Preparation of fluorohalomethylmagnesium halides using highly active magnesium metal and their reactions

Article abstract of DOI:10.1016/j.jfluchem.2005.07.016

Highly active magnesium (Rieke magnesium) reacts with fluorohalomethanes at -100°C forming the corresponding fluorohalomethylmagnesium halides, which undergo nucleophilic substitution with silyl halides or nucleophilic addition with aldehydes or ketones. Whereas the stability of dibromofluoromethylmagnesium bromide (2a) was sufficient to provide acceptable product yields with dimethylphenylsilyl chloride, benzaldehyde, butyraldehyde or acetophenone as electrophiles, other fluoroorganomagnesium halides, bromodifluoromethylmagnesium bromide (2b), bromochlorofluoromethylmagnesium bromide (2c) and trifluoromethylmagnesium iodide (2d) displayed only very limited stability and thus the corresponding yields of reactions with electrophiles were low.

Full text of DOI:10.1016/j.jfluchem.2005.07.016

Journal of Fluorine Chemistry 126 (2005) 1390–1395
www.elsevier.com/locate/fluor
Preparation of fluorohalomethylmagnesium halides using highly
active magnesium metal and their reactions§
ˇ
Jaroslav Kvıcala , Jan Stambasky, Martin Skalicky, Oldrich Paleta
*
´ˇ
´
´
ˇ
Department of Organic Chemistry, Institute of Chemical Technology in Prague,
166 28 Prague 6, Czech Republic
Received 4 February 2005; received in revised form 25 July 2005; accepted 27 July 2005
Available online 12 September 2005
Abstract
Highly active magnesium (Rieke magnesium) reacts with fluorohalomethanes at À100 8C forming the corresponding fluorohalomethyl-
magnesium halides, which undergo nucleophilic substitution with silyl halides or nucleophilic addition with aldehydes or ketones. Whereas
the stability of dibromofluoromethylmagnesium bromide (2a) was sufficient to provide acceptable product yields with dimethylphenylsilyl
chloride, benzaldehyde, butyraldehyde or acetophenone as electrophiles, other fluoroorganomagnesium halides, bromodifluoromethylmag-
nesium bromide (2b), bromochlorofluoromethylmagnesium bromide (2c) and trifluoromethylmagnesium iodide (2d) displayed only very
limited stability and thus the corresponding yields of reactions with electrophiles were low.
# 2005 Elsevier B.V. All rights reserved.
Keywords: Activated magnesium; Rieke magnesium; Fluorohalomethane; Fluoro Grignard reagent; Fluoromethylmagnesium halide; Fluorohalomethyl-
magnesium halide; Nucleophilic substitution; Nucleophilic addition; Fluorohalomethylsilane; Fluorohaloalcohol
1. Introduction
co-worker, for the preparation of difluoromethylated
compounds [5].
In contrast to perfluoroalkylorganometallic compounds,
which are appreciably stable up to À40 8C for perfluoroalk-
yllithium [1], up to 0 8C for perfluoroalkylmagnesium [2,3]
and above room temperature for perfluoroalkylzinc [4] and
perfluoroalkylcopper [1] compounds, the stability of other
fluoroalkylmagnesium compounds is surprisingly low and
thus information about successful applications of fluor-
omethyl- and fluorohalomethylorganometallic compounds
is severely limited. Trifluoromethylzinc and trifluoromethyl-
copper reagents can be prepared from various precursors
such as bromotrifluoromethane, dibromodifluoromethane
and others, preferably under Barbier conditions [1]. Except
for trifluoromethyl reagents, only difluoromethylcadmium
compounds have been successfully applied, by Burton and
Early attempts to prepare fluoro- or fluorohalomethyl
organometallic compounds using more electropositive
metals, such as lithium or magnesium were unsuccessful
due to immediate decomposition of the fluoroorganometallics
formed to the corresponding carbenes and metal halides [6]
and hence the name ‘‘carbenoids’’ was introduced for this
class of compounds [7,8]. A major breakthrough was
achieved by Kuroboshi et al., who successfully generated
dibromofluoromethyllithium under Barbier conditions from
tribromofluoromethane and butyllithium at À130 8C and
reacted it with a series of electrophiles [9].
Our aim in fluorocarbenoids started in 1995 by preparation
of fluorene derived fluoroethenyllithium and first direct
observation of low-temperature 13C and 19F NMR spectra
[10–12] of a fluorocarbenoid and continued with experi-
mental and theoretical study of fluoroalkenyllithiums [13,14].
In contrast to both experimental and theoretical interest in
fluoroorganolithium compounds in the course of the last
decade, no such studies have been devoted to fluoroorga-
§
Part 6 in the series ‘‘Fluorinated carbanions’’ [20].
* Corresponding author. Tel.: +420 2 20 444 242; fax: +420 2 20 444 288.
´ˇ
E-mail address: kvicalaj@vscht.cz (J. Kvıcala).
0022-1139/$ – see front matter # 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.07.016

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1391
nomagnesium compounds. We hence decided to start a study
of both experimental and theoretical aspects of this area of
chemistry. In this paper, we present our experimental results
concerning preparation and reactions of fluorohalomethyl-
magnesium halides.
2. Results and discussion
Scheme 1.
Preparation of fluoroorganolithium compounds by direct
lithiation isnotfeasible[7,8] and therefore transmetallationof
the fluoroalkyl halide with an appropriate organolithium
reagent has to be employed [1,9]. Transmetallation of
perfluoroalkyl iodides with an organomagnesium reagent at
À40 8C is also the preferable method for the generation of
perfluoroalkylmagnesium compounds [2,3]. We were there-
fore surprised when we failed to synthesize any fluorohalo-
methylmagnesium halides using this method regardless of the
nature of the substrate, solvent and temperature employed.
Standard conditions for the preparation of organomag-
nesium compounds are rather harsh (room temperature)
and fluoroorganomagnesium compounds cannot survive.
Attempts to prepare trifluoromethylmagnesium iodide under
Barbier conditions at À78 8C more than 50 years ago
afforded only very low yields of the addition product with
acetone [15]. Clearly, activation of the magnesium metal is
critical to the preparation.
the reaction with chlorobenzene at 20 8C and bromobenzene
at À78 8C.
As the first substrate, we chose tribromofluoromethane
(1a) expecting the best stability of the corresponding
fluoroorganometallic compound by analogy with the
corresponding fluoroorganolithium compound. Experiments
with temperature variation established À100 8C to be the
temperature of choice; at À70 8C partial decomposition
occurred, whereas at À130 8C no reaction was observed.
Finally, we studied the reaction arrangement. Under Barbier
conditions, i.e. addition of the Rieke metal to the mixture of
fluorohalomethane 1a and electrophilic substrate, benzal-
dehyde (3, general procedure A, see Section 4), we found
that the expected product, fluorohaloalcohol 4a (18% yield),
was accompanied by an unexpected side-product, 2,4,5-
triphenyl-1,3-dioxolane (5, see Scheme 1). This side-
product is probably formed by pinacol reaction of
benzaldehyde (3) induced by magnesium and subsequent
cyclization of 1,2-diphenylethan-1,2-diol with aldehyde 3.
We therefore first prepared the corresponding fluoroor-
ganomagnesium bromide 2a and added the electrophile 3
after 5 min (general procedure B). In this case, we obtained
fluoroalcohol 4a in a yield of 17% with no side-product 5.
Attempts to improve the results by extending the reaction
time to 30 min (general procedure C) did not change the
yield. Hence, general procedure B (separate formation of
fluoroorganomagnesium compound 2 for 5 min, reaction
temperature À100 8C) was employed for all experiments
with compound 2a throughout this work.
Rieke and co-workers published a series of methods
resulting in the formation of highly active magnesium metal,
which allowed the preparation of organomagnesium com-
pounds at temperatures as low as À80 8C [16–19]. One using
potassium and magnesium bromide worked best in our
hands. We modified the original procedure and formed
magnesium bromide in situ by the reaction of magnesium
with 1,2-dibromoethane in diethyl ether. Removal of diethyl
ether under vacuum, addition of anhydrous ethereal solvent
(THF for À70 8C, diethyl ether for À100 8C, 2-methylte-
trahydrofuran (MTHF) for À130 8C) and potassium metal
allowed the preparation of highly active magnesium without
the use of a dry box. The activity of Rieke magnesium was
confirmed according to the original procedures [16–19] by
Scheme 2.

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J. Kvıcala et al. / Journal of Fluorine Chemistry 126 (2005) 1390–1395
1392
Scheme 3.
Scheme 4.
Reaction of compound 2a with other oxo compounds,
We expected that fluoro Grignard reagent 2c formed from
dibromochlorofluoromethane (1c) would display stability
close to that of fluoromethylmagnesium bromide 2a.
Surprisingly, despite numerous variations in reaction
conditions, the yield with benzaldehyde (3) did not exceed
6% (mixture of two diastereoisomers in about 1:1 ratio).
Similarly disappointing were the results of reactions of
trifluoromethylmagnesium iodide (2d) formed from tri-
fluoromethyl iodide (1d) and activated magnesium. For
example, its addition to aldehyde 3 afforded the product in
only 4% yield, estimated by NMR from the complex
reaction mixture (Scheme 4).
butyraldehyde (6), acetophenone (7), and benzoyl chloride,
afforded the corresponding products 8 and 9 in acceptable
yields with the exception of the latter reagent where no
product could be isolated. Reaction of compound 2a with
dimethylphenylsilyl chloride (10) as a representative
halosilane afforded the corresponding fluorohalomethylsi-
lane 11a in good yield. However, the analogous reaction
with tributyltin chloride failed even if the reaction
temperature was raised (Scheme 2). In both failed
experiments, no fluorinated signals were observed in 19F
NMR spectra of crude reactions mixtures. Probably weaker
electrophiles employed in these reactions are not reactive
enough at low temperatures and the decomposition of the
fluorocarbenoid took place predominantly. According to 1H
NMR spectra, complex mixtures were formed in which the
starting electrophiles prevailed.
3. Conclusions
We have shown that highly activated magnesium can be
employed for the preparation of fluorohalomethylmagne-
sium halides 2a–2d and subsequent transfer of the
fluorohalomethyl moiety to appropriate electrophiles.
Similar to the corresponding fluorohalomethyllithium
compounds, dibromofluoromethylmagnesium (2a) dis-
played the highest stability among the fluoro Grignard
reagents studied. The low stability of other fluoro Grignard
reagents 2b–2d precludes their synthetic applications.
Both experiments [9] and calculations [20] confirmed
that dibromofluoromethyllithium is significantly more stable
that bromodifluoromethyllithium. A similar pattern can be
observed in the stabilities of the corresponding fluoro
Grignard reagents. Thus, reaction of bromodifluoromethyl-
magnesium bromide (2b), prepared from dibromodifluor-
omethane (1b) and activated magnesium, with benzaldehyde
(3) afforded only negligible (0.2%) yield of the correspond-
ing fluoroalcohol 4b. However, trapping the reagent 2b with
silyl chloride 10 afforded a 12% yield of the corresponding
fluoromethylsilane 11b. In these cases, general procedure A
(i.e. reactions under Barbier conditions) lead to better results
than general procedure B. To our knowledge, this is the first,
at least partially successful, experiment published transfer-
ring the bromodifluoromethyl moiety using an organome-
tallic reagent (Scheme 3). Again, no fluorinated by-products
were found in the reaction mixtures and large amounts of
electrophiles were recovered.
4. Experimental
4.1. General experimental details
Temperature data were uncorrected. NMR spectra were
1
recorded with a Varian MercuryPlus instrument, H NMR
spectra at 300.0 MHz and 13C NMR spectra at 75.4 MHz
using residual solvent peaks as the respective internal

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J. Kvıcala et al. / Journal of Fluorine Chemistry 126 (2005) 1390–1395
1393
standards, 19F NMR spectra at 282.2 MHz using CFCl3 as the
internal standard with lower frequency values designed
negative. GC–MS spectra were measured with a Hewlett-
Packard 5890 II instrument. FT-IR spectra were recorded with
a Nicolet 740 instrument. Elemental analyses were performed
with automatic elemental analyser, Perkin-Elmer 2400.
Fluorohalomethanes (1a–1d), 1,2-dibromoethane, mag-
nesium and potassium were purchased from Aldrich, as well
as the electrophilic reagents used. Dimethylphenylsilyl
chloride (10) was prepared from phenylmagnesium bromide
and dichlorodimethylsilane [21].
solvent was carefully added dropwise (5 min) on the wall of
the reaction flask. After another 5 min, a solution of
electrophile in 1 ml (mmol Mg*)À1 of ethereal solvent used
was similarly added. The mixture was stirred for 30 min
while still cooled and stirred, quenched with Br2 and
worked-up as above.
4.3.3. General procedure C
This procedure was nearly identical with general
procedure B; in this case, the solution of electrophile was
added after 30 min to allow complete formation of the
organometallic species 2.
Apparatus were heated by a hot gun and allowed to cool
under a positive pressure of argon prior to use. Reactions
were performed under a positive argon pressure and
anhydrous conditions using standard septum techniques
and an inert line.
4.3.4. Aqueous work-up
The crude reaction mixture (in the case of THF as a
solvent, 2.5 ml (mmol Mg*)À1 of Et2O was added) was
washed with 2.5 ml (mmol Mg*)À1 of diluted hydrochloric
acid (1:9, v/v), 2.5 ml (mmol Mg*)À1 of satd. aqueous
Na2SO3, twice with 2.5 ml (mmol Mg*)À1 of water and dried
with anh. MgSO4. Solvents were removed by vacuum rotary
evaporator, followed by drying in vacuo (RT, 0.1 kPa, 24 h).
For final purification, column chromatography was
employed.
4.2. Preparation of activated magnesium [16]
A flask was charged with Mg (500 mg, 20.6 mmol), 1,2-
dibromoethane (1 ml) and Et2O (2 ml). After the vigorous
reaction started, a solution of the remaining 1,2-dibro-
moethane (overall 6.54 g, 34.8 mmol) in Et2O (25 ml) was
added dropwise at such a rate to preserve vigorous reflux
(about 10 min). After the addition was complete, the mixture
was heated for an additional 0.5 h under reflux, followed by
distilling off Et2O. All residual volatile components were
removed by heating in vacuo (200 8C, 0.5 h, 0.1 kPa). After
cooling to RT, THF (or other ethereal solvent, 40 ml) was
added followed by a fast addition of potassium metal in
small pieces (1.45 g, 37.0 mmol, washed three times with
dry pentane). The mixture was then heated for 2 h to reflux,
cooled to RT and the black suspension of activated Mg was
used immediately.
4.3.5. Non-aqueous work-up
The crude reaction mixture was diluted with 25 ml
(mmol Mg*)À1 of CH2Cl2 and desalinated by column
chromatography (SiO2, 5 cm column, CH2Cl2). Solvents
were removed by vacuum rotary evaporator, followed by
drying in vacuo (RT, 0.1 kPa, 24 h). For final purification,
column chromatography was employed.
4.3.6. 2,2-Dibromo-2-fluoro-1-phenylethan-1-ol (4a)
CBr3F (1a, 4.82 g, 17.8 mmol), activated magnesium and
benzaldehyde (3, 1.88 g, 17.7 mmol) afforded according to
general procedure A, followed by aqueous work-up and
column chromatography (SiO2, eluent hexane-ethyl acetate
5:1) unreacted benzaldehyde (461 mg), fluorohaloalcohol
4a (951 mg, 18.0%, RF 0.38, colourless liquid) and
4.3. Reactions of activated magnesium
4.3.1. General procedure A
A freshly prepared suspension of activated magnesium
was diluted with 2.5 ml (mmol Mg*)À1 Et2O (or other
ethereal solvent), cooled to the desired temperature (usually
À100 8C) and the electrophile added, followed by careful
dropwise addition of 0.9 mmol (mmol Mg*)À1 of fluoroha-
lomethane 1 dissolved in 0.5 ml (mmol Mg*)À1 of ethereal
solvent on the wall of the reaction flask. The mixture was
stirred for 30 min while still cooled and then the reaction
was quenched at this temperature by addition of 1 mmol
(mmol Mg*)À1 Br2. After warming to RT, the mixture
underwent aqueous or non-aqueous work-up (see below).
1
triphenyldioxolane 5 (295 mg, 16.5%, RF 0.58). H, 13C
and 19F NMR spectra of compound 4a were identical with
1
published data [9], side-product 5 was identified by its H
and 13C NMR spectra [22].
Similarly, from CBr3F (1a, 4.83 g, 17.8 mmol), activated
magnesium and benzaldehyde (3, 1.89 g, 17.8 mmol) were
obtained by general procedure B, aqueous work-up and
column chromatography as above unreacted benzaldehyde
(1.23 g) and fluorohaloalcohol 4a (878 mg, 16.6%). No
formation of the side-product 5 was observed.
4.3.2. General procedure B
Similarly, CBr3F (1a, 4.53 g, 16.7 mmol), activated
magnesium and benzaldehyde (3, 1.78 g, 16.8 mmol)
afforded by general procedure C, aqueous work-up and
column chromatography as above unreacted benzaldehyde
(605 mg), fluorohaloalcohol 4a (853 mg, 17.0%) and
dioxolane 5 (53 mg, 3.1%).
A freshly prepared suspension of activated magnesium
was diluted with 1 ml (mmol Mg*)À1 of diethyl ether (or
other ethereal solvent), cooled to the desired temperature
(mostly À100 8C) and 0.9 mmol (mmol Mg*)À1 of fluor-
ohalomethane 1 dissolved in 1 ml (mmol Mg*)À1 of ethereal

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1394
4.3.7. 1,1-Dibromo-1-fluoropentan-2-ol (8)
(SiO2, eluent hexane-ethyl acetate 5:1) fluorohaloalcohol
4b as the sole fluorinated compound (9 mg, 0.2%). 1H, 13
C
CBr3F (1a, 4.79 g, 17.7 mmol), activated magnesium and
butyraldehyde (6, 1.28 g, 17.8 mmol) afforded according to
general procedure B, followed by aqueous work-up and
fractional distillation, fluorohaloalcohol 8 (1.77 g, 38.0%,
b.p. 52–60 8C/2.5 kPa, colourless liquid). 1H NMR
(300.0 MHz, CDCl3): d 0.96 (3H, m, H-5), 1.40 (4H, m,
H-3 and H-4), 2.83 (1H, bs, OH), 3.84 (1H, m, H-2); 13C
NMR (75.4 MHz, CDCl3): d 13.8 (s, C-5), 18.8 (s, C-4), 34.1
and 19F NMR spectra of compound 4b were identical with
the published data [23].
4.3.11. (Bromodifluoromethyl)dimethylphenylsilane
(11b)
CBr2F2 (1b, 3.54 g, 16.9 mmol), activated magnesium and
dimethylphenylsilyl chloride (10, 3.12 g, 18.8 mmol)
afforded according to general procedure A followed by
non-aqueous work-up light yellow liquid (2.06 g). This was
diluted with pentane (150 ml) and washed with conc. H2SO4
(3 Â 50 ml). Removal of solvents on vacuum rotary
evaporator and final drying in vacuo gave 680 mg of
colourless liquid, which furnished after separation by column
chromatography (SiO2, cyclohexane) fluorohalosilane 11b
2
(s, C-3), 81.0 (d, JCF = 21.0 Hz, C-2), 104.4 (d,
1JCF = 321.0 Hz, C-1); 19F NMR (282.2 MHz, CDCl3):
3
À59.6 (d, JHF = 9 Hz); GC–MS m/z (rel. int.): 264 (M+,
0.2), 221 (1), 191 (2), 140 (5), 121 (2), 111 (2), 92 (1), 73
(70), 55 (100), 43 (35); IR (CHCl3): n 3444 br, 2964 s, 2934
m, 2876 m, 1735 br, 1467 m, 1382 m, 1261 m. Anal. Calcd.
for C5H9Br2FO: C, 22.8; H, 3.4; F, 7.2. Found: C, 21.9; H,
3.3; F, 7.7.
1
(520 mg, 11.6%, colourless liquid). H, 13C and 19F NMR
spectra of compound 11b were identical with the published
data [24].
4.3.8. 1,1-Dibromo-1-fluoro-2-phenylpropan-2-ol (9)
CBr3F (1a, 4.82 g, 17.8 mmol), activated magnesium and
acetophenone (7, 2.20 g, 18.3 mmol) afforded according to
general procedure B, followed by aqueous work-up and
column chromatography (SiO2, eluent hexane-ethyl acetate
5:1) unreacted acetophenone (7) and fluorohaloalcohol 9
4.3.12. 2-Bromo-2-chloro-2-fluoro-1-phenylethan-1-ol
(4c)
CBr2ClF (1c, 3.77 g, 16.7 mmol), activated magnesium
and benzaldehyde (3, 1.77 g, 16.7 mmol) afforded according
to general procedure B followed by aqueous work-up 3.72 g
of colourless liquid. Column chromatography (SiO2, eluent
hexane-ethyl acetate 5:1) furnished fluorohaloalcohol 4c
(270 mg, 6.4%) as a mixture of diastereoisomers 4cA, 4cB in
about 1:1 ratio (19F NMR). 1H NMR (300.0 MHz, CDCl3): d
3.0 (bs, 1H, OH), 5.08 (d, 1H, 3JHF = 7.9 Hz, 4cA H-1), 5.15
(d, 1H, 3JHF 7.9 Hz, 4cB H-1), 7.65 (m, 5H, Ph-H); 13C NMR
(75.4 MHz, CDCl3): d 81.9 (d, 2JCF = 20 Hz, 4cA C-1), 82.1
1
(2.64 g, 47.5%, colourless liquid). H, 13C and 19F NMR
spectra of compound 9 were identical with the published
data [9].
4.3.9. (Dibromofluoromethyl)dimethylphenylsilane
(11a)
CBr3F (1a, 4.58 g, 16.9 mmol), activated magnesium and
dimethylphenylsilyl chloride (10, 2.88 g, 16.9 mmol)
afforded according to general procedure B followed by
non-aqueous work-up yellow liquid (4.37 g). This was
diluted with pentane (200 ml) and washed with conc. H2SO4
(5 Â 50 ml). Removal of solvents in vacuo and final drying
in vacuo afforded fluorohalosilane 11a (3.47 g, 63.0%,
colourless liquid). 1H NMR (300.0 MHz, CDCl3): d 0.57 (s,
6H, Si-CH3), 7.34 (m, 3H, Ph-H), 7.62 (d, 2H, J = 6.8 Hz,
Ph-H); 13C NMR (75.4 MHz, CDCl3): d À5.2 (s, Si-CH3),
2
1
(d, JCF = 20 Hz, 4cB C-1), 113.4 (d, JCF = 310 Hz, C-2),
128.1 (s, Ph), 128.4 (s, Ph), 129.4 (s, Ph), 134.6 (s, Ph); 19
F
3
NMR (282.2 MHz, CDCl3): À62.1 (d, JHF = 8 Hz, 4cA),
À64.2 (d, 3JHF = 8 Hz, 4cB). Anal. Calcd. for C8H7BrClFO:
C, 37.9; H, 2.8; F, 7.5. Found: C, 38.6; H, 2.9; F, 7.7.
4.3.13. 2,2,2-Trifluoro-1-phenylethan-1-ol (4d)
CF3I (1d, 3.26 g, 17.7 mmol) was condensed into a
calibrated flask cooled to À78 8C, diluted with Et2O (20 ml)
and transferred by a cooled canula to the dispersion of
activated magnesium in Et2O. Then, a solution of
benzaldehyde (3, 1.77 g, 16.7 mmol) in Et2O was added
according to general procedure B. Aqueous work-up
afforded 538 mg of colourless liquid which we were not
able to separate fully by column chromatography. Estimated
1
103.8 (d, JCF = 339.9 Hz, CBr2F), 128.0 (s, Ph), 130.8 (s,
Ph), 131.3 (s, Ph), 135.0 (s, Ph); 19F NMR (282.2 MHz,
CDCl3): À76.4 (s); GC–MS m/z, (rel. int.): 326 (M+, 0.1),
265 (1), 247 (M+-Br, 1), 205 (8), 201 (8), 168 (M+-Br2, 20),
149 (8), 135 (100), 119 (12), 105 (30); IR (CHCl3): n 3000 w,
1591 w, 1255 m, 1116 m, 1080 m. Anal. Calcd. for
C9H11Br2FSi: C, 33.2; H, 3.4; Br, 49.0; F, 5.8. Found: C,
32.8; H, 3.5; Br, 48.9; F, 5.8.
1
yield from careful analysis of H NMR spectra was about
1
4%. H, 13C and 19F NMR spectra of compound 4d were
identical with the published data [25].
4.3.10. 2-Bromo-2,2-difluoro-1-phenylethan-1-ol (4b)
CBr2F2 (1b, 3.68 g, 17.6 mmol), activated magnesium
and benzaldehyde (3, 1.86 g, 17.5 mmol) afforded according
to general procedure A followed by aqueous work-up 2.94 g
of light yellow liquid. Vacuum distillation of this crude
product gave 234 mg of colourless liquid (b.p. 107–113 8C/
3.3 kPa), which furnished by column chromatography
Acknowledgements
We thank the Grant Agency of the Czech Republic (Grant
No. 203/02/0716) and the Ministry of Education of the

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[12] J. Kvıcala, A. Pelter, Collect. Czech. Chem. Commun. 66 (2001)
Czech Republic (Project No. 223100001) for financial
support of this project.
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´ˇ
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[13] J. Kvıcala, R. Hrabal, J. Czernek, I. Bartosova, O. Paleta, A. Pelter, J.
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