Chiral Lithium Diamides Derived from Linked N‑Isopropyl Valinol or Alaninol

Four different chiral diamino diethers synthesized from N-isopropyl valinol or N-isopropyl alaninol were lithiated with n-butyllithium in tetrahydrofuran or diethyl ether. Crystal structures of the dilithiated diamino diethers were determined by X-ray diffraction. Three dilithiated diamino diethers including (2S,2′S)-1,1′-(butane-1,4-diylbis­(oxy))­bis­(N-isopropylpropan-2-amine) 7, (2S,2′S)-1,1′-(pentane-1,5-diylbis­(oxy))­bis­(N-isopropylpropan-2-amine) 8, and (2S,2′S)-1,1′-(heptane-1,7-diylbis­(oxy))­bis­(N-isopropyl-3-methylbutan-2-amine) 9 are dimers, whereas dilithiated (2S,2′S)-1,1′-(pentane-1,5-diylbis­(oxy))­bis­(N-isopropyl-3-methylbutan-2-amine) 10 is a monomer. The lithium atoms in all crystal structures adopt a nonequivalent coordination protocol and exist in two different environments in which one of the lithium atoms is tetra-coordinated while the other one is tri-coordinated. The solution structures of the dilithiated diamino diethers are also characterized by a variety of NMR experiments including diffusion-ordered NMR spectroscopy (DOSY) with diffusion coefficient-formula (D-FW) weight correlation analyses and other one- and two-dimensional NMR techniques.