Dancing Silanols: Stereospecific Rearrangements of Silanol Epoxides into Silanoxy-Tetrahydrofurans and Silanoxy-Tetrahydropyrans

We have developed highly stereospecific rearrangements of silanol epoxides into 1’-silanoxy-tetrahydrofurans and 1’-silanoxy-tetrahydropyrans. Upon treatment with Ph3CBF4 and NaHCO3 in CH2Cl2, di-substituted trans-epoxide silanols rearrange into products with an erythro configuration; di-substituted cis-epoxide silanols give products with a threo configuration. To our knowledge, this transformation has little literature precedent. Control experiments show that the rearrangement reaction likely proceeds by nucleophilic attack of the proximal silanol oxygen onto the epoxide followed by an intramolecular silyl transfer. We have used these reactions as key steps in the syntheses of (±)-solerone and (±)-muricatacin.