Ar‐BINMOLs with Axial and sp³ Central Chirality – Characterization, Chiroptical Properties, and Application in Asymmetric Catalysis

Abstract

Abstract 2′‐Hydroxy‐1,1′‐binaphthalene‐2‐(arylmethanol) (Ar‐BINMOLs), a family of new 1,1′‐binaphthalene‐2,2′‐diol derivatives, prepared by a [1,2]‐Wittig rearrangement, are introduced as new chiral molecules for the study of the modes of supramolecular aggregation on the basis of ESI‐MS, NMR spectroscopy, differential scanning calorimetry (DSC), and X‐ray diffractometry. Characterization showed that Ar‐BINMOLs exhibit different characteristics to BINOL and act as supramolecules due to hydrogen bonding and aromatic π–π/C–H ··· π interactions. In particular, CD measurements of chiral and racemic Ar‐BINMOL 2a in solution and the solid state show a strong Cotton effect, which revealed that amplification of chirality was observed because of the formation of a chiral supramolecular oligomer derived from the racemic monomer. To this end, the Ar‐BINMOLs were used as supramolecular auxiliaries to mediate the Michael reaction of anthrone to ( E )‐β‐nitrostyrene and could give the Michael adduct with comparable enantioselectivities. In addition, the Ar‐BINMOLs act as ligands to promote asymmetric 1,2‐addition of diethylzinc to aldehydes, which resulted in excellent yields and enantioselectivities (up to >99.9 % ee ) in the reactions of diethylzinc with a broad range of aromatic aldehdyes.