Suzuki-Miyaura Cross-Coupling of Potassium Trifluoro(N-methylheteroaryl)borates with Aryl and Heteroaryl Halides

Reaction Scheme

Abstract

A new bulky biarylphosphine ligand (L8) has been developed that allows the Pd-catalyzed C-O cross-coupling of a wide range of aryl halides and phenols under milder conditions than previously possible. A direct correlation between the size of the ligand substituents in the 2�, 4�, and 6� positions of the nonphosphine containing ring and the reactivity of the derived catalyst system was observed. Specifically, the rate of coupling increased with the size of these substituents.

Substrates

Procedure

An oven-dried test tube, which was equipped with a magnetic stir bar and fitted with a teflon screw-cap, was charged with L8 (1.5-7.5 mol %), [(cinnamyl)PdCl]2 (0.5-2.5 mol %), K3PO4 (318 mg, 1.5 mmol), aryl halide (1.0 mmol) and phenol (1.5 mmol). The vessel was evacuated and backfilled with argon (this process was repeated a total of three times) after which toluene and DME were added via syringe (the amount of solvent is specific to each substrate). The solution was stirred at the specified temperature for 16 h after which it was cooled to rt and diluted with ethyl acetate, washed with water, filtered through a pad of silica gel (eluted with diethyl ether), and concentrated under reduced pressure. The crude material was purified by flash chromatography via the Biotage SP4

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Materials

     
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