Superbases in Confined Space: Control of the Basicity and Reactivity of the Proton Transfer

Endohedral functionalization of the
molecular cavity of host molecules
is in high demand in many areas of supramolecular chemistry. When
highly reactive species are incarcerated in the confined space of
a molecular cavity, deep changes of their chemical properties are
expected. Here, we show that the superbasic properties of proazaphosphatranes
can be improved in the confined space of the molecular cavity of hemicryptophane
hosts. A general and modular procedure is described to prepare supramolecular
superbases with various cavity sizes. The rate of proton transfer
is strongly dependent on the shape and size of the inner cavity of
the designed superbasic structure. Kinetic and thermodynamic data
are strongly correlated to the space available around the basic center
as revealed by the X-ray molecular structures analyses.