Palladium-Catalyzed Cross-Coupling Reaction of Arylboronic Acids with Chloroformate or Carbamoyl Chloride

Abstract

The first palladium-catalyzed cross-coupling reaction between substituted arylboronic acids and chloroformate or carbamoyl chloride is described. One-carbon homologation from arylboronic acids was achieved to give corresponding esters or amides in good yields.

cross-coupling reaction - palladium - boronic acid - arylcarboxylic ester - arylcarboxamide

References

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15

General Procedure: m-Tolylboronic acid (82 mg, 0.6 mmol), Pd(PPh₃)₄ (17 mg, 0.015 mmol), Cu₂O (4 mg, 0.028 mmol), K₃PO₄·3H₂O (439 mg, 1.65 mmol) were placed in a flask under Ar atmosphere. Toluene (4 mL) and ethyl chloroformate (50 µL, 0.5 mmol) were added and the reaction mixture was stirred at 80 °C for 24 h. The reaction mixture was allowed to cool to r.t., and H₂O (5 mL) was added. The mixture was then extracted with Et₂O (3 × 10 mL). The combined organic layer was washed with brine (3 × 10 mL), dried over MgSO₄ and concentrated. The residue was chromatographed on silica gel (elution with hexanes-EtOAc = 30:1) to afford the corresponding ethyl arylcarboxylic ester 3a. ¹H NMR (300 MHz, CDCl₃-TMS): δ = 7.70-7.86 (m, 2 H), 7.30-7.35 (m, 2 H), 4.36 (q, J = 7.2 Hz, 2 H), 2.40 (s, 3 H), 1.39 (t, J = 7.2 Hz, 3 H) ppm. EIMS: m/z (%) = 164 (29) [M⁺], 119 (100), 91 (51), 164 (29), 136 (26), 65 (23), 120 (16), 89 (12), 63 (10). IR (neat): 2983, 1719, 1280, 1201, 1107, 1084, 746, 684 cm^-1. Anal. Calcd for C₁₀H₁₂O₂: C, 73.17; H, 7.32; Found: C, 73.03; H, 7.45.