Y. Kato, Y. Kitamoto, Naoya Morohashi
Apr 29, 2009
Citations
0
Influential Citations
11
Citations
Journal
Tetrahedron Letters
Abstract
Abstract In the recrystallization of a diastereomeric mixture of amides ( RS a , S )- 1 formed from racemic 1,1′-binaphthalene-2,2′-dicarboxylic acid and ( S )-1-phenylethylamine, either of the diastereomers crystallizes out as a diastereomerically pure form, depending on the solvent employed; sterically undemanding solvents, acetone, dichloromethane, and acetonitrile, afford crystals formulated as ( S a , S )- 1 ·solvent with an exception of ethanol, which affords ( R a , S )- 1 ·EtOH, while sterically bulkier solvents afford ( R a , S )- 1 including no solvent. The stereoselectivity can be rationalized by the crystal structures. A dielectrically controlled resolution (DCR) can also be carried out by using mixed solvents, which contain, for example, 25 vol % of acetone and varying ratios of hexane and 1-propanol in total 75 vol %; ( S a , S )- 1 ·acetone is deposited as crystals from the solvents with a dielectric constant ( e ) range 8.9 ⩽ e ⩽ 10.2, while ( R a , S )- 1 is deposited from the solvents with 14.8 ⩽ e ⩽ 20.3.