Chemical Properties
white to light yellow crystal powde
Uses
Chiral binapthol imminium salt precursor. Salts were used for an asymmetric epoxidation of olefins.
Definition
ChEBI: (S)-(-)-1,1'-Bi-2-naphthol is a member of naphthols.
Synthesis
Racemic 1,1'-bi-2-naphthol is resolved via formation of a molecular inclusion complex. The racemate is heated with (S)-proline in acetonitrile under reflux. Upon cooling, a white solid (the molecular inclusion complex) precipitates and is filtered. The white solid is treated with ethanol to give inclusion complex crystals. These crystals are stirred in a two-phase ethyl acetate-water system. After separation, the organic phase is processed to yield enantiopure (S)-product. The acetonitrile filtrate is processed to yield enantiopure (R)-product. The aqueous phase allows recovery of (S)-proline.
Purification Methods
Dissolve it in cold 2.5N NaOH, extract with CH2Cl2, and acidify with 5% HCl. Collect the white precipitate and recrystallise it from aqueous EtOH and dry it in a vacuum [Akimoto & Yamada Tetrahedron 27 5999 1971]. It is optically stable in dioxane-water (100o/24hours). Racemisation: 72% in 1.2N HCl at 100o/24hours and 68% in 0.67M KOH in BuOH at 118o/23hours [Kyba et al. J Am Chem Soc 95 2693 1973]. It has also been crystallised from *C6H6 (solubility is 1%) using Norite or aqueous EtOH after chromatography through silica gel, eluting with Me2CO/*C6H6. [Kyba et al. J Org Chem 42 4173 1977; see also Brussee & Jansen Tetrahedron Lett 24 3261 1983, Akimoto & Yamada Tetrahedron 27 5999 1971, Beilstein 6 IV 7020.]
