Construction of the Spiro[5.5]undecane Framework through Dearomative <i>ipso</i>-Iodocyclization of 5-(4-(1-Ethoxyethoxy)phenyl)-1-alkynes

A broadly applicable approach to the construction of spiro[5.5]undecanes through dearomative <i>ipso</i>-iodocyclization of 5-(4-(1-ethoxyethoxy)phenyl)-1-alkynes has been developed. The ethoxyethyl group has multiple functions: serving as a protecting group for the preparation of the substrates, being easily removed under the iodocyclization conditions, and suppressing the iodination of the phenolic moiety. This reaction can be performed at room temperature in an open flask using the easy-to-handle iodinating reagent bis(pyridine)iodonium hexafluorophosphate (IPy₂PF₆).