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

Abstract : 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.