Catalytic Enantioselective Synthesis of Inherently Chiral Macrocycles by Dynamic Kinetic Resolution

Kinetically fast racemization of chiral substrates through an achiral intermediate and enantioselective functionalization of one of the enantiomeric substrates forms the basis of the dynamic kinetic resolution (DKR) of centrally chiral molecules. We report herein DKR of inherently chiral macrocycles through enantioselective alkylation of one of the two rapidly interconverting conformers. Reaction of heteracalixaromatics with bromomethylarenes in the presence of a catalytic amount of Cinchonine- derived chiral phase transfer catalyst (PTC) affords inherently chiral O- alkylated products in 90%−99% yields with up to 95% enaniomeric excess. Density functional theory calculations indicate that a host−guest-like interaction between the macrocyclic substrate and catalyst effectively differentiates the reactivity of two enantiomers devoid of chiral elements.