A 13C nuclear magnetic resonance study of the reversible substituent migration in several 2-acyl and 2-silyl derivatives of tropolone. Troponoid-IV

The energy barrier for the reversible substituent migration was determined for a number of 2-acyl and 2-silyl derivatives of tropolone. The energy barrier is found to be dependent on the nature of the migrating group. Asymmetric monosubstitution on the ring shifts the equilibrium in favor of one dynamic isomer. In the two cases studied (3-bromotropolone and 3-bromotropolone acetate) it is found that the equilibrium is shifted towards the isomer bearing the bromine atom at the 7-position.