Theoretical studies on hetero Diels-Alder reactions of sulfur diimides

Title
Theoretical studies on hetero Diels-Alder reactions of sulfur diimides
Authors
Kim, C.K.; Lee, B.S.; Lee, H.W.
Keywords
NATURAL RESONANCE THEORY, REARRANGEMENT
Issue Date
2002-10
Publisher
ROYAL SOC CHEMISTRY
Abstract
The gas-phase hetero Diels-Alder cycloaddition reactions of the sulfur diimides HN=S+N-X, where X = CH3, H, Cl, CN and NO2, with 1,3-butadiene were investigated theoretically at the B3LYP/6-31G* level. The most stable isomers of sulfur diimides have Z,Z-forms, which are more stable than the least stable E,E-forms by 6-11 kcal mol(-1). The reactions proceed mostly with HN=S+N-X (2) rather than HN-S+=NX (2') even with an electron-donor X ( = CH3). The activation free energy (DeltaG(double dagger)) is lower, the stronger the electron-accepting ability of X. The lowest cycloaddition barriers are obtained in the exo-additions of the E,E-isomers, which are lower by ca 10-13 kcal mol(-1) than the highest barrier exo-processes of the Z,Z-isomers. The repulsive interactions between the diene pi electrons and the endo lone pair on N (n(N)), and the steric hindrance of a bulky group, are the two major factors that are responsible for the cycloaddition barrier heights.
URI
http://dspace.inha.ac.kr/handle/10505/20301
ISSN
1144-0546
Appears in Collections:
College of Natural Science(자연과학대학) > Chemistry (화학) > Journal Papers, Reports(화학 논문, 보고서)
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