Synthesis of Purines and Related Molecules by Cyclization ­Reactions of Heterocyclic Enamines

Abstract

AbstractA great variety of pharmacologically relevant fluorinated purine analogues are available by cyclization reactions of heterocyclic enamines with 1,3-dielectrophiles. The reactions usually proceed with excellent regioselectivities. As electrophiles, 1,3-diketones, enaminones or 3-chloro-2-en-1-ones were used. Other synthetic strategies are based on inverse-electron-demand Diels–Alder reactions of heterocyclic enamines with triazines. Purine analogues were further functionalized by transition-metal-catalyzed CH-coupling reactions or oxidative cyclizations, giving rise to more complex polycyclic products. Amidino-C-glycosides in their reactions with 1,3-dielectrophiles afforded pyrimidine-C-glycosides. Multicomponent reactions of heterocyclic enamines afforded complex products, including spirocyclic derivatives.1 Introduction2 1,3-Diketones3 Enaminones4 3-Chloro-2-en-1-ones5 Triazines6 Transition-Metal-Catalyzed Functionalizations7 Pyrimidine-C-Nucleosides8 Multicomponent Reactions9 Conclusions