Pd/Brønsted Acid-Catalyzed Atom-Economical [3 + 3] Annulation of 4-Hydroxycoumarins and Skipped Enynes

Org Lett. 2024 Aug 23;26(33):6961-6965. doi: 10.1021/acs.orglett.4c02215. Epub 2024 Aug 9.

Abstract

We report an unprecedented application of skipped enynes as bis-electrophiles under palladium/Brønsted acid catalysis. A [3 + 3] annulation of skipped enynes with 4-hydroxy coumarins as bis-nucleophiles enables a completely atom-economic synthesis of fused O-heterocycles. The reaction is proposed to proceed via the Pd-catalyzed C-H activation of the skipped enyne leading to a diene, which upon subsequent activation by Pd and an O-nucleophilic attack leads to the regioselective formation of a six-membered heterocyclic ring, with a vinyl substituent.