Preparations of SF5- and CF3-substituted arenes utilizing the 7-oxabicyclo[2.2.1]hept-2-ene synthones

Article abstract of DOI:10.1039/c3ob41560k

The synthesis of SF₅- and CF₃-substituted benzenes and naphthalenes from various 7-oxanorbornene derivatives utilizing SF ₅Cl and CF₃I radical addition reactions, followed by dehydrohalogenation and aromatizatio

Full text of DOI:10.1039/c3ob41560k

Organic &
Biomolecular Chemistry
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Preparations of SF5- and CF3-substituted arenes
utilizing the 7-oxabicyclo[2.2.1]hept-2-ene synthones†
Cite this: Org. Biomol. Chem., 2013, 11,
8103
Maxim V. Ponomarenko,*a Katrin Lummer,a Andrey A. Fokin,b Yurii A. Serguchev,c
Bassem S. Bassila and Gerd-Volker Röschenthalera
The synthesis of SF5- and CF3-substituted benzenes and naphthalenes from various 7-oxanorbornene
derivatives utilizing SF5Cl and CF3I radical addition reactions, followed by dehydrohalogenation and aro-
matization, is reported. The differences in the behavior of the SF5- and CF3-containing intermediates
under basic and acidic conditions are discussed. The experimentally observed high regioselectivities of
the formation of 2-RF-substituted-1-naphthols agree well with the ab initio computations, revealing the
first example of the SF5⋯HO hydrogen bonding.
Received 30th July 2013,
Accepted 10th October 2013
DOI: 10.1039/c3ob41560k
www.rsc.org/obc
multiple bonds (cyclohexenes, acetylene, and sulfolene), fol-
lowed by the conversion of the corresponding adducts.9
Introduction
Recent discoveries of CF3-substituted aromatics among bio-
The ring-opening reactions of the 7-oxabicyclo[2.2.1]hept-2-
logically active compounds have stimulated the development ene (7-oxanorbornene) derivatives involving the cleavage of the
of new approaches towards the synthesis of trifluoromethy- oxygen bridge10 are useful for the preparations of functiona-
lated arenes.1 The advantages of the arenes containing penta- lized cyclohexene derivatives,11 and arenes,12 as well as various
fluoro-λ6-sulfanyl substituent (SF5),2 which was recently natural products and their analogues.13 However, to the best of
labeled a “super CF3 function”,2d,g attract substantial interest our knowledge, the additions14 to 7-oxanorbornene have never
with respect to their potential as materials,2d,g,3 pharmaceuti- been applied for the preparation of perfluoro-arene derivatives.
cals,2a,4 and agrochemicals.2b However, the number of SF5-con- The only example includes the preparation of 3-pentafluoro-λ6-
taining compounds is limited by poor availability of the SF5 sulfanyl furanes from the adducts of SF5Cl with 5-cyano-7-
sources or building blocks.
oxanorbornenes.15
Several approaches towards the preparation of pentafluoro-
Alternatively, 2-pentafluoro-λ6-sulfanyl naphthalene was
λ6-sulfanyl benzenes have been developed. The most common obtained in three steps through the addition of SF5Cl to benzo-
are based on the fluorination of diaryl disulfides or aryl thiols barralene followed by dehydrochlorination and elimination of
with AgF2 or XeF2,5 F2,6 or with excess of chlorine and potass- the ethylene bridge via a sequence of cycloadditions and retro-
ium fluoride resulting in the formation of [chloro(tetrafluoro)- cycloadditions.16
λ6-sulfanyl]aryles. The latter were converted to the SF5-contain-
ing products in good yields utilizing zinc fluoride, HF-pyridine
complex, excess of anhydrous hydrofluoric acid, or SbF5.7 The
Results and discussion
functionalizations of the obtained SF5-aromatics were inten-
sively explored recently.6b,8 The alternative synthetic approach
Herein we present the synthesis of SF5- and CF3-benzenes and
naphthalenes from the readily available11e,17 7-oxanorbornene
is based on the radical additions of SF5X (X = Br, Cl) to
derivatives 1a–c utilizing the radical additions of SF5Cl18 and
CF3I,19 respectively. The selective exo-addition of the electro-
aSchool of Engineering and Science, Jacobs University Bremen gGmbH, Campus Ring
1, 28759 Bremen, Germany. E-mail: m.ponomarenko@jacobs-university.de;
Fax: +49 421 2003229; Tel: +49 421 2003651
bDepartment of Organic Chemistry, Kiev Polytechnic Institute, pr. Pobedy 37,
03056 Kiev, Ukraine
•
•
philic radicals SF5 and CF3 to the double bond and the pre-
dominant endo-abstractions of the halogens (Cl, I) lead to the
respective adducts 2a–c and 3a–c in good preparative yields
(Scheme 1). Minute amounts of exo/exo-addition products
(4a–c) were observed in the reaction of CF3I with 1a–c
(Scheme 1, Table 1, entries 4–6). The exo–endo stereospecificity
of the addition of SF5Cl is due to the steric demand of the SF5-
group.20 The stereochemistry of 2, 3 and 4c was proven by
1- and 2D NMR spectroscopy (see the ESI† for details). The
cInstitute of Organic Chemistry, NAS of Ukraine, 5 Murmanskaya Str., 02094 Kiev,
Ukraine
†Electronic supplementary information (ESI) available: Copies of 1H, 13C, 19F
NMR, and 2D spectra of synthesized products, X-ray structures of 8, 10a, 14c.
CCDC 951078–951080. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c3ob41560k
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Scheme 1 The radical additions to 7-oxanorbornenes 1a–c with further dehydrohalogenations.
however, the reaction rates vary slightly for each stereoisomer.
We have found that the anti-elimination of HI from 4c is
ca. 2 times faster than that for the syn-elimination from 3c
(see the ESI† for details).
Table 1 The radical additions of SF5Cl and CF3I to 7-oxanorbornenes 1a–c
Isolated yield (%)
Starting
olefin
2, 3
(exo–endo)
4a–c
(exo–exo)
#
Reagent
Time (h)
The behavior of adducts 2b and 3b under the basic con-
ditions is determined by the presence of the endo-protons at
the α-position to the carboxylic groups. The treatment of 3b
with LiOH or K2CO3 in DMSO results in the aromatization to
1
2
3
4
5
6
1a
1b
1c
1a
1b
1c
SF5Cl
SF5Cl
SF5Cl
CF3I
CF3I
CF3I
10
18
10
40
48
40
84
79
96
90
—
—
—
∼1a
5a
1
7b (Scheme 2). When the reaction was monitored by H NMR
81
70 (84)a
5 (14)a
spectroscopy, the formation of an intermediate 8 was detected.
Under the ambient reaction conditions with DBU, the isomer
8 was isolated in 72% yield. The structure of 8 was confirmed
by X-ray crystal structure analysis (see the ESI†). We conclude
that the aromatization of 3b occurs via an initially formed carb-
anionic intermediate A, which undergoes the rearrangement
through a resonance-stabilized enolate B, to give the more
thermodynamically stable exo,endo-dimethylcarboxylate 8 as
an intermediate.
a Determined by 19F NMR.
reaction of SF5Cl with the Diels–Alder adduct of furan and
maleic anhydride (not shown) gave only a 56% yield of the
desired radical addition product, which was converted to 2b
(90% yield) by refluxing in methanol with catalytic amounts of
sulfuric acid.
Dehydrohalogenations of 2a, c and 3a, c with LiOH (5 eq.)
in DMSO occurred with high selectivity, providing olefins 5a, c
and 6a, c, respectively (Scheme 1). The mixture of the stereo-
isomers 3c and 4c can be used for the elimination step;
According to the literature data,21 the subsequent base-
induced endo- and exo-α-deprotonations of 7-oxabicyclo[2.2.1]-
heptane-2 carboxylates are viable. As a result of the latter, and
HI elimination, the further aromatization of 8 to 7b may
proceed through either intermediate C or D. Thus, the
Scheme 2 Base-catalyzed transformations of 2b and 3b.
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Scheme 3 The preparation of RF-naphthols 10–11a by the acid-catalyzed ring-opening.
Fig. 1 The MP2/cc-pVDZ (kcal mol−1) relative energies of the cations formed after the proton-induced ring-openings of 5a and 6a.
treatment of 8 with K2CO3 in DMSO leads to the aromatic destabilize the cationic intermediates of type F and H. Impor-
product 7b in good yield (Scheme 2). tantly, the cations E and G are additionally stabilized by the
The presence of SF5-group in adduct 2b changed the reac- intramolecular F⋯HO hydrogen bonding.
tion course dramatically as we isolated only a nortricyclic com-
It is known that the CF⋯HO hydrogen bonding can influ-
pound 9 after the treatment with DBU in CH2Cl2, and LiOH or ence the properties of fluorine containing organic com-
K2CO3 in DMSO (Scheme 2). The formation of 9 is likely pounds.25 However, due to the poor polarizability of the C–F
to occur via the α-endo-deprotonation to anion E, which bond in organic fluorides the weak hydrogen bonding26
undergoes cyclization accompanied by the γ-elimination of enhances only selected molecular structures and conforma-
the SF5-anion, which is the better leaving group than the tions.25b,27 To the best of our knowledge, there is no indication
CF3-anion.22
for intramolecular F⋯HO interactions in the organic com-
In order to isomerize 5a and 6a into the corresponding aro- pounds bearing the SF5-group. It has been shown that rotation
matic products, we tested several acid-promoted ring-opening around the SF5C–COH bond of saturated alcohols is controlled
reactions. The isomerization of the SF5-containing 7-oxanor- by the SF5-substituent,28 but this influence was attributed to
bornene derivative 5a proceeds slowly, giving only one regio- the stereoelectronic effects, rather than to the SF⋯HO
isomer of the SF5-substituted 2-pentafluoro-λ6-sulfanyl-1- bonding, which was estimated as only 0.08 kcal mol−1 28b
.
1
naphthol (10a) in 64% yield after heating at 90 °C in metha-
To our surprise, in the H NMR spectra of 10a and 11a in
nol–HCl (Scheme 3). The ring-opening of 6a under similar con- CDCl3 we observed the distinct multiplets of the OH protons
ditions resulted in the formation of CF3-naphthol 11a, due to spin–spin coupling with SF5- and CF3-substituents,
together with the traces of 12 and 12′, which resulted from the correspondingly. The signal of the OH proton of 10a is
acidic hydrolysis6b,23 of the CF3-group.
observed as a quintet (5JHF = 4.9 Hz, 6.77 ppm) resulting from
The regiospecificities of the formation of 2-RF-substituted- the coupling on four equatorial fluorine atoms (Feq) of the SF5-
5
1-naphthols 10a and 11a in the acid-catalyzed ring-opening group. The exceptionally sharp quartet at 6.32 ppm with JHF
=
reactions of 5a and 6a are not obvious12d–f and cannot be 5.1 Hz was observed for the hydroxyl proton of 11a. This is in
explained by the participation of both rings in charge delocali- contrast to the ortho-CF3-substituted phenols and 2-naphthols
1
zation, but rather by electron-withdrawing properties of the that typically display the OH-proton singlets in their H NMR
perfluorinated substituents SF5 and CF3. We computed24 the spectra.29 The observed constants are too large for through
relative stabilities of the respective intermediates and found bond coupling and may be attributed to the through-space
that cations E and G are more stable than their counterparts F intramolecular interaction only. The multiplets of the
and H (Fig. 1). We conclude that the regioselectivities of the OH-protons of 10a and 11a disappeared in DMSO-d6 due to
ring-opening of 5a and 6a are determined by the electron- the formation of the strong OH⋯DMSO hydrogen bond where
withdrawing effect of the fluorine-containing substituents that the sharp singlets at 10–11 ppm were observed instead.
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Fig. 2 The MP2/cc-pVDZ optimized geometry of 10a (left, bond distances in Å) and experimental X-ray crystal structures of 10a and 14c.
In order to detect the SF⋯HO interactions in the solid broadening and red-shifting band of 1-naphthol caused by
state, we carried out an X-ray crystallographic study of 10a. intermolecular hydrogen bond in the crystal.
A block-like single crystal of 10a appropriate for the X-ray
Unlike 5a and 6a, compound 5c undergoes the acid-
analysis was grown from an n-hexane–CH2Cl2 solution. The induced ring-opening, followed by aromatization only under
crystal structure of 10a (Fig. 2) shows a typical SF5-group geo- harsh conditions that give a number of side products. Treat-
metry, which is similar to that previously reported for SF5- ment of 5c with a mixture of acetic and sulfuric acids (5/1) at
substituted aromatics,6b,30 as well as to the X-ray structure of 100 °C for 24 h is accompanied by tarring and only one
the product 14c (Fig. 2). The S–F bond lengths of 10a are SF5-containing aromatic product 13 was identified (Scheme 4).
approximately 1.58–1.60 Å, and 1.793(9) Å distance is observed In the reaction of 5c with hydrochloric acid (35% aq.) at 100 °C
for the C–S bond. The equatorial fluorine atoms are directed the starting compound was completely consumed in ca. 90 h,
slightly away from the naphthalene ring resulting in the value giving the main product 14c, which was isolated from the
of 86.5–87.8° for the F–S–F angles between the equatorial and complex reaction mixture in 56% yield (Scheme 4). The for-
axial fluorine atoms of the SF5-group. The equatorial fluorine mation of 14c likely occurs through a preliminary hydrolysis of
atoms are staggered to the relative naphthalene plane forming the CH3O-groups to the corresponding dialcohol 16 with
the Feq–S–C–C dihedral angles of 47–48°. Accordingly, the further cleavage of the C–O bond of the bicycle followed by the
hydrogen atom of the hydroxyl group is directed towards the dehydration. The hydrochlorination of the intermediate 16
SF5-group, and adjacent to the two equatorial fluorine yielded the product 15 (Scheme 4). Alternatively, the mono-
atoms within distances of 2.209 Å (OH⋯Feq4) and 2.128 Å chlorination of 5c and further intramolecular SN2 substitution
(OH⋯Feq5) forming the Feq⋯H–O angles of about 129.5°. Both also can give 14c. However, this is less probable under acidic
of these OH⋯Feq distances are much shorter than the sum of conditions.
the van der Waals radii of hydrogen and fluorine atoms
All our attempts to aromatize the CF3-substituted com-
pound 6c failed. For instance, the exposure of 6c with hydro-
(2.67 Å).31
4
5
The O⋯Feq distances (O⋯Feq = 2.802 Å; O⋯Feq = 2.727 Å) chloric or Lewis acids, such as BF3-etherate or TiCl4/Zn-system
in 10a are also shorter than the sum of the van der Waals radii in THF, at 80–100 °C led to full decomposition of the starting
of oxygen (1.52 Å) and fluorine atoms (1.47 Å).31 These dis- material. The corresponding reaction mixtures were only con-
tances are conclusive evidence of the SF⋯HO hydrogen taminated by CF3-containing, and unidentified aromatic pro-
bonding in 10a and are in perfect agreement with the MP2/ ducts. In the reaction with BF3-etherate only ethyl benzoate as
cc-pVDZ optimized geometry of 10a (Fig. 2). We have found an aromatic product was isolated in 4% yield. Refluxing in the
that the C–O rotamer of 10a with an opposite location of the mixture of trifluoroacetic and hydrochloric acids resulted
OH fragment is ca. 5.5 kcal mol−1 less stable.
in the formation of a tricyclic product 17 in high yield
ˉ
The compound 10a crystallizes in P1 space group with four (Scheme 4), clearly indicating that hydrolysis of the CH3O-
molecules occupying the unit cell (see the ESI†). In the solid group followed by the formation of the new cyclic ether pro-
state the molecules of 10a make couples, in which the mole- ceeds faster than the cleavage of C–O bond of the 7-oxanor-
cules are oriented to each other by the intermolecular inter- bornene cage. The addition of hydrochloric or sulfuric acids into
action of the SF5-group and the OH-group lying in almost the trifluoroacetic acid solution of 17 and long exposure under
parallel planes of the naphthol moieties. The distance between elevated temperature led to complicated reaction mixtures.
the nearest Feq atom of the SF5-group of one molecule and the
OH hydrogen of the other (2.56 Å) is close to the van der Waals
radii of hydrogen and fluorine atoms.
Conclusions
As additional evidence of the S–Feq⋯HO hydrogen bonding
in the solid state of 10a, the νOH was observed as a sharp band
We have found that the radical additions of SF5Cl and CF3I to
the double bond of 7-oxanorbornene is a useful tool for the
at 3633 cm−1 in the IR spectrum measured in KBr unlike the
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Scheme 4 The acid-catalyzed transformations of 5c and 6c.
introduction of SF5- and CF3-substituents. The products TMS or CCl3F as an internal standard. Column chromato-
obtained from further transformations of the adducts depend graphy was performed on Kieselgel Merck 60 (230–400 mesh).
on the functional groups present in the structures. The reac-
Single crystals were each mounted on a Hampton cryo-loop
tions of 2a, c and 3a, c with LiOH led to the formation of de- for indexing and intensity data collection at 173 K (compound
hydrohalogenation products 5a, c and 6a, c in good yields. 10a, CCDC 951079) and 100 K (compounds 8, CCDC 951078,
Subsequent treatment of 5a, c and 6a with Brønsted acids and 14c, CCDC 951080) using Mo Kα radiation (λ = 71.073
gives the products of aromatization 10a, 14c, and 11a, respecti- pm). Lorentz and polarization corrections were applied, and
vely. The behavior of the adducts of SF5Cl and CF3I and an absorption correction was performed using the SADABS
dimethyl 7-oxanorbornene-2,3-dicarboxylate (1b) under basic program.32 Direct methods were used for structure solution of
conditions is determined by the endo-protons at the α-position all structures (SHELXS-97). Structural refinement was obtained
to the carboxylic groups. We found dramatic differences in the from successive Fourier maps (SHELXL-97).33 All heavy atoms
reactions of SF5-product 2b and CF3-containing product 3b (C, O, F, I, and S) were refined anisotropically, and the hydro-
with bases. Reactions of 3b with LiOH or K2CO3 occur via the gen atoms were either found through calculated constrained
intermediate formation of the rearrangement product 8, which positions or directly. In order to prove the hydrogen bonding
undergoes the aromatization to 7b. The treatment of 2b with in 10a the OH-hydrogen atom was found directly and refined
bases (DBU, LiOH, and K2CO3) leads to the γ-elimination of isotropically.
the SF5-group giving the nortricyclic product 9.
Computations show that the high regioselectivities of the
formation of 2-RF-substituted-1-naphthols 10a and 11a in the
aromatization reactions are determined by the stability of
the intermediate carbocations formed after cleavage of the
C–O bond of the 7-oxanorbornane moiety. The products are
additionally stabilized by the intramolecular Ar–RF⋯HO
hydrogen bonding, which is shown for the first time for the
SF5⋯HO moiety by the example of 10a.
General procedure for SF5Cl addition to 1a–c
In a 3-necked flask equipped with a dry ice condenser and an
argon inlet 1a (1.0 g, 6.94 mmol) was dissolved in dry dichloro-
methane and cooled down to −40 °C. Then SF5Cl (2.25 g,
13.9 mmol, 2 equiv.) was condensed into the solution and
while stirring at −40 °C, Et3B (0.1 equiv., 1 M in hexane) was
added. The solution was stirred for 10–18 h and then warmed
to rt. The solvent was evaporated, the crude product was
diluted with 50 mL of CH2Cl2, washed with water (2 × 5 mL),
and dried under sodium sulfate. After evaporation of
the solvent the pure product 2a (1.79 g, 84%) was isolated by
filtration through SiO2 (CH2Cl2).
Experimental section
Compounds 1a–c were prepared according to literature proce-
endo-2-Chloro-exo-3-(pentafluoro-λ6-sulfanyl)-1,2,3,4-tetra-
dures.11e,17 All reagents from commercial suppliers were used hydro-1,4-epoxynaphthalene (2a). Yellow oil; 1H NMR
without further purification. 1H (399.78 or 200.13 MHz), 13C (400 MHz, CDCl3): δ 7.47–7.43 (m, 1H), 7.41–7.37 (m, 1H),
(100.53 or 50.32 MHz), and 19F (376.17 or 188.31) NMR spectra 7.35–7.30 (m, 2H), 5.89 (s, 1H, H4), 5.46 (d, J1,2 = 4.9 Hz, 1H,
3
were recorded on a Jeol ECX-400 and Bruker DPX-200 using H1), 5.01 (t, 3J2,1,3 = 4.9 Hz, 1H, H2), 3.86 (quin-d, 3J3,F = 6.4 Hz,
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3J3,2 = 4.5 Hz, 1H, H3); 13C NMR (101 MHz, CDCl3): δ 141.7 were dried over Na2SO4. After evaporation of the solvent the
(quin, 4J = 1.2 Hz, Ar), 141.2, 128.7, 128.3, 123.5, 119.7, 93.7 pure product 3a (2.6 g, 90%) was isolated by column chromato-
2
2
(quin-d, J = 10.6 Hz, 0.7 Hz, C3), 83.4 (quin, J = 4.7 Hz, C4), graphy (n-hexane–CH2Cl2 = 1/2).
82.3, 55.5 (quin, J = 4.0 Hz, C2); 19F NMR (376 MHz, CDCl3):
Endo-2-iodo-exo-3-(trifluoromethyl)-1,2,3,4-tetrahydro-1,4-
δ 83.8 (9 lines, A-part), 62.7 (dd, 2JF,F = 145.8 Hz, 3JF,H = 6.4 Hz, epoxynaphthalene (3a)
1
B4-part); Anal. Calcd for C10H8ClF5OS: C, 39.16; H, 2.63; Cl,
11.56. Found: C, 39.05; H, 2.61; Cl, 11.49.
White crystals, mp 64–65 °C; H NMR (400 MHz, CDCl3): δ
7.42 (d, 3J = 6.6 Hz, 1H), 7.39–7.26 (m, 3H), 5.47 (s, 1H, H4),
Dimethyl endo-5-chloro-exo-6-(pentafluoro-λ6-sulfanyl)-7- 5.39 (d, J1,2 = 4.4 Hz, 1H, H1), 4.21 (t, J2,1,3 = 4.6 Hz, 1H, H2),
3
3
oxabicyclo[2.2.1]heptane-exo,exo-2,3-dicarboxylate (2b). 1.39 g 2.48 (qd, J3,F = 8.7 Hz, J3,2 = 4.6 Hz, 1H, H3); 13C NMR
3
3
(79%); white crystals, mp 70–71 °C; 1H NMR (200 MHz, (101 MHz, CDCl3): δ 142.9, 142.7, 128.3, 127.2, 126.5 (q, 1J =
CDCl3): δ 5.40 (s, 1H, H1), 5.06 (d, J4,5 = 5.1 Hz, 1H, H4), 4.76 279.2 Hz, CF3), 123.5, 119.0, 83.3 (C1), 79.4 (q, J = 2.4 Hz, C4),
(t, 3J5,4,6 = 5.1 Hz, 1H, H5), 3.89 (m, 3J6,F = 5.7 Hz, 3J6,5 = 5.1 Hz, 56.1 (q, 2J = 27.8 Hz, C3), 13.6 (q, 3J = 1.2 Hz, C2); 19F NMR
1H, H6), 3.76 (d, 3J2,3 = 9.6 Hz, 1H, H2 or 3), 3.74 (s, 3H), 3.73 (s, (376 MHz, CDCl3): δ −68.52 (d, 3J = 8.7 Hz); Anal. Calcd for
3
3
3H), 3.17 (d, J2,3 = 9.6 Hz, 1H, H2 or 3); 13C NMR (50 MHz, C11H8F3IO: C, 38.85; H, 2.37; I, 37.32. Found: C, 38.70; H, 2.36;
3
CDCl3): δ 170.4, 169.8, 93.4 (quin, 2J = 12.6 Hz, C6), 83.2 (quin, I, 37.18.
3J = 4.4 Hz, C1), 81.9 (C4), 58.1 (quin, 3J = 3.9 Hz, C5), 53.1,
Dimethyl endo-5-iodo-exo-6-(trifluoromethyl)-7-oxabicyclo-
53.0, 51.4, 45.4; 19F NMR (188 MHz, CDCl3): δ 81.7 (9 lines, [2.2.1]heptane-exo,exo-2,3-dicarboxylate (3b). 2.81
(81%);
A-part), 59.4 (dm, J = 146.3 Hz, B4-part); HRMS (EI) for white crystals, mp 83–84 °C; 1H NMR (400 MHz, CDCl3): δ 4.92
g
[M − OCH3]+ (C9H9ClF5O4S): calcd 342.9830, found 342.9831; (d, J4,5 = 4.7 Hz, 1H, H4), 4.90 (s, 1H, H1), 4.00 (dd, J5,6 = 5.8
3
3
for [M − SF5]+ (C10H12ClO5): calcd 247.0373, found 247.0368.
Hz, J5,4 = 4.7 Hz, 1H, H5), 3.91 (d, J2,3 = 9.6 Hz, 1H), 3.71 (s,
3
3
3
endo-2-Chloro-exo,exo-5,6-bis(methoxymethyl)-exo-3-(penta- 3H, CH3), 3.70 (s, 3H, CH3), 3.05 (d, J2,3 = 9.6 Hz, 1H), 2.54
fluoro-λ6-sulfanyl)-7-oxa-bicyclo[2.2.1]heptane (2c). 1.81
g
(qd, J6,F = 8.3 Hz, J6,5 = 5.8 Hz, 1H, H6); 13C NMR (101 MHz,
3
3
(96%); white crystals, mp 51–52 °C; 1H NMR (400 MHz, CDCl3): δ 170.5, 169.8, 125.6 (q, J = 279.0 Hz, CF3), 82.3 (C4),
1
CDCl3): δ 4.96 (s, 1H, H4), 4.67 (t, J2,1,3 = 5.0 Hz, 1H, H2), 4.50 78.7 (q, J = 2.3 Hz, C1), 57.8 (q, J = 28.6 Hz, C6), 52.6, 52.6,
3
3
2
(d, J1,2 = 5.0 Hz, 1H, H1), 3.91 (m, J3,F = 5.9 Hz, 1H, H3), 51.5, 49.5, 15.2 (q, 3J = 1.9 Hz, C5); 19F NMR (376 MHz, CDCl3):
3.40–3.21 (m, 4H, 2CH2), 3.32 (s, 6H, 2CH3), 2.87 (td, J = 9.1,
−70.3 (d, 3J 8.3 Hz); HRMS (ESI) for [M + Na]+
6.2 Hz, 1H), 2.26 (m, J = 9.1, 5.0 Hz, 1H); 13C NMR (101 MHz, (C11H12F3INaO5): calcd 430.9574, found 430.9588.
3
3
δ
=
CDCl3): δ 94.5 (quin, J = 11.5 Hz, C3), 83.5 (quin, J = 5.2 Hz,
endo-2-Iodo-exo,exo-5,6-bis(methoxymethyl)-exo-3-(tri-fluoro-
(3c). 2.26 (70%),
2
3
C4), 82.3 (C1), 69.7 (CH2), 69.6 (CH2), 59.0 (OCH3), 58.9 methyl)-7-oxabicyclo[2.2.1]heptane
g
(OCH3), 58.6 (quin, 3J = 3.6 Hz, C2), 45.9, 38.1; 19F NMR n-hexane–CH2Cl2 = 1/5; white crystals, mp 41–42 °C; H NMR
(376 MHz, CDCl3): δ 83.5 (9 lines, A-part), 59.61 (dd, J = 145.7, (400 MHz, CDCl3): δ 4.44 (s, 1H, H4), 4.33 (d, 3J1,2 = 4.6 Hz, 1H,
1
5.9 Hz, B4-part); Anal. Calcd for C10H16ClF5O3S: C, 34.64; H, H1), 3.92 (dd, J2,3 = 5.8 Hz, J2,1 = 4.6 Hz, 1H, H2), 3.29 (s, 3H,
3
3
3
4.65; Cl, 10.22; S, 9.25. Found: C, 34.55; H 4.63; Cl, 10.16; S, CH3), 3.27 (s, 3H, CH3), 3.35–3.16 (m, 4H, 2CH2), 2.99 (td, J =
9.21.
9.0, 6.3 Hz, 1H), 2.51 (qd, 3J3,F = 8.7 Hz, 3J3,2 = 5.8 Hz, 1H, H3),
endo-5-Chloro-exo-6-(pentafluoro-λ6-sulfanyl)-7-oxabicyclo- 2.13 (m, J = 9.2, 5.3 Hz, 1H); 13C NMR (101 MHz, CDCl3):
1
3
[2.2.1]heptane-exo,exo-2,3-dicarbocyclic
acid
anhydride δ 126.2 (q, J = 278.9 Hz, CF3), 82.8 (C1), 79.2 (q, J = 2.2 Hz,
(2d). 1.11 g (56%); white crystals, mp 89–91 °C; 1H NMR C4), 70.2 (CH2), 69.5 (CH2), 58.9 (CH3), 58.7 (CH3), 57.8 (q, J =
2
(200 MHz, DMSO-d6): δ 5.46 (s, 1H, H1), 5.22 (d, J4,5 = 4.8 Hz, 27.9 Hz, C3), 46.0, 42.3, 17.3 (q, 3J = 1.3 Hz, C2); 19F NMR
3
1H, H4), 5.10–4.90 (m, 2H, H5,6), 4.14 (d, J2,3 = 7.5 Hz, 1H), (376 MHz, CDCl3): δ −70.32 (d, 3J = 8.7 Hz); HRMS (EI) for [M]+
3
3
3.78 (d, J2,3 = 7.4 Hz, 1H); 13C NMR (50 MHz, DMSO-d6): (C11H16F3IO3): calcd 380.0091, found 380.0097.
δ 172.2, 171.5, 93.3 (quin, 2J = 9.8 Hz), 83.4 (d, J = 4.3 Hz, C1),
exo-2-Iodo-exo,exo-5,6-bis(methoxymethyl)-exo-3-(tri-fluoro-
(4c). 0.16 (5%),
3
82.2 (C4), 59.2 (d, 3J = 4.3 Hz, C5), 50.6, 45.2; 19F NMR methyl)-7-oxabicyclo[2.2.1]heptane
g
(188 MHz, DMSO-d6): δ 85.2 (9 lines, A-part), 60.78 (dm, J = n-hexane–CH2Cl2
= 1/5; white crystals, mp 159–160 °C
151.5 Hz, B4-part); Anal. Calcd for C8H6ClF5O4S: C, 29.24; H, (sublime at >120 °C); 1H NMR (401 MHz, CDCl3): δ 4.70 (s, 1H,
3
1.84; Cl, 10.79. Found: C 29.15; H 1.83; Cl 10.68.
H1), 4.63 (s, 1H, H4), 4.10 (d, J = 8.3 Hz, 1H, H2), 3.31 (s, 6H,
2CH3), 3.38–3.11 (m, 4H), 2.61 (qd, 3J3,F = 8.7 Hz, 3J3,2 = 8.3 Hz,
1H, H3), 2.15 (m, 2H); 13C NMR (101 MHz, CDCl3): δ 124.2 (q,
General procedure for addition of CF3I to 1a–c
A pressure glass ampoule (150 mL) fitted with a magnetic stir- 1J = 279.2 Hz, CF3), 89.7 (C1), 79.9 (d, 3J = 2.1 Hz, C4), 70.0
ring bar was filled with a H2O–CH3CN solution (1 : 1, 40 mL), (CH2), 69.9 (CH2), 59.0 (2CH3), 52.0 (q, J = 27.6 Hz, C3), 45.9,
2
sodium dithionite (1.74 g, 8.5 mmol [85%]), Na3PO4·12H2O 45.5, 17.4 (d, 3J = 1.2 Hz, C2); 19F NMR (376 MHz, CDCl3): δ
(6.46 g, 17 mmol) and 1a (1.23 g, 8.5 mmol). The ampoule was −64.6 (bs); HRMS (EI) for [M]+ (C11H16F3IO3): calcd 380.0091,
cooled to −78 °C and evacuated, and then trifluoroiodo- found 380.0076.
methane (2.55 g, 13 mmol) was condensed in it. After
warming up to ambient temperature the mixture was stirred
Dehydrohalogenation of 2a, c, 3a, c and 4c
for 40–48 h, then water was added (50 mL), the mixture was 2c (0.20 g, 0.58 mmol) was dissolved in DMSO (5 mL) and 5
extracted with CH2Cl2 (4 × 15 mL), and the combined extracts equiv. of LiOH (0.069 g, 2.88 mmol) were added. The mixture
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was stirred for 24 h at 50 °C. Water (50 mL) was added and the mixture was extracted with dichloromethane (5 × 10 mL). After
mixture was extracted with dichloromethane (5 × 10 mL); the drying with sodium sulfate, the solvent was evaporated to
combined extracts were washed with water (3 × 10 mL). After obtain the crude product, which was purified by column
drying with sodium sulfate, the solvent was evaporated to chromatography (pentane–dichloromethane = 10/1) yielding
obtain the crude product, which was purified by filtration 7b (0.10 g, 78%) as a colourless liquid. 1H NMR (401 MHz,
through SiO2 (CH2Cl2) giving 5c (0.16 g, 92%).
CDCl3): δ 8.02 (s, 1H), 7.80 (d, J = 0.9 Hz, 2H), 3.93 (s, 6H); 13C
4
Exo,exo-5,6-Bis(methoxymethyl)-2-(pentafluoro-λ6-sulfanyl)-
NMR (101 MHz, CDCl3): δ 167.2, 166.4, 135.7 (q, J = 1.1 Hz),
2
3
7-oxabicyclo-[2.2.1]hept-2-ene (5c)
133.1 (q, J = 33.5 Hz, C4), 132.2, 129.4, 128.2 (q, J = 3.7 Hz),
1
3
1
White crystals, mp 38–39 °C; H NMR (401 MHz, CDCl3): δ 126.3 (q, J = 3.8 Hz), 123.2 (d, J = 272.8 Hz, CF3), 53.1, 53.1;
3
6.72 (m, J = 1.2 Hz, 1H, H3), 5.04 (d, J = 1.2 Hz, 1H, H4), 4.96 19F NMR (377 MHz, CDCl3): δ −63.04 (s).
4
2
(quin, J1,F = 1.2 Hz, 1H, H1), 3.51 (dd, JA,B = 9.0 Hz, 3J =
Dimethyl endo-5-iodo-exo-6-(trifluoromethyl)-7-oxabicyclo-
5.1 Hz, 1H, CH2), 3.44 (dd, 2JA,B = 9.2 Hz, 3J = 5.8 Hz, 1H, CH2), [2.2.1]heptane-endo-2-exo-3-dicarboxylate (8). 3b (0.10 g,
3.34 (s, 3H, OCH3), 3.33 (s, 3H, OCH3), 3.32–3.25 (m, 2H, CH2), 0.25 mmol) was dissolved in dichloromethane (2 mL), and
3
3
2.25 (td, J = 9.1, 5.8 Hz, 1H), 2.07 (ddd, J = 10.2, 8.5, 5.1 Hz, 1.2 eq. of DBU (0.046 g, 0.30 mmol) were added at 0 °C. The
1H); 13C NMR (101 MHz, CDCl3): δ 160.2 (quind, J2,Feq
=
reaction mixture was stirred for 12 h at rt. The reaction
2
2
2
18.7 Hz, J2,Fax = 2.0 Hz, C2), 137.0 (quin, J = 6.1 Hz, C3), 81.6 mixture was diluted with dichloromethane (5 mL) and washed
(quin, 3J = 3.4 Hz, C1), 81.4 (C4), 71.0 (OCH3), 71.0 (OCH3), 59.0 with water (3 × 3 mL). After drying with sodium sulfate the
(OCH2), 58.8 (OCH2), 39.8 (C5,6); 19F NMR (376 MHz, CDCl3): δ solvent was evaporated to obtain the crude product, which was
82.32 (9 lines, A-part), 66.57 (d, J = 152.1 Hz, B4-part); Anal. purified by filtration through silica gel giving 8 (0.072 g, 72%).
Calcd for C10H15F5O3S: C, 38.71; H, 4.87. Found: C, 38.59; H, White crystals, mp 68–71 °C; 1H NMR (400 MHz, CDCl3): δ
3
3
4.85.
4.86 (d, J1,2 = 5.0 Hz, 1H, H1), 4.76 (d, J4,5 = 5.5 Hz, 1H, H4),
2-(Pentafluoro-λ6-sulfanyl)-1,4-dihydro-1,4-epoxynaphthalene 4.05 (dd, J = 6.2, 5.5 Hz, 1H, H5), 3.90 (d, J3,2 = 6.0 Hz, 1H,
3
3
(5a). 0.13 g (81%); yellow oil; 1H NMR (400 MHz, CDCl3): δ H3), 3.78 (s, 3H, CH3), 3.76 (s, 3H, CH3), 3.55 (dd, 3J = 6.0,
7.40 (m, 1H), 7.35–7.30 (m, 2H), 7.09 (m, 2H), 5.87 (s, 2H, 5.0 Hz, 1H, H2), 2.65 (qd, J6,F = 8.6 Hz, J6,5 = 6.0 Hz, 1H); 13C
3
3
H1,4); 13C NMR (101 MHz, CDCl3): δ 169.5 (quin, J = 19.6 Hz, NMR (101 MHz, CDCl3): δ 171.9, 169.6, 125.9 (q, J = 278.9 Hz,
2
1
C2), 146.6, 145.8, 143.9 (quin, J = 6.2 Hz), 126.4, 126.3, 121.5, CF3), 84.6, 78.3 (q, J = 2.3 Hz, C1), 53.6 (q, J = 28.8 Hz, C6),
3
3
2
121.4, 83.5 (m, J = 3.6 Hz, C1), 83.1 (C4); 19F NMR (376 MHz, 53.0, 52.9, 51.1, 48.2, 15.5 (d, 3J = 1.4 Hz, C5); 19F NMR
3
CDCl3): δ 81.86 (9 lines, A-part), 66.24 (d, J = 152.9 Hz, B4-part); (376 MHz, CDCl3): δ −70.3 (d, 3J = 8.5 Hz); HRMS (ESI) for
Anal. Calcd for C10H7F5OS: C, 44.45; H, 2.61. Found: C, 44.34; [M + Na]+ (C11H12F3INaO5): calcd 430.9574, found 430.9588.
H, 2.60.
Dimethyl 5-chloro-3-oxatricyclo[2.2.1.02,6]heptane-1,7-dicarb-
2-(Trifluoromethyl)-1,4-dihydro-1,4-epoxynaphthalene (6a). oxylate (9). 2b (0.10 g, 0.27 mmol) was dissolved in dichloro-
0.10 g (84%); colourless oil; 1H NMR (400 MHz, CDCl3): δ methane (2 mL), and then 2 equiv. of DBU (0.082 g,
7.42–7.34 (m, 2H), 7.32 (m, 1H), 7.11–7.01 (m, 2H), 5.85 (m, 0.54 mmol) were added at 0 °C. The reaction mixture was
1H, H1), 5.78 (s, 1H, H4); 13C NMR (101 MHz, CDCl3): δ 147.1, stirred for 12 h at rt. The reaction mixture was diluted with
3
146.8, 146.4 (q, J = 1.3 Hz), 146.0 (q, J3,F = 4.9 Hz, C3), 126.1, 10 mL of dichloromethane, and washed with water (3 × 2 mL).
126.0, 122.8 (q, 1J = 267.7 Hz, CF3), 121.2, 121.0, 83.1 (C4), 81.2 After drying with sodium sulfate the solvent was evaporated to
3
(q, J = 1.6 Hz, C1); 19F NMR (376 MHz, CDCl3): δ −64.82 (s); obtain the crude product, which was purified by filtration
Anal. Calcd for C11H7F3O: C, 62.27; H, 3.33. Found: C, 62.12; through silica gel (CH2Cl2) giving 9 (0.035 g, 53%). Colourless
1
H, 3.32.
oil; H NMR (400 MHz, CDCl3): δ 4.66 (d, J = 3.9 Hz, 1H, H2),
exo,exo-5,6-Bis(methoxymethyl)-2-(trifluoromethyl)-7-oxa- 4.34 (m, 1H, H4), 4.01 (t, J = 2.1 Hz, 1H, H5), 3.73 (s, 3H,
bicyclo[2.2.1]hept-2-ene (6c). 0.13 g (89%); colourless oil; 1H OCH3), 3.71 (s, 3H, OCH3), 3.67 (s, 1H, H7), 2.35 (m, 1H, H6);
NMR (400 MHz, CDCl3): δ 6.76 (m, J = 2.3 Hz, 1H, H3), 4.97 (s, 13C NMR (101 MHz, CDCl3): δ 169.8, 169.0, 78.0 (C4), 61.4 (C2),
1H, H1), 4.92 (m, 1H, H4), 3.51 (dd, JA,B = 8.9 Hz, J = 5.0 Hz, 59.3 (C5), 52.4 (OCH3), 52.29 (OCH3), 46.7 (C7), 29.8 (C1), 29.2
1
3
1H, CH2), 3.45 (dd, 1JA,B = 9.1 Hz, 3J = 5.7 Hz, 1H, CH2), 3.36 (s, (C6); HRMS (ESI) for [M
3H, OCH3), 3.35 (s, 3H, OCH3), 3.38–3.25 (m, 2H, CH2), 2.07 269.0187, found 269.0188.
+
Na]+ (C10H11ClNaO5): calcd
3
3
(ddd, J = 8.7 Hz, 5.7 Hz, 1H), 2.00 (ddd, J = 9.9 Hz, 8.7 Hz,
The preparation of RF-naphthols 10–11a. 5a (0.13 g,
5.0 Hz, 1H); 13C NMR (101 MHz, CDCl3): δ 139.1 (q, 2J = 0.48 mmol) was dissolved in a mixture of methanol and hydro-
35.4 Hz, C2), 138.8 (q, J = 4.8 Hz, C3), 122.0 (q, J = 267.9 Hz, chloric acid (37% aq.) (3/1 mL). The reaction mixture was
CF3), 81.6 (C4), 79.3 (q, 3J = 1.4 Hz, C1), 71.2 (OCH3), 71.1 stirred for 70 h at 90 °C. Water (20 mL) was added to the reac-
(OCH3), 58.9 (CH2), 58.8 (CH2), 40.0 (C5), 39.8 (q, J = 1.3 Hz, tion mixture and the mixture was extracted with dichloro-
C6); 19F NMR (376 MHz, CDCl3): δ −63.6 (s); HRMS (ESI) for methane (5 × 5 mL), and washed with water (3 × 3 mL). After
3
1
[M]+ (C11H15F3NaO3): calcd 275.0866, found 275.0867.
drying with sodium sulfate the solvent was evaporated.
Dimethyl 4-(trifluoromethyl)phthalate (7b).34 3b (0.20 g, The crude product was purified by column chromatography
0.49 mmol) was dissolved in DMSO (5 mL) and 5 equiv. of (n-hexane–CH2Cl2 = 10/1) yielding 10a (0.083 g, 64%).
K2CO3 (0.34 g, 2.45 mmol) were added. The mixture was
stirred for 12 h at 60 °C. 100 mL of water was added and the mp 69–71 °C; 1H NMR (401 MHz, CDCl3): δ 8.42 (d, 3J = 8.3 Hz,
2-(Pentafluoro-λ6-sulfanyl)-1-naphthol (10a). White crystals,
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3
3
2
3
1H), 7.79 (d, J = 7.9 Hz, 1H), 7.67–7.51 (m, 3H), 7.40 (d, J = 1H, H4), 3.10 (dd, JAB = 10.2 Hz, J = 6.1 Hz, 1H, CH2), 2.69
9.3 Hz, 1H), 6.77 (quin, J = 4.9 Hz, 1H, OH); 13C NMR (dd, JAB = 11.1 Hz, 3J = 8.0 Hz, 1H, CH2), 2.65–2.51 (m, 2H,
2
(101 MHz, CDCl3): δ 147.1 (quin, J = 2.1 Hz, C1), 135.9–134.8 CH2), 2.28 (t, J = 8.0 Hz, 1H), 1.86 (dd, J = 6.1, 1.6 Hz, 1H); 13C
3
(quin, 2J = 13.1 Hz, C2), 135.3, 129.2, 127.3, 126.7, 125.8, 124.0, NMR (101 MHz, C6D6): δ 156.9 (quin, J = 13.5 Hz, C2), 130.6
2
122.9 (quin, 3J = 5.0 Hz, C3), 120.1; 19F NMR (377 MHz, CDCl3): (quin, J = 5.4 Hz, C3), 74.8 (quin, J = 3.0 Hz, C1), 66.9 (CH2),
δ 86.6 (9 lines, A-part), 67.1 (dm, J = 148.8 Hz, B4-part); IR 56.3 (C4), 45.2, 43.3, 42.4 (CH2); 19F NMR (376 MHz, CDCl3): δ
(KBr) νmax 3633, 2964, 1633, 1581, 1503, 1461, 1412; HRMS 82.1 (9 lines, A-part), 59.1 (d, J = 150.2 Hz, B4-part); HRMS (CI)
(ESI) for [M − H]− (C10H6F5OS): calcd 269.0066, found for [M − OH]+ (C8H8Cl2F5S): calc. 300.9644, found 300.9646.
3
3
269.0065.
HRMS (CI) for [M − F]+ (C8H9Cl2F4S): calc. 298.9687, found
2-(Trifluoromethyl)-1-naphthol (11a). Pale yellow crystals, 298.9694.
1
mp 37–38 °C; 0.082 g (41%, from 0.20 g, 0.94 mmol of 6a); H
5-(Trifluoromethyl)-1,3,3a,4,7,7a-hexahydro-4,7-epoxy-2-benzo-
3
NMR (400 MHz, CDCl3): δ 8.34 (d, J = 7.9 Hz, 1H), 7.82 (dd, furan (17). 6c (0.15 g, 0.59 mmol) was dissolved in 5 mL of tri-
3J = 7.4 Hz, 4J = 1.3 Hz, 1H), 7.59 (m, 2H), 7.47 (m, 2H), 6.32 (q, fluoroacetic acid. The reaction mixture was refluxed 3 h. TFA
J = 5.1 Hz, 1H, OH); 13C NMR (101 MHz, CDCl3): δ 150.7 (q, was evaporated, the reaction mixture was dissolved in 10 mL of
1
3J = 2.5 Hz, C1), 136.2, 128.7, 127.7, 126.5, 125.5 (q, J = 272.0 CH2Cl2, and washed with water (2 × 2 mL). After drying with
3
Hz, CF3), 124.9, 122.9, 121.7 (q, J = 4.2 Hz, C3), 120.8, 109.1 sodium sulfate the solvent was evaporated. The crude product
(q, 2J = 29.1 Hz, C2); 19F NMR (377 MHz, CDCl3): δ −59.0 (d, J = was purified by filtration through silica gel (pentane–CH2Cl2 =
5.0 Hz); Anal. Calcd for C11H7F3O: C, 62.27; H, 3.33. Found: C, 1/1) giving 17 (0.093 g, 76%). Colourless oil; 1H NMR
3
3
62.08; H, 3.32.
(400 MHz, CDCl3): δ 6.81 (dq, J6,F = 4.3 Hz, J = 2.3 Hz, 1H,
The spectral data of methyl 4-hydroxy-2-naphthoate (12) H6), 4.89 (s, 1H), 4.87 (s, 1H), 3.94 (ddd, J = 9.3, 7.4, 3.2 Hz,
and 1-hydroxy-2-naphthoate (12′) correspond with the litera- 2H), 3.64 (ddd, J = 9.2, 4.8, 2.5 Hz, 2H), 2.61 (dtd, J = 26.6, 7.7,
ture data.35
4.9 Hz, 2H); 13C NMR (101 MHz, CDCl3): δ 140.8 (q, 2J =
4-(Pentafluoro-λ6-sulfanyl)benzyl acetate (13). 5c (0.1 g, 35.8 Hz, C5), 139.9 (q, J = 4.8 Hz, C6), 122.1 (q, J = 267.9 Hz,
0.32 mmol) was dissolved in a mixture of AcOH and H2SO4 CF3), 82.9, 80.6 (q, 3J = 1.3 Hz, C4), 70.9, 70.8, 47.7, 47.4 (q, 4J =
(98%) (5/1 mL). The reaction mixture was stirred for 24 h at 1.4 Hz); 19F NMR (376 MHz, CDCl3): δ −63.8 (m); Anal. Calc.
100 °C. Water (40 mL) was added to the reaction mixture and for C9H9F3O2: C, 52.43; H, 4.40. Found: C, 52.29; H, 4.38.
the mixture was extracted with dichloromethane (5 × 8 mL),
3
and washed with water (4 × 3 mL). After drying with sodium
sulfate the solvent was evaporated. The crude product was
purified by column chromatography (n-hexane–CH2Cl2 = 1/1)
Acknowledgements
yielding 13 (0.017 g, 19%, only ca. 82% of purity by NMR). Pale This work was supported by the Deutsche Forschungsge-
1
yellow oil: H NMR (400 MHz, CDCl3): δ 7.74 (dm, J = 8.3 Hz, meinschaft (436 UKR 113/99/0-1). AAF is grateful to the Univer-
2H), 7.44 (dm, J = 8.3 Hz, 2H), 5.14 (s, 2H, CH2), 2.12 (s, 3H, sity of Giessen (Germany) and the Institute of Applied System
CH3); 13C NMR (101 MHz, CDCl3): δ 170.7, 147.0 (m), 139.9, Analysis (Kiev, Ukraine) for computing facilities.
128.1, 126.3 (quin, J = 4.6 Hz), 64.9, 20.9; 19F NMR (376 MHz,
CDCl3): δ 84.30 (tt, J = 154.6, 147.4 Hz), 62.93 (d, J = 150.0 Hz).
5-(Pentafluoro-λ6-sulfanyl)-1,3-dihydro-2-benzofuran (14c).
3 mL of hydrochloric acid (37% aq.) and 5c (0.2 g, 0.64 mmol)
Notes and references
were mixed in a 10 mL flask. The reaction mixture was stirred
ca. 90 h at 100 °C. Water (40 mL) was added to the reaction
mixture and the mixture was extracted with dichloromethane
(5 × 8 mL), and washed with water (4 × 3 mL). After drying
with sodium sulfate the solvent was evaporated. The reaction
mixture was separated by column chromatography (CH2Cl2)
giving 14c (0.089 g, 56%) and 15 (0.012 g, 6%). 14c: white crys-
1 (a) J. Nie, H.-C. Guo, D. Cahard and J.-A. Ma, Chem. Rev.,
2010, 111, 455–529; (b) D. O’Hagan, J. Fluorine Chem., 2010,
131, 1071–1081; (c) O. A. Tomashenko and V. V. Grushin,
Chem. Rev., 2011, 111, 4475–4521; (d) S. Purser,
P. R. Moore, S. Swallow and V. Gouverneur, Chem. Soc. Rev.,
2008, 37, 320–330; (e) G. K. S. Prakash and S. Chacko, Curr.
Opin. Drug Discovery Dev., 2008, 11, 793–802;
(f) A. T. Parsons and S. L. Buchwald, Nature, 2011, 480,
184–185; (g) K. Müller, C. Faeh and F. Diederich, Science,
2007, 317, 1881–1886; (h) J.-A. Ma and D. Cahard, J. Fluor-
ine Chem., 2007, 128, 975–996.
2 (a) S. Altomonte and M. Zanda, J. Fluorine Chem., 2012,
143, 57–93; (b) P. J. Crowley, G. Mitchell, R. Salmon and
P. A. Worthington, Chimia, 2004, 58, 138–142;
(c) G. L. Gard, Chim. Oggi, 2009, 27, 10–13; (d) P. Kirsch and
G. V. Röschenthaler, in Current Fluoroorganic Chemistry –
New Synthetic Directions, Technologies, Materials, and Bio-
logical Applications, ed. V. A. Soloshonok, K. Mikami,
1
3
tals, mp 89–90 °C; H NMR (400 MHz, CDCl3): δ 7.67 (dd, J =
4
4
8.3 Hz, J = 1.8 Hz, 1H), 7.62 (d, J = 1.8 Hz, 1H), 7.31 (d, J =
8.3 Hz, 1H), 5.14 (s, 4H, CH2); 13C NMR (101 MHz, CDCl3):
δ 153.6 (qd, J5,Feq = 17.3 Hz, J5,Fax = 1.2 Hz), 142.9, 140.2,
2
2
3
3
125.4 (q, J = 4.7 Hz), 121.2, 119.1 (q, J = 4.6 Hz), 73.3, 73.2;
19F NMR (376 MHz, CDCl3): δ 84.8 (9 lines, A-part), 63.7 (d, J =
150.0 Hz, B4-part); Anal. Calc. for C8H7F5OS: C, 39.03; H, 2.87.
Found: C, 38.92; H, 2.86.
5,6-Bis(chloromethyl)-2-(pentafluoro-λ6-sulfanyl)-7-oxabicyclo-
[2.2.1]hept-2-ene (15). Pale yellow oil; 1H NMR (400 MHz,
C6D6): δ 5.86 (m, 1H, H3), 4.54 (d, J = 1.3 Hz, 1H, H1), 3.40 (m,
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