1992 Fiscal Year Final Research Report Summary
Nucleophilic Carbonyl Addition of Organometallics: Reaction Pathway, Transition State Structure and Stereoselectivity
| Project/Area Number |
03640451
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
有機化学一般
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| Research Institution | Osaka University |
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Principal Investigator |
YAMATAKA Hiroshi Osaka University, The Institute of Scientific and Industrial Research, Associate Professor, 産業科学研究所, 助教授 (60029907)
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| Co-Investigator(Kenkyū-buntansha) |
ICHIHARA Junko Osaka University, The Institute of Scientific and Industrial Research, Research, 産業科学研究所, 教務職員 (60110772)
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| Project Period (FY) |
1991 – 1992
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| Keywords | Single Electron Transfer / Reaction Route / Reaction Mechanism / Grignard Reaction / Wittig Reaction / Isotope Effect / Substituent Effect / Stereoselectivity |
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| Research Abstract |
Tow reaction routes are possible for nucleophilic additions to carbonyl compounds, polar addition and electron transfer-radical coupling sequence. We have demonstrated that a new radical anion probe experiment utilizing dehalogenation of halo-substituted benzophenone is effective to detect the occurrence of electron transfer during the reaction. Three reactions were carried out: the Grignard reactions, for which the electron transfer mechanism is highly recommended, the addition of allyltributyltin, the reaction considered to proceed through the polar mechanism, and the Wittig reaction for which the reaction pathway is not known at present. In the reaction of omicron-Br or I-benzophenone with MeMgl and PhMgBr considerable amount of dehalogenation products was observed, which clearly indicate the occurrence of electron transfer during the reaction. In contrast, a similar probe reaction with allyltributyltin was found negative. These two sets of reactions confirmed the usefulness of the new probe experiment to detect the occurrence of electron transfer during the reaction in question. Application of this new technique to the Wittig reaction then indicated that the reaction mechanism if highly dependent on the structure of ylide; the reactions of nonstabilized ylides proceed via electron transfer route while those of a semistabilized ylide go through the polar mechanism. These results are fully consistent with the isotope effect as well as the substituent effect data obtained last year in these Wittig reactions. The difference in the reaction route is considered to by responsible to the observed diversity in stereochemistry of the Wittig reaction.
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