Table 2. Effect of the substituents on the ene-donor.

^aConditions: toluene, 130 °C, 14 h.

^bIsolated yield.

^c cis-Diastereomer only.

^dDecomposition or polymerization of the aryne intermediates.

^e E/Z-mixture (2.5 : 1).

^fWith R = SiEt₃, 2r′ was obtained in 46% yield at 150 °C at 40 h.

^gIntermolecular Alder-ene reaction with β-pinene (5 equiv.) of 1u provided 2u′ (see ref. 13).