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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 26, Number 9
BKCSDE 26(9)
September 20, 2005 

Substituents Effect on Aziridine Chemistry: N-Inversion Energy, Reactivity and Regioselectivity of Nucleophilic Ring-opening
Gyoosoon Park*, Seok-Chan Kim, Han-Young Kang
Aziridine, N-Inversion energy, Nucleophilic ring-opening, Ab initio
The N-inversion energies and nucleophilic ring-opening reactions of N-substituted aziridine compounds are investigated using B3LYP/6-31+G* methods, where substituents (R) on the nitrogen atom has been H (1), Me (2), Ph (3), Bn (4), CHMePh (5), CO2Me (6), COPh (7) and SO2Ph (8). The N-inversion energy with X group are decreased as the following order: R = CHMePh (17.06 kcal/mol) > Me (16.97) > Bn (16.70) > H (16.64) > SO2Ph (12.18) > Ph (8.91) > COPh (5.75) > CO2Me (5.48). For reactivity of the ring opening toward cyanide ion, the aziridine 6 (R=CO2Me) is shown to be the most reactive one. During the ring opening of aziridine 6 by CN , the torsional OCNC angle becomes near to 180o, where the geometry allows for the effective incorporation of electrons of the nitrogen atom to the C=O bond. It would be a possible driving force for nucleophilic ring opening reaction as well as decreasing the N-inversion energy barrier. Regarding to the regioselectivity, the orientation of nucleophile in ring opening reaction appears to be different in the case of 9 and 10. The results are discussed in terms of steric/electronic effect of the C2-substituents.
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