Reaction of chloropyridazin-3(2H)-ones with iodide. Part I. A mechanistic study

In this communication we describe the reactions of 4-chloro-, 5-chloro-, and 4,5-dichloropyridazin-3(2H)-ones with 57% hydrogen iodide or sodium iodide in dimethyl formamide to afford iodopyridazin-3(2H)-ones via nucleophilic substitution followed by hydrodeiodination. The constitution of each product was proven by 1H, 13C and 15N NMR spectroscopic investigations. The mechanism proposal is based on density functional theory calculations on intermediates possibly involved in these transformations.