Base-Catalyzed Fragmentation of 2,3-Dioxabicycloheptane, the Bicyclic Peroxide Nucleus of Prostaglandin Endoperoxides: Large Secondary Deuterium Kinetic Isotope Effects

Article abstract of DOI:10.1021/ja00318a034

The influence of deuterium substitution on the rates of base-catalyzed rearrangements of 2,3-dioxabicyclo<2.2.1>heptane (1) is examined.The kinetic isotope effect observed previously with 1,4,5,6,7,7-hexadeuterio-1 (k_H/k_D = 7-8) is much larger than that observed with 1-deuterio-1 (k_H/k_D = 3-4) during fragmentation to levulinaldehyde.This reveals a large cumulative secondary deuterium isotope effect which accompanies rate-determining cleavage of the bridgehead C-H bond.Presumably cleavage of the C4-C7 bond also occurs during the rate-determining step and deuterium substitution on these carbons produces large secondary kinetic isotope effects.