Highly Selective Ortho‐Directed Dicarboxylation of Cyclopentadiene by Methylcarbonates and CO 2 or COS – First Insight into Co‐ordination Chemistry of New Ambident Ligands
| Autor: | Jörg Sundermeyer, Tobias Vollgraff |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
chemistry.chemical_classification
Cyclopentadiene 010405 organic chemistry Chemistry Organic Chemistry Regioselectivity General Chemistry 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis 0104 chemical sciences Coordination complex chemistry.chemical_compound Delocalized electron Carboxylation Intramolecular force Ionic liquid Lewis acids and bases |
| Zdroj: | Chemistry – A European Journal. 27:8517-8527 |
| ISSN: | 1521-3765 0947-6539 |
| Popis: | This research presents the highly regioselective syntheses of 1,2-dicarboxylated cyclopentadienide salts [Cat]2 [C5 H3 (CO2 )2 H] by reaction of a variety of organic cation methylcarbonate salts [Cat]OCO2 Me (Cat=NR4+ , PR4+ , Im+ ) with cyclopentadiene (CpH) or by simply reacting organic cation cyclopentadienides Cat[Cp] (Cat=NR4+ , PR4+ , Im+ ) with CO2 . One characteristic feature of these dianionic ligands is the acidic proton delocalized in an intramolecular hydrogen bridge (IHB) between the two carboxyl groups, as studied by 1 H NMR spectroscopy and XRD analyses. The reaction cannot be stopped after the first carboxylation. Therefore, we propose a Kolbe-Schmitt phenol-carboxylation related mechanism where the acidic proton of the monocarboxylic acid intermediate plays an ortho-directing and CO2 activating role for the second kinetically accelerated CO2 addition step exclusively in ortho position. The same and related thiocarboxylates [Cat]2 [C5 H3 (COS)2 H] are obtained by reaction of COS with Cat[Cp] (Cat=NR4+ , PR4+ , Im+ ). A preliminary study on [Cat]2 [C5 H3 (CO2 )2 H] reveals, that its soft and hard coordination sites can selectively be addressed by soft Lewis acids (Mo0 , Ru2+ ) and hard Lewis acids (Al3+ , La3+ ). |
| Databáze: | OpenAIRE |
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