Convenient syntheses of chiral 3-substituted 2-ethynylaziridines

Two convenient methods for the synthesis of chiral 2-ethynylaziridines from natural alpha-amino acids are described. Sodium hydride-promoted aziridina tion of mesylates of 4-arylsulfonylamino-2-bromoalk-2-en-1-ols yields trans - 2-(1-bromovinyl)aziridines in a highly stereoselective manner, and subseq uent dehydrobromination of the aziridines by potassium tert-butoxide gives separable stereoisomeric mixtures of trans- and cis-2-ethynylaziridines in enantiomerically pure forms (> 98% ee). Simple synthesis of 2-ethynylazirid ines with high optical purities (91-98% ee) from chiral amino alcohols bear ing an ethynyl group under Mitsunobu conditions is also presented.