We examined the scope of this rearrangement reaction with a range of trans (Scheme 2) and cis (Scheme 3) epoxide substrates. Di-substituted trans-epoxide silanols rearranged stereospecifically into erythro silanoxy-tetrahydrofurans. Analogously, di-substituted cis-epoxide silanols gave threo silanoxy-tetrahydrofurans. The silanol groups in products 24 and 56 were removed using TBAF, and X-ray crystallography of the resulting hydroxy-tetrahydrofurans (CCDC 2233480 and CCDC 2233482) allowed us to unambiguously confirm product identity and relative stereochemistry (See Supporting Information, Structural Reasoning and X-ray Crystallography Sections for additional details). In our optimization experiments (Table ), rearranged product formed in good yields with a range of Lewis acids. However, as the substrate complexity increased, we observed that the best yields were obtained with Ph3CBF4, and our optimized reaction protocol involved stirring silanol epoxide substrate with 15 mol% of Ph3CBF4 and 1 equivalent of NaHCO3 in CH2Cl2 for 2 hours. The role of NaHCO3 is not entirely clear, but, in the absence of it, we have seen a loss of up to 20% of the product yield. We hypothesize that it quenches adventitious HBF4 and prevents unproductive decomposition of the Brønsted acid-labile silanol moiety. The functional group compatibility of this rearrangement reaction was quite good; alkyl ethers (Scheme 2, Entries 7-8), aryl ethers (Scheme 2, Entries 3-4), halogenated aryl rings (Scheme 2, Entry 3 and Scheme 3, Entry 5), alkyl bromides (Scheme 3, Entry 6), and terminal epoxides (Scheme 3, Entry 7) were all tolerated under the reaction conditions. We have also scaled this rearrangement reaction from 0.2 mmol to 3.87 mmol (19-fold increase, Scheme 4), without loss of yield or selectivity.