Synthesis and orthogonal functionalization of oxazolo[5′, 4′: 4,5]pyrano[2,3-b]pyridine by intra- and intermolecular Pd-catalyzed direct C-H bond heteroarylation

The construction and subsequent orthogonal functionalization of a hitherto unknown oxazolo[5', 4': 4,5] pyrano[2,3-b] pyridine are reported. A palladium-catalyzed direct C-H bond functionalization methodology was used to build the tricyclic scaffold as well as to achieve the subsequent C-H bond functionalization at the C-2 position of the oxazole unit with various (hetero)aryl iodides. Remarkably, selective C-H construction and functionalization procedures preserve the chorine atom on the pyridine moiety offering a late-stage substitution site to progress drug design.