Abstract Hydrogen iodide in glacial acetic acid has served as a versatile reagent in modifications of chlorophyll and its closely related derivatives, eg pheophorbides and 3- vinylchlorins, to 3-ethyl-porphyrins (HI isomerization) or to 3 1-oxoporphyrins (oxo reaction). Nevertheless, the mechamisms of these important reactions have remained obscure. In this paper, the reaction conditions used by H. Fischer for the HI isomerization and the oxo ...
