A new sequence of cationic reactions that converts cyclic silyl acyloins and w-alkynyl acetals to polycyclic enediones is reported. For example, treatment of bis-1, 2-((trimethylsilyl) oxy) cyclobutene and 2-(ethylenedioxy)-5-heptyne with excess boron trifluoride etherate in methylene chloride for 2 days provides 4-acetyl-3, 5, 6, 6a-tetrahydro-6a-methyl-l-(fZH)- pentalenone in 58% yield.“his product is formed via a sequence involving a Mukaiyama ...
