The diimine prepared by condensation of glyoxal trimer dihydrate with (S)-1-phenylethylamine underwent double addition of allylic zinc compounds (2-butenyl-, 2,4-pentadienyl-, 2-methyl-2-propenylzinc bromide) in THF generally at -78 °C, with allylic inversion. The newly formed stereocentres adjacent to the nitrogen atoms had prevalently the R configuration. Removal of the auxiliary from the secondary 1,2-diamines with concomitant hydrogenation of the C=C double bonds afforded the primary 1,2-diamines. The reaction with 3-methyl-2-butenylzinc bromide gave almost exclusively the α-amino imine from which the α-aminoaldehyde was obtained by hydrolysis. On the other hand, 3-methyl-2-butenylmagnesium chloride reacted at 0-20 °C to give the diamine with linear-chain substituents, owing to the reversibility of the organometallic addition.
One-pot Preparation of 1,2-Aminoalcohols or Pyrroles by CeCl3 · 7 H2O-mediated Barbier Reactions of N,N′-Bis[(S)-1-phenylethyl]ethanediimine
作者:Gianluca Martelli、Stefano Morri、Diego Savoia
DOI:10.1055/s-2002-19343
日期:——
1,2-Aminoalcohols or pyrroles were obtained from N,N’-bis[(S)-1-phenylethyl]ethanediimine by a one-pot procedure involving two Barbier additions of allylic and/or propargyl zinc reagents alternated with the hydrolysis of the unreacted imine function, followed by a cyclisation/dehydration sequence when a 1-amino-5-pentyne moiety was involved, all these steps being promoted by CeCl3·7 H2O.