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)NiBr2] (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(OEt2)] (prominent at low temperature) is observed. Reaction of Ap'H with BuLi in diethyl ether gives rise to [Ap*LiAp*Li(OEt2)]. Deprotonation of Ap*H and Ap'H using KH leads to [Ap*K](n) and [Ap'K](infinity), respectively. [Ap'K](infinity) is a rare example of a crystalline organometallic polymer, as determined by X-ray analysis. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.