Synthesis and 19F and 13C NMR Studies of a Series of 4-Substituted Fluorocubanes: Resonance Dependence of 19F Chemical Shifts in a Saturated System

Article abstract of DOI:10.1021/jo00121a059

The substituent chemical shifts and the carbon-fluorine coupling constants of a range of 4-substituted cubyl fluorides in solvents of varying polarity are presented.Least squares regressional analysis of the data indicates that the fluorine probe, while being somewhat less sensitive to field effects as a result of the low polarizability of the cubane C-F bond, nevertheless responds in the "reverse" manner in agreement with precedents established in other alicyclic systems.The dependence of ¹J(CF) upon electronegativity has been interpreted as evidence for the occurence of ?-induction over four bonds, the longest reported to date.Significantly, resonance parameters are found to be very important in describing the effect of substituents on both the fluorine chemical shifts and the magnitude of the one-bond and four-bond 13C-19F coupling constants.This represents one of the rare occasions that resonance effects have been observed in a fully saturated system in the ground state.A possible mechanism by which these resonance effects may be transmitted is presented.