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Beilstein J Org Chem. 2013 Jun 10;9:1119-26. doi: 10.3762/bjoc.9.124. Print 2013.

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts.

Author information

1
Institut für Chemie der Universität Rostock, Albert-Einstein-Straße 3a, D-18059 Rostock, Germany, ; Laboratory of Organic Synthesis and Natural Products, Department of Chemistry, Sharif University of Technology, P. O. Box 11155-9516 Tehran, Iran ; Department of Chemistry, Faculty of Science, University of Qom, Qom, Iran.

Abstract

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0(2,7)]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product.

KEYWORDS:

cyclization; density functional calculations; heterocycles; nucleophilic addition; pyridinium salt

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