Direct electrochemical synthesis of arenesulfonyl fluorides from nitroarenes: a dramatic ionic liquid effect

Abstract

A practical electrochemical strategy for the direct synthesis of arenesulfonyl fluorides from industrial feedstock nitroarenes is described. The key to success lies in using a cheap ionic liquid N-methylimidazolium p-toluenesulfonate ([Mim]TolSO₃) as an effective additive and electrolyte to facilitate the selective reduction of nitroarenes to the corresponding aniline intermediate, promoting the desired fluorosulfonylation with broad functional group tolerance under mild conditions.

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Introduction

With the emergence of new applications for fluorinating reagents,¹¹⁸F radiolabeling agents,² and other fluorinated compounds for chemical biology research,³ interest in the synthesis of sulfonyl fluorides, including arenesulfonyl fluorides, has dramatically increased recently.⁴ Aryl sulfonyl fluorides are typically synthesized by chloride–fluoride exchange reactions of the corresponding arenesulfonyl chlorides,⁵ oxidative fluorination of sulfur-containing substrates (such as sodium sulfinic,⁶ thiols,⁷ sulfonyl hydrazides,⁸ disulfides,^7b,9 and sulfonates or sulfonic acids¹⁰) or by converting various prefunctionalized substrates such as aryl (pseudo)halides,¹¹ aryl boronic acids,¹² aryl diazonium salts,¹³ and others.¹⁴ Despite these advances, the development of practical, mild methods for accessing arenesulfonyl fluorides from inexpensive, widely available industrial feedstocks remains highly desirable.

On the other hand, nitroarenes are inexpensive and abundant industrial chemical feedstocks that can be easily accessed by the electrophilic aromatic nitration of arenes.¹⁵ The reported methods for transforming nitroarenes into arenesulfonyl fluorides often require multiple steps, which include the conversion of nitroarenes to the corresponding diazo salts by reduction/derivatization first, and the subsequent transformation with an SO₂ surrogate and fluorinating reagents enables the delivery of arenesulfonyl fluorides (Scheme 1a).¹³ Although these reliable multistep methods are widely used in organic synthesis, they have some drawbacks, including the need for tedious separation procedures and the generation of a lot of chemical waste.¹³ Therefore, a strategy for the direct denitrative fluorosulfonylation of nitroarenes to afford arenesulfonyl fluorides would be highly desirable in terms of step economy, environmental friendliness, cost, and speed. However, to the best of our knowledge, the use of nitroarenes for the direct synthesis of arenesulfonyl fluorides remains unexplored.

Scheme 1 Synthesis of arenesulfonyl fluorides from nitroarenes.

Electrochemistry, which has the advantages of being green and sustainable, has received considerable attention from researchers in academia and industry in the last decade.¹⁶ In this scenario, coupled with our previous success in electrosynthesis¹⁷ and the reductive dialkylation of nitroarenes,¹⁸ we envisioned that the use of electrochemistry tools to reduce nitroarenes in situ might provide a meaningful strategy to realize the anticipated denitrative fluorosulfonylation by overcoming the previous methods’ tedious reduction and pre-functionalization. Nevertheless, it is nontrivial to achieve this goal, as precedent examples have identified that depending on the specific reduction conditions, the intermediates for the reduction of nitroarenes might be completely different and complicated.¹⁹ For example, the reduction of nitrobenzene could result in nitrosobenzene, N-phenyl hydroxylamine, azoxybenzene, azobenzene, 1,2-diphenylhydrazine, or PhNH₂.^18,19 To this end, a prerequisite for the desired fluorosulfonylation lies in choosing suitable conditions that enable the selective reduction of nitroarenes to be realized in a controllable way. In addition, such reduction conditions should be compatible with the subsequent fluorosulfonylation process. Herein, by successfully overcoming the aforementioned challenges, we wish to report our preliminary results on the electrochemical denitrative fluorosulfonylation of nitroarenes (Scheme 1b). As detailed below, our strategy enables the preparation of arenesulfonyl fluorides with high efficiency and shows broad functional group tolerance.

Results and discussion

To find the optimal conditions for the desired denitrative fluorosulfonylation of nitroarenes, 4-nitrotoluene (1a) was chosen as the model substrate. After extensive screening of various reaction parameters, we were pleased to notice that the desired product 3a could be facilely isolated with 72% yield using commercially available 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO, 2) as an SO₂ surrogate, Selectfluor as a fluorinating reagent in an undivided cell with a graphite anode and a glassy carbon (GC) cathode (Table 1). As shown in entry 1, the reaction for 6 h at room temperature in an 8 : 1 (v/v) mixture of N-methylimidazolium p-toluenesulfonate ([Mim]TolSO₃) and MeOH containing tert-butyl nitrite (^tBuONO) as an additive at a constant current of 12 mA gave the best result. During the whole process, the voltage of the cell was 2.6–3.0 V. The essential dual role (as an electrolyte and a key additive for the selective reduction of nitroarenes) of [Mim]TolSO₃ will be detailed later. In comparison, replacing MeOH with MeCN, DMF, EtOH, CF₃CH₂OH or (CF₃)₂CHOH led to a lower or trace yield (entries 2–4). The replacement of [Mim]TolSO₃ with various alternative ionic liquids or common Brønsted acids (such as TsOH, H₂SO₄, or HCl) also decreased the yield (entries 5 and 6). This indicates that both the cation and anion parts of (Mim)TolSO₃ play very important roles for achieving good results. Other electrode combinations—RVC(+)/RVC(−) (RVC = reticulated vitreous carbon), Pt(+)/GC(−), and GC(+)/GC(−)—also gave similar yields (entry 7), as did alternative SO₂ surrogates (entry 8) and fluoride sources (entry 9). In addition, reducing or increasing the current lowered the yield (entry 10). Under an air atmosphere, the yield was only 43% (entry 11). The control experiment showed that ^tBuONO played a vital role in this transformation (entry 12), as did the electric current and [Mim]TolSO₃ (entry 13); none of the desired product was obtained in their absence.

Table 1 Reaction optimization^a

Entry	Variation from standard conditions	Yield of 3a ^b (%)
a Standard conditions: graphite (C, 0.8 × 0.2 cm^2) anode, glassy carbon (GC, 0.8 × 0.2 cm^2) cathode, 12 mA, 1a (0.30 mmol), 2 (0.20 mmol), Selectfluor (0.60 mmol), ^tBuONO (0.90 mmol), [Mim]TolSO3 (0.5 mL), MeOH (4 mL), room temperature (rt), N2 atmosphere, and 6 h. b Isolated yields. NFSI: N-fluorobenzenesulfonamide. [Bmim]: 1-butyl-3-methylimidazolium hexafluorophosphate.
1	None	72
2	CH3CN instead of MeOH	32
3	DMF instead of MeOH	42
4	EtOH, CF3CH2OH, (CF3)2CHOH instead of MeOH	65/trace/trace
5	[Bmim]Br, [Bmim]PF6, [Bmim]OAc, [Mim]Cl, [Mim]OAc, or [Mim]HSO4 instead of [Mim]TolSO3	Trace/8/13/0/0/13
6	H2SO4, HCl, TsOH instead of [Mim]TolSO3	0/0/0
7	RVC(+)/RVC(−), Pt(+)/GC(−), or GC(+)/GC(−) instead of C(+)/GC(−)	64/66/70
8	K2S2O5, CF3SO2Na, or Na2S2O5 instead of DABSO	8/0/43
9	Et3N·3HF, NFSI, KHF2 or KBF4 instead of Selectfluor	54/56/40/15
10	10 or 15 mA instead of 12 mA	69/53
11	Air instead of N2	43
12	No ^tBuONO	0
13	No electric current or [Mim]TolSO3	0

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With the optimal conditions in hand, we carefully evaluated various nitroarene substrates 1 (Table 2). Nitroarenes with alkyl groups (1a–1f), electron-withdrawing substituents (1g–1l, 1n), methoxy (1m), phenyl (1o), or a readily transformable bis(pinacolato)diboron substituent (1p) at the para position of the phenyl ring were successfully converted to the desired products 3a–3p in moderate to good yields (63–75%). Two naphthalene-based nitro compounds underwent fluorosulfonylation to give the desired products 3q and 3r in moderate yields. In addition, nitro compounds with a meta methyl (3s), halogen (3t–3v), trifluoromethyl (3w), phenyl (3x), or ester (3y) substituent were tolerated. We also evaluated ortho-methoxy substrates, which gave 3z under the standard conditions, albeit with moderate yield (59%). 3,5-Dimethyl substituted substrate was also tolerated (3aa). Furthermore, heteroarenesulfonyl fluorides with a coumarin, quinoline, indazole, fluorene or benzofuran core (3ab–3ad, 3af) were also accessed in reasonable yields. Finally, to our delight, sulfonyl fluorides derived from the pharmaceutical nimesulide, the natural product menthol, and the pesticide nitrofen could also be obtained (3ag–3ai), highlighting the good functional group tolerance of our strategy. It is noteworthy that denitrative arenes can often by detected in these cases as the major byproduct.

Table 2 Substrate scope^a

a For details, see the ESI.†

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To further demonstrate the green metrics of our method, Table 3 summarizes the green metrics of our method with the known protocols reported by Liu et al.^13a,b and Weng,^13c and product 3a has been chosen as a model example. For the four major green chemistry metrics we analysed, that is the E-factor, atom economy (AE), reaction mass efficiency (RME), and process mass intensity (PMI), lower values of the E-factor and the PMI, as well as higher values of RME, were observed for our protocol (for details, please see Part 5, ESI†). These indicate less waste is formed and a smaller total mass of reagents is required for our protocol along with better atom efficiency.²⁰

Table 3 Calculation of green chemistry metrics

Entry	Work of different groups	E-Factor	AE	RME	PMI
1	This work	21.3	20.8%	4.5%	22.4
2	Chen and Liu^13a	43.3	32.7%	2.3%	44.3
3	Zheng, Hu and Liu^13b	48.2	15.9%	2.0%	49.2
4	Weng^13c	45.1	16.3%	2.2%	46.1

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This novel electrochemical method could be performed on a gram scale. For example, the reaction of 9 mmol of 1a with DABSO 2 and Selectfluor gave the desired product 3a in 70% isolated yield under slightly modified conditions (Scheme 2).

Scheme 2 Gram-scale reaction.

To gain insight into the mechanism of this denitrative fluorosulfonylation of nitroarenes, a series of control experiments were conducted (Scheme 3). (1) First of all, the addition of 2 equiv. of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) to the model reaction only led to a trace amount of 3a (Scheme 3a). (2) Second, a radical clock experiment involving 2-nitro-1,1-biphenyl 4 only afforded dibenzo[b,d]thiophene 5,5-dioxide 5 in 81% yield, and sulfonyl fluoride product 6 could not be detected (Scheme 3b). These results suggest that an aryl radical might be generated during this transformation. (3) To identify the key intermediate for the transformation, a variety of plausible intermediates, such as nitrosobenzene 7, N-phenyl hydroxylamine 8, azoxybenzene 9, azobenzene 10, 1,2-diphenylhydrazine 11, or PhNH₂12, were tested under the optimal conditions (Scheme 3c). It turns out that only the use of nitrosobenzene 7 or PhNH₂12b enables the delivery of a comparable yield of 3b. In addition, no 3b could be detected in the absence of electricity using either 7 or 12b as the substrate. This indicates that either 7 or 12b might serve as the reactive species for our fluorosulfonylation. (4) To give a deep understanding of the role of [Mim]TolSO₃, cyclic voltammetry (CV) studies were conducted.^19c–l As shown in Scheme 3d, while no signal was observed from 0 to −2.0 V for 1a, only one irreversible reduction peak at −1.2 V was observed in the presence of [Mim]TolSO₃.^19k This is different from the previous work of Zhang,¹⁹ⁱ who reported that two obvious reduction peaks were observed for the reduction of PhNO₂ in the presence of ⁿBuNHSO₄. (5) To further identify the key role of [Mim]TolSO₃, an exhaustive electrolysis experiment was performed. As shown in Scheme 3e, it was noticed that the presence of [Mim]TolSO₃ was crucial for the selective reduction of the nitro group. While the presence of [Mim]TolSO₃ enabled us to isolate intermediate 12a with 83% yield, no 12a was detected when the reaction was carried out without [Mim]TolSO₃. Furthermore, while the use of [Mim]HSO₄ could deliver 12a with 21% yield, the presence of other acids such as [Mim]Cl, [Mim]OAc, H₂SO₄, HCl or TsOH instead of [Mim]TolSO₃ only led to trace 12a. These results not only demonstrate that such an ionic liquid is essential for promoting the selective reduction of nitroarenes to the corresponding aniline intermediate, but also indicate that aniline might serve as the key intermediate for the transformation.

Scheme 3 Mechanistic studies (for details, please see the ESI†).

On the basis of the above-described results and previous reports,^11–15,19 two plausible mechanisms have been proposed (Fig. 1). Initially, under the assistance of [Mim]TolSO₃, nitroarenes 1 could accept six electrons at the cathode, along with protons, to form aniline Bvia ArNO intermediate A. The aniline B could react with ^tBuONO to afford aryl diazo salt C, which undergoes single-electron reduction on the cathode, to form aromatic radical D with the elimination of N₂.¹⁹ⁱ The aryl radical D could be rapidly captured by SO₂ to form the corresponding aryl sulfonyl intermediate E. After this, intermediate E could be converted to desired arenesulfonyl fluoride 3via rapid radical fluorination by Selectfluor.^13a,21 Alternatively, intermediate E could combine with radical cation F (formed via the oxidation of DABCO at the cathode), giving rise to the species G.²² The subsequent nucleophilic substitution with BF₄⁻ (the anion of Selectfluor) gives rise to the observed 3. This is consistent with the fact that the use of KBF₄ as a fluoro source also enables the production of product 3a, albeit with low yield (Table 1, entry 8).

Fig. 1 Two plausible mechanisms.

Conclusions

In summary, we have developed the first electrochemical fluorosulfonylation of nitroarenes. This practical, efficient method affords arenesulfonyl fluorides in moderate to good yields and shows good functional group tolerance. The method, which utilizes inexpensive electrodes and simple ionic liquid as a mediator to help the selective reduction of nitroarenes and does not require additional oxidants or reducing agents, can be expected to be a valuable addition to the toolkit for the preparation of aromatic hydrocarbon sulfonyl fluorides.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

Financial support from the NSFC (22102012, 22202021, 22272011, 22201062, and 22372015) and the National Natural Science Foundation of Henan Province (222300420111) is gratefully acknowledged.

References

1. (a) M. K. Nielsen, C. R. Ugaz, W. Li and A. G. Doyle, J. Am. Chem. Soc., 2015, 137, 9571–9574; (b) C. J. Smedley, A. S. Barrow, C. Spiteri, M.-C. Giel, P. Sharma and J. E. Moses, Chem. – Eur. J., 2017, 23, 9990–9995; (c) M. K. Nielsen, D. T. Ahneman, O. Riera and A. G. Doyle, J. Am. Chem. Soc., 2018, 140, 5004–5008.
2. L. Matesic, N. A. Wyatt, B. H. Fraser, M. P. Roberts, T. Q. Pham and I. Greguric, J. Org. Chem., 2013, 78, 11262–11270.
3. (a) A. Narayanan and L. H. Jones, Chem. Sci., 2015, 6, 2650–2659; (b) D. A. Shannon, C. Gu, C. J. McLaughlin, M. Kaiser, R. A. L. van der Hoorn and E. Weerapana, ChemBioChem, 2012, 13, 2327–2330; (c) N. P. Grimster, S. Connelly, A. Baranczak, J. Dong, L. B. Krasnova, K. B. Sharpless, E. T. Powers, I. A. Wilson and J. W. Kelly, J. Am. Chem. Soc., 2013, 135, 5656–5668; (d) E. C. Hett, H. Xu, K. F. Geoghegan, A. Gopalsamy, R. E. Kyne, C. A. Menard, A. Narayanan, M. D. Parikh, S. Liu, L. Roberts, R. P. Robinson, M. A. Tones and L. H. Jones, ACS Chem. Biol., 2015, 10, 1094–1098.
4. (a) T. Zhong, Z. Chen, J. Yi, G. Lu and J. Weng, Chin. Chem. Lett., 2021, 32, 2736–2750; (b) F. He, Y. Li and J. Wu, Org. Chem. Front., 2022, 9, 5299–5305; (c) T. S.-B. Lou and M. C. Willis, Nat. Rev. Chem., 2022, 6, 146–162.
5. (a) W. Davies and J. H. Dick, J. Chem. Soc., 1932, 483–486; (b) T. A. Bianchi and L. A. Cate, J. Org. Chem., 1977, 42, 2031–2032; (c) C. Patel, E. André-Joyaux, J. A. Leitch, X. M. Irujo-Labalde, F. Ibba, J. Struijs, M. A. Ellwanger, R. Paton, D. L. Browne, G. Pupo, S. Aldridge, M. A. Hayward and V. Gouverneur, Science, 2023, 381, 302–306.
6. (a) M. Kulka, J. Am. Chem. Soc., 1950, 72, 1215–1218; (b) L. Zhang, X. Cheng and Q.-L. Zhou, Chin. J. Chem., 2022, 40, 1687–1692; (c) B. J. Thomson, S. R. Khasnavis, E. C. Grigorian, R. Krishnan, T. D. Yassa, K. Lee, G. M. Sammis and N. D. Ball, Chem. Commun., 2023, 59, 555–558.
7. (a) S. W. Wright and K. N. Hallstrom, J. Org. Chem., 2006, 71, 1080–1084; (b) G. Laudadio, A. d. A. Bartolomeu, L. M. H. M. Verwijlen, Y. Cao, K. T. de Oliveira and T. Noël, J. Am. Chem. Soc., 2019, 141, 11832–11836.
8. L. Tang, Y. Yang, L. Wen, X. Yang and Z. Wang, Green Chem., 2016, 18, 1224–1228.
9. (a) M. Kirihara, S. Naito, Y. Ishizuka, H. Hanai and T. Noguchi, Tetrahedron Lett., 2011, 52, 3086–3089; (b) M. Kirihara, S. Naito, Y. Nishimura, Y. Ishizuka, T. Iwai, H. Takeuchi, T. Ogata, H. Hanai, Y. Kinoshita, M. Kishida, K. Yamazaki, T. Noguchi and S. Yamashoji, Tetrahedron, 2014, 70, 2464–2471.
10. (a) Y. Jiang, N. S. Alharbi, B. Sun and H.-L. Qin, RSC Adv., 2019, 9, 13863–13867; (b) M. Perez-Palau and J. Cornella, Eur. J. Org. Chem., 2020, 2497–2500.
11. (a) A. T. Davies, J. M. Curto, S. W. Bagley and M. C. Willis, Chem. Sci., 2017, 8, 1233–1237; (b) A. L. Tribby, I. Rodriguez, S. Shariffudin and N. D. Ball, J. Org. Chem., 2017, 82, 2294–2299; (c) T. S.-B. Lou, Y. Kawamata, T. Ewing, G. A. Correa-Otero, M. R. Collins and P. S. Baran, Angew. Chem., Int. Ed., 2022, 61, e202208080.
12. (a) Y. Chen and M. C. Willis, Chem. Sci., 2017, 8, 3249–3253; (b) P. K. T. Lo, Y. Chen and M. C. Willis, ACS Catal., 2019, 9, 10668–10673; (c) M. Magre and J. Cornella, J. Am. Chem. Soc., 2021, 143, 21497–21502.
13. (a) Y. Liu, D. Yu, Y. Guo, J.-C. Xiao, Q.-Y. Chen and C. Liu, Org. Lett., 2020, 22, 2281–2286; (b) Q. Lin, Z. Ma, C. Zheng, X.-J. Hu, Y. Guo, Q.-Y. Chen and C. Liu, Chin. J. Chem., 2020, 38, 1107–1110; (c) T. Zhong, M.-K. Pang, Z.-D. Chen, B. Zhang, J. Weng and G. Lu, Org. Lett., 2020, 22, 3072–3078.
14. (a) J. Kwon and B. M. Kim, Org. Lett., 2019, 21, 428–433; (b) C. Lee, N. D. Ball and G. M. Sammis, Chem. Commun., 2019, 55, 14753–14756; (c) X. Kong, Y. Chen, Q. Liu, W. Wang, S. Zhang, Q. Zhang, X. Chen, Y.-Q. Xu and Z.-Y. Cao, Org. Lett., 2023, 25, 581–586; (d) L. Shan, Z. Ma, C. Ou, Y. Cai, Y. Ma, Y. Guo, X. Ma and C. Liu, Org. Biomol. Chem., 2023, 21, 3789–3793; (e) Y. Ma, Q. Pan, C. Ou, Y. Cai, X. Ma and C. Liu, Org. Biomol. Chem., 2023, 21, 7597–7601. For other recent examples for the synthesis of sulfonyl fluorides, please see: (f) D. Chen, X. Nie, Q. Feng, Y. Zhang, Y. Wang, Q. Wang, L. Huang, S. Huang and S. Liao, Angew. Chem., Int. Ed., 2021, 60, 27271–27276; (g) N. L. Frye, C. G. Daniliuc and A. Studer, Angew. Chem., Int. Ed., 2022, 61, e202115593; (h) P. Wang, H. Zhang, M. Zhao, S. Ji, L. Lin, N. Yang, X. Nie, J. Song and S. Liao, Angew. Chem., Int. Ed., 2022, 61, e202207684; (i) W. Zhang, H. Li, X. Li, Z. Zou, M. Huang, J. Liu, X. Wang, S. Ni, Y. Pan and Y. A. Wang, Nat. Commun., 2022, 13, 3515; (j) R. Xu, T. Xu, M. Yang, T. Cao and S. Liao, Nat. Commun., 2019, 10, 3752; (k) J. F. Erchinger, R. Hoogesteger, R. Laskar, S. Dutta, C. Hümpel, D. Rana, C. G. Daniliuc and F. Glorius, J. Am. Chem. Soc., 2023, 145, 2364–2374; (l) H. Zhang, X. Sun, C. Ma, C. Li, Y. Ni, Y. Yu, Y.-Q. Xu, S.-F. Ni and Z.-Y. Cao, ACS Catal., 2024 DOI:10.1021/acscatal.3c05154. For a recent review, please see: (m) Y. Zheng, W. Lu, T. Ma and S. Huang, Org. Chem. Front., 2024, 11, 217–235.
15. (a) N. Ono, The Nitro Group in Organic Synthesis, Wiley-VCH, New York, 2001; (b) G. Booth, Nitro Compounds, Aromatic, Wiley-VCH, New York, 2000.
16. For selected reviews, please see: (a) M. Yan, Y. Kawamata and P. S. Baran, Chem. Rev., 2017, 117, 13230–13319; (b) S. Tang, Y. Liu and A. Lei, Chem, 2018, 4, 27–45; (c) P. Xiong and H.-C. Xu, Acc. Chem. Res., 2019, 52, 3339–3350; (d) L. Ackermann, Acc. Chem. Res., 2020, 53, 84–104; (e) J. C. Siu, N. K. Fu and S. Lin, Acc. Chem. Res., 2020, 53, 547–560; (f) Y. Yu, P. Guo, J.-S. Zhong, Y. Yuan and K.-Y. Ye, Org. Chem. Front., 2020, 7, 131–135; (g) C. Ma, P. Fang, Z. Liu, S. Xu, K. Xu, X. Cheng, A. Lei, H. Xu, C. C. Zeng and T.-S. Mei, Sci. Bull., 2021, 66, 2412–2429; (h) C. Xu, A.-W. Lei, T.-S. Mei, H.-C. Xu, K. Xu and C.-C. Zeng, CCS Chem., 2021, 4, 1120–1152; (i) Z. Tan, H. Zhang, K. Xu and C.-C. Zeng, Sci. China: Chem., 2024, 67, 450–470; (j) H. Zhou, H.-T. Tan and W.-M. He, Chin. J. Catal., 2023, 46, 4–10.
17. (a) X. Kong, Y. Liu, L. Lin, Q. Chen and B. Xu, Green Chem., 2019, 21, 3796–3801; (b) X. Kong, Y. Wang, Y. Chen, X. Chen, L. Lin and Z.-Y. Cao, Org. Chem. Front., 2022, 9, 1288–1294; (c) X. Kong, Y. Chen, X. Chen, Z. Lu, W. Wang, S.-F. Ni and Z.-Y. Cao, Org. Lett., 2022, 24, 2137–2142; (d) X. Kong, X. Chen, Y. Chen and Z.-Y. Cao, J. Org. Chem., 2022, 87, 7013–7021; (e) X. Chen, N.-Z. Wang, Y.-M. Cheng, X. Kong and Z.-Y. Cao, Synthesis, 2023, 2833–2842; (f) X. Kong, Y. Chen, X. Chen, C. Ma, M. Chen, W. Wang, Y.-Q. Xu, S.-F. Ni and Z.-Y. Cao, Nat. Commun., 2023, 14, 6933.
18. H.-D. He, Z.-K. Zhang, H.-B. Tang, Y.-Q. Xu, X.-B. Xu, Z.-Y. Cao, H. Xu and Y. Li, Org. Chem. Front., 2022, 9, 4875–4881.
19. (a) H.-U. Blaser, Science, 2006, 313, 312–313; (b) H.-U. Blaser, H. Steiner and M. Studer, ChemCatChem, 2009, 1, 210–221. For studies on the electrochemical reduction of nitroarenes, please see: (c) F. Z. Haber, Z. Elektrochem. Angew. Phys. Chem., 1898, 5, 235; (d) J. Marquez and D. Pletcher, J. Appl. Electrochem., 1980, 10, 567–573; (e) D. S. Silvester, A. J. Wain, L. Aldous, C. Hardacre and R. G. Compton, J. Electroanal. Chem., 2006, 596, 131–140; (f) S. Won, W. Kim and H. Kim, Bull. Korean Chem. Soc., 2006, 27, 195–196; (g) Y.-Z. Liu, M.-Y. Lin, L.-P. Xiao, K. Zhang and J.-X. Lu, Chin. J. Chem., 2008, 26, 1168–1172; (h) J.-L. Fan, W.-L. Ye, R. Wang, L.-Q. Xu and X.-Q. Wu, J. Electrochem., 2009, 15, 260; (i) S. Wang, X. Xia, Q. Chen, K. Li, X. Xiao and F. Chen, ACS Appl. Mater. Interfaces, 2024, 16(4), 5158–5167; (j) P. Du, J. L. Brosmer and D. G. Peters, Org. Lett., 2011, 13, 4072–4075; (k) A. A. Sokolov, M. A. Syroeshkin, V. N. Solkan, T. V. Shebunina, R. S. Begunov, L. V. Mikhal'chenko, M. Y. Leonova and V. P. Gultyai, Chem. Bull., 2014, 63, 372–380; (l) L. Du, B. Zhang, S. Ji, H. Cai and H. Zhang, Sci. China: Chem., 2023, 66, 534–539; (m) S. Ji, L. Zhao, B. Miao, M. Xue, T. Pan, Z. Shao, X. Zhou, A. Fu and Y. Zhang, Angew. Chem., Int. Ed., 2023, 62, e202304434.
20. (a) K. V. Aken, L. Strekowski and L. Patiny, Beilstein J. Org. Chem., 2006, 2 DOI:10.1186/1860-5397-2-3; (b) R. A. Sheldon, Green Chem., 2007, 9, 1273–1283; (c) R. A. Sheldon, Chem. Commun., 2008, 44, 3352–3356; (d) C. Jimenez-Gonzalez, C. S. Ponder, Q. B. Broxterman and J. B. Manley, Org. Process Res. Dev., 2011, 15(4), 912–917.
21. Y. Liu, H. Wu, Y. Guo, J.-C. Xiao, Q.-Y. Chen and C. Liu, Angew. Chem., Int. Ed., 2017, 56, 15432–15435.
22. D. Louvel, A. Chelagha, J. Rouillon, P.-A. Payard, L. Khrouz, C. Monnereau and A. Tlili, Chem. – Eur. J., 2021, 27, 8704–8708.

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Footnote

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d3gc04528e

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