DMAP-Catalyzed\n[4 + 2] Annulation of Hex-5-en-2-ynoates\nwith Electron-Poor Alkenes

Herein, we report a DMAP-catalyzed [4 + 2] annulation\nreaction\nof hex-5-en-2-ynoates <b>1</b> with electron-poor alkenes <b>2</b>, which affords exocyclic olefinic cyclohexenes <b>3</b> in good yields and excellent regio-, diastereo-, and <i>E</i>/<i>Z</i> selectivities. Distinguished from previous allenoate-\nor alkynoate-based substrates, hex-5-en-2-ynoates <b>1</b> use\nthe β- and ε-carbons for the bond formation, presenting\nnew and regiodivergent C<sub>4</sub> synthons for Lewis base-catalyzed\nannulations.