E
Synlett
S. Pan et al.
Letter
S. Org. Process Res. Dev. 2013, 17, 1247. (n) Chen, C.; Liu, B.;
Chen, W. Synthesis 2013, 45, 3387. (o) Zhang, G.; Lei, J.; Han, X.;
Luan, Y.; Ding, C.; Shan, S. Synlett 2015, 26, 779.
Chem. Commun. 2010, 45, 1103. (f) Hudson, R.; Hamasaka, G.;
Osako, T.; Yamada, Y. M. A.; Li, C.-J.; Uozumi, Y.; Moores, A.
Green Chem. 2013, 15, 2141. (g) Yan, S.; Pan, S.; Osako, T.;
Uozumi, Y. Synlett 2016, 27, 1232.
(
7) For selected examples of Cu/ABNO catalytic systems, see:
(
a) Steves, J. E.; Stahl, S. S. J. Am. Chem. Soc. 2013, 135, 15742.
(18) Synthesis of PS–PEG-TD2–Cu(II) Complexes A–D
A mixture of PS–PED-TD2 (1.0 g) and the appropriate copper
salt (1.0 mmol) in MeOH (10 mL) was stirred at r.t. for 6 h. The
mixture was then filtered, and the resulting resin beads were
washed with MeOH (10 × 10 mL) and dried in vacuo overnight.
The copper loadings of the catalysts were determined by ICP–
AES analysis.
(b) Rogan, L.; Hughes, N. L.; Cao, Q.; Dornan, L. M.; Muldoon, M.
J. Catal. Sci. Technol. 2014, 4, 1720. (c) Steves, J. E.; Preger, Y.;
Martinelli, J. R.; Welch, C. J.; Root, T. W.; Hawkins, J. M.; Stahl, S.
S. Org. Process Res. Dev. 2015, 19, 1548. (d) Steves, J. E.; Stahl, S.
S. J. Org. Chem. 2015, 80, 11184.
(
8) For selected examples of Cu/AZADO catalytic systems, see:
(a) Sasano, Y.; Nagasawa, S.; Yamazaki, M.; Shibuya, M.; Park, J.;
(19) We investigated the solvent effect (toluene, H O, CH CN, and
2
3
Iwabuchi, Y. Angew. Chem. Int. Ed. 2014, 53, 3236. (b) Sasano, Y.;
Kogure, N.; Nishiyama, T.; Nagasawa, S.; Iwabuchi, Y. Chem.
Asian J. 2015, 10, 1004.
THF) on the aerobic oxidation of benzyl alcohol under the stan-
dard conditions. The aerobic oxidation in toluene and H O pro-
2
ceeded well to give benzaldehyde (2a) in 100 and 83% GC yield,
(
9) (a) Sheldon, R. A.; van Bekkum, H. Fine chemicals through hetero-
geneous catalysis; Wiley-VCH: Weinheim, 2001. (b) Barbaro, P.;
Liguori, F. Heterogenized homogeneous catalysts for fine chemi-
respectively, while the reactions in CH CN and THF were slug-
gish (56 and 9% GC yield, respectively). In addition, ICP analysis
3
for the recovered catalyst from the reaction in H O showed that
2
cals production: catalysis by metal complexes;
drecht, 2010.
10) (a) Yang, G.; Ma, J.; Wang, W.; Zhao, J.; Lin, X.; Zhou, L.; Gao, X.
Catal. Lett. 2006, 112, 83. (b) Yang, G.; Zhu, W.; Zhang, P.; Xue,
H.; Wang, W.; Tian, J.; Song, M. Adv. Synth. Catal. 2008, 350, 542.
11) (a) Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. ACS Catal.
3
3Vo.
l
Springer: Dor-
32% of the copper species leached into the solution during the
reaction. On the basis of these results, we selected heptane for
the further investigation.
(
(20) We monitored the formation of benzaldehyde in the aerobic
oxidation of benzyl alcohol under O2 and air. Similar reaction
rates were observed under O and air. Under O : 64% GC yield (2
(
2
2
2
011, 1, 48. (b) Qi, Y.; Luan, Y.; Yu, J.; Peng, X.; Wang, G. Chem.
h), 83% GC yield (4 h), 89% GC yield (8 h), 90 % GC yield (12 h).
Under air: 52% GC yield (2 h), 79% GC yield (4 h), 87% GC yield (8
h), 96% GC yield (12 h).
Eur. J. 2015, 21, 1589. (c) Feng, X.; Xu, C.; Wang, Z.-Q.; Tang, S.-
F.; Fu, W.-J.; Ji, B.-M.; Wang, L.-Y. Inorg. Chem. 2015, 54, 2088.
12) (a) Hu, Z.; Kerton, F. M. Appl. Catal., A 2012, 413–414, 332.
(
(21) We also tested various solvents for washing the recovered cata-
lyst. MTBE was an effective solvent to extract the organic mate-
rials and keep the copper content in the polymer matrix.
(22) Synthesis of Aldehydes 2a–y; General Procedure
A mixture of catalyst PS–PEG-TD2–Cu(OAc)2 (100 mg, 0.05
mmol Cu), BnOH (1a, 27.0 mg, 0.25 mmol), and TEMPO (7.8 mg,
0.05 mmol) in heptane (2.0 mL) was stirred at 80 °C for 24 h
under air (1 atm). The mixture was then cooled and filtered, and
(b) Samanta, S.; Das, S.; Samanta, P. K.; Dutta, S.; Biswas, P. RSC
Adv. 2013, 3, 19455. (c) Gupta, M.; Sharma, P.; Gupta, M.; Gupta,
R. J. Chem. Sci. 2015, 127, 1485. (d) Buxaderas, E.; Graziano-
Mayer, M.; Volpe, M. A.; Radivoy, G. Synthesis 2017, 49, 1387.
13) Zhu, X.; Yang, D.; Wei, W.; Jiang, M.; Li, L.; Zhu, X.; You, J.; Wang,
H. RSC Adv. 2014, 4, 64930.
(
(
(
14) Zhang, G.; Han, X.; Luan, Y.; Wang, Y.; Wen, X.; Xu, L.; Ding, C.;
Gao, J. RSC Adv. 2013, 3, 19255.
the resulting solid material was washed with Et O (3 × 2 mL).
2
15) (a) Chung, C. W. Y.; Toy, P. H. J. Comb. Chem. 2007, 9, 115.
The organic phases were combined, concentrated to a volume of
2 mL, and the internal standard was added to determine the GC
yield. The crude product was purified by column chromatogra-
(b) Akagawa, K.; Takigawa, S.; Mano, E.; Kudo, K. Tetrahedron
Lett. 2011, 52, 770. (c) Yu, J.; Luan, Y.; Qi, Y.; Hou, J.; Dong, W.;
Yang, M.; Yang, M.; Wang, G. RSC Adv. 2014, 4, 55028.
phy [silica gel, hexane–Et O (99:1)]. In the formation of some
2
(
16) Pan, S.; Yan, S.; Osako, T.; Uozumi, Y. ACS Sustainable Chem. Eng.
benzaldehydes, low isolated yields were observed because of
instability of the benzaldehydes on silica gel.
2017, 5, 10722.
(
17) For selected examples, see: (a) Uozumi, Y.; Shibatomi, K. J. Am.
Chem. Soc. 2001, 123, 2919. (b) Uozumi, Y.; Nakao, R. Angew.
Chem. Int. Ed. 2003, 42, 194. (c) Yamada, Y. M. A.; Arakawa, T.;
Hocke, H.; Uozumi, Y. Angew. Chem. Ind. Ed. 2007, 46, 704.
Benzaldehyde (2a)
Colorless oil; yield: 10.8 mg (41%). H NMR (400 MHz, CDCl ):
δ = 10.03 (s, 1 H), 7.89 (dd, J = 8.4, 1.2 Hz, 2 H), 7.64 (t, J = 7.6 Hz,
1 H), 7.56–7.52 (m, 2 H); C NMR (100 MHz, CDCl ): δ = 192.4,
1
3
13
3
(d) Uozumi, Y.; Matsuura, Y.; Arakawa, T.; Yamada, Y. M. A.
136.4, 134.5, 129.7, 129.0.
Angew. Chem. Ind. Ed. 2009, 48, 2708. (e) Hirai, Y.; Uozumi, Y.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2018, 29, A–E