Oxygen Superbases as Polar Binding Pockets in Nonpolar Solvents

摘要

A novel class of chiral superbases derived from the 2,2′-bipyridyl-N,N′-dioxide skeleton are presented. Combined experimental and theoretical data reveal that their proton affinities are on the order of 1050 kJ mol−1, with protonation occurring at the oxygen atoms in a chelating manner. In the free bases, the oxygen atoms form a strongly polar binding site hidden in a hydrophobic envelope formed by the hydrocarbon backbone of the superbases. This chiral molecular structure can entrap polar intermediates or polarized transition structures and stabilize them in nonpolar solvents. Specifically, this mode of catalysis is shown for the coupling of benzaldehyde and allyltrichlorosilane.