Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-62448
Gebert, Andreas; Barth, Max; Linden, Anthony; Widmer, Ulrich; Heimgartner, Heinz (2012). Novel Synthesis of 2-Alkylquinolizinium-1-olates and their 1,3-Dipolar Cycloaddition reactions with Acetylenes. Helvetica Chimica Acta, 95(5):737-760.
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Several 2-alkylquinolizinium-1-olates 9, i.e., heterobetaines, were prepared from ketone 11, the latter being readily available either from pyridine-2-carbaldehyde via a Grignard reaction, followed by oxidation with MnO2, or from 2-picolinic acid (= pyridine-2-carboxylic acid) via the corresponding Weinreb amide and subsequent Grignard reaction. Mesoionic heterobetaines such as quinolizinium derivatives have the potential to undergo cycloaddition reactions with double and triple bonds, e.g., 1,3-dipolar cycloadditions or Diels-Alder reactions. We here report on the scope and limitations of cycloaddition reactions of 2-alkylquinolizinium-1-olates 9 with electron-poor acetylene derivatives. As main products of the reaction, 5-oxopyrrolo[2,1,5-de]quinolizines (= '[2.3.3]cyclazin-5-ones') 19 were formed via a regioselective [2+3] cycloaddition, and cyclohexadienone derivatives, formed via a Diels-Alder reaction, were obtained as side products. The structures of 2-benzylquinolizinium-1-olate (9a) and two '[2.3.3]cyclazin-5-ones' 19i and 19l were established by X-ray crystallography.
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|Item Type:||Journal Article, refereed, original work|
|Communities & Collections:||07 Faculty of Science > Department of Chemistry|
|Date:||21 May 2012|
|Deposited On:||22 May 2012 07:28|
|Last Modified:||10 Jul 2014 15:46|
|Publisher:||Verlag Helvetica Chimica Acta|
|Funders:||Swiss National Science Foundation, F. Hoffmann-La Roche AG|
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