title: Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts.
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.
authors.affiliation: 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.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Kiamehr
authors.forename: Firouz Matloubi
authors.initials: FM
authors.lastname: Moghaddam
authors.forename: Satenik
authors.initials: S
authors.lastname: Mkrtchyan
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Semeniuchenko
authors.forename: Linda
authors.initials: L
authors.lastname: Supe
authors.forename: Alexander
authors.initials: A
authors.lastname: Villinger
authors.forename: Peter
authors.initials: P
authors.lastname: Langer
authors.forename: Viktor O
authors.initials: VO
authors.lastname: Iaroshenko
keywords: cyclization; density functional calculations; heterocycles; nucleophilic addition; pyridinium salt