In Pursuit of cis,cis,cis-Cyclonona-2,5,8-triene-1,4,7-trione - An Adventure in Medium-Sized Ring Chemistry

• Published in: European Journal of Organic Chemistry Vol. 2007; no. 29; pp. 4867 - 4880
• Main Authors: Pleschke, Axel, Geier, Jens, Keller, Manfred, Wörth, Jürgen, Knothe, Lothar, Prinzbach, Horst
• Format: Book Review Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.10.2007; WILEY‐VCH Verlag; Wiley
• Subjects: bridged; Calculations; Chemistry; Chemistry, Organic; Cyclononanes; Cyclononanes, highly functionalized, bridged; highly functionalized; Physical Sciences; Science & Technology; Tris σ/π-Homobenzenes; PHOTOELECTRON-SPECTRA; BENZENE; MOLECULAR-STRUCTURE; CRYSTAL; DENSITY-FUNCTIONAL THERMOCHEMISTRY; TRIS-SIGMA-HOMOBENZENES; AMINOGLYCOSIDE ANTIBIOTICS; MILD; highly functionalized; PHOTOCHEMICAL-TRANSFORMATIONS; tris sigma/pi-Homobenzenes; TRIDENTATE LIGAND; bridged; calculations; cyclononanes
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.200700397

Attempts to synthesize the long soughtafter tris‐π‐homobenzene cis,cis,cis‐2,5,8‐cyclononatriene‐1,4,7‐trione, via the newly prepared cyclononane‐1,4,7‐trione (C9H6O3), through base‐catalysed threefold HBr elimination from an efficiently prepared and stereochemically uniform tribromo derivative, failed due to typical medium‐ring complications, transannular reactions and an exceptional ease of polymerization. In the cations generated in the vapour phase through electron‐impact ionization (MS), the threefold elimination of (H)Br, competing with the elimination of CO, led to C9H7O3+ ions, whereas the impressively neat anionic three‐step fragmentation pathway resulted in C9H6O3– ion(s). Whilst the compositions of these bromine‐free ions, which were in part computationally approached {B3LYP/6‐31+G(d,p)}, and their assignments appeared compatible with the protonated and anionic target molecules, their true natures remain open. X‐ray structural analyses for several (bridged) nine‐membered ring compounds are provided. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)