Thiourea-Assisted Chiral Bicyclic Imidazole Organocatalysts: Design, Synthesis, and Application in Asymmetric Acylative Desymmetrization of Bisphenols for the Construction of P‑Stereocenters

Thiourea-assisted chiral bicyclic imidazole organocatalysts
were
designed, synthesized, and successfully applied in the asymmetric
acylative desymmetrization of P-prochiral bisphenols. Under mild conditions,
the P-stereogenic products were obtained in high yields (up to 99%
yield) and with high enantioselectivities (up to 99% ee). Most importantly,
the reaction could also achieve satisfactory results under 1 mol %
catalyst loadings. Mechanistic studies showed that the synergistic
effect including the covalent activation of the acyl group by the
nucleophilic imidazole and the noncovalent H-bonding and π-interaction
between the catalyst and substrate was crucial for the efficient construction
of P-stereocenters.