Electronic and chelation effects on the unusual C2-methylation of N-(para-substituted)phenylaziridines with lithium organocuprates.
J Comput Chem
; 32(9): 1859-68, 2011 Jul 15.
Article
em En
| MEDLINE
| ID: mdl-21455961
ABSTRACT
Density functional theory calculations with the B3LYP functional were performed for the title ring-opening reaction to understand the intrinsic activating and directing effects of the N-substituents, as well as the electron donating effect of the para-substituted (Y = Cl, H, Me) phenyl group at the more hindered benzylic C2 atom. The N-tosyl group (i.e., N-Tos) or the N-(2-pyridyl)sulfonyl group (i.e., N-Py) was introduced to activate the ring nitrogen atom (N1) and the para-substituted (Y = Cl, H, Me) phenyl group for the activation of the C2 atom. Conformational searches and geometry optimizations were performed for the N-(para-substituted)phenylaziridines (1â¼6). Calculations indicate that the aziridine 6 (i.e., Py/Me) has the most elongated C2-N1 bond intrinsically due to the electronic activating effects, implying the aziridine 6 to be the most potent candidate for the more-hindered C2 opening. Transition states (TSs) were investigated for the prospective ring-opening paths (Iâ¼IV), considering the types of intermolecular push-pull interactions between the N-activated phenylaziridines and the cuprate. The N-Py group provides an unique C2-favored TS along the path IV, which the N-Tos group cannot afford, due to the less charge transfer from the nucleophilic CH 3δ- of the cuprate into the electrophilic C2 atom. Furthermore, the e-donating effect of the para-substituents (Y = Cl, H, Me) enhances the C2 opening for the path IV. This study enables us to understand the unusual ring-opening phenomena in terms of electronic and directing effects and hence may serve as a tool to design substrates for highly regioselective ring openings.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Compostos Organometálicos
/
Aziridinas
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Quelantes
/
Lítio
Idioma:
En
Revista:
J Comput Chem
Assunto da revista:
QUIMICA
Ano de publicação:
2011
Tipo de documento:
Article