controlled oxazolidineformation was observed with aromatic aldehydes substituted by electron-withdrawing groups. The stereoselectivity is solvent dependent: non-stereoselective ring closure occurred in chloroform while a high diastereodifferentiation was observed in methanol. The first oxazolidine showing an unambiguous 2R configuration was synthesized from p-bromobenzaldehyde and (-)-ephedrine in alcohol
Role of solvent on the diastereoselectivity of oxazolidine formation from (–)-ephedrine
作者:Claude Agami、Toufic Rizk
DOI:10.1039/c39830001485
日期:——
Under kinetic control, the stereochemical course of the condensation between (–)-ephedrine and p-cyano-or p-nitro-benzaldehyde is solvent dependent; no noticeable stereoselectivity was observed in chloroform whereas diastereo-differentiation occurred in methanol.
By reaction of aromatic aldehydes with (-)-ephedrine aromatic 1,3-oxazolidines can be obtained. The reaction was carried out either at conventional conditions or by microwave heating. The different diastereomeric ratios were determined by Means of H-1 NMR spectroscopy.