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)-l,l'-(heptane -l,7 -diylbis (oxy ))b is (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 o f 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. [ABSTRACT FROM AUTHOR]