3
may be involved in this reaction. Moreover, kinetic isotopic
effect (KIE) experiment was carried out under the standard
reaction conditions (eq 2). The result shows a significant isotopic
effect (kH/kD = 2.7), indicating that the C-H bond cleavage is the
rate-determinating step of this transformation.
References and notes
1
2
Larock, R. C. Comprehensive Organic Transformations: A Guide to
Functional Group Preparations; VCH Publishers: New York, 1989.
(a) Fernandez-Bachiller, M. I.; Perez, C.; Monjas, L.; Rademann, J.;
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Srinivasan, B.; Hermanson, D. L.; Bleeker, N. P.; Doshi, J. M.; Tang, R.;
Beck, W. T.; Xing, C. J. Med. Chem. 2011, 54, 5937.
3
(a) Aromí, G.; Barrios, L. A.; Roubeau, O.; Gamez, P. Coord. Chem.
Rev. 2011, 255, 485; (b) Singh, R. P.; Verma, R. D.; Meshri, D. T.;
Shreeve, J. M. Angew. Chem., Int. Ed. 2006, 45, 3584; (c) Tao, G. H.;
Guo, Y.; Joo, Y. H.; Twamley, B.; Shreeve, J. M. J. Mater. Chem. 2008,
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4
5
(a) Seki, M. ACS Catal. 2011, 1, 607; (b) Diers, E.; Kumar, N. Y. P.;
Mejuch, T.; Marek, I.; Ackermann, L. Tetrahedron 2013, 69, 4445; (c)
Wang, L.; Wu, W. T.; Chen, Q.; He, M. Y. Org. Biomol. Chem. 2014,
12, 7923.
Scheme 2. Control experiments.
(a) Lam, P. Y. S.; Clark, C. G.; Saubern, S.; Adams, J.; Winters, M. P.;
Chan, D. M. T.; Combs, A. Tetrahedron Lett. 1998, 39, 2941; (b)
Davydov, D. V.; Beletskaya, I. P.; Semenov, B. B.; Smushkevich, Y. I.
Tetrahedron Lett. 2002, 43, 6217; (c) Fedorov, A. Y.; Finet, J.-P.
Tetrahedron Lett. 1999, 40, 2747; (d) Beletskaya, I. P.; Davydov, D. V.;
Gorovoy, M. S. Tetrahedron Lett. 2002, 43, 6221; (e) ) Li, Y.; Gao, L.-
X.; Han, F.-S. Chem. Commun. 2012, 48, 2719; (f) Liu, C.-Y.; Li, Y.;
Ding, J.-Y.; Dong, D.-W.; Han, F.-S. Chem. Eur. J. 2014, 20, 2373; (g)
Onaka, T.; Umemoto, H.; Miki, Y.; Nakamura, A.; Maegawa, T. J. Org.
Chem. 2014, 79, 6703.
Based on the above results and the similar study that
previously reported,10h,13,14 a possible mechanism was proposed
(Scheme 3). Barton and co-workers confirmed that Fe(III) salt
reacted with TBHP to generate tert-butylperoxy radical and Fe(II)
in their study (step a).12 TBHP can decompose into tert-butoxyl
radical and hydroxyl anion in the presence of the ferrous catalyst
(step b).10h Thus, we believe that one hydrogen atom of ether is
abstracted by either tert-butylperoxy radical or tert-butoxyl
radical to form radical A, followed by oxidation by Fe3+ to
generate oxonium ion B (step c). Meanwhile, deprotonation of
tetrazole gives C (step d). Finally, nucleophilic addition of C to
B provides the desired product (step e).
6
7
Aridoss, G.; Laali, K. K. Eur. J. Org. Chem. 2011, 6343.
Wang, L.; Zhu, K. Q.; Chen, Q.; He, M. Y. J. Org. Chem. 2014, 79,
11780.
8
9
Wang, L.; Zhu, K. Q.; Wu, W. T.; Chen, Q.; He, M. Y. Catal. Sci.
Technol. 2015, 5, 2891.
For representative reviews on iron chemistry, see: (a) Fürstner, A.
Angew.Chem., Int. Ed. 2009, 48, 1364; (b) Czaplik, W. M.; Mayer, M.;
Cvengros, J.; Jacobi von Wangelin, A. ChemSusChem 2009, 2, 396; (c)
Sherry, B. D.; Fu¨rstner, A. Acc. Chem. Res. 2008, 41, 1500; (d) Correa,
A.; Mancheňo, O. G.; Bolm, C. Chem. Soc. Rev. 2008, 37, 1108; (e)
Enthaler, S.; Junge, K.; Beller, M. Angew. Chem., Int. Ed. 2008, 47,
3317; (f) Bolm, C.; Legros, J.; Le Paih, J.; Zani, L. Chem. Rev. 2004,
104, 6217.
10 (a) Jia, F.; Li, Z. Org. Chem. Front. 2014, 1, 194; (b) Gaster, E.; Vainer,
Y.; Regev, A. ; Narute, S.; Sudheendran, K.; Werbeloff, A.; Shalit,
H.; Pappo, D. Angew. Chem., Int. Ed. 2015, 54, 4198; (c) Guo, S.; Li,
Y.; Wang, Y.; Guo, X.; Meng, X.; Chen, B. Adv. Synth. Catal. 2015,
357, 950; (d) Zhao, J.; Fang, H.; Zhou, W.; Han, J.; Pan, Y. J. Org.
Chem. 2014, 79, 3847; (e) Cheng, Y.; Dong, W.; Wang, L.;
Parthasarathy, K.; Bolm, C. Org. Lett. 2014, 16, 2000; (f) Parnes, R.;
Kshirsagar, U.; Werbeloff, A.; Regev, C.; Pappo, D. Org. Lett. 2012, 14,
3324; (g) Liu, H.; Cao, L.; Sun, J.; Fossey, J.; Deng, W. Chem. Commun.
2012, 48, 2674; (h) Pan, S.; Liu, J.; Li, H.; Wang, Z.; Guo, X.; Li, Z.
Org. Lett. 2010, 12,1932; (i) Li, Y.; Li, B.; Lu, X.; Lin, S.; Shi, Z.
Angew. Chem., Int. Ed. 2009, 48, 3817.
Scheme 3. Proposed mechanism.
11 Typical procedure for the synthesis of 3: To a mixture of tetrazole 1
(0.3 mmol), alkyl ethers 2 (3 mmol), and FeCl3.6H2O (4.1 mg, 0.015
mmol, 5 mol%), ethyl acetate (1 mL) was added under nitrogen. Then t-
BuOOH (70% aqueous, 1.5 mmol, 5 equiv) was dropped into the
mixture under nitrogen. The reaction mixture was stirred at 90 oC for 12
h. After reaction, the mixture was allowed to cool to room temperature.
The solvent was then removed under vacuum, and the residue was
purified by silica gel chromatography using a mixture of PE/EA to
afford the desired product 3.
In summary, an iron-catalyzed oxidative dehydrogenative
coupling of ethers with aryl tetrazoles has been developed. This
protocol provides a simple and straightforward approach for the
preparation of pharmaceutically and synthetically useful
tetrazole derivatives. Substrates with a series of functional
groups proceed smoothly to provide the corresponding products
in moderate to good yields.
12 The plausible mechanism for generation of compounds 3n and 3o is
unclear at current stage. Further studies are undergoing in our laboratory.
13 Barton, D. H. R.; Le Gloahec, V. N. Tetrahedron 1998, 54, 15457.
14 Porcheddu, A.; De Luca, L. Adv. Synth. Catal. 2012, 354, 2949.
Acknowledgments
This project was financially supported by the National
Natural Science Foundation of China (NO. 21302014), the
Natural Science Foundation for Colleges and Universities of
Jiangsu Province (13KJB150002), and ordinary university
graduate student research innovation projects of Jiangsu
province (No. KYZZ_0303).