406
M. Rupprich et al.
indicates the presence of a chlorine atom in the molecule.
Thus, these findings (1H-NMR and GC/MS) clearly indi-
cate that fluorine substitution did not occur, and, as
expected, the well-known chlorine compound was formed.
In addition to the above mentioned experiments, we
performed the reaction (CCl4/DMF; Ph3P; KF) under
microwave irradiation, since it is known that microwave
heating results in reduced reaction times and side reactions,
increased yields and improved reproducibility [5]. There-
fore, we tested whether microwave-induced activation has
a positive effect on the system. However, we were able to
characterize all of the isolated products from the micro-
wave-accelerated experiments as the corresponding
chlorine derivatives (Scheme 2).
chromatography (ethyl acetate/n-hexane; 1:9) to obtain the
chlorine compound with a yield of 72%; 1H-NMR
(200 MHz, CDCl3): d = 7.13 (d, 2H, J = 8.6 Hz), 6.87 (d,
2H, J = 8.6 Hz), 4.54 (s, 2H); GC/MS (EI, 70 eV): m/
z = 144 (M?, 2.5%), 142 (M?, 7.8%), 107 ([M-Cl]?,
100%), 91 (20.5%).
Experiment 2: Reaction of 4-hydroxybenzylalcohol
in CCl4/DMF (1:4) in the presence of Ph3P and KF
under microwave irradiation
Sixty milligrams of 4-hydroxybenzylalcohol (0.5 mmol)
and 320 mg triphenylphosphine (1.2 mmol) were dissolved
in mixture of 2 cm3 of CCl4/DMF (1:4) followed by the
addition of 59 mg KF (1.0 mmol). The resulting mixture
was heated in a microwave synthesizer (CEM Discover,
Matthews, NC, USA) with an irradiation power of 50 W
for 5 min at 50 °C. After the reaction (TLC), the mixture
was extracted with n-hexane (2 9 5 cm3) and the com-
bined organic phases were dried over sodium sulfate. The
solvent was removed in vacuo and the remaining residue
was purified by column chromatography (ethyl acetate/n-
hexane; 1:9) to obtain the chlorine compound with a yield
of 81%.
Ph3P, KF, 25 °C
R
R
OH
Cl
CCl4-DMF (1:4)
Scheme 2
In conclusion, we were not able to reproduce the results
described by Bandgar et al. We were only able to isolate
the corresponding chlorine compounds. We fully agree
with the authors that a one-step conversion of alcohols to
the fluorine derivatives under mild conditions is a desirable
ambition. However, the protocol given by Bandgar et al.
does not allow this goal to be achieved.
1H-NMR and mass spectra were found to be identical to
those described in ‘‘Experiment 1.’’
Experiment 3: Reaction of 4-methoxybenzylalcohol
in CCl4/DMF (1:4) in the presence of Ph3P and KF
Experimental
Six hundred and ninety milligrams of 4-methoxybenzylal-
cohol (5.0 mmol) and 3.28 g triphenylphosphine
(12.5 mmol) were dissolved in a mixture of 5 cm3 of CCl4/
DMF (1:4), followed by the addition of 580 mg KF
(10.0 mmol). The resulting mixture was stirred at room
temperature for 1.5 h. The mixture was extracted with n-
hexane (2 9 5 cm3) and the combined organic phases were
dried over sodium sulfate. The solvent was removed in
vacuo, and the remaining residue was purified by column
chromatography (ethyl acetate/n-hexane; 1:9) to afford the
chlorine compound in 79% yield; 1H-NMR (200 MHz,
CDCl3): d = 7.32 (d, 2H, J = 8.4 Hz), 6.92 (d, 2H,
J = 8.4 Hz), 4.55 (s, 2H), 3.78 (s, 3H); GC/MS (EI,
70 eV): m/z = 158 (M?, 4.2%), 156 (M?, 13.2%), 121
([M–Cl]?, 100%), 91 (9.8%), 78 (20.3%), 77 (21.8%).
All reagents and solvents were of analytical grade and were
1
used without further purification. H-NMR spectra were
recorded on a Varian (Palo Alto, CA, USA) Gemini 200
spectrometer (199.98 MHz for 1H) with the deuterium
signal of the solvent used as the lock and TMS as internal
standard. GC/MS measurements were performed on a HP
(Palo Alto, CA, USA) 5890 II gas chromatograph, followed
by characterization in a HP 5971 A quadrupole mass
spectrometer (EI, 70 eV).
Experiment 1: Reaction of 4-hydroxybenzylalcohol
in CCl4/DMF (1:4) in the presence of Ph3P and KF
Three hundred and ten milligrams of 4-hydroxybenzylal-
cohol (2.5 mmol) and 1.64 g triphenylphosphine
(6.25 mmol) were dissolved in a mixture of 3 cm3 of CCl4/
DMF (1:4), followed by the addition of 290 mg KF
(5 mmol). The resulting mixture was stirred at room tem-
perature for 0.5 h. The mixture was extracted with n-
hexane (2 9 5 cm3) and the combined organic phases were
dried over sodium sulfate. The solvent was removed in
vacuo and the remaining residue was purified by column
Experiment 4: Reaction of 4-methoxybenzylalcohol
in CCl4/DMF (1:4) in the presence of Ph3P and KF
under microwave irradiation
Fifty-two
milligrams
of
4-methoxybenzylalcohol
(0.37 mmol) and 235 mg triphenylphosphine (0.90 mmol)
were dissolved in mixture of 2 cm3 of CCl4/DMF (1:4)
123