The electrophilic addition of bromine to homobenzonorbornadiene (3) at
10 degrees C led in quantitative yield to the formation of di-anti-br
omo adduct 4. However, high-temperature bromination of 3 in decalin at
150 degrees C followed by repeated chromatography combined with fract
ional crystallization gave us 13 products. Non-rearranged products 5 a
nd 6 have been isolated in 34% yield. The formation of allylic bromina
ted products 8, 9 and 13 (33%) at high temperature have been discussed
in terms of free radical mechanism. 14 and 15 are alcohol compounds w
hich arise from hydrolysis of 8, 9, and 13, respectively. All compound
s have been characterized properly, especially by 200 MHz H-1 NMR and
50 MHz C-13 NMR and by chemical transformations. Furthermore, it has b
een concluded that high temperature bromination of bicyclic systems gi
ves more non-rearranged products. Lf the molecule is more strained, th
e tendency to rearrange decreases as in the case of benzonorbornadiene
. Copyright (C) 1996 Elsevier Science Ltd.