The Inverse Demand Oxa-Diels–Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity

The Diels–Alder
reaction enables introduction of new functionalities
onto the resorcinarene skeleton with simultaneous generation of new
stereogenic centers and expansion of the internal cavity. We present
highly regio- and diastereoselective inverse electron demand oxa-Diels–Alder
reactions of resorcinarene ortho-quinone methide
with benzofuran and indene, each generating 12 new stereogenic centers.
The mechanism and reasons for regioselectivity and diastereoselectivity
were analyzed using theoretical calculations (NBO charges, Fukui functions,
transition state energies, and thermodynamic stability of the products).
Enantiomers were separated, and their configurations were determined
by comparison of experimental and theoretical electronic circular
dichroism spectra.