Convenient Syntheses of Chiral 3-Substituted 2-Ethynylaziridines.

Two convenient methods for the synthesis of chiral 2-ethynylaziridines from natural α-amino acids are described. Sodium hydride-promoted aziridination of mesylates of 4-arylsulfonylamino-2-bromoalk-2-en-1-ols yields trans-2-(1-bromovinyl)aziridines in a highly stereoselective manner, and subsequent 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-ethynylaziridines with high optical purities (91–98% ee) from chiral amino alcohols bearing an ethynyl group under Mitsunobu conditions is also presented.