Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes

Steffen A, Sladek MI, Braun T, Neumann B, Stammler H-G (2005)
ORGANOMETALLICS 24(16): 4057-4064.

Journal Article | Published | English

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Abstract
Treatment of [Ni(COD)(2)] (COD = 1,5-cyclooctadiene) with 5-chloro-2,4,6-trifluoropyrimidine (1) in the presence of (PPr3)-Pr-i or PPh3 effects the formation of the fluoro complexes trans[NiF(4-C4N2ClF2)(PiPr3)2] (3) and trans- [NiF((4)-C4N2ClF2)(PPh3)(2)] (4). The chloro complex trans- [NiCl(4-C4N2ClF2)(PPh3)(2)] (5) can be prepared by reaction of 4 with Me3SiCl. In contrast, a reaction of 1 with [Pd(PPh3)(4)] leads to the insertion of a {Pd(PPh3)(2)}unit into the C-Cl bond yielding trans-[PdCl(5-C4N2F3)(PPh3)(2)] (6). Treatment of 4 with an excess of TolB(OH)2 at 273 K results in the slow formation of trans- [NiF(4-C(4)N(2)TolCIF)(PPh3)(2)] (7) and subsequently 5-chloro-2-fluoro-4,6-ditolylpyrimidine (8). (quenching of a solution of 7 with Me3SiCl leads to the chloro derivative trans- [NiCl(4-C(4)N(2)TolClF)(PPh3)(2)] (9). Treatment of 4 with PhB(OH)2 followed by addition of Me3SiCl gives the complex trans-[NiCl(4-C4N2PhClF)(PPh3)2] (10). In catalytic experiments, 1 is converted with the boronic acids TolB(OH)(2), PhB(OH)(2), and p-F3CC6H4B(OH)(2) into the 5-chloro-2-fluoro-4,6-diarylpyrimidines 8, 11, and 12 in 73%, 88%, and 37% yield, respectively, when 10% of 4 is employed as catalyst. The molecular structures of the complexes 5, 6, and 10 have been determined by X-ray crystallography. The studies reported in this paper represent the first catalytic C-C coupling reactions involving the activation of a C-F bond in the presence of a thermodynamically weaker C-Cl bond. They provide a route to access 5-chloro-2-fluoro-4,6-diarylpyrimidines, which have not been described before. There is considerable evidence that the presence of the fluoro ligand in 4 is crucial for the transmetalation step to occur and for the catalytic cycle to proceed.
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Steffen A, Sladek MI, Braun T, Neumann B, Stammler H-G. Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes. ORGANOMETALLICS. 2005;24(16):4057-4064.
Steffen, A., Sladek, M. I., Braun, T., Neumann, B., & Stammler, H. - G. (2005). Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes. ORGANOMETALLICS, 24(16), 4057-4064.
Steffen, A., Sladek, M. I., Braun, T., Neumann, B., and Stammler, H. - G. (2005). Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes. ORGANOMETALLICS 24, 4057-4064.
Steffen, A., et al., 2005. Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes. ORGANOMETALLICS, 24(16), p 4057-4064.
A. Steffen, et al., “Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes”, ORGANOMETALLICS, vol. 24, 2005, pp. 4057-4064.
Steffen, A., Sladek, M.I., Braun, T., Neumann, B., Stammler, H.-G.: Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes. ORGANOMETALLICS. 24, 4057-4064 (2005).
Steffen, A, Sladek, MI, Braun, T, Neumann, Beate, and Stammler, Hans-Georg. “Catalytic C-C coupling reactions at nickel by C-F activation of a pyrimidine in the presence of a C-Cl bond: The crucial role of highly reactive fluoro complexes”. ORGANOMETALLICS 24.16 (2005): 4057-4064.
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