Three-Different-Component (1 + 2 + n)Annulation Reactions: Ionic and Radical Cyclizations.

One-carbon-atom Michael donors are used to initiate convergent and flexible [1+2+3]-hexannulations and [1+2+2]-pentannulations in which the initial nucleophilic carbon atom terminates the reaction sequence in an ionic fashion as an electrophilic center or in a carbon-centered radical fashion as a nucleophilic center. This protocol is used to prepare regiospecifically substituted bicyclic ketones and lactones and a cis-bicyclic tetrahydrofuran