A study of the Ir-catalyzed C-H silylation of 6-phenyl-7-deazapurines or -9-deazapurines with trialkylsilanes revealed that this reaction preferentially proceeded via ortho-silylation at the aryl group due to the directing effect of the N1 nitrogen of the deazapurine, rather than C-H silylation at the heterocycle which was only a minor side-reaction. A preparative protocol for the ortho-silylation of aryldeazapurines is. presented.