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Abstract

Without any metal catalyst, an efficient transformation of a variety of sulfonyl hydrazides into the corresponding thiosulfonates mediated by NBS/DABCO under air is developed. The method utilizes mild reaction conditions, affords moderate to good yields of product, and tolerates a broad substrate scope. A plausible mechanism is proposed for the decomposition of the sulfonyl hydrazides and the construction of S(O₂)–S bonds to form thiosulfonates.

Keywords

metal-free NBS/DABCO sulfonyl hydrazides synthesis thiosulfonates

Introduction

Thiosulfonates play key roles in pharmaceuticals and possess rich biological activities such as antimicrobial, antiviral, and fungicidal.^1–8 Owing to the wide applications of thiosulfonates, a variety of approaches have been developed for their preparation. The most common approaches for establishing the S–S bonds of thiosulfonates mainly include the oxidation of disulfides/mercaptans^9–15 and the sulfuration of sulfinic acid salts.^16–19 To synthesize unsymmetrical thiosulfonates, sulfonyl chlorides, sulfinyl chlorides, sulfinates, or sulfonyl hydrazides are commonly reacted with disulfides or mercaptans in the presence of a metal catalyst and an oxidant (Scheme 1(a)).^18–22 To synthesize symmetrical thiosulfonates, in the last 15 years, the direct oxidation and coupling of disulfides or mercaptans has been highly favored (Scheme 1(b)).^9,23,24 However, many of these methods suffer from harsh reaction conditions involving the use of strong oxidizing agents and toxic catalysts, and give low yields with numerous byproducts. Sulfonyl hydrazides possess a number of advantages such as easily availability, stability, and low sensitivity to air.^25–27 In the past 3 years, they have attracted the attention of chemists for the preparation of symmetrical thiosulfonates by cleaving S–N bonds to construct S–S bonds. In 2017, Li et al.¹⁴ reported that sulfonyl hydrazides underwent decomposition and were transformed into thiosulfonates with Pd/ZrO₂ as the catalyst and O₂ as the oxidant under visible light at ambient temperature for 24 h (Scheme 1(c)). In 2018, Wei et al.²⁸ showed that thiosulfonates could be obtained from sulfonyl hydrazides using K₂S₂O₈ as a stoichiometric oxidant (Scheme 1(c)). In 2020, Kim et al.²⁹ reported that sulfonyl hydrazides were transformed to thiosulfonates in the absence of an oxidant at 90 °C for 15 h (Scheme 1(c)). Recently, Lv et al.³⁰ described that symmetrical/unsymmetrical thiosulfonates could be prepared from sulfonyl hydrazides using versatile heteropoly acid H₃PMo₁₂O₄₀ as a catalyst at 90 °C for 3 h in CH₃NO₂ (Scheme 1(d)). Nevertheless, these methods suffer from environmental and economical concerns as they utilize strong oxidants, transition–metal catalysts, high reaction temperatures, and long reaction times, which impede the applicability of these methodologies. Avoiding these drawbacks, we have successfully developed a procedure to symmetrical thiosulfonates from sulfonyl hydrazides in moderate to good yields (57%–88%) using NBS (N-bromosuccinimide)/DABCO (1,4-diazabicyclo[2.2.2]octane) without any metal catalyst at 80 °C for 2 h under air (Scheme 1(e)).

Scheme 1.

Preparation of thiosulfonates.

Results and discussion

p-Tolylsulfonyl hydrazide (1a)²⁶ was selected to optimize the reaction conditions for the selective synthesis of thiosulfonate 2a. The effects of different additives, bases, and solvents were investigated, and the results are shown in Table 1. First, various additives such as NH₄I, NBS (N-bromosuccinimide), NIS (N-iodosuccinimide), and TBAI (tetra-n-butylammonium iodide) were examined and NBS was found to be the most promising (Table 1, Entries 1–4). Only a trace amount of product was observed in the absence of an additive (Table 1, Entry 5). Second, among all the bases, DABCO proved to be the best since an 81% yield of 2a could be obtained (Table 1, Entries 6–10). Fortunately, only a trace of the byproduct 3a was detected when DABCO was used as the base. However, without any base, a 30% yield of 3a was detected (Table 1, Entry 11). Third, the solvent was optimized and CH₃CN was found to be the most promising (Table 1, Entries 10, and 12–15). When the reaction was carried out under N₂, the yield of 2a decreased but that of 3a increased significantly (Table 1, Entries 10 and 16). This result indicated that the reaction needs O₂ or air. Subsequently, the reaction was run under O₂ and the yield of the product 2a was almost equal to the yield in air (Table 1, Entries 10 and 17). No appreciable yield of 3a was obtained at room temperature, even after 10 h (Table 1, Entry 18). To further improve the yield of 2a, the amounts of NBS and DABCO were investigated (Table 1, Entries 19–22). For NBS, among Entries 10, 19, and 20, 1.5 equiv. ensured the best yield of 2a and there was no advantage gained on increasing the amount. For DABCO, among Entries 10, 21, and 22, 1.0 or 1.5 equiv. offered the same yield of 2a, but the use of 0.5 equiv. led to a decrease in the yield of 2a to 72%. Therefore, the optimum reaction conditions were established as NBS (1.5 equiv.) as the additive, DABCO (1.0 equiv.) as the base, and CH₃CN as the solvent in air at 80 °C for 2 h.

Table 1.

Optimization of the reaction conditions for the synthesis of 2a.^a


Entry	Additive (equiv.)	Base (equiv.)	Solvent	Yield of 2a (%)^b	Yield of 3a (%)^b
1	NH₄I (1.5)	K₂CO₃ (1.0)	CH₃CN	Trace	Trace
2	NBS (1.5)	K₂CO₃ (1.0)	CH₃CN	62	10
3	NIS (1.5)	K₂CO₃ (1.0)	CH₃CN	40	10
4	TBAI (1.5)	K₂CO₃ (1.0)	CH₃CN	34	13
5	none (1.5)	K₂CO₃ (1.0)	CH₃CN	Trace	Trace
6	NBS (1.5)	NaOH (1.0)	CH₃CN	67	10
7	NBS (1.5)	Cs₂CO₃ (1.0)	CH₃CN	71	12
8	NBS (1.5)	Et₃N (1.0)	CH₃CN	60	11
9	NBS (1.5)	Pyridine (1.0)	CH₃CN	65	10
10	NBS (1.5)	DABCO (1.0)	CH₃CN	81	Trace
11	NBS (1.5)	None (1.0)	CH₃CN	20	30
12	NBS (1.5)	DABCO (1.0)	THF	74	Trace
13	NBS (1.5)	DABCO (1.0)	Toluene	70	Trace
14	NBS (1.5)	DABCO (1.0)	1,4-dioxane	63	Trace
15	NBS (1.5)	DABCO (1.0)	H₂O	Trace	Trace
16^c	NBS (1.5)	DABCO (1.0)	CH₃CN	40	17
17^d	NBS (1.5)	DABCO (1.0)	CH₃CN	81	Trace
18^e	NBS (1.5)	DABCO (1.0)	CH₃CN	60	Trace
19^f	NBS (1.0)	DABCO (1.0)	CH₃CN	70	Trace
20^g	NBS (2.0)	DABCO (1.0)	CH₃CN	80	Trace
21^h	NBS (1.5)	DABCO (0.5)	CH₃CN	72	6
22ⁱ	NBS (1.5)	DABCO (1.5)	CH₃CN	80	Trace

Reaction conditions: 1a (1.0 mmol), additive (1.5 equiv.), base (1.0 equiv.), solvent (2 mL), air, 80 °C, 2 h.

Isolated yield.

Under N₂.

Under O₂.

At room temperature for 10 h.

NBS (1.0 equiv.).

NBS (2.0 equiv.).

DABCO (0.5 equiv.).

DABCO (1.5 equiv.).

With optimized conditions in hand, we set out to explore the substrate scope. Several sulfonyl hydrazides with different substituents on the phenyl ring were investigated and the corresponding symmetrical thiosulfonates were obtained in moderate to good yields ranging from 68% to 85% (Table 2, Entries 1–14). The nature of the substituents affected the reaction yields to some degree. Compounds substituted with electron-donating groups (Table 2, Entries 1–3) gave slightly lower yields than those with electron-withdrawing groups (Table 2, Entries 6–8). When electron-donating substituents were attached to the ortho, meta, or para positions of the phenyl ring (Table 2, Entries 2, 9, and 11), the order of the product yields was para > ortho > meta, the same as with electron-withdrawing substituents (Table 2, Entries 6, 10 and 12). Multisubstituted sulfonyl hydrazides gave the corresponding thiosulfonates in good yields (75%–81%) (Table 2, Entries 13 and 14). Moreover, it was noteworthy that naphthyl and benzyl sulfonyl hydrazides also provided the desired products in 76% and 57% yields, respectively, (Table 2, Entries 15 and 16).

Table 2.

Synthesis of thiosulfonates 2 from sulfonyl hydrazides under the optimized conditions.


Entry	Reactant	R	Product^a	Yield (%)^b
1	1a	4-MeC₆H₄	2a	81
2	1b	4-MeOC₆H₄	2b	79
3	1c	4-EtOC₆H₄	2c	76
4	1d	C₆H₅	2d	80
5	1e	4-FC₆H₄	2e	82
6	1f	4-ClC₆H₄	2f	84
7	1g	4-BrC₆H₄	2g	85
8	1h	4-O₂NC₆H₄	2h	80
9	1i	2-MeC₆H₄	2i	77
10	1j	2-ClC₆H₄	2j	75
11	1k	3-MeC₆H₄	2k	72
12	1l	3-ClC₆H₄	2l	68
13	1m	2-Me-3-ClC₆H₃	2m	75
14	1n	2,4,6-MeC₆H₂	2n	81
15	1o	◻1-naphthyl	2o	76
16	1p	C₆H₅CH₂	2p	57

Confirmed by ¹H and ¹³C NMR spectroscopy.

Isolated yield.

A scale-up experiment (20 mmol) of our synthesis provided an 82% yield of 2a and demonstrates the effectiveness of this method.

Scheme 2.

A scale-up experiment.

To further explore the mechanism of the decomposition of the sulfonyl hydrazides and the construction of S(O₂)–S bonds to form thiosulfonates, several control experiments were carried out. First, when adding the radical scavenger TEMPO (1.0 equiv.) to the standard reaction, only a trace amount of the target product 2a was observed (Scheme 3(a)), which suggested that the reaction proceeded through a radical intermediate. Second, when the byproduct disulfide 3a alone was subjected to the standard reaction conditions, a trace amount of product 2a was observed (Scheme 3(b)). Finally, when 1a reacted with 3a under the standard conditions, an 83% yield of thiosulfonate 2a was obtained (Scheme 3(c)), suggesting that disulfide 3a might be an intermediate in this reaction.

Scheme 3.

Control experiments.

Based on these observations and relevant references,^28,31–34 a mechanism can be proposed in Scheme 4. Initially, sulfonyl hydrazide 1 is transformed into sulfinic acid B in the presence of NBS/DABCO via expulsion of HBr and N₂. Next, B can be oxidized to be an oxygen-centered radical C by air upon heating.³⁴ Self-coupling of the radical C can offer the intermediate disulfone D. Subsequently, D can be reduced by B to give the disulfoxide E and sulfonic acid F.³⁴ The unstable intermediate E takes place homolytic cleavage under heating to generate radical G. Finally, G may disproportionate into radicals I and H, which can easily be combined into the target thiosulfonate 2.

Scheme 4.

A plausible mechanism for the formation of 2.

Conclusion

In summary, we have developed an efficient approach for the transformation of a variety of sulfonyl hydrazides into the corresponding thiosulfonates mediated by NBS/DABCO under air without any metal catalyst. The approach provides mild reaction conditions, moderate to good yields of products, and a broad substrate scope. A plausible mechanism has been proposed for the decomposition of the sulfonyl hydrazides and the construction of S(O₂)–S bonds to form the target thiosulfonates. The reaction is limited to only symmetrical thiosulfonates, which should be as a limitation of the methodology.

Experimental

Infrared spectra were determined on a Nicolet Avatar-370 spectrometer in KBr (ν in cm⁻¹). Melting points were measured on a Büchi B-540 capillary melting point apparatus and were uncorrected. Mass spectra (electrospray ionization mass spectrometry (ESI-MS)) were recorded on a Thermo Finnigan LCQ-Advantage. High-resolution mass spectra (ESI-HRMS) were obtained using an Agilent 6210 TOF instrument. ¹H NMR and ¹³C NMR spectra were recorded on a Varian Mercury Plus-400 spectrometer (400 and 100 MHz), δ in parts per million, J in Hertz, using TMS as the internal standard. Signal multiplicity was assigned as singlet (s), doublet (d), and multiplet (m). All analytical reagents were commercially available and used directly without further purification.

Synthesis of thiosulfonates (2a selected as an example); general procedure

A mixture of p-tolylsulfonyl hydrazide (1a) (0.37 g, 2 mmol), NBS (0.53 g, 3.0 mmol), and DABCO (0.22 g, 2 mmol) in CH₃CN (5 mL) was stirred at 80 °C for about 2.0 h until total consumption of the starting material, as monitored by TLC (petroleum ether/EtOAc = 20:1). The reaction mixture was then washed with brine (20 mL) and extracted with CH₂Cl₂ (2 × 20 mL). The combined organic extract was dried over Na₂SO₄ and concentrated under vacuum. The residue was purified by column chromatography (petroleum ether/EtOAc = 20:1) to afford the product 2a (white solid, 81%, 0.23 g).

S-(p-Tolyl) 4-methylbenzenesulfonothioate²⁰ (2a): White solid; 81%, 0.23 g; m.p. 76–78 °C (lit.²⁰ m.p. 76–77 °C). IR (KBr, cm⁻¹): ν = 1344, 1151. ¹H NMR (400 MHz, DMSO-d₆): δ 7.47 (d, J = 8.2 Hz, 2H), 7.26-7.21 (m, 4H), 7.15 (d, J = 7.8 Hz, 2H), 2.42 (s, 3H), 2.36 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 144.6, 142.1, 140.5, 136.3, 130.3, 129.2, 127.5, 124.6, 21.5, 21.6. MS (ESI): m/z (%) = 279.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₅O₂S₂: 279.0513; found: 279.0520.

S-(4-Methoxyphenyl) 4-methoxybenzenesulfonothioate¹¹ (2b): White solid; 79%, 0.25 g; m.p. 84–85 °C (lit.¹¹ m.p. 84–85 °C). IR (KBr, cm⁻¹): ν = 1341, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 7.51 (d, J = 8.7 Hz, 2H), 7.28 (d, J = 8.4 Hz, 2H), 6.88-6.84 (m, 4H), 3.88 (s, 3H), 3.86 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 163.4, 162.3, 138.2, 134.8, 129.9, 118.8, 114.9, 113.8, 55.8, 55.5. MS (ESI): m/z (%) = 311.0 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₅O₄S₂: 311.0411; found: 311.0419.

S-(4-Ethoxyphenyl) 4-ethoxybenzenesulfonothioate²⁰ (2c): White solid; 76%, 0.26 g; m.p. 89–90 °C (lit.²⁰ m.p. 89 °C). IR (KBr, cm⁻¹): ν = 1344, 1153. ¹H NMR (400 MHz, DMSO-d₆): δ 7.68 (d, J = 8.8 Hz, 2H), 7.48 (d, J = 8.0 Hz, 2H), 7.28 (d, J = 8.0 Hz, 2H), 7.14 (d, J = 8.8 Hz, 2H), 4.09-4.05 (m, 4H), 1.34-1.29 (m, 6H). ¹³C NMR (100 MHz, DMSO-d₆): δ 163.7, 158.3, 131.2, 130.1, 129.0, 124.1, 115.8, 114.9, 64.8, 64.7, 14.5, 14.4. MS (ESI): m/z (%) = 339.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₆H₁₉O₄S₂: 339.0725; found: 339.0734.

S-Phenyl benzenesulfonothioate¹² (2d): White solid; 80%, 0.20 g; m.p. 39–41 °C (lit.¹² m.p. 39–41 °C). IR (KBr, cm⁻¹): ν = 1342, 1151. ¹H NMR (400 MHz, DMSO-d₆): δ 7.76-7.73 (m, 1H), 7.61-7.55 (m, 5H), 7.46-7.41 (m, 2H), 7.36-7.32 (m, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 142.7, 136.6, 134.6, 132.2, 129.8, 129.6, 127.8, 127.4. MS (ESI): m/z (%) = 251.0 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₁₁O₂S₂: 251.0200; found: 251.0207.

S-(4-Fluorophenyl) 4-fluorobenzenesulfonothioate¹² (2e): White solid; 82%, 0.22 g; m.p. 70–71 °C (lit.¹² m.p. 70 °C). IR (KBr, cm⁻¹): ν = 1341, 1153. ¹H NMR (400 MHz, DMSO-d₆): δ 7.67-7.62 (m, 2H), 7.47-7.38 (m, 4H), 7.30-7.25 (m, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 166.6 (d, J_C-F = 84.2 Hz), 163.4 (d, J_C-F = 81.2 Hz), 138.4 (d, J_C-F = 9.4 Hz), 138.0 (d, J_C-F = 2.8 Hz), 131.1 (d, J_C-F = 10.1 Hz), 123.4 (d, J_C-F = 3.2 Hz), 117.5 (d, J_C-F = 22.3 Hz), 117.2 (d, J_C-F = 23.1 Hz). ¹⁹F NMR (375 MHz, DMSO-d₆): δ = −102.6, −106.9. MS (ESI): m/z (%) = 287.0 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉F₂O₂S₂: 287.0012; found: 287.0019.

S-(4-Chlorophenyl) 4-chlorobenzenesulfonothioate¹² (2f): White solid; 84%, 0.28 g; m.p. 134–136 °C (lit.¹² m.p. 134–136 °C). IR (KBr, cm⁻¹): ν = 1345, 1153. ¹H NMR (400 MHz, DMSO-d₆): δ 7.72 (d, J = 8.7 Hz, 2H), 7.49 (d, J = 8.7 Hz, 2H), 7.36-7.30 (m, 4H).^{12
¹³}C NMR (100 MHz, DMSO-d₆): δ 141.2, 140.4, 138.6, 137.7, 129.8, 129.2, 128.9, 126.1. MS (ESI): m/z (%) = 318.9 ([M]⁺, 75), 322.9 ([M]⁺, 25). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉³⁵Cl₂O₂S₂: 318.9421; found: 318.9429; C₁₂H₉³⁷Cl₂O₂S₂: 322.9362; found: 322.9369.

S-(4-Bromophenyl) 4-bromobenzenesulfonothioate¹² (2g): White solid; 85%, 0.36 g; m.p. 160–161 °C (lit.¹² 160 °C). IR (KBr, cm⁻¹): ν = 1343, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 7.78 (d, J = 8.5 Hz, 2H), 7.71 (d, J = 8.3 Hz, 2H), 7.44 (d, J = 8.5 Hz, 2H), 7.26 (d, J = 8.4 Hz, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 141.7, 137.7, 132.9, 132.2, 129.2, 128.9, 127.1, 126.5. MS (ESI): m/z (%) = 406.8 ([M]⁺, 51), 410.8 ([M]⁺, 49). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉⁷⁹Br₂O₂S₂: 406.8411; found: 406.8418; C₁₂H₉⁸¹Br₂O₂S₂: 410.8370; found: 410.8377.

S-(4-Nitrophenyl) 4-nitrobenzenesulfonothioate¹² (2h): White solid; 80%, 0.29 g; m.p. 181–183 °C (lit.¹² m.p. 181–183 °C). IR (KBr, cm⁻¹): ν = 1345, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 8.37 (d, J = 8.8 Hz, 2H), 8.28 (t, J = 9.2 Hz, 2H), 7.88-7.80 (m, 2H), 7.66 (t, J = 8.8 Hz, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 151.2, 149.8, 137.9, 134.3, 129.4, 127.1, 125.6, 125.2. MS (ESI): m/z (%) = 341.0 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉N₂O₆S₂: 340.9902; found: 340.9909.

S-(2-Methylphenyl) 2-methoxybenzenesulfonothioate¹¹ (2i): Yellowish solid; 77%, 0.24 g; m.p. 39–40 °C (lit.¹¹ m.p. 39–40 °C). IR (KBr, cm⁻¹): ν = 1340, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 7.45-7.39 (m, 2H), 7.33-7.29 (m, 2H), 7.25-7.17 (m, 2H), 7.14-7.06 (m, 2H), 2.68 (s, 3H), 2.17 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 139.0, 138.6, 138.1, 137.8, 133.6, 132.8, 131.7, 130.9, 130.1, 127.0, 126.7, 125.4, 21.5, 21.4. MS (ESI): m/z (%) = 279.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₅O₂S₂: 279.0513; found: 279.0521.

S-(2-Chlorophenyl) 2-chlorobenzenesulfonothioate³³ (2j): White solid; 75%, 0.24 g; m.p. 81–83 °C (lit.³⁵ m.p. 81–83 °C). IR (KBr, cm⁻¹): ν = 1343, 1150. ¹H NMR (400 MHz, DMSO-d₆): δ 7.81-7.76 (m, 2H), 7.61-7.50 (m, 4H), 7.49-7.41 (m, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 139.0, 135.1, 132.9, 132.5, 132.0, 131.4, 130.9, 130.8, 130.6, 128.9, 127.6, 126.3. MS (ESI): m/z (%) = 318.9 ([M]⁺, 75), 322.9 ([M]⁺, 25). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉³⁵Cl₂O₂S₂: 318.9422; found: 318.9429; C₁₂H₉³⁷Cl₂O₂S₂: 322.9362; found: 322.9370.

S-(3-Methylphenyl) 3-methylbenzenesulfonothioate³⁵ (2k): Yellowish solid; 72%, 0.22 g; m.p. 56–58 °C (lit.³⁶ m.p. 56–58 °C). IR (KBr, cm⁻¹): ν = 1341, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 7.77-7.69 (m, 2H), 7.61 (m, 1H), 7.38 (m, 1H), 7.24-7.19 (m, 3H), 7.01 (m, 1H), 2.34 (s, 3H), 2.32 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 140.7, 139.4, 138.4, 134.0, 132.4, 129.6, 128.9, 127.7, 126.7, 126.4, 125.8, 125.3, 21.3, 20.9. MS (ESI): m/z (%) = 279.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₅O₂S₂: 279.0513; found: 279.0520.

S-(3-Chlorophenyl) 3-chlorobenzenesulfonothioate³⁶ (2l): White solid; 68%, 0.22 g; m.p. 97–99 °C (lit.³⁷ m.p. 98–99 °C). IR (KBr, cm⁻¹): ν = 1342, 1150. ¹H NMR (400 MHz, DMSO-d₆): δ 8.20-8.17 (m, 1H), 7.74-7.67 (m, 2H), 7.57-7.49 (m, 2H), 7.27-7.23 (m, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 139.8, 135.3, 133.9, 133.8, 133.5, 131.1, 130.6, 129.1, 127.6, 127.5, 126.4, 125.6. MS (ESI): m/z (%) = 318.9 ([M]⁺, 75), 322.9 ([M]⁺, 25). HRMS (ESI): m/z [M]⁺ calcd for C₁₂H₉³⁵Cl₂O₂S₂: 318.9421; found: 318.9428; C₁₂H₉³⁷Cl₂O₂S₂: 322.9362; found: 322.9371.

S-(3-Chloro-2-methylphenyl) 3-chloro-2-methylbenzenesulfonothioate²⁹ (2m): White solid; 75%, 0.26 g; m.p. 112–113 °C (lit.²⁹ m.p. 112–114 °C). IR (KBr, cm⁻¹): ν = 1342, 1153. ¹H NMR (400 MHz, DMSO-d₆): δ 7.65-7.61 (m, 2H), 7.48-7.41 (m, 2H), 7.16 (d, J = 7.9 Hz, 1H), 7.10 (d, J = 7.6 Hz, 1H), 2.78 (s, 3H), 2.34 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆): δ 142.1, 141.7, 138.1, 136.6, 135.4, 135.1, 134.6, 133.1, 128.5, 128.1, 127.3, 126.3, 18.2, 12.0. MS (ESI): m/z (%) = 347.0 ([M]⁺, 75), 351.0 ([M]⁺, 25). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₃³⁵Cl₂O₂S₂: 346.9734; found: 346.9739; C₁₄H₁₃³⁷Cl₂O₂S₂: 350.9675; found: 350.9682.

S-(2,4,6-Trimethylphenyl) 2,4,6-trimethylbenzenesulfonothioate³⁷ (2n): White solid; 81%, 0.28 g; m.p. 128–130 °C (lit.³⁸ m.p. 128–130 °C). IR (KBr, cm⁻¹): ν = 1342, 1150. ¹H NMR (400 MHz, DMSO-d₆): δ 7.10 (s, 2H), 6.78 (s, 2H), 2.34 (s, 6H), 2.31 (s, 3H), 2.25 (s, 3H), 2.15 (s, 6H). ¹³C NMR (100 MHz, DMSO-d₆): δ 145.1, 142.4, 139.9, 139.3, 139.1, 131.9, 129.8, 123.4, 22.6, 21.6, 21.7, 21.1.MS (ESI): m/z (%) = 335.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₈H₂₃O₂S₂: 335.1139; found: 335.1146.

S-(Naphthalen-1-yl) naphthalene-1-sulfonothioate³⁸ (2o): White solid; 76%, 0.29 g; m.p. 111–113 °C (lit.³⁸ m.p. 111–113 °C). IR (KBr, cm⁻¹): ν = 1341, 1152. ¹H NMR (400 MHz, DMSO-d₆): δ 8.80 (d, J = 8.6 Hz, 1H), 8.08-8.01 (m, 4H), 7.86-7.82 (m, 2H), 7.68-7.60 (m, 3H), 7.50-7.43 (m, 2H), 7.11-7.05 (m, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 138.6, 137.7, 135.3, 134.4, 134.1, 133.7, 131.7, 130.4, 130.1, 129.7, 129.3, 129.0, 128.7, 128.5, 128.4, 128.2, 127.9, 127.5, 124.6, 122.8. MS (ESI): m/z (%) = 351.0 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₂₀H₁₅O₂S₂: 351.0513; found: 351.0521.

S-(Benzyl) phenylmethanesulfonothioate¹² (2p): Yellow oil; 57%, 0.16 g; m.p. 105–107 °C (lit.¹² m.p. 105–107 °C). IR (KBr, cm⁻¹): ν = 1343, 1153. ¹H NMR (400 MHz, DMSO-d₆): δ 7.41-7.35 (m, 4H), 7.33-7.26 (m, 6H), 4.67 (s, 2H), 3.83 (s, 2H). ¹³C NMR (100 MHz, DMSO-d₆): δ 139.6, 133.2, 130.8, 128.7, 128.6, 127.7, 127.1, 125.7, 66.1, 30.2. MS (ESI): m/z (%) = 279.1 ([M]⁺, 100). HRMS (ESI): m/z [M]⁺ calcd for C₁₄H₁₅O₂S₂: 279.0513; found: 279.0519.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The authors are grateful to the Traditional Chinese Medicine Research Projects of Health and Family Planning Commission of Jiangxi Province (nos 2018A312 and 2019A228) for the financial support.

ORCID iD

Xue Li

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A metal-free approach for the synthesis of thiosulfonates from sulfonyl hydrazides

Abstract

Keywords

Introduction

Results and discussion

Conclusion

Experimental

Synthesis of thiosulfonates (2a selected as an example); general procedure

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

References