Structures and reactions of monomeric and dimeric lithium diazapentadienyl complexes with electrophiles:synthesis of alpha-C,C'-dialkyl-beta-diimines,and dissolution-reversible synthesis of an alpha-alkoxylithium-beta-diimine

摘要

Direct acid-catalysed condensation of substituted anilines with acetylacetone was found to give convenient access to beta-enamineimines [2-Pr~i-C_6H_4NCMeCHCMeNH-2-Pr~i-C_6H_4] and [2-MeO-C_6H_4NCMeCHCMeNH-2-MeO-C_6H_4],whereas TiCl_4-mediated condensation was required to produce [2,6-Pr~i_2-C_6H_3NHC(CF_3)CHC(CF3)N-2,6-Pr~i_2-C_6H_3],which was crystallographically characterized.All are conveniently metallated using Bu~nLi.The structures of monomer [2-Pr~i-C_6H_4NCMeCHCMeN-2-Pr~i-C_6H_4-Li(thf)_2],and dimer [{ 2-MeO-C_6H_4NCMeCHCMeN-2-MeO-C_6H_4-Li)_2] are reported.The structure of the dimeric product of aldol addition of adamantan-2-one to [2-Pr~i-C_6H_4NCMeCHCMeN-2-Pr~i-C_6H_4 centre dot Li.],the lithium scorpionate [{(C_10H_14OLi)CH(CMeN-2-Pr~i-C_6H_4)_2)_2],is also reported.It undergoes retro-aldol dissociation upon dissolution in non-co-ordinating solvents.The efficient synthesis of alpha-C,C dialkylated 'true' beta-diimines by repeat lithiation/alkylation of di- and mono-ortho-isopropylanilino diketiminates is also reported.The differing reactivity of the monomers and dimer with electrophiles,and its relation to the structures of the intermediates,are discussed.