Regioselective Cross-Coupling of Allylboronic Acid Pinacol Ester Derivatives with Aryl Halides via Pd-PEPPSI-IPent-

Reaction Scheme

Abstract

Palladium-catalyzed direct cross-coupling of aryl chlorides with a wide range of (hetero)aryl lithium compounds is reported. The use of Pd-PEPPSI-IPent or Pd2(dba)3/XPhos as the catalyst allows for the preparation of biaryl and heterobiaryl compounds in high yields under mild conditions (room temperature to 40 �C) with short reaction times.

Substrates

Procedure

Procedure 1: In a dry Schlenk flask Pd-PEPPSI-IPent (5 mol%, 0.015 mmol, 11.9 mg) and the substrate (0.3 mmol) were dissolved in 1 mL of dry toluene and the solution was stirred at the indicated temperature. The corresponding lithium reagent (1.5 equiv) was diluted with THF to reach the concentration of 0.6 M; this solution was slowly added with the indicated flow rate by the use of a syringe pump. After the addition was completed a saturated aqueous solution of NH4Cl was added and the mixture was extracted with ether (3 x 5 mL). The organic phases were combined and dried with anhydrous Na2SO4. Evaporation of the solvent under reduced pressure afforded the crude product that was then purified by column chromatography. Procedure 2: In a dry Schlenk flask Pd2(dba)3 (2.5 mol%, 0.0075 mmol, 6.87 mg) and XPhos(10 mol%, 0.03 mmol, 14.3 mg) were dissolved in toluene, the substrate (0.3 mmol) was added and the solution stirred at the indicated temperature. The corresponding lithium reagent (1.5 equiv) was diluted with THF to reach a concentration of 0.6 M; this solution was slowly added with the indicated flow rate by the use of a syringe pump. After the addition was completed a saturated solution of aqueous NH4Cl was added and the mixture was extracted with ether (3 x 5 mL). The organic phases were combined and dried with anhydrous Na2SO4. Evaporation of the solvent under reduced pressure afforded the crude product that was then purified by column chromatography

Products

Materials

     
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