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.