Preparation of diamines by lithiation-substitution of imidazolidines and pyrimidines

The synthesis of chiral 1,2-diamines and 1,3-diamines was achieved from the unsubstituted diamines by way of N-tert-butoxycarbonyl (Boc) substituted imidazolidines (tetrahydroimidazoles) and pyrimidines (hexahydro-1,3-diazines), which were treated with sec-butyllithium to effect deprotonation alpha- to the N-Boc group, followed by addition of an electrophile to give substituted products that could be hydrolysed under acidic conditions to give the substituted 1,2- or 1,3-diamines. Use of the chiral ligand (-)-sparteine promoted asymmetric deprotonation of the imidazolidine substrates to give, after hydrolysis, enantiomerically enriched 1,2-diamines.