3
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For selected reviews, see: a) M. Majek, A. Jacobi von Wangelin,
Angew. Chem. Int. Ed. 2013, 52, 5919. b) S. Paria, O. Reiser,
ChemCatChem 2014, 6, 2477. c) M. Parasram, V. Gevorgyan,
Chem. Soc. Rev. 2017, 46, 6227.
1
2
3
4
5
6
7
8
9
DMF to provide HCl and radical A.22 There are two possible
pathways for the oxidation from A to B.23 In pathway (i),
CCl3CN oxidizes A, leading to decomposition of the
cyanodichloromethyl radical. The radical reacts with oxygen
to generate HCl.12 In pathway (ii), CuCl2 oxidizes A. The
resulting Cu(I) species reverts back to Cu(II) with the help
of oxidants such as oxygen/HCl or CCl3CN/light.24
Hydrolysis of the iminium intermediate B could also
generate HCl, whereas the reaction of B with halohydrin 2
For selected examples using Cu catalysts, see: a) M. Pirtsch, S.
Paria, T. Matsuno, H. Isobe, O. Reiser, Chem. Eur. J. 2012, 18,
7336. b) Q. M. Kainz, C. D. Matier, A. Bartoszewicz, S. L.
Zultanski, J. C. Peters, G. C. Fu, Science 2016, 351, 681. c) A.
Call, C. Casadevall, F. Acuña-Parés, A. Casitas, J. Lloret-Fillol,
Chem. Sci. 2017, 8, 4739. d) Y. Li, K. Zhou, Z. Wen, S. Cao, X.
Shen, M. Lei, L. Gong, J. Am. Chem. Soc. 2018, 140, 15850.
For selected examples using Ni catalysts, see: a) B. J. Shields, B.
Kudisch, G. D. Scholes, A. G. Doyle, J. Am. Chem. Soc. 2018,
140, 3035. b) C.-H. Lim, M. Kudisch, B. Liu, G. M. Miyake, J.
Am. Chem. Soc. 2018, 140, 7667. c) M. Grübel, I. Bosque, P. J.
Altmann, T. Bach, C. R. Hess, Chem. Sci. 2018, 9, 3313.
For selected examples using Fe catalysts, see: a) A. Gualandi, M.
Marchini, L. Mengozzi, M. Natali, M. Lucarini, P. Ceroni, P. G.
Cozzi, ACS Catal. 2015, 5, 5927. b) S. Parisien-Collette, A. C.
Hernandez-Perez, S. K. Collins, Org. Lett. 2016, 18, 4994.
For selected examples using Cr catalysts, see: a) S. M. Stevenson,
M. P. Shores, E. M. Ferreira, Angew. Chem. Int. Ed. 2015, 54,
6506. b) L. A. Büldt, O. S. Wenger, Chem. Sci. 2017, 8, 7359.
A. Hossain, A. Bhattacharyya, O. Reiser, Science 2019, 364,
eaav9713.
10 leads to byproduct formation. Thus, the addition of H2O to
11 the solvent was important to suppress the side reaction that
12 formed 6.
13
5
6
7
8
9
a) C. Dai, J. M. R. Narayanam, C. R. J. Stephenson, Nat. Chem.
2011, 3, 140. See also: b) P. Zhi, Z.-W. Xi, D.-Y. Wang, W.
Wang, X.-Z. Liang, F.-F. Tao, R.-P. Shen, Y.-M. Shen, New. J.
Chem. 2019, 43, 709.
14
77 10 Léonel et al. reported that excess amount of Fe and Cu powder
78
79
can reduce CBr4 in DMF, see: E. Léonel, J. P. Paugam, J. Y.
Nédélec, J. Org. Chem. 1997, 62, 7061.
15
16
17
Scheme 3. Proposed mechanism.
80 11 a) A. Vilsmeier, A. Haack, Ber. 1927, 60, 119. b) O. Meth-Cohn,
In summary, we have demonstrated catalytic ring-
81
S. P. Stanforth, Comp. Org. Syn. 1991, 2, 777.
82 12 Y. Toda, R. Matsuda, S. Gomyou, H. Suga, Org. Biomol. Chem.
2019, 17, 3825.
18 opening reactions of epoxides 1 using CCl3CN as a visible-
19 light responsive HCl generator for the synthesis of
20 chlorohydrins 2. It was found that copper and iron halide
21 salts enabled the catalysis of the reaction under visible-light
22 irradiation. The synthesis of -chloroamine 4 and -
23 methoxyethylamine 5 was accomplished by the copper
24 catalysis. Efforts are currently underway to broaden the
25 applications of this methodology and to understand the
26 precise reaction mechanism.
83
84 13 Selected examples of catalytic regioselective halohydrin
85
86
87
synthesis, see: a) C. Wang, H. Yamamoto, Org. Lett. 2014, 16,
5937. b) Y. Li, X. Jiang, C. Zhao, X. Fu, X. Xu, P. Tang, ACS
Catal. 2017, 7, 1606.
88 14 Oxygen atmosphere is important for reproducibility and higher
89
yield. See Supporting Information for details.
90 15 The reaction using Ru(bpy)3Cl2•6H2O under argon atmosphere
afforded 2a in 75% NMR yield and 2a’ in 9% NMR yield.
91
92 16 The HCl addition to 3 using FeCl3•6H2O in 1,4-dioxane led to
27
93
94
95
low yield of 4 because of hydrolysis of 3. In contrast, the MeOH
addition using FeCl3•6H2O proceeded without irradiation by blue
LEDs to form 5 in 88% NMR yield.
28 This work was partially supported by the Japan Society for
29 the Promotion of Science (JSPS) through a Grant-in-Aid for
30 Young Scientists (B) (Grant No. JP17K14483). We
31 gratefully acknowledge funding from the alumni association
32 “Wakasatokai” of the Faculty of Engineering, Shinshu
33 University. We are extremely thankful to Tomoyuki
34 Sakamoto (Shinshu University) for his kind support.
35
96 17 In the proposed mechanism by Stephenson et al., DMF attacks
97
98
electrophilic tribromomethyl radical (see, ref 9a). However,
DMF is not necessary for the present reaction.
99 18 The ratio was confirmed by HRMS analysis.
100 19 Zhao et al. observed a kinetic isotope effect value of 4.9 in the
101
102
103
visible-light-driven coupling of DMF and alcohols, see: L. Li, G.
Zhang, A. Savateev, B. Kurpil, M. Antonietti, Y. Zhao, Asian J.
Org. Chem. 2018, 7, 2464.
36 Supporting
37 http://dx.doi.org/10.1246/cl.******.
38
Information
is
available
on
104 20 For a seminal study, see: J. K. Kochi, J. Am. Chem. Soc. 1962, 84,
105
2121.
106 21 The reaction using stoichiometric amount of CuCl2 (100 mol %)
107
108
in the absence of CCl3CN afforded 2a in 11% NMR yield. CuCl2
shows visible-light absorbance (max = 436 nm).
39 References and Notes
40
41
42
43
44
45
46
47
1
a) F.-S. Han, Chem. Soc. Rev. 2013, 42, 5270. b) S. Thapa, B.
Shrestha, S. K. Gurung, R. Giri, Org. Biomol. Chem. 2015, 13,
4816. c) A. Piontek, E. Bisz, M. Szostak, Angew. Chem. Int. Ed.
2018, 57, 11116. d) A. M. F. Phillips, A. J. L. Pombeiro,
ChemCatChem 2018, 10, 3354.
109 22 B. J. Shields, A. G. Doyle, J. Am. Chem. Soc. 2016, 138, 12719.
110 23 The HOMO level of radical A (-4.96 eV) is higher than that of
111
112
DMF (-6.96 eV) on the basis of DFT calculations at the
B3LYP/6-311+G** level (E = 46.1 kcal/mol).
113 24 The additional results are shown in Supporting Information.
2
a) C. K. Prier, D. A. Rankic, D. W. C. MacMillan, Chem. Rev.
2013, 113, 5322. b) D. Ravelli, S. Protti, M. Fagnoni, Chem. Rev.
2016, 116, 9850.