[RuCl₃(H₂O)_n]-Catalyzed Direct Arylations with Bromides as Electrophiles

Abstract

Catalytic amounts of [RuCl₃(H₂O)_n] allow for direct ­arylations via C-H bond functionalization with aryl bromides, ­bearing a variety of important functional groups.

Key words

arene - aryl bromides - C-H bond functionalization - ­regioselectivity - ruthenium

References and Notes

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19

Representative Procedure - Synthesis of 3d (Table 1, Entry 3)
A suspension of 5 (12.6 mg, 0.05 mmol, 5.0 mol%), K₂CO₃ (415 mg, 3.00 mmol), 2-phenylpyridine (160 mg, 1.03 mmol), and 4-bromoacetophenone (438 mg, 2.20 mmol) in anhyd NMP (2.0 mL) was stirred for 22 h at 120 °C under N₂. After the reaction mixture was cooled to ambient temperature, Et₂O (50 mL) and H₂O (40 mL) were added. The separated aqueous phase was extracted with Et₂O (3 × 50 mL). The combined organic layers were washed with H₂O (50 mL) and brine (50 mL), dried over Na₂SO₄, and concentrated in vacuo. The remaining residue was purified by column chromatography on silica gel (n-pentane-Et₂O, 3:1 → 2:1 → 1:1 → 1:2 → 1:3) to yield 3d (361 mg, 90%, mp 200.5-201.5 °C) as a yellow solid. ¹H NMR (300 MHz, CDCl₃): δ = 8.30 (d, J = 5.0 Hz, 1 H), 7.75 (d, J = 8.1 Hz, 4 H), 7.56 (dd, J = 8.6, 6.4 Hz, 1 H), 7.50-7.45 (m, 2 H), 7.31 (dt, J = 7.7, 1.8 Hz, 1 H), 7.18 (d, J = 8.1 Hz, 4 H), 6.94 (ddd, J = 7.5, 4.8, 0.9 Hz, 1 H), 6.86 (d, J = 7.7 Hz, 1 H), 2.56 (s, 6 H). ¹³C NMR (75 MHz, CDCl₃): δ = 197.7, 157.9, 148.7, 146.3, 140.9, 138.3, 135.3, 135.1, 129.8, 129.7, 128.5, 127.8, 126.6, 121.4, 26.5. IR (KBr): 3053, 2919, 1680, 1605, 1268, 958, 809 cm^-1. MS (EI): m/z (%) = 391 (68) [M⁺], 390 (100), 348 (13). HRMS (EI): m/z calcd for C₂₇H₂₁NO₂: 391.1572; found: 391.1550.