FORMATION OF MIXED ARYL, ALKYL-LITHIUM AGGREGATES IN THE HETEROATOM ASSISTED LITHIATION OF ALPHA,ALPHA'-DIALKYL SUBSTITUTED 1,3-BIS[(DIMETHYLAMINO)METHYL]BENZENE

The heteroatom assisted lithiation of 1,3-bis[1-(dimethylamino)ethyl]b enzene with n-BuLi afforded 2,6-bis[1-(dimethylamino)ethyl]phenyllithi um. An X-ray crystal structure determination revealed a dimeric aggreg ate 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 aggregat e comprising the parent lithiated compound and n-BuLi in a 1:1 molar r atio. The four Li atoms and the four bridging carbon atoms are arrange d in a unique ladder-type C-Li-2-C-2'-Li-2-C framework. (C) 1998 Elsev ier Science S.A.