During our optimization process, in some reactions, we isolated small amounts of a side product which we eventually determined to be a 5-membered cyclic silanediol organomercurial compound. We immediately recognized that such intermediates could be extremely valuable in the construction of the functional-group stereochemical arrays found in carbohydrate and polyketide natural products, and we wondered if we could bias the formation of this product through tuning of reaction conditions (Table ). a Yield estimated from 1 H NMR integration with methyl phenyl sulfone as an internal standard. This turned out not to be as simple a task as we had hoped, but, after some experimentation, we found that 1.75 equivalents of Hg(OTf)2 and 1 equivalent of NaHCO3 in THF at 0 °C gave silanediol 50 in a respectable yield of 80% (Table , Entry 8) . The ratio of Hg(OTf)2 and NaHCO3 was absolutely critical and small changes (Table , Entries 1-5 and 6) led to dramatic variations in yield. Maintaining the reaction temperature at 0 °C was also crucial; increasing the temperature to 10 °C was mildly deleterious (Table , Entry 5) and dropping the temperature to -20 °C (Table 1, Entry 7) was dramatically so.