| Popis: |
A series of ring substituted pyridines were selected for the sodium amide initiated heterogeneous Chichibabin amination to obtain 2,6-diaminopyridine derivatives which are important synthons for the preparation of PNP pincer ligands. The substrates were treated with an excess of sodium amide in neat mineral oil as solvent under an argon atmosphere. The reaction required temperatures of up to 215 °C under vigorous stirring with an overall reaction time of 3–5 h. In the case of methyl, tert -butyl, phenyl, pyridinyl, and hydroxyl substituted pyridines the desired products were obtained in good to excellent yields (63–96%). Thus, the Chichibabin reaction provides an inexpensive and economic alternative to methodologies starting from halopyridines or pyridine N -oxides provided that the substituents are inert under the harsh reaction conditions. |
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