Palladium-catalyzed couplings to 5-deaza- and 7-deazapurines

Heterocyclic small molecules with a fused 5,6-membered ring, are an important class of compounds possessing notable biological activities. Among this class, the 7H-pyrrolo [2,3-d]pyrimidine and the 5H-pyrrolo[3,2-d]pyrimidine based compounds occupy a particular place due to their very close structural analogy to the basic purine skeleton (these compounds can be viewed as 5-deaza- and 7- deazapurines, respectively). Moreover, they also represent attractive scaffolds for development of analogues by modification of the substitution pattern. One particular simple and efficient way to introduce a variety of substituents around the heterocyclic scaffold is the formation of C-C bonds via metal-catalyzed cross-coupling reactions. An illustration is provided by this short review which will focus mainly on recent examples of 5-deazapurines functionalization involving a palladium transition metal in the C-C bond forming step.