New silicon-mediated, sequential ring expansions of n-sized 2-cycloalkenones into hydroxyolefinic n + m + p medium-sized lactones: short synthesis of (-)-phoracantholide-J

reaction: see text] In only four steps from 2-cyclopentenone and 2-cyclohexenone, sequential three- or four-atom and then one- to three-atom ring enlargements produce nine- to 12-membered hydroxyolefinic lactones on a gram scale. 2-Cyclopentenone undergoes this serial 5 + 3 + 2 process to form 10-membered ring natural (-)-phoracantholide-J in six linear steps and 26% overall yield.