Bicyclization of isocyanides with alkenoyl bis(ketene dithioacetals): Access to 6,7-dihydro-1 h -indol-4(5 h)-ones

Article abstract of DOI:10.1021/jo500928c

The tandem [3 + 2] cycloaddition/intramolecular imidoyl anion trapping strategy has been successfully applied for the synthesis of 6,7-dihydro-1H- indol-4(5H)-ones from alkenoyl bis(ketene dithioacetals) and tosylmethyl isocyanide. The reaction proceeded smoothly under mild reaction conditions to afford bicyclization products in high to excellent yields in a single step.

Full text of DOI:10.1021/jo500928c

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Note
Bicyclization of Isocyanides with Alkenoyl Bis(ketene
dithioacetals): An Access to 6,7-Dihydro-1H-indol-4(5H)-ones
Yifei Li, Xianxiu Xu, Hui Shi, Ling Pan, and Qun Liu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo500928c • Publication Date (Web): 20 May 2014
Downloaded from http://pubs.acs.org on May 26, 2014
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Bicyclization of Isocyanides with Alkenoyl Bis(ketene dithioacetals): An
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Access to 6,7-Dihydro-1H-indol-4(5H)-ones
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Yifei Li, Xianxiu Xu,* Hui Shi, Ling Pan and Qun Liu*
Department of Chemistry, Northeast Normal University, Changchun, 130024, China
E-mail: xuxx677@nenu.edu.cn and liuqun@nenu.edu.cn
Abstract: The tandem [3+2] cycloaddition/intramolecular imidoyl anion trapping strategy has
been successfully applied for the synthesis of 6,7-dihydro-1H-indol-4(5H)-ones from alkenoyl
bis(ketene dithioacetals) and tosylmethyl isocyanide. The reaction proceeded smoothly under mild
reaction conditions to afford bicyclization products in high to excellent yields in a single step.
Functionalized ketene dithioacetals are versatile intermediates in organic synthesis.1,2 In our recent
research on the heterocyclization based on the reactions of -acidic isocyanides with
functionalized ketene dithioacetals leading to nitrogen heterocycles,1,3–5 we were able to show that
cyclopenta[b]pyrrole derivatives can be constructed from the reaction of alkenoyl ketene
dithioacetals with tosylmethyl isocyanide (TosMIC) under mild metal-free conditions in a single
run.5 In this reaction, the successful trapping of the incipient imidoyl anion species in-situ
generated from the [3+2] cycloaddition (Scheme 1, eq 1)5 as the key feature of the bicyclization
promoted us to further explore the bicyclization strategy. Herein, we describe the efficient
synthesis of 6,7-dihydro-1H-indol-4(5H)-ones from the bicyclization of alkenoyl
bis(ketene-dithioacetals) 3 with TosMIC (Scheme 1, eq 2).6
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Scheme 1. Imidoyl anion trapping strategy.
The present research started with the synthesis of bis(ketene-dithioacetals), for example 2a, as an
acyclic precursor for the bicyclization reaction.5 The literature search gave only a few relevant
references for the preparation of bis(ketene-dithioacetals) (Scheme 2)7 including, for example: 1)
first obtained by Krespan in 1961 from the reaction of sulfur and hexafluoro-2-butyne in the
o
presence of iodine at 200 C under pressure, suggested having a p-dithiinodihydro-p-dithiin
structure,7a later assigned as 2,2'-bi[2,4,5-tris(trifluoromethyl)-1,3-dithiole] A (obtained in 35%
yield by treating potassium sulfide with 2,3-dichlorohexafluoro-2-butene in purified DMF at 25 oC
for 6 days);7b 2) treatment of dimethyl acetylenedicarboxylate with carbon disulfide in a Carius
o
tube at 100 C for 18 h giving tetramethyl 2,2'-(1,4-dimethoxy-1,4-dioxobutane-2,3-diylidene)
bis(1,3-dithiole-4,5-dicarboxylate) B as a minor product in only 4.8% yield;7c and 3) bis(ketene-
dithioacetals) C and D by diazo transfer reaction of 2-(trimethylsilyl)-l,3-dithiane with tosyl azide
at -70 oC via probably a bisalkylthiocarbene intermediate.7d-f
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Scheme 2. Preparation of bis(ketene dithioacetals).
In our research it was found, after a series of tests, that bis(ketene-dithioacetal),
3,4-di(1,3-dithiolan-2-ylidene)hexane-2,5-dione 2a, could be readily prepared in 70% yield by
treatment of -acetyl ketene dithioacetal 1a (1.0 mmol) with ceric ammonium nitrate (CAN, 2.3
mmol)8 as the oxidant in methanol at 0 oC within 30 min (Scheme 2). The above result indicates
that a single-electron-transfer (SET) of 1a and subsequent homo-coupling process could be
accounted for the formation of bis(ketene-dithioacetal) 2a (Scheme 2)8 which provides an easy
access to bis(ketene-dithioacetals).7 Under similar reaction conditions, bis(ketene-dithioacetal) 2b
2,3-di(1,3-dithiolan-2-ylidene)-1,4-diphenylbutane-1,4-dione was obtained in 72% yield from
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2-(1,3-dithiolan-2-ylidene)-1-phenylethanone 1b (Scheme 2). However, a complicated mixture
was obtained from the reaction of 1-(1,3-dithian-2-ylidene)propan-2-one 1c, indicating a
significant effect of the alkylthio group of ketene dithioacetals on the reaction.1
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The condensation of bis(ketene dithioacetal) 2a with various aldehydes under basic conditions led
to the formation of either dialkenoyl bis(ketene-dithioacetals) 3a–g (Table 1, entry 1–7) or
mono-alkenoyl bis(ketene-dithioacetal)s 3h–j (Table 1, entry 8–10) in high to excellent yields.
Next, the reaction of 3a with TosMIC was examined to investigate the bicyclization of alkenoyl
bis(ketene-dithioacetals) for the synthesis of 6,7-dihydro-1H-indol-4(5H)-ones. Fortunately, the
desired 1H-indol-4(5H)-one 4a was prepared in 76% yield by treating the reaction mixture of 3a
(247 mg, 0.5 mmol) and TosMIC (117 mg, 0.6 mmol) with NaOH (22 mg, 0.55 mmol) in DMF at
room temperature for 6 h. Further optimization of reaction conditions showed that THF was more
suitable than DMF as solvent and the yield of 4a increased to 93% (Table 1, entry 11).
Under identical reaction conditions as above, the scope of this tandem [3+2]
cycloaddition/intramolecular imidoyl anion trapping reaction was investigated (Table 1, entries
11–20). The dialkenoyl bis(ketene-dithioacetals) 3a–g having phenyl (entry 11), electron-deficient
aryl (entry 12), electron-rich aryl (entries 13 and 14), 2-naphthyl (entry 15), heteroaryl (entry 16),
or alkyl group (entry 17) at the -position of the enone moiety afforded the corresponding
indol-4(5H)-ones 4a–g in high to excellent yields. In addition, the mono-alkenoyl
bis(ketene-dithioacetals) bearing an alkyl R2 group could also lead to the desired indol-4(5H)-ones
4h–j in high yields (entries 18–20).
Table 1. Synthesis of di-/mono-alkenoyl bis(ketene dithioacetals) 3 and indol-4(5H)-ones 4
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Yield of 3
Time Yield of 4
(h)
Entrya, b
R1
R2
Entryd
11
(%)c
(%)c
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3a (95)
3b (90)
3c (86)
3d (89)
3e (88)
3f (82)
3g (80)
3h (65)
Ph
PhCH=CH
6
4a (93)
4-ClC6H4
4-ClC6H4CH=CH
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4b (95)
4c (89)
4d (90)
4e (88)
4f (80)
4g (74)
4h (75)
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4-CH3OC6H4 4-CH3OC6H4CH=CH 8
4-CH3C6H4
2-naphthyl
2-furyl
4-CH3C6H4CH=CH
2-naphthylCH=CH
2-furylCH=CH
t-BuCH=CH
8
6
6
t-Bu
12
5
4-ClC6H4
Me
9
3i (60)
3j (63)
4-CH3OC6H4 Me
t-Bu Me
6
4i (70)
4j (65)
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20
10
12
aConditions for 3a–g (Entry 1–7): 2 (1.0 mmol), R1CHO (2.2 equiv) and NaOH (4.0 equiv) in
o
b
EtOH/CH2Cl2 (10:1, v/v, 25 mL) at 30 C for 12–18 h. Conditions for 3h–j (Entry 8–10): 2 (1.0
mmol), R1CHO (1.1 equiv) and NaOH (2.0 equiv) in H2O at 45 C for 12 h. Yield of isolated
o
c
d
products. Conditions: 3 (0.5 mmol), TosMIC (0.6 mmol, 1.2 equiv) and NaOH (0.55 mmol, 1.1
equiv) in THF (10 mL) at room temperature.
The successful synthesis of indol-4(5H)-ones 4 provides an efficient access to indole derivatives
in a single operation.6,9 Taken together, our previous5 and present results (Table 1), a plausible
mechanism for the formation of indol-4(5H)-ones 4 is proposed in Scheme 3. The overall process
involves (i) a formal [3+2] cycloaddition of the C=C double bond of alkenoyl moiety of
bis(ketene-dithioacetals) 3 with TosMIC under basic conditions to provide intermediate imidoyl
anion I;3 (ii) intramolecular trapping of the resulting anion I by the tethered terminal carbonyl
group (I→II) followed by elimination of tosylic acid (II→III);5 and finally (iii) spontaneous
aromatization of III to furnish indol-4(5H)-ones 4.10 Therefore, the key feature of this tandem
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process for the one-pot construction of 6,7-dihydro-1H-indol-4(5H)-ones 4 is the selective
intramolecular trapping of the incipient imidoyl anion species I by the electrophilic terminal
carbonyl carbon to form the six-membered ring.
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Scheme 3. Proposed mechanism for formation of indol-4(5H)-ones 4
In conclusion, we have described a simple oxidative dimmerization reaction of -acetal ketene
dithioacetal, which enables the direct synthesis of bis(ketene dithioacetal) as the precursor of
alkenoyl bis(ketene-dithioacetals) via a SET and subsequent homo-coupling process in the
presence of CAN as oxidant. The reaction of alkenoyl bis(ketene-dithioacetals) with TosMIC
provides a simple access to indole derivatives in a single operation under very mild reaction
conditions via a tandem [3+2] cycloaddition/intramolecular imidoyl anion trapping process. This
strategy provides an easy access to pyrrole-fused heterocycles from readily available acyclic
precursors in a single operation.
Experimental Section
General information
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All reagents were commercial and used without further purification, unless otherwise indicated.
Chromatography was carried on flash silica gel (300−400 mesh). All reactions were monitored by
TLC, which was performed on precoated aluminum sheets of silica gel 60 (F254). Melting points
were uncorrected. The 1H NMR and 13C NMR spectra were determined at 500 MHz and 125 MHz
(TMS as internal standard), respectively. High-resolutionmass spectra (HRMS) were obtained
using a micro TOF spectrometer (ESI).
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General procedure for the synthesis of 2: To the solution of 1 (160mg, 1.0 mmol) in MeOH (25
mL) was added ceric ammonium nitrate (CAN) (1261 mg, 2.3 mmol) at 0 ºC. The reaction
mixture was stirred at this temperature until the substrate 1 was consumed as indicated by TLC.
The resulting mixture was then poured into brine (30 mL) and extracted with dichloromethane (15
mL × 3). The combined organic phase was washed with water (15 mL ×3), dried over anhydrous
MgSO4 and concentrated in vacuum. The crude product was purified by flash chromatography on
silica gel (petroleum ether /EtOAc = 2 : 1) to give 2 as a yellow solid.
2a, 3,4-Di(1,3-dithiolan-2-ylidene)hexane-2,5-dione. Yellowish solid (111 mg, 70% yield), mp.
1
149–151 ºC. H NMR (CDCl3, 500 MHz) 2.12 (s, 6H), 3.29–3.32 (m, 4H), 3.50–3.54 (m, 4H).
13C NMR (CDCl3, 125 MHz) 27.1, 35.3, 40.1, 124.0, 168.2, 193.4. HRMS (ESI-TOF) Calcd for
C12H15O2S4+ ([M+H] +) 318.9949. Found 318.9956.
2b, 2,3-Di(1,3-dithiolan-2-ylidene)-1,4-diphenylbutane-1,4-dione. The reaction was performed at
1
room temperature. Yellowish solid (159 mg, 72% yield), mp. 194–196 ºC. H NMR (CDCl3, 500
MHz) 3.35 (d, J = 7.5 Hz, 4H), 3.52 (t, J = 8.0 Hz, 4H), 7.15–7.20 (m, 2H), 7.29–7.34 (m, 8H).
13C NMR (CDCl3, 125 MHz) 35.4, 40.1, 124.1, 127.5, 130.4, 139.5, 171.5, 189.3. HRMS
+
(ESI-TOF) Calcd for C22H19O2S4 ([M+H] +) 443.0262. Found 443.0258.
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General procedure for the synthesis of dialkenoyl bisketene dithioacetals 3a-g (taking 3a as an
example): To the mixture of 2a (318 mg, 1.0 mmol) and benzaldehyde (0.224 mL, 2.2 mmol) in
EtOH/CH2Cl2 (10 : 1, v/v, 25 mL) was added NaOH (160 mg, 4.0 mmol). The reaction mixture was
stirred at 30 ºC until the substrate 2a was consumed as indicated by TLC. The resulting mixture was
then poured into brine (30 mL) and extracted with dichloromethane (15 mL × 3). The combined
organic phase was washed with water (15 mL ×3), dried over anhydrous MgSO4 and concentrated in
vacuum. The crude product was purified by flash chromatography on silica gel (petroleum ether
/EtOAc = 2 : 1) to give 3a (470 mg, 95%) as a yellow solid.
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3a, (1E,7E)-4,5-Di(1,3-dithiolan-2-ylidene)-1,8-diphenylocta-1,7-diene-3,6-dione. Yellow solid
1
(470 mg, 95% yield), mp. 125–127 ºC. H NMR (CDCl3, 500 MHz) 3.29–3.32 (m, 4H), 3.55–
3.58 (m, 4H), 6.87 (d, J = 15.5 Hz, 2H), 7.31–7.32 (m, 6H), 7.45–7.47 (m, 4H), 7.78 (d, J = 15.5
Hz, 2H). 13C NMR (CDCl3, 125 MHz) 35.5, 40.2, 122.0, 123.7, 128.4, 128.7, 130.0, 135.2,
+
+
143.6, 170.8, 184.2. HRMS (ESI-TOF) Calcd for C26H23O2S4 ([M+H] ) 495.0575. Found
495.0578.
3b,
(1E,7E)-1,8-Bis(4-chlorophenyl)-4,5-di(1,3-dithiolan-2-ylidene)octa-1,7-diene-3,6-dione.
1
Yellow solid (507 mg, 90% yield), mp. 133–135 ºC. H NMR (CDCl3, 500 MHz)  3.33 (d, J =
5.0 Hz, 4H), 3.57 (d, J = 6.0 Hz, 4H), 6.81 (d, J = 15.5 Hz, 2H), 7.28 (d, J = 8.5 Hz, 4H), 7.38 (d,
J = 8.5 Hz, 4H), 7.71 (d, J = 15.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz) 35.6, 40.2, 122.4, 123.4,
+
128.9, 129.5, 133.6, 135.9, 142.2, 171.4, 183.9. HRMS (ESI-TOF) Calcd for C26H21Cl2O2S4
([M+H] +) 562.9796. Found 562.9785.
3c, (1E,7E)-4,5-Di(1,3-dithiolan-2-ylidene)-1,8-bis(4-methoxyphenyl)octa-1,7-diene-3,6-dione.
Yellow solid (477 mg, 86% yield), mp. 136–138 ºC. 1H NMR (CDCl3, 500 MHz)  3.28–3.31 (m,
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4H), 3.53–3.56 (m, 4H), 3.80 (s, 6H), 6.75 (d, J = 15.5 Hz, 2H), 6.83 (d, J = 8.5 Hz, 4H), 7.42 (d,
J = 8.5 Hz, 4H), 7.75 (d, J = 15.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz)35.5, 40.1, 55.3, 114.1,
8
9
+
119.8, 123.9, 127.9, 130.1, 143.4, 161.2, 169.8, 184.3. HRMS (ESI-TOF) Calcd for C28H27O4S4
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([M+H] +) 555.0787. Found 555.0787.
3d, (1E,7E)-4,5-Di(1,3-dithiolan-2-ylidene)-1,8-di-p-tolylocta-1,7-diene-3,6-dione. Yellow solid
(465 mg, 89% yield), mp. 122–124 ºC. 1H NMR (CDCl3, 500 MHz) 2.32 (s, 6H), 3.28–3.30 (m,
4H), 3.54–3.57 (m, 4H), 6.83 (d, J = 15.5 Hz, 2H), 7.11 (d, J = 8.0 Hz, 4H), 7.36 (d, J = 8.0 Hz,
4H), 7.76 (d, J = 15.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz)  21.5, 35.5, 40.2, 121.1, 123.9,
128.4, 129.4, 132.5, 140.5, 143.7, 170.3, 184.4. HRMS (ESI-TOF) Calcd for C28H27O2S4+ ([M+H]
+) 523.0888. Found 523.0896.
3e,
(1E,7E)-4,5-Di(1,3-dithiolan-2-ylidene)-1,8-di(naphthalen-2-yl)octa-1,7-diene-3,6-dione.
Yellow solid (523 mg, 88% yield), mp. 137–139 ºC. 1H NMR (CDCl3, 500 MHz) 3.31–3.34 (m,
4H), 3.58–3.60 (m, 4H), 7.01 (d, J = 15.5 Hz, 2H), 7.46 (dd, J = 7.0, 4.0 Hz, 4H), 7.58 (dd, J = 8.5,
1.5 Hz, 2H), 7.74 (d, J = 8.5 Hz, 2H), 7.76–7.78 (m, 2H), 7.81–7.83 (m, 2H), 7.90 (s, 2H), 7.97 (d,
J = 15.5 Hz, 2H). 13C NMR (CDCl3, 125 MHz)  35.6, 40.2, 122.2, 123.8, 123.9, 126.5, 127.0,
127.7, 128.4, 128.5, 130.3, 132.7, 133.2, 134.1, 143.8, 171.0, 184.2. HRMS (ESI-TOF) Calcd for
C34H27O2S4+ ([M+H] +) 595.0888. Found 595.0896.
3f, (1E,7E)-4,5-Di(1,3-dithiolan-2-ylidene)-1,8-di(furan-2-yl)octa-1,7-diene-3,6-dione. Yellow
1
solid (389 mg, 82% yield), mp. 135–137 ºC. H NMR (CDCl3, 500 MHz)  3.29–3.31 (m, 4H),
3.54–3.56 (m, 4H), 6.41 (dd, J = 3.5, 2.0 Hz, 2H), 6.73 (d, J = 15.5 Hz, 2H), 7.40 (d, J = 1.0 Hz,
2H), 7.51 (d, J = 15.0 Hz, 2H). 13C NMR (CDCl3, 125 MHz)  35.5, 40.2, 112.3, 115.4, 119.9,
123.8, 129.7, 144.4, 152.0, 170.4, 184.0. HRMS (ESI-TOF) Calcd for C22H19O4S4 ([M+H] +)
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475.0161. Found 475.0163.
3g, (3E,9E)-6,7-Di(1,3-dithiolan-2-ylidene)-2,2,11,11-tetramethyldodeca-3,9-diene-5,8-dione.
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Yellow solid (363 mg, 80% yield), mp. 140–142 ºC. 1H NMR (CDCl3, 500 MHz)  0.99 (s, 18H),
3.26–3.30 (m, 4H), 3.48–3.52 (m, 4H), 6.10 (d, J = 15.5 Hz, 2H), 6.97 (d, J = 15.5 Hz, 2H). 13C
NMR (CDCl3, 125 MHz) 28.7, 33.7, 35.4, 40.0, 120.7, 123.5, 157.7, 169.3, 185.1. HRMS
(ESI-TOF) Calcd for C22H31O2S4+ ([M+H] +) 455.1201. Found 455.1207.
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General procedure for the synthesis of mono-alkenoyl bisketene dithioacetals 3h-j (taking 3h
as an example): To the mixture of 2a (318 mg, 1.0 mmol) and 4-chlorobenzaldehyde (154 mg, 1.1
mmol) in H2O (25 mL) was added NaOH ( 80 mg, 2.0 mmol). The reaction mixture was stirred at
45 ºC until the substrate 2a was consumed as indicated by TLC. The resulting mixture was then
poured into brine (30 mL) and extracted with dichloromethane (15 mL × 3). The combined organic
phase was washed with water (15 mL ×3), dried over anhydrous MgSO4 and concentrated in
vacuum. The crude product was purified by flash chromatography on silica gel (petroleum ether
/EtOAc = 2 : 1) to give 3h (285 mg, 65%) as a yellow solid.
3h, (E)-7-(4-Chlorophenyl)-3,4-di(1,3-dithiolan-2-ylidene)hept-6-ene-2,5-dione. Yellow solid
(285 mg, 65% yield), mp. 120–122 ºC. 1H NMR (CDCl3, 500 MHz) 2.11 (s, 3H), 3.26–3.34 (m,
4H), 3.50–3.57 (m, 4H), 6.79 (d, J = 16.0 Hz, 1H), 7.31 (d, J = 8.5 Hz, 2H), 7.41 (d, J = 8.5 Hz,
2H), 7.71 (d, J = 15.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz) 27.4, 35.4, 35.4, 40.1, 40.1, 122.0,
122.8, 124.3, 128.9, 129.4, 133.4, 135.8, 142.1, 170.7, 183.5, 193.6. HRMS (ESI-TOF) Calcd for
C19H18ClO2S4+ ([M+H] +) 440.9873. Found 440.9868.
3i, (E)-3,4-Di(1,3-dithiolan-2-ylidene)-7-(4-methoxyphenyl)hept-6-ene-2,5-dione. Yellow solid
(262 mg, 60% yield), mp. 118–120 ºC. 1H NMR (CDCl3, 500 MHz) 2.12 (s, 3H), 3.27–3.34 (m,
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4H), 3.50–3.55 (m, 4H), 3.83 (s, 3H), 6.72 (d, J = 15.5 Hz, 1H), 6.87 (d, J = 8.5 Hz, 2H), 7.45 (d,
J = 9.0 Hz, 2H), 7.76 (d, J = 15.5 Hz, 1H). 13C NMR (CDCl3, 125 MHz)  27.4, 35.3, 35.4, 40.1,
40.1, 55.3, 114.2, 119.3, 123.2, 124.7, 127.8, 130.1, 143.6, 161.3, 168.4, 169.3, 184.0, 193.8.
HRMS (ESI-TOF) Calcd for C20H21O3S4+ ([M+H] +) 437.0368. Found 437.0371.
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3j, (E)-3,4-Di(1,3-dithiolan-2-ylidene)-8,8-dimethylnon-6-ene-2,5-dione. Yellow solid (243 mg,
63% yield), mp. 125–127 ºC. 1H NMR (CDCl3, 500 MHz) 1.00 (s, 9H), 2.06 (s, 3H), 3.25–3.29
(m, 4H), 3.47–3.52 (m, 4H), 6.11 (d, J = 15.5 Hz, 1H), 7.00 (d, J = 15.5 Hz, 1H). 13C NMR
(CDCl3, 125 MHz)  27.2, 28.7, 33.7, 35.2, 35.4, 40.0, 120.1, 123.0, 124.2, 158.2, 168.0, 169.2,
184.7, 193.5. HRMS (ESI-TOF) Calcd for C17H23O2S4+ ([M+H] +) 387.0575. Found 387.0565.
General procedure for the synthesis of indol-4(5H)-ones 4 (taking 4a as an example): To the
mixture of 3a (247 mg, 0.5 mmol) and TosMIC (117 mg, 0.6 mmol) in THF (10 mL) was added
NaOH (22 mg, 0.55 mmol). The reaction mixture was stirred at room temperature until the
substrate 3a was consumed as indicated by TLC. The resulting mixture was then poured into brine
(30 mL) and extracted with dichloromethane (15 mL × 3). The combined organic phase was
washed with water (15 mL ×3), dried over anhydrous MgSO4 and concentrated in vacuum. The
crude product was purified by flash chromatography on silica gel (petroleum ether /EtOAc = 3 : 1)
to give 4a (248 mg, 93%) as a yellow solid.
4a, (E)-5,6-Di(1,3-dithiolan-2-ylidene)-7-hydroxy-3-phenyl-7-styryl-6,7-dihydro-1H-indol-4(5H)-
1
one. Yellow solid (248 mg, 93% yield), mp. 160–162 ºC. H NMR (CDCl3, 500 MHz) 3.06–
3.15 (m, 2H), 3.18–3.26 (m, 2H), 3.27 (s, 1H), 3.29–3.37 (m, 2H), 3.38–3.42 (m, 2H), 6.32 (d, J =
16.0 Hz, 1H), 6.40 (d, J = 16.0 Hz, 1H), 6.77 (d, J = 2.0 Hz, 1H), 7.19 (t, J = 7.0 Hz, 1H), 7.23–
7.30 (m, 5H), 7.34 (t, J = 8.0 Hz, 2H), 7.67 (d, J = 8.0 Hz, 2H), 8.95 (s, 1H) . 13C NMR (CDCl3,
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125 MHz) 35.5, 35.9, 38.6, 39.4, 77.6, 116.9, 118.7, 125.2, 125.4, 126.5, 126.7, 126.8, 127.7,
127.9, 128.4, 128.5, 128.7, 129.1, 134.0, 135.6, 136.4, 143.1, 158.3, 181.1. HRMS (ESI-TOF)
Calcd for C28H24NO2S4+ ([M+H] +) 534.0684. Found 534.0687.
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4b,
(E)-3-(4-Chlorophenyl)-7-(4-chlorostyryl)-5,6-di(1,3-dithiolan-2-ylidene)-7-hydroxy-6,7-
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dihydro-1H-indol-4(5H)-one. Yellow solid (286 mg, 95%), mp. 170–172 ºC. H NMR (CDCl3,
500 MHz)3.07–3.19 (m, 2H), 3.21 (s, 1H), 3.22–3.47 (m, 6H), 6.26 (d, J = 15.5 Hz, 1H), 6.32
(d, J = 16.0 Hz, 1H), 6.76 (d, J = 2.5 Hz, 1H), 7.20 (dd, J = 14.0, 8.5 Hz, 4H), 7.30–7.31 (m, 2H),
7.60–7.61 (m, 2H), 8.91 (s, 1H) . 13C NMR (CDCl3, 125 MHz)  35.6, 36.0, 38.7, 39.4, 77.5,
116.9, 118.7, 124.2, 125.1, 126.3, 127.9, 128.0, 128.1, 128.6, 129.0, 129.9, 132.4, 132.4, 133.4,
+
+
134.9, 136.0, 143.1, 158.9, 181.0. HRMS (ESI-TOF) Calcd for C28H22Cl2NO2S4 ([M+H] )
601.9905. Found 601.9911.
4c,
(E)-5,6-Di(1,3-dithiolan-2-ylidene)-7-hydroxy-3-(4-methoxyphenyl)-7-(4-methoxystyryl)-
6,7-dihydro-1H-indol-4(5H)-one. Yellow solid (264 mg, 89%), mp. 197–199 ºC. 1H NMR (CDCl3,
500 MHz) 3.05–3.25 (m, 4H), 3.27–3.36 (m, 5H), 3.77 (s, 3H), 3.80 (s, 3H), 6.20 (d, J = 16.0 Hz,
1H), 6.33 (d, J = 15.5 Hz, 1H), 6.73 (d, J = 2.5 Hz, 1H), 6.77 (d, J = 9.0 Hz, 2H), 6.89 (d, J = 9.0
Hz, 2H), 7.20 (d, J = 9.0 Hz, 2H), 7.61 (d, J = 9.0 Hz, 2H), 8.91 (s, 1H) . 13C NMR (CDCl3, 125
MHz) 35.5, 35.9, 38.6, 39.4, 55.2, 55.2, 77.7, 113.4, 113.8, 116.8, 117.9, 125.0, 125.6, 126.6,
127.1, 128.0, 128.8, 129.2, 129.8, 135.3, 143.1, 157.9, 158.4, 159.3, 181.1. HRMS (ESI-TOF)
Calcd for C30H28NO4S4+ ([M+H] +) 594.0896. Found 594.0878.
4d, (E)-5,6-Di(1,3-dithiolan-2-ylidene)-7-hydroxy-7-(4-methylstyryl)-3-(p-tolyl)-6,7-dihydro-1H-
1
indol-4(5H)-one. Yellow solid (253 mg, 90%), mp. 166–168 ºC. H NMR (CDCl3, 500 MHz)
2.29 (s, 3H), 3.33 (s, 3H), 3.04–3.20 (m, 4H), 3.25 (s, 1H), 3.33–3.40 (m, 4H), 6.26 (d, J = 15.5
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Hz, 1H), 6.34 (d, J = 15.5 Hz, 1H), 6.71 (s, 1H), 7.04 (d, J = 8.0 Hz, 2H), 7.15 (t, J = 8.0 Hz, 4H),
7.55 (d, J = 7.5 Hz, 2H), 8.99 (s, 1H) . 13C NMR (CDCl3, 125 MHz) 21.2, 35.5, 35.8, 38.6, 39.4,
77.6, 116.9, 118.5, 125.1, 125.6, 126.7, 127.0, 127.6, 128.6, 128.7, 129.1, 131.1, 133.6, 135.4,
136.1, 137.5, 143.1, 158.0, 181.2. HRMS (ESI-TOF) Calcd for C30H28NO2S4+ ([M+H] +) 562.0997.
Found 562.0989.
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4e,
(E)-5,6-Di(1,3-dithiolan-2-ylidene)-7-hydroxy-3-(naphthalen-2-yl)-7-(2-(naphthalen-2-yl)
1
vinyl)-6,7-dihydro-1H-indol-4(5H)-one. Yellow solid (279 mg, 88%), mp. 148–150 ºC. H NMR
(CDCl3, 500 MHz) 2.96–3.05 (m, 2H), 3.15–3.24 (m, 3H), 3.27–3.34 (m, 2H), 3.37–3.41 (m,
2H), 6.44 (d, J = 15.5 Hz, 1H), 6.49 (d, J = 16.0 Hz, 1H), 6.74 (d, J = 2.5 Hz, 1H), 7.38–7.40 (m,
4H), 7.41–7.46 (m, 1H), 7.60 (s, 1H), 7.66–7.78 (m, 6H), 7.79–7.83 (m, 1H), 8.07 (s, 1H), 9.14 (s,
1H). 13C NMR (CDCl3, 125 MHz) 35.6, 35.8, 38.6, 39.4, 77.7, 117.2, 119.3, 123.8, 125.1, 125.2,
125.5, 125.6, 125.9, 126.2, 126.6, 126.8, 127.0, 127.2, 127.5, 127.6, 127.8, 128.0, 128.1, 128.9,
129.3, 131.7, 132.4, 132.9, 133.4, 133.5, 133.9, 135.7, 143.3, 158.4, 181.3. HRMS (ESI-TOF)
Calcd for C36H28NO2S4+ ([M+H] +) 634.0997. Found 634.1017.
4f,
(E)-5,6-Di(1,3-dithiolan-2-ylidene)-3-(furan-2-yl)-7-(2-(furan-2-yl)vinyl)-7-hydroxy-6,7-
1
dihydro-1H-indol-4(5H)-one. Yellow solid (205 mg, 80%), mp. 155–157 ºC. H NMR (CDCl3,
500 MHz)  3.14–3.24 (m, 5H), 3.31–3.34 (m, 2H), 3.41–3.44 (m, 2H), 6.17 (d, J = 3.0 Hz,
1H), 6.26(d, J = 8.5 Hz, 2H), 6.31 (dd, J = 3.5, 1.5 Hz, 1H), 6.43 (dd, J = 3.5, 2.0 Hz, 1H), 7.12 (d,
J = 2.0 Hz, 1H), 7.29 (d, J = 1.5 Hz, 1H), 7.32 (d, J = 1.0 Hz, 1H), 7.51 (d, J = 3.5 Hz, 1H), 8.74
(s, 1H) . 13C NMR (CDCl3, 125 MHz) 35.6, 36.0, 38.5, 39.4, 77.3, 108.8, 109.0, 111.2, 111.5,
115.3, 115.8, 117.9, 125.4, 126.1, 126.9, 136.2, 140.3, 142.2, 142.6, 149.0, 152.0, 158.1, 181.0.
HRMS (ESI-TOF) Calcd for C24H20NO4S4+ ([M+H] +) 514.0270. Found 514.0272.
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4g, (E)-3-(tert-Butyl)-7-(3,3-dimethylbut-1-en-1-yl)-5,6-di(1,3-dithiolan-2-ylidene)-7-hydroxy-6,7
6
7
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-dihydro-1H-indol-4(5H)-one. Yellow solid (183 mg, 74%), mp. 142–144 ºC. H NMR (CDCl3,
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500 MHz) 0.93 (s, 9H), 1.41 (s, 9H), 2.88 (s, 1H), 3.15–3.23 (m, 4H), 3.28–3.38 (m, 2H),
3.40–3.45 (m, 2H), 5.38 (d, J = 15.5 Hz, 1H), 5.56(d, J = 15.5 Hz, 1H), 6.51 (d, J = 2.0 Hz, 1H),
8.32 (s, 1H) . HRMS (ESI-TOF) Calcd for C24H32NO2S4+ ([M+H] +) 494.1310. Found 494.1317.
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4h,
3-(4-Chlorophenyl)-5,6-di(1,3-dithiolan-2-ylidene)-7-hydroxy-7-methyl-6,7-dihydro-1H
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-indol-4(5H)-one. Yellow solid (180 mg, 75%), mp. 157–159 ºC. H NMR (CDCl3, 500 MHz)
1.64 (s, 3H), 2.84 (s, 1H), 3.19–3.24 (m, 2H), 3.25–3.30 (m, 2H), 3.33–3.41 (m, 2H), 3.44–3.49
(m, 2H), 6.79 (d, J = 2.5 Hz, 1H), 7.30 (d, J = 8.5 Hz, 2H), 7.60 (d, J = 8.5 Hz, 2H), 8.66 (s, 1H) .
13C NMR (CDCl3, 125 MHz) 27.4, 35.5, 35.9, 38.8, 39.3, 75.3, 115.6, 118.2, 124.0, 125.9, 128.0,
128.7, 129.9, 132.2, 132.5, 134.2, 146.3, 157.9, 180.9. HRMS (ESI-TOF) Calcd for
C21H19ClNO2S4+ ([M+H] +) 479.9982. Found 479.9976.
4i,
5,6-Di(1,3-dithiolan-2-ylidene)-7-hydroxy-3-(4-methoxyphenyl)-7-methyl-6,7-dihydro-1H-
1
indol-4(5H)-one. Yellow solid (166 mg, 70%), mp. 155–157 ºC. H NMR (CDCl3, 500 MHz)
1.62 (d, J = 1.5 Hz, 3H), 2.96 (s, 1H), 3.14–3.23 (m, 2H), 3.24–3.29 (m, 2H), 3.34–3.41 (m, 2H),
3.42–3.50 (m, 2H), 3.80 (s, 3H), 6.70 (d, J = 2.5 Hz, 1H), 6.88 (d, J = 9.0 Hz, 2H), 7.58 (d, J = 9.0
Hz, 2H), 8.80 (s, 1H) . 13C NMR (CDCl3, 125 MHz) 27.4, 35.5, 35.9, 38.7, 39.3, 55.2, 75.3,
113.4, 115.6, 117.6, 124.8, 126.1, 126.6, 129.0, 133.9, 146.0, 157.2, 158.4, 181.0. HRMS
(ESI-TOF) Calcd for C22H22NO3S4+ ([M+H] +) 476.0477. Found 476.0492.
4j,
3-(tert-Butyl)-5,6-di(1,3-dithiolan-2-ylidene)-7-hydroxy-7-methyl-6,7-dihydro-1H-indol-
4(5H)-one. Yellow solid (138 mg, 65%), mp. 181–183 ºC. 1H NMR (CDCl3, 500 MHz) 1.39 (s,
9H), 1.59 (s, 3H), 3.02 (s, 1H), 3.10–3.14 (m, 1H), 3.17–3.21 (m, 1H), 3.24–3.29 (m, 3H), 3.35–
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3.40 (m, 2H), 3.45–3.49 (m, 1H), 6.49 (d, J = 2.0 Hz, 1H), 8.59 (s, 1H). 13C NMR (CDCl3, 125
MHz) 27.4, 30.1, 31.4, 35.5, 35.9, 38.6, 39.2, 75.3, 115.0, 116.4, 126.6, 129.2, 133.2, 135.3,
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+
+
146.7, 155.9, 180.7. HRMS (ESI-TOF) Calcd for C19H24NO2S4 ([M+H] ) 426.0684. Found
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ASSOCIATED CONTENT
Supporting Information
Copies of 1H and 13C NMR spectra for all new products. This material is available free of charge
via the Internet at http://pubs.acs.org.
Notes
The authors declare no competing financial interest.
■ ACKNOWLEDGMENTS
Financial supports of this research provided by the NNSFC (21172030, 21272034 and 21202015),
the Young Scientific Research Foundation of Jilin Province (20140520083JH) and the
Fundamental Research Funds for the Central Universities (12QNJJ010) are greatly acknowledged.
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A. de Meijere, Georg Thieme, Stuttgart, Vol. 24, 2014, pp 245−286.
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