Ag(I)- or Ag(I)-Au(I)-catalyzed cascade annulation of alkynols (5-hexyn-1-ol systems) with α-ketoesters involving a dual activation process (π and σ) has been developed for the first time. This reaction proceeds through cycloisomerization of alkynol to give the 6-endo-enol ether followed by annulation with an α-ketoester to furnish furo[2,3-b]pyran-2-ones in good yields. Chemical structures of all products were rigorously confirmed by single crystal X-ray analysis and analogy.

We report an improved synthetic protocol for hydroxy methyl-derived polysubstituted furans employing Bi(III)-catalyzed dehydrative cycloisomerization of α-hydroxy oxetanyl ketones. This procedure provides rapid access (within 5 min) to highly substituted furans with exceptional functional group diversity, excellent yields, generality, scalability, and operationally simple reaction conditions. Further, it demonstrated the utility of this method in the first enantioselective total synthesis of furyl-hydroquinone-derived biologically potent natural products shikonofurans J, D, E, and C in seven linear steps, starting from readily available building blocks of 2,5-dihydroxy acetophenone and 3-oxetanone employing chiral-phosphoric acid (TRIP)-catalyzed asymmetric prenylation as a key step to induce the chirality.

A full account of our efforts directed towards the synthesis of diarylheptanoid-derived natural products hedycoropyrans that led to the total synthesis of ent-rhoiptelol B is described. In this endeavor, we...