J. Liu, C.-H. Wong / Tetrahedron Letters 43 (2002) 4037–4039
4039
We propose that the F group in Selectfluor™ plays a
Lewis acid role in these deprotection reactions although
other possibilities could not be ruled out.11
127.95, 127.06, 65.72, 49.57; ESI m/e Calcd for (M+)
C9H12O2: 152; Found: 175 (M+Na), 151 (M−H), 187
(M+Cl).
6. Greene, T. W.; Wuts, P. G. W. Protective Groups in
Organic Synthesis, 3rd ed.; John Wiley: New York, 1999;
pp. 49–54.
7. (a) Greene, T. W.; Wuts, P. G. W. Protective Groups in
Organic Synthesis, 3rd ed.; John Wiley: New York, 1999;
pp. 329–344; (b) Platen, M.; Steckhan, E. Tetrahedron
Lett. 1980, 21, 511–514; (c) Stork, G.; Zhao, K. Tetra-
hedron Lett. 1989, 30, 287–290.
In summary, we have developed a new and efficient
method to remove the PMP, THP and 1,3-dithiane
protecting groups using Selectfluor™ in high yields and
under very mild conditions. Because Selectfluor™ is
very soluble in water (176 g/l at 20°C), a simple
aqueous workup is enough to remove most byproducts.
In addition, it is nontoxic and relatively inexpensive
compared to other electrophilic fluorinating reagents.
Further utility of this method is being investigated in
our laboratory.
8. Valle´e, Y.; Bulpin, A. In Comprehensive Organic Func-
tional Group Transformations; Katritzky, A. R.; Meth-
Cohn, O.; Rees, C. W., Eds. Functions incorporating two
chalcogens other than oxygen, 1st ed.; Cambridge Uni-
versity Press: Oxford, 1995; Vol. 4, pp. 243–283.
9. General procedure for the deprotection of dithianes: sub-
strate 5 (Table 2) (54 mg, 0.17 mmol) was dissolved in
CH3CN (5 ml, 5% H2O). To the mixture was added
Selectfluor™ (150 mg, 0.42 mmol) at room temperature.
The reaction went to completion in 5 min and was
quenched by adding aqueous NaHCO3 (sat. 5 ml). The
mixture was extracted by CH2Cl2 (10 ml) twice. The
combined organic layer was washed with H2O (10 ml),
dried (Na2SO4) and concentrated in vacuo. The residue
was purified by flash chromatography (silica, 8:1 hex-
anes:EtOAc) to afford the product as a colorless oil (31
mg, 80%). 1H NMR (500 MHz, CDCl3) l 9.71 (br. s,
1H), 4.45 (t, J=5.5 Hz, 1H), 2.75 (dt, J=1.8, 5.2 Hz,
2H), 2.25 (s, 3H), 0.89 (s, 9H), 0.10 (s, 3H), 0.07 (s, 3H);
13C NMR (CDCl3, 125 MHz): 210.59, 198.85, 73.97,
48.03, 25.99, 25.59, 18.31, −4.92, −5.02; HRMS m/e
Calcd for (M+) C11H22O3Si: 230.1338; Found: 253.1223
(M+Na).
References
1. Banks, R. E.; Besheesh, M. K.; Mohialdin, S. N.; Sharif,
I. J. Chem. Soc., Perkin Trans. 1 1996, 2069–2076.
2. (a) Burkart, M. D.; Zhang, Z.; Hung, S.-C.; Wong, C.-H.
J. Am. Chem. Soc. 1997, 119, 11743–11746; (b) Vincent,
S. P.; Burkart, M. D.; Tsai, C.-Y.; Zhang, Z.; Wong,
C.-H. J. Org. Chem. 1999, 64, 5264–5279.
3. (a) Shibata, N.; Suzuki, E.; Asahi, T.; Shiro, M. J. Am.
Chem. Soc. 2001, 123, 7001–7009; (b) Takeuchi, Y.;
Tarui, T.; Shibata, N. Org. Lett. 2000, 2, 639–642.
4. Greene, T. W.; Wuts, P. G. W. Protective Groups in
Organic Synthesis, 3rd ed.; John Wiley: New York, 1999;
pp. 224–227.
5. General procedure for the deprotection of PMP and THP
groups: substrate 5 (Table 1) (120 mg, 0.38 mmol) was
dissolved in CH3CN (10 ml, 5% H2O). To the mixture
was added Selectfluor™ (320 mg, 0.90 mmol) at room
temperature. The mixture was stirred for 5 h. After the
reaction went to completion, the solvent was remove in
vacuo and the residue was purified by flash chromatogra-
phy (silica, 1:1 hexanes:EtOAc) to afford the product as a
10. Deprotection of conjugated, cinnamaldehyde type 1,3-
dithianes with Selectfluor™ usually gave a low yield.
11. We found that the pH of the aqueous solution of Select-
fluor™ (ꢀ50 mg/ml) is about 3, which may implicate the
1
formation of ꢀN -H from the reaction between Select-
colorless oil (53 mg, 94%). H NMR (600 MHz, CDCl3)
fluor™ and H2O. Whether other reactive species, e.g.
HOF, are formed and also participate in the cleavage
reaction is currently being investigated in our laboratory.
l 7.33 (m, 2H), 7.27 (m, 1H), 7.23 (m, 2H), 3.93 (dd,
J=7.9, 11.0 Hz, 2H), 3.87 (dd, J=5.3, 11.0 Hz, 2H), 3.02
(m, 3H); 13C NMR (CDCl3, 150 MHz): 139.34, 128.66,