The effect of the double bond pyramidalization on the mode of the bromination reaction: bromination of benzobicyclononadiene.

The bromination of 6,7,8,9-tetrahydro-5H-5,9-ethenobenzo[a][7]annulene yielded regio- and stereospecifically formed dibromides arising from the alkyl shift where the bromine exclusively attacks the double bond from the endo face of the double bond. DFT calculations on model compounds showed that the pyramidalization of the double bond and steric repulsion caused by the methylene protons are responsible for the stereo- and regioselective addition of bromine.