Hosomi-Sakurai Allylation and Related Reactions

Intramolecular allylation of oxocarbenium ions with allylsilanes is valuable for stereoselective synthesis of cyclic ethers. Allylsilanes (15a-c), bearing a hydroxy or trimethylsiloxy group, are convenient reagents for this cyclization. The (la)-promoted reactions of (15a-c) with carbonyls or acetals efficiently afford cyclic 

3 RiSiX-Promoted Reactions of Acetals and Their Precursors 477 1a(10mol%) 

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