Ruthenium-Catalyzed Regioselective C7–H Arylation of 2-(Het)aryl[1,2,4]triazolo[1,5-a]pyrimidines with Aryl Halides.

Unusual direction of the C–H arylation of 2-(het)aryl[1,2,4]triazolo[1,5-a]pyrimidines with (het)aryl halides under catalysis by ruthenium(II) complexes has been revealed. The reaction involved activation of the C7–H bond rather than the Cα–H bond of the (het)aryl substituent at C2 of the triazolopyrimidine core. The arylation of 2-substituted [1,2,4]triazolo[1,5-a]pyrimidines with (het)aryl bromides afforded a series of 7-(het)aryl derivatives in good yields. [ABSTRACT FROM AUTHOR]