Fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 and XeF2

Article abstract of DOI:10.1016/j.jfluchem.2005.12.027

The selective fluorolactonization was achieved by treatment of cis-5-norbornene-2,3-endo-dicarboxylic acid or its monomethyl and dimethyl esters with F-TEDA-BF₄ or XeF₂. The reactions of 5-norbornene-endo-2-carboxylic acid and its monomethyl ester with F-TEDA-BF ₄ or XeF₂ proceed in a non-selective manner to give fluorolactonization, addition and rearrangement products. The basic factor responsible for selectivity of the fluorolactonization is the presence of two endo-oriented carboxyl groups in the substrate molecule. The electrophilicity and type of the fluorinating agent is of secondary importance in this regard. It is postulated that the fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF₄ or XeF₂ is realized mainly via "open" fluoronorbornyl carbocation intermediates which in the reaction with XeF₂ are postulated as the tight ion pairs.

Full text of DOI:10.1016/j.jfluchem.2005.12.027

Journal of Fluorine Chemistry 127 (2006) 377–385
www.elsevier.com/locate/fluor
Fluorolactonization of norbornenecarboxylic acids and
their methyl esters with F-TEDA-BF4 and XeF2
a
Lyudmila F. Lourie a, Yurii A. Serguchev a, , Galina V. Shevchenko ,
*
Maxim V. Ponomarenko a, Alexander N. Chernega a,1,
Eduard B. Rusanova,1, Judith A.K. Howard b,1
a Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya str., 02094 Kyiv, Ukraine
b Department of Chemistry, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK
Received 9 September 2005; received in revised form 28 December 2005; accepted 30 December 2005
Available online 2 March 2006
Abstract
The selective fluorolactonization was achieved by treatment of cis-5-norbornene-2,3-endo-dicarboxylic acid or its monomethyl and dimethyl
esters with F-TEDA-BF4 or XeF2. The reactions of 5-norbornene-endo-2-carboxylic acid and its monomethyl ester with F-TEDA-BF4 or XeF2
proceed in a non-selective manner to give fluorolactonization, addition and rearrangement products. The basic factor responsible for selectivity of
the fluorolactonization is the presence of two endo-oriented carboxyl groups in the substrate molecule. The electrophilicity and type of the
fluorinating agent is of secondary importance in this regard. It is postulated that the fluorolactonization of norbornenecarboxylic acids and their
methyl esters with F-TEDA-BF4 or XeF2 is realized mainly via ‘‘open’’ fluoronorbornyl carbocation intermediates which in the reaction with XeF2
are postulated as the tight ion pairs.
# 2006 Elsevier B.V. All rights reserved.
Keywords: Fluorolactonization; Norbornenecarboxylic acids; Selectivity; Fluorocarbocations
1. Introduction
(F-TEDA-BF4) [7,8], but the selectivity of these reactions was
not high.
Electrophilic cyclization of unsaturated carboxylic acids is
useful as a method to prepare lactones [1–3]. Although many
electrophilic agents (halogens, metal salts, sulfenyl halides,
acids and peracids) were used in the cyclization, such
traditional fluorinating electrophiles as F2, XeF2, RCO2F and
CF3OF that the first to introduce by Barton et al. [4] were not
employed for this purpose, evidently because of their high
reactivity making difficult the control of the addition and
cyclization steps.
The development of simple one-pot syntheses of fluorinated
lactones is important as these compounds are similar in
structure to biologically active fluorinated carbohydrates
[9,10]. The electrophilic fluorocyclization of norbornenecar-
boxylic acids is of particular interest owing to the structural
similarity of these compounds to natural terpenes. The products
of the reactions of norbornene with electrophilic fluorinating
agents depend strongly on the reagents, reaction pathways and
reaction conditions. Norbornene reacting with F-TEDA-BF4 in
acetonitrile yields only two rearranged products of the Ritter
reaction, exo-2-acetamido-syn-7-fluoronorbornane and exo-2-
acetamido-anti-7-fluoronorbornane; other rearranged products
substituted by fluorine, hydroxy or methoxy groups are formed
when the reaction is carried out in the presence of water or
methanol [11].
Recently fluorolactonization of unsaturated carboxylic acids
was performed with such soft electrophilic fluorinating agents
as N-fluoropentachloropyridinium triflate [5], iodotoluene
difluoride, amine-HF complexes [6], and 1-chloromethyl-4-
fluoro-1,4-diazoniabicyclo[2.2.2]octane-bis(tetrafluoroborate)
If xenon difluoride is used for the norbornene fluorination in
chlorinated organic solvents, up to seven fluorination products
are formed depending on the catalyst used (HF, BF3ꢀOEt2,
C6F5SH) [12–14]. The reaction in methanol [15] or in alcohols
* Corresponding author. Tel.: +7 44 5590436; fax: +7 44 5732643.
E-mail address: serg@mail.kar.net (Y.A. Serguchev).
1
XRD investigation.
0022-1139/$ – see front matter # 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2005.12.027

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L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
with electron-withdrawing substituents, in the presence of
boron trifluoride etherate leads, aside from fluorination, to
alkoxyfluorination and alcohol addition products [16]. When
norbornene was fluorinated by XeF2 in acetonitrile with
photochemical initiation, unrearranged 2,3-difluorides were
found and the products of addition of fluorine and acetonitrile at
positions 2 and 3 of the norbornane structure [17].
In order to determine the influence of electrophilicity of the
fluorinating agent, substrate’s structure factor, reaction condi-
tions and mechanism on competition of the cyclization,
addition and rearrangement processes, we studied the flu-
orination of 5-norbornene-endo-2-carboxylic acid 1a, its
methyl ester 1b, cis-5-norbornen-endo-2,3-dicarboxylic acid
2a, its dimethyl ester 2b and monomethyl ester 2c by
electrophilic agents, F-TEDA-BF4 and xenon difluoride.
F-TEDA-BF4 was selected as easy-to-handle, selective,
monofluorinating and soft agent (Ep = 0.04 V [18]), that widely
used for fluorination of unsaturated compounds [19–24]. On the
other hand XeF2 is used as a rather strong difluorinating
electrophile (EAXeFþ ¼ 10 eV [25]) that shows a low-selectiv-
ity in fluorination of norbornenes.
Fig. 1. Perspective view and labeling scheme for the molecule of 6b. Selected
˚
bond lengths (A) and torsion angles (8): C(1)–C(2) 1.551 (4), C(1)–C(6) 1.536
(4), C(1)–C(7) 1.515 (4), C(2)–C(3) 1.557 (4), C(3)–C(4) 1.526 (4), C(4)–C(5)
1.535 (4), C(4)–C(7) 1.524 (3), C(5)–C(6) 1.552 (4), C(6)C(1)C(7)F(1) ꢁ62.3,
C(5)C(4)C(7)F(1) 69.6, C(2)C(1)C(7)F(1) ꢁ177.0, C(3)C(4)C(7)F(1) 177.9.
should be noted that in our previous short communication [7]
we presented the fluorination of a mixture of endo- and exo-
isomers of 1a with suspension of F-TEDA-BF4 in boiling
acetonitrile and only minor yields of Ritter products were
found.
2. Results and discussion
2.1. Fluorination of norbornenecarboxylic acids and their
methyl esters using F-TEDA-BF4
The structure of ester 6b was unambiguously determined by
single crystal X-ray diffraction method (Fig. 1).
The 19F NMR signal of the Ritter product 7b
(d = ꢁ168.9 ppm) corresponds to the exo-oriented fluorine in
the norbornane structure [7,11,13,27]. In the 1H NMR
spectrum, the double doublet at 4.99 ppm (3JH,F = 30.6 Hz),
which belongs to the N–CH–CF proton, indicates its exo-
position and the endo-orientation of the NHCOCH3 group.
The trace product isolated in a small amount lactame 8 is
evidently a cyclization product of 7a or 7b. The presence of two
The reaction of acid 1a with F-TEDA-BF4 in acetonitrile
solution at room temperature proceeds unselectively yielding
several products, which were isolated by column chromato-
graphy on silica gel (Scheme 1).
The cyclization products of 1a are exo-fluoro-g-lactone 3
and fluorine-free g-lactone 4. These compounds were
previously described [7,26] and identified by spectral
characteristics. g-Lactone 4 is evidently formed in acidic
cyclization caused by a proton released during formation of
fluorolactone 3. This was confirmed by the reaction of methyl
ester 1b with F-TEDA-BF4 where lactone 4 was formed
in virtually trace amounts. In both cases rearrangement
of the starting substrate proceeds in parallel with the
lactonization.
1
sets of signals in the H NMR spectrum at 2.48 ppm (s, CH3)
3
and 4.42 ppm (dd, H–C–N, JH,F = 21.0 Hz) confirms the
structure given.
In order to exclude Ritter adduct formation from the reaction
pathways described in Scheme 1, we carried out reactions of 1a
and 1b with F-TEDA-BF4 in nitromethane. Two major
products, g-fluorolactone 3 and 5a or 5b, were isolated in
about 1:1 proportion, the unfluorinated g-lactone 4 being a by-
product.
Acetonitrile is involved in the reaction, adding together with
fluorine, giving products 6a,b and 7a,b (Ritter reaction). It
Scheme 1.

L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
379
fluoronium carbocations [41], we postulate the intermediacy of
open fluorocarbocations A and B in this reaction (Scheme 3).
Most probably carbocation A is the intermediate in the
formation of g-fluorolactone 3 and Ritter products 7, 8.
Quantum-chemical calculations at the semi-empirical level
PM3 [42] show that cyclization of cation B into a six-
membered d-fluorolactone is unfavorable (Ea = 121 kJ molꢁ1
)
and this is confirmed by its absence among the reaction
products. Meerwein–Wagner rearrangement of cation B gives
carbocation C whose deprotonation gives the unsaturated
rearranged compounds 5a and 5b while the reaction with an
acetonitrile molecule leads to the rearranged Ritter products 6a
and 6b.
A low activation energy of the transformation of cation A
into lactone 3 (1.3 kJ molꢁ1 [42]) and the availability of two
carboxylated groups in the molecules of 2a, 2b and 2c that can
react with proper carbocations on C-5 and C-6 carbons suggests
a selective character of fluorolactonization in the reaction of
norbornenedicarboxylic acid 2a, its dimethyl and monomethyl
esters 2b and 2c with F-TEDA-BF4. The fluorolactonization of
acid 2a or dimethyl ester 2b by F-TEDA-BF4 in acetonitrile
proceeds quite selectively yielding g-fluorolactones 9a or 9b as
the major products, while the rearranged product 10a or 10b
and the Ritter reaction product 11b are formed only in minor
amounts (Scheme 4).
Scheme 2.
Iodolactonization of g- and d-unsaturated carboxylic acids
and specifically 5-norbornene-endo-2-carboxylic acid, pro-
ceeds with high stereoselectivity due to the synchronous attack
of iodine and carboxylic oxygen on the double bond [1,28–31].
In this case the structure of the cyclic products is formed in the
transition state of the rate-limiting step and it is this that
determines the high selectivity of the iodolactonization.
In contrast fluorolactonization is a multistep process [5,7],
which proceeds similarly to reactions of olefins with
electrophilic NF-agents in nucleophilic and dissociating
solvents [32–34]. As known for reactions of electrophilic
NF-agents with olefins there are two possible mechanistic
pathways: single-electron transfer (SET) [32,35,36] or nucleo-
philic SN2 substitution [37,38] but both mechanisms lead to the
same a fluorinated carbocation which virtually determines the
composition of the reaction products (Scheme 2).
1H and 13C NMR spectra of 11b are similar to the
corresponding spectra of 7b both in chemical shifts and values
3
of JF,H for the H–C–N proton.
Fluorolactonization of monomethyl norbornenedicarboxy-
late 2c leads to g-fluorolactones 9a and 9b in about equal yields
(Scheme 5), which is an additional proof for the intermediacy of
open fluorocarbocations in the reaction.
The formation of the skeletal rearrangement products 5a and
5b, 6a and 6b in the reactions of acid 1a and its methyl ester 1b
with F-TEDA-BF4 suggests a carbocationic mechanism. The
easy isomerization of norbornyl carbocations [39,40] and a
competition of external and intramolecular nucleophiles in the
transformations of the carbocation intermediates make the
fluorolactonization of 1a and 1b non-selective. Taking into
account the inability of fluorine to form three-membered cyclic
The rearranged product 12 has spectral characteristics that
are similar to those of compound 10b. Single crystal X-ray
investigation of compound 12 unambiguously confirmed the
anti-position of the fluorine on the bridge and exo-orientation of
the carboxylic groups in the norbornene frame. The perspective
view of the molecule 12 and selected parameters are given in
Fig. 2.
Scheme 3.

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L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
Scheme 4.
Scheme 5.
2.2. Fluorination of methyl esters of 5-norbornene-endo-2-
carboxylic and cis-5-norbornene-endo-2,3-dicarboxylic
acids with XeF2
The effect of XeF2 on the selectivity of the fluorocyclization
was studied, using methyl ester 1b and dimethyl ester 2b as
substrates. The reaction was carried out in the presence of
BF3ꢀEt2O in CH2Cl2 at ꢁ78 8C. Like the reaction of 1b with F-
TEDA-BF4 in acetonitrile, its reaction with XeF2 is non-
selective.
g-Fluorolactone 3, unfluorinated lactone 4 and two
difluorides, 13 and 14, were isolated from the reaction mixture
by silica gel column chromatography (Scheme 6).
Fig. 2. Perspective view, labeling scheme, and crystal packing for the structure
˚
The endo-orientation of fluorine at position 6 of compound
13 was derived from the multiplicity of the 19F NMR signal at
ꢁ193.5 ppm (ddd) (cf. the 19F NMR spectrum of endo-2, exo-5-
difluoronorbornane [14]). The exo-position of the F–C-3 bond
in difluoride 13 is evidenced by the 19F NMR signal at
ꢁ160.0 ppm, whose downfield shift relative to signals of exo-
fluorine in the earlier described fluorinated norbornanes [6,12–
15] can be explained by the adjacent COOCH3 group. The exo-
position of fluorine at C-3 is also indicated by the C–F coupling
(3JC,F ꢂ 0.5 Hz) for the C O carbon in the 13C NMR. The 1H,
13C and 19F NMR spectra of compound 14 are similar to those
of structurally closely related compound 18 (Scheme 7) whose
structure was established by single crystal X-ray diffraction
(Fig. 3).
of 12. Selected bond lengths (A) and torsion angles (8): C(1)–C(2) 1.556 (3),
C(1)–C(6) 1.515 (3), C(1)–C(7) 1.521 (3), C(2)–C(3) 1.579 (3), C(3)–C(4)
1.568 (3), C(4)–C(5) 1.516 (3), C(4)–C(7) 1.524 (3), C(5)–C(6) 1.314 (4),
C(6)C(1)C(7)F(1) ꢁ68.7, C(5)C(4)C(7)F(1) 69.6, C(2)C(1)C(7)F(1) ꢁ177.0,
C(3)C(4)C(7)F(1) 177.9.
exo-Fluoro-g-lactones rather than endo- are formed upon
fluorolactonization. Since the exo-side of the norbornene
system is considered to be less sterically hindered for the attack
of electrophilic agents compared with the endo-side [1,43], the
participation of such a bulky agent as F-TEDA-BF4 in the
reaction explains the selective exo-addition of fluorine to
norbornenecarboxylic acids and their esters.
Scheme 6.

L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
381
Scheme 7.
Two other minor isomeric difluorides, 15 and 16, were
identified in mixture by 19F NMR spectra, where signals at
ꢁ199.3 and ꢁ200.1 ppm (ddd) are characteristic of endo-
fluorine atoms; anti-F signals are observed at ꢁ206.8 and
ꢁ207.4 ppm as doublets. The spectra of these products are
similar to spectra of the structurally related difluoride 19
(Scheme 7), which was studied by single crystal X-ray
diffraction (Fig. 4).
The fluorolactonization of dimethyl ester 2b by XeF2
proceeds with selective yield of g-fluorolactone 9b (Scheme 7).
The by-products are unfluorinated lactone 17 and two
isomeric difluorides, 18 and 19. The structure of the latter was
determined by single crystal X-ray diffraction (Figs. 3 and 4).
The formation of difluorides 14, 15, 16 and 18, 19 in
reactions of 1b and 2b substrates with XeF2 in low polar
CH2Cl2 suggests that the intermediates are fluorocarbocations
as the tight ion pairs, which were postulated by Rozen and
Brand in reactions of F2 with alkenes [44]. The ratio of products
in these reactions is controlled by competition of fluoride
anions and intramolecular carboxylate groups for interaction
with fluorocarbocations.
3. Conclusion
The selective g-fluorolactonization is accomplished on
treatment of cis-5-norbornene-endo-2,3-dicarboxylic acid, its
mono- or di-methyl ester with soft monofluorating agent F-
TEDA-BF4 in acetonitrile. The good yield of g-fluorolacton is
in the reaction of dimethyl ester 2b with strong electrophile
XeF2 in low polar CH2Cl2.
Fig. 3. Perspective view and labeling scheme for the molecule 18. Selected
The reactions of 5-norbornene-endo-2-carboxylic acid or its
methyl ester with F-TEDA-BF4 or XeF2 proceed unselectively
with the formation of products of lactonization, addition and
rearrangements.
˚
bond lengths (A) and torsion angles (8): C(1)–C(2) 1.538 (3), C(1)–C(6) 1.535
(3), C(1)–C(7) 1.515 (3), C(2)–C(3) 1.584 (3), C(3)–C(4) 1.518 (4), C(4)–C(5)
1.532 (3), C(4)–C(7) 1.512 (3), C(5)–C(6) 1.530 (4), C(6)C(1)C(7)F(1) ꢁ62.8,
C(5)C(4)C(7)F(1) 65.1, C(2)C(1)C(7)F(1) ꢁ173.0, C(3)C(4)C(7)F(1) 176.2,
C(3)C(4)C(5)F(2) 162.9, C(1)C(6)C(5)F(2) 126.3, C(7)C(4)C(5)F(2) ꢁ92.1.
It is postulated that the fluorolactonization of norbornene-
carboxylic acids and their methyl esters with F-TEDA-BF4 is
realized via open fluoronorbornyl carbocation intermediates.
The reactions of methyl esters 1b and 2b with XeF2 possibly
involve fluorocarbocations as the tight ion pairs, in which super
week nucleophilic fluoride anion is able to complete with
carboxylate group for carbocation.
Thus the basic factor determining of fluorolactonization in
these reactions is the presence of two carboxylic groups at the
endo positions of the norbornene frame, whereas the
electrophilicity of the fluorinating agent and the reaction
mechanism of rate limiting stage are of secondary importance.
4. Experimental
Fig. 4. Perspective view and labeling scheme for the molecule 19. Selected
˚
1
The H (300 MHz), 13C (75.4 MHz) and 19F (282.2 MHz)
bond lengths (A) and torsion angles (8): C(1)–C(2) 1.537 (3), C(1)–C(6) 1.542
(3), C(1)–C(7) 1.507 (3), C(2)–C(3) 1.575 (3), C(3)–C(4) 1.544 (3), C(4)–C(5)
1.533 (3), C(4)–C(7) 1.525 (3), C(5)–C(6) 1.527 (4), C(6)C(1)C(7)F(1) 61.1,
C(5)C(4)C(7)F(1) ꢁ62.5, C(2)C(1)C(7)F(1) 172.5, C(3)C(4)C(7)F(1) ꢁ174.1,
C(7)C(4)C(5)F(2) ꢁ153.1, C(3)C(4)C(5)F(2) ꢁ47.9, C(1)C(6)C(5)F(2) 118.5.
NMR spectra were recorded on a Varian VXR-300 spectro-
meter using CDCl3 as solvent and TMS or CCl3F as internal
standards. The spectra of compound 6a were recorded in

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L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
DMSO-d6. Mass spectra (EI) were obtained on an MX-1321
instrument at 70 eV.
4.1.3. Methyl anti-7-fluoro-5-norbornene-exo-2-
carboxylate (5b)
1
Colourless oil; H NMR: d 1.39 (1H, ddd, J3endo,3exo
2
Crystals of compounds 6b, 12, 18, 19 were grown from ethyl
acetate.
=
3
4
12.3 Hz, J3endo,2 = 10.5 Hz, J3endo,F = 7.3 Hz, Hendo-3), 1.93
2
Acid 1a was obtained by iodolactonization of a mixture of
endo- and exo-isomers of 5-norbornene-2-carboxylic acid
followed by transformation of the iodolactone into the pure
endo-isomer [45]. Methyl ester 1b, acid 2a, its monomethyl
ester 2c and dimethyl ester 2b were obtained as described
earlier [46–48]. F-TEDA-BF4 and XeF2 were obtained
commercially (Aldrich, Merck).
(1H, dm, J3exo,3endo = 12.3 Hz, Hexo-3), 2.19 (1H, dm,
3J2,3endo = 10.5 Hz, J2,3exo = 4J2,F = 5.1 Hz, H-2), 2.97 (1H,
m, H-4), 3.09 (1H, m, H-1), 3.68 (3H, s, CH3), 4.92 (1H, dm,
3
2J7,F = 59.4 Hz, H-7), 6.12 (2H, m, H-5, H-6); 19F NMR: d
2
ꢁ209.3 (dm, JF,7 = 59.8 Hz). Anal. Calcd for C9H11FO2: C,
63.51; H, 6.51. Found: C, 63.5; H, 6.4.
4.1.4. exo-5-Acetamido-anti-7-fluoronorbornane-exo-2-
carboxylic acid (6a)
4.1. Reactions of 1a, b, 2a–c with F-TEDA-BF4. General
procedure
Colourless crystals, mp 183–184 8C, 1H NMR (DMSO-d6):
2
3
d 1.52 (1H, ddd, J3endo,3exo = 12.9 Hz, J3endo,2 = 10.2 Hz,
4J3endo,F = 6.8 Hz, Hendo-3), 1.69 (2H, m, Hexo-6, Hendo-6), 1.77
(3H, s, CH3), 1.89 (1H, m, Hexo-3), 2.14 (1H, dm,
A mixture of the corresponding acid (5 mmol) and F-
TEDA-BF4 (6 mmol) in 50 mL of acetonitrile was stirred for
40 h at room temperature. The progress of the reaction was
followed by TCL. Once the reaction was complete the solvent
was evaporated, the residue was dissolved in chloroform,
washed with water (30 mL) and the water layer was
additionally extracted with chloroform (2 mL ꢃ 25 mL).
The combined extracts were dried over Na2SO4 and
concentrated. The reactions with F-TEDA-BF4 in nitro-
methane were conducted similarly to the reactions in
acetonitrile. The products were separated by column chro-
matography on silica gel with 2:1 diethyl ether–hexane as
eluent.
3
3J1,6exo = 3.3 Hz, H-1), 2.32 (1H, dm, J2,3endo = 10.2 Hz,
3
3J2,3exo = 4J2,F = 5.2 Hz, H-2), 2.44 (1H, dm, J4,3exo = 3.3 Hz,
H-4), 3.75 (1H, m, H-5), 4.89 (1H, d, 2J7,F = 56.1 Hz, H-7), 7.58
3
(1H, d, JH,5 = 6.9 Hz, NH), 12.31 (1H, bs, OH); 13C NMR
(DMSO-d6): d 22.4 (s, CH3), 26.6 (d, 3J = 8.9 Hz, C-3), 34.3 (s,
3
2
C-6), 41.2 (d, J = 7.2 Hz, C-2), 41.8 (d, J = 18.2 Hz, C-1),
43.2 (d, 2J = 13.6 Hz, C-4), 50.7 (s, C-5), 97.6 (d,
1J = 192.6 Hz, C-7), 168.5 (s, C O), 175.6 (s, C O); 19F
2
NMR (DMSO-d6): d ꢁ202.4 (dm, JF,7 = 55.7 Hz); EIMS
70 eV, m/z (%): 215 [M]+ (11), 195 [M ꢁ HF]+ (8), 85 (21), 43
[C2H3O]+ (100). Anal. Calcd for C10H14FNO3: N, 6.51. Found:
N, 6.6.
exo-5-Fluoro-2,6-norbornanecarbolactone (3), endo-3-car-
boxy-exo-5-fluoro-2,6-norbornanecarbolactone (9a) and exo-5-
fluoro-endo-3-methoxycarbonyl-2,6-norbornanecarbolactone
(9b) were described earlier [7].
4.1.5. Methyl exo-5-acetamido-anti-7-fluoronorbornane-
exo-2-carboxylate (6b)
Colourless crystals, mp 117–118 8C; 1H NMR: d 1.64 (1H,
ddd, J3endo,3exo = 13.5 Hz, J3endo,2 = 10.5 Hz, J3endo,F =
2
3
4
4.1.1. 2,6-Norbornanecarbolactone (4)
White crystals, mp 154–155 8C (lit.: mp 155–156 8C [26]);
1H NMR: d 1.50–1.62 (3H, m, Hendo-3, Hendo-5, Hsyn-7), 1.68–
6.0 Hz, Hendo-3), 1.67–1.78 (1H, m, Hendo-6), 1.82–1.94 (1H,
m, Hexo-6), 1.93 (3H, s, CH3), 2.03 (1H, m, Hexo-3), 2.24 (1H,
2
3
dm, J1,6exo = 3.6 Hz, H-1), 2.33 (1H, dm, J2,3endo = 10.5 Hz,
3
1.80 (2H, m, Hexo-5, Hanti-7), 1.96 (1H, dm, J3exo,3en-
3
do = 12.9 Hz, Hexo-3), 2.45 (1H, bs, H-4), 2.54 (1H, ddm,
3J2,3exo = 4J2,F = 5.1 Hz, H-2), 2.60 (1H, dm, J4,3exo = 4.0 Hz,
3J2,3exo = 11.4 Hz, 3J2,1 = 5.0 Hz, H-2), 3.20 (1H, t,
H-4), 3.66 (3H, s, OCH3), 4.18 (1H, m, H-5), 5.09 (1H, d,
2J7,F = 56.4 Hz, H-7), 5.82 (1H, bs, NH); 19F NMR: d ꢁ204.4
(dm, JF,7 = 57.0 Hz). Anal. Calcd for C11H16FNO3: C, 57.63;
H, 7.03. Found: C, 57.5; H, 7.0.
3
3J1,2 = 3J1,6 = 5.0 Hz, H-1), 4.78 (1H, dd, J6,5exo = 7.8 Hz,
3J6,1 = 5.0 Hz, H-6).
4.1.2. anti-7-Fluoro-5-norbornene-exo-2-carboxylic acid
(5a)
4.1.6. Methyl endo-6-acetamido-exo-5-fluoronorbornane-
endo-2-carboxylate (7b)
1
White crystals, mp 54–56 8C; H NMR: d 1.48 (1H, ddd,
3
4
1
2
Colourless oil; H NMR: d 1.49 (1H, dm, AB, J7syn,7anti =
2J3endo,3exo = 12.8 Hz, J3endo,2 = 10.7 Hz, J3endo,F = 7.3 Hz,
Hendo-3), 2.01 (1H, dm, J3exo,3endo = 12.8 Hz, Hexo-3), 2.27
11.1 Hz, Hsyn-7), 1.70 (1H, ddd, J3endo,3exo = 13.8 Hz,
2
2
(1H, dm, J2,3endo = 10.7 Hz, J2,3exo = 4J2,F = 4.8 Hz, H-2),
3.03 (1H, bs, H-4), 3.19 (1H, bs, H-1), 4.97 (1H, dm,
2J7,F = 59.1 Hz, H-7), 6.19 (2H, m, H-5, H-6), 11.01 (1H, bs,
OH); 13C NMR: d 26.3 (d, 3J = 4.6 Hz, C-3), 40.4 (d,
3J = 5.3 Hz, C-2), 44.4 (d, 2J = 16.3 Hz, C-4), 48.7 (d,
3J3endo,2 = 6.0 Hz, J3endo,4 = 2.0 Hz, Hendo-3), 1.87 (1H, dm,
3
3
3
2
AB, J7anti,7syn = 11.1 Hz, Hanti-7), 1.84–2.00 (1H, m, Hexo-3),
1.98 (3H, s, CH3), 2.46 (1H, m, H-4), 2.72 (1H, ddd,
3J2,3exo = 11.4 Hz, 3J2,3endo = 6.0 Hz, 3J2,1 = 4.0 Hz, H-2), 2.98
(1H, m, H-1), 3.65 (3H, s, OCH3), 4.40 (1H, d, 2J5,F = 53.4 Hz,
2J = 17.9 Hz, C-1), 102.5 (d, J = 204.1 Hz, C-7), 131.0 (s,
H-5), 4.99 (1H, dd, J6,F = 30.6 Hz, J6,1 = 3.9 Hz, H-6), 5.82
(1H, bs, NH); 13C NMR: d 20.5 (s, CH3), 24.9 (d, 3J = 9.5 Hz,
1
3
3
C-5 or C-6), 133.3 (s, C-5 or C-6), 175.3 (s, C O); 19F NMR: d
ꢁ209.2 (dm, 2JF,7 = 59.0 Hz); EIMS 70 eV, m/z (%): 156 [M]+
(14), 91 [M ꢁ COOH-HF]+ (51), 84 (100). Anal. Calcd for
C8H9FO2: C, 61.53; H, 5.81. Found: C, 61.5; H, 5.7.
2
C-3), 35.3 (s, C-7), 41.8 (s, C-2), 41.9 (d, J = 21.5 Hz, C-4),
42.4 (d, 3J = 3.1 Hz, C-1), 51.5 (s, OCH3), 81.0 (d,
2J = 27.0 Hz, C-6), 98.4 (d, 1J = 188.8 Hz, C-5), 169.6 (s,

L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
383
C O), 173.6 (s, C O); 19F NMR:
d
ꢁ168.9 (dd,
4.1.10. 7-anti-Fluoro-cis-5-norbornene-exo-2,3-
dicarboxylic acid monomethyl ester (12)
2JF,5 = 55.4 Hz, 3JF,6 = 30.2 Hz). Anal. Calcd for C11H16FNO3:
C, 57.63; H, 7.03. Found: C, 57.5; H, 7.0.
Colourless crystals, mp 134–135 8C; 1H NMR: d 2.66 (2H,
dm, JH,F = 5.8 Hz, H-2, H-3), 3.24 (2H, m, H-1, H-4), 3.70
4
4.1.7. N-Aceto-exo-5-fluoro-2,6-norbornanecarbolactame
(8)
(3H, s, OCH3), 5.42 (1H, d, 2J7,F = 58.2 Hz, H-7), 6.24 (2H, m,
H-5, H-6), 12.21 (1H, bs, OH); 13C NMR: d 43.9 (d,
Colourless oil; 1H NMR: d 1.50 (1H, dm, AB, 2J7syn,7anti
=
3J = 5.2 Hz, C-2 or C-3), 44.1 (d, J = 5.2 Hz, C-2 or C-3),
3
2
2
47.8 (d, J = 17.8 Hz, C-1, C-4), 52.2 (s, OCH3), 101.5 (d,
13.8 Hz, Hsyn-7), 1.60 (1H, dm, AB, J3endo,3exo = 13.8 Hz,
Hendo-3), 2.00–2.16 (2H, m, Hexo-3, Hanti-7), 2.48 (3H, s,
CH3), 2.57 (1H, dm, 3J2,3exo = 11.4 Hz, H-2), 2.68 (1H, m, H-
1J = 199.7 Hz, C-7), 133.1 (C-5 or C-6), 133.3 (C-5 or C-6),
172.5 (s, C O), 178.3 (s, C O); 19F NMR: d ꢁ211.3 (dm,
3
4
4), 2.96 (1H, tm, J1,2 = 3J1,6 = 5.4 Hz, H-1), 4.31 (1H, d,
2JF,7 = 58.1 Hz, JF,2 = 4JF,3 = 6.0 Hz); EIMS 70 eV, m/z (%):
2J5,F = 50.4 Hz, H-5), 4.42 (1H, dd, J6,F = 21.0 Hz,
214 [M]+ (18), 183 [M ꢁ OCH3]+ (45), 155 [M ꢁ COOCH3]+
(28), 111 [M ꢁ COOCH3-CO2]+ (16), 98 (20), 66 [C5H6]+
(100). Anal. Calcd for C10H11FO4: F, 8.87. Found: F, 8.6.
3
3J6,1 = 5.4 Hz, H-6); 13C NMR: d 24.6 (s, CH3), 30.8 (d,
3J = 10.0 Hz, C-3), 33.3 (s, C-7), 40.6 (s, C-2), 42.4 (d,
2J = 20.6 Hz, C-4), 43.3 (s, C-1), 63.1 (d, J = 28.7 Hz, C-6),
2
96.5 (d, 1J = 192.6 Hz, C-5), 170.3 (s, C O), 177.9 (s, C O);
4.2. Reactions of esters 1b and 2c with XeF2. General
procedure
2
3
19F NMR: d ꢁ173.4 (ddm, JF,5 = 51.0 Hz, JF,6 = 21.7 Hz);
EIMS 70 eV, m/z (%): 197 [M]+ (73), 169 [M ꢁ CO]+
(26), 155 [M ꢁ CH2CO]+ (22), 127 (98), 96 (92), 43
[C2H3O]+ (100). Anal. Calcd for C10H12FNO2: N, 7.10.
Found: N, 6.6.
To a cooled (ꢁ78 8C) solution of XeF2 (4 mmol) in 25 mL of
methylene chloride was added with stirring under the argon
atmosphere a solution of compound 1b or 2c (4 mmol) in 25 mL
of methylene chloride followed by a solution of boron trifluoride
etherate (3 mmol) in 15 mL of methylene chloride. The reaction
mixture was stirred at ꢁ78 8C for 24 h and at 0 8C for 12 h, then
slowlywarmed toroom temperature, andwashedwithwater. The
water layer was extracted with methylene chloride and the
combined extracts, after concentration, were subject to column
chromatography on silica gel eluting the products with diethyl
ether–hexane–methylene chloride (1:4:5).
4.1.8. Dimethyl anti-7-fluoro-cis-5-norbornene-exo-2,3-
dicarboxylate (10b)
White crystals, mp 90–93 8C; 1H NMR: d 2.62 (2H, d,
4JH,F = 5.4 Hz, H-2, H-3), 3.21 (2H, m, H-1, H-4), 3.68 (6H, s,
2CH3), 5.44 (1H, dm, 2J7,F = 58.5 Hz, H-7), 6.22 (2H, bs, H-5,
3
H-6); 13C NMR: d 43.9 (d, J = 3.6 Hz, C-2, C-3), 47.8 (d,
2J = 17.8 Hz, C-1, C-4), 52.2 (s, 2CH3), 101.7 (d,
1J = 199.9 Hz, C-7), 133.2 (s, C-5, C-6), 172.7 (s, 2C O);
2
19F NMR: d ꢁ211.3 (dm, JF,7 = 58.4 Hz); EIMS 70 eV, m/z
4.2.1. Methyl exo-3,endo-6-difluoronorbornane-endo-2-
carboxylate (13)
(%): 228 [M]+ (1), 197 [M ꢁ OCH3]+ (42), 169
[M ꢁ COOCH3]+ (24), 149 [M ꢁ COOCH3-HF]+ (21), 145
[C6H9O4]+ (91), 137 [M ꢁ OCH3-CH3COOH]+ (22), 113
(100), 109 [M ꢁ CH3COOH-COOCH3]+ (46), 84 [C5H5F]+
(80), 59 [C2H3O2]+ (52). Anal. Calcd for C11H13FO4: C, 57.89;
H, 5.74. Found: C, 57.7; H, 5.7.
Colourless oil; 1H NMR:
d
1.08 (1H, ddm,
3J5endo,F = 27.5 Hz, J5endo,5exo = 15.0 Hz, Hendo-5), 1.50–1.80
(2H, m, Hanti-7, Hsyn-7), 2.42 (1H, m, Hexo-5), 2.68 (1H, m, H-
2), 2.80 (1H, m, H-4), 2.96 (1H, m, H-1), 3.70 (3H, s, OCH3),
2
2
4.72 (1H, dm, J3,F = 54.6 Hz, H-3), 5.22 (1H, dm,
2J6,F = 54.0 Hz, H-6); 13C NMR: d 30.9 (dd, 2J = 20.4 Hz,
2
4.1.9. Dimethyl endo-6-acetamido-exo-5-fluoro-cis-
norbornane-endo-2,3-dicarboxylate (11b)
3J = 11.1 Hz, C-5), 32.6 (s, C-7), 41.9 (d, J = 19.8 Hz, C-4),
43.2 (dd, 2J = 23.9 Hz, 3J = 6.7 Hz, C-2), 44.9 (d, 2J = 20.6 Hz,
C-1), 51.9 (s, OCH3), 91.1 (d, 1J = 183.7 Hz, C-3 or C-6), 93.8
White crystals, mp 74–75 8C; 1H NMR: d 1.47 (1H, dm, AB,
2J7syn,7anti = 11.1 Hz, Hsyn-7), 1.97 (1H, dm, AB, J7anti,7syn
=
(d, J = 184.3 Hz, C-3 or C-6), 172.1 (s, C O); 19F NMR: d
2
1
11.1 Hz, Hanti-7), 2.03 (3H, s, CH3), 2.76 (1H, dd,
ꢁ160.0 (m, F-3), ꢁ193. 5 (ddd, JF,6 = 54.0 Hz, JF,5endo
=
27.0 Hz, JF,5exo = 15.5 Hz, F-6). Anal. Calcd for C9H12F2O2:
2
3
3
3
3J4,F = 10.3 Hz, J4,3 = 4.0 Hz, H-4), 3.0–3.24 (3H, m,
3
3J2,3 = 12.0 Hz, J2,1 = 3J3,4 = 4.0 Hz, H-1, H-2, H-3), 3.66
(3H, s, OCH3), 3.72 (3H, s, OCH3), 5.01 (1H, dm,
C, 56.83; H, 6.36. Found: C, 56.7; H, 6.3.
2
3J6,F = 31.5 Hz, H-6), 5.52 (1H, d, J5,F = 51.9 Hz, H-5),
4.2.2. Methyl exo-5,anti-7-difluoronorbornane-exo-2-
carboxylate (14)
5.50 (1H, bs, NH); 13C NMR: d 20.7 (s, CH3), 34.5 (s, C-7),
42.8 (d, 3J = 9.9 Hz, C-3), 42.9 (s, C-2), 44.0 (d, 3J = 3.1 Hz, C-
1), 45.4 (d, 2J = 23.7 Hz, C-4), 51.6 (s, 2OCH3), 81.0 (d,
2J = 25.3 Hz, C-6), 93.9 (d, 1J = 184.2 Hz, C-5), 170.0 (s,
C O), 171.1 (s, C O), 171.7 (s, C O); 19F NMR: d ꢁ177.0
(m); EIMS 70 eV, m/z (%): 287 [M]+ (1), 244 [M ꢁ CH3CO]+
(4), 228 [M ꢁ COOCH3]+ (5), 215 (42), 145 [C6H9O4]+ (47),
113 (28), 84 [C5H5F]+ (47), 59 [C2H3O2]+ (21), 43 [C2H3O]+
(100). Anal. Calcd for C13H18FNO5: C, 54.34; H, 6.31. Found:
C, 54.2; H, 6.3.
1
Colourless oil; H NMR: d 1.35 (1H, ddd, J3endo,3exo
2
=
13.7 Hz, 3J3endo,2 = 10.2 Hz, 4J3endo,F = 6.3 Hz, Hendo-3), 1.82–
2.05 (2H, m, Hexo-3, Hendo-6), 2.08–2.32 (2H, m, H-2, Hexo-6),
3
2.58 (1H, dd, J4,F = 9.0 Hz, J4,3exo = 5.4 Hz, H-4), 2.63 (1H,
3
2
m, H-1), 3.66 (3H, s, OCH3), 4.75 (1H, ddm, J5,F = 53.7 Hz,
3J5,6endo = 6.9 Hz, H-5), 4.99 (1H, d, 2J7,F = 54.9 Hz, H-7); 13
C
3
3
NMR: d 23.3 (dd, J = 11.5 Hz, J = 9.4 Hz, C-3), 36.5 (d,
2J = 23.0 Hz, C-6), 41.4 (d, 3J = 5.7 Hz, C-2), 42.2 (d,
2J = 18.5 Hz, C-1), 43.3 (dd, 2J = 19.4 Hz, 2J = 15.1 Hz,

384
L.F. Lourie et al. / Journal of Fluorine Chemistry 127 (2006) 377–385
1
C-4), 52.1 (s, OCH3), 94.1 (d, J = 186.7 Hz, C-5), 96.5 (d,
1J = 198.4 Hz, C-7), 174.4 (s, C O); 19F NMR: d ꢁ166.2 (m,
publication no. CCDC-281173 (6b), CCDC-281172 (12),
CCDC-281235 (18), and CCDC-281236 (19). Copies of the
data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (Fax: +44 1223/336
033; E-mail: deposit@ccdc.cam.ac.uk).
2
F-5), ꢁ207.3 (dm, JF,7 = 55.2 Hz, F-7). Anal. Calcd for
C9H12F2O2: C, 56.83; H, 6.36. Found: C, 56.8; H, 6.3.
4.2.3. endo-3-Methoxycarbonyl-2,6-
norbornanecarbolactone (17)
White crystals, mp 83–84 8C (lit.: mp 85 8C [49]); 1H NMR: d
1.60–1.80 (3H, m, Hendo-5, Hexo-5, Hsyn-7), 2.23 (1H, dm, AB,
2J7anti,7syn = 14.4 Hz, Hanti-7), 2.66 (1H, m, H-4), 2.78 (1H, dd,
References
[1] Yu.I. Gevaza, V.I. Staninets, N.S. Zefirov, Electrofil’naya vnutrimolecu-
lyarnaya tsiklizatsiya olefinov (Elecrofilic Intramolecular Cyclization of
Olefins), Naukova Dumka, Kiev, 1990, p. 156, (in Russian).
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Org. Khim. 36 (2000) 218–225 (Russ. J. Org. Chem. 36 (2000) 195–
199).
3
3
3J2,3 = 10.8 Hz, J2,1 = 4.5 Hz, H-2), 3.02 (1H, dm, J3,2
=
3
10.8 Hz, H-3), 3.30 (1H, tm, J1,2 = 3J1,6 = 4.8 Hz, H-1), 3.72
(3H, s, CH3), 4.82 (1H, dd, 3J6,5exo = 7.8 Hz, 3J6,1 = 4.5 Hz, H-6).
[3] N.S. Pirkuliev, V.K. Brel, N.G. Akhmedov, N.S. Zefirov, Zh. Org. Khim.
37 (2001) 1052–1057 (Russ. J. Org. Chem. 37 (2001) 1001–1006).
[4] D.H.R. Barton, L.S. Godinho, R.H. Hesse, M.M. Pechet, Chem. Commun.
(1968) 804–806.
4.2.4. Dimethyl exo-5,anti-7-difluoro-cis-norbornane-exo-
2,3-dicarboxylate (18)
1
Colourless crystals, mp 95 8C; H NMR: d 1.98 (1H, m,
3
2J6endo,6exo = 14.1 Hz, J6endo,F = 14 Hz, 3J6endo,5 = 6.9 Hz,
[5] M. Okada, Y. Nakamura, H. Horikawa, T. Inoue, T. Taguchi, J. Fluorine
Chem. 82 (1997) 157–161.
3
2
Hendo-6), 2.29 (1H, ddm, J6exo,F = 35.1 Hz, J6exo,6endo
=
14.1 Hz, Hexo-6), 2.56 (1H, dd, AB, J2,3 = 10.8 Hz,
4JH,F = 4.8 Hz, H-2 or H-3), 2.63 (1H, dd, AB,
3
[6] M. Sawaguchi, S. Hara, T. Fukuhara, N. Yoneda, J. Fluorine Chem. 104
(2000) 277–280.
[7] Yu.A. Serguchev, L.F. Lourie, G.V. Polishchuk, A.N. Chernega, Mende-
leev Commun. (2002) 115–117.
3J2,3 = 10.8 Hz, JH,F = 4.8 Hz, H-2 or H-3), 2.74 (1H, m, H-
4
1), 2.89 (1H, dm, 3J4,F = 9.6 Hz, H-4), 3.66 (3H, s, OCH3), 3.67
[8] Yu.A. Serguchev, L.F. Lourie, G.V. Shevchenko, A.N. Chernega, J. Org.
Pharm. Chem. 3 (2005) 28–31 (Russian).
2
(3H, s, OCH3), 4.76 (1H, ddm, J5,F = 54.9 Hz, J5,6endo
3
=
6.9 Hz, H-5), 5.51 (1H, dm, 2J7,F = 54.3 Hz, H-7); 13C NMR: d
36.2 (d, 2J = 21.4 Hz, C-6), 41.2 (dd, 3J = 9.6 Hz, 3J = 8.6 Hz,
[9] M. Albert, K. Dax, J. Ortner, Tetrahedron 54 (1998) 4839–4848.
[10] S.P. Vincent, M.D. Burkart, C.-Y. Tsai, Z. Zhang, C.-H. Wong, J. Org.
Chem. 64 (1999) 5264–5279.
ˇ
[11] M. Zupan, P. Sculj, S. Stavber, Tetrahedron 57 (2001) 10027–10031.
ˇ ˇ
[12] M. Zupan, A. Gregorcic, A. Pollak, J. Org. Chem. 42 (1977) 1562–
2
3
C-3), 41.3 (d, J = 18.3 Hz, C-1), 45.4 (d, J = 6.5 Hz, C-2),
46.1 (dd, 2J = 21.5 Hz, 2J = 16.0 Hz, C-4), 52.2 (s, OCH3), 52.4
(s, OCH3), 93.5 (d, 1J = 190.5 Hz, C-7 or C-5), 95.7 (d,
1J = 197.7 Hz, C-5 or C-7), 171.3 (s, C O), 171.9 (s, C O); 19
1566.
ˇ ˇ
[13] A. Gregorcic, M. Zupan, Bull. Chem. Soc. Jpn. 53 (1980) 1085–1088.
F
2
[14] S.A. Shackelford, J. Org. Chem. 44 (1979) 3485–3492.
[15] D.F. Shellhamer, C.M. Curtis, R.H. Dunham, D.R. Hollingsworth,
M.L. Ragains, R.E. Richardson, V.L. Heasley, J. Org. Chem. 50 (1985)
2751–2758.
NMR: d ꢁ166.7 (m, F-5), ꢁ208.6 (dm, JF,7 = 53.9 Hz, F-7).
Anal. Calcd for C11H14F2O4: C, 53.22; H, 5.68. Found: C, 53.1;
H, 5.6.
[16] M.L. Druelinger, D.F. Shellhamer, R.D. Chapman, S.A. Shackelford, M.E.
Riner, S.L. Carter, R.P. Callahan, C.R. Youngstrom, J. Chem. Soc., Perkin
Trans. 2 (1997) 787–794.
4.2.5. Dimethyl endo-5,anti-7-difluoro-cis-norbornane-
exo-2,3-dicarboxylate (19)
[17] R.A. Hildreth, M.L. Druelinger, S.A. Shackelford, Tetrahedron Lett. 23
(1982) 1059–1062.
1
Colourless crystals, mp 54.5–55 8C; H NMR: d 1.46 (1H,
3
2
ddm, J6endo,F = 28.2 Hz, J6endo,6exo = 14.1 Hz, Hendo-6), 2.48
[18] A.G. Gilicinski, G.P. Pez, R.G. Syvret, G.S. Lal, J. Fluorine Chem. 59
(1992) 157–162.
(1H, m, Hexo-6), 2.59 (1H, m, H-1), 2.94 (1H, m, H-4), 2.97
3
(1H, dd, J2,3 = 11.7 Hz, J2,F = 4.8 Hz, H-2), 3.41 (1H, dd,
4
[19] R.E. Banks, (Air Products and Chemicals Inc., USA), US Patent
5,086,178, 1992, p. 9.
3J3,2 = 11.7 Hz, J3,F = 4.8 Hz, H-3), 3.67 (6H, s, 2CH3), 5.40
4
[20] J.J. Hart, R.G. Syvret, J. Fluorine Chem. 100 (1999) 157–161.
[21] S.D. Taylor, C.C. Kotoris, G. Hum, Tetrahedron 55 (1999) 12431–12477.
[22] J.-A. Ma, D. Cahard, Chem. Rev. 104 (2004) 6119–6146.
[23] R.P. Singh, J.M. Shreeve, Acc. Chem. Res. 37 (2004) 31–44.
[24] P.T. Nyffeler, S.G. Duron, M.D. Burkart, S.P. Vincent, C.-H. Wong,
Angew. Chem. Int. Ed. 44 (2005) 192–212.
(1H, dm, 2J5,F = 55.8 Hz, H-5), 5.55 (1H, dm, 2J7,F = 55.2 Hz,
H-7); 13C NMR: d 33.7 (d, 2J = 23.0 Hz, C-6), 37.3 (dd,
3J = 12.1 Hz, J = 7.7 Hz, C-3), 41.5 (d, J = 19.4 Hz, C-1),
3
2
2
45.5 (t, J = 15.8 Hz, C-4), 46.5 (d, J = 6.6 Hz, C-2), 52.2 (s,
3
1
1
2OCH3), 91.5 (d, J = 184.5 Hz, C-5), 97.9 (d, J = 194.5 Hz,
C-7), 172.3 (s, C O), 172.4 (s, C O); 19F NMR: d ꢁ199.5
(ddd, 2JF,5 = 55.2 Hz, 3JF,6endo = 28.8 Hz, 3JF,6exo = 16.6 Hz, F-
[25] F. Sladky, in: V. Gutman (Ed.), Noble Gases. Main Group Elements Group
VII and Noble Gases, Butterworth, 1973.
[26] J.D. Roberts, E.R. Trumbull Jr., W. Bennett, R. Armstrong, J. Am. Chem.
Soc. 72 (1950) 3116–3124.
2
5), ꢁ208.6 (d, JF,7 = 55.3 Hz, F-7). Anal. Calcd for
[27] S.A. Lermontov, S.I. Zavorin, I.V. Bakhtin, A.N. Pushin, N.S. Zefirov, P.J.
Stang, J. Fluorine Chem. 87 (1998) 75–83.
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