Addition of diphenylphosphinodithioic acid and thioacetic acid with vinylidenecyclopropanes: reversed regioselectivities

The reaction of vinylidenecyclopropanes 1 with diphenylphosphinodithioic acid produces the adducts 3 in good to high yields in toluene upon heating at 100 °C within 1 h, whereas adducts 5 are obtained in excellent yields in reversed regioselectivity from the reaction of 1 with thioacetic acid under identical conditions. The radical reaction processes have been discussed on the basis of deuterium labeling experiment and the control experiments in the presence of radical inhibitors (TEMPO and BHT) or a proton scavenger (DTBMP).