Mechanisms of elimination reactions. XII. Hydrogen isotope effects and the nature of the transition state in eliminations from alicyclic quaternary ammonium salts

1969 ◽  
Vol 91 (16) ◽  
pp. 4473-4478 ◽  
Author(s):  
William H. Saunders ◽  
Thomas A. Ashe
Keyword(s):  
Transition State ◽  
Quaternary Ammonium ◽  
Hydrogen Isotope ◽  
Isotope Effects ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Elimination Reactions

ISOTOPE EFFECT STUDIES ON ELIMINATION REACTIONS: III. NITROGEN ISOTOPE EFFECTS IN THE E2 REACTION OF ETHYLTRIMETHYL-AMMONIUM AND 2-PHENYLETHYLTRIMETHYLAMMONIUM IONS

1963 ◽  
Vol 41 (7) ◽  
pp. 1759-1767 ◽  
Author(s):  
G. Ayrey ◽  
A. N. Bourns ◽  
V. A. Vyas
Keyword(s):  
Isotope Effect ◽  
Quaternary Ammonium ◽  
Isotope Effects ◽  
Transition States ◽  
Nitrogen Isotope ◽  
Quaternary Ammonium Salts ◽  
Ammonium Salts ◽  
Relative Extent ◽  
Deuterium Isotope Effects ◽  
Elimination Reactions

Nitrogen isotope effects have been determined for the E2 reaction of two quaternary ammonium salts with ethoxide ion in ethanol. Ethyltrimethylammonium iodide gave k14/k15 values of 1.017 at 60° and 1.015 at 95°, while 2-phenylethyltrimethylammonium bromide gave 1.012 at 40° and 1.009 at 60°. These results and the β-deuterium isotope effects reported by others have been interpreted in terms of the relative extent of Cα—N+ and Cβ—H bond weakening in the transition states of the two reactions.

scholarly journals Exploring the Scope of Tandem Palladium and Isothiourea Relay Catalysis for the Synthesis of α-Amino Acid Derivatives

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2463
Author(s):  
Jacqueline Bitai ◽  
Alexandra M. Z. Slawin ◽  
David B. Cordes ◽  
Andrew D. Smith
Keyword(s):  
Amino Acid ◽  
Transition State ◽  
Quaternary Ammonium ◽  
Palladium Catalyst ◽  
Quaternary Ammonium Salts ◽  
Sigmatropic Rearrangement ◽  
Ammonium Salts ◽  
Amino Acid Derivatives ◽  
Substitution Pattern

The scope and limitations of a tandem N-allylation/[2,3]-rearrangement protocol are investigated through the incorporation of a variety of functional groups within an allylic phosphate precursor. This method uses readily accessible N,N-dimethylglycine aryl esters and functionalized allylic phosphates, forming quaternary ammonium salts in situ in the presence of a palladium catalyst. Subsequent enantioselective [2,3]-sigmatropic rearrangement, promoted by the chiral isothiourea tetramisole, generates α-amino acid derivatives with two contiguous stereocenters. The incorporation of electron-withdrawing ester and amide groups gave the best results, furnishing the desired products in moderate to good yields (29–70%), with low diastereocontrol (typically 60:40 dr) but high enantioselectivity (up to 90:10 er). These results indicate that substrate–catalyst interactions in the proposed transition state are sensitive to the substitution pattern of the substrates.

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