Vv. Zverev et Va. Vasin, Theoretical study of the structure of radical cations derived from substituted tricyclo[4.1.0.0(2,7)]heptanes, RUSS J G CH, 70(6), 2000, pp. 921-926
The PM3 procedure was applied to analyze charge and spin density distributi
on in radical cations of 1-X-tricyclo[4.1.0.0(2,7)]heptanes (X' = H, CO2Me,
SMe; structure A) and products of their thermal isomerization with complet
ely broken central bicyclobutane C-1-C-7 bond (B), broken peripheral C-1-C-
2 (C) and C-2-C-7 bonds (D), and also 1,3-cycloheptadiene structure (E). Th
e general trend is successive increase in the relative stability of radical
cations in going from structure A to E.