Directed Functionalization of Aromatic C-H Bonds in Electrocatalytic Phosphorylation and Fluoroalkylation Reactions with the Participant of Transition Metal Complexes
Authors: Strekalova Sofia , Khrizanforov Mikhail , Gryaznova Tatyana , Budnikova Yulia 
Published: February 2020

The formation of carbon-phosphorus and carbon-fluoroalkyl bonds catalyzed by transition metal complexes is considered as an important methodology for producing of various useful compounds. Many of these compounds exhibit a high biological activity and are widely used in organic synthesis, medical chemistry, materials or as versatile ligands in many catalytic reactions.1-2

However, it should be noted that in majority of papers as aromatic substrates are used organic halides, while examples of substituted C-H bonds, where the leaving group is hydrogen, are much smaller. Major reviews of the latest achievements in the field of  formation of metal-catalyzed С-P bonds published in recent years almost do not consider examples of phosphorylation of aromatic C-H bonds.3 Known fluoroalkylation  reactions also have the drawbacks: the high cost of the reagents, the frequent requirement for forcing reaction conditions, a modest substrate scope.4

That is why the purpose of our work is to develop a more economically and environmentally beneficial method of obtaining phosphorus, fluoroalkyl compounds by electrochemical activation of aromatic C-H bonds under electrocatalysis involving transition metal complexes.

The interest in electrochemical fluoroalkylation and phosphorylation reactions is driven by a number of factors: mild conditions (moderate temperature, ambient pressure), the possibility of closed-loop implementation with a small amount of the catalyst reactant that is repeatedly recycled, and the high environmental safety of the synthesis, especially in comparison with the traditional organic chemistry techniques. Electrosynthesis is also useful in transition metal catalysis for generating the active form of the catalyst without the need to add external oxidizing or reducing agents.5-7

Thus in a series of experiments products of phosphorylation and fluoroalkylation of aromatic substrates (benzene, coumarin, caffeine, pyridine, ferrocene)  were obtained under mild conditions (room temperature, normal pressure) from good to excellent yields (90%).8-9

 

Acknowledgements

This work was supported by the Russian Science Foundation no. 14-23-00016.

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Figure 1