STEREOCHEMISTRY OF RADICAL ADDITION OF POLYHALOMETHANES TO BICYCLO[2.2.1]HEPTENYL SYSTEMS

The radical addition of tribromofluoromethane to endo-2-substituted bicyclo [2.2.1] hept-5-enyl systems is shown to give both trans and exo,cis addition products, the relative amounts of each being dependent on the steric nature of the endo-2 substituent. The addition of tribromofluoromethane tobicyclo [2.2.1] hept-5-ene-endo-2,3- dicarboxylic anhydride (10) gives the trans adduct, exo-5-dibromofluoromethyl-endo-6-bromobicyclo[2.2.1]- heptane-endo-2,3-dicarboxylic anhydride (11), and the exo,cis adduct, exo-5-dibromofluoromethyl-evo-6-bromobicyclo[ 2.2.1]heptane-endo-2,3-dicarboxylic anhydride (12), in yields of approximately 40 and 60%, respectively. The temperature-dependent 19F nmr spectra of 12 reflect the steric hindrance to rotation of the dibromofluoromethyl group of this adduct, with peaks for each of the three conformers of this compound being resolved below -30°. The trans adduct gives only one peak in its 19F spectrum. This difference is used to assign structures in a number of systems. The addition of tribromofluoromethane to bicyclo [2.2.1] hept-2-ene gives the trans adduct in greater than 95% yield. © 1969, American Chemical Society. All rights reserved.