Lithium and Potassium Amides of Sterically Demanding Aminopyridines

The reaction of Grignard compounds of 1‐bromo‐2,4,6‐diisopropylbenzene ( 1 ) or 1‐bromo‐2,6‐dimethylbenzene ( 2 ), formed in situ, with 2,6‐dibromopyridine in the presence of a catalytic amount of [(dme)NiBr 2 ] (dme = 1,2‐dimethoxyethane) and tricyclohexylphosphane (1:2 ratio) leads to the corresponding monoarylated bromopyridines. These bromopyridines undergo Pd‐catalysed aryl amination (Buchwald−Hartwig amination) with 2,6‐diisopropylaniline giving rise to (2,6‐diisopropylphenyl)[6‐(2,4,6‐triisopropylphenyl)pyridin‐2‐yl]amine (Ap*H) and (2,6‐diisopropylphenyl)[6‐(2,6‐dimethylphenyl)pyridin‐2‐yl]amine (Ap′H) (Ap = aminopyridinate). Deprotonation of Ap*H in diethyl ether using BuLi results (after workup in hexane) in a colourless crystalline material. X‐ray structural analysis reveals it to be a monomeric three‐coordinate lithium aminopyridinate. In toluene solution, an equilibrium between [(Ap*Li) 2 ] (in excess at room temperature) and [Ap*Li(OEt 2 )] (prominent at low temperature) is observed. Reaction of Ap′H with BuLi in diethyl ether gives rise to [Ap*LiAp*Li(OEt 2 )]. Deprotonation of Ap*H and Ap′H using KH leads to [Ap*K] n and [Ap′K] ∞ , respectively. [Ap′K] ∞ is a rare example of a crystalline organometallic polymer, as determined by X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)