Formation of mixed aryl, alkyl-lithium aggregates in the heteroatom assisted lithiation of α,α′-dialkyl substituted 1,3-bis[(dimethylamino)methyl]benzene

The heteroatom assisted lithiation of 1,3-bis[1-(dimethylamino)ethyl]benzene with n-BuLi afforded 2,6-bis[1-(dimethylamino)ethyl]phenyllithium. An X-ray crystal structure determination revealed a dimeric aggregate in which the four benzylic chiral centers are identical, pointing to stereoselective crystallization. In contrast, reaction of 1,3-bis[1-(dimethylamino)propyl]benzene with n-BuLi afforded a dimeric aggregate comprising the parent lithiated compound and n-BuLi in a 1:1 molar ratio. The four Li atoms and the four bridging carbon atoms are arranged in a unique ladder-type C-Li-2-C-2'-Li-2-C framework. (C) 1998 Elsevier Science S.A.