Base-Catalyzed Hydrogen Exchange

Abstract

Publisher Summary This chapter focuses on the base-catalyzed hydrogen exchange in heterocyclic compounds. Isotopic hydrogen exchange is becoming a widely employed method for preparing labeled compounds, being unsatisfactory only when the specificity of the process is uncertain and when the label can be replaced is high. A better understanding of the various factors involved in the preparation of labeled compounds as well as the stability of the label under widely different conditions is emphasized in the chapter. The conditions necessary to induce exchange vary widely and may be dictated by structural features. Proton-transfer reactions from heterocyclic compounds provide a favorable situation for the operation of a mechanism of exchange. Heterogeneous methods of exchange often involving expensive catalysts were widely used for incorporating tritium and deuterium into heterocyclic compounds. The isotopic exchange procedure is useful as a diagnostic tool for detection of minute traces of labeled compounds that can be seen in the recently developed method for assay of guanine residues in DNA. Many applications have resulted from studies of base-catalyzed isotope exchange reactions of heterocyclic compounds. Primary kinetic hydrogen isotope effects in the base catalyzed exchange of various heterocyclic compounds are tabulated in the chapter.