Synthesis of Cyclic β-Silylalkenyl Triflates via an Alkenyl Cation Intermediate.

Trimethylsilylalkyne derivatives are transformed into cyclic β-silylalkenyl triflates through cationic cyclization and subsequent trapping of the alkenyl cation by a triflate anion. β-Silylcyclohexenyl triflates and 3-trimethylsilyl-1,4-dihydronaphth-2-yl triflates are generated efficiently using this methodology. These products provide ready access to substituted cyclohexynes, exemplified by a concise total synthesis of β-apopicropodophyllin.