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

Herein, we report a DMAP-catalyzed [4 + 2] annulation reaction of hex-5-en-2-ynoates 1 with electron-poor alkenes 2, which affords exocyclic olefinic cyclohexenes 3 in good yields and excellent regio-, diastereo-, and E/Z selectivities. Distinguished from previous allenoate- or alkynoate-based substrates, hex-5-en-2-ynoates 1 use the β- and ε-carbons for the bond formation, presenting new and regiodivergent C4 synthons for Lewis base-catalyzed annulations.