Synthesis of polysubstituted iodobenzene derivatives from alkynylsilanes and 1,3-dienes via diels-alder/oxidation/iodination reaction sequence.

The cobalt-catalyzed Diels-Alder reaction of trimethylsilyl-substituted alkynes with 1,3-dienes led to dihydroaromatic intermediates which were transformed into iodobenzene derivatives. For this transformation, the dihydroaromatic intermediates had to be oxidized and the trimethylsilyl-substituted arene had to undergo a silicon-iodine exchange reaction. For this purpose, a number of oxidizing agents and iodonium sources were tested in order to realize the desired two transformations in a single step. Eventually, the combination of tert-butyl hydroperoxide (TBHP), zinc iodide, and potassium carbonate led to the desired oxidation/iodination in good to excellent yields in a short reaction time at ambient temperatures.