S. Das et al. / Tetrahedron Letters 48 (2007) 5305–5307
5307
ꢀ
40 ꢁC to +50 ꢁC. The more volatile fluorinated
9. Seddon, K. R.; Stark, A.; Torres, M. Pure Appl. Chem.
000, 12, 2275–2288.
0. Typical experimental procedure for dehydroxy-fluorination:
The ionic liquid [C mim][PF ] (2 ml) in a two-necked
2
products were isolated directly by distillation, in pure
form. For the less volatile derivatives, extraction with
a non polar solvent, followed by short silica gel filtra-
tion, was found to be efficient. The yields for fluorina-
tion in RTILs were usually found to be higher than
those obtained in classical organic solvents such as
1
8
6
round-bottomed flask equipped with a magnetic stirrer,
was heated at 50 ꢁC after which it was connected to a high
vacuum pump for 6 h to pump off any moisture present.
Then after cooling to room temperature (20 ꢁC) under N ,
2
the alcohol (2 mmol) was added slowly to the stirred
solution. After 15 min DAST (2.1 mmol) was added
dropwise at room temperature. The reaction mixture was
1
4
CH Cl .
2
2
Acknowledgements
2
allowed to stir for 30 min under an N atmosphere.
Purification by distillation: The volatile dehydroxy-fluori-
nated products were distilled into a trap maintained at
about ꢀ78 ꢁC under vacuum. Purification by extraction:
The reaction mixture was extracted using pentane or ether
We thank IFCPAR/CEFIPRA (Project No. 7106) for
the support of this research and Mrs. D. Gr e´ e for her
help in the NMR studies.
(
5 · 3 ml), and then the combined organic phases were
washed (3 · 5 ml) with a saturated solution of NaHCO ,
filtered through a small pad (1 g) of silica gel and
concentrated.
3
References and notes
1
1. Data for compounds in Table 1: 2a–b and 2d–f have
1
2
. Ionic Liquids in Synthesis; Wasserscheid, P., Welton, T.,
Eds.; Wiley-VCH: Germany, 2003.
. Recent reviews on ionic liquids: (a) Jain, N.; Kumar, A.;
Chauhan, S.; Chauhan, S. M. S. Tetrahedron 2005, 61,
spectral data in agreement with the literature. Compound
1
(2c) pale yellow oil, 75% H NMR (300 MHz, CDCl
3
): d
5.91 (m, 1H), 5.28 (dm, 2H, J = 10.6 Hz), 4.89 (dq, 1H,
J
H–F = 48.5, 6.3 Hz), 1.80–1.25 (m, 8H), 0.90 (t, 3H,
1
3
1
015–1060; (b) L e´ v eˆ que, J.-M.; Luche, J.-L.; P e´ trier, C.;
J = 6.5 Hz). C NMR (75 MHz, CDCl
C–F = 19.4 Hz), 116.7 (d, 1C, JC–F = 12.0 Hz), 93.8 (d,
1C, JC–F = 166.4 Hz), 35.2 (d, 1C, JC–F = 22.0 Hz), 31.5,
3
): d 136.8 (d, 1C,
Roux, R.; Bonrath, W. Green Chem. 2002, 4, 357–360; (c)
Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev.
J
1
9
2
2
002, 102, 3667–3692; (d) Sheldon, R. Chem. Commun.
001, 23, 2399–2407; (e) Earle, M. J.; Seddon, K. R. Pure
24.3 (d, 1C, JC–F = 4.7 Hz), 22.5, 13.9.
F NMR
(282.3 MHz, CDCl
3
): d ꢀ176.6 (m, 1F). MS data: m/z
+
Å
Appl. Chem. 2000, 72, 1391–1398; (f) Wasserscheid, P.;
Keim, W. Angew. Chem., Int. Ed. 2000, 39, 3772–3789; (g)
Welton, T. Chem. Rev. 1999, 99, 2071–2084.
(EI) 130.1163 (M
12. Typical Experimental procedure for gem-difluorination: The
ionic liquid [C mim][PF ] (1 ml) in a two-necked round-
8
C H15F requires 130.1157).
8
6
3
. (a) Kitazume, T.; Yamazaki, T. Experimental Methods in
Organic Fluorine Chemistry; Gordon and Breach Science:
Tokyo, 1998; (b) Hudlicky, M.; Pavlath, A. E. Chemistry
of Organic Fluorine Compounds II: A Critical Review. ACS
Monograph 187: Washington, DC, 1995; (c) Banks, R. E.;
Smart, B. E.; Tatlow, J. C. Characteristics of C–F systems.
In Organofluorine Chemistry: Principles and Commercial
Applications; Plenum: New York, 1994; Vol. 57, and
references cited therein.
bottomed flask was stirred at 50 ꢁC then connected to a
high vacuum pump for 6 h to pump off any moisture
present. It was cooled to room temperature (20 ꢁC) under
2
N and the ketone (0.8 mmol) added slowly to the stirred
solution. After 15 min, DAST (1.6 mmol) was added
dropwise at room temperature, then slowly the tempera-
ture was raised to 50 ꢁC. The reaction mixture was allowed
2
to stir for 4 h under N . The reaction mixture was
extracted using pentane (5 · 3 ml), and then the combined
organic phase was washed (3 · 5 ml) with a saturated
solution of NaHCO , filtered through a small pad (1 g) of
3
4
. (a) Ojima, I.; McCarthy, J. R.; Welch, J. T. Biomedical
Frontiers in Fluorine Chemistry, ACS Symposium Series
6
39: Washington, DC, 1996; (b) Welch, J. T.; Eswara-
silica gel and concentrated.
krishnan, S. Fluorine in Bioorganic Chemistry; Wiley
Interscience: New York, 1991; (c) Welch, J. T. Tetrahedron
13. Data for gem-difluorinated compounds: Compound 6 has
spectral data in agreement with literature. 3,3-difluorooct-
1
1
987, 43, 3123–3197, and references cited therein.
1-yne (4) pale yellow oil 93% H NMR (300 MHz,
5
. (a) Kim, S. M.; Kang, Y. K.; Lee, K. S.; Mang, J. Y.; Kim,
D. Y. Bull. Korean Chem. Soc. 2006, 27, 423–425; (b)
Baudequin, C.; Loubassou, J.-F.; Plaquevent, J.-C.;
Cahard, D. J. Fluorine Chem. 2003, 122, 189–193; (c)
Laali, K. K.; Borodkin, G. I. J. Chem. Soc., Perkin Trans.
CDCl
(m, 2H), 1.35 (m, 4H), 0.93 (t, 3H, J = 6.5 Hz). C NMR
(75 MHz, CDCl ): d 114.4 (t, 1C, JC–F = 232.8 Hz), 77.0
(t, 1C, JC–F = 32.0 Hz), 74.9 (t, 1C, JC–F = 6.8 Hz), 38.9 (t,
3
): d 2.77 (t, 1H, J = 4.9 Hz), 2.07 (m, 2H), 1.51
13
3
1C, JC–F = 25.2 Hz), 31.0, 22.4, 22.3 (t, 1C, JC–F
=
1
9
2
2002, 5, 953–957.
3.5 Hz), 13.8. F NMR (282.3 MHz, CDCl
(tt, 1F, J = 15.0, 4.9 Hz). MS data: m/z (EI) 145.0837
+
3
): d ꢀ84.04
6
. Anguille, S.; Garayt, M.; Schanen, V.; Gr e´ e, R. Adv. Synth.
Cat. 2006, 348, 1149–1153, and references cited therein.
. (a) Singh, R. P.; Shreeve, J. M. Synthesis 2002, 17, 2561–
Å
([M–H]
8 11 2
C H F requires 145.0828).
7
14. It is clear that extension of this chemistry, involving higher
reaction temperatures, first requires a detailed understand-
ing of the thermal and chemical stability of the sensitive
2
578; (b) Hudlicky, M. Org. React. 1988, 35, 513, and
references cited therein; (c) Middleton, W. J. J. Org.
Chem. 1975, 40, 574–578.
TM
DAST and Deoxo-fluor reagents in RTILs. Correspond-
8
. Prakesch, M.; Gr e´ e, D.; Gr e´ e, R. Acc. Chem. Res. 2002,
ing experiments are under investigation in our group and
will be reported in due course.
3
5, 175–181.