Metal-stabilized carbocations derived from monoterpenes: dicobalt hexacarbonyl complexes of alkynyl-verbenols

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• 作者：Angela Moore ; Johannes Ostermann ; Helge Mü ; ller-Bunz ; Yannick Ortin ; Michael J. McGlinchey ; ^{michael.mcglinchey@ucd.ie" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Monoterpenes ; Alkynes ; X-ray crystallography ; 31P NMR spectroscopy ; Cobalt-stabilized cations ; Nuclear overhauser effect
• 刊名：Tetrahedron
• 出版年：2016
• 出版时间：21 July 2016
• 年：2016
• 卷：72
• 期：29
• 页码：4186-4193
• 全文大小：905 K

文摘

Nucleophilic attack by alkynyl anions on the verbenone skeleton occurs on the face opposite to that occupied by the gem-dimethyl group. The resulting alkynols react with dicobalt octacarbonyl to form tetrahedral (μ²-alkyne)Co₂(CO)₆ clusters in which the tricarbonylcobalt moieties are diastereotopic, and treatment with dppm tags each of these vertices with a ³¹P NMR label. Protonation yields a single cobalt-stabilized carbocation, 13a, in which the cobalt is situated on the side bearing the methylene bridge, thus avoiding the gem-dimethyl group, and pulls the capping phenyl substituent proximate to the hydrogen atom at C(3). All new molecules were characterized by NMR spectroscopy and by X-ray crystallography for syn-trimethylsilylethynylverbenol, 6, syn-ethynyl-verbenol, 7, and for the (2-phenylethynyl-4-methylene-6,6-dimethyl-(1S,5S)-bicyclo[3.1.1]hept-2-ene)Co₂(CO)₄(dppm) cluster, 12. The 2-ethynyl-4-methylene-6,6-dimethyl-bicyclo[3.1.1]hept-2-ene ligand, 15, was also prepared and characterized for the first time.