A Copper-Catalyzed Synthesis of Symmetrical Diarylsulfanes

Abstract

A room-temperature, copper-catalyzed synthesis of symmetrical diarylsulfanes has been developed. The reaction proceeds from aryl iodides and elemental sulfur (S₈) by the action of copper(I) salts in the presence of N-ethyl-N-isopropylpropan-2-amine to afford the corresponding diarylsulfanes in good yields.

Key words

S-arylation - copper(I) iodide - diarylsulfanes - sulfur

• References and Notes

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• 19 General Procedure for the Synthesis of Products 2 A mixture of aryl iodide (2 mmol), CuI (0.10 mmol), ligand (1.1 mmol), and S₈ (1.1 mmol) were added to an oven-dried reaction tube equipped with a septum. The reaction tube was evacuated and back-filled with argon. Under a counterflow of argon, EIPA (0.258 g, 2 mmol) and DMSO (2 mL) were added, and the mixture stirred at r.t. for 8 h. After complete disappearance of aryl iodide (monitored by TLC), H₂O (5 mL) was added, and the mixture was extracted with CH₂Cl₂ (3 × 5 mL). The combined organic phases were dried (on MgSO₄) and filtered before evaporation of the solvent. The residue was purified on silica gel, eluting with PE–EtOAc (20:1), to give product 2. Analytical and spectroscopic data for all derivatives, except 2g–i have been reported previously.¹⁹ Bis(2-trifluoromethylphenyl)sulfane (2g) Colorless oil; yield: 0.23 g (71%). IR (KBr): ν_max = 2915, 1591, 1443, 1313, 1264, 1170, 1128, 1034, 756 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 7.24 (2 H, d, ³ J = 8.0 Hz, 2 CH), 7.36–7.44 (4 H, m, 4 CH), 7.74 (2 H, d, ³ J = 7.5 Hz, 2 CH). ¹³C NMR (125.7 MHz, CDCl₃): δ = 123.6 (2 CF₃, q, ¹ J _CF = 272.0 Hz), 126.9 (2 CH, q, ³ J _CF = 5.5 Hz), 127.5 (2 CH), 131.0 (2 C, q, ² J _CF = 30.2 Hz), 132.4 (2 CH), 134.7 (2 CH), 134.8 (2 C, q, ³ J _CF = 5.0 Hz). MS (EI, 70 eV): m/z (%) = 322 [M + 1], 301 (55), 252 (33), 233 (99), 184 (59), 157 (50), 133 (17), 108 (36). Bis(3-trifluoromethylphenyl)sulfane (2h) Colorless oil; yield: 0.26 g (81%). IR (KBr): ν_max = 2928, 1589, 1422, 1316, 1145, 755 cm^–1. ¹H NMR (500 MHz, CDCl₃) δ = 7.46 (2 H, d, ³ J = 7.2 Hz, 2 CH), 7.49–7.55 (4 H, m, 4 CH), 7.62 (2 H, s, 2 CH). ¹³C NMR (125.7 MHz, CDCl₃): δ = 123.6 (2 CF₃, q, ¹ J _CF = 271 Hz), 124.4 (2 CH, q, ³ J _CF = 3.5 Hz), 127.7 (2 CH, q, ³ J _CF = 3.7 Hz), 129.9 (2 CH), 131.9 (2 C, q, ² J _CF = 32.4 Hz), 134.2 (2 CH), 136.2 (2 C). MS (EI, 70 eV): m/z (%) = 322 [M + 1], 301 (26), 233 (69), 184 (35), 157 (40), 133 (11), 108 (25). Bis(4-cyanophenyl)sulfane (2i) Colorless solid; mp 174–176 °C; yield: 0.19 g (80%). IR (KBr): ν_max = 3424, 2370, 2218, 1582, 1482, 818 cm^–1. ¹H NMR (500 MHz, CDCl₃): δ = 7.55 (4 H, d, ³ J = 8.4 Hz, 4 CH), 7.61 (4 H, d, ³ J = 8.4 Hz, 4 CH).¹³C NMR (125.7 MHz, CDCl₃): δ = 110.9 (2 C), 118.1 (2 CN), 126.5 (4 CH), 132.8 (4 CH), 142.1 (2 C). MS (EI, 70 eV): m/z (%) = 236 [M + 1], 204 (14), 166 (11), 134 (100), 107 (30), 90 (51), 82 (15), 75 (24), 69 (45), 63 (46), 57 (16), 51 (16).