N. Liu et al. / Tetrahedron 67 (2011) 4385e4390
4389
1333, 1161, 1071, 796 cmꢀ1. HRMS (ESI) for C13H12BrNO4SþNa
(Mþ23), 379.9563 (calcd), found 379.9582.
664 cmꢀ1. HRMS (ESI) for C18H28BrNO3SSiþNa (Mþ23), 468.0635
(calcd), found 468.0641.
4.2.4. Synthesis of oxazolidone 19. To a solution of imide 18
(0.1 mmol) in chloroform directly purchased from Fisher was added
NBS (23 mg, 0.12 mmol) and DABCO (2 mg, 20 mol %). The reaction
mixture was stirred at room temperature until the starting material
disappeared as indicated by TLC. The reaction mixture was con-
centrated under vacuum and directly purified by flash column
chromatography eluting with ethyl acetate and hexanes to give
oxazolidone 19 (18.2 mg) in 48% yield and byproduct 20 (17.1 mg) in
45% yield.
4.2.7. Synthesis of aziridine 24. To a stirred suspension of NaH
(4.08 mg, 0.17 mmol) in THF under Ar was added a solution of 23
(0.14 mmol, 44.4 mg) in THF at 0 ꢁC. After the mixture was stirred at
room temperature for 24 h, the mixture was poured into ice-water
saturated with NH4Cl. The solution was extracted with diethyl
ether, and the extract was washed with water and dried over
MgSO4. Filtration and solvent evaporation are followed by silica gel
column chromatography eluting with ethyl acetate and hexanes to
give product 24 (54.0 mg) in 87% yield. 1H NMR (400 MHz, CDCl3,
TMS):
d 0.01 (s, 3H), 0.03 (s, 3H), 0.85 (s, 9H), 2.23 (s, 1H), 2.47 (s,
4.2.4.1. Compound 19. 1H NMR (400 MHz, CDCl3, TMS):
d
2.46 (s,
3H), 3.08 (ABX, 1H), 3.42 (dd, J¼6.4, 2 Hz, 1H), 3.73 (dd, J¼11.2, 6 Hz,
3H), 4.24 (dd, J¼8.8, 3.6 Hz, 1H), 4.52 (dd, J¼8.4, 8 Hz, 1H), 5.06 (m,
1H), 3.80 (dd, J¼11.2, 8 Hz, 1H), 7.37 (d, J¼7.6 Hz, 2H), 7.86 (d,
1H), 5.59(m, 1H), 6.37 (dd, J¼5.4, 5 Hz, 1H), 7.37 (d, J¼8 Hz, 2H), 7.94
J¼7.6 Hz, 2H). 13C NMR (100 MHz, CDCl3):
d
ꢀ5.3, ꢀ5.2, 18.4, 21.9,
2986,
2376, 1332, 1162, 1090, 833, 670 cmꢀ1
. HRMS (ESI) for
(dd, J¼7.2, 1.6 Hz, 2H). 13C NMR (100 MHz, CDCl3):
d
22.0, 55.2, 67.7,
2358, 1781,
26.0, 31.8, 45.0, 61.4, 73.0, 76.4, 128.3, 130.1, 134.6, 145.1. IR: n
76.5, 97.8, 128.8, 130.1, 134.9, 146.2, 151.5, 203.1. IR:
n
1709, 1368, 1168, 1088, 993 cmꢀ1. HRMS (ESI) for C13H12BrO4SþNa
(Mþ23), 379.9563 (calcd), found 379.9553.
C18H27NO3SSiþNa (Mþ23), 388.1373 (calcd), found 388.1376.
Acknowledgements
4.2.4.2. Compound 20. 1H NMR (400 MHz, CDCl3, TMS):
d 2.42
(s, 3H), 4.48 (t, J¼8 Hz, 1H), 4.81 (t, J¼8 Hz, 1H), 5.47 (m, 1H), 5.57 (t,
We thank the University of Wisconsin and the American
Chemical Society Petroleum Research Foundation (48092-G) for
funding, and the School of Pharmacy Analytical Instrument Center
(AIC) for mass spectrometry services and NMR support.
J¼6.4 Hz, 1H), 6.33 (d, J¼6.4 Hz, 1H), 7.29 (d, J¼8 Hz, 2H), 7.86 (d,
J¼8 Hz, 2H). 13C NMR (100 MHz, CDCl3):
d 21.9, 29.6, 77.6, 95.2,
127.2, 129.4, 138.6, 143.8, 159.4, 178.7, 203.2. IR:
n 2922, 1771, 1689,
1293, 1187, 819 cmꢀ1. HRMS (ESI) for C13H12BrNO4SþNa (Mþ23),
379.9563 (calcd), found 379.9558.
Supplementary data
4.2.5. Synthesis of 4,5-dihydrooxazole 22. To a solution of tri-
chloroacetimidate 13 (0.1 mmol) in acetonitrile directly purchased
from Fisher was added NBS (23 mg, 0.12 mmol). The reaction
mixture was stirred for 24 h. The reaction mixture was concen-
trated under vacuum and directly purified by flash column chro-
matography eluting with ethyl acetate and hexanes to give product
22 (16.9 mg) in 52% yield. Diastereomer one: 1H NMR (400 MHz,
Supplementary data related to this article can be found online at
References and notes
1. (a) Harding, K. E.; Tiner, T. H. In Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Eds.; Pergamon: Oxford, 1991; Vol. 4, p 363; (b) Rodriguez, J.;
Dulcere, J. P. Synthesis 1993, 1177.
€
CDCl3, TMS):
d 4.55 (m, 1H), 4.77 (m, 1H), 5.05 (m, 1H), 5.58 (t,
2. Hoffmann-Roder, A.; Krause, N. Angew. Chem., Int. Ed. 2004, 43, 1196.
J¼6 Hz, 1 H), 6.21 (m, 1H). 13C NMR (100 MHz, CDCl3):
d 64.9, 75.3,
n 2927, 2362, 2252, 1657, 907,
3. (a) For recent reviews on allenes, see Krause, N.; Hashmi, A. S. K. Modern Allene
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Bissmire, S.; Wirth, T. Chem. Soc. Rev. 2004, 33, 354.
75.7, 99.4, 100.3, 168.3, 202.7. IR:
731 cmꢀ1. HRMS (ESI) for C7H5BrCl3NOþNa (Mþ23), 325.8518
(calcd), found 325.8529. Diastereomer two: 1H NMR (400 MHz,
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Kosaka, S.; Tanaka, T. J. Am. Chem. Soc. 2004, 126, 8744; (e) Hamaguchi, H.;
Kosaka, S.; Ohno, H.; Tanaka, T. Angew. Chem., Int. Ed. 2005, 44, 1513; (f) Xu, B.;
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CDCl3, TMS):
J¼6 Hz, 1H), 6.21 (m, 1H).
d 4.55 (m, 1H), 4.77 (m, 1H), 5.05 (m, 1H), 5.67 (t,
4.2.6. Preparation of bromoallene 23 via deprotection and silyla-
tion. The solution of 16 (267 mg, 0.75 mmol) and LiOH (38.4 mg,
1.6 mmol) in 3.5 mL H2O and 10 mL THF was stirred at room
temperature overnight. The mixture was extracted with diethyl
ester and the combined organic layers were dried over MgSO4,
concentrated under vacuum, and purified by flash column chro-
matography eluting with ethyl acetate and hexanes to yield a free
alcohol.
A solution of above alcohol (66 mg, 0.2 mmol), imidazole
(68 mg, 1.0 mmol), and TBSCl (150.7 mg, 1.0 mmol) in DMF was
stirred for 13 h at room temperature. The reaction was quenched
by addition of saturated aqueous NH4Cl. The resulting mixture
was extracted with diethyl ether. The organic layer was dried with
Na2SO4 and concentrated under vacuum. The residue was purified
by flash column chromatography eluting with ethyl acetate and
hexanes to give product 23 (73.9 mg) in 83% yield. 1H NMR
(400 MHz, CDCl3, TMS):
d 0.02 (s, 6H), 0.86 (s, 9H), 2.42 (s, 3H),
3.60 (dd, J¼6.4, 4.8 Hz, 1H), 3.97 (m, 1H), 4.95 (d, J¼6.8 Hz, 1H),
5.31 (dd, J¼6.8, 4.8 Hz, 1H), 5.86 (d, J¼6.8 Hz, 1H), 7.30 (d, J¼6.8 Hz,
2H), 7.76 (d, J¼6.8 Hz, 2H). 13C NMR (100 MHz, CDCl3):
d
ꢀ5.34,
13. Werness, J. B.; Tang, W. Sci. China Chem. 2011, 54, 56.
14. (a) Zhang, W.; Werness, J. B.; Tang, W. Org. Lett. 2008, 10, 2023; (b) Zhang, W.;
Werness, J. B.; Tang, W. Tetrahedron 2009, 65, 3090.
ꢀ5.29, ꢀ3.4, 18.4, 21.7, 25.9, 53.4, 65.3, 75.3, 99.8, 127.5, 129.9,
130.0, 143.8, 201.7. IR:
n 2996, 2360, 1705, 1328, 1158, 1090,