propene and a series of seven enophiles using density functional theory at M06‐2X/def2‐
TZVPP. The reaction barrier decreases along the enophiles in the order H2C CH2> HC
CH> H2C NH> H2C CH (COOCH3)> H2C O> H2C PH> H2C S. Thus, barriers drop
in particular, if third‐period atoms become involved in the double bond of the enophile.
Activation‐strain analyses show that this trend in reactivity correlates with the activation …