HETEROCYCLES

Paper | Regular issue | Vol. 92, No. 6, 2016, pp. 1063-1074
Received, 29th February, 2016, Accepted, 4th April, 2016, Published online, 8th April, 2016.

■ 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

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).

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.

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 uncorrected. IR spectra were recorded with a Perkin–Elmer Spectrum 65 FTIR spectrophotometer. 1H NMR and 13C 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; mp 97–99 ˚C (hexane/CH2Cl2); IR (KBr) 3121, 1639, 1613 cm–1; 1H 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 (hexane/CH2Cl2); IR (KBr) 3210, 1644, 1615 cm–1; 1H 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 ˚C (hexane/CH2Cl2); IR (KBr) 3107, 1645, 1618 cm–1; 1H 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 162–165 ˚C (hexane/CH2Cl2); IR (KBr) 3104, 1644, 1613 cm–1; 1H NMR δ 5.97 (s, 1H), 7.24 (ddd, J = 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); 13C 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 (hexane/CH2Cl2); IR (KBr) 3173, 1654 cm–1; 1H 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 154–156 ˚C (hexane/CH2Cl2); IR (KBr) 3116, 1635, 1618 cm–1; 1H NMR δ 5.97 (s, 1H), 7.26 (ddd, J = 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); 13C 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 (hexane/CH2Cl2); IR (KBr) 3241, 1635, 1621 cm–1; 1H 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 = 8.0, 1.1 Hz, 1H); 13C 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 (AcOEt/hexane 5:1); IR (neat) 3263, 1652 cm–1; 1H 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, 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); 13C 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 153–154 ˚C (hexane/CH2Cl2); IR (KBr) 3271, 1652 cm–1; 1H 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 (hexane/ CH2Cl2); IR (KBr) 3335, 1645, 1616 cm–1; 1H 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, J = 7.4, 1.7 Hz, 2H); 13C 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 (hexane/CH2Cl2); IR (KBr) 3240, 1687, 1666, 1607 cm–1; 1H 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 122–124 ˚C (hexane/CH2Cl2) (lit.,3 124–125 ˚C). The spectral data (IR and 1H 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 = 7.4, 1.1 Hz, 2H), 8.41 (d, J = 8.0 Hz, 1H); 13C 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 (hexane/CH2Cl2); IR (KBr) 1721, 1667 cm–1; 1H NMR δ 2.32 (s, 3H), 4.18 (s, 2H), 7.14 (t, J = 7.4 Hz, 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); 13C 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, 1H), 8.22 (br, 1H); 13C 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); IR (KBr) 1718, 1662 cm–1; 1H NMR δ 4.07 (br s, 2H), 7.32 (t, J = 7.4 Hz, 1H), 7.40–7.53 (m, 4H), 7.74–7.80 (m, 2H), 8.71 (d, J = 8.6 Hz, 1H); 13C 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); IR (KBr) 1717, 1646 cm–1; 1H 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), 8.30 (br, 1H); 13C 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 (d, J = 8.6 Hz, 1H); 13C 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) (hexane/CH2Cl2); IR (KBr) 1722, 1674, 1602 cm–1; 1H NMR δ 4.31 (s, 2H), 7.34 (t, J = 7.4 Hz, 1H), 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); 13C 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.

References

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