Synthesis of chiral 1,2-diamines by asymmetric lithiation-substitution

[GRAPHICS] The imidazolidine (tetrahydrolmidazole) 2, prepared in one step from N-iso- propylethylenediamine, was subjected to asymmetric lithiation and substitut ion using sec-butyllithium, (-)-sparteine and a range of electrophiles. Sub stituted imidazolidines were formed with high optical purity and could be h ydrolyzed under acidic conditions to chiral, substituted ethylenediamines. Kinetic data indicate that the conformation of the carbonyl group is crucia l to the extent of deprotonation, and this has implications for the lithiat ion of unsymmetrical carbamates and carboxylic amides.