D
Y. Wang et al.
Letter
Synlett
R.-B.; Yang, S.-D. Tetrahedron 2012, 68, 5216. (f) Althagafy, H. S.;
Meza-Aviña, M. E.; Oberlies, N. H.; Croatt, M. P. J. Org. Chem.
2013, 78, 7594.
R1
R1
R1
HFIPH2
DDQ
OH
O
O
HDDQ
(9) (a) El-Seedi, H. R.; Yamamura, S.; Nishiyama, S. Tetrahedron
2002, 58, 7485. (b) Kirste, A.; Schnakenburg, G.; Stecker, F.;
Fischer, A.; Waldvogel, S. R. Angew. Chem. Int. Ed. 2010, 49, 971.
(c) El-Seedi, H. R.; Yamamura, S.; Nishiyama, S. Tetrahedron Lett.
2002, 43, 3301. (d) Okada, Y.; Yoshioka, T.; Koike, M.; Chiba, K.
Tetrahedron Lett. 2011, 52, 4690. (e) Chiba, K.; Fukuda, M.; Kim,
S.; Kitano, Y.; Tada, M. J. Org. Chem. 1999, 64, 7654. (f) Kim, S.;
Noda, S.; Hayashi, K.; Chiba, K. Org. Lett. 2008, 10, 1827.
(10) Zhao, Y.; Huang, B.; Yang, C.; Li, B.; Xia, W. Synthesis 2015, 47,
2731.
1
5
4
R2
R4
[3+2] radical cycloaddition
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R1
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R3
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(11) Huang, Z.; Jin, L.; Feng, Y.; Peng, P.; Yi, H.; Lei, A. Angew. Chem.
Int. Ed. 2013, 52, 7151.
Scheme 3 Plausible reaction mechanism
(12) Liang, K.; Yang, J.; Tong, X.; Shang, W.; Pan, Z.; Xia, C. Org. Lett.
2016, 18, 1474.
(13) Liang, K.; Wu, T.; Xia, C. Org. Biomol. Chem. 2016, 14, 4690.
(14) Meng, L.; Zhang, G.; Liu, C.; Wu, K.; Lei, A. Angew. Chem. Int. Ed.
2013, 52, 10195.
(15) Shama, S.; Parumala, S. K. R.; Peddinti, R. K. Synlett 2017, 28,
239.
approach features catalyst-free conditions, a broad sub-
strate scope, and short reaction times, which suggests it has
good potential for practical application.
(16) Song, T.; Zhou, B.; Peng, G.-W.; Zhang, Q.-B.; Wu, L.-Z.; Liu, Q.;
Wang, Y. Chem. Eur. J. 2014, 20, 678.
Funding Information
(17) (a) Gaster, E.; Vainer, Y.; Regev, A.; Narute, S.; Sudheendran, K.;
Werbeloff, A.; Shalit, H.; Pappo, D. Angew. Chem. Int. Ed. 2015,
ó54, 4198. (b) Elsler, B.; Wiebe, A.; Schollmeyer, D.; Dyballa, K.
M.; Franke, R.; Waldvogel, S. R. Chem. Eur. J. 2015, 21, 12321.
(c) Dohi, T.; Yamaoka, N.; Kita, Y. Tetrahedron 2010, 66, 5775.
(d) Libman, A.; Shalit, H.; Vainer, Y.; Narute, S.; Kozuch, S.;
Pappo, D. J. Am. Chem. Soc. 2015, 137, 11453.
(18) Dihydrobenzofurans 3a–q; Typical Procedure
A 5 mL cylindrical glass bottle equipped with magnetic stirrer
bar was charged with the appropriate phenol 1 (0.15 mmol),
styrene 2 (0.3 mmol), and HFIP (1.5 mL). When the phenol and
the styrene were completely dissolved in the HFIP, DDQ (1.2
equiv) was gradually added. The mixture was stirred at r.t. for
15 min, and then concentrated under vacuum. The crude
product was purified by flash chromatography [silica gel, PE–
EtOAc (50:1)].
We are grateful for financial support from the Open Foundation of
Key Laboratory of Synthetic and Natural Functional Molecule Chemis-
try of the Ministry of Education of China, Science and Technology Pro-
gram of Xi'an City and Shaanxi Province (2017KW-066).2(
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References and Notes
(1) Kshirsagar, U. A.; Regev, C.; Parnes, R.; Pappo, D. Org. Lett. 2013,
15, 3174.
(2) Varadaraju, T. G.; Hwu, J. R. Org. Biomol. Chem. 2012, 10, 5456.
(3) Blum, T. R.; Zhu, Y.; Nordeen, S. A.; Yoon, T. P. Angew. Chem. Int.
Ed. 2014, 53, 11056.
(4) Magoulas, G. E.; Papaioannou, D. Molecules 2014, 19, 19769.
(5) Cui, N.; Zhao, Y.; Wang, Y. Chin. J. Org. Chem. 2017, 37, 20.
(6) (a) Wang, S.; Gates, B. D.; Swenton, J. S. J. Org. Chem. 1991, 56,
1979. (b) Dohi, T.; Nakae, T.; Toyoda, Y.; Koseki, D.; Kubo, H.;
Kamitanaka, T.; Kita, Y. Heterocycles 2015, 90, 631. (c) Mohr, A.
L.; Lombardo, V. M.; Arisco, T. M.; Morrow, G. W. Synth.
Commun. 2009, 39, 3845.
5-Methoxy-2-phenyl-2,3-dihydro-1-benzofuran (3a)
Yellow oil; yield: 30 mg (88%). 1H NMR (400 MHz, CDCl3):
δ = 7.46–7.30 (m, 5 H), 6.83–6.76 (m, 2 H), 6.72 (dd, J = 8.7, 2.6
Hz, 1 H), 5.75 (t, J = 8.8 Hz, 1 H), 3.78 (s, 3 H), 3.61 (dd, J = 15.7,
9.3 Hz, 1 H), 3.21 (dd, J = 15.7, 8.2 Hz, 1 H). 13C NMR (100 MHz,
CDCl3): δ = 154.3, 153.78, 142.0, 128.7, 128.0, 127.5, 125.8,
113.0, 111.2, 109.2, 84.2, 56.1, 38.9. HRMS (ESI+): m/z [M + Na]+
calcd for C15H14NaO2: 249.0886; found: 249.0888.
2-(4-tert-Butylphenyl)-5-methoxy-2,3-dihydro-1-benzofu-
ran (3f)
Pale-yellow solid; yield: 38 mg (89%). 1H NMR (400 MHz,
CDCl3): δ = 7.39 (d, J = 8.3 Hz, 2 H), 7.34 (d, J = 8.3 Hz, 2 H), 6.83–
6.72 (m, 2 H), 6.69 (dd, J = 8.6, 2.2 Hz, 1 H), 5.71 (t, J = 8.7 Hz, 1
H), 3.76 (s, 3 H), 3.57 (dd, J = 15.7, 9.3 Hz, 1 H), 3.22 (dd, J = 15.7,
8.2 Hz, 1 H), 1.31 (s, 9 H). 13C NMR (100 MHz, CDCl3): δ = 154.2,
153.8, 151.0, 138.8, 127.7, 125.7, 125.5, 112.9, 111.2, 109.2,
84.2, 56.0, 38.6, 34.6, 31.3. HRMS (ESI+): m/z [M + Na]+ calcd for
(7) Alvey, L.; Prado, S.; Huteau, V.; Saint-Joanis, B.; Michel, S.; Koch,
M.; Cole, S. T.; Tillequin, F.; Janin, Y. L. Bioorg. Med. Chem. 2008,
16, 8264.
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Tetrahedron 2013, 69, 653. (b) Sako, M.; Hosokawa, H.; Ito, T.;
Iinuma, M. J. Org. Chem. 2004, 69, 2598. (c) Takaya, Y.;
Terashima, K.; Ito, J.; He, Y. H.; Tateoka, M.; Yamaguchi, N.; Niwa,
M. Tetrahedron 2005, 61, 10285. (d) Bruschi, M.; Orlandi, M.;
Rindone, B.; Rummakko, P.; Zoia, L. J. Phys. Org. Chem. 2006, 19,
592. (e) Wang, G.-W.; Wang, H.-L.; Capretto, D. A.; Han, Q.; Hua,
C
19H22NaO2: 305.1512; found: 305.1512.
2-Mesityl-5-methoxy-2,3-dihydro-1-benzofuran (3g)
colorless oil; yield: 28 mg (69%). 1H NMR (400 MHz, CDCl3):
δ = 6.86 (s, 2 H), 6.80 (s, 1 H), 6.73 (d, J = 8.7 Hz, 2 H), 6.11 (t, J =
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–E