A new chemoselective synthesis of pyrrolo[2,3-d]pyrimidines (7-deazapurines) bearing two different aryl groups at positions 4 and 5 was developed based on two orthogonal cross-couplings. Starting from 7-benzyl-protected 4-(phenylsulfanyl)-5-iodopyrrolo[2,3-d]pyrimidine, the Pd-catalyzed Suzuki coupling with arylboronic acids proceeded selectively at position 5, followed by the Pd-catalyzed Cu-mediated Liebeskind–Srogl coupling at position 4. A small library of 4,5-diaryl derivatives was prepared.