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Selective Monoarylation of Acetate Esters and Aryl Methyl Ketones Using Aryl Chlorides

Reaction Scheme

Abstract

A series of palladacyclic precatalysts that incorporate electron-rich di-tert-butylphosphino biaryl ligands is reported. These precatalysts are easily prepared, and their use provides a general means of employing bulky ligands in palladium-catalyzed cross-coupling reactions. The application of these palladium sources to various C-N and C-O bond-forming processes is also described.

Substrates

Procedure

AMIDATION: 24 mL screw-top test tube equipped with a stir bar and Teflon septum was charged with aryl chloride if solid (1.00 mmol, 1.00 equiv) amide (1.05 � 1.20 mmol, 1.05 � 1.20 equiv) tBuBrettPhos-Pd-G3 (8.5 mg, 0.01 mmol, 1 mol %) and tribasic potassium phosphate (297 mg, 1.40 mmol, 1.40 equiv). The tube was evacuated and backfilled with argon. This sequence was repeated a total of three times, after which aryl halide was added by syringe if a liquid, followed by t-butanol (2 mL). Under positive pressure of argon, the Teflon septum was replaced with an unpunctured one and the reaction was placed in a preheated oil bath at 110 �C and stirred for 1.5 h. The reaction was monitored by thin layer chromatography. After completion the reaction was cooled to room temperature and diluted with ethyl acetate (5 mL) and water (5 mL). The phases were separated and the aqueous phase was extracted with ethyl acetate (3x5 mL). The combined organic phases were dried over magnesium sulfate, concentrated with the aid of a rotary evaporator and purified by flash chromatography

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