Radicalic Ethoxycarbonylation of 3-Iodopyridazines: An Efficient Access to Tri- and Tetrasubstituted Pyridazines

Introduction of ester groups into positions 4 and 5 of 3-iodopyridazines (1,2) by redox decomposition of the oxyhydroperoxide of ethyl pyruvate in a sulfuric acid/toluene two-phase system affords trifunctional pyridazine building blocks (3,4a) in a single step.3][14] The limited availability of iodopyridazines other than the 3-iodo and easily accessible 6-substituted 3-iodo derivatives, however, restricts the scope of this reaction type for the synthesis of polyfunctional 1,2-diazines.6][17] Here, we wish to report on a facile and convenient access to 3-iodo-4,5-pyridazinedicarboxylic acid diethyl ester and its 6-methyl congener, which were required in our laboratory as key intermediates for the construction of polycyclic condensed systems, by means of radicalic ethoxycarbonylation of the corresponding iodopyridazines.Since the pioneering work of Minisci, 18 nucleophilic carbon-centered radicals, including alkyl, acyl, carbamoyl and alkoxycarbonyl radicals, have found wide application for substitution reactions in π-* Dedicated with best wishes to Prof. Dr. F.