BULLETIN OF THE
Note
KOREAN CHEMICAL SOCIETY
3. (a) G. Crini, Prog. Polym. Sci. 2005, 30, 38. (b) L. Pontoni,
M. Fabbricino, Carbohydr. Res. 2012, 356, 86.
(c) R. A. A. Muzzarelli, Carbohydr. Polym. 2011, 84, 54.
4. (a) A. Pestov, S. Bratskaya, Molecules 2016, 21, 330.
(b) P. Xu, B. Li, L. Wang, C. Qin, L. Zhu, Catal. Commun.
2016, 86, 23. (c) D. H. K. Reedy, S.-K. Lee, J. Appl. Polym.
Sci. 2013, 130, 4542. (d) S. Y. Bratskaya, Y. A. Azarova,
E. G. Matochkina, M. I. Kodess, Y. G. Yatluk, A. V. Pestov,
Carbohydr. Polym. 2012, 87, 869. (e) W. Sajomsang, Car-
bohydr. Polym. 2010, 80, 631. (f) M. Chtchigrovsky,
A. Primo, P. Gonzalez, K. Molvinger, M. Robitzer,
F. Quignard, F. Taran, Angew. Chem. 2009, 121, 6030.
(g) J. J. E. Hardy, S. Hubert, D. J. Macquarrie, A. J. Wilson,
Green Chem. 2004, 6, 53. (h) K. C. Justi, M. C. Laranjeira,
M. A. Neves, A. S. Mangrich, V. T. Favere, Polymers 2004,
45, 6285. (i) C. A. Rodrigues, M. C. M. Laranjeira,
V. T. Favere, E. Stadler, Polymer 1998, 39, 5121.
(j) J. W. Park, K.-H. Choi, K. K. Park, Bull. Kor. Chem. Soc.
1983, 4, 68. (k) J. W. Park, M.-O. Park, K. K. Park, Bull.
Kor. Chem. Soc. 1984, 5, 108.
5. Various protocols were also available. See: Ref. 4g for a rep-
resentative procedure.
6. F. J. Goncalves, F. Kamal, A. Gaucher, R. Gil, F. Bourdreux,
C. Martineau-Corcos, L. V. A. Gurgel, L. F. Gil, D. Prim,
Carbohydr. Polym. 2018, 181, 1206.
7. For the crucial role of the molecular oxygen. See: Refs. 2b,
2g, and 2h.
8. Approximately 50% recovery of the support by weight
as Cu@L1.
comprehensive investigations on copper absorption and
recyclability, the results suggested that Cu-complexation
occurred partially in situ (i.e., during the reaction). The
resulting complex could be reused for the transformation of
boronic acids to the corresponding alcohols.
The IR spectrum corresponding to the resulting copper
complex of L1 hanged only slightly indicating that most of
the imine sites were unaltered. And, comparison of TGA
analyses of L1 and Cu@L1 also verified the copper-
complexation (see Supporting Information).
In conclusion, we have developed a versatile eco-friendly
protocol for the synthesis of substituted phenols via the
copper-catalyzed ipso-hydroxylation of arylboronic acids.10
Use of a biopolymer, modified-chitosan platforms in conjunc-
tion with readily available copper salts under aerobic condi-
tions rendered the protocol economical and environmentally
friendly. The corresponding transformation occurred smoothly
affording the corresponding phenols in moderate to high
yields, regardless of whether the boronic acid substrates bear
electron-withdrawing or electron-donating groups. A chelating
effect depending on the chelating atom, nitrogen versus sulfur,
and copper-complexation with a modified-chitosan backbone
were both observed during the conversion. In addition, thus-
formed copper complex seemed to be a promising a catalyst
for the successive hydroxylation of boronic acid with or with-
out the addition of a copper catalyst.
9. It could be attributed to the deformation of the platform
(Cu@L1) and/or leaching of copper-metal into the solution.
A scrutinized study is currently undertaken in our laboratory
and the results will be reported in due course.
Acknowledgments. This work was supported by Dankook
University in 2016.
Supporting Information. Additional supporting informa-
10. Representative procedure of the ipso-hydroxylation: prepara-
tion of 2d: preparation of p-cresol; a flask was charged with
4-methylphenylboronic acid (1.0 mmol), Cu2O (0.008 g,
0.1 mmol), CTS-Py (100.0 mg), KOH (0.17 g, 3.0 mmol),
and H2O (5.00 mL). Then, the flask was stirred at room tem-
perature in open air for 24 h. At the end of the reaction, the
reaction mixture was filtered and washed with water. Then,
the filtrate was acidified with dilute aqueous HCl and
extracted with diethyl ether (3 × 10 mL). The organic phases
were combined. Combined organic layers were washed with
brine, and then dried over anhydrous Na2SO4. The volatile
components were evaporated under reduced pressure. Filter-
ing through short pad of silica (80% hexanes/ 20% ethyl ace-
tate) afforded 0.0671 g of p-cresol (2d) in 62% isolated yield
as a colorless oily liquid. 1H NMR (500 MHz, CDCl3): δ
(ppm) 7.05 (d, J = 8.0 Hz, 2H), 6.75 (dd, J = 6.5, 2.0 Hz,
2H), 4.95 (br s, 1H), 2.29 (s, 3H); 13C NMR (125 MHz,
CDCl3): δ (ppm) 153.1, 130.1, 130.0, 115.0, 20.5; HRMS
calcd for C7H8O: 108.0575, found: 108.0550.
tion is available in the online version of this article.
References
1. G. Evano, N. Blanchard, Copper-mediated Cross-Coupling
Reactions, John Wiley & Sons, Inc, New Jersey, 2014.
2. (a) R. Borah, E. Saikia, S. J. Bora, B. Chetia, Tetrahedron
Lett. 2017, 58, 1211. (b) S. J. Bora, B. Chetia, J. Org. Chem.
2017, 851, 52. (c) D. Yang, B. An, W. Wei, M. Jiang, J. You,
H. Wang, Tetrahedron 2014, 70, 3630. (d) A. Affrose,
I. A. Azath, A. Dhakshinamoorthy, K. Pitchumani,
J. Molecular Cat. A: Chem. 2014, 395, 500. (e) B. A. Dar,
P. Bhatti, A. P. Singh, A. Lazar, P. R. Sharma, M. Sharma,
B. Singh, Appl. Cat. A: General 2013, 466, 60. (f) H.-L. Qi,
D.-S. Chen, J.-S. Ye, J.-M. Huang, J. Org. Chem. 2013, 78,
7842. (g) K. Inamoto, K. Nozawa, M. Yonemoto, Y. Kondo,
Chem. Commun. 2011, 47, 11775. (h) J. Xu, X. Wang,
C. Shao, D. Su, G. Cheng, Y. Hu, Org. Lett. 2010, 12, 1964.
Bull. Korean Chem. Soc. 2019
© 2019 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4