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Transition-Metal-Free C−S Bond Formation: Synthesis of Polysubstituted Diaryl Sulfides and α‑Thioarylcarbonyl Compounds Liang-Hua Zou,*,†,‡ Cong Zhao,†,‡ Ping-Gui Li,§ Ying Wang,† and Jie Li*,† †

School of Pharmaceutical Sciences, Jiangnan University. Lihu Avenue 1800, 214122 Wuxi, P. R. China The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University. Lihu Avenue 1800, 214122 Wuxi, P. R. China § State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Chemistry for Life Sciences, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China ‡

S Supporting Information *

ABSTRACT: A transition-metal-free protocol for the construction of C−S bonds has been developed. Acetylacetone acts as a new and green aryl source for the synthesis of polysubstituted diarylsulfides bearing a free hydroxy group and a ketone group, which provides a new access to a series of flavonoids containing a thioaryl group. In addition, a series of α-thioarylcarbonyl compounds are obtained in good to excellent yields.

T

active compounds and are valuable intermediates in organic synthesis.12 Therefore, significant progress has been made in the transition-metal-catalyzed synthesis of diarylsulfides,13 in which various aryl reagents were employed, including halides,14 triflates,8 boronic acids,15 diazonium fluoroborates,16 trimethoxysilanes,17 anilines,18 Grignard reagents,19 and so on20 (Figure 2a, right). Very recently, cyclohexanones were also successfully employed for the synthesis of diarylsulfides via iodine-catalyzed oxidative aromatization.21 In addition, the Shimizu group developed a procedure for the synthesis of sulfides through hydrodeoxygenation of sulfoxides using a Pt and MoOx coloaded TiO2 catalyst.22

he formation of C−S bonds represents a key step in the synthesis of a broad range of biologically active molecules and functional materials.1 Particularly, thio-containing 1,3benzothiazoles are essential building blocks, which are widely found in a large number of pharmaceutically active molecules (Figure 1).2 In the past decade, the cross-coupling of thiols with

Figure 1. Representative examples of biologically active molecules containing C−S bonds.

various aryl sources such as aryl halides,3 aryl triflates,4 and aryl boronic acids5 has been extensively developed for the construction of C−S bonds catalyzed by various of metal catalysts. The replacement of thiols with diaryldisulfides and such transformations could also be realized,6 even without the need of transition metals. 7 Beyond that, indium tri(organothiolate),8 thiosulfonates,9 and potassium thioacetate10 were also found to be suitable sulfur reagents.11 Diarylsulfides are a particularly useful class of structural units commonly found in many naturally occurring and biologically © 2017 American Chemical Society

Figure 2. Protocols for the construction of C−S bonds. Received: September 21, 2017 Published: November 7, 2017 12892

DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

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The Journal of Organic Chemistry

various electron-donating or electron-withdrawing substituents were applied to the reaction system to synthesize a series of diarylsulfides. For example, the reaction of substrates with electron-donating substituents such as methyl and methoxyl afforded the corresponding products 3a−c and 3e in good yields ranging from 40% to 72% yields. The substrate without any substituents on the aryl ring yielded product 3f in 60% yield. In addition, substrates with various electron-withdrawing groups also worked well in the procedure, furnishing the desired products 3g−l in acceptable yields. It seems that there is no straightforward correlation between the stereoelectronic properties of the substrate and the reaction efficiency. To further extend the substrate scope, one substrate with a bulky group (naphthyl) was also tested under the conditions, providing product 3m in a rather modest yield of 31% (Scheme 1). Substrates with strong electron-withdrawing

Herein, we report on the transition-metal-free synthesis of diarylsulfides using acetylacetone as a new and green aryl source.23 It is noteworthy that the desired product possessed a hydroxyl group and a ketone group, which provides a synthetic pathway to obtain a series of flavonoids containing a thioaryl group (Figure 2b, right). Furthermore, we unexpectedly found that a broad range of α-thioarylcarbonyl compounds could be efficiently synthesized under the same conditions (Figure 2b, left), which were previously synthesized in the presence of a copper catalyst (Figure 2a, left).24 The initial screening and optimization of the reaction conditions were conducted with di-p-tolyldisulfide (1a) and acetylacetone (2a) as substrates (Table 1). Using 1a and 2a in a Table 1. Optimization of the Reaction Conditions for the Synthesis of Diarylsulfide 3aa

Scheme 1. Substrate Scope for the Metal-Free Synthesis of Diarylsulfidesa entry

base

solvent

yield (%)b

1 2 3 4 5 6 7 8 9 10 11 12

Cs2CO3 KOtBu NaOtBu Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 Cs2CO3 K2CO3

CH3CN CH3CN CH3CN CH3CN DMF DMSO dioxane HFIP toluene TFE CH3CN CH3CN

45 (39c) 31 (41d) 0 54e 46e 26e 9e 0e 0e 0e 70f (33g, 51h) 49f

a

General conditions: 1a (0.25 mmol), 2a (2.5 mmol), base (0.5 mol), solvent (2.0 mL), adding components under an air atmosphere, 130 °C, 24 h. bIsolated yield (based on 1a). cUnder an argon atmosphere. d 3.0 equiv of base. e20 equiv of 2a and 4 equiv of base. f20 equiv of 2a and 6 equiv of base. g100 °C. h140 °C. HFIP = 1,1,1,3,3,3-hexafluoro2-propanol. TFE = trifluoroethanol.

a

General conditions: 1a (0.25 mmol), 2a (5.0 mmol), base (1.5 mol), CH3CN (2.0 mL), 130 °C, 24 h.

1:10 ratio (on a 0.25 mmol scale), Cs2CO3 (2 equiv) as a base, and CH3CN as a solvent, product 3a was obtained in 45% yield at 130 °C (Table 1, entry 1).25 While adding components under an argon atmosphere, the reaction gave a lower yield (Table 1, entry 1). Next we tried to use other bases such as KOtBu and NaOtBu, but the reaction with the former led to a lower yield; the latter was ineffective (Table 1, entries 2 and 3). The yield was increased to 54% when the loadings of 2a and Cs2CO3 were extended to 20 equiv and 4 equiv, respectively (Table 1, entry 4). Subsequently, various solvents were tested for their influence on the reaction behavior (Table 1, entries 5− 10), and the results showed that CH3CN was the best solvent for this reaction. Finally, the yield was increased to 70% when 20 equiv of 2a and 6 equiv of Cs2CO3 were employed in the reaction (Table 1, entry 11). When performing the reaction at a lower or higher temperature, the yield was dropped to 33% and 51% yields, respectively (Table 1, entry 11). Using a cheap base such as K2CO3 instead of Cs2CO3, the reaction proceeded well but provided 3a in a lower yield (Table 1, entry 12). With the optimized reaction conditions in hand (see entry 11, Table 1), the scope of the reaction of diaryldisulfides with acetylacetone (2a) was investigated. Many substrates with

substituents, such as CN, NO2, and CO2Me, were also tested, but no desired products were obtained, as was also observed when utilizing dialkylsulfides. Here, substrate 1n bearing a cyano group (−CN) was an exception, and a deacetylated product 3n was obtained in 69% yield, which underwent an intermolecular cyclization, followed by a decarbonylation. Next, 1,3-diketone compounds were varied, and substrates 2b and 2c served as reaction partners to react with a series of diaryldisulfides. Interestingly, the reaction did not provide cyclized diarylsulfides as expected products; however, the reaction gave the corresponding α-thioarylcarbonyl compounds. Subsequently, the scope of the metal-free reaction for the synthesis of α-thioarylcarbonyl compounds was extended (Scheme 2). Substrate 2b was reacted with various diaryldisulfides, providing the corresponding products 4a−h in good to excellent yields ranging from 54% to 93%. It is noteworthy that the reaction of substrate 2a with a reaction partner bearing a methylester group also provided a similar product, 4i, in 55% yield. Interestingly, this compound was reacted with 2b to give two products 4j and 4j′ in 27% and 34% 12893

DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

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The Journal of Organic Chemistry Scheme 2. Substrate Scope for the Metal-Free Synthesis of αThioarylcarbonyl Compoundsa

Scheme 4. Proposed Mechanism for the Synthesis of Polysubstituted Diarylsulfides

Scheme 5. Proposed Mechanism for the Synthesis of αThioarylcarbonyl Compounds

a

General conditions: 1 (0.25 mmol), 2a−c (5.0 mmol), base (1.5 mol), CH3CN (2 mL), 130 °C, 24 h.

yields, respectively, one of which 4j′ might be formed through an ester-exchanging process. In addition, the reaction of 1a with 2c afforded product 4a in a good yield of 53%. To investigate the mechanism, we carried out some control reactions. Initially, we assumed that the reaction might proceed via a reaction of 1a and an intermediate 5; however, a test reaction failed to give the desired product 3a (Scheme 3a).

generates the key intermediate III. Subsequently, nucleophilic substitution and dehydration furnish intermediate V, followed by enolization to afford desired product 3a (Schemes 4). However, substrates 2 bearing an ester group gave the unexpected α-thioarylcarbonyl compounds as the final products rather than polysubstituted diarylsulfides. It seems that a stronger electron-withdrawing substituent on 2 would enhance the activity of the acetyl group to proceed a nucleophilic attack, thus inhibiting the expected dual Aldol condensation process. Take the synthesis of 4i as an example (Scheme 5), intermediate VI was formed in the presence of Cs2CO3, which was subsequently attacked by a nucleophilic species to generate intermediate VII. Finally, desired product 4i was furnished via proto-demetalation. To demonstrate the synthetic utility of the products synthesized by our green protocol, one example using product 3a as the precursor was shown for the synthesis of corresponding flavonoids 7 and 8 containing a thioaryl group (Scheme 6).26 In conclusion, we have developed a transition-metal-free procedure for the formation of C−S bonds, starting from easily available starting materials. A new aryl source, acetylacetone, is

Scheme 3. Control Reactionsa

a

TEMPO = 2,2,6,6-tetramethylpiperidinooxy. DPE = 1,1-diphenylethylene.

Subsequently, radical scavengers TEMPO and DPE were employed in the process (Scheme 3b). The yield dropped a little when 0.2 equiv of TEMPO was used to trap the possible radicals produced in the reaction. To our surprise, no 3a product was obtained when 1.0 equiv of TEMPO was used. When replacing TEMPO with 1.0 equiv of DPE, the reaction also worked well, albeit giving 3a in a slightly lower yield of 62%. Therefore, the reaction might not proceed via a radical process. On the basis of our mechanistic insights, we proposed possible mechanisms for the synthesis of polysubstituted diarylsulfides and α-thioarylcarbonyl compounds successively (Schemes 4 and 5). Initially, intermediate II is formed through dual Aldol condensation. Then intramolecular dehydrogenation

Scheme 6. Application of Compound 3a as the Precursor for the Synthesis of Flavonoidsa

a

Reaction conditions: (a) 4-methoxybenzaldehyde, 14% KOH, EtOH, rt, under an argon atmosphere, 24 h; (b) EtOH, NaOAc, reflux, 24 h; (c) I2, pyridine, 95 °C, under an argon atmosphere, 14 h. PMP = pmethoxyphenyl. 12894

DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

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The Journal of Organic Chemistry

1090, 810; HRMS (ESI-TOF) m/z [M + H]+ calcd for C17H19O3S 303.1055, found 303.1047. Phenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3e): yellow solid, 40.8 mg, 60% yield, mp 56.2−58.6 °C; 1H NMR (400 MHz, CDCl3) δ 9.22 (s, 1H), 7.21 (dd, J = 10.4, 4.7 Hz, 2H), 7.12 (t, J = 7.3 Hz, 1H), 7.06−6.98 (m, 2H), 6.76 (s, 1H), 2.60 (s, 3H), 2.40 (s, 3H), 2.37 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 204.3, 157.9, 147.5, 139.7, 135.5, 129.2, 126.3, 125.8, 125.0, 124.2, 115.1, 32.4, 21.4, 21.3; MS m/z (EI) 272.1 (M+); IR 2998, 1589, 1474, 1359, 1208, 1090; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H17O2S 273.0949, found 273.0940. p-Fluorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3g): yellow solid, 32.6 mg, 45% yield, mp 68.1−70.0 °C; 1H NMR (400 MHz, CDCl3) δ 9.67 (s, 1H), 7.03 (dd, J = 8.8, 5.1 Hz, 2H), 6.92 (t, J = 8.6 Hz, 2H), 6.75 (s, 1H), 2.61 (s, 3H), 2.42 (s, 3H), 2.38 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.3, 161.4 (d, J = 245.6 Hz), 158.4, 147.6, 139.9, 133.8, 128.5 (d, J = 7.9 Hz), 125.1, 123.8, 116.2 (d, J = 22.2 Hz), 115.9, 32.5, 21.7, 21.4; 19F NMR (377 MHz, CDCl3) δ −116.57; MS m/z (EI) 290.1 (M+); IR 2918, 1588, 1485, 1207, 823; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H16O2FS 291.0855, found 291.0847. p-Chlorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3h): yellow solid, 38.3 mg, 50% yield, mp 76.6−78.3 °C; 1H NMR (400 MHz, CDCl3) δ 9.90 (s, 1H), 7.17 (d, J = 8.6 Hz, 2H), 6.95 (d, J = 8.6 Hz, 2H), 6.76 (s, 1H), 2.61 (s, 3H), 2.44 (s, 3H), 2.37 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ 204.4, 159.0, 148.0, 140.2, 134.4, 131.6, 129.2, 127.6, 125.2, 123.6, 115.2, 32.6, 22.0, 21.4; MS m/z (EI) 306.1 (M+); IR 2998, 1589, 1473, 1359, 1208, 1090, 820; HRMS (ESITOF) m/z [M + H]+ calcd for C16H16O2ClS 307.0559, found 307.0552. p-Bromophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3i): yellow solid, 43.8 mg, 50% yield, mp 79.8−82.2 °C; 1H NMR (400 MHz, CDCl3) δ 9.96 (s, 1H), 7.31 (d, J = 8.6 Hz, 2H), 6.89 (d, J = 8.6 Hz, 2H), 6.76 (s, 1H), 2.61 (s, 3H), 2.44 (s, 3H), 2.37 (s, 3H); 13 C NMR (101 MHz, CDCl3) δ 204.4, 159.1, 148.1, 140.3, 135.1, 132.1, 127.8, 125.2, 123.5, 119.3, 115.0, 32.6, 22.0, 21.4; MS m/z (EI) 350.1 (M+); IR 2918, 1612, 1471, 1359, 1207, 1003, 808; HRMS (ESITOF) m/z [M + H]+ calcd for C16H16O2BrS 351.0054, found 351.0054. m-Fluorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3j): yellow solid, 29.7 mg, 41% yield, mp 46.1−47.2 °C; 1H NMR (400 MHz, CDCl3) δ 10.07 (s, 1H), 7.17 (td, J = 8.1, 6.0 Hz, 1H), 6.82 (ddd, J = 9.9, 5.0, 1.6 Hz, 2H), 6.77 (s, 1H), 6.69−6.64 (m, 1H), 2.62 (s, 3H), 2.45 (s, 3H), 2.38 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.5, 163.2 (d, J = 248.2 Hz), 159.3, 148.3, 140.5, 138.4 (d, J = 7.7 Hz), 130.4 (d, J = 8.6 Hz), 125.3, 123.4, 121.7 (d, J = 3.0 Hz), 114.7, 112.9 (d, J = 24.2 Hz), 112.6 (d, J = 21.4 Hz), 32.6, 22.1, 21.4; 19F NMR (377 MHz, CDCl3) δ −111.91; MS m/z (EI) 290.1 (M+); IR 2920, 1575, 1377, 1207, 879, 677; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H16O2FS 291.0855, found 291.0847. m-Chlorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3k): yellow solid, 39.0 mg, 51% yield, mp 49.4−51.8 °C; 1H NMR (400 MHz, CDCl3) δ 10.25 (s, 1H), 7.11 (t, J = 7.8 Hz, 1H), 7.09− 7.04 (m, 1H), 6.98 (t, J = 1.8 Hz, 1H), 6.91−6.87 (m, 1H), 6.76 (s, 1H), 2.61 (s, 3H), 2.45 (s, 3H), 2.37 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.5, 159.6, 148.4, 140.6, 138.2, 135.0, 130.1, 125.8, 125.3, 124.2, 123.3, 114.7, 32.6, 22.3, 21.4; MS m/z (EI) 306.1 (M+); IR 2919, 1573, 1358, 1201, 773, 677; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H16O2ClS 307.0559, found 307.0545. 3,4-Dichlorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3l): yellow solid, 25.5 mg, 30% yield, mp 77.3−78.6 °C; 1H NMR (400 MHz, CDCl3) δ 10.75 (s, 1H), 7.26 (d, J = 8.4 Hz, 2H), 7.08 (d, J = 2.2 Hz, 1H), 6.85 (dd, J = 8.5, 2.2 Hz, 1H), 6.78 (s, 1H), 2.64 (s, 3H), 2.49 (s, 3H), 2.39 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.6, 160.3, 148.8, 140.9, 136.6, 133.2, 130.7, 129.5, 127.6, 125.5, 125.4, 122.8, 114.8, 32.8, 22.7, 21.5; MS m/z (EI) 340.0 (M+); IR 2922, 1455, 1361, 1028, 806; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H15O2Cl2S 341.0170, found 341.0164. 2-Naphthalenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3m): yellow solid, 24.9 mg, 31% yield, mp 56.0−58.2 °C; 1H NMR

designed to synthesize a series of important diarylsulfides bearing a hydroxy group and a ketone group, which can be employed for the synthesis a class of flavonoids containing a thioaryl group. Furthermore, various α-thioarylcarbonyl compounds can be efficiently synthesized under these conditions. Further derivatization of the obtained products to get flavonols and their corresponding products of glycosylation is currently ongoing in our laboratories.

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EXPERIMENTAL SECTION

Representative Procedure for the Synthesis of Diarylsulfides (Synthesis of 3a). Under an air atmosphere, a 25 mL sealed tube equipped with a magnetic stir bar was charged with di-ptolyldisulfide (1a, 61.5 mg, 0.25 mmol) and Cs2CO3 (488.7 mg, 1.5 mmol). After the addition of acetylacetone (5 mmol) and acetonitrile (2 mL) via a syringe, respectively, the tube was sealed by a Tefloncoated screw cap, and the reaction vessel was placed in a preheated device at 130 °C and stirred for 24 h. The reaction mixture was cooled to room temperature and diluted with ethyl acetate. The resulting solution was directly filtered through a filter paper and concentrated under reduced pressure. Purification by column chromatography (using hexane/ethyl acetate = 80:1 as an eluent) provided 3a as a yellow solid in 70% yield (based on 1a, 50.1 mg, 0.175 mmol). Tolyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3a): yellow solid, 50.1 mg, 70% yield, mp 86.9−88.1 °C; 1H NMR (400 MHz, CDCl3) δ 9.17 (s, 1H), 7.01 (d, J = 8.1 Hz, 2H), 6.93 (d, J = 8.3 Hz, 2H), 6.73 (s, 1H), 2.58 (s, 3H), 2.38 (s, 3H), 2.36 (s, 3H), 2.25 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.2, 157.7, 147.2, 139.5, 135.8, 131.8, 129.9, 126.7, 125.0, 124.2, 115.7, 32.4, 21.3, 21.3, 20.9; MS m/z (EI) 286.2 (M+); IR 2918, 1588, 1377, 1254, 1206, 799; HRMS (ESI-TOF) m/z [M + Na]+ calcd for C17H18O2NaS 309.0920, found 309.0920. m-Tolyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3b): yellow solid, 28.6 mg, 40% yield, mp 44.5−46.5 °C; 1H NMR (400 MHz, CDCl3) δ 9.07 (s, 1H), 7.09 (t, J = 7.7 Hz, 1H), 6.93 (d, J = 7.6 Hz, 1H), 6.88 (s, 1H), 6.78 (d, J = 7.9 Hz, 1H), 6.75 (s, 1H), 2.60 (s, 3H), 2.40 (s, 3H), 2.37 (s, 3H), 2.26 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.3, 157.7, 147.4, 139.6, 139.1, 135.2, 129.0, 126.9, 126.7, 125.0, 124.2, 123.3, 115.1, 32.4, 21.4, 21.3 (2C); MS m/z (EI) 286.1 (M+); IR 2981, 1588, 1371, 1205, 853, 774; HRMS (ESI-TOF) m/z [M + H]+ calcd for C17H19O2S 287.1106, found 287.1100. o-Tolyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3c): yellow solid, 51.5 mg, 72% yield, mp 85.1−87.2 °C; 1H NMR (400 MHz, CDCl3) δ 9.14 (s, 1H), 7.14 (d, J = 7.2 Hz, 1H), 7.05−6.94 (m, 2H), 6.77 (s, 1H), 6.51 (dd, J = 7.8, 1.0 Hz, 1H), 2.59 (s, 3H), 2.46 (s, 3H), 2.41 (s, 3H), 2.33 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.3, 158.1, 147.6, 139.6, 135.3, 134.5, 130.3, 126.7, 125.4, 125.2, 124.4, 124.2, 114.6, 32.4, 21.4, 21.2, 20.0; MS m/z (EI) 286.1 (M+); IR 2972, 1587, 1443, 1208, 746, 596; HRMS (ESI-TOF) m/z [M + H]+ calcd for C17H19O2S 287.1106, found 287.1097. o-Fluorophenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3d): yellow solid, 31.9 mg, 44% yield, mp 63.1−65 °C; 1H NMR (400 MHz, CDCl3) δ 9.72 (s, 1H), 7.20−7.08 (m, 1H), 7.06−7.02 (m, 1H), 6.95 (td, J = 7.8, 1.3 Hz, 1H), 6.76 (s, 1H), 6.72 (td, J = 7.8, 1.6 Hz, 1H), 2.61 (s, 3H), 2.43 (s, 3H), 2.40 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.4, 161.2, 158.8 (d, J = 13.1 Hz), 148.0, 140.1, 128.2 (d, J = 1.8 Hz), 127.4 (d, J = 7.6 Hz), 125.2, 124.7 (d, J = 3.5 Hz), 123.8, 122.8 (d, J = 17.0 Hz), 115.6 (d, J = 21.3 Hz), 113.8, 32.5, 21.8, 21.3; 19 F NMR (377 MHz, CDCl3) δ −112.17; MS m/z (EI) 290.1 (M+); IR 2996, 1573, 1467, 1376, 1256, 1210, 1027, 853, 748, 675, 598; HRMS (ESI-TOF) m/z [M + H]+ calcd for C16H16O2FS 291.0855, found 291.0857. p-Methoxyphenyl (2-Hydroxy-3-acetyl-4,6-dimethyl)phenyl Sulfide (3e): yellow solid, 37.8 mg, 50% yield, mp 51.2−52.8 °C; 1H NMR (400 MHz, CDCl3) δ 9.18 (s, 1H), 7.02 (d, J = 8.8 Hz, 2H), 6.75 (d, J = 8.8 Hz, 2H), 6.70 (s, 1H), 3.72 (s, 3H), 2.58 (s, 3H), 2.37 (s, 3H), 2.36 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.3, 158.4, 157.5, 146.9, 139.2, 128.9, 125.9, 124.9, 124.2, 116.7, 114.9, 55.3, 32.4, 21.3, 21.2; MS m/z (EI) 302.1 (M+); IR 2918, 1612, 1473, 1360, 1208, 12895

DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

Note

The Journal of Organic Chemistry (400 MHz, CDCl3) δ 9.51 (s, 1H), 7.76−7.69 (m, 1H), 7.67 (d, J = 8.7 Hz, 1H), 7.61 (d, J = 7.7 Hz, 1H), 7.45−7.33 (m, 3H), 7.16 (dd, J = 8.6, 1.9 Hz, 1H), 6.76 (s, 1H), 2.60 (s, 3H), 2.41 (s, 3H), 2.38 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 204.4, 158.4, 147.8, 139.9, 133.8, 133.0, 131.7, 128.9, 127.8, 127.0, 126.7, 125.6, 125.2, 124.8, 124.2, 124.0, 115.2, 32.5, 21.7, 21.4; MS m/z (EI) 322.2 (M+); IR 2916, 1588, 1376, 1205, 810, 741; HRMS (ESI-TOF) m/z [M + H]+ calcd for C20H19O2S 323.1106, found 323.1098. p-Nitrilephenyl (2-Hydroxy-4,6-dimethyl)phenyl Sulfide (3n): yellow solid, 44.0 mg, 69% yield; 1H NMR (400 MHz, CDCl3) δ 7.51−7.44 (m, 2H), 7.08−7.01 (m, 2H), 6.79 (s, 1H), 6.77 (s, 1H), 6.43 (brs, 1H), 2.34 (s, 3H), 2.31 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 157.6, 143.9, 143.1, 143.1, 132.6, 125.8, 124.0, 118.6, 113.8, 110.1, 109.0, 21.5, 20.8; MS m/z (EI) 255.1 (M+); IR 3415, 2917, 2360, 2224, 1589, 1484, 1307, 1194, 968, 830, 706, 546; HRMS (ESITOF) m/z [M + H]+ calcd for C15H14ONS 256.0796, found 256.0796. Representative Procedure for the Synthesis of α-Thioaryl Carbonyl Compounds (Synthesis of 4a). Under an air atmosphere, a 25 mL sealed tube equipped with a magnetic stir bar was charged with di-p-tolyldisulfide (1a, 61.6 mg, 0.25 mmol) and Cs2CO3 (488.7 mg, 1.5 mmol). After the addition of ethyl acetoacetate (2b, 5 mmol) and acetonitrile (2 mL) via a syringe, respectively, the tube was sealed by a Teflon-coated screw cap, and the reaction vessel was placed in a preheated device at 130 °C and stirred for 24 h. The reaction mixture was cooled to room temperature and diluted with ethyl acetate. The resulting solution was directly filtered through a filter paper and concentrated under reduced pressure. Purification by column chromatography (using hexane/ethyl acetate = 20:1 as an eluent) provided 4a as a yellow liquid in 93% yield (based on 1a, 49.4 mg, 0.235 mmol). Ethyl 2-(p-Tolylthio)acetate (4a): 24 yellow liquid, 49.4 mg, 93% yield; 1H NMR (400 MHz, CDCl3) δ 7.33 (d, J = 8.1 Hz, 2H), 7.11 (d, J = 8.0 Hz, 2H), 4.15 (q, J = 7.1 Hz, 2H), 3.58 (s, 2H), 2.32 (s, 3H), 1.22 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.8, 137.3, 131.2, 131.0, 129.8, 61.4, 37.4, 21.1, 14.1; MS m/z (EI) 210.0 (M+); IR 2922, 1731, 1492, 1261, 1118, 804. Ethyl 2-(4-Methoxyphenylthio)acetate (4b): 27 yellow liquid, 34.5 mg, 61% yield; 1H NMR (400 MHz, CDCl3) δ 7.42 (d, J = 8.7 Hz, 2H), 6.84 (d, J = 8.7 Hz, 2H), 4.14 (q, J = 7.1 Hz, 2H), 3.79 (s, 3H), 3.51 (s, 2H), 1.22 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.9, 159.7, 134.2, 125.0, 114.7, 61.3, 55.3, 38.6, 14.1; MS m/z (EI) 226.1 (M+); IR 2917, 1730, 1493, 1245, 1028, 828. Ethyl 2-(4-Chlorophenylthio)acetate (4c): 24 yellow liquid, 31.0 mg, 54% yield; 1H NMR (400 MHz, CDCl3) δ 7.35 (d, J = 8.6 Hz, 2H), 7.30−7.23 (m, 2H), 4.16 (q, J = 7.1 Hz, 2H), 3.60 (s, 2H), 1.23 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.4, 133.5, 133.2, 131.5, 129.2, 61.7, 36.9, 14.1; MS m/z (EI) 230.1 (M+); IR 2980, 1731, 1476, 1268, 1094, 815. Ethyl 2-(4-Bromophenylthio)acetate (4d): 28 yellow liquid, 57.1 mg, 83% yield; 1H NMR (400 MHz, CDCl3) δ 7.41 (d, J = 8.5 Hz, 2H), 7.27 (d, J = 8.5 Hz, 2H), 4.16 (q, J = 7.1 Hz, 2H), 3.61 (s, 2H), 1.23 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.4, 134.2, 132.1, 131.5, 121.0, 61.7, 36.6, 14.1; MS m/z (EI) 275.1 (M+); IR 2979, 1730, 1473, 1268, 1091, 1007, 810. Ethyl 2-(3-Fluorophenylthio)acetate (4e): yellow liquid, 38.0 mg, 71% yield; 1H NMR (400 MHz, CDCl3) δ 7.30−7.22 (m, 1H), 7.18− 7.07 (m, 2H), 6.91 (td, J = 8.3, 1.8 Hz, 1H), 4.18 (q, J = 7.1 Hz, 2H), 3.65 (s, 2H), 1.24 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.3, 162.8 (d, J = 248.5 Hz), 137.5 (d, J = 7.9 Hz), 130.3 (d, J = 8.5 Hz), 124.8 (d, J = 3.1 Hz), 116.1 (d, J = 23.3 Hz), 113.7 (d, J = 21.2 Hz), 61.7, 36.2, 14.1; 19F NMR (377 MHz, CDCl3) δ −111.92; MS m/z (EI) 214.1 (M+); IR 2981, 1731, 1474, 1263, 1027, 878, 776; HRMS (ESI-TOF) m/z [M + H]+ calcd for C10H12O2FS 215.0542, found 215.0541. Ethyl 2-(3-Chlorophenylthio)acetate (4f): yellow liquid, 43.1 mg, 75% yield; 1H NMR (400 MHz, CDCl3) δ 7.39 (d, J = 1.5 Hz, 1H), 7.30−7.26 (m, 1H), 7.25−7.16 (m, 2H), 4.18 (q, J = 7.1 Hz, 2H), 3.64 (s, 2H), 1.24 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.3, 137.2, 134.7, 130.0, 129.2, 127.6, 127.0, 61.7, 36.3, 14.1; MS m/ z (EI) 230.1 (M+); IR 2980, 1731, 1461, 1128, 1026, 774; HRMS

(ESI-TOF) m/z [M + H]+ calcd for C10H12O2ClS 231.0246, found 231.0236. Ethyl 2-(3,4-Dichlorophenylthio)acetate (4g): 29 yellow liquid, 55.0 mg, 83% yield; 1H NMR (400 MHz, CDCl3) δ 7.49 (d, J = 2.2 Hz, 1H), 7.36 (d, J = 8.4 Hz, 1H), 7.23 (dd, J = 8.4, 2.2 Hz, 1H), 4.18 (q, J = 7.1 Hz, 2H), 3.62 (s, 2H), 1.25 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.1, 135.3, 133.0, 131.2, 131.1, 130.7, 128.9, 61.8, 36.4, 14.1; MS m/z (EI) 265.1 (M+); IR 2980, 1731, 1460, 1266, 1129, 1027, 811. Ethyl 2-(Naphthalenylthio)acetate (4h): 24 yellow liquid, 36.3 mg, 59% yield; 1H NMR (400 MHz, CDCl3) δ 7.85 (d, J = 0.8 Hz, 1H), 7.81−7.72 (m, 3H), 7.50−7.41 (m, 3H), 4.16 (q, J = 7.1 Hz, 2H), 3.73 (s, 2H), 1.20 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.7, 133.7, 132.5, 132.2, 128.6, 128.2, 127.7, 127.6, 127.3, 126.6, 126.1, 61.6, 36.7, 14.1; MS m/z (EI) 246.1 (M+); IR 2917, 1730, 1266, 1130, 1027, 812. 4-(2-Oxo-propylsulfany)-benzoic Acid Methyl Ester (4i): white solid, 30.8 mg, 55% yield; 1H NMR (400 MHz, CDCl3) δ 7.94 (d, J = 8.6 Hz, 2H), 7.31 (d, J = 8.6 Hz, 2H), 3.90 (s, 3H), 3.76 (s, 2H), 2.30 (s, 3H); 13C NMR (101 MHz, CDCl3) δ 202.7, 166.5, 141.7, 130.2, 127.8, 127.0, 52.1, 43.2, 28.0; MS m/z (EI) 224.1 (M+); IR 2956, 1706, 1274, 1111, 756; HRMS (ESI-TOF) m/z [M + H]+ calcd for C11H13O3S 225.0585, found 225.0572. 4-Ethoxycarbonylmethylsulfanyl-benzoic Acid Methyl Ester (4j): colorless liquid, 17.1 mg, 27% yield; 1H NMR (400 MHz, CDCl3) δ 7.95 (d, J = 8.5 Hz, 2H), 7.37 (d, J = 8.5 Hz, 2H), 4.19 (q, J = 7.1 Hz, 2H), 3.90 (s, 3H), 3.72 (s, 2H), 1.24 (t, J = 5.8 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.1, 166.6, 142.1, 130.1, 127.8, 127.2, 61.8, 52.1, 35.1, 14.1; MS m/z (EI) 254.1 (M+); IR 2917, 1715, 1593, 1272, 1109, 844, 759, 670; HRMS (ESI-TOF) m/z [M + H]+ calcd for C12H15O4S 255.0691, found 255.0690. 4-Ethoxycarbonylmethylsulfanyl-benzoic Acid Ethyl Ester (4j′): yellow liquid, 22.8 mg, 34% yield; 1H NMR (400 MHz, CDCl3) δ 8.12−7.89 (m, 2H), 7.47−7.33 (m, 2H), 4.36 (q, J = 7.1 Hz, 2H), 4.19 (q, J = 7.1 Hz, 2H), 3.72 (s, 2H), 1.38 (t, J = 7.1 Hz, 3H), 1.25 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 169.1, 166.1, 141.9, 130.0, 128.1, 127.2, 61.9, 61.0, 35.1, 14.3, 14.1; MS m/z (EI) 268.1 (M+); IR 2981, 1711, 1593, 1269, 1105, 1016, 849, 757, 689; HRMS (ESI-TOF) m/z [M + H]+ calcd for C13H17O4S 269.0848, found 269.0846. Procedure for the Synthesis of Compound 5. Under an air atmosphere, a 25 mL sealed tube equipped with a magnetic stir bar was charged with Cs2CO3 (651.6 mg, 2.0 mmol). After the addition of acetylacetone (2a, 10.0 mmol) and acetonitrile (4 mL) via a syringe, respectively, the tube was sealed by a Teflon-coated screw cap, and the reaction vessel was placed in a preheated device at 130 °C and stirred for 24 h. The reaction mixture was cooled to room temperature and diluted with ethyl acetate. The resulting solution was directly filtered through a filter paper and concentrated under reduced pressure. Purification by column chromatography (using hexane/ethyl acetate = 20:1 as an eluent) provided 5 as a colorless solid in 24% yield (199.8 mg, 1.2 mmol). 1-(2-Hydroxy-4,6-dimethylphenyl)ethanone (5): 30 colorless solid, 199.8 mg, 24 yield; 1H NMR (400 MHz, CDCl3) δ 12.68 (s, 1H), 6.65 (s, 1H), 6.54 (s, 1H), 2.64 (s, 3H), 2.56 (s, 3H), 2.27 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 205.4, 163.5, 146.0, 139.5, 124.5, 119.1, 116.7, 33.2, 24.6, 21.5; MS m/z (EI) 165.1 (M+). Procedure for the Synthesis of 1-[4,6-Dimethyl-2-hydroxy3-(p-tolylthio)]-3-(p-tolyl) Propenone (6). A 50 mL single-necked flask equipped with a magnetic stir bar was charged with 3a (71.6 mg, 0.25 mmol) and a 14% KOH (238.5 mg, 4.25 mmol) alcohol solution under an air atmosphere. After the addition of 4-methoxybenzaldehyde (81.69 mg, 0.6 mmol) dissolved in 4 mL of absolute ethanol, the flask was sealed by a Teflon-coated screw cap, and the solution was stirred for 24 h at room temperature. A yellow spot monitored by TLC appeared. Then drops of dilute HCl were added to achieve a pH of 7, and a large amount of a white solid precipitated. After filtration, the resulting solution was concentrated under reduced pressure, extracted with ethyl acetate, and washed with saturated brine. The organic phase was dried over anhydrous sodium sulfate and concentrated under 12896

DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

Note

The Journal of Organic Chemistry ORCID

reduced pressure. Purification by column chromatography (using hexane/ethyl acetate = 5:1 as an eluent) provided 6 as a yellow solid in 57% yield (57.8 mg, 0.143 mmol). 1-[4,6-Dimethyl-2-hydroxy-3-(p-tolylthio)]-3-(p-tolyl) Propenone (6): yellow solid, 57.8 mg, 57% yield, mp 132.4−134.2 °C; 1H NMR (600 MHz, CDCl3) δ 7.87 (s, 1H), 7.52−7.46 (m, 2H), 7.38 (d, J = 16.0 Hz, 1H), 7.04 (d, J = 8.0 Hz, 2H), 6.99−6.93 (m, 3H), 6.92−6.87 (m, 2H), 6.79 (s, 1H), 3.84 (s, 3H), 2.39 (s, 3H), 2.32 (s, 3H), 2.28 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 196.2, 161.7, 155.7, 145.7, 145.2, 139.2, 135.8, 131.6, 130.3, 129.9, 127.3, 126.6, 125.7, 124.6, 124.3, 114.7, 114.4, 55.4, 21.2, 20.9, 20.1; MS m/z (EI) 404.2 (M+); IR 2920, 1634, 1509, 1269, 1149, 1063, 973, 824; HRMS (ESI-TOF) m/z [M + H]+ calcd for C25H24O3NaS 427.1338, found 427.1338. Procedure for the Synthesis of 5,7-Dimethyl-4′-methoxy-8benzylthio Flavonone (7). A 50 mL single-necked flask equipped with a magnetic stir bar was charged with 6 (101.1 mg, 0.25 mmol) and anhydrous sodium acetate (143.6 mg, 1.75 mmol). After the addition of 15 mL of absolute ethanol, the reaction was refluxed for 24 h at 90 °C and was monitored by TLC until the reaction was completed. Then the resulting solution was concentrated under reduced pressure and purified by column chromatography (using hexane/ethyl acetate = 5:1 as an eluent) to provide 7 as a yellow solid in 85% yield (86.1 mg, 0.213 mmol). 5,7-Dimethyl-4′-methoxy-8-benzylthio Flavonone (7): yellow solid, 86.1 mg, 85% yield, mp 95.3−97.4 °C; 1H NMR (600 MHz, CDCl3) δ 7.03 (d, J = 8.7 Hz, 2H), 6.99 (d, J = 8.2 Hz, 2H), 6.97−6.93 (m, 2H), 6.84−6.75 (m, 3H), 5.31 (dd, J = 12.5, 3.2 Hz, 1H), 3.79 (s, 3H), 2.96 (dd, J = 16.5, 12.5 Hz, 1H), 2.85 (dd, J = 16.5, 3.2 Hz, 1H), 2.65 (s, 3H), 2.47 (s, 3H), 2.29 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 193.4, 163.0, 159.5, 150.5, 142.6, 135.0, 134.0, 130.6, 129.5, 127.3, 127.2, 126.9, 119.0, 118.4, 113.7, 78.3, 55.2, 45.1, 22.9, 22.0, 20.9; MS m/z (EI) 404.2 (M+); IR 2924, 1684, 1513, 1245, 1035, 806, 674. Anal. Calcd for C25H24O3S: C, 74.23; H, 5.98. Found: C, 74.09; H, 6.27. Procedure for the Synthesis of 5,7-Dimethyl-4′-methoxy-8benzylthio Flavone (8). A 50 mL single-necked flask equipped with a magnetic stir bar was charged with 5,7-dimethyl-4′-methoxy-8benzylthio flavonone (7, 101.1 mg, 0.25 mmol) and 3.0 mL of anhydrous pyridine under an argon atmosphere. After the addition of iodine (6.2 mg, 0.26 mmol), the reaction was stirred for 14 h at 95 °C. The reaction mixture was cooled to room temperature, then concentrated under reduced pressure, and purified through column chromatography (using hexane/ethyl acetate = 5:1 as an eluent) to provide product 8 as a yellow solid in 88% yield (89.0 mg, 0.22 mmol). 5,7-Dimethyl-4′-methoxy-8-benzylthio Flavone (8): red solid, 88.7 mg, 88% yield, mp 155.1−156.2 °C; 1H NMR (400 MHz, CDCl3) δ 7.71 (d, J = 8.8 Hz, 2H), 7.11 (s, 1H), 7.03−6.96 (m, 4H), 6.90 (d, J = 8.8 Hz, 2H), 6.62 (s, 1H), 3.84 (s, 3H), 2.88 (s, 3H), 2.54 (s, 3H), 2.24 (s,3H); 13C NMR (101 MHz, CDCl3) δ 180.5, 162.2, 161.7, 157.9, 149.0, 141.9, 135.3, 133.4, 130.0, 129.8, 128.0, 126.7, 123.8, 121.2, 118.7, 114.3, 107.0, 55.4, 22.8, 21.7, 20.9; MS m/z (EI) 403.2 (M+); IR 2918, 2849, 1636, 1510, 1424, 1360, 1243, 1026, 823, 805, 639; HRMS (ESI-TOF) m/z [M + H]+ calcd for C25H23O3S 403.1368, found 403.1369.

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Jie Li: 0000-0002-6912-3346 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work is financially supported by the NSF of the Jiangsu Province (BK20150129 and BK20160160), NSF of China (21602083), Fundamental Research Funds for the Central Universities (JUSRP51703A), and a sponsored program by the Jiangsu Province for the Cultivation of Innovation and Pioneering doctor (1016010241151030). L.Z. appreciates Professor Carsten Bolm (RWTH Aachen University) for his valuable discussion and initial studies on this work in Aachen.

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(1) For selected reviews on the transition-metal-catalyzed formation of C−S bonds, see: (a) Hartwig, J. F. Angew. Chem., Int. Ed. 1998, 37, 2046. (b) Liu, H.; Jiang, X. Chem. - Asian J. 2013, 8, 2546. For selected reviews on the application of C−S bonds in medicinal chemistry, see: (c) Feng, M.; Tang, B.; Liang, S. H.; Jiang, X. Curr. Top. Med. Chem. 2016, 16, 1200. (d) Lee, C.-F.; Liu, Y.-C.; Badsara, S. S. Chem. - Asian J. 2014, 9, 706. For selected reviews on the application of C−S bonds in functional materials, see: (e) Takimiya, K.; Shinamura, S.; Osaka, I.; Miyazaki, E. Adv. Mater. 2011, 23, 4347. (2) Ranjit, S.; Lee, R.; Heryadi, D.; Shen, C.; Wu, J.; Zhang, P.; Huang, K.-W.; Liu, X. J. Org. Chem. 2011, 76, 8999. (3) (a) Fernandez-Rodriguez, M. A.; Shen, Q.; Hartwig, J. F. Chem. Eur. J. 2006, 12, 7782. (b) Fernandez-Rodriguez, M. A.; Shen, Q.; Hartwig, J. F. J. Am. Chem. Soc. 2006, 128, 2180. (c) Zhang, Y.; Ngeow, K. C.; Ying, J. Y. Org. Lett. 2007, 9, 3495. (d) Chen, Y.-J.; Chen, H.-H. Org. Lett. 2006, 8, 5609. (e) Larsson, P. F.; Correa, A.; Carril, M.; Norrby, P. O.; Bolm, C. Angew. Chem., Int. Ed. 2009, 48, 5691. (f) Correa, A.; Carril, M.; Bolm, C. Angew. Chem., Int. Ed. 2008, 47, 2880. (4) (a) Mispelaere-Canivet, C.; Spindler, J. F.; Perrio, S.; Beslin, P. Tetrahedron 2005, 61, 5253. (b) Itoh, T.; Mase, T. Org. Lett. 2004, 6, 4587. (c) Zheng, N.; McWilliams, J. C.; Fleitz, F. J.; Armstrong, J. D.; Volante, R. P. J. Org. Chem. 1998, 63, 9606. (5) (a) Savarin, C.; Srogl, J.; Liebeskind, L. S. Org. Lett. 2002, 4, 4309. (b) Herradura, P. S.; Pendola, K. A.; Guy, R. K. Org. Lett. 2000, 2, 2019. (6) (a) Kumar, S.; Engman, L. J. Org. Chem. 2006, 71, 5400. (b) Taniguchi, N.; Onami, T. J. Org. Chem. 2004, 69, 915. (c) Baldovino-Pantaleon, O.; Hernandez-Ortega, S.; MoralesMorales, D. Adv. Synth. Catal. 2006, 348, 236. (7) For selected examples on the transition-metal-free formations of C−S bonds, see: (a) Kumar, A.; Bhakuni, B. S.; Prasad, C. D.; Kumar, S.; Kumar, S. Tetrahedron 2013, 69, 5383. (b) Sang, P.; Chen, Z.; Zou, J.; Zhang, Y. Green Chem. 2013, 15, 2096. (c) Prasad, C. D.; Sattar, M.; Kumar, S. Org. Lett. 2017, 19, 774. (d) Prasad, C. D.; Balkrishna, S. J.; Kumar, A.; Bhakuni, B. S.; Shrimali, K.; Biswas, S.; Kumar, S. J. Org. Chem. 2013, 78, 1434. (8) Lee, J. Y.; Lee, P. H. J. Org. Chem. 2008, 73, 7413. (9) Yoshida, S.; Sugimura, Y.; Hazama, Y.; Nishiyama, Y.; Yano, T.; Shimizu, S.; Hosoya, T. Chem. Commun. 2015, 51, 16613. (10) Wang, M.; Wei, J.; Fan, Q.; Jiang, X. Chem. Commun. 2017, 53, 2918. (11) For other selected sulfur reagents, see: (a) Gholinejad, M. Eur. J. Org. Chem. 2015, 2015, 4162. (b) Firouzabadi, H.; Iranpoor, N.; Gholinejad, M. Adv. Synth. Catal. 2010, 352, 119. (c) Ma, X.; Yu, L.; Su, C.; Yang, Y.; Li, H.; Xu, Q. Adv. Synth. Catal. 2017, 359, 1649. (12) (a) Caboni, P.; Sammelson, R. E.; Casida, J. E. J. Agric. Food Chem. 2003, 51, 7055. (b) Wang, Y.; Chackalamannil, S.; Hu, Z.; Clader, J. W.; Greenlee, W.; Billard, W.; Binch, H., III; Crosby, G.; Ruperto, V.; Duffy, R. A.; McQuade, R.; Lachowicz, J. E. Bioorg. Med. Chem. Lett. 2000, 10, 2247. (c) Nielsen, S. F.; Nielsen, E. O.; Olsen, G.

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b02384. 1 H, 13C, and 19F NMR spectra for new compounds (PDF) Crystal data for 3a (CIF)

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DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898

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DOI: 10.1021/acs.joc.7b02384 J. Org. Chem. 2017, 82, 12892−12898