Bicyclic strained allenes : incorporation of an allene unit into alpha-pinene and benzonorbornadiene

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2004

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Azizoğlu, Akın

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The first part of study describes an investigation aimed at the incorporation of an allene unit into a natural compound, being alpha-pinene, by using Doering-Moore-Skatteboel method. DFT computations show that both allene product and insertion product can be isolated if the reaction of methyllithium with 3,3-dibromo-2,7,7-trimethyl-tricyclo[4.1.1.02,4]octane is carried out at either low or high temperatures. One insertion product resulting from the intramolecular C-H insertion at the bridge and three allene dimers were isolated when this reaction was carried out at room temperature. In the second part of study, exo- and endo-cyclopropylidene incorporated into benzonorbornadiene were investigated by using theoretical and experimental methods. Theoretical calculations show that the endo-carbene would be stable and undergo some kind of insertion and addition reactions. On the contrary, the exo-carbene is not stable and isomerizes to the corresponding allene structure during the optimization process. For this purpose, the reaction of dibromocarbene and dichlorocarbene with 7-methoxybenzonorbornadiene was achieved to afford gem-dibromocyclopropane and gem-dichlorocyclopropane adducts, respectively. However, they suffer stereoelectronically-controlled ring opening under the reaction conditions to give the ring-expanded allylic dihalides, respectively. On the other hand, gem-bromofluorocyclopropane, obtained by the treatment of 7-methoxybenzonorbornadiene with bromofluorocarbene, provided one of the four possible [2+4] allene adducts upon treatment with MeLi in furan. The exact structure of the adduct has been elucidated on the basis of NMR spectral data. This result confirms the formation of the bicyclic allene as an reactive intermediate. No products were isolated derived from the endo-carbene.

Subject Keywords

Chemistry, Organic

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http://etd.lib.metu.edu.tr/upload/3/12605053/index.pdf
https://hdl.handle.net/11511/14233

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. Azizoğlu, “Bicyclic strained allenes : incorporation of an allene unit into alpha-pinene and benzonorbornadiene,” Ph.D. - Doctoral Program, Middle East Technical University, 2004.