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Original article
09 2022
:15;
104097
doi:
10.1016/j.arabjc.2022.104097

Domino synthetic strategy for tetrahydrothiophene derivatives from 2-acetylfuran/2-acetylthiophene, benzaldehydes, and sulfur powder

, , , , , , , , , ,
a Department of Chemistry & Chemical Engineering, Lvliang University, Lvliang 033001, PR China
b School of Chemistry and Chemical Engineering, Shanxi Datong University, Datong 037009, PR China
c Department of Chemistry, Kansas State University, Manhattan, KS 66506, USA

⁎Corresponding authors. chenddxy@163.com (Dongdong Chen), yangxufeng@llhc.edu.cn (Xufeng Yang)

Received: , Accepted: ,
© The Author(s) 2022
Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
1 These authors contribute equally to this work.

Abstract

Abstract

A domino reaction from 2-acetylfuran/2-acetylthiophene, benzaldehydes and sulfur powder has been developed to synthesize a series of tetrahydrothiophene derivatives. The reaction proceeds well to construct five new bonds and a tetrahydrothiophene ring by one-pot. A possible mechanism was proposed, involving a stepwise of Aldol/double Michael addition/internal SN2 cascaded reaction with sulfur powder acts as a source of sulfur. This method is characterized by mild reaction conditions, commercially available starting materials and transition-metal-free.

Keywords

Domino reaction
Tetrahydrothiophene derivatives
Sulfur Powder
Cyclization
Benzaldehydes
1

1 Introduction

Sulfur-containing compounds play an important role in academia and industry communities due to their extensive use in medicines (Darvesh et al., 2008; Smith et al., 2014; Pluta et al., 2017; Nielsen et al., 2000; Du et al., 2021), pesticides (Zyk et al., 2003; McReynolds et al., 2004, Wu et al., 2016) and synthons (Chang et al., 2018; Uno et al., 2019; Xiong et al., 2020; Liu et al., 2021; Dong et al., 2021). Thiophene skeletons are commonly found in natural medicines (Thase et al., 2006; Liu and Jiang, 2013; Rechfeld et al., 2014), organic materials (Ortiz et al., 2009; Ie et al., 2011), especially in biologically active molecules (Wiviott et al., 2005; Wang et al., 2010; Elgazwy et al., 2013; Lucas et al., 2015; Malani et al., 2016; Bozorov et al., 2017; Mishra et al., 2018; Kim et al., 2020). Among these, some chemicals with tetrahydrothiophene moiety exhibit good biological activities. Natural products like garlicnin A and biotin exhibit antitumor and potential anti-HIV activities (Stewart et al., 2007; El-Aasr et al., 2011) respectively, while the analogues of penicillin N and hippolachnin possess antibacterial and antifungal activity (Fig. 1) (Block et al., 2018; Winter et al., 2019). These fruitful applications have aroused chemists’ interest in developing new strategies for synthesis of thiophene derivatives. Elemental sulfur, the simplest inorganic substance, has been a research hotspot as a source of sulfur (Gao et al., 2017; Zhang et al., 2018; Xiong et al., 2019; Gan et al., 2019; Shi et al., 2020; Zhang et al., 2021). In the past decades, some synthetic methods for the thiophene derivatives have been reported, using sulfur powder as the sulfur source (Nguyen et al., 2017; Jin et al., 2020; Teja et al., 2020; Yue et al., 2020). But, its practical applications have been greatly limited by the participation of metals (Wang et al., 2021) and harsh reaction conditions (Ni et al., 2017). In this case, the domino reaction is a simple and effective method to construct complex molecules from simple precursors (Wang et al., 2009; Yamamoto et al., 2019; Golantsov et al., 2020; Liu et al., 2020). However, to the best of our knowledge, there are little studies on the construction of tetrahydrothiophene ring with domino synthesis strategy.

compounds containing tetrahydrothiophene ring.
Fig. 1 compounds containing tetrahydrothiophene ring.

In our previous work, we developed a novel method to synthesize a series of tetrahydrothiopyran derivatives by domino reaction (Scheme 1a) (Chen et al., 2020). In that reaction, sodium sulfide acts as sulfur source and base. In this work, sulfur powder (acts as sulfur source) rather than sodium sulfide was selected for the new tandem Aldol/double Michael addition/internal SN2 reaction. Different with the products from sodium sulfide reactions, the sulfur powder reactions produced a series of tetrahydrothiophene derivatives conveniently in mild conditions with no transition-metal-catalysts needed (Scheme 1b). As far as we are concerned, this new class of tetrahydrothiophene derivatives have never been reported.

Synthesis of S-heterocycles via domino reactions.
Scheme 1 Synthesis of S-heterocycles via domino reactions.

2

2 Material and methods

2.1

2.1 Chemical reagents

The chemical reagents were purchased from commercial suppliers, and used without further purification (sulfur powder, 325 mesh).

2.2

2.2 Structure characterization

All compounds were fully characterized by spectroscopic data. Melting points (mp) were determined on an XT-4 micro-melting point apparatus and uncorrected. Nuclear magnetic resonance spectra (NMR) were recorded on Bruker AVIII-400 (1H: 400 MHz, 13C: 100 MHz) or Bruker AVIII-500 HD (1H: 500 MHz, 13C: 125 MHz) (Bruker, Karlsruhe, Germany) instrument in CDCl3 or DMSO‑d6 and using tetramethyl silane (TMS) as an internal standard. Spin multiplicities are indicated by the following symbols: s (singlet), d (doublet), t (triplet), q (quartet), and m (multiplet). All chemical shifts (δ values) are given in ppm and coupling constants (J values) are given in Hz. High resolution mass spectra (HRMS) were obtained using a Bruker micrOTOF-Q II focus spectrometer (ESI). Single-crystal X-ray diffraction data was collected at room temperature on a Bruker SMART APEX Ⅱ (λ = 0.71073 Å). The crystal structures were solved by direct method of SHELXS-2014 and refined by full-matrix least-squares techniques using the SHELXL-2014 program.

2.3

2.3 General experimental procedures for the synthesis of compounds 3

A mixture of sulfur powder (96 mg, 3 mmol), NaOH (120 mg, 3 mmol) and MeOH (5 mL) was stirred at room temperature for 0.5 h. 2-Acetylfuran/2-acetylthiophene 1 (1.0 mmol) and benzaldehyde 2 (1.1 mmol) was added and the reaction mixture was stirred for 72 h at room temperature. Upon completion, monitoring was carried out by TLC. The reaction mixture was diluted with DCM (10 mL) and filtered. The solution washed with water (20 mL × 3) and saturated brine (20 mL × 3). The organic phase was dried with anhydrous Na2SO4 and evaporated under vacuum. The crude product recrystallized with petroleum ether/ethyl acetate (10:1, v/v) mixture and dried under reduced pressure to afford pure product 3.

3

3 Results and discussion

In order to investigate adaptability of the tandem process, we chose the synthesis of tetrahydrothiophene derivative 3aa from 2-acetylfuran 1a, benzaldehyde 2a, and sulfur powder (S8) as a model system to evaluate different reaction parameters at room temperature (Table 1). As shown in Table 1, the desired product 3aa was obtained with low yields in aprotic solvent (DCM, toluene and DMF) (Entries 1–3, Table 1). Protic solvent such as ethanol (EtOH) and methanol (MeOH) were evaluated next where, MeOH proved to be the best choice (Entries 4–5, Table 1). The yield of 3aa was increasing when reaction time was increased from 12 h to 72 h. (Entries 6–8, Table 1). Various bases including inorganics (NaOH, Na2CO3 and Cs2CO3) and an organic one (1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)) were further screened (Entries 8–11, Table 1), and NaOH was the optimal base and afforded product 3aa with 89 % yield (Entry 8, Table 1). Therefore, the treatment of the reaction solution of 2-acetylfuran 1a (1 equiv, 1 mmol), benzaldehyde 2a (1.1 equiv, 1.1 mmol) and sulfur powder (3 equiv, 3 mmol) with NaOH (3 equiv, 3 mmol) in MeOH (5 mL) at at room temperature for 48 h was selected as the most optimal condition.

Table 1 Optimization of the Reaction Conditions.[a].
Entry Base Solvent Time (h) Yield (%)[b]
1 NaOH DCM 12 7
2 NaOH toluene 12 4
3 NaOH DMF 12 5
4 NaOH EtOH 12 24
5 NaOH MeOH 12 36
6 NaOH MeOH 24 51
7 NaOH MeOH 48 82
8 NaOH MeOH 72 89
9 Na2CO3 MeOH 72 76
10 Cs2CO3 MeOH 72 78
11 DBU[c] MeOH 72 54
[a] Reaction conditions: 1a (1 mmol), 2a (1.1 mmol), S8 (3 mmol, 325 mesh), base (3 mmol) solvent (5 mL).
[b] Isolated yield based on 1a.
[c] DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene.
Table 2 Crystal Data of of compound 3aa.
Empirical formula C26H20O4S
Formula weight 428.48
Crystal size 0.36 × 0.29 × 0.21
Crystal system Monoclinic
Space group C2/c
a (Å) 24.655(4)
b (Å) 11.1253(16)
c (Å) 20.570(3)
α (deg) 90
β (deg) 125.165(2)
γ (deg) 90
Volume 4612.5(12)
Z 8
Dc (g.cm−3) 0.169
F (0 0 0) 1792.0
Reflections collected 4308
Unique reflections 2900
Goof 0.981
R1a [I > 2σ(I)] 0.0424
wR2b [I > 2σ(I)] 0.1240
a R1 = Σ||Fo| − |Fc||/Σ|Fo|.
b wR2 = |Σw(|Fo|2 − |Fc|2)|/Σ|w(Fo)2|1/2, w = 1/[σ2(Fo2) + (aP)2 + bP]. P = (Fo2 + 2Fc2)/3.

With optimized reaction condition in hand (Table 1, entry 8), the limitations of the synthesis of tetrahydrothiophene derivatives 3 from 2-acetylfuran 1a/2-acetylthiophene 1b, various benzaldehydes 2 and sulfur powder were explored (Scheme 2). Compounds belong to 3a and 3b series can be obtained from acetylfuran 1a and acetylthiophene 1b with similar yields. The type and position of the substituents in the benzene ring of benzaldehydes 2 can significantly influence the yields of tetrahydrothiophene derivatives 3. The yields from non-substituted benzaldehyde substrates (3aa, 3ba) and 4-position chloro (3ac, 3bc) and bromo (3ad, 3bd) substituted benzaldehyde substrates exhibited excellent yields, while the yield from fluoro substituted benzaldehyde substrates were moderate. The presence of electron-drawing group such as trifluoromethyl (3af, 3bf) and strong electron-donating group such as methoxy (3an, 3bn) or methylthio (3ao, 3bo) showed satisfied yields. Gratifyingly, all of alkyl benzaldehydes can be converted to tetrahydrothiophene derivatives as expected (3ag-3am, 3bg-3bm). The para monomethyl benzaldehydes exhibited higher yield than its ortho and meta counterparts. (3ag-3ai, 3bg-3bi). The yield from phenyl benzaldehyde substrates (3ap, 3aq, 3 bp, 3bq) decreased. It may cause by the stability of intermediate A, which hindered the subsequent Michael addition reaction (Scheme 5).

Synthesis of tetrahydrothiophene derivatives 3. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.
Scheme 2 Synthesis of tetrahydrothiophene derivatives 3. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.

To further test the generality of this domino reaction, other methyl ketones and formaldehyde were investigated providing tetrahydrothiophene derivatives 3r − 3u (Scheme 3). 3-acetylthiophene (3r), acetophenone (3s) and 4′-bromoacetophenone (-3t) were well-tolerated in this reaction, giving tetrahydrothiophene derivatives 3r −3t in moderate to high yields. Formaldehyde (aliphatic aldehyde) was screened in this reaction, but the reaction generated a complex mixture from which target product could not be isolated unfortunately.

Synthesis of tetrahydrothiophene derivatives -3r − 3u. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.
Scheme 3 Synthesis of tetrahydrothiophene derivatives -3r − 3u. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.

The structures of the tetrahydrothiophene derivatives (3) were identified by 1H NMR, 13C NMR, and HRMS. Furthermore, the relative stereochemistry of representative 3aa was confirmed by the X-ray single-crystal analysis (Fig. 2 and Table 2) (CCDC 2077789), showing that two phenyl groups (3,5-position) directed to the same side, while two acyl groups (2,4-position) directed to another side.

Single-crystal X-ray structures and relative stereochemistry of compound 3aa.
Fig. 2 Single-crystal X-ray structures and relative stereochemistry of compound 3aa.

Next, the gram-scale were performed. The corresponding products 3aa and 3ab were obtained in 76% and 73% yields under the standard conditions (Scheme 4).

Large-scale reaction. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.
Scheme 4 Large-scale reaction. Reaction conditions: 1 (1 mmol), 2 (1.1 mmol), S8 (3 mmol) and NaOH (3 mmol) in MeOH (5 mL) at room temperature. Isolated yield based on 1.
Plausible reaction mechanism.
Scheme 5 Plausible reaction mechanism.

A possible mechanistic pathway is outlined in Scheme 5. The key intermediate α,β-unsaturated ketone A was generated by an Aldol reaction from 2-acetylfuran (1a)/2-acetylthiophene (1b) and substituted benzaldehyde 2 with the presence of sodium hydroxide (the intermediate A of compound 3ac had been captured and determined by 1H, 13C NMR and HRMS, see the Supporting Information). Sulfur atom was then attacked intermediate A to produce a polysulfide B under basic condition. Subsequently, Michael addition was taken place between intermediate A and B to generate intermediate C. Finally, cyclization and elimination of fragmentation of S7 would lead to tetrahydrothiophene derivatives 3.

4

4 Conclusion

In conclusion, we have explored a novel domino reaction to provide straightforward access to tetrahydrothiophene derivatives through an Aldol reaction/double Michael addition/internal SN2 cascaded reaction with sulfur powder acts as a source of sulfur. The tetrahydrothiophene ring can be smoothly constructed from readies available substrates (2-acetylfuran/2-acetylthiophene, benzaldehydes and sulfur powder) with high yields under mild and transition-metal-free conditions. Further applications and reaction mechanism of this domino reaction are under study in our laboratory.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The work is financially supported by the Natural Science Foundation of Shanxi Province (20210302124072, 202103021223386), Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi (2019L0941, 2019L0937, 2019L0966, 2021L388), the High-level Scientific and Technological Talent Introduction Project of Lvliang (2019108, 2019105, 2019109, 2017-011-01) and national natural science foundation of China (51804191).

Author Contributions

D. Chen and X. F. Yang conceived the research and wrote the manuscript. Y. Bai, Q. Cheng, J. Li, Z. Tong, J. Hou, T. Liu, Y. Guo, X. Tang and X. Yang performed all experiments. All authors designed experiments, analyzed data, edited and approved the manuscript.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Appendix A

Supplementary material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.arabjc.2022.104097.

Appendix A

Supplementary material

The following are the Supplementary data to this article:

Supplementary Data 1

Supplementary Data 1


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