In(OTf)₃-catalyzed chemoselective alkylation of tryptamines with 2-oxo-1-pyrrolidine derivatives

Abstract

The chemoselective alkylation of tryptamine derivatives with 2-oxo-1-pyrrolidine compounds, catalyzed by In(OTf)₃, was investigated. A series of 2-alkyl and N-alkyl tryptamine derivatives were synthesized under mild conditions with good total yields (up to 99%) and chemoselectivity (up to 95 : 5).

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Introduction

The tryptamine skeleton widely exists in many natural products as well as in commercial drugs.¹ Selected alkaloids bearing a tryptamine skeleton are shown in Scheme 1. Serotonin (1) is a neurotransmitter which influences the human nervous system and plays a part in central nervous system function.² Melatonin (2), a neurohormone mainly secreted by the pineal gland, plays a pivotal role in regulating our body's circadian rhythms.³ Luzindole (3) is widely known as a reference MT2-selective melatonin receptor antagonist.⁴ Desformylflustrabromine (4) has been identified as the first selective allosteric modulator of nicotinic acetylcholine (nACh) receptors.⁵ Psychotrimine (5) and its analogous compounds often exhibit potent biological activity including anti-bacterial, anti-fungal, anti-viral and analgesic properties.⁶ Vinblastine (6), isolated from Catharanthus roseus at the end of the 1950s,⁷ is an efficient cancer chemotherapeutic agent in the therapy of particularly fast growing tumor types (leukemia, lymphoma).⁸

Scheme 1 Representative alkaloids.

Recently, we reported iodine-catalyzed alkylation of indoles with 1-(ethoxy-aryl-methyl)pyrrolidin-2-one to form 3-alkylated indole derivatives under mild conditions.⁹ As a continuation of this project, we attempted to utilize the tryptamine derivative 1a with 1-(ethoxy-aryl-methyl)pyrrolidin-2-one 2a (Scheme 2).

Scheme 2 Proposed attempt.

As expected, a 2-alkylized tryptamine derivative (3a) and an N-alkylized tryptamine derivative (4a) were obtained as the major and minor products, respectively.

In recent decades, numerous methods have been developed for the functionalization of tryptamine derivatives, such as the classical Fischer indolization, Larock's method,¹⁰ Friedel–Craft conjugate addition,¹¹ and nitroethylation of indole derivatives followed by reduction.¹² In addition, Nicolaou and coworkers have also covered a new synthetic approach from N-protected anilines to the functional tryptamines.¹³ It's still a challenge to functionalize the C-2 position of tryptamines directly; some methods referring to the synthesis of 2-benzyl tryptamines have reported limitations such as expensive catalysts, multiple steps, or harsh reaction conditions.¹⁴ Herein, we describe the chemoselective alkylation of tryptamines with 2-oxo-1-pyrrolidine derivatives, to give the desired C-2 alkylation of tryptamines bearing 2-oxo-1-pyrrolidine as the major products in good yields under mild conditions (Scheme 3).

Scheme 3 Routes to 2-substituted tryptamine compounds.

Results and discussion

Our studies were initiated by the model reaction of N-tosyl tryptamine 1a with 2a in CH₂Cl₂ at 40 °C. As shown in Table 1, the model reaction proceeded well, especially in the presence of 10 mol% In(OTf)₃ for 24 hours, which produced the 2-alkylized tryptamine derivative 3a in 63% LC-yield and the N-alkylized tryptamine derivative 4a in 5% LC-yield, respectively (Table 1, entry 1). A series of trifluoromethane sulfonates, other Lewis acids, as well as some Brønsted acids were screened for this reaction. It was found that In(OTf)₃ gave the best results based on the yields and chemoselectivity (Table 1, entries 2–13). Different solvents were employed for the further optimization of our reaction conditions (Table 2, entries 1–9). CH₂Cl₂, CHCl₃, toluene and DCE were found to be a little superior to the other solutions, and CH₂Cl₂ was the optimal solvent (Table 2, entry 1).

Table 1 Evaluation of catalysts^a

Entry	Cat. (10 mol%)	3a : 4a	Total yield^b (%)
a Reaction conditions: 1a (0.5 mmol), 2a (0.5 mmol), catalyst (0.05 mmol) in CH2Cl2 (2 mL) at 40 °C.b Determined by LC-MS (3a + 4a) analysis with biphenyl as the internal standard.
1	In(OTf)3	92 : 8	68
2	Zn(OTf)2	66 : 34	61
3	AgOTf	76 : 24	71
4	Yb(OTf)3	68 : 32	59
5	TfOH	>99 : 1	54
6	TFA	57 : 43	7
7	PTSA	82 : 18	62
8	FeCl3	70 : 30	58
9	InCl3·4H2O	48 : 52	40
10	NiCl2	—	Trace
11	CAN	77 : 23	53
12	I2	97 : 3	61
13	InCl3	38 : 62	37

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Table 2 Solution screening^a

Entry	Solvent	T (°C)	3a : 4a	Total yield^b (%)
a Reaction conditions: 1a (0.5 mmol), 2a (0.5 mmol), In(OTf)3 (0.05 mmol) in solution (2 mL), reflux.b Determined by LC-MS (3a + 4a) analysis with biphenyl as the internal standard.c DCE = 1,2-dichloroethane.
1	CH2Cl2	40	92 : 8	68
2	CHCl3	60	96 : 4	58
3	THF	60	67 : 33	27
4	Toluene	110	>99 : 1	50
5	CH3CN	60	94 : 6	49
6	DCE^c	90	>99 : 1	51
7	H2O	100	>99 : 1	18
8	EtOH	80	—	Trace
9	CH3NO2	110	—	Trace

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The reaction conditions were further optimized by screening the catalyst loading, reaction times and molar ratios of 1a and 2a (Tables 3 and 4). It was found that the optimized model reaction conditions were a 1 : 1.5 molar ratio of 1a and 2a in the presence of 15 mol% In(OTf)₃ in CH₂Cl₂ for 10 hours, which could furnish 3a in 74% LC-yield (73% isolated yield) and 4a in 14% LC-yield, respectively (Table 4, entry 2).

Table 3 Reaction optimization^a

Entry	In(OTf)3 (mol%)	t (h)	3a : 4a	Total yield^b (%)
a Reaction conditions: 1a (0.5 mmol), 2a (0.5 mmol), In(OTf)3 (0.05 mmol) in CH2Cl2 (2 mL), 40 °C.b Determined by LC-MS (3a + 4a) analysis with biphenyl as the internal standard.
1	10	24	92 : 8	68
2	15	4	54 : 46	61
3	15	6	75 : 25	80
4	15	10	88 : 12	82
5	15	12	87 : 13	83
6	15	24	87 : 13	83
7	15	48	83 : 17	82
8	20	24	84 : 16	82

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Table 4 Effect of the ratio^a

Entry	1a : 2a	3a : 4a	Total yield^b (%)
a Reaction conditions: 1a (0.5 mmol), 2a (X mmol), In(OTf)3 (0.075 mmol) in CH2Cl2 (2 mL), 40 °C.b Determined by LC-MS (3a + 4a) analysis with biphenyl as the internal standard.c Isolated yield of 3a + 4a.
1	1 : 1	88 : 12	82 (70 + 9^c)
2	1 : 1.5	84 : 16	88 (73 + 13^c)
3	1 : 2	74 : 26	89 (65 + 20^c)
4	1 : 2.5	65 : 35	66 (40 + 21^c)

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With the optimal reaction conditions in hand, we investigated the scope of the reaction utilizing a range of different 2-oxo-1-pyrrolidine derivatives and tryptamine derivatives. As shown in Table 5, all the reactions were completed with good generality. The substrates 2 bearing Ar with electron-donating groups, such as methyl and methoxy groups, could react well with N-tosyl tryptamine 1a to furnish the desired products in moderate yields with up to 95 : 5 chemoselectivity (Table 5, entries 1–5). The substrates 2 bearing Ar with strong electron-withdrawing groups, such as nitro and cyano groups, could proceed well to give the desired products in excellent yields with up to 85 : 15 chemoselectivity (Table 5, entries 11 and 12). Some other substrates 2 bearing aryls, such as naphthalene-2-yl and thiophen-2-yl, were demonstrated to be good candidates for this reaction, giving high yields (Table 5, entries 13 and 14). As shown in Table 5, the substrates 2 bearing Ar with the same group at different positions gave similar results, reflecting that the steric effect has little influence (Table 5, entries 1–5, 7–10). As shown in Table 5, 2-substituted tryptamines were formed in a higher ratio compared to N-substituted tryptamines due to the steric congestion caused during the attack from different positions of the indole to the bulky iminium ion. The absolute configurations of 3k and 4f have been determined by X-ray diffraction (Scheme 4).

Table 5 Substrate scope^a

Entry	Ar	R	3 : 4	Total yield^b (%)
a Reaction conditions: 1a (0.5 mmol), 2 (0.75 mmol), In(OTf)3 (0.075 mmol) in CH2Cl2 (2 mL), 40 °C.b Isolated yield (3 + 4).
1		Et	3b : 4b = 86 : 14	78
2		Et	3c : 4c = 78 : 22	77
3		Et	3d : 4d = 95 : 5	74
4		Et	3e : 4e = 82 : 18	77
5		Et	3f : 4f = 68 : 32	80
6		Et	3g : 4g = 79 : 21	76
7		Et	3h : 4h = 85 : 15	98
8		Et	3i : 4i = 82 : 18	85
9		Et	3j : 4j = 77 : 23	97
10		Et	3k : 4k = 88 : 12	86
11		Et	3l : 4l = 72 : 28	95
12		Et	3m : 4m = 85 : 15	99
13		Et	3n : 4n = 82 : 18	87
14		Et	3o : 4o = 86 : 14	85
15		Me(2p)	3h : 4h = 89 : 11	98
16		Me(2q)	3m : 4m = 89 : 11	99

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Scheme 4 X-ray crystal structure of 3k and 4f.

Furthermore, tryptamine derivatives with different protecting groups were also explored (Table 6). All the reactions proceeded well to furnish the desired C-2 alkylation and N-alkylation products in moderate to excellent yields with high chemoselectivities (86 : 14). Unfortunately, it was found that no desired product was formed when tryptamine was used in the reaction, under identical reaction conditions.

Table 6 Substrate scope^a

Entry	Tryptamine	3 : 4	Total yield^b (%)
a Reaction conditions: 1 (0.5 mmol), 2a (0.75 mmol), In(OTf)3 (0.075 mmol) in CH2Cl2 (2 mL), 40 °C.b Isolated yield (3 + 4).
1		3p : 4p = 57 : 43	53
2		3q : 4q = 75 : 25	87
3		3r : 4r = 86 : 14	97

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Based on the above results and ongoing efforts by our group,¹⁵ a plausible mechanism for this reaction is suggested in Scheme 5. The C–O bond of the 1-(ethoxy(4-nitrophenyl)methyl)pyrrolidin-2-one (2a) was activated in the presence of the Lewis acid to generate a stable intermediate of the iminium ion I and In(OTf)₃(OEt)⁻. Under these circumstances, I was readily attacked by the C-2 position of the tryptamine derivative 1a (path [A]). The intermediate of the imine cation II was formed, followed by the elimination of a proton to afford the final product 3a. For the nucleophilicity of the N atom, the product 4a could also be obtained through the elimination of a proton from the intermediate III (path [B]). The proton was captured by the ethoxide ion of the In(OTf)₃(OEt)⁻ to regenerate EtOH and In(OTf)₃. Because of the steric congestion caused during the attack from the different positions of the indole to the bulky iminium ion, 2-substituted tryptamines were formed in a higher ratio compared to N-substituted tryptamines.

Scheme 5 Plausible mechanism.

Conclusions

In conclusion, we have developed a simple and highly efficient indium-catalyzed method to introduce various benzyl groups, as well as the 2-oxo-1-pyrrolidine moiety at the C-2 position of tryptamine derivatives, with good yields and chemoselectivity. In addition, our studies could not only enrich the library of Luzindole (3), but also provide a new way to synthesize a wide variety of potential pharmaceutically active compounds bearing a 2-oxo-1-pyrrolidine scaffold.

Experimental

General

Unless otherwise stated, all reagents were purchased from commercial suppliers and used without further purification. All reactions were carried out in air and using undistilled solvents, without any precautions to exclude air and moisture unless otherwise noted. Reactions were monitored by thin-layer chromatography (TLC) on silica gel GF-254 precoated glass plates. Chromatograms were visualized by fluorescence quenching with UV light at 254 nm. Flash column chromatography was performed using silica gel. Melting points were measured on a melting point apparatus and uncorrected. ¹H and ¹³C NMR spectra were recorded in CDCl₃ or D₆-DMSO on 300 MHz or 400 MHz spectrometers. Tetramethylsilane (TMS) served as an internal standard for ¹H NMR, and CDCl₃ or D₆-DMSO were used as internal standards for ¹³C NMR. IR spectra were recorded on a FT-IR spectrometer. Mass spectra were carried out using a quadrupole LC/MS system with an ESI source. HRMS was recorded on a commercial apparatus (ESI source).

General procedure for the In-catalyzed alkylation reaction

N-Tosyl tryptamine (0.5 mmol, 0.1575 g), 1-(ethoxy(phenyl)methyl) pyrrolidin-2-one (0.75 mmol, 0.1643 g), In(OTf)₃ (0.075 mmol, 0.0421 g, 15 mol%), and CH₂Cl₂ (2 mL) were added into a flask. The mixture was then vigorously stirred at 40 °C until 1-phenylbutane-1,3-dione or 1-(ethoxy(phenyl)methyl)pyrrolidin-2-one was completely consumed, as monitored by TLC analysis. After the completion of the reaction, the residue was directly purified by flash column chromatography using ethyl acetate and petroleum ether as eluents to give the pure product.

4-Methyl-N-(2-(1-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4a). White solid (m.p. 70–71 °C), 14% yield (34.1 mg); ¹H NMR (400 MHz, DMSO-d₆) δ 7.66–7.61 (m, 3H), 7.57 (s, 1H), 7.48–7.40 (m, 4H), 7.35–7.27 (m, 3H), 7.19 (d, J = 7.1 Hz, 2H), 7.14 (t, J = 7.5 Hz, 1H), 7.07 (t, J = 7.4 Hz, 1H), 6.95 (s, 1H), 3.33–3.39 (m, 1H), 3.02–2.94 (m, 2H), 2.80–2.68 (m, 3H), 2.46–2.37 (m, 1H), 2.35 (s, 3H), 2.32–2.24 (m, 1H), 2.08–1.97 (m, 1H), 1.90–1.89 (m, 1H); ¹³C NMR (75 MHz, CDCl3) δ 175.63, 143.38, 137.00, 134.81, 129.65, 129.05, 128.78, 127.78, 126.95, 126.88, 124.72, 122.80, 120.38, 118.79, 111.79, 110.74, 63.72, 43.35, 43.08, 30.77, 25.67, 21.53, 18.00; IR (KBr) ν_max: 3174, 2916, 1653, 1597, 1492, 1452, 1428, 1319, 1291, 1152, 1095, 925, 811, 744, 706, 664, 567, 545, 511 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₉N₃NaO₃S: [M + Na]⁺ 510.1827, found: 510.1842%.

4-Methyl-N-(2-(2-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3a). White solid (85–86 °C), 74% yield (180.2 mg); ¹H NMR (400 MHz, DMSO-d₆) δ 10.70 (s, 1H), 7.62 (d, J = 8.2 Hz, 3H), 7.40–7.26 (m, 7H), 7.08–7.03 (m, 3H), 6.97 (t, J = 7.3 Hz, 1H), 6.56 (s, 1H), 3.46–3.40 (m, 1H), 3.02–3.10 (m, 1H), 2.90–2.73 (m, 4H), 2.43–2.36 (m, 1H), 2.34 (s, 3H), 2.30–2.20 (m, 1H), 2.06–1.97 (s, 1H), 1.94–1.85 (s, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.12, 142.07, 135.98, 135.67, 134.67, 131.59, 128.50, 127.81, 126.74, 126.14, 125.97, 125.72, 121.61, 118.76, 117.69, 110.33, 110.22, 50.89, 45.86, 42.26, 30.21, 23.58, 20.49, 17.25; IR (KBr) ν_max: 3356, 3198, 2935, 1645, 1598, 1496, 1458, 1443, 1300, 1145, 1095, 931, 913, 812, 751, 709, 673, 574, 541, 530 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₉N₃NaO₃S: [M + Na]⁺ 510.1827, found: 510.1823%.

N-(2-(1-((2-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4b). White solid (m.p. 30–31 °C), 11% yield (27.0 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.68 (s, 1H), 7.56 (d, J = 7.3 Hz, 2H), 7.44–7.35 (m, 2H), 7.30 (d, J = 7.8 Hz, 1H), 7.22–7.17 (m, 1H), 7.14 (d, J = 7.4 Hz, 2H), 7.10–7.03 (m, 2H), 7.02–6.93 (m, 2H), 6.65 (s, 1H), 4.55 (s, 1H), 3.69 (s, 3H), 3.42–3.33 (m, 1H), 3.26–3.11 (m, 2H), 2.90–2.80 (m, 1H), 2.80–2.71 (m, 1H), 2.70–2.62 (m, 1H), 2.52–2.41 (m, 2H), 2.37 (s, 3H), 2.11–2.01 (m, 1H), 1.99–1.88 (m, 1H); ¹³C NMR (100 MHz, CDCl₃) δ 175.63, 157.49, 143.45, 137.03, 136.53, 130.74, 129.81, 127.92, 127.19, 127.11, 124.23, 123.98, 122.70, 120.77, 120.12, 118.96, 111.37, 110.93, 110.62, 61.52, 55.90, 44.92, 43.09, 31.16, 25.66, 21.73, 18.51; IR (KBr) ν_max: 3282, 2923, 1673, 1492, 1461, 1287, 1156, 1094, 742, 545, 535, 506 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1915%.

N-(2-(2-((2-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3b). White solid (m.p. 218–219 °C), 67% yield (173.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 9.05 (s, 1H), 7.54 (d, J = 7.9 Hz, 2H), 7.37 (d, J = 7.8 Hz, 1H), 7.33–2.27 (m, 2H), 7.20–7.12 (m, 4H), 7.03 (t, J = 7.4 Hz, 1H), 6.91 (t, J = 7.0 Hz, 2H), 6.36 (s, 1H), 4.55 (s, 1H), 3.81 (s, 3H), 3.61–3.53 (m, 1H), 3.51–3.43 (m, 1H), 3.15 (s, 2H), 3.01–2.85 (m, 2H), 2.41 (t, J = 8.0 Hz, 2H), 2.37 (s, 3H), 2.10–1.96 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.85, 156.69, 143.06, 136.61, 135.39, 133.67, 129.51, 129.38, 128.45, 127.31, 126.97, 126.06, 122.17, 120.55, 119.53, 118.42, 111.32, 110.83, 109.01, 55.63, 49.40, 48.55, 43.16, 31.53, 24.41, 21.50, 18.54; IR (KBr) ν_max: 3259, 2937, 2855, 1655, 1490, 1460, 1438, 1324, 1244, 1161, 1106, 1020, 872, 816, 748, 551, 497 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1909%.

N-(2-(1-((3-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4c). White solid (m.p. 75–76 °C), 17% yield (45.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.72 (s, 1H), 7.64 (d, J = 8.0 Hz, 2H), 7.49–7.42 (m, 2H), 7.35 (t, J = 8.0 Hz, 1H), 7.22 (d, J = 8.0 Hz, 3H), 7.14 (t, J = 7.4 Hz, 1H), 6.94 (d, J = 8.0 Hz, 1H), 6.80 (d, J = 7.6 Hz, 1H), 6.77–6.73 (m, 2H), 4.31 (s, 1H), 3.79 (s, 3H), 3.50–3.42 (m, 1H), 3.30–3.20 (m, 2H), 2.92–2.83 (m, 2H), 2.68–2.59 (m, 1H), 2.57–2.47 (m, 1H), 2.45–2.34 (m, 4H), 2.13–2.02 (m, 1H), 1.98–1.88 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.62, 160.16, 143.35, 136.96, 136.51, 130.14, 129.65, 127.83, 126.95, 124.71, 122.77, 120.36, 119.11, 118.81, 113.72, 113.09, 111.86, 110.69, 63.65, 55.38, 43.42, 43.12, 30.75, 25.68, 21.52, 17.99; IR (KBr) ν_max: 3529, 3147, 2941, 1675, 1595, 1492, 1462, 1329, 1225, 1158, 1094, 816, 745, 658, 550, 428 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1929%.

N-(2-(2-((3-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3c). White solid (m.p. 136–137 °C), 60% yield (153.1 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.49 (s, 1H), 7.61 (d, J = 7.8 Hz, 2H), 7.47 (d, J = 7.8 Hz, 1H), 7.31–7.23 (m, 2H), 7.22–7.16 (m, 3H), 7.09 (t, J = 7.4 Hz, 1H), 6.83 (d, J = 8.0 Hz, 1H), 6.67 (d, J = 7.8 Hz, 1H), 6.65 (s, 1H), 6.44 (s, 1H), 4.76 (s, 1H), 3.75 (s, 3H), 3.67–3.59 (m, 1H), 3.41–3.33 (m, 1H), 3.20 (s, 2H), 3.08–2.91 (m, 2H), 2.49 (t, J = 8.0 Hz, 2H), 2.38 (s, 3H), 2.15–2.03 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.02, 158.94, 142.03, 137.78, 135.73, 134.72, 131.27, 128.89, 128.50, 126.23, 125.96, 121.50, 118.66, 118.13, 117.71, 112.20, 111.42, 110.39, 110.26, 54.27, 50.61, 45.47, 42.37, 30.08, 23.60, 20.49, 17.18; IR (KBr) ν_max: 3312, 3221, 2920, 1650, 1491, 1462, 1332, 1245, 1162, 1094, 1053, 874, 816, 766, 748, 549, 501 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1932%.

N-(2-(1-((4-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4d). White solid (m.p. 48–49 °C), 4% yield (10.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.68 (s, 1H), 7.55 (d, J = 7.9 Hz, 2H), 7.45–7.35 (m, 2H), 7.32 (d, J = 8.2 Hz, 1H), 7.23–7.18 (m, 1H), 7.16 (d, J = 7.9 Hz, 2H), 7.12–7.05 (m, 2H), 7.03–6.95 (m, 2H), 6.63 (s, 1H), 4.21 (s, 1H), 3.71 (s, 3H), 3.45–3.36 (m, 1H), 3.29–3.14 (m, 2H), 2.91–2.83 (m, 1H), 2.80–2.72 (m, 1H), 2.70–2.62 (m, 1H), 2.51–2.41 (m, 2H), 2.38 (s, 3H), 2.12–2.02 (m, 1H), 1.98–1.90 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.36, 157.29, 143.25, 136.79, 136.35, 130.53, 129.59, 127.66, 126.89, 124.05, 123.75, 122.52, 120.55, 119.93, 118.70, 111.18, 110.61, 61.31, 55.68, 44.67, 42.79, 30.93, 25.42, 21.50, 18.29; IR (KBr) ν_max: 3150, 2928, 1670, 1598, 1490, 1457, 1411, 1328, 1267, 1159, 1089, 1016, 712, 698, 635, 576, 544 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1922%.

N-(2-(2-((4-Methoxyphenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3d). White solid (m.p. 203–204 °C), 70% yield (182.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 9.06 (s, 1H), 7.55 (d, J = 7.8 Hz, 2H), 7.37 (d, J = 7.8 Hz, 1H), 7.34–7.27 (m, 2H), 7.20–7.13 (m, 4H), 7.03 (t, J = 7.4 Hz, 1H), 6.91 (t, J = 6.9 Hz, 2H), 6.36 (s, 1H), 4.58 (s, 1H), 3.81 (s, 3H), 3.61–3.53 (m, 1H), 3.51–3.42 (m, 1H), 3.15 (s, 2H), 3.01–2.85 (m, 2H), 2.42 (t, J = 7.9 Hz, 2H), 2.37 (s, 3H), 2.10–1.96 (m, 2H); ¹³C NMR (75 MHz, DMSO-d₆) δ 174.17, 156.97, 142.94, 138.00, 135.98, 133.43, 130.02, 129.39, 127.99, 126.99, 121.42, 120.79, 119.04, 118.19, 111.86, 111.37, 108.91, 55.86, 47.40, 46.12, 43.60, 30.79, 24.86, 21.37, 18.15; IR (KBr) ν_max: 3424, 3215, 2964, 2916, 2849, 1669, 1598, 1493, 1461, 1421, 1324, 1160, 1105, 1022, 934, 912, 817, 800, 751, 739, 653, 572, 551, 498 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₄S: [M + Na]⁺ 540.1927, found: 540.1932%.

4-Methyl-N-(2-(1-((2-oxopyrrolidin-1-yl)(p-tolyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4e). White solid (m.p. 37–38), 14% yield (21.5 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.72 (s, 1H), 7.64 (d, J = 7.9 Hz, 2H), 7.45 (t, J = 7.9 Hz, 2H), 7.23 (t, J = 8.2 Hz, 5H), 7.16–7.11 (m, 1H), 7.09 (d, J = 7.8 Hz, 2H), 6.75 (s, 1H), 4.28 (s, 1H), 3.45 (t, J = 7.4 Hz, 1H), 3.30–3.19 (m, J = 6.3 Hz, 2H), 2.91–2.82 (m, 2H), 2.70–2.61 (m, 1H), 2.58–2.48 (m, 1H), 2.46–2.34 (m, 7H), 2.15–2.03 (m, 1H), 1.99–1.88 (m, 1H); ¹³C NMR (100 MHz, CDCl₃) δ 175.90, 143.50, 138.83, 137.26, 137.14, 132.01, 129.93, 129.86, 128.13, 127.18, 127.06, 124.88, 122.88, 120.49, 119.05, 112.07, 110.93, 63.90, 43.62, 43.44, 31.05, 25.91, 21.76, 21.39, 18.21; IR (KBr) ν_max: 3183, 2923, 1652, 1458, 1327, 1158, 1095, 780, 741, 545, 495 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₃S: [M + Na]⁺ 524.1978, found: 524.1970%.

4-Methyl-N-(2-(2-((2-oxopyrrolidin-1-yl)(p-tolyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3e). White solid (m.p. 157–158), 63% yield (95.1 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.55 (s, 1H), 7.60 (d, J = 7.9 Hz, 2H), 7.46 (d, J = 7.8 Hz, 1H), 7.28 (d, J = 8.3 Hz, 1H), 7.18 (d, J = 7.5 Hz, 3H), 7.13 (d, J = 7.7 Hz, 2H), 7.08 (t, J = 7.4 Hz, 1H), 6.97 (d, J = 7.7 Hz, 2H), 6.41 (s, 1H), 4.80 (s, 1H), 3.67–3.58 (m, 1H), 3.44–3.35 (m, 1H), 3.19 (s, 2H), 3.07–2.92 (m, 2H), 2.49 (t, J = 7.9 Hz, 2H), 2.37 (s, 3H), 2.34 (s, 3H), 2.13–2.03 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.07, 142.04, 136.49, 135.71, 134.63, 132.90, 131.81, 128.49, 126.19, 125.97, 125.69, 121.52, 118.71, 117.67, 110.30, 110.02, 50.73, 45.83, 42.28, 30.25, 23.56, 20.49, 20.05, 17.24; IR (KBr) ν_max: 3390, 3085, 2919, 1659, 1514, 1493, 1461, 1328, 1295, 1211, 1159, 1073, 913, 823, 747, 655, 573 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₃S: [M + Na]⁺ 524.1978, found: 524.1974%.

4-Methyl-N-(2-(1-((2-oxopyrrolidin-1-yl)(o-tolyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4f). White solid (m.p. 47–48 °C), 26% yield (65.4 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.62 (d, J = 8.1 Hz, 2H), 7.58 (s, 1H), 7.44 (d, J = 7.9 Hz, 1H), 7.36–7.29 (m, 2H), 7.28–7.27 (m, 1H), 7.25–7.20 (m, 3H), 7.20–7.15 (m, 2H), 7.13 (t, J = 7.5 Hz, 1H), 6.53 (s, 1H), 4.39 (s, 1H), 3.48–3.41 (m, 1H), 3.24–3.16 (m, 2H), 2.81 (t, J = 6.9 Hz, 2H), 2.59–2.42 (m, 3H), 2.39 (s, 3H), 2.17–2.04 (m, 1H), 1.99–1.90 (m, 4H); ¹³C NMR (75 MHz, CDCl₃) δ 175.34, 143.35, 137.07, 136.20, 133.68, 131.55, 129.65, 129.07, 127.80, 126.93, 126.32, 125.59, 123.76, 122.92, 120.40, 118.95, 111.76, 110.18, 76.60, 62.98, 44.36, 43.13, 30.84, 25.61, 21.52, 18.86, 18.16; IR (KBr) ν_max: 3488, 2923, 2134, 1670, 1459, 1414, 1327, 1287, 1266, 1155, 1094, 818, 745, 686, 661, 552 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₃S: [M + Na]⁺ 524.1984, found: 524.1979%.

4-Methyl-N-(2-(2-((2-oxopyrrolidin-1-yl)(o-tolyl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3f). White solid (m.p. 169–170 °C), 54% yield (134.5 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.05 (s, 1H), 7.64 (d, J = 7.6 Hz, 2H), 7.44 (d, J = 7.5 Hz, 1H), 7.26–7.19 (m, 5H), 7.18–7.11 (m, 3H), 7.11–7.04 (m, 1H), 6.57 (s, 1H), 5.02 (s, 1H), 3.51–3.39 (m, 1H), 3.21–3.01 (m, 3H), 2.95–2.83 (m, 2H), 2.51–2.42 (m, 2H), 2.39 (s, 3H), 2.06 (s, 3H), 2.04–1.96 (m, 1H), 1.84 (s, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.43, 143.12, 136.79, 136.56, 135.75, 135.38, 132.02, 131.33, 129.56, 128.14, 127.77, 127.07, 126.35, 126.06, 122.40, 119.89, 118.62, 111.25, 110.51, 50.41, 46.66, 43.25, 30.99, 24.63, 21.51, 19.36, 18.20; IR (KBr) ν_max: 3428, 3188, 2918, 1653, 1457, 1433, 1307, 1322, 1289, 1158, 1093, 748, 720, 667, 550, 484, 456 cm⁻¹; HRMS (ESI): calcd for C₂₉H₃₁N₃NaO₃S: [M + Na]⁺ 524.1984, found: 524.1971%.

N-(2-(1-((4-Fluorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4g). White solid (m.p. 144–145 °C), 16% yield (40.5 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.72 (s, 1H), 7.65 (d, J = 7.8 Hz, 2H), 7.48–7.40 (m, 2H), 7.23 (d, J = 7.6 Hz, 3H), 7.21–7.16 (m, 2H), 7.16–7.07 (m, 3H), 6.74 (s, 1H), 4.32 (s, 1H), 3.47–3.39 (m, 1H), 3.30–3.21 (m, 2H), 2.89 (t, J = 6.6 Hz, 2H), 2.73–2.62 (m, 1H), 2.58–2.48 (m, 1H), 2.46–2.35 (m, 4H), 2.14–2.02 (m, 1H), 2.01–1.90 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.70, 143.38, 136.99, 130.70, 129.65, 128.81, 128.70, 127.90, 126.94, 124.44, 122.84, 120.44, 118.88, 116.19, 115.90, 112.20, 110.66, 63.37, 43.32, 43.11, 30.72, 25.69, 21.51, 17.98; IR (KBr) ν_max: 3405, 2921, 1667, 1508, 1459, 1327, 1232, 1159, 1087, 744, 550, 457, 418 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈FN₃NaO₃S: [M + Na]⁺ 528.1728, found: 528.1711%.

N-(2-(2-((4-Fluorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3g). White solid (m.p. 167–16), 60% yield (150.5 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.70 (s, 1H), 7.60 (d, J = 7.6 Hz, 2H), 7.46 (d, J = 7.7 Hz, 1H), 7.30 (d, J = 8.0 Hz, 1H), 7.19 (d, J = 7.4 Hz, 3H), 7.13–7.03 (m, 3H), 7.03–6.95 (m, 2H), 6.35 (s, 1H), 4.75 (s, 1H), 3.69–3.58 (m, 1H), 3.50–3.40 (m, 1H), 3.18 (s, 2H), 3.09–2.92 (m, 2H), 2.54–2.45 (m, 2H), 2.38 (s, 3H), 2.15–2.04 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 176.20, 143.15, 136.69, 135.81, 132.96, 132.31, 129.54, 128.62, 128.51, 126.95, 122.65, 119.76, 118.71, 115.79, 115.50, 111.47, 111.24, 51.56, 46.88, 43.40, 31.20, 24.66, 21.50, 18.24; IR (KBr) ν_max: 3371, 3189, 2933, 1644, 1599, 1512, 1459, 1300, 1233, 1146, 1095, 869, 812, 746, 672, 573, 549 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈FN₃NaO₃S: [M + Na]⁺ 528.1728, found: 528.1712%.

N-(2-(1-((4-Bromophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4h). White solid (m.p. 77–78 °C), 15% yield (41.2 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.69 (s, 1H), 7.65 (d, J = 7.8 Hz, 2H), 7.56 (d, J = 8.1 Hz, 2H), 7.48–7.40 (m, 2H), 7.24 (d, J = 7.4 Hz, 3H), 7.15 (t, J = 7.1 Hz, 1H), 7.09 (d, J = 7.8 Hz, 2H), 6.72 (s, 1H), 4.33 (s, 1H), 3.41 (s, 1H), 3.29–3.21 (m, 2H), 2.92–2.95 (m, 2H), 2.72–2.63 (m, 1H), 2.58–2.48 (m, 1H), 2.46–2.35 (m, 4H), 2.15–2.02 (m, 1H), 2.01–1.90 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.70, 143.40, 136.97, 136.88, 134.07, 132.21, 129.66, 128.65, 127.86, 126.94, 124.41, 122.92, 120.50, 118.89, 112.29, 110.65, 63.40, 43.31, 43.09, 30.67, 25.68, 21.53, 17.98; IR (KBr) ν_max: 3442, 3179, 1663, 1458, 1416, 1328, 1263, 1157, 1088, 813, 801, 745, 548, 428, 420 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈⁸¹BrN₃NaO₃S: [M + Na]⁺ 590.0912, found: 590.0917%.

N-(2-(2-((4-Bromophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3h). White solid (m.p. 204–205 °C), 83% yield (235.2 mg); ¹H NMR (400 MHz, DMSO-d₆) δ 10.70 (s, 1H), 7.63 (d, J = 7.9 Hz, 3H), 7.55 (d, J = 8.1 Hz, 2H), 7.40 (d, J = 7.8 Hz, 1H), 7.33 (d, J = 7.8 Hz, 2H), 7.28 (d, J = 8.0 Hz, 1H), 7.11–6.94 (m, 4H), 6.53 (s, 1H), 3.45–3.38 (m, 1H), 3.05–2.96 (m, 7.9 Hz, 1H), 2.89–2.75 (m, 4H), 2.44–2.36 (m, 1H), 2.35 (s, 3H), 2.30–2.17 (m, 1H), 2.07–1.95 (m, 1H), 1.95–1.82 (m, 1H); ¹³C NMR (75 MHz, DMSO-d₆) δ 173.61, 141.89, 137.00, 136.96, 135.42, 131.22, 130.83, 128.95, 128.52, 126.45, 125.97, 121.00, 119.89, 118.18, 117.74, 110.93, 110.08, 49.07, 43.83, 43.01, 29.63, 23.88, 20.37, 17.05; IR (KBr) ν_max: 3351, 3196, 2923, 1648, 1489, 1436, 1309, 1145, 1094, 1010, 929, 913, 812, 748, 670, 542, 521 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈⁸¹BrN₃NaO₃S: [M + Na]⁺ 590.0912, found: 590.0914%.

N-(2-(1-((4-Chlorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4i). White solid (m.p. 52–53 °C), 15% yield (38.4 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.71 (s, 1H), 7.65 (d, J = 7.8 Hz, 2H), 7.49–7.42 (m, 2H), 7.41 (d, J = 7.5 Hz, 2H), 7.23 (d, J = 7.5 Hz, 3H), 7.15 (d, J = 7.4 Hz, 3H), 6.73 (s, 1H), 4.33 (s, 1H), 3.42 (t, J = 7.8 Hz, 1H), 3.31–3.19 (m, 2H), 2.89 (t, J = 6.4 Hz, 2H), 2.73–2.63 (m, 1H), 2.59–2.48 (m, 1H), 2.45–2.35 (m, 4H), 2.15–2.02 (m, 1H), 2.00–1.90 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.71, 143.40, 136.98, 136.88, 134.76, 133.51, 129.65, 129.25, 128.34, 127.88, 126.93, 124.41, 122.89, 120.49, 118.89, 112.29, 110.65, 63.37, 43.33, 43.09, 30.67, 25.68, 21.52, 17.98; IR (KBr) ν_max: 3414, 3188, 2925, 1664, 1492, 1459, 1329, 1286, 1158, 1089, 1011, 815, 745, 544 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈ClN₃NaO₃S: [M + Na]⁺ 544.1432, found: 544.1431%.

N-(2-(2-((4-Chlorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3i). White solid (m.p. 216–217), 70% yield (182.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.71 (s, 1H), 7.60 (d, J = 8.0 Hz, 2H), 7.47 (d, J = 7.9 Hz, 1H), 7.29 (t, J = 8.0 Hz, 3H), 7.20 (t, J = 6.9 Hz, 3H), 7.09 (t, J = 7.4 Hz, 1H), 7.02 (d, J = 8.2 Hz, 2H), 6.32 (s, 1H), 4.70 (s, 1H), 3.70–3.61 (m, 1H), 3.51–3.43 (m, 1H), 3.24–3.12 (m, 2H), 3.10–2.92 (m, 2H), 2.55–2.44 (m, 2H), 2.38 (s, 3H), 2.18–2.07 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 176.29, 143.22, 136.64, 135.79, 135.74, 133.65, 132.29, 129.57, 128.95, 128.13, 126.98, 122.84, 119.89, 118.69, 111.44, 111.26, 51.99, 47.50, 43.26, 31.28, 24.73, 21.50, 18.34; IR (KBr) ν_max: 3320, 3212, 2922, 1667, 1598, 1490, 1461, 1437, 1334, 1307, 1161, 1090, 1058, 1014, 871, 804, 756, 742, 659, 573, 548, 499 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈ClN₃NaO₃S: [M + Na]⁺ 544.1432, found: 544.1434%.

N-(2-(1-((3-Chlorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4j). White solid (m.p. 57–58 °C), 22% yield (58.0 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.71 (s, 1H), 7.65 (d, J = 7.7 Hz, 2H), 7.49–7.41 (m, 2H), 7.40–7.33 (m, 2H), 7.26–7.17 (m, 4H), 7.15 (t, J = 7.4 Hz, 1H), 7.09 (d, J = 6.5 Hz, 1H), 6.72 (s, 1H), 4.44 (s, 1H), 3.43 (t, J = 7.9 Hz, 1H), 3.25 (s, 2H), 2.89 (t, J = 6.5 Hz, 2H), 2.72–2.62 (m, 1H), 2.61–2.48 (m, 1H), 2.46–2.33 (m, 4H), 2.18–2.04 (m, 1H), 2.01–1.89 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.78, 143.36, 137.21, 137.00, 136.91, 135.15, 130.40, 129.66, 129.03, 127.88, 126.94, 125.26, 124.38, 122.92, 120.51, 118.93, 112.47, 110.58, 63.27, 43.34, 43.14, 30.64, 25.69, 21.52, 17.97; IR (KBr) ν_max: 3463, 2928, 2880, 1739, 1654, 1599, 1490, 1458, 1384, 1234, 1217, 1155, 1105, 1093, 1020, 743, 667, 582, 548, 470 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈ClN₃NaO₃S: [M + Na]⁺ 544.1432, found: 544.1431%.

N-(2-(2-((3-Chlorophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3j). White solid (m.p. 74–75 °C), 75% yield (194.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.70 (s, 1H), 7.60 (d, J = 7.5 Hz, 2H), 7.47 (d, J = 7.8 Hz, 1H), 7.33–7.26 (m, 2H), 7.25–7.15 (m, 4H), 7.14–7.03 (m, 2H), 6.97 (d, J = 6.0 Hz, 1H), 6.35 (s, 1H), 4.77 (s, 1H), 3.69–3.59 (m, 1H), 3.49–3.39 (m, 1H), 3.23–3.13 (m, 2H), 3.10–2.90 (m, 2H), 2.49 (t, J = 7.8 Hz, 2H), 2.38 (s, 3H), 2.16–2.06 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 176.21, 143.14, 139.57, 136.75, 135.89, 134.81, 131.78, 130.08, 129.55, 127.93, 127.09, 126.95, 126.83, 125.09, 122.75, 119.80, 118.76, 111.53, 51.71, 46.95, 43.40, 31.10, 24.74, 21.49, 18.24; IR (KBr) ν_max: 3344, 2926, 1665, 1596, 1459, 1420, 1325, 1157, 1094, 890, 814, 745, 659, 550 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈ClN₃NaO₃S: [M + Na]⁺ 544.1432, found: 544.1433%.

N-(2-(1-((2-Bromophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4k). White solid (m.p. 44–45 °C), 10% yield (28.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.66 (d, J = 7.8 Hz, 1H), 7.62 (d, J = 7.8 Hz, 2H), 7.55 (s, 1H), 7.42 (d, J = 7.7 Hz, 1H), 7.36 (t, J = 7.6 Hz, 1H), 7.32–7.26 (m, 2H), 7.23–7.17 (m, 3H), 7.13–7.07 (m, 2H), 6.62 (s, 1H), 4.51 (t, J = 6.0 Hz, 1H), 3.39–3.31 (m, 1H), 3.28–3.15 (m, 2H), 2.93–2.75 (m, 3H), 2.57–2.44 (m, 2H), 2.38 (s, 3H), 2.16–2.07 (m, 1H), 2.05–1.98 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.52, 143.27, 136.95, 136.22, 135.09, 134.05, 130.62, 129.63, 127.90, 127.75, 126.91, 123.64, 123.48, 122.82, 120.29, 118.90, 111.92, 110.26, 65.20, 44.83, 43.00, 30.74, 25.57, 21.52, 18.32; IR (KBr) ν_max: 3413, 2919, 1679, 1460, 1411, 1328, 1285, 1156, 1093, 1018, 812, 749, 669, 551, 446 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈BrN₃NaO₃S: [M + Na]⁺ 588.0932, found: 588.0934%.

N-(2-(2-((2-Bromophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3k). White solid (m.p. 165–166), 76% yield (214.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.69 (s, 1H), 7.60 (d, J = 7.7 Hz, 2H), 7.56 (d, J = 7.9 Hz, 1H), 7.42 (d, J = 7.8 Hz, 1H), 7.31–7.25 (m, 2H), 7.20–7.12 (m, 4H), 7.06 (t, J = 7.3 Hz, 1H), 6.35 (s, 1H), 4.81 (s, 1H), 3.43 (t, J = 6.6 Hz, 2H), 3.18–3.06 (m, 2H), 2.96–2.83 (m, 2H), 2.42 (t, J = 7.9 Hz, 2H), 2.38 (s, 3H), 2.09–1.99 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.99, 143.19, 137.15, 136.63, 135.60, 133.65, 132.13, 129.71, 129.59, 129.32, 127.70, 127.05, 123.54, 122.63, 119.92, 118.66, 111.39, 110.38, 53.94, 48.26, 43.08, 31.26, 24.67, 21.53, 18.49; IR (KBr) ν_max: 3362, 2924, 1668, 1597, 1493, 1461, 1417, 1324, 1289, 1157, 1093, 1020, 814, 746, 661, 550, 435 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈BrN₃NaO₃S: [M + Na]⁺ 588.0932, found: 588.0925%.

N-(2-(1-((4-Cyanophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (4l). White solid (m.p. 84–85 °C), 27% yield (69.6 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.76 (s, 1H), 7.71 (d, J = 7.3 Hz, 2H), 7.65 (d, J = 7.8 Hz, 2H), 7.47 (d, J = 8.0 Hz, 1H), 7.39 (d, J = 8.1 Hz, 1H), 7.34 (d, J = 7.5 Hz, 2H), 7.25–7.19 (m, 3H), 7.15 (t, J = 6.9 Hz, 1H), 6.73 (s, 1H), 4.73 (t, J = 5.2 Hz, 1H), 3.40 (t, J = 8.7 Hz, 1H), 3.28–3.18 (m, 2H), 2.90 (t, J = 6.5 Hz, 2H), 2.78–2.69 (m, 1H), 2.58–2.49 (m, 1H), 2.45–2.35 (m, 4H), 2.15–2.03 (m, 1H), 2.03–1.90 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.92, 143.43, 140.52, 136.96, 136.85, 132.84, 129.67, 127.80, 126.90, 124.27, 123.03, 120.64, 119.02, 118.23, 112.96, 112.76, 110.49, 63.48, 43.40, 43.05, 30.54, 25.67, 21.52, 17.96; IR (KBr) ν_max: 3277, 2925, 2853, 2229, 1677, 1598, 1507, 1460, 1412, 1326, 1158, 1094, 1017, 880, 814, 744, 660, 550, 427 cm⁻¹; HRMS (ESI): calcd for C₂₉H₂₈N₄NaO₃S: [M + Na]⁺ 535.1780, found: 535.1783%.

N-(2-(2-((4-Cyanophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)-4-methylbenzenesulfonamide (3l). White solid (m.p. 245–246 °C), 68% yield (176.2 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.94 (s, 1H), 7.63–7.54 (m, 4H), 7.50–7.42 (m, 1H), 7.35–7.27 (m, 1H), 7.24–7.16 (m, 5H), 7.14–7.06 (m, 1H), 6.26 (s, 1H), 4.60 (s, 1H), 3.79–3.68 (m, 1H), 3.63–3.52 (m, 1H), 3.25–3.13 (m, 2H), 3.11–2.94 (m, 2H), 2.58–2.44 (m, 2H), 2.40 (s, 3H), 2.22–2.10 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 176.61, 143.42, 143.06, 136.52, 135.88, 132.53, 131.76, 129.64, 127.44, 126.98, 126.68, 123.13, 120.00, 118.68, 111.61, 111.55, 52.89, 48.38, 43.20, 31.28, 24.92, 21.51, 18.46; IR (KBr) ν_max: 3247, 2914, 2231, 1664, 1605, 1493, 1459, 1332, 1268, 1162, 1059, 872, 763, 746, 659, 562, 550 cm⁻¹; HRMS (ESI): calcd for C₂₉H₂₈N₄NaO₃S: [M + Na]⁺ 535.1780, found: 535.1765%.

4-Methyl-N-(2-(1-((4-nitrophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4m). White solid (m.p. 45–46 °C), 15% yield (39.6 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.29 (d, J = 8.5 Hz, 2H), 7.81 (s, 1H), 7.66 (d, J = 8.0 Hz, 2H), 7.49 (d, J = 7.7 Hz, 1H), 7.41 (d, J = 8.1 Hz, 3H), 7.26–7.22 (m, 3H), 7.17 (t, J = 7.4 Hz, 1H), 6.74 (s, 1H), 4.34 (s, 1H), 3.47–3.39 (m, 1H), 3.30–3.21 (m, 2H), 2.92 (t, J = 6.5 Hz, 2H), 2.80–2.71 (m, 1H), 2.62–2.52 (m, 1H), 2.48–2.37 (m, 4H), 2.20–2.08 (m, 1H), 2.05–1.96 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.93, 148.10, 143.47, 142.41, 136.91, 136.84, 129.68, 128.06, 127.93, 126.90, 124.22, 123.10, 120.71, 119.05, 113.06, 110.50, 63.42, 43.43, 43.05, 30.52, 25.68, 21.51, 17.99; IR (KBr) ν_max: 3417, 3164, 2925, 1667, 1598, 1519, 1458, 1412, 1349, 1264, 1158, 1084, 1016, 811, 800, 748, 628, 552 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈N₄NaO₅S: [M + Na]⁺ 555.1673, found: 555.1670%.

4-Methyl-N-(2-(2-((4-nitrophenyl)(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3m). White solid (m.p. 107–108 °C), 84% yield (222.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 9.00 (s, 1H), 8.14 (d, J = 7.8 Hz, 2H), 7.60 (d, J = 7.4 Hz, 2H), 7.48 (d, J = 7.5 Hz, 1H), 7.31 (t, J = 11.0 Hz, 1H), 7.26–7.15 (m, 5H), 7.15–7.05 (m, 1H), 6.28 (s, 1H), 4.63 (s, 1H), 3.82–3.69 (m, 1H), 3.68–3.54 (m, 1H), 3.16 (s, 2H), 3.12–2.94 (m, 2H), 2.60–2.44 (m, 2H), 2.39 (s, 3H), 2.24–2.08 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 176.65, 147.26, 145.11, 143.46, 136.45, 135.92, 131.69, 129.64, 127.63, 126.97, 126.67, 123.89, 123.15, 120.00, 118.70, 111.65, 111.58, 52.81, 48.40, 43.25, 31.27, 24.93, 21.51, 18.47; IR (KBr) ν_max: 3317, 3242, 2915, 1671, 1597, 1517, 1459, 1433 1356, 1162, 1084, 1014, 877, 766, 749, 659, 547 cm⁻¹; HRMS (ESI): calcd for C₂₈H₂₈N₄NaO₅S: [M + Na]⁺ 555.1673, found: 555.1671%.

4-Methyl-N-(2-(1-(naphthalen-1-yl(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4n). White solid (m.p. 72–73 °C), 16% yield (43.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.92–2.87 (m, 3H), 7.87–7.82 (m, 1H), 7.69 (s, 1H), 7.62 (d, J = 8.0 Hz, 2H), 7.58–7.53 (m, 2H), 7.48 (t, J = 7.4 Hz, 2H), 7.29–7.22 (m, 2H), 7.15 (t, J = 7.4 Hz, 3H), 6.72 (s, 1H), 4.32 (s, 1H), 3.58–3.50 (m, 1H), 3.29–3.22 (m, 2H), 2.86 (t, J = 6.5 Hz, 2H), 2.75–2.66 (m, 1H), 2.64–2.55 (m, 1H), 2.50–2.40 (m, 1H), 2.35 (s, 3H), 2.21–2.12 (m, 1H), 2.03–1.94 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.76, 143.32, 137.02, 136.95, 133.24, 133.09, 132.29, 129.61, 129.07, 128.20, 127.86, 127.75, 126.92, 126.87, 126.77, 125.83, 124.76, 124.56, 122.87, 120.44, 118.87, 111.92, 110.75, 64.00, 43.54, 43.05, 30.83, 25.63, 21.46, 18.08; IR (KBr) ν_max: 3277, 2923, 1670, 1459, 1328, 1157, 1093, 821, 746, 661, 554, 476 cm⁻¹; HRMS (ESI): calcd for C₃₂H₃₁N₃NaO₃S: [M + Na]⁺ 560.1978, found: 560.1975%.

4-Methyl-N-(2-(2-(naphthalen-1-yl(2-oxopyrrolidin-1-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3n). White solid (m.p. 193–194 °C), 71% yield (190.2 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.95 (s, 1H), 7.60 (d, J = 7.6 Hz, 4H), 7.47 (d, J = 7.8 Hz, 1H), 7.32 (d, J = 8.0 Hz, 1H), 7.26–7.17 (m, 8H), 7.11 (t, J = 7.4 Hz, 1H), 6.27 (s, 1H), 4.61 (s, 1H), 3.79–3.71 (m, 1H), 3.62–3.55 (m, 1H), 3.20 (s, 2H), 3.13–2.97 (m, 2H), 2.57–2.47 (m, 2H), 2.40 (s, 3H), 2.21–2.12 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.56, 142.39, 142.07, 135.47, 134.86, 131.49, 130.70, 128.61, 126.45, 125.95, 125.66, 122.07, 118.95, 117.66, 117.45, 110.59, 110.53, 51.80, 47.29, 42.20, 30.27, 23.87, 20.50, 17.36; IR (KBr) ν_max: 3322, 3209, 2923, 1655, 1489, 1464, 1435, 1328, 1151, 1091, 818, 751, 657, 565, 551, 497 cm⁻¹; HRMS (ESI): calcd for C₃₂H₃₁N₃NaO₃S: [M + Na]⁺ 560.1978, found: 560.1973%.

4-Methyl-N-(2-(1-((2-oxopyrrolidin-1-yl)(thiophen-2-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (4o). White solid (m.p. 99–100 °C), 12% yield (29.0 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.89 (s, 1H), 7.80–7.75 (m, 1H), 7.64 (t, J = 6.7 Hz, 2H), 7.51–7.32 (m, 3H), 7.25–7.19 (m, 3H), 7.19–7.10 (m, 1H), 7.09–7.04 (m, 1H), 6.99 (s, 1H), 4.62–4.49 (m, 1H), 3.40 (t, J = 7.0 Hz, 1H), 3.30–3.22 (m, 2H), 2.95–2.85 (m, 2H), 2.74–2.65 (m, 1H), 2.54–2.43 (m, 1H), 2.39 (s, 3H), 2.37–2.27 (m, 1H), 2.10–1.99 (m, 1H), 1.95–1.84 (m, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 177.61, 145.82, 141.09, 139.42, 139.06, 132.12, 132.08, 129.97, 129.47, 129.43, 128.97, 126.83, 125.36, 123.02, 121.32, 114.48, 113.11, 63.43, 45.59, 45.52, 33.16, 28.14, 24.00, 20.44; IR (KBr) ν_max: 3389, 2926, 1673, 1596, 1458, 1318, 1156, 1090, 1078, 815, 742, 640, 545, 504 cm⁻¹; HRMS (ESI): calcd for C₂₆H₂₇N₃NaO₃S₂: [M + Na]⁺ 516.1386, found: 516.1393%.

4-Methyl-N-(2-(2-((2-oxopyrrolidin-1-yl)(thiophen-2-yl)methyl)-1H-indol-3-yl)ethyl)benzenesulfonamide (3o). White solid (m.p. 137–138 °C), 73% yield (179.6 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.82 (s, 1H), 7.61 (d, J = 7.8 Hz, 2H), 7.46 (d, J = 7.8 Hz, 1H), 7.33 (d, J = 8.0 Hz, 1H), 7.30–7.26 (m, 1H), 7.23–7.16 (m, J = 9.0 Hz, 3H), 7.09 (t, J = 7.3 Hz, 1H), 6.98–6.93 (m, 1H), 6.77 (s, 1H), 6.59 (s, 1H), 4.70 (s, 1H), 3.77–3.69 (m, 1H), 3.47–3.38 (m, 1H), 3.26–3.12 (m, 2H), 3.08–2.93 (m, 2H), 2.47 (t, J = 7.9 Hz, 2H), 2.38 (s, 3H), 2.13–2.01 (m, 2H); ¹³C NMR (75 MHz, CDCl₃) δ 175.78, 143.07, 141.23, 136.79, 135.71, 131.88, 129.53, 127.24, 127.17, 126.98, 126.21, 125.46, 122.73, 119.79, 118.83, 111.52, 110.71, 48.65, 46.25, 43.36, 31.14, 24.61, 21.51, 18.21; IR (KBr) ν_max: 3354, 3175, 2935, 2868, 1652, 1597, 1490, 1459, 1425, 1301, 1146, 1095, 933, 812, 748, 721, 672, 574, 542 cm⁻¹; HRMS (ESI): calcd for C₂₆H₂₇N₃NaO₃S₂: [M + Na]⁺ 516.1386, found: 516.1382%.

N-(2-(1-((2-Oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)acetamide (4p). White solid (m.p. 102–103 °C), 23% yield (42.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.78 (s, 1H), 7.61 (d, J = 7.6 Hz, 1H), 7.48 (d, J = 7.9 Hz, 1H), 7.45–7.38 (m, 3H), 7.24–7.19 (m, 3H), 7.18–7.10 (m, 1H), 6.79 (s, 1H), 5.49 (s, 1H), 3.59–3.44 (m, 3H), 2.96–2.87 (m, 2H), 2.64–2.64 (m, 1H), 2.59–2.49 (m, 1H), 2.47–2.33 (m, 1H), 2.15–2.03 (m, 1H), 1.99–1.87 (m, 4H); ¹³C NMR (75 MHz, CDCl₃) δ 175.59, 170.03, 136.98, 134.95, 128.99, 128.76, 128.19, 126.86, 124.18, 122.71, 120.31, 118.95, 113.09, 110.61, 63.74, 43.35, 39.83, 30.76, 25.28, 23.30, 17.98; IR (KBr) ν_max: 3308, 2942, 1696, 1637, 1550, 1459, 1448, 1411, 1278, 1261, 765, 742, 703, 484, 444 cm⁻¹; HRMS (ESI): calcd for C₂₃H₂₅N₃NaO₂: [M + Na]⁺ 398.1839, found: 398.1840%.

N-(2-(2-((2-Oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)acetamide (3p). White solid (m.p. 147–148 °C), 30% yield (53.6 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.75 (s, 1H), 7.64 (d, J = 7.6 Hz, 1H), 7.37–7.27 (m, 4H), 7.23–7.18 (m, 1H), 7.17–7.10 (m, 3H), 6.44 (s, 1H), 5.87 (s, 1H), 3.62–3.42 (m, 4H), 3.07–2.96 (m, 2H), 2.53–2.41 (m, 2H), 2.15–2.06 (m, 2H), 1.76 (s, 3H); ¹³C NMR (75 MHz, CDCl₃) δ 175.69, 170.35, 137.34, 135.76, 132.20, 128.85, 127.82, 127.49, 126.90, 122.61, 119.74, 118.98, 112.27, 111.32, 52.26, 47.14, 40.31, 31.30, 24.26, 23.01, 18.38; IR (KBr) ν_max: 3276, 3089, 2940, 1652, 1563, 1492, 1459, 1433, 1285, 1270, 794, 743, 731, 703, 501 cm⁻¹; HRMS (ESI): calcd for C₂₃H₂₅N₃NaO₂: [M + Na]⁺ 398.1839, found: 398.1840%.

tert-Butyl(2-(1-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)carbamate (4q). White solid (m.p. 50–51 °C), 32% yield (69.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.79 (s, 1H), 7.62 (d, J = 7.7 Hz, 1H), 7.49 (d, J = 8.2 Hz, 1H), 7.44–7.37 (m, 3H), 7.23 (d, J = 7.4 Hz, 3H), 7.18 (t, J = 7.5 Hz, 1H), 6.79 (s, 1H), 4.63 (s, 1H), 3.50–3.43 (m, 1H), 3.42–3.35 (m, 2H), 2.90 (t, J = 6.7 Hz, 2H), 2.72–2.62 (m, 1H), 2.58–2.48 (m, 1H), 2.45–2.34 (m, 1H), 2.13–2.04 (m, 1H), 1.97–1.87 (m, 1H), 1.40 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 7.79 (s, 1H), 7.62 (d, J = 7.7 Hz, 1H), 7.49 (d, J = 8.2 Hz, 1H), 7.44–7.37 (m, 3H), 7.23 (d, J = 7.4 Hz, 3H), 7.18 (t, J = 7.5 Hz, 1H), 6.79 (s, 1H), 4.63 (s, 1H), 3.50–3.43 (m, 1H), 3.42–3.35 (m, 2H), 2.90 (t, J = 6.7 Hz, 2H), 2.72–2.62 (m, 1H), 2.58–2.48 (m, 1H), 2.45–2.34 (m, 1H), 2.13–2.04 (m, 1H), 1.97–1.87 (m, 1H), 1.40 (s, 9H); IR (KBr) ν_max: 3346, 2925, 1689, 1506, 1460, 1413, 1364, 1265, 1167, 743, 701, 521, 495, 472, 429 cm⁻¹; HRMS (ESI): calcd for C₂₆H₃₁N₃NaO₃: [M + Na]⁺ 456.2258, found: 456.2244%.

tert-Butyl(2-(2-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)ethyl)carbamate (3q). White solid (m.p. 147–148 °C), 65% yield (142.6 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.63 (s, 1H), 7.65 (d, J = 7.3 Hz, 1H), 7.37–7.27 (m, 4H), 7.20 (t, J = 7.2 Hz, 1H), 7.16–7.10 (m, 3H), 6.41 (s, 1H), 4.63 (s, 1H), 3.67–3.57 (m, 1H), 3.46–3.34 (m, 3H), 3.07–2.90 (m, 2H), 2.54–2.43 (m, 2H), 2.16–2.06 (m, 2H), 1.37 (s, 9H); ¹³C NMR (75 MHz, CDCl₃) δ 175.56, 155.85, 137.31, 135.64, 132.39, 128.81, 127.68, 127.57, 126.63, 122.55, 119.66, 119.15, 112.35, 111.24, 52.46, 47.38, 41.23, 31.29, 28.35, 24.92, 18.35; IR (KBr) ν_max: 3428, 3274, 2965, 2930, 1710, 1665, 1585, 1494, 1455, 1434, 1389, 1365, 1310, 1262, 1165, 1015, 958, 927, 861, 801, 748, 701, 660, 499 cm⁻¹; HRMS (ESI): calcd for C₂₆H₃₁N₃NaO₃: [M + Na]⁺ 456.2258, found: 456.2241%.

4-Methyl-N-(2-((1-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)methyl)phenyl)benzenesulfonamide (4r). White solid (m.p. 96–97 °C), 14% yield (39.3 mg); ¹H NMR (400 MHz, CDCl₃) δ 7.81 (s, 1H), 7.50 (d, J = 8.4 Hz, 1H), 7.48–7.38 (m, 3H), 7.35 (d, J = 7.9 Hz, 3H), 7.25–7.20 (m, 4H), 7.18 (d, J = 7.6 Hz, 1H), 7.14–7.07 (m, 4H), 7.04 (t, J = 7.4 Hz, 1H), 6.75 (s, 1H), 6.64 (s, 1H), 3.71 (s, 2H), 3.55–3.47 (m, 1H), 2.81–2.71 (m, 1H), 2.59–2.48 (m, 1H), 2.47–2.38 (m, 1H), 2.35 (s, 3H), 2.15–2.03 (m, 1H), 2.02–1.92 (s, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.77, 143.75, 137.52, 136.49, 135.47, 134.61, 131.53, 130.56, 129.57, 129.11, 128.79, 127.76, 126.93, 126.84, 125.62, 124.35, 123.22, 123.18, 120.57, 119.57, 112.60, 110.82, 63.72, 43.38, 30.77, 29.27, 21.54, 18.03; IR (KBr) ν_max: 3430, 3059, 2921, 2850, 2364, 1672, 1599, 1492, 1459, 1420, 1333, 1267, 1236, 1159, 1091, 925, 822, 746, 663, 576, 563, 544 cm⁻¹; HRMS (ESI): calcd for C₃₃H₃1N₃NaO₃S: [M + Na]⁺ 572.1978, found: 572.1961%.

4-Methyl-N-(2-((2-((2-oxopyrrolidin-1-yl)(phenyl)methyl)-1H-indol-3-yl)methyl)phenyl)benzenesulfonamide (3r). White solid (m.p. 97–98 °C), 83% yield (227.8 mg); ¹H NMR (400 MHz, CDCl₃) δ 8.35 (s, 1H), 7.45 (d, J = 7.5 Hz, 2H), 7.28–7.16 (m, 5H), 7.15–7.05 (m, 5H), 7.04–2.97 (m, 4H), 6.96–6.90 (m, 2H), 6.34 (s, 1H), 3.95 (d, J = 16.7 Hz, 1H), 3.76 (d, J = 16.7 Hz, 1H), 3.29–3.21 (m, 1H), 2.88–2.79 (m, 1H), 2.31 (s, 3H), 2.27–2.19 (m, 1H), 1.98–1.79 (m, 2H), 1.67–1.56 (s, 1H); ¹³C NMR (75 MHz, CDCl₃) δ 175.67, 143.46, 137.12, 136.60, 136.11, 135.41, 134.20, 132.55, 129.66, 129.55, 128.89, 128.06, 127.81, 127.23, 126.95, 126.65, 126.57, 125.93, 122.66, 120.03, 118.90, 112.51, 111.38, 51.76, 46.23, 30.81, 25.43, 21.58, 17.82; IR (KBr) ν_max: 3361, 3060, 2924, 2853, 1664, 1599, 1493, 1458, 1419, 1332, 1287, 1159k, 1091, 922, 815, 745, 662, 561, 496 cm⁻¹; HRMS (ESI): calcd for C₃₃H₃₁N₃NaO₃S: [M + Na]⁺ 572.1978, found: 572.1966%.

Acknowledgements

We gratefully acknowledge the Natural Science Foundation of China (no. 21172162), the Young National Natural Science Foundation of China (no. 21202111), the Young Natural Science Foundation of Jiangsu Province (BK2012174), PAPD, Key Laboratory of Organic Synthesis of Jiangsu Province (KJS1211), and Soochow University for financial support.

Notes and references

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Footnote

† Electronic supplementary information (ESI) available. CCDC 947549 and 947550. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3ra44196b

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