Enhanced Aromaticity of the Transition Structures for the Diels−Alder Reactions of Quinodimethanes: Evidence from ab Initio and DFT Computations

2000 ◽  
Vol 65 (23) ◽  
pp. 7971-7976 ◽  
Author(s):  
Mariappan Manoharan ◽  
Frank De Proft ◽  
Paul Geerlings
Keyword(s):  
Ab Initio ◽  
Diels Alder ◽  
Dft Computations ◽  
Transition Structures ◽  
Ab Initio And Dft

Ab Initio and DFT Study of the Influence of the Allene Group on the Diels–Alder Reaction

2004 ◽  
Vol 15 (4) ◽  
pp. 323-326 ◽  
Author(s):  
M. Luisa Ferreiro ◽  
Jesús Rodríguez-Otero ◽  
Enrique M. Cabaleiro-Lago
Keyword(s):  
Ab Initio ◽  
Alder Reaction ◽  
Diels Alder ◽  
Dft Study ◽  
Diels Alder Reaction ◽  
Ab Initio And Dft

scholarly journals Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides

2015 ◽  
Vol 11 ◽  
pp. 1441-1446 ◽  
Author(s):  
Armando Navarro-Vázquez
Keyword(s):  
Ab Initio ◽  
Equilibrium Position ◽  
Structural Changes ◽  
Energy Gap ◽  
Equilibrium Mixture ◽  
Experimental Results ◽  
Exchange Equilibrium ◽  
Small Energy ◽  
Dft Computations ◽  
Ab Initio And Dft

The base-catalyzed isomerization of N-propargylamides or carbamates may furnish N-allenyl compounds (allenamides/allencarbamates) or further evolve to N-alkynyl compounds (ynamides or yncarbamates). The particular fate of this reaction varies from experiment to experiment and there is no clear rule for predicting the reaction outcome for a particular structure. With the support of ab initio and DFT computations, this work shows that observed results can be explained by assuming an exchange equilibrium between energetically close N-propargyl, allenyl and N-alkynyl forms and that the reaction outcome correlates to a particular equilibrium mixture. Due to the very small energy gap between the N-allenyl and N-alkynyl forms, small structural changes may easily alter the equilibrium position, explaining the variety of observed experimental results. Based on CBS-QB3 computations, the ωB97 functional provided reasonably accurate isomerization energies and could successfully predict the experimentally observed behavior for several examples from the literature.

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