Palladium-Catalysed Direct Arylation of Heteroaromatics Bearing Unprotected Hydroxyalkyl Functions using Aryl Bromides
Résumé
Heteroaromatics bearing unprotected hydroxyalkyl functions can be arylated using aryl or heteroaryl bromides, via palladium-catalysed carbon-hydrogen bond activation/arylation. Good yields were generally obtained using 0.01-0.5 mol% of the air-stable palladium acetate complex as the catalyst. The nature of the base was found to be crucial for the selectivity of this reaction. Potassium acetate led to the direct arylation products whereas caesium carbonate led to the formation of the ether. This procedure is certainly more atom-economic than other methods for the preparation of such compounds, as no protection/deprotection sequence of the hydroxyalkyl function and no preparation of an organometallic derivative is required.