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Article

Efficient Synthesis of Eight-Membered Cyclic Diaryl Sulfides via an Aryne Reaction with 2-Methylenebenzothiophene-3-Ones

by
Juhua Feng
*,†,
Wenjie Zou
†,
Haokun Zhang
,
Qilin Huang
,
Ailin Huang
,
Kuan Liu
and
Guizhou Yue
College of Science, Sichuan Agricultural University, Xinkang Road 46, Ya’an 625014, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Reactions 2025, 6(2), 35; https://doi.org/10.3390/reactions6020035
Submission received: 15 April 2025 / Revised: 20 May 2025 / Accepted: 28 May 2025 / Published: 30 May 2025
(This article belongs to the Special Issue Cycloaddition Reactions at the Beginning of the Third Millennium)
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Abstract

In this study, we develop a concise and efficient synthetic strategy for the construction of eight-membered cyclic diaryl sulfides by undertaking [3+2] cycloaddition, 1,2-hydrogen shift, and C(sp2)-S bond cleavage steps on 2-methylenebenzothiophene-3-ones with aryne, using TBAT as the fluorine source. This transformation proceeds well under mild conditions and affords the target products in high to excellent yields (up to 93% yields). The process provides a practical route to achieving sulfur-containing medium-sized heterocycles.

1. Introduction

Sulfur-containing heterocycles are prominent structural motifs, which constitute the core structure of a significant number of natural products [1,2,3,4,5], pharmaceuticals [6,7,8,9,10,11], functional materials [12,13,14,15,16,17], and active biological molecules [18,19,20,21,22]. For instance, as shown in Scheme 1, diltiazem (calcium channel blocker) is used in the treatment of hypertension and angina [23,24]. Raloxifene is a widely recognized therapeutic agent for the treatment of osteoporosis [25]; Zaltoprofen is a non-steroidal anti-inflammatory drug [26,27,28]; and DNTT is a well-known organic thin-film transistor [29,30]. Additionally, thiolactomycin exhibits interesting antibacterial activity [31,32,33]. Compound A was found to be an effective inhibitor of stomach secretion [34], compound B showed anti-tumor activity [35], and compound C exhibited anti-ischemic activity [36]. As a result, many efforts have been devoted to the construction of sulfur-containing heterocycles [37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52]. Notably, there has been far less research focused on efficient methods for the synthesis of sulfur-containing benzo-fused eight-membered heterocycles. Likely due to unfavorable entropic and enthalpic constraints [53,54], the construction of these eight-membered heterocycles is a challenge.
A survey of the relevant literature revealed that only several very limited examples have been reported. In 1987, Hellwinkel reported the connection of the head and tail of a sulfide using Dieckmann cyclization for the synthesis of benzo-fused eight-membered cyclic sulfides [55]. Biehl reported the synthesis of benzene-fused eight-membered rings containing nitrogen and sulfur via a benzyne ring closure reaction [56]. Foubelo reported the cyclisation of sulfanyl alcohol under acidic conditions to yield the eight-membered sulfur-containing heterocycle [57]. Jiang reported straightforward protocols for diarylannulated sulfide construction through S-I exchange [58,59]. Asai reported using the thio-alkylation of thiosalicylic acid and then intramolecular Friedel–Crafts acylation to synthesize diaryl sulfide [60]. In 2019, Chen’s and Meng’s groups reported the construction of benzo-fused eight-membered cyclic sulfides via the domino reaction of arynes and methylenebenzothiopheneones with CsF as the fluorine source [61,62]. When unsubstituted methylenebenzothiopheneone reacted with an unsubstituted aryne precursor, only a 31% yield was obtained. In other cases, there is no substrate scope of the reaction with 2-(trimethylsilyl)phenyl trifluoromethanesulfonate as the benzyne precursor. Reddy reported using copper (I)-catalyzed interrupted click-sulfenylation of O-/N-propargyl benzyl thiosulfonates with organic azides to construct triazole-fused eight-membered heterocycles [63]. Despite some efforts made in the past, the synthetic chemistry of sulfur-containing benzo-fused eight-membered heterocycles still suffers from considerable limitations, such as low yields and narrow substrate scope.
Considering the importance of eight-membered cyclic diaryl sulfides, we here report undertaking the [3+2] cycloaddition, 1,2-hydrogen shift and C(sp2)-S bond cleavage of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and 2-methylenebenzothiophene-3-ones with TBAT as fluorine source for the preparation of eight-membered cyclic diaryl sulfides.

2. Results and Discussion

In our initial attempts, we commenced with the reaction of 2-methylenebenzothiophene-3-one (1a) and 2-(trimethylsilyl)phenyl trifluoromethanesulfonate (unsubstituted aryne precursor) (2) for the exploration of the optimal reaction conditions. As shown in Table 1, first, the reaction was conducted with CsF as the fluorine source in ethyl acetate at 30 °C. Regrettably, only a trace amount of the anticipated product (3a) was obtained (Table 1, entry 1). Various solvents were screened (Table 1, entries 2–7). Similarly, only a trace amount of desired product (3a) was generated with THF, CH2Cl2, and EtOH (Table 1, entries 2–4). When the solvent was toluene, the desired product (3a) was not obtained (Table 1, entry 5). Fortunately, a significant improvement was noted when acetone was used as the solvent, resulting in 33% yield of the product (Table 1, entry 6). Further experimentation revealed that CH3CN was an optimal solvent, affording a 52% yield (Table 1, entry 7). Subsequently, the screening of different fluorine sources for the reaction was carried out. A yield of only 16% was generated when using KF as fluorine source (Table 1, entry 8). When using NaF or TBAF, trace amounts of the desired product (3a) were obtained (Table 1, entries 9 and 10). Gratifyingly, when TBAT was employed as the fluorine source, a remarkable 92% yield of product 3a was achieved (Table 1, entry 11). The effect of the additive 18-crown-6 was also evaluated, and the yield of 3a was substantially reduced to 73% (Table 1, entry 12). Then, further evaluations of the effect of temperature revealed that, when the reaction was carried out at 60 °C, no distinct change was detected (91% yield, Table 1, entry 15). At other temperatures, the reaction decreased yields (77% and 84% yields, Table 1, entries 13 and 14). Finally, the equivalent of TBAT was screened. Further increases in the equivalence of TBAT and 2 did not improve the yield of 3a (Table 1, entries 16 and 17).
Thus, the optimal reaction conditions were found to be 1.0 equiv. of 2-methylenebenzothiophene-3-one 1a, 2.0 equiv. of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate 2, and 2.0 equiv. of TBAT in 0.5 mL of CH3CN at 30 °C for 4 h.
With the optimal reaction conditions established, we further explored the substrate range of 2-methylenebenzothiophene-3-ones 1 (Scheme 2). First, we investigated the substrates with R2 = CO2Et. When the methyl group was substituted at the C5 or C6 positions, the corresponding products 3b and 3c were obtained in 85% and 87% yields, respectively. Product 3d was obtained in 93% yield when the methyl substitution was located at the C7 position. Next, when the R2 group of substrate 1 was changed from CO2Et to CO2Me, substrates that had a C5-, C6-, or C7-substituent phenyl ring with a methyl group were also subjected to general reaction conditions, producing the compounds 3e–3h in excellent yields (91–92% yields). When the ester moiety of substrate 1 changes to sterically hindered CO2tBu, the reaction of the substrate-bearing methyl group at the C5–C7 positions of the phenyl ring resulted in 80–84% yields of products 3i–3l. In addition, substrates with benzyl on the ester moiety were well tolerated and afforded products 3m–3p in high yields (70–78% yields). Unfortunately, when the substituents on the benzene ring were electron-withdrawing groups (Cl or Br), the desired products could not be generated.
Furthermore, to demonstrate the applicability of this reaction, we carried out a gram-scale experiment under optimized conditions. As shown in Scheme 3, when using 4.0 mmol (0.99 g) of methylenebenzothiophene-one 1d for cycloaddition, the reaction still proceeded well, producing 3d with a yield of 81% (1.05 g).

3. Conclusions

In summary, a variety of eight-membered cyclic diaryl sulfides were effectively synthesized. Utilizing TBAT as the fluorine source, the [3+2] cycloaddition of 2-methylenebenzothiophene-3-ones with aryne, following a 1,2-hydrogen shift and C-S bond cleavage, proceeded smoothly to afford the target products in high to excellent yields (70–93% yields). The reaction could be conducted on a gram scale. Our laboratory is undertaking further investigations of the potential of using arynes to construct sulfur-containing heterocycles.

4. Materials and Methods

The 1H and 13C NMR spectra of all compounds were recorded on a Bruker 400 advance III spectrometer (1H = 400 MHz and 13C = 101 MHz) (Bruker corporation) at room temperature (25 °C) using CDCl3 (Adamas-Beta, Shanghai, China) as the solvent. The processing of NMR spectra was performed using MestReNova Software (version 14.2.1-27684; Mestrelab Research, 2021). The chemical shifts were recorded in ppm relative to tetramethylsilane and with the solvent resonance as the internal standard. Data were reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, m = multiplet, br = broad), coupling constants (Hz), and integration. The melting points were determined using Melting-Point Apparatus (HUAZHI HMX-1B, Fujian, China). HRMS data were acquired using a Thermo Scientific Q Exactive Plus Quadrupole-Orbitrap mass spectrometer (Thermo Fisher Scientific, Bremen, Germany) equipped with a Heated Electrospray Ionization (HESI) source. Flash chromatography was performed using silica gel (Qingdao Haiyang chemical corporation, Qingdao, China). Thin-layer chromatography (TLC): Huanghai HSGF254, Yantai, China. 1H and 13C-NMR spectra of compounds 3a–3p are in Supplementary Materials.
General procedure for the synthesis of 3:
In a test tube, 2 (0.40 mmol) was added to a solution of 1 (0.20 mmol) and TBAT (0.40 mmol) in CH3CN (2.0 mL). The mixture was stirred at 30 °C for 4 h. After the reaction was complete (monitored by TLC), the solvent was removed under reduced pressure, and the residue was purified via column chromatography to afford the pure product 3 (ethyl acetate: petroleum ether = 1:20).
Ethyl (E)-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3a):
Yellow solid (57.2 mg, 92% yield), mp 134–136 °C, Rf = 0.68 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.82–7.73 (m, 1H), 7.71–7.61 (m, 2H), 7.56–7.36 (m, 4H), 7.34–7.25 (m, 2H), 4.37–4.26 (m, 2H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 195.93, 165.17, 140.96, 140.81, 139.57, 136.48, 136.41, 135.96, 132.76, 132.58, 131.99, 131.57, 130.08, 129.84, 129.58, 127.51, 61.87, 14.21. HRMS (ESI): m/z calcd for C18H14O3S [M + H]+: 311.0736, found: 311.0736.
Ethyl (E)-3-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3b):
Yellow solid (55.2 mg, 85% yield), mp 134–135 °C, Rf = 0.64 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.76–7.62 (m, 2H), 7.58–7.46 (m, 2H), 7.44–7.37 (m, 2H), 7.29–7.24 (m, 1H), 7.29–7.24 (m, 1H), 4.36–4.27 (m, 2H), 2.39 (s, 3H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 195.32, 165.30, 143.98, 140.96, 140.68, 139.72, 136.30, 135.45, 134.05, 132.89, 132.67, 131.74, 129.95, 129.87, 129.48, 128.51, 61.83, 21.37, 14.22. HRMS (ESI): m/z calcd for C19H16O3S [M + H]+: 325.0893, found: 325.0894.
Ethyl (E)-2-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3c):
Yellow solid (56.5 mg, 87% yield), Rf = 0.64 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.72–7.52 (m, 2H), 7.50–7.38 (m, 2H), 7.37–7.25 (m, 2H), 7.21–7.15 (m, 1H), 7.08–7.00 (m, 1H), 4.30–4.16 (m, 2H), 2.31 (s, 3H), 1.25 (t, J = 7.1 Hz, 3H). HRMS (ESI): m/z calcd for C19H16O3S [M + H]+: 325.0893, found: 325.0892.
Ethyl (E)-1-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3d):
Yellow solid (60.3 mg, 93% yield), mp 143–144 °C, Rf = 0.64 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, Chloroform-d) δ 7.66–7.59 (m 1H), 7.58–7.48 (m, 2H), 7.46–7.33 (m, 3H), 7.28–7.23 (m, 1H), 7.18 (t, J = 7.6 Hz, 1H), 4.38–4.26 (m, 2H), 2.61 (s, 3H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 196.72, 165.06, 141.78, 140.77, 140.20, 138.46, 137.13, 136.85, 136.20, 134.14, 132.35, 130.17, 129.68, 129.57, 129.34, 126.49, 61.79, 21.47, 14.24. HRMS (ESI): m/z calcd for C19H16O3S [M + H]+: 325.0893, found: 325.0893.
Methyl (E)-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3e):
Light yellow solid (53.7 mg, 91% yield), mp 146–147 °C, Rf = 0.66 (Ethyl acetate: Petroleum ether = 1:5)). 1H NMR (400 MHz, CDCl3) δ 7.79–7.72 (m, 1H), 7.71–7.65 (m, 2H), 7.50 (d, J = 7.7 Hz, 1H), 7.46–7.40 (m, 3H), 7.34–7.26 (m, 2H), 3.86 (s, 3H). HRMS (ESI): m/z calcd for C17H12O3S [M + H]+: 297.0580, found: 297.0584.
Methyl (E)-3-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3f):
Light yellow solid (57.1 mg, 92% yield), mp 159–161 °C, Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5)). 1H NMR (400 MHz, CDCl3) δ 7.73–7.65 (m, 1H), 7.63–7.52 (m, 2H), 7.51–7.34 (m, 3H), 7.30–7.24 (m, 2H), 3.85 (s, 3H), 2.33 (s, 3H). HRMS (ESI): m/z calcd for C18H14O3S [M + H]+: 311.0736, found: 311.0736.
Methyl (E)-2-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3g):
Orange waxy solid (56.6 mg, 91% yield), Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5)). 1H NMR (400 MHz, CDCl3) δ 7.69 (t, J = 7.3 Hz, 2H), 7.53–7.37 (m, 4H), 7.30–7.24 (m, 1H), 7.13 (d, J = 7.8 Hz, 1H), 3.85 (s, 3H), 2.34 (s, 3H). HRMS (ESI): m/z calcd for C18H14O3S [M + H]+: 311.0736, found: 311.0736.
Methyl (E)-1-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3h):
Light yellow solid (56.6 mg, 91% yield), mp 128–129 °C, Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.65–7.61 (m, 1H), 7.58–7.49 (m, 2H), 7.47–7.31 (m, 3H), 7.30–7.24 (m, 1H), 7.19 (t, J = 7.6 Hz, 1H), 3.86 (s, 3H), 2.61 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 196.57, 165.56, 141.66, 140.72, 140.52, 138.49, 137.08, 136.87, 135.92, 134.17, 132.39, 130.22, 129.63, 129.36, 126.51, 52.75, 29.73, 21.48. HRMS (ESI): m/z calcd for C18H14O3S [M + H]+: 311.0736, found: 311.0740.
tert-Butyl (E)-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3i):
Green oil (57.0 mg, 84% yield), Rf = 0.73 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.73 -7.65 (m, 1H), 7.64–7.56 (m, 2H), 7.46–7.40 (m, 1H), 7.39–7.29 (m, 2H), 7.26–7.15 (m, 3H), 1.46 (s, 9H). HRMS (ESI): m/z calcd for C20H18O3S [M + H]+: 339.1049, found: 339.1052.
tert-Butyl (E)-3-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3j):
Orange solid (58.0 mg, 82% yield), mp 113–115 °C, Rf = 0.75 (Ethyl acetate: Petroleum ether = 1:5)). 1H NMR (400 MHz, CDCl3) δ 7.70–7.63 (m, 1H), 7.62–7.53 (m, 2H), 7.52–7.45 (m, 1H), 7.42–7.31 (m, 2H), 7.27–7.24 (m, 2H), 2.33 (s, 3H), 1.53 (s, 9H). 13C NMR (101 MHz, CDCl3) δ 196.30, 164.32, 141.00, 138.68, 137.83, 137.64, 137.15, 136.39, 136.16, 133.63, 133.03, 132.11, 131.95, 129.95, 129.73, 129.32, 82.28, 28.05, 20.76. HRMS (ESI): m/z calcd for C21H20O3S [M + H]+: 353.1206, found: 353.1207.
tert-Butyl (E)-2-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3k):
Bright yellow waxy solid (58.7 mg, 83% yield), Rf = 0.71 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.72–7.64 (m, 2H), 7.54–7.47 (m, 2H), 7.42–7.36 (m, 1H), 7.34 (s, 1H), 7.28–7.24 (m, 1H), 7.14–7.11 (m, 1H), 2.39 (s, 3H), 1.53 (s, 9H). HRMS (ESI): m/z calcd for C21H20O3S [M + H]+: 353.1206, found: 353.1206.
tert-Butyl (E)-1-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3l):
Orange waxy solid (56.5 mg, 80% yield), Rf = 0.72 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.62 (d, J = 7.8 Hz, 1H), 7.53 (t, J = 8.4 Hz, 2H), 7.43–7.35 (m, 2H), 7.30 (s, 1H), 7.26 (s, 1H), 7.19 (t, J = 7.6 Hz, 1H), 2.62 (s, 3H), 1.54 (s, 9H). 13C NMR (101 MHz, CDCl3) δ 197.09, 164.13, 142.07, 140.86, 139.29, 138.39, 137.55, 137.20, 136.77, 134.03, 132.28, 129.99, 129.77, 129.36, 129.28, 126.39, 82.25, 28.07, 21.44. HRMS (ESI): m/z calcd for C21H20O3S [M + Na]+: 375.1025, found: 375.1025.
Benzyl (E)-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3m):
Orange waxy solid (52.0 mg, 70% yield), Rf = 0.64 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.75 (d, J = 7.8 Hz, 1H), 7.68 (t, J = 7.0 Hz, 2H), 7.51 (d, J = 7.7 Hz, 1H), 7.48–7.14 (m, 10H), 5.36–5.24 (m, 2H). HRMS (ESI): m/z calcd for C23H16O3S [M + H]+: 373.0893, found: 373.0894.
Benzyl (E)-3-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3n):
Orange waxy solid (54.4 mg, 70% yield), Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.68 (d, J = 7.8 Hz, 1H), 7.63–7.54 (m, 2H), 7.52–7.44 (m, 2H), 7.42–7.30 (m, 6H), 7.28–7.18 (m, 2H), 5.35–5.24 (m, 2H), 2.32 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 195.78, 165.12, 140.56, 140.03, 137.76, 137.71, 136.28, 135.52, 133.76, 133.19, 132.17, 132.00, 129.94, 129.85, 129.61, 128.63, 128.38, 128.15, 67.43, 20.78. HRMS (ESI): m/z calcd for C24H18O3S [M + H]+: 387.1049, found: 387.1052.
Benzyl (E)-2-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3o):
Light yellow waxy solid (57.4 mg, 74% yield), Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.73–7.53 (m, 2H), 7.53–7.45 (m, 2H), 7.43–7.22 (m, 8H), 7.12 (d, J = 7.9 Hz, 1H), 5.34–5.24 (m, 2H), 2.33 (d, J = 41.6 Hz, 3H). HRMS (ESI): m/z calcd for C24H18O3S [M + H]+: 387.1049, found: 387.1049.
Benzyl (E)-1-methyl-5-oxo-5H-dibenzo[b,g]thiocine-7-carboxylate (3p):
Orange waxy solid (60.6 mg, 78% yield), Rf = 0.62 (Ethyl acetate: Petroleum ether = 1:5). 1H NMR (400 MHz, CDCl3) δ 7.62 (d, J = 7.8 Hz, 1H), 7.53 (d, J = 7.9 Hz, 2H), 7.46–7.30 (m, 8H), 7.29–7.23 (m, 1H), 7.17 (t, J = 7.6 Hz, 1H), 5.30 (d, J = 7.2 Hz, 2H), 2.61 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 196.59, 164.90, 141.62, 140.76, 140.66, 138.48, 137.08, 136.90, 135.91, 135.52, 134.18, 132.41, 130.21, 129.69, 129.66, 129.35, 128.65, 128.41, 128.21, 126.50, 67.42, 21.48. HRMS (ESI): m/z calcd for C24H18O3S [M + H]+: 387.1049, found: 387.1051.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/reactions6020035/s1, 1H and 13C-NMR spectra of compounds 3a–3p.

Author Contributions

J.F.: experimental design, writing—original draft preparation, and writing—review and editing. W.Z. and H.Z.: experiments and data collection. Q.H., A.H., K.L. and G.Y.: data analysis. All authors revised the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in this study are included in the article and Supplementary Materials. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare no conflicts of interest.

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Reactions 06 00035 sch001
Scheme 1. Representative examples of sulfur-containing heterocycles.
Scheme 1. Representative examples of sulfur-containing heterocycles.
Reactions 06 00035 sch001
Reactions 06 00035 sch002
Scheme 2. Substrate scope for the domino reaction between various 2-methylenebenzothiophene-3-ones 1 and 2-(trimethylsilyl)phenyl trifluoromethanesulfonate 2. Reaction conditions: 1 (0.20 mmol), 2 (0.40 mmol), and TBAT (0.40 mmol) in CH3CN (2.0 mL) at 30 °C; isolated yields.
Scheme 2. Substrate scope for the domino reaction between various 2-methylenebenzothiophene-3-ones 1 and 2-(trimethylsilyl)phenyl trifluoromethanesulfonate 2. Reaction conditions: 1 (0.20 mmol), 2 (0.40 mmol), and TBAT (0.40 mmol) in CH3CN (2.0 mL) at 30 °C; isolated yields.
Reactions 06 00035 sch002
Reactions 06 00035 sch003
Scheme 3. Scale-up reaction.
Scheme 3. Scale-up reaction.
Reactions 06 00035 sch003
Table 1. Optimization of the reaction conditions a.
Table 1. Optimization of the reaction conditions a.
Reactions 06 00035 i001
EntrySolventF SourceT (°C)Yield (%) b
1EtOAcCsF30Trace
2THFCsF30Trace
3CH2Cl2CsF30Trace
4EtOHCsF30Trace
5TolueneCsF30N.R. c
6AcetoneCsF3033
7CH3CNCsF3052
8CH3CNKF3016
9CH3CNNaF30Trace
10CH3CNTBAF30Trace
11CH3CNTBAT3092
12 dCH3CNTBAT3073
13CH3CNTBAT4077
14CH3CNTBAT5084
15CH3CNTBAT6091
16 eCH3CNTBAT3092
17 fCH3CNTBAT3087
a Unless otherwise noted, the reaction was carried out with 1a (0.05 mmol), 2 (0.10 mmol, 2.0 equiv.,) and the fluorine source (0.10 mmol, 2.0 equiv.) in a solvent (0.50 mL) at the indicated temperature for 4 h. b Isolated yield after flash chromatography on silica gel. c N.R. = no reaction. d 2.0 equiv. of 18-crown-6 was added. e 3.0 equiv. of TBAT and 3.0 equiv. of 2 were used. f 4.0 equiv. of TBAT and 4.0 equiv. of 2 were used. THF = tetrahydrofuran. TBAT = tetrabutylammonium difluorotriphenylsilicate. TBAF = tetrabutylammonium fluoride.
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Feng, J.; Zou, W.; Zhang, H.; Huang, Q.; Huang, A.; Liu, K.; Yue, G. Efficient Synthesis of Eight-Membered Cyclic Diaryl Sulfides via an Aryne Reaction with 2-Methylenebenzothiophene-3-Ones. Reactions 2025, 6, 35. https://doi.org/10.3390/reactions6020035

AMA Style

Feng J, Zou W, Zhang H, Huang Q, Huang A, Liu K, Yue G. Efficient Synthesis of Eight-Membered Cyclic Diaryl Sulfides via an Aryne Reaction with 2-Methylenebenzothiophene-3-Ones. Reactions. 2025; 6(2):35. https://doi.org/10.3390/reactions6020035

Chicago/Turabian Style

Feng, Juhua, Wenjie Zou, Haokun Zhang, Qilin Huang, Ailin Huang, Kuan Liu, and Guizhou Yue. 2025. "Efficient Synthesis of Eight-Membered Cyclic Diaryl Sulfides via an Aryne Reaction with 2-Methylenebenzothiophene-3-Ones" Reactions 6, no. 2: 35. https://doi.org/10.3390/reactions6020035

APA Style

Feng, J., Zou, W., Zhang, H., Huang, Q., Huang, A., Liu, K., & Yue, G. (2025). Efficient Synthesis of Eight-Membered Cyclic Diaryl Sulfides via an Aryne Reaction with 2-Methylenebenzothiophene-3-Ones. Reactions, 6(2), 35. https://doi.org/10.3390/reactions6020035

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