Gt. Binmore et al., AN EPR AND KINETIC INVESTIGATION OF TRICYCLO[3.1.1.0(3,6)]HEPT-6-YL AND TRICYCLO[3.1.1.0(3,6)]HEPT-6-YLMETHYL RADICALS, Australian Journal of Chemistry, 47(7), 1994, pp. 1285-1293
Tricyclo[3.1.1.0(3,6)]hept-6-yl radicals were generated by bromine abs
traction from 6-bromo-tricyclo[3.1.1.0(3,6)]heptane, and observed by e
.p.r. spectroscopy. In spite of their high ring strain the radicals we
re found not to rearrange readily but to take part in bimolecular comb
ination reactions and to abstract hydrogen from the methylene groups o
f triethylsilane. Similar treatment of 6-bromomethyltricyclo[3.1.1.0(3
,6)]heptane gave tricyclo[3.1.1.0(3,6)]hept-6-ylmethyl radicals, which
rearranged so rapidly that only the product of beta-scission, the 6-m
ethylenebicyclo[3.1.1]hept-3-yl radical, was observed spectroscopicall
y. The rate constant for beta-scission of the tricyclo[3.1.1.0(3,6)]he
pt-6-ylmethyl radical, estimated from e.p.r. experiments and also from
reduction of 6-bromomethyltricyclo[3.1.1.0(3,6)]heptane with tributyl
tin hydride, was found to be >5 x 10(9) s-1 at 298 K.