A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying
2,3-cis- and 2,3-trans-N-Arylsulfonyl-2-ethynylaziridines with high enantiomeric purity have been synthesized. N-Protected amino aldehydes synthesized from natural alpha-amino acids were successively treated with Ph3P=C(Br)CO2Me, DIBAL, MsCl-Et3N, NaH in DMSO, and tert-BuOK in THF to yield 2-ethynylaziridines in good to high yields. (C) 1998 Elsevier Science Ltd. All rights reserved.