Scandium Triflate Catalyzed One-Pot Synthesis of Diaryl Sulfoxides

Abstract

Arenes react smoothly with thionyl chloride in the presence of a catalytic amount of scandium triflate at ambient temperature to afford the corresponding symmetrical diaryl sulfoxides in excellent yields with high regioselectivity.

Key words

scandium reagents - sulfinylation - arenes - aryl sulfoxides

References

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12

Experimental procedure: A mixture of arene (10 mmol), thionyl chloride (6 mmol) and Sc(OTf)₃ (5 mol%) in dichloromethane (15 mL) was stirred at ambient temperature under N₂ atmosphere for an appropriate time (Table). After complete conversion, as indicated by TLC, the reaction mixture was diluted with water (10 mL), neutralized with sat. sodium bicabonate and extracted with dichloromethane (2 × 15 mL). The combined organic layers were dried over anhyd Na₂SO₄, concentrated in vacuo and the resulting product was purified by column chromatography on silica gel (Merck, 100-200 mesh, ethyl acetate-hexane, 2:8) to afford pure diaryl sulfoxides. Spectral data for products:
Di-(3,4-dimethoxyphenyl) Sulfoxide (2b): ¹H NMR (200 MHz, CDCl₃): δ 3.98 (s, 12 H), 6.97 (d, 2 H, J = 8.0 Hz), 7.40 (d, 2 H, J = 2.3 Hz), 7.65 (dd, 2 H, J = 2.3, 8.0 Hz). EIMS: m/z: 336 (M⁺), 321, 293, 155, 69, 57. IR (KBr): 2925, 2855, 1585, 1474, 1359, 1254, 1208, 1033, 840, 778 cm^-1.
Di-(3,4-dimethylphenyl) Sulfoxide (2i): ¹H NMR (200 MHz, CDCl₃): δ 2.40 (s, 12 H), 7.25 (d, 2 H, J = 1.2 Hz), 7.30 (d, 2 H, J = 8.0 Hz), 7.78 (dd, 2 H, J = 1.2 and 8.0 Hz). EIMS: m/z: 258 (M⁺), 240, 226, 169, 141, 105, 77, 43. IR (KBr): 2924, 2853, 1585, 1450, 1325, 1124, 772, 601 cm^-1.
Di-(2-methoxy-1-naphthyl) Sulfoxide (2o): ¹H NMR (200 MHz, CDCl₃): δ 4.0 (s, 6 H), 7.23 (d, 2 H, J = 8.0 Hz), 7.38 (t, 2 H, J = 7.8 Hz), 7.57 (t, 2 H, J = 7.8 Hz), 7.70 (d, 2 H, J = 8.0 Hz), 7.78 (d, 2 H, J = 8.0 Hz), 8.20 (d, 2 H, J = 8.0 Hz). FAB Mass: 362 (M⁺), 346, 192, 177, 149, 126, 114, 63. IR (KBr): 2923, 2845, 1585, 1495, 1430,1355, 1320, 1255, 1210, 1178, 1024, 840 cm^-1.