Isoxazole Strategy for the Synthesis of 2,2'-Bipyridine Ligands: Symmetrical and Unsymmetrical 6,6'-Binicotinates, 2,2'-Bipyridine-5-carboxylates, and Their Metal Complexes

The Journal of Organic Chemistry
Ekaterina E GalenkoAlexander F Khlebnikov

Abstract

An effective strategy was developed for the synthesis of new 2,2'-bipyridine ligands, symmetrical and unsymmetrical 6,6'-binicotinates, and 2,2'-bipyridine-5-carboxylates, from 4-propargylisoxazoles. The synthesis of symmetrical 2,2'-disubstituted 6,6'-binicotinates was achieved using the Eglinton reaction of 5-methoxy-4-(prop-2-yn-1-yl)isoxazoles with Cu(OAc)2, followed by Fe(NTf2)2/Au(NTf2) tBuXPhos-catalyzed isomerization of the so-formed mixture of isoxazole/azirine-substituted biacetylenic intermediates. Unsymmetrical 2,2'-disubstituted 6,6'-binicotinates were prepared via a copper-free Sonogashira coupling of 5-methoxy-4-(prop-2-yn-1-yl)isoxazoles with 6-bromonicotinates to give methyl 6-(3-(5-methoxyisoxazol-4-yl)prop-1-ynyl)pyridine-3-carboxylates, followed by a transformation of the propargylisoxazole moiety of the adduct into the pyridine fragment under Fe(II)/Au(I) relay catalysis conditions. 6-(Pyrid-2-yl)nicotinates were synthesized by a Stille-type coupling of 2-(tributylstannyl)pyridine with 6-bromonicotinates. Several cyclopalladated complexes of a new series of 6,6'-binicotinates and 2,2'-bipyridine-5-carboxylates and the homoleptic Cu(I) complex were synthesized in high yields.

References

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Dec 23, 2016·Journal of the American Chemical Society·Kyung Min ChoiOmar M Yaghi
Apr 30, 2017·The Journal of Organic Chemistry·Alexey V GalenkoAlexander F Khlebnikov
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Aug 22, 2018·Accounts of Chemical Research·Tasha DrakeWenbin Lin

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Citations

Apr 4, 2021·Molecules : a Journal of Synthetic Chemistry and Natural Product Chemistry·Timur O ZanakhovAlexander A Khlebnikov
Apr 14, 2021·The Journal of Organic Chemistry·Ekaterina E GalenkoAlexander F Khlebnikov
Aug 7, 2019·The Journal of Organic Chemistry·Ekaterina E GalenkoAlexander F Khlebnikov
Apr 9, 2020·The Journal of Organic Chemistry·Ekaterina E GalenkoAlexander F Khlebnikov

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