Enhanced long-range coupling constants in cyclic systems

Abstract

Long-range couplings in the 1,3-dioxan series are reported. A clear demonstration of these couplings is given by preparing symmetrical and unsymmetrical spiro-analogues of the dioxans, to render magnetically identical protons non-identical. Coupling constants found are unusually large for saturated, unstrained systems, and a possible effect of the electronegativity of substituents is discussed.