502
L. Xu, X. Huang / Tetrahedron Letters 49 (2008) 500–503
MCPBA
TsCl
Br
TsN
TsN
O
NH2
O
H
H
K2CO3
pyridine
O
C
HO
H3O
80%
Cp2TiCl
THF
CuBr, HCHO
i-Pr2NH
TsN
N
Ts
N
Ts
9 (55:45)
8
Scheme 3.
1993, 1032–1033; (d) Satoshi, Y.; Tomoko, I.; Takuya, K.; Toshiya,
M. Biosci., Biotechnol., Biochem. 2004, 183–192.
Acknowledgement
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We are grateful to the National Natural Science Foun-
dation of China (Project No. 20332060, 20472072) for its
financial support.
´
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Int. Ed. 1998, 37, 101–103; (c) Fernandez-Mateos, A.; Martın de la
References and notes
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Nava, E.; Pascual Coca, G.; Ramos Silvo, A.; Rubio Gonza lez, R.
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Fernandez-Mateos, A.; Mateos Buron, L.; Rabanedo Clemente, R.;
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Ramos Silvo, A. I.; Rubio Gonzalez, R. Synlett 2004, 1011–1014.
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14. The epoxyallene ethers were prepared from the corresponding allenyl
alcohols treated with NaH, then added epichlorohydrin and refluxed.
15. The radical initiator Cp2TiCl was generated in situ from commercially
available titanocene dichloride (Cp2TiCl2) and Zn dust in tetra-
hydrofuran under nitrogen. See Ref. 8a and references cited therein.
16. Typical procedure for radical cyclization reaction. Preparation of 4a: A
solution of titanocene dichloride (0.5 g, 2 mmol) in dry tetrahydrofu-
ran (15 mL) was stirred with activated zinc dust (0.39 g, 6 mmol) for
1 h under nitrogen (activated zinc dust was prepared by washing 20 g
of commercially available zinc dust with 60 mL of 4 N HCl and
thoroughly washing with water and finally with dry acetone and then
drying in vacuo). The resulting green solution was then added
dropwise to a stirred solution of epoxide 1a (0.18 g, 1 mmol) in dry
tetrahydrofuran (10 mL) at room temperature under nitrogen during
15 min. The reaction mixture was stirred for an additional 1 h and
quenched with 10% H2SO4 (15 mL). Most of the solvent was removed
under reduced pressure, and the residue was extracted with diethyl
ether (4 · 15 mL). The ether layer was washed with saturated NaHCO3
(2 · 10 mL) and dried (Na2SO4). After removal of solvent, the crude
residue was purified by column chromatography over silica gel (25%
ethyl acetate/light petroleum) to afford alcohol 4a (0.15 g, 84%) as a
viscous liquid. Compound 4a: 1H NMR (400 MHz, CDCl3) d 5.76–
5.62 (m, 1H), 5.08–5.04 (m, 2H), 3.95–3.89 (m, 1H), 3.68–3.63 (m, 1H),
3.61–3.57 (m, 1H), 3.52–3.47 (m, 1H), 2.71–2.66 (m, 0.36 H), 2.59–2.54
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