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Mixed Aggregates of an Alkyl Lithium Reagent and a Chiral Lithium Amide Derived From N-ethyl-O-triisopropylsilyl Valinol

Mixed Aggregates of an Alkyl Lithium Reagent and a Chiral Lithium Amide Derived From N-ethyl-O-triisopropylsilyl Valinol

Chicheung Su, Russell Hopson, Paul G Williard

J Am Chem Soc. 2013 Sep 25;135(38):14367-79.

PMID: 23980610

Abstract:

The crystal structure of a mixed aggregate containing lithiated (S)-N-ethyl-3-methyl-1-(triisopropylsilyloxy)butan-2-amine derived from (S)-valinol and cyclopentyllithium is determined by X-ray diffraction. The mixed aggregate adopts a ladder structure in the solid state. The ladder-type mixed aggregate is also the major species in a toluene-d8 solution containing an approximately 1:1 molar ratio of the lithiated chiral amide to cyclopentyllithium. 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 allowed us to characterize the complex in solution. Solution state structures of the mixed aggregates of n-butyl, sec-butyllithium, isopropyllithium with lithiated (S)-N-ethyl-3-methyl-1-(triisopropylsilyloxy)butan-2-amine are also reported. Identical dimeric, ladder-type, mixed aggregates are the major species at a stoichiometric ratio of 1:1 lithium chiral amide to alkyllithium in toluene-d8 solution for all of the different alkyllithium reagents.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1888751	Isopropyllithium solution		1888-75-1	Price

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