Synthesis of the First Perfluoro-spiro-bis-crown Ethers

Full text of DOI:10.1021/jo961628o

J . Org. Chem. 1997, 62, 1527-1528
1527
Syn th esis of th e F ir st
P er flu or o-sp ir o-bis-cr ow n Eth er s
Han-Chao Wei, Vincent M. Lynch, and
Richard J . Lagow*
Department of Chemistry and Biochemistry, The University
of Texas at Austin, Texas 78712
Received August 20, 1996
In tr od u ction
Since the first perfluoro crown ethers were prepared
1
by members of our research group, many new perfluoro
2
crown ethers have been synthesized, and medical ap-
1
9
3
plications such as F NMR imaging and oxygen carrier
applications2b as well as new chemistry associated with
these compounds are currently under study. Perfluoro
crown ethers do not form extremely stable complexes
with metal cations because the basicities of perfluoro
crown ethers decrease as the amount of fluorine substitu-
tion increases.5 On the contrary, perfluoro crown ethers
form complexes with certain anions in the gas phase.4
In order to explore the chemistry of theses new com-
pounds, the preparation of new perfluoro crown ethers,
such as multilooped perfluoro crown ethers, is very
important. We report in this paper the syntheses of the
4
F igu r e 1. X-ray crystal structure of 1 (all fluorine atoms are
omitted for clarity).
compounds. The yields of 1-3 are low because of the
steric hindrance between the eight fluorine atoms that
are located next to the spiro carbon.
The 19F NMR spectra of 1-3 exhibit distinct signals
at two regions. One shows a singlet at approximately
6
first perfluoro-spiro-bis-crown ethers, perfluoro-spiro-bis-
[19]crown-6 (1), perfluoro-spiro-bis[16]crown-5 (2), and
perfluoro-spiro-bis[13]crown-4 (3), by elemental fluorine.
-66 ppm, which corresponds to the resonances of the
eight fluorine atoms that are located next to the spiro
carbon; the other one shows a singlet or a multisinglet
at approximately -89 ppm, which corresponds to the
resonances of fluorine atoms of the -OCF CF O- units.
2 2
A crystal of 1 suitable for single-crystal structural
determination was obtained by recrystallization from
3 3
CDCl /CFCl (1/1). The structure was solved by direct
2
methods and refined on F with anisotropic displacement
parameters for all atoms. The molecule lies on a crystal-
lographic 2-fold rotation axis that passes through the
spiro carbon, C1. One of the ethylene groups was found
to be disordered about two orientations representing two
Resu lts a n d Discu ssion
different conformations for that group. Final R ) 0.0451,
2
R
w
(F ) ) 0.1011 for 2215 unique reflections. Experimen-
The major side products of direct fluorination in the
experiments are ring-opening and partially fluorinated
tal details, position parameters, and structural data
7
including bond lengths and angles for 1 are available.
A graphical representation of 1 is given in Figure 1. The
(
1) Lin, W. H.; Bailey, W. I.; Lagow, R. J . J . Chem. Soc., Chem.
Commun. 1985, 1350.
2) (a) Clark, W. D.; Lin, T. Y.; Maleknia, S. D.; Lagow, R. J . J . Org.
8
crystal structure of 4‚2LiI‚4H
2
O has been reported. The
hydrocarbon spiro crown ether (4) is coordinated by two
(
Chem. 1990, 55, 5933. (b) Lin, T. Y.; Lagow, R. J . J . Chem. Soc., Chem.
Commun. 1991, 12. (c) Lin, T. Y.; Roesky, H. W.; Lagow, R. J . Synth.
Commun. 1993, 23, 2451.
+
Li ions and four water molecules. Such coordinating
species will distort the geometry of the parent hydrocar-
bon spiro crown ether. Figures 2 and 3 show this clearly
to be the case.
(
3) Schweighardt, F. K.; Rubertone, J . A. U.S. Patent 4,838,274,
989.
4) (a) Brodbelt, J . S.; Maleknia, S. D.; Liou, C. C.; Lagow, R. J . J .
1
(
Am. Chem. Soc. 1991, 113, 5913. (b) Brodbelt, J . S.; Maleknia, S. D.;
Lagow, R. J .; Lin, T. Y. J . Chem. Soc., Chem. Commun. 1991, 1705.
The syntheses of the new types of perfluoro macrocyclic
ethers, double-looped perfluoro crown ethers, is a new
frontier for further studies of host-guest chemistry in
the gas phase. Perfluro-spiro-bis-crown ethers 1-3 are
currently being investigated to determine their binding
abilities for oxygen and other molecules.
(c) Brodbelt, J . S.; Liou, C. C.; Maleknia, S. D.; Lin, T. Y.; Lagow, R.
J . J . Am. Chem. Soc. 1993, 115, 11069. (d) Lin, T. Y.; Lin, W. H.; Clark,
W. D.; Lagow, R. J .; Larson, S. D.; Simonsen, S. H.; Lynch, V. M.;
Brodbelt, J . S.; Maleknia, S. D.; Liou, C. C. J . Am. Chem. Soc. 1994,
1
16, 5172.
5) (a) Kimura, E.; Shionoya, M.; Okamoto, M.; Nada, H. J . Am.
(
Chem. Soc. 1988, 110, 3679. (b) Shionoya, M.; Kimura, E.; Iitaka, Y.
J . Am. Chem. Soc. 1990, 112, 9237.
(
6) (a) We followed the simple crown ether compound nomenclature
(7) The author has deposited atomic coordinates for this structure
with the Cambridge Crystallographic Data Centre. The coordinates
can be obtained, on request, from the Director, Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK.
(8) Czugler, M. and Weber, E. J . Chem. Soc., Chem. Commun. 1981,
472.
proposed by Pedersen: Pedersen, C. J . J . Am. Chem. Soc. 1967, 89,
017. Pedersen, C. J .; Frensdorff, H. K. Angew. Chem., Int. Ed. Engl.
972, 11, 16. (b) For more discussion of new nomenclature of crown
ether compounds see: Weber, E.; V o¨ gtle, F. Inorg. Chim. Acta 1980,
5, L65.
7
1
4
S0022-3263(96)01628-3 CCC: $14.00 © 1997 American Chemical Society

1
528 J . Org. Chem., Vol. 62, No. 5, 1997
Notes
Ta ble 1. Dir ect F lu or in a tion Con d ition s for 1-3
stage He (mL/min) F2 (mL/min)
T (°C)
time (h)
1
2
3
4
5
6
400
400
10
10
0
0
100
10
10
10
-20
-20
0
ambient (∼36)
ambient (∼36)
ambient (∼36)
0.5
6
12
24
24
24
0
10
Chemical shifts are given in ppm with negative values indicating
resonances at higher frequencies. Elemental compositions were
studied by high-resolution mass spectroscopy employing chemi-
cal ionization in the positive mode.
Syn th esis of 4-6. Hydrocarbon starting materials for direct
fluorination were prepared by modification of the previous
work.10 In a typical reaction, pentaerythritol (6.1 g, 0.045 mol)
and potassium metal (8 g, 0.2 mol) were dissolved in 1 L of tert-
butyl alcohol, and then the solution was heated under argon
atmosphere at reflux for 2 h. Pentaethylene glycol ditosylate
F igu r e 2. Superposition of 1 onto the equivalent atoms of
the hydrocarbon. The atoms used in the fit are labeled. The
dashed lines show the atoms of 1. It is obvious that there are
large conformational differences between the two molecules.
(50 g, 0.09 mol) in 500 mL of dry dioxane was then added
dropwise to the above solution over 8 h, and then the resultant
mixture was stirred at reflux for 24 h. Workup and column
chromatography using silica gel with dichloromethane/methanol
(20/1) eluent gave 4 in 18% yield. Compounds 5 and 6 were
prepared in the same manner by using sodium and lithium metal
with tetraethylene glycol ditosylate and triethylene glycol dito-
1
sylate in 20 and 17% yields, respectively. The MS and H NMR
1
1
spectra of 4-6 were in agreement with published data.
Dir ect F lu or in a tion . The direct fluorination reactions were
performed in a manner similar to the reactions that we have
described previously.12 Reaction details are summarized in
Table 1. In a typical reaction, compound 4 (4.5 g) was dissolved
in 1,1,2-trichlorotrifluoroethane (300 mL); subsequently, the
solution was slowly introduced into a stainless steel reactor that
contained 1,1,2-trichlorotrifluoroethane (600 mL), excess sodium
fluoride, and a fluorine-helium mixture (stage 2; Table 1).
During the next 84 h both the relative fluorine concentration
and the reaction temperature were slowly raised.
P er flu or o-sp ir o-bis[19]cr ow n -6 (1). Pure product (>99%
purity) was collected by preparative GC as white solid in 19%
yield. The retention time was 148.4 min: MS m/ z (identifica-
+
tion, intensity) 1385 ((M - F) , 100); HRMS calcd for C25
47 12
F O
+
19
(
M - F) 1384.8639; found 1384.8626; F NMR δ -66.93 (s,
8
F), -89.49 (s, 40F).
P eflu or o-sp ir o-bis[16]cr ow n -5 (2). Pure product (>99%
purity) was obtained as a colorless oil in 16% yield. The
retention time was 66.2 min: MS m/ z (identification, intensity)
+
+
1
1
(
39
153 ((M - F) , 100); HRMS calcd for C21F O10 (M - F)
152.8869, found 1152.8881; 19F NMR δ -66.47 (s, 8F), -89.59
s, 16F), -89.94 (s, 8F), -90.10 (s, 8F).
P er flu or o-sp ir o-bis[13]cr ow n -4 (3). Pure product (>98%
purity) was obtained as colorless oil in 13% yield. The retention
time was 30.8 min: MS m/ z (identification, intensity) 921 ((M
+
+
-
F) , 100); HRMS calcd for C17
20.9096; 19F NMR δ -66.66 (s, 8F), -89.38 (s, 16F), -89.64
s, 8F).
31 8
F O (M - F) 920.9098, found
9
(
Ack n ow led gm en t. We are grateful for substantial
support from the U.S. Department of Energy Division
of Advanced Energy Projects (DE-FG05-91ER12119)
and the Office of Naval Research.
F igu r e 3. Superposition of 1 onto the equivalent atoms of
the hydrocarbon. In this figure, the atoms of one half of the
spiro compound are used in the comparison (less the disordered
atoms in 1). The dashed lines show the atoms of 1.
Su p p or tin g In for m a tion Ava ila ble: 19F NMR spectra (3
pages). This material is contained in libraries on microfiche,
immediately follows this article in the microfilm version of the
journal, and can be ordered from the ACS; see any current
masthead page for ordering information.
Exp er im en ta l Section
Gen er a l Meth od s. Perfluorinated products were purified by
9
preparative GC equipped with a 815Z column, 10 ft × 0.25 in.
2
5% 815Z on chromosorb A 60/80. Helium flow rate was 45 mL/
min, and column temperature was 200 °C. The purity of the
J O961628O
1
9
perfluorinated products was monitored on a 815Z column.
NMR were recorded at 282 MHz using CDCl as the lock solvent
and CFCl as the internal standard (CDCl /CFCl ) 1/1).
F
3
(
10) Bogatsky, A. V.; Lukyanenko, N. G.; Lobach, A. V.; Nazarova,
N. Yu.; Karpenko, L. P. Synthesis 1984, 139.
11) Weber, E. J . Org. Chem. 1982, 47, 3478.
3
3
3
(
(
9) BRAYCO 815Z perfluoropolyether oil, Castrol, Inc., Bray Prod-
(12) Bierschenk, T. R.; J uhlke, T. J .; Lagow, R. J .; Kawa, H. U. S.
Patent 5, 093, 432, 1992.
ucts Division, Irvine, CA.