Ruthenium-Catalyzed Oxidative Annulation of 6-Anilinopurines with Alkynes via C-H Activation: Synthesis of Indole-Substituted Purines/Purine Nucleosides

Abstract

Indole-substituted purine nucleobases have been synthesized by Ru-catalyzed oxidative annulation of 6-anilinopurines with internal alkynes that involves C-H activation. Unsymmetrical aryl(alkyl)alkynes led to high regioselectivity. The reaction was also successful with nucleosides by delivering unprotected indole-substituted nucleosides. In the presence of [RuCl < inf > 2 < /inf > (p-cymene)] < inf > 2 < /inf > and copper(II) acetate hydrate [Cu(OAc) < inf > 2 < /inf > H < inf > 2 < /inf > O], in some cases, we have observed two-fold C-H activation products that exhibit fluorescence. A ruthenacycle intermediate was characterized by crystallography, which suggests that the N-1 nitrogen atom of the purine acts as a directing group for the present transformation.