Catalytic Direct Cross-Coupling of Organolithium Compounds with Aryl Chlorides

Reaction Scheme


Complex, hindered biaryls have been prepared at temperatures ranging from 0�C to room temperature, or with gentle heating. The Pd-PEPPSI-IPent catalyst nicely couples starting materials containing acidic moieties and routinely prepares biaryl derivatives where one or both rings comprising the biaryl are heterocyclic. Ar1=hindered aryl or heteroaryl, Ar2=unactivated aryl or heteroaryl



In a glovebox, an oven-dried vial (3 mL screw-cap threaded) equipped with a stir bar was charged with Pd-PEPPSI-IPr (3.4 mg, 2 mol %) or Pd-PEPPSIIPent (4 mg, 2 mol %), and zinc (II) chloride (1.4 equiv, 47.7 mg, 0.35 mmol). The vial was sealed with a Teflon�-lined screw cap and THF (0.5 mL) was then added via syringe. After stirring at rt for 10 min., the organomagnesium bromide (1.2 equiv, 0.3 mL) was then added and metal-metal exchange occurred with the concurrent formation of MgX2 ppte. After stirring 20 min. at rt, NMP (0.4 mL) and the aryl halide (0.25 mmol) were added; if solid, the aryl halide was dissolved in NMP and then transferred to the vial. The reaction was stirred for the indicated period of time and temperature after which it was diluted with diethyl ether (2 mL) and washed successively with 1 M Na3EDTA (prepared from 1 equiv of EDTA and 3 equiv of NaOH), and brine. After drying over anhydrous Na2SO4, the solvent was removed in vacuo and the residue purified by flash chromatography.



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