.0193.
N-[2-(2-Chloroacetyl)phenyl]pyridine-3-carboxamide (2i): a white solid; mp 145 ˚C (decomp.)
(hexane/CH2Cl2); IR (KBr) 3239, 1698, 1663, 1611 cm–1; 1H NMR δ 4.84 (s, 2H), 7.24 (ddd, J = 8.0, 7.4,
1.1 Hz, 1H), 7.49 (dd, J = 8.6, 4.6 Hz, 1H), 7.71 (ddd, J = 8.0, 7.4, 1.1 Hz, 1H), 7.92 (dd, J = 8.0, 1.1 Hz,
1H), 8.34 (ddd, J = 8.0, 2.3, 1.7 Hz, 1H), 8.82 (dd, J = 4.6, 1.7 Hz, 1H), 9.00 (d, J = 8.6 Hz, 1H), 9.32 (d,
J = 2.3 Hz, 1H), 12.43 (br s, 1H). Anal. Calcd for C14H11ClN2O2: C, 61.21; H, 4.04; N, 10.20. Found: C,
60.96; H, 4.02; N, 10.11.
4-Chloro-N-[4-chloro-2-(2-chloroacetyl)phenyl]benzamide (2j): colorless needles; mp 166–168 ˚C
(hexane/CH2Cl2); IR (KBr) 3245, 1669, 1605 cm–1; 1H NMR δ 4.80 (s, 2H), 7.51 (d, J = 8.6 Hz, 2H), 7.64
(dd, J = 9.2, 2.9 Hz, 1H), 7.85 (d, J = 2.9 Hz, 1H), 7.99 (d, J = 8.6 Hz, 2H), 8.99 (d, J = 9.2 Hz, 1H),
12.22 (br s, 1H). Anal. Calcd for C15H10Cl3NO2: C, 52.59; H, 2.94; N, 4.09. Found: C, 52.44; H, 3.07; N,
3.87.
N-[2-(2-Chloroacetyl)-4-methoxyphenyl]benzamide (2k):
a
white solid; mp 148–150 ˚C
(hexane/CH2Cl2); IR (KBr) 3289, 1662, 1617, 1601 cm–1; 1H NMR δ 3.88 (s, 3H), 4.80 (s, 2H), 7.25–7.28
(m, 2H), 7.35 (d, J = 2.9 Hz, 1H), 7.51–7.58 (m, 3H), 8.05 (d, J = 9.2 Hz, 2H), 12.00 (br s, 1H). Anal.
Calcd for C16H14ClNO3: C, 63.27; H, 4.65; N, 4.61. Found: C, 63.26; H, 4.66; N, 4.50.
Typical Procedure for the Preparation of 1-Aroyl-1,2-dihydro-3H-indol-3-ones (4). 1-Benzoyl-1,2-
dihydro-3H-indol-3-one (4a).3 To a stirred solution of 2a (0.22 g, 0.80 mmol) in DMF (3 mL) containing
(Boc)2O (0.17 g, 0.8 mmol) at rt was added Et3N (0.16 g, 1.6 mmol). After stirring overnight at the same
temperature, saturated aqueous NaHCO3 (15 mL) was added and the mixture was extracted with AcOEt
(3 × 10 mL). The combined extracts were washed with H2O (3 × 10 mL) and brine (10 mL), dried
(Na2SO4), and concentrated by evaporation to give a residue containing 3a. To this residue was added
TFA (0.5 mL) at rt and the solution was stirred for 1 h. The solution was diluted with anhydrous CH2Cl2
(15 mL) and anhydrous K2CO3 (1 g) was added. After stirring for 30 min, the solid materials were filtered
off under reduced pressure and the filtrate was concentrated by evaporation. The residue was purified by
column chromatography on SiO2 (AcOEt/hexane 1:3) to afford 4a (0.12 g, 63 %); a pale-yellow solid; mp
1
122–124 ˚C (hexane/CH2Cl2) (lit.,3 124–125 ˚C). The spectral data (IR and H NMR) for this product
were identical to those reported previously.3
1-Benzoyl-1H-indol-3-yl 1,1-Dimethylethyl Carbonate (3a). This compound could be isolated by
column chromatography on SiO2 (CH2Cl2/hexane 1:5). A pale-yellow solid; mp 116–118 ˚C
(hexane/CH2Cl2); IR (KBr) 1763, 1688, 1602 cm–1; 1H NMR δ 1.57 (s, 9H), 7.35 (ddd, J = 8.0, 7.4, 1.1 Hz,
1H), 7.42 (td, J = 7.4, 1.1 Hz, 1H), 7.49 (s, 1H), 7.53 (t, J = 7.4 Hz, 2H), 7.55–7.62 (m, 2H), 7.75 (dd, J =
13
7.4, 1.1 Hz, 2H), 8.41 (d, J = 8.0 Hz, 1H); C NMR δ 27.62, 84.13, 115.12, 116.52, 117.76, 123.95,

124.00, 125.94, 128.65, 129.10, 131.93, 133.59, 134.26, 134.85, 150.50, 168.58. HR-MS (ESI). Calcd for
C20H20NO4 (M+H): 338.1392. Found: m/z 338.1389.
1-(3-Methylbenzoyl)-1,2-dihydro-3H-indol-3-one (4b):
a
pale-yellow solid; mp 76–77 ˚C
1
(hexane/CH2Cl2); IR (KBr) 1721, 1667 cm–1; H NMR δ 2.32 (s, 3H), 4.18 (s, 2H), 7.14 (t, J = 7.4 Hz,
13
1H), 7.23–7.29 (m, 4H), 7.56 (br t, J = 7.4 Hz, 1H), 7.67 (d, J = 7.4 Hz, 1H), 8.15 (br, 1H); C NMR δ
21.35, 57.83, 118.67, 123.78, 124.02, 124.48, 125.32, 127.60, 128.69, 131.79, 135.69, 136.98, 138.84,
153.79, 168.88, 195.26. HR-MS (EI). Calcd for C16H13NO2 (M): 251.0946. Found: m/z 251.0954. Anal.
Calcd for C16H13NO2: C, 76.48; H, 5.21; N, 5.57. Found: C, 76.77; H, 5.40; N, 5.70.
1-(4-Methylbenzoyl)-1,2-dihydro-3H-indol-3-one (4c): a pale-yellow solid; mp 133–135 ˚C
(hexane/CH2Cl2); IR (KBr) 1718, 1663, 1607 cm–1; 1H NMR δ 2.44 (s, 3H), 4.29 (s, 2H), 7.24 (t, J = 7.4
Hz, 1H), 7.29 (d, J = 8.0 Hz, 2H), 7.48 (d, J = 8.0 Hz, 2H), 7.65 (t, J = 7.4 Hz, 1H), 7.77 (d, J = 7.4 Hz,
13
1H), 8.22 (br, 1H); C NMR δ 21.52, 57.89, 118.71, 123.76, 124.39, 125.33, 127.27, 129.43, 132.84,
136.91, 141.60, 153.95, 168.82, 195.28. HR-MS (EI). Calcd for C16H13NO2 (M): 251.0946. Found: m/z
251.0939. Anal. Calcd for C16H13NO2: C, 76.48; H, 5.21; N, 5.57. Found: C, 76.24; H, 5.15; N, 5.48.
1-(2-Chlorobenzoyl)-1,2-dihydro-3H-indol-3-one (4d): a white solid; mp 140–142 ˚C (hexane/CH2Cl2);
1
IR (KBr) 1718, 1662 cm–1; H NMR δ 4.07 (br s, 2H), 7.32 (t, J = 7.4 Hz, 1H), 7.40–7.53 (m, 4H),
13
7.74–7.80 (m, 2H), 8.71 (d, J = 8.6 Hz, 1H); C NMR δ 56.35, 118.88, 123.79, 125.07, 125.32, 127.45,
127.59, 129.71, 130.03, 131.27, 135.75, 137.31, 152.96, 165.47, 194.54. HR-MS (EI). Calcd for
C15H10ClNO2 (M): 271.0400. Found: m/z 271.0412. Anal. Calcd for C15H10ClNO2: C, 66.31; H, 3.71; N,
5.16. Found: C, 66.24; H, 3.66; N, 5.13.
1-(4-Chlorobenzoyl)-1,2-dihydro-3H-indol-3-one (4e): a white solid; mp 111–114 ˚C (hexane/CH2Cl2);
1
IR (KBr) 1717, 1646 cm–1; H NMR δ 4.27 (s, 2H), 7.27 (dd, J = 8.0, 7.4 Hz, 1H), 7.49 (d, J = 8.6 Hz,
2H), 7.54 (d, J = 8.6 Hz, 2H), 7.68 (t, J = 7.4 Hz, 1H), 7.78 (d, J = 8.0 Hz, 1H), 8.28 (br, 1H); 13C NMR δ
57.65, 118.40, 123.85, 124.75, 125.32, 128.64, 129.17, 133.97, 137.02, 137.35, 153.51, 167.50, 194.73.
HR-MS (EI). Calcd for C15H10ClNO2 (M): 271.0400. Found: m/z 271.0404. Anal. Calcd for C15H10ClNO2:
C, 66.31; H, 3.71; N, 5.16. Found: C, 66.11; H, 3.79; N, 5.00.
1-(2,4-Dichlorobenzoyl)-1,2-dihydro-3H-indol-3-one (4f): a pale-yellow solid; mp 178–180 ˚C
(hexane/CH2Cl2); IR (KBr) 1724, 1659 cm–1; 1H NMR δ 4.06 (s, 2H), 7.33 (t, J = 7.4 Hz, 1H), 7.36–7.42
(m, 3H), 7.74–7.80 (m, 2H), 8.68 (d, J = 8.0 Hz, 1H); 13C NMR δ 56.23, 118.93, 120.37, 120.92, 123.87,
125.30, 128.09, 128.49, 130.05, 134.25, 136.82, 137.36, 152.86, 164.54, 194.14. HR-MS (EI). Calcd for
C15H9Cl2NO2 (M): 305.0010. Found: m/z 305.0021. Anal. Calcd for C15H9Cl2NO2: C, 58.85; H, 2.96; N,
4.58. Found: C, 58.62; H, 3.09; N, 4.55.

1-(3-Methoxybenzoyl)-1,2-dihydro-3H-indol-3-one (4g): a pale-yellow oil: Rf 0.38 (AcOEt/hexane 1:2);
IR (neat) 1722, 1666, 1602 cm–1; 1H NMR δ 3.85 (s, 3H), 4.29 (s, 2H), 7.06–7.09 (m, 2H), 7.13 (dd, J =
7.4, 1.1 Hz, 1H), 7.26 (t, J = 7.4 Hz, 1H), 7.41 (t, J = 8.0 Hz, 1H), 7.67 (br, 1H), 7.78 (d, J = 7.4 Hz, 1H),
13
8.30 (br, 1H); C NMR δ 55.41, 60.37, 112.28, 116.86, 118.72, 118.99, 123.77, 124.56, 125.35, 130.01,
136.91, 136.97, 153.63, 159.75, 168.37, 195.07. HR-MS (DART). Calcd for C16H14NO3 (M+H): 268.0973.
Found: m/z 268.0961. Anal. Calcd for C16H13NO3: C, 71.90; H, 4.90; N, 5.24. Found: C, 71.87; H, 5.07; N,
5.14.
1-(Thiophen-2-ylcarbonyl)-1,2-dihydro-3H-indol-3-one (4h): a white solid; mp 116–118 ˚C
(hexane/CH2Cl2); IR (KBr) 1724, 1623, 1604 cm–1; 1H NMR δ 4.63 (s, 2H), 7.18 (dd, J = 4.6, 4.0 Hz, 1H),
7.27 (dd, J = 8.0, 6.9 Hz, 1H), 7.64 (d, J = 4.6 Hz, 1H), 7.69–7.72 (m, 2H), 7.79 (d, J = 7.4 Hz, 1H), 8.58
13
(d, J = 8.6 Hz, 1H); C NMR δ 57.42, 119.46, 123.71, 124.74, 124.92, 127.76, 131.34, 131.76, 137.26,
137.65, 154.34, 160.83, 195.02. HR-MS (DART). Calcd for C13H10NO2S (M+H): 244.0432. Found: m/z
244.0420. Anal. Calcd for C13H9NO2S: C, 64.18; H, 3.73; N, 5.76. Found: C, 63.92; H, 3.67; N, 5.55.
1-(Pyridin-3-ylcarbonyl)-1,2-dihydro-3H-indol-3-one (4i): a beige solid; mp 132 ˚C (decomp)
1
(hexane/CH2Cl2); IR (KBr) 1722, 1674, 1602 cm–1; H NMR δ 4.31 (s, 2H), 7.34 (t, J = 7.4 Hz, 1H),
13
7.74–7.82 (m, 3H), 8.27 (d, J = 7.4 Hz, 1H), 8.89 (br s, 1H), 9.05 (br s, 1H), 9.25 (br, 1H); C NMR δ
57.29, 118.81, 124.11, 125.42, 125.51, 125.65, 133.50, 137.33, 138.88, 144.69, 147.95, 152.92, 164.01,
193.72. HR-MS (EI). Calcd for C14H10N2O2 (M): 238.0742. Found: m/z 238.0748. Anal. Calcd for
C14H10N2O2: C, 70.58; H, 4.23; N, 11.76. Found: C, 70.58; H, 4.36; N, 11.71.
5-Chloro-1-(4-chlorobenzoyl)-1,2-dihydro-3H-indol-3-one (4j): a white solid; mp 132–134 ˚C
(hexane/CH2Cl2); IR (KBr) 1726, 1668 cm–1; 1H NMR δ 4.29 (s, 2H), 7.49 (d, J = 8.6 Hz, 2H), 7.53 (d, J
= 8.6 Hz, 2H), 7.63 (dd, J = 7.4, 1.7 Hz, 1H), 7.73 (d, J = 1.7 Hz, 1H), 8.25 (br, 1H); 13C NMR δ 58.05,
120.06, 123.38, 126.61, 128.66, 129.27, 130.60, 133.59, 136.82, 137.66, 151.98, 167.45, 193.38. HR-MS
(EI). Calcd for C15H9Cl2NO2 (M): 305.0010. Found: m/z 305.0017. Anal. Calcd for C15H9Cl2NO2: C,
58.85; H, 2.96; N, 4.58. Found: C, 58.81; H, 3.01; N, 4.29.
1-Benzoyl-5-methoxy-1,2-dihydro-3H-indol-3-one (4k). To a stirred suspension of NaH (60% in
mineral oil; 14 mg, 0.36 mmol) in DME (5 mL) at 0 ˚C was added a solution of 2k (0.10 g, 0.33 mmol) in
DME (3 mL) dropwise. After 5 min, saturated aqueous NH4Cl (20 mL) was added and the mixture was
extracted with AcOEt (3 × 10 mL). The combined extracts were washed with water (3 × 15 mL) and brine
(15 mL), dried (Na2SO4), and concentrated by evaporation. The residue was purified by column
chromatography on SiO2 (AcOEt/hexane 1:3) to afford 4k (31 mg, 35%); a pale-yellow solid; mp
167–169 ˚C (hexane/CH2Cl2); IR (KBr) 1718, 1650 cm–1; 1H NMR δ 3.85 (s, 3H), 4.28 (s, 2H), 7.17 (d, J
= 2.3 Hz, 1H), 7.27 (br, 1H), 7.47–7.53 (m, 3H), 7.56 (dd, J = 8.0, 1.1 Hz, 2H), 8.30 (br, 1H); 13C NMR δ

55.77, 104.42, 119.90, 125.88, 126.22, 127.05, 128.79, 130.93, 135.80, 148.55, 156.84 (2 overlapped Cs),
168.10, 194.94. HR-MS (EI). Calcd for C16H13NO3 (M): 267.0895. Found: m/z 267.0885. Anal. Calcd for
C16H13NO3: C, 71.90; H, 4.90; N, 5.24. Found: C, 71.73; H, 4.84; N, 5.18.
ACKNOWLEDGEMENTS
We thank Mrs. Miyuki Tanmatsu of our university for her assistance in obtaining mass spectra and
elemental analytical data.
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