From: 1,3-Dipolar [3 + 2] cycloaddition reactions of N,C,C-trisubstituted nitrones with ring-acceptor methylenecyclopropanes: a computational study
Substituents
Activation energy (kcal/mol)
Reaction energy (kcal/mol)
4-isomer
5-isomer
R3=–H, R4=–H
+28.9
+16.6
−10.3
−20.9
R3=–OCH3, R4=–CH3
+29.7
+17.6
−10.0
−20.4
R3=–H, R4=–Cl
+29.1
+16.2
−10.4
−22.0