No method is compatible with all substrates (Scheme 5B). Subjecting tert-butyldimethylsilyl ether substrate 41 to our reaction conditions was met with unproductive decomposition. We hypothesize that the instability of the TBS group to the strongly basic reaction conditions led to substrate failure. Substrates 42 and 43 also failed to provide product cleanly. In both cases, unproductive competition between exo and endo modes of nucleophilic attack likely led to substrate decomposition.