Cyclization or hydrogen migration: theoretical study and experimental evidence on the reactivities of unsaturated amidyl radicals.
[reaction: see text] Theoretical calculations (B3LYP/6-31G) backed up by deuterated experiments reveal that the N-substituents (R) play a crucial role in determining the reaction pathways of unsaturated amidyl radicals. With the increase of the bulkiness of N-alkyl group, the activation energy for 6-exo cyclization increases steadily, while the activation energy for 1,5-H abstraction remains almost unchanged. Therefore, cyclization occurs exclusively when R is H while 1,5-H migration occurs exclusively when R is t-Bu.
Chen
Qian
Q
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, P. R. China.
Shen
Meihua
M
Tang
Yu
Y
Li
Chaozhong
C