Yu. H. Budnikova et al.
SHORT COMMUNICATION
oxidation of 2-phenylpyridine/perfluoroheptanoic acid (1:1) that clearly generate high oxidation state nickel and palla-
in the presence of various catalysts led to direct perfluoro- dium complexes. Only the electrocatalyst and the substrates
alkylation products through a decarboxylative pathway, as are required for the reaction to occur. To broaden the scope
described in Scheme 4. Good yields {81% for Pd2(OAc)2- of the proposed method we are planning to examine various
(PhPy)2 and 85% for [Ni(bpy)3]2+} were obtained demon- substrates for C–H activation like substituted arenes that
strating that the perfluoroalkyl carboxylic acids are in fact have been previously studied,[5,10] as well as more sophisti-
better substrates than the perfluoroalkyl bromide in direct cated structures. The mechanisms of these redox processes
functionalization reactions.
are currently under study in efforts to optimize the reac-
tions even further.
Experimental Section
Preparative Electrolysis: An electrochemical cell was loaded with a
mixture of 2-phenylpyridine (7 mmol), 6H-perfluorohexyl bromide
or perfluoroheptanoic acid (14 mmol) and the catalyst (0.7 mmol)
in acetonitrile (70 mL). Electrolysis was conducted in a divided cell
at a platinum anode with the use of Et4NBF4 as the background
electrolyte. The mixture was stirred with a magnetic stirrer and a
constant stream of argon. 2F per RfX (X = Br, COOH) electricity
was passed through the electrolyte. At the end of electrolysis, the
reaction mixture was placed in 250-mL flask, the solvent was re-
moved on a rotary evaporator, and the residue was washed with
water and extracted with benzene (3ϫ50 mL). The organic layer
was dried with MgSO4, then the solvent was removed, and the resi-
due was washed with diethyl ether and dried in a vacuum. The
product was purified by silica gel column chromatography (ethyl
acetate/hexane).
Scheme 4. Electrooxidative ortho-fluoroalkylation of 2-phenylpyr-
idine with perfluoroheptanoic acid.
We speculate that intermediate 3 is generated on route to
product formation. The presence of 3 in the reaction mix-
tures was confirmed by GC–MS. When Pd(OAc)2 was used
as a catalyst there were three products in the reaction mix-
ture: the intermediate palladium complex {fragment peaks
in the mass spectrum at 106 [Pd], 154 [C6H4C6H4N], 319
[C6H4C6H4NPdOAc], 378 [C6H4C6H4NPd(OAc)2]}; ortho-
carboxylated species 3 with m/z = 517 [M]+, and oxidation
product 4 with m/z = 473 [M]+). An increase in electrolysis
time leads to final product 4. A summary of the results for
the MII/MIII-catalyzed ortho-fluoroalkylation of 2-phenyl-
pyridine is shown in Table 1.
Supporting Information (see footnote on the first page of this arti-
cle): General information, characterization data, and copies of the
1H NMR, 13C NMR, and 19F NMR spectra of new compounds.
Acknowledgments
This work was supported by the Russian Foundation for Basic Re-
search (RFBR) (grant 11–03–92662-MCX_a). D. A. V. thanks the
U.S. National Science Foundation (NSF) (grant CHE-1124619) for
support of this work.
Table 1. Products of ortho-C–H substitution in Ph-Py with different
catalysts.
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Conclusions
The electrocatalytic syntheses of fluoroalkylated 2-phen-
ylpyridine proceeded under mild conditions at potentials
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