[1.3], [3.3] AND TANDEM [1.3]-[3.3] REARRANGEMENTS OF 11-MEMBERED AND 12-MEMBERED TRIENOLIDES

The bis-O-silyl enolates 5 derived from lactones 4 rearrange via a tandem [1.3]-[3.3] mechanism leading to the cyclopentane acids 8, whereas the higher homologue 13 is similarly converted into the cyclodecene 15 by a [1.3] process; by contrast, O-silyl enolates of the less substituted lactones 21 and 25 undergo exclusively [3.3] rearrangements.