Gassman’s Cationic [2 + 2] Cycloadditions Using Temporary Tethers

An intermolecular equivalent of Gassman’s cationic [2 + 2] cycloaddition through the use of temporary tethering is described. Notably, hydrazine and hydroxyamide proved to be robust under the acidic conditions required for the cycloaddition, leading to unique cyclobutane manifolds in a highly regio- and stereoselective manner. This development represents a rare usage of hydrazine and hydroxyamide in the capacity as temporary tethers.