Co(II)-Mediated and microwave assisted coupling between 2,6-diaminopyridine and nitriles. A new synthetic route to N-(6-aminopyridin-2-yl)carboximidamides |
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| Authors: | N A Bokach V Yu Kukushkin M Haukka T B Mikhailova A A Sidorov I L Eremenko |
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| Institution: | (1) Department of Chemistry, St. Petersburg State University, 26 Universitetsky prosp., 198504 Stary Petergof, Russian Federation;(2) Department of Chemistry, University of Joensuu, P.O. Box 111, Joensuu, FIN-8010, Finland;(3) N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 31 Leninsky prosp., 119991 Moscow, Russian Federation |
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| Abstract: | The Chinese-lantern-type Co2(O2CBut)4{2,6-(NH2)2C5H3
N}2 complex reacts with RCN (R = Me or Prn) under microwave irradiation (MWI) to give the mononuclear amidine complexes Co(O2CBut)2{H2N(C5H3
N)NHC(R)=NH} (R = Me (4a) or Prn (4c)). Under microwave irradiation, the addition of 2,6-diaminopyridine to acetonitrile in the presence of the pivalate complexes
Co2(μ2-OH2)(O2CBut)4(HO2CBut)4 (1) or Co(OH)n(O2CBut)2−n
]x (2) afforded complex 4a in higher yield compared to the corresponding reaction performed earlier without MWI. The use of MWI makes it possible to
perform analogous reactions with nitriles RCN (R = Et, Prn, or Ph) giving rise to complexes 4b—d, respectively. Compounds 4a—d were characterized by elemental analysis and IR spectroscopy. The structure of complex 4c was established by X-ray diffraction. Amidines H2N(C5H3N)NHC(R)=NH, which formed in the coordination sphere of cobalt(II), were isolated in the free state from methanolic solutions of complexes 4a—d under the action of Na2S and were characterized by electrospray mass spectrometry and 1H and 13C{1H} NMR spectroscopy. The reactions of 2-aminopyridine with both complexes 1 and 2 in acetonitrile under microwave irradiation produced the Co(O2CBut)2(H2NC5H4N)2 complex.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–42, January, 2006. |
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| Keywords: | microwave synthesis coordinated nitriles ligand reactivity cobalt complexes aminopyridines amidines |
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