2,6-Diazasemibullvalenes: synthesis, structural characterization, reaction chemistry, and theoretical analysis.
A series of 2,6-diazasemibullvalenes (NSBVs) were synthesized and isolated from the reaction of 1,4-dilithio-1,3-dienes with nitriles via oxidant-induced C-N bond formation. For the first time, the activation barrier and an X-ray crystal structure of a substituted 2,6-diazasemibullvalene were determined. All NSBVs show extremely rapid aza-Cope rearrangement in solution, but the rapid aza-Cope rearrangement is "frozen" in the solid state, as shown by solid-state NMR measurements and X-ray single-crystal structural analysis. Insertion of unsaturated compounds or a low-valent metal center into the NSBV C-N bond gave diverse and interesting ring-expansion products. Theoretical analysis showed that the localized structure is predominant and that the homoaromatic delocalized structure exists as a minor component in the equilibrium.
Beijing National Laboratory for Molecular Sciences, College of Chemistry, Peking University, Beijing 100871, China.
Shaoguang
S
Zhang
Junnian
J
Wei
Ming
M
Zhan
Qian
Q
Luo
Chao
C
Wang
Wen-Xiong
WX
Zhang
Zhenfeng
Z
Xi