Self-terminating, oxidative radical cyclizations of medium-sized cycloalkynones with inorganic and organic oxygen-centered radicals of type XO•:: the reaction pathway depends on the nature of X

The reaction of various inorganic and organic oxygen-centered radicals of type XO. with cyclodec-5-ynone 6 can be used as a mechanistic probe to study the ease with which X-. acts as a leaving group in self-terminating, oxidative radical cyclizations. It was observed that when X-. has good leaving ability the reaction leads to formation of the bicyclic epoxy ketones 13 and 14, whereas in the other cases a competition between the individual reversible cyclization steps resulted in predominant formation of the spiro ketone 20. The experimental data obtained lead to the suggestion that vinyl radicals could rearrange through 1,2-group migrations.