Synthesis of 1,2,3-Triazole-fused Heterocycles via Palladium Catalyzed Annulation of 5-Iodotriazoles

Increasing attention has recently been directed toward 1,2,3-triazole-containing compounds. With their unique properties and excellent stability, 1,4-disubstituted triazoles are readily accessible via the copper catalyzed azide alkyne cycloaddition (CuAAC). As compounds containing fused triazoles become common in pharmaceutical targets and biologically active substances, new strategies to synthesize this class of molecules are highly desirable. An efficient and highly modular approach toward the synthesis of three different heterocyclic motifs containing fused 1,2,3-triazoles is reported. The synthesis involved a Pd-catalyzed annulation of 5-iodo-1,2,3-triazoles, which were prepared by a Cu(I)-catalyzed cycloaddition of iodoalkynes and azides. This work demonstrates the versatility of iodotriazoles in Heck reactions and in direct arylations.MAS