Asymmetric Synthesis of Thioamido Selenides. A Simple Synthetic Route to Enantiopure Thiazolines

The mixtures of two enantiomerically pure diastereoisomeric amido selenides, obtained from the reactions of alkenes with camphorselenyl sulfate in a mixture of, ater and a nitrile, were treated with Lawesson's reagent to afford a mixture of the two corresponding thioamido derivatives. The two diastereoisomeric thioamido selenides could be easily separated by flash chromatography. The thioamido selenides, after activation with PhSeCl, underwent deselenylation by a stereospecific intramolecular substitution. Thus both enantiomeric thiazolines could be obtained in enantiomerically pure form.