(S)-1,1′-Bi-2-naphthol

(S)-1,1′-Bi-2-naphthol (BINOL) is a biaryl diol with axial chirality.

• Titanium catalysis. With titanium(IV) isopropoxide it forms a BINOL–Ti complex that catalyses the asymmetric addition of alkynylzinc reagents to unactivated ketones. A titanium(IV) catalyst of (S)-BINOL also gives enantioselective aryl transfer from triaryl(tetrahydrofuran)aluminium reagents to ketones.
  +

  R″C≡C–Zn

  (S)-BINOL, Ti(OiPr)₄

  ⟶

  General reaction: ketone + alkynylzinc → tertiary propargylic alcohol.

• Chiral Lewis acid catalysis. A chiral bis-titanium(IV) oxide is prepared by treating bis(triisopropoxy)titanium oxide with (S)-BINOL. This catalyst activates aldehyde carbonyls and allows the enantioselective allylation of aldehydes with allyltributyltin.
• Chiral phosphoric acids. Phosphoric acids derived from BINOL are used as chiral organocatalysts. These acids catalyse the asymmetric allylboration of aldehydes.
  phosphorylation

  ⟶

  General structure: BINOL → BINOL-derived phosphoric acid.

• Phosphoramidite ligands. An (S)-BINOL-derived phosphoramidite with a rhodium precatalyst effects enantioselective cyclisation of aromatic ketimines by directed C–H bond activation.
  phosphoramidite

  ⟶

  formation

  General structure: BINOL → BINOL-derived phosphoramidite ligand (NMe₂ shown).

• Chiral recognition. BINOL is used to construct chiral fluorescent sensors for the enantioselective recognition of amino alcohols, α-hydroxycarboxylic acids and amino acid derivatives. A BINOL-based bis(naphthylimine) probe responds differently at two emission wavelengths to chiral diamines, amino alcohols and amino acids.