Catalytic Hydrogeriolysis of endo/exo-Amino- or Dimethylaminosubstituted Bicyclo[3. 1. O]hexane and Bicyclo[4. 1. O]heptane

Abstract

The catalytic hydrogenolysis of endo/exo isomers of amino- or dimethylamino-substituted bicyclo[3.1. Olhexane and bicyclo[4.1.O]heptane with Pd-C and Raney Ni catalyst was studied in order to investigate the regioselective behavior of the amino and N, N-dimethylamino groups on the cyclopropane ring hydrogenolysis. When the hydrogenolysis carried out in hexane or pentane, the endo and exo isomers of the bicyclo[3.1.O]hexane and bicyclo[4.1.0]heptane were hydrogenolyzed at the adjacent bond of the substituent, whereas the opposite bond of the substituent was hydrogenolyzed in acetic acid solution. The endo isomers of the bicyclo [3.1. O]hexanamines were hydrogenolyzed readily at the opposite bond accompanied by the synchronous elimination of the subsituent and the exo isomers of the bicyclo[4.1.0]heptanamines were hydrogenolyzed slowly at the opposite bond without elemination of the subsituent. These results show clearly the difference of the role between the amino group and the ammonio group. The amino group adsorbs tightly to the catalyst surface and assists the cleavage of the adjacent bond. In the case of the ammonium compounds, the driving force of the hydrogenolysis is releasing the strain which causes the preferential cleavage of the opposite bond. Furthermore, the synchronous elimination of the endo ammonio group contrihutrs to accelerate the reaction.