We first wished to examine the capability of a range of Lewis acids to promote the conversion of silanol aziridine A into amino tetrahydrofuran B (Table ). Our initial investigation was conducted with Sc(OTf)3, a versatile yet fairly strong Lewis acid (Table , Entry 1). Switching to Y(OTf)3 and tropylium tetrafluoroborate shut the reaction down completely (Table , Entries 2-3). With the stronger Lewis acids Ph3CBF4, Bi(OTf)3 and Al(OTf)3, reaction performance was excellent but worse than with Sc(OTf)3 (Table , Entries 4-6). With Sc(OTf)3, product formation in toluene was comparable to that in CH2Cl2, but using THF almost completely shut the reaction down. Thus, cyclization is promoted by a variety of Lewis acids but requires a noncoordinating solvent to be successful.