Symmetry or asymmetry in cheletropic additions forming cyclopropanes |
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Authors: | Shinichi Yamabe Noriko Tsuchida Tsutomu Minato Takahisa Machiguchi |
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Affiliation: | (1) Department of Chemstry, Nara University of Education, Takabatake-cho 630-8528, Nara, Japan;(2) Institute for Natural Science, Nara University, 1500 Misasagi-cho, 631-8502, Nara, Japan;(3) Department of Chemistry, Faculty of Science, Saitama University, 338-8570 Saitama, Japan |
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Abstract: | Cheletropic additions forming cyclopropane rings were studied theoretically. Ten addition paths were traced by means of density-functional-theory calculations. Two 1,4-dienes, 1,4-pentadiene, and tricyclo[5.3.1.04,9]undeca-2,5-diene were adopted as substrates. CO, SO2, C2H5PCl2, CCl2 and SiCl2 were employed as cheletropic reagents (Xs). An orbital correlation diagram of the Woodward–Hoffmann (W–H) rule and frontier molecular orbital (FMO) interactions between them were investigated in detail. The FMO interactions, HOMO (1,4-diene)lumo (X) and homo (X)LUMO (diene), work reasonably for the progress of the reactions. Those cause the formation of two C–X bonds and a cyclopropane ring, and alternation of double bonds to single bonds. All the additions are concerted. The easiness of the ring formation depends upon the energy gap between HOMO and lumo and that between homo and LUMO, and the spatial directions of HOMO and LUMO extensions. Symmetry conservation of the W–H rule does not hold necessarily for those addition paths. The symmetry-breaking was discussed in terms of FMO interactions.Acknowledgement This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan and by Nishida Memorial Foundation for Fundamental Chemical Research. |
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Keywords: | Cheletropic additions Frontier molecular orbital Woodward– Hoffmann rule Cyclopropane ring Rehybridization |
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