Files in this item
|(no description provided)|
|Title:||Chemical and Mechanistic Studies of Alpha' Lithio Amides|
|Doctoral Committee Chair(s):||Beak, Peter|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||The lithiation and electrophilic substitution of the allyl amides, N-allyl-N-methyl-2-ethyl-methylbutanamide (76), 1,2,5,6-tetrahydropyridinyl-2-ethyl-2-methylbutanamide (77), 3-methylene-2-ethyl-2-methylbutanamide (78) and 5-tert-butyl-1,2,5,6-tetrahydropyridinyl-2-ethyl-2-methylbutanamide (79) is reported. The $\alpha\sp\prime$ lithio amides from 76, 77, and 79 are found to react with a variety of electrophiles in moderate yields to give both $\alpha$ and $\gamma$ substituted products, and the $\alpha\sp\prime$ lithio amide 78 which has the geometry of the anion in E configuration, gives only poor yields. High diastereoselectivity in the reaction products from the $\alpha\sp\prime$ lithio amide from 79 is found.
The structure of the $\alpha\sp\prime$ lithio allyl amide intermediates in the reaction of 76, 77 and 79 were investigated by $\sp1$H and $\sp $C NMR spectroscopy and found to be delocalized species with only one geometry about the amide C-N bond. The anion, 93, generated from amide 6 was found to exist in the Z conformation to the limits of $\sp1$H and $\sp $C NMR detection. The anion, 161, generated from amide 79 gave spectra consistent with the presence of a single conformationally rigid diastereomeric anion. An investigation of the $\alpha\sp\prime$ lithio anion of 4-tert-butylpiperidinyl-2,2-diethylbutanamide (80), 165, showed the piperidinyl ring to be conformationally rigid, and the $\alpha\sp\prime$ carbanion to be sp$\sp3$ hybridized.
An intermolecular hydrogen isotope study of the alpha lithiation of 77 established that the slow step in the metalation of the amide is proton removal. Examination of diastereospecifically labeled deutero amides 138e and 138a as well as 80-d showed that the $\alpha\sp\prime$ protons in the plane of the amide are more acidic than those out of the amide plane consistent with the experimental and calculated stereoelectronics associated with amide stabilization of $\alpha\sp\prime$ lithio amide anions.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
|Date Available in IDEALS:||2014-12-15|