8800
J. He et al. / Tetrahedron 64 (2008) 8797–8800
OH
OH
4.2.3.1.
6-Methoxy-2-methyl-2-phenylbenzofuran-3(2H)-one
7.59–7.54 (m, 3H), 7.37–7.26 (m,
3H), 6.67–6.64 (m, 2H), 3.89 (s, 3H), 1.83 (s, 3H); 13C NMR (75 MHz,
CDCl3) 199.2, 173.6, 168.5, 138.5, 128.4, 127.9, 126.1, 124.6, 112.3,
(13). 1H NMR (300 MHz, CDCl3)
d
S
H
N
d
O
1
111.8, 96.0, 90.4, 55.8, 24.2; IR (KBr) 1708, 1613, 1443, 1284,
1203 cmꢁ1; MS m/z (%) 254 (Mþ, 60), 253 (24), 151 (100), 134 (43),
124 (30), 106 (37), 77 (46), 63 (51). HRMS (ESI) calcd for C16H15O3
[MþH]þ 255.1016, found 255.1011.
H
O
S
O
N
Ph
N
Ph
O
8
23
9
4.2.3.2.
(300 MHz, CDCl3)
J¼7.5 Hz, 1H), 2.29–2.21 (m, J¼7.5, 1.7 Hz, 2H), 0.91 (t, J¼7.5 Hz, 3H);
13C NMR (75 MHz, CDCl3)
201.5, 171.6, 138.0, 137.1, 128.4, 127.8,
2-Ethyl-2-phenylbenzofuran-3(2H)-one (21). 1H NMR
7.67–7.61 (m, 4H), 7.40–7.25 (m, 4H), 7.07 (t,
d
O
H
HO
N
O
d
S
O
124.8, 121.9, 120.3, 113.1, 92.6, 31.7, 7.9; IR (KBr) 1721, 1612, 1462,
1323, 1299, 1246, 756 cmꢁ1; MS m/z (%) 238 (Mþ, 41), 223 (55), 209
(100), 121 (52), 117 (52), 115 (68), 77 (94), 63 (52). HRMS (ESI) calcd
for C16H15O2 [MþH]þ 239.1067, found 239.1070.
S
O
Ph
Ph
OH
HO
24
26
S
N
O
Acknowledgements
H
O
We are grateful for the generous financial support by the Special
Doctorial Program Funds of the Ministry of Education of China
(20040730008), NSFC (QT program, No. 20572037), NCET-05-0879,
the key grant project of Chinese ministry of Education (No. 105169),
and Gansu Science Foundation (3ZS051-A25-004).
Ph
25
Scheme 5. Proposed catalytic cycle.
CHO
O
References and notes
path B
CHO
1. Seebach, D. Angew. Chem., Int. Ed. Engl. 1979, 18, 239.
H
2. (a) Ukai, T.; Tanaka, R.; Dokawa, T. J. Pharm. Soc. Jpn. 1943, 63, 296; (b) Ardu-
engo, A. J.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1991, 113, 361.
3. For recent reviews see: (a) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41,
1290; (b) Nair, V.; Bindu, S.; Sreekumar, V. Angew. Chem., Int. Ed. 2004, 43, 5130;
(c) Enders, D.; Balensiefer, T. Acc. Chem. Res. 2004, 37, 534.
4. (a) Herrmann, W. A.; Goossen, L. J.; Artus, G. R. J.; Kocher, C. Organometallics
1997, 16, 2472; (b) Kerr, M. S.; Read de Alaniz, J.; Rovis, T. J. Org. Chem. 2005, 70,
5725.
Ph
9
H
O
O
CH2D
Ph
30 mol % cat. 1
CH3
Ph
O
D
30 mol % DBU
O
O
O
30
8
Ph
Tos
27
5. Johnson, J. S. Angew. Chem., Int. Ed. 2004, 43, 1326.
not obtained
6. (a) Sheehan, J. C.; Hara, T. J. Org. Chem. 1974, 39, 1196; (b) Enders, D.; Kallfass, U.
Angew. Chem., Int. Ed. 2002, 41, 1743; (c) Hachisu, Y.; Bode, J. W.; Suzuki, K. J. Am.
Chem. Soc. 2003, 125, 8432; (d) Enders, D.; Niemeier, O.; Balensiefer, T. Angew.
Chem., Int. Ed. 2006, 45, 1463.
7. (a) Murry, J. A.; Frantz, D. E.; Soheili, A.; Tillyer, R.; Grabowski, E. J. J.; Reider, P. J.
J. Am. Chem. Soc. 2001, 123, 9696; (b) Kerr, M. S.; Read de Alaniz, J.; Rovis, T.
J. Am. Chem. Soc. 2002, 124, 10298; (c) Mattson, A. E.; Bharadwaj, A. R.; Scheidt,
K. A. J. Am. Chem. Soc. 2004, 126, 2314; (d) Kerr, M. S.; Rovis, T. J. Am. Chem. Soc.
2004, 126, 8876.
O
CHO
O
Ph
O
path A
O
Tos
D
D
28
Ph
29
Scheme 6. The labeling experiment.
8. (a) Mattson, A. E.; Scheidt, K. A. Org. Lett. 2004, 6, 4363; (b) Mennen, S. M.;
Gipson, J. D.; Kim, Y. R.; Miller, S. J. J. Am. Chem. Soc. 2005, 127, 1654; (c) Liu, Q.;
Rovis, T. J. Am. Chem. Soc. 2006, 128, 2552; (d) Mattson, A. E.; Zuhl, A. M.;
Reynolds, T. E.; Scheidt, K. A. J. Am. Chem. Soc. 2006, 128, 4932.
9. Other reactions have been developed. For internal redox of unsaturated alde-
hydes, see: (a) Sohn, S. S.; Rosen, E. L.; Bode, J. W. J. Am. Chem. Soc. 2004, 126,
14370; (b) He, M.; Bode, J. W. Org. Lett. 2005, 7, 3131; For internal redox of
epoxyaldehydes, see: (c) Chow, K. Y.-K.; Bode, J. W. J. Am. Chem. Soc. 2004, 126,
8126; For internal redox of haloaldehydes, see: (d) Reynolds, N. T.; Read de
Alaniz, J.; Rovis, T. J. Am. Chem. Soc. 2004, 126, 9518; For tandem reaction, see:
(e) Ye, W.; Cai, G.; Zhuang, Z.; Jia, X.; Zhai, H. Org. Lett. 2005, 7, 3769; (f) Maki, B.
E.; Chan, A.; Philips, E. M.; Scheidt, K. A. Org. Lett. 2007, 9, 371.
10. He, J.; Zheng, J.; Liu, J.; She, X.; Pan, X. Org. Lett. 2006, 8, 4637.
11. Breslow, R. J. Am. Chem. Soc. 1958, 80, 3719.
filtered, and concentrated under reduced pressure. Purification by
flash column chromatography (silica gel, elution with 20:1 petro-
leum ether/EtOAc) afforded enol ether 9 (108 mg, 96%) as yellow oil.
4.2.3. Synthesis of benzofuranones
A round bottom flask was charged with DBU (53 mg, 0.35 mmol)
in 25 ml xylene and thiazolium salt (36 mg, 0.125 mmol) was
added. The resulting mixture was stirred at 50 ꢀC for 30 min and
then substrate (0.5 mmol) was added. The reaction mixture was
stirred for 12 h at reflux temperature. The solvent was removed
under ordinary pressure; the residue was chromatographed using
20:1 petroleum ether/EtOAc to afford the product.
12. Stetter, H. Angew. Chem., Int. Ed. Engl. 1976, 15, 639.
13. Thiazolium salt 1 and DBU of 30 mol % were mixed in xylene and stirred at
50 ꢀC for 30 min, and then substrate was added. The reaction mixture was
stirred for 12 h at reflux temperature.