ACS Catalysis
Letter
Minisci C−H Alkylation of N-Heteroarenes using Boronic Acids and
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(9) (a) Jin, J.; MacMillan, D. W. C. Alcohols as Alkylating Agents in
Heteroarene C−H Functionalization. Nature 2015, 525, 87−90.
(b) McCallum, T.; Pitre, S. P.; Morin, M.; Scaiano, J. C.; Barriault, L.
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(19) For examples of secondary alkyl oxalate salts as radical
precursors, see Table S2 of the Supporting Information.
(20) For detailed computational studies on the Minisci reaction, see:
(10) (a) Cheng, W.-M.; Shang, R.; Fu, M.-C.; Fu, Y. Photoredox-
Catalysed Decarboxylative Alkylation of N-Heteroarenes with N-
(Acyloxy)phthalimides. Chem. - Eur. J. 2017, 23, 2537−2541.
(b) Sherwood, T. C.; Li, N.; Yazdani, A. N.; Dhar, T. G. M.
Organocatalyzed, Visible-Light Photoredox-Mediated, One-Pot Min-
isci Reaction Using Carboxylic Acids via N-(Acyloxy)phthalimides. J.
Org. Chem. 2018, 83, 3000−3012. (c) Proctor, R. S. J.; Davis, H. J.;
Phipps, R. J. Catalytic enantioselective Minisci-Type Addition to
Heteroarenes. Science 2018, 360, 419−422.
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Nuhant, P.; Oderinde, M. S.; Genovino, J.; Juneau, A.; Gagne, Y.;
Allais, C.; Chinigo, G. M.; Choi, C.; Sach, N. W.; Bernier, L.; Fobian,
Y. M.; Bundesmann, M. W.; Khunte, B.; Frenette, M.; Fadeyi, O. O.
Visible-Light-Initiated Manganese Catalysis for C−H Alkylation of
Heteroarenes: Applications and Mechanistic Studies. Angew. Chem.,
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(21) Reactions that were unsuccessful or that proceeded in yields
lower than 30% are summarized in Table S3 of the Supporting
Information.
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(11) Gutierrez-Bonet, A.; Remeur, C.; Matsui, J. K.; Molander, G. A.
Late-Stage C−H Alkylation of Heterocycles and 1,4-Quinones via
Oxidative Homolysis of 1,4-Dihydropyridines. J. Am. Chem. Soc. 2017,
139, 12251−12258.
(22) Pitre, S. P.; McTiernan, C. D.; Scaiano, J. C. Understanding the
Kinetics and Spectroscopy of Photoredox Catalysis and Transition-
Metal-Free Alternatives. Acc. Chem. Res. 2016, 49, 1320−1330.
(23) Pitre, S. P.; McTiernan, C. D.; Ismaili, H.; Scaiano, J. C.
Mechanistic Insights and Kinetic Analysis for the Oxidative
Hydroxylation of Arylboronic Acids by Visible Light Photoredox
Catalysis: A Metal-Free Alternative. J. Am. Chem. Soc. 2013, 135,
13286−13289.
(24) For the chemical actinometer employed in our quantum yield
calculations, see: Pitre, S. P.; McTiernan, C. D.; Vine, W.; DiPucchio,
R.; Grenier, M.; Scaiano, J. C. Visible-Light Actinometry and
Intermittent Illumination as Convenient Tools to Study Ru(bpy)3Cl2
Mediated Photoredox Transformations. Sci. Rep. 2015, 5, 16397.
(12) We are aware of the following reports that document a slightly
broader scope: (a) Fiorentino, M.; Testaferri, L.; Tiecco, M.; Troisi,
L. Structural Effects on the Reactivity of Carbon Radicals in
Homolytic Aromatic Substitution. Part 4. The Nucleophilicity of
Bridgehead Radicals. J. Chem. Soc., Perkin Trans. 2 1977, 2, 87−93.
(b) Togo, H.; Aoki, M.; Yokoyama, M. Alkylation of Aromatic
Heterocycles with Oxalic Acid Monoalkyl Esters in the Presence of
Trivalent Iodine Compounds. Chem. Lett. 1991, 20, 1691−1694.
(c) Coppa, F.; Fontana, F.; Lazzarini, E.; Minisci, F.; Pianese, G.;
Zhao, L. A Novel, Simple and Cheap Source of Alkyl Radicals from
Alcohols, Useful for Heteroaromatic Substitution. Chem. Lett. 1992,
21, 1295−1298. (d) McCallum, T.; Barriault, L. Direct Alkylation of
Heteroarenes with Unactivated Bromoalkanes using Photoredox Gold
Catalysis. Chem. Sci. 2016, 7, 4754−4758. (e) Genovino, J.; Lian, Y.;
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Zhang, Y.; Hope, T. O.; Juneau, A.; Gagne, Y.; Ingle, G.; Frenette, M.
Metal-Free-Visible Light C−H Alkylation of Heteroaromatics via
Hypervalent Iodine-Promoted Decarboxylation. Org. Lett. 2018, 20,
3229−3232. (f) Garza-Sanchez, R. A.; Tlahuext-Aca, A.; Tavakoli, G.;
Glorius, F. Visible Light-Mediated Direct Decarboxylative C−H
Functionalization of Heteroarenes. ACS Catal. 2017, 7, 4057−4061.
(g) Sun, A. C.; McClain, E. J.; Beatty, J. W.; Stephenson, C. R. J.
Visible Light-Mediated Decarboxylative Alkylation of Pharmaceuti-
cally Relevant Heterocycles. Org. Lett. 2018, 20, 3487−3490.
(h) Revil-Baudard, V. L.; Vors, J.-P.; Zard, S. Z. Xanthate-Mediated
Incorporation of Quaternary Centers into Heteroarenes. Org. Lett.
2018, 20, 3531−3535.
(13) For a recent photochemical variant of Togo’s original work, see:
Zhang, X.-Y.; Weng, W.-Z.; Liang, H.; Yang, H.; Zhang, B. Visible-
Light-Initiated, Photocatalyst-Free Decarboxylative Coupling of
Carboxylic Acids with N-Heterocycles. Org. Lett. 2018, 20, 4686−
4690.
(14) (a) Nawrat, C. C.; Jamison, C. R.; Slutskyy, Y.; MacMillan, D.
W. C.; Overman, L. E. Oxalates as Activating Groups for Alcohols in
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ACS Catal. 2019, 9, 3413−3418