Sulfur-Promoted Oxidative Cyclization of Pentan-1-ones: Direct Access to Tetrasubstituted Furans from Deoxybenzoins and Chalcones

Metal-Free Catalytic Synthesis of Tetrasubstituted Furans from α-Hydroxy Ketones and Cyano Compounds

A novel method for the efficient and straightforward synthesis of tetrasubstituted furans is presented, employing a base-catalyzed reaction of α-hydroxy ketones and cyano compounds. The reaction proceeds under relatively mild conditions, utilizes readily available starting materials, and exhibits good functional group tolerance and high yields. Notably, this reaction obviates the need for expensive metal catalysts and introduces crucial functional groups such as amino and cyano moieties. Furthermore, it avoids the prerequisite functionalization of substrates, thereby enhancing atomic economy.

Synthesis of tetrasubstituted furans through a Cu/base-mediated cascade reaction from terminal alkynes and 1,2-diketones

The expeditious construction of tetrasubstituted furans via Cu/base-promoted cascade reactions of terminal alkynes with 1,2-diketones is described. This reaction proceeds smoothly, involving the formation of multiple chemical bonds tolerating a wide range of functional groups. The mechanism underlying these transformations has been thoroughly investigated, suggesting that 1,3-diyne serves as a key intermediate generated in situ through oxidative coupling facilitated by the Cu catalyst.

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.