Abstract
Palladium catalysed Sonogashira reactions between 2,4,6-tribromo-3,5-difluoropyridine and a variety of phenylacetylene derivatives gave a series of 4-bromo-2,6-bis(2-phenylethynyl)-3,5- difluoropyridine derivatives arising from displacement of bromine atoms attached to positions ortho to ring nitrogen.
Highlights
It is well established that the incorporation of fluorine atoms into heterocyclic molecules can have a significant effect upon the chemical and biological properties of these systems.[2,3] This has been used to great effect in the development of various commercially important life-science products, such as 5-fluorouracil, 5-fluoroprimaquine and Ciprofloxacin, that owe their useful biological activity to the presence of a fluorine substituent located on the heterocyclic ring.[3]
In the life science/drug discovery arena, strategies for the synthesis of novel families of polysubstituted heterocyclic systems of readily variable molecular architecture are of increasing importance, due to the surprisingly high proportion of commercially important pharmaceutical and plant protection products that are based upon a small heterocyclic ring core scaffold.[5,6,7,8]
We are developing the chemistry of perhalogenated heteroaromatic systems and we have demonstrated that perfluorinated heterocyclic derivatives, such as pentafluoropyridine, are very useful polyfunctional heterocyclic scaffolds[4,9] because, in principle, all of the fluorine atoms are activated towards nucleophilic attack and may be replaced by appropriate nucleophilic species.[10]
Summary
It is well established that the incorporation of fluorine atoms into heterocyclic molecules can have a significant effect upon the chemical and biological properties of these systems.[2,3] This has been used to great effect in the development of various commercially important life-science products, such as 5-fluorouracil, 5-fluoroprimaquine and Ciprofloxacin, that owe their useful biological activity to the presence of a fluorine substituent located on the heterocyclic ring.[3]. Palladium catalysed Sonogashira reactions involving 2,4,6-tribromo-3,5difluoropyridine give products arising from the displacement of bromine atioms located at the 2and 6-positions, ortho to ring nitrogen, further demonstrating the use of perhalogenated scaffolds for synthetic applications.
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