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|Title:||Studies of alpha-lithioamine synthetic equivalents: I. Elaboration of primary amines. II. Detection of an intermediate in the lithiation of a benzylic urea|
|Author(s):||Resek, James Edward|
|Doctoral Committee Chair(s):||Beak, Peter|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Reagents for the $\alpha$-substitution of N-Boc-benzylamine and N-Boc-allylamine have been developed via dilithiation and electrophilic substitution. Discussion of the specific conditions employed to accomplish these transformations is presented, as well as mechanistic speculation. Dilithiation and substitution of O-benzyl-N-methyl carbamate has been achieved, and use of sec-BuLi/(-)sparteine as the base provided the corresponding products with up to 57% enantiomeric excess. Lithiation of N-tert-butyl-N-benzyl carbamates resulted in rearrangement to phenylglycine derivatives. These related investigations are also discussed.
The intramolecular and intermolecular primary hydrogen-deuterium kinetic isotope effects for the benzylic deprotonation of N-benzyl-N,N$\sp\prime$-dimethyl urea with sec-BuLi/TMEDA have been measured to be 13 $\pm$ 3 and 2.0 $\pm$ 0.7, respectively, at $-$78$\sp\circ$C. These substantially different values exclude a one-step deprotonation mechanism and are taken as evidence for the formation of a pre-lithiation complex between the substrate and sec-BuLi which has a rate of decomplexation that is competitive with proton transfer. Detailed kinetic analysis and discussion of the implications of these results are presented.
|Rights Information:||Copyright 1994 Resek, James Edward|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI9416430|