Sulfur-Promoted Oxidative Condensation of Chalcones with Unsubstituted Cyanoacetamide in DMSO: Access to 3-Cyanopyrid-2-ones

Synthesis of Masked 2-Pyridones from 1,3-Enynyl Esters via Tandem Gold-Catalyzed Cycloisomerization and Oxidative Nitrogen Insertion

An efficient synthetic method to regioselectively assemble masked 2-pyridones that relies on sequential gold-catalyzed cycloisomerization and phenyliodonium diacetate (PIDA)-mediated oxidative nitrogen insertion from 1,3-enynyl esters in a one-pot, two-step manner is described. The synthetic utility of the cascade protocol was further demonstrated by the 2 mmol scale synthesis of one example and its elaboration to other potentially useful building blocks as well as the late-stage modification of a diverse array of structurally complex bioactive molecules.

Base- and sulfur-promoted oxidative lactonization of chalcone-acetate Michael adducts: access to pyran-2-ones

A cost-effective, practical, straightforward and scalable synthesis of α-pyrones via base- and sulfur-promoted annulation of phenylacetates and chalcones is reported. Generated in situ from the starting components by using dbu as a base catalyst, the Michael adducts underwent a smooth oxidative cyclization into 3,4,6-triaryl-2-pyranones upon heating with DABCO and sulfur in DMSO. Extension to malonate in place of phenylacetates led to 4,6-diaryl-2-pyranone-2-carboxylates.