Synthesis of Fluorescent 2-Substituted 6-(Het)aryl-7-deazapurine Bases {4-(Het)aryl-pyrrolo[2,3-d]pyrimidines} by Aqueous Suzuki–Miyaura Cross-Coupling Reactions

A series of 4-(het)aryl-pyrrolo[2,3-d]pyrimidines [6-(het)aryl-7-deazapurine bases] bearing a H, NH2, CH3, F, or Cl group at the 2-position and either H or F at the 5-position (position 7 of 7-deazapurine) were prepared in a single step by the aqueous Suzuki-Miyaura cross-coupling reactions of the corresponding 6-chloro-7-deazapurines with (het)arylboronic acids. Unlike their ribonucleoside derivatives, which are potent cytostatics, the deazapurine bases did not show significant biological activity but most of them exerted bright fluorescence with emission maxima 368-468 nm and high quantum yields up to 0.83.