Effects of remote unsaturated bonds on nucleophilic aromatic substitution in polyfluoroaromatic compounds. Profound effect of a remote carbonyl group

Abstract

Approximate values of the second-order rate constants for fluorine replacement by isopropoxide ion in a series of unsaturated and related saturated 5,6,7,8-tetrafluoro-1,4-bridged naphthalenes have been determined. For 5,6,7,8-tetrafluoro-1,4-dihydro-3,3-dimethyl-1,4-methanonaphthalen-2(3H)-one, the rate constant (extrapolated to 25 °C) is greater than that for 5,6,7,8-tetrafluoro-1,2,3,4-tetrahydro-endo-2-methoxy-3,3-dimethyl-1,4-methanonaphthalene by a factor of 100 with similar rates of reactions at C-6 and -7, rationalised in terms of the field effect of the carbonyl group and the exclusion of regiospecific homoconjugation in the transition state for reaction at C-6. All other systems examined reacted with similar rate constants, irrespective of remote unsaturated or saturated bonds.