Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides.
Beilstein J Org Chem
; 11: 1441-6, 2015.
Article
em En
| MEDLINE
| ID: mdl-26425200
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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
Beilstein J Org Chem
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Alemanha