Bridgehead substituents effect on the reactivity of bicyclobutane in its reactions with nucleophiles. A comparison with olefinic systems

The reactivity of bridgehead substituted bicyclobutanes towards nucleophilic attack was compared with that of the analogous vinylic compounds. Ab initio calculations suggest that the substituents exert nearly the same energetic effects on the ground state of the two systems. The observed difference in the reactivity of the two systems stems, therefore, from the different nature of corresponding transition states.