Organic Letters
Letter
pyridyl)carboxylates and Alkyl Iodides by Use of Zinc Dust and a
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(9) (a) Kazmierski, I.; Bastienne, M.; Gosmini, C.; Paris, J.-M.;
Catalyzed Decarbonylative Trifluoromethylation of Acid Fluoride.
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(14) (a) Jia, X.-G.; Guo, P.; Duan, J.; Shu, X.-Z. Dual nickel and
Lewis acid catalysis for cross-electrophile coupling: the allylation of
aryl halides with allylic alcohols. Chem. Sci. 2018, 9, 640. (b) Yan, X.-
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catalysis. Chem. Sci. 2018, 9, 4529.
(15) When Zn was used instead of Mn, both acid fluoride 1a and
vinyl triflate 2a remained intact, and only a trace of vinyl-H was
observed. Presently, what role is responsible for the low reactivity in
the presence of Zn is unclear. It is possible that an activated nickel
species might not be generated when Zn powder was used in our
catalytic system. For the reductive potential of Zn and Mn (E0 [Zn2+/
Zn] = −0.762 V, E0 [Mn2+/Mn] = −1.182 V), see: Bratsch, S. G.
Standard Electrode Potentials and Temperature Coefficients in Water
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́
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Cobalt Catalysis. J. Org. Chem. 2004, 69, 936. (b) Yin, H.; Zhao, C.;
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J. Nickel-Catalyzed Desymmetrizing Cross-Electrophile Coupling of
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(16) The formation of product 3 is in competition with the
formation of vinyl−vinyl dimer. This might be the reason why inferior
results were obtained when the substrate was changed in some cases.
(17) For a related work, see: Wang, Z.; Wang, X.; Nishihara, Y.
Nickel-catalysed decarbonylative borylation of aroyl fluorides. Chem.
Commun. 2018, 54, 13969.
(18) Because the detection of benzene by GC is interfered by
toluene, DMA (Table 1, entry 14) was used instead of DMA/toluene
(3:2).
(19) Liu, J.; Ren, Q.; Zhang, X.; Gong, H. Preparation of Vinyl
Arenes by Nickel-Catalyzed Reductive Coupling of Aryl Halides with
Vinyl Bromides. Angew. Chem., Int. Ed. 2016, 55, 15544.
(20) It is also possible that the nucleophilic addition of vinyl-Ni(I)
to acid fluoride may give the product. For related work, see: Huang,
Y.-C.; Majumdar, K. K.; Cheng, C.-H. Nickel-Catalyzed Coupling of
Aryl Iodides with Aromatic Aldehydes: Chemoselective Synthesis of
Ketones. J. Org. Chem. 2002, 67, 1682.
(21) The presence of a radical scavenger such as BHT (butylated
hydroxytoluene) or 1,1-diphenylethylene showed no effects on the
reaction of 1a and 2a (see Table S8 in the Supporting Information).
However, the reaction was totally inhibited when 2,2,6,6-tetramethyl-
1-piperidinyloxy (TEMPO, 1.5 equiv) was used, but no radical
trapping product was observed. This might be due to the presence of
a single-electron process capable of reducing oxidized Ni catalyst.
Nevertheless, we currently cannot rule out a radical activation of the
substrate. For related mechanism, see: Biswas, S.; Weix, D. J.
Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile
Coupling of Aryl Halides with Alkyl Halides. J. Am. Chem. Soc. 2013,
135, 16192 (also see ref 5c) .
(10) For selected references, see: (a) Sato, T.; Naruse, K.; Enokiya,
M.; Fujisawa, T. Facile Synthesis of Benzyl Ketones by the Reductive
Coupling of Benzyl Bromide and Acyl Chlorides in the Presence of a
Palladium Catalyst and Zinc Powder. Chem. Lett. 1981, 10, 1135.
(b) Wu, F.; Lu, W.; Qian, Q.; Ren, Q.; Gong, H. Ketone Formation
via Mild Nickel-Catalyzed Reductive Coupling of Alkyl Halides with
Aryl Acid Chlorides. Org. Lett. 2012, 14, 3044. (c) Lu, W.; Liang, Z.;
Zhang, Y.; Wu, F.; Qian, Q.; Gong, H. Gram-Scale Ketone Synthesis
by Direct Reductive Coupling of Alkyl Iodides with Acid Chlorides.
Synthesis 2013, 45, 2234. (d) Cherney, A. H.; Kadunce, N. T.;
Reisman, S. E. Catalytic Asymmetric Reductive Acyl Cross-Coupling:
Synthesis of Enantioenriched Acyclic α, α-Disubstituted Ketones. J.
Am. Chem. Soc. 2013, 135, 7442. (e) Liang, Z.; Xue, W.; Lin, K.;
Gong, H. Nickel-Catalyzed Reductive Methylation of Alkyl Halides
and Acid Chlorides with Methyl p-Tosylate. Org. Lett. 2014, 16, 5620.
(f) Wotal, A. C.; Batesky, D. C.; Weix, D. J. Nickel-Catalyzed
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(11) For selected references, see: (a) Carpino, L. A.; El-Faham, A.
Tetramethylfluoroformamidinium Hexafluorophosphate: A Rapid-
Acting Peptide Coupling Reagent for Solution and Solid Phase
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Pez, G. P.; Pesaresi, R. J.; Prozonic, F. M.; Cheng, H. Bis(2-
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Deoxofluorinating Agent with Enhanced Thermal Stability. J. Org.
Chem. 1999, 64, 7048. (c) Chen, C.; Chien, C.-T.; Su, C.-H.
Preparation of acyl fluorides with hydrogen fluoride-pyridine and 1,3-
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Stable and Crystalline Deoxofluorinating Reagents. Org. Lett. 2009,
11, 5050. (e) Scattolin, T.; Deckers, K.; Schoenebeck, F. Direct
Synthesis of Acyl Fluorides from Carboxylic Acids with the Bench-
Stable Solid Reagent (Me4N)SCF3. Org. Lett. 2017, 19, 5740.
(f) Munoz, S. B.; Dang, H.; Ispizua-Rodriguez, X.; Mathew, T.;
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(12) Zhang, Y.; Rovis, T. A Unique Catalyst Effects the Rapid
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(13) (a) Ogiwara, Y.; Maegawa, Y.; Sakino, D.; Sakai, N. Palladium-
catalyzed Coupling of Benzoyl Halides with Aryltrifluorosilanes
Leading to Diaryl Ketones. Chem. Lett. 2016, 45, 790. (b) Ogiwara,
Y.; Sakino, D.; Sakurai, Y.; Sakai, N. Acid Fluorides as Acyl
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