Reaction of chlorosulfonyl isocyanate with fluorosubstituted alkenes: Evidence of a concerted pathway

Article abstract of DOI:10.1021/jo101240s

Concerted reactions are indicated for the electrophilic addition of chlorosulfonyl isocyanate with monofluoroalkenes. A vinyl fluorine atom on an alkene raises the energy of a stepwise transition state more than the energy of the competing concerted pathw

Full text of DOI:10.1021/jo101240s

pubs.acs.org/joc
synthesize β-fluorolactams from CSI. Other methods to
Reaction of Chlorosulfonyl Isocyanate with
Fluorosubstituted Alkenes: Evidence of a Concerted
Pathway
prepare β-fluorolactams have been reported.5a,b
Reactions of CSI with hydrocarbon alkenes are reported to
proceed through an open-ion dipolar intermediate.1,3,6 Moriconi
suggests that some 1,2-disubsituted olefins retain stereo-
chemistry through fast collapse of the dipolar intermediate.3,6
Ab initio calculations show that [2 þ 2] cycloadditions between
alkenes and isocyanates can react via a concerted transition
state with zwitterionic character.7 These calculations also found
that electron-donating groups on the alkene or electron-
withdrawing groups on the isocyanate lower the activation
energy and induce the nature of the reaction to become less
synchronous.7 Calculations support a concerted process for
the cycloaddition of isocyanates with aldehydes.8 Quantum
chemical calculations and photoelectron spectral data show
that substituting a hydrogen with a fluorine atom on the π-bond
of an alkene does not significantly alter the molecular energy of
the π-bond,9 and therefore, the HOMO and LUMO orbital
energies for a concerted pathway should not be altered either.
On the other hand, the energy for a dipolar stepwise pathway is
raised significantly by the vinyl fluorine atom through its strong
inductive effect.10 This perturbation of the free energy profile is
described in Figure 1 where the fluorine atom raises the transi-
tion state energy significantly for the stepwise process but
increases the energy of the concerted pathway by only a modest
amount. In Figure 1 the solid line represents the energy profile
for hydrocarbon alkenes, and the dashed line describes the
pathway for monofluoroalkenes. Therefore, alkenes with a
vinyl fluorine atom may allow a concerted process to compete
with or completely dominate the stepwise pathway. Both con-
certed and stepwise pathways might be realized for reactions of
CSI with appropriately substituted fluoroalkenes.
Dale F. Shellhamer,*,† Kevyn J. Davenport,†
Danielle M. Hassler,† Kelli R. Hickle,† Jacob J. Thorpe,†
David J. Vandenbroek,† Victor L. Heasley,† Jerry A. Boatz,‡
Arnold L. Reingold,§ and Curtis E. Moore§
†Department of Chemistry, Point Loma Nazarene University,
San Diego, California 92106-2899, United States, ‡Air Force
Research Laboratory, Edwards Air Force Base, California
93524-7680, United States, and §Department of Chemistry
and Biochemistry, University of California, 9500 Gilman
Drive, La Jolla, California 92093-0358, United States
dshellha@pointloma.edu
Received June 30, 2010
Concerted reactions are indicated for the electrophilic
addition of chlorosulfonyl isocyanate with monofluoro-
alkenes. A vinyl fluorine atom on an alkene raises the
energy of a stepwise transition state more than the energy
of the competing concerted pathway. This energy shift
induces CSI to react with monofluoroalkenes by a one-
step process. The low reactivity of CSI with monofluoro-
alkenes, stereospecific reactions, the absence of 2:1 uracil
products with neat fluoroalkenes, and quantum chemical
calculations support a concerted pathway.
Chlorosulfonyl isocyanate (CSI) is the most reactive and
versatile isocyanate.1 CSI reacts with alkenes to give chloro-
sulfonyl β-lactams that are readily reduced to β-lactams.2,3
This reaction sequence provides a synthetic route to β-lactam
antibiotics.4 We demonstrate in this paper a method to
FIGURE 1. Free energy diagram for reaction of CSI with hydro-
carbon alkenes and fluorocarbon alkenes. Concerted reactions to
the left and stepwise reactions to the right.
(1) (a) Dhar, D. N.; Murthy, K. S. K. Synthesis 1986, 437. (b) Szabo,
W. A. Aldrichimica Acta 1977, 10, 23. Rasmussen, J. K.; Hassner, A. Chem.
Rev. 1976, 76, 389. Aue, D. H.; Iwahashi, H.; Shellhamer, D. F. Tetrahedron
Lett. 1973, 3719. Graf, R. Angew. Chem.., Int. Ed. Engl. 1968, 7, 172.
(2) (a) Hollywood, F.; Suschitzky, H.; Hull, R. Synthesis 1982, 662–665.
(b) Durst, T.; O’Sullivan, M. J. J. Org. Chem. 1970, 35, 2043.
(3) Moriconi, E. J.; Crawford, W. C. J. Org. Chem. 1968, 33, 370.
(4) Chemistry and Biology of beta-Lactam Antibiotics; Marin, R. B.,
Gorman, M., Eds.; Academic Press: New York, 1982; Vols. 1-3. Recent
Progress in the Chemical Synthesis of Antibiotics; Lucas, G., Ohno, M., Eds.;
Springer-Verlag: Berlin, 1990; pp 562-612.
(5) (a) Welch, J. T.; Koechi, A.; Kawecki, R.; Wichtowski, J. A. J. Org.
Chem. 1993, 58, 2454. (b) Lopez, R.; Ruiz-Lopez, M. F.; Rinaldi, D.; Sordo,
J. A.; Sordo, T. L. J. Phys. Chem. 1996, 100, 10600.
(6) Moriconi, E. J.; Meyer, W. C. J. Org. Chem. 1971, 36, 2841. Moriconi,
E. J.; Jalandoni, C. C. J. Org. Chem. 1970, 35, 3796.
(7) Cossio, F. P.; Roa, G.; Lecea, B.; Ugalde, J. M. J. Am. Chem. Soc.
1995, 117, 12306.
(8) Fang, De-Cai; Fu, X. Y. J. Mol. Struc. (Theochem) 1999, 459, 15.
(9) Brundle, C. R.; Robin, M. B.; Kuebler, N. A. J. Am. Chem. Soc. 1972,
94, 1451.
(10) Krespan, C. G.; Petrov, V. A. Chem. Rev. 1996, 96, 3269. Polishchuck,
V. R.; Mysov, E. I.; Stankevich, I. V.; Chistadov, A. L.; Potechin, K. A.
J. Fluorine Chem. 1993, 65, 233.
DOI: 10.1021/jo101240s
r
Published on Web 10/21/2010
J. Org. Chem. 2010, 75, 7913–7916 7913
2010 American Chemical Society

Shellhamer et al.
JOCNote
CSI is a sluggish electrophile and reacts poorly in solution
with alkenes that contain an electron-withdrawing vinyl
fluorine.11 We found that neat reactions of CSI with these
less reactive fluoroalkenes proceed smoothly and in good
yield. Neat reactions of CSI with these monofluoroalkenes
allow for the synthesis of β-fluorolactams under “green
chemistry” conditions. Thus, dialkylsubstituted monofluoro-
alkenes like the 1-fluorocyclohexenes (1, 2), 3-fluorohex-3-
enes 3E and 3Z, and the trialkylsubstituted fluorocyclohexene
(4) react with CSI to give chlorosulfonyl β-fluorolactams
(Scheme 1). A stereospecific reaction of CSI with 3E and
3Z is consistent with a concerted process for this series
of fluoroalkenes. Product regiochemistry was confirmed by
the carbonyl 13C NMR three bond coupling with fluorine
(JC-F = 3-6 Hz). The nitrogen of the β-lactams is bonded to
the carbon with the fluorine since the developing positive
charge in the concerted transition state prefers to be on the
carbon stabilized by back-bond resonance from fluorine.
The regiochemistry of the β-sulfonyl fluorolactam pro-
ducts did not change when a third alkyl group was incorpo-
rated as in fluoroalkene 4. β-Lactam products (10 cis and 10
trans) show a 3 Hz coupling typical for three bond fluorine to
carbonyl splitting. Assignment of the carbons from 10 cis
and 10 trans was based on the magnitude of the carbon-
fluorine coupling and from DEPT and HSQC experi-
ments. The cis/trans stereochemistry of 10 was assigned using
a 1-dimension ROESY experiment. Irradiating the upfield
methyl adjacent to the carbonyl of the major isomer
enhanced the methyl on the methine carbon. Irradiating
the upfield methyl of the minor isomer enhanced the methine
hydrogen on the minor isomer. Irradiating the methine
hydrogens of each isomer separately confirmed the experi-
ments irradiating the methyl groups above.
SCHEME 1. Reaction of Alkenes with CSI
The best conditions to obtain β-sulfonyl fluorolactams
(11 and 12) were with fluoroalkenes 5 and 6 and CSI in
methylene chloride at room temperature (Scheme 1). Pro-
duct 11, as a neat liquid, decomposes in 1-2 days at room
temperature but is stable in solution for about 1 week.
Product 6 is a crystalline solid that decomposes in less than
15 min at room temperature but is stable in solution for 1
day. Reactions at high molar concentrations of 5 or 6 with
CSI, approaching the neat concentrations used for fluoro-
alkenes 1, 2, 3E, 3Z, and 4, did not give uracil products 13.
At these high concentrations we would expect capture of
a dipolar intermediate by a second molecule of CSI to give
uracil products like those reported for the reaction of CSI
with hydrocarbon alkenes that can support stable dipolar
intermediates.1a,2a,12 Thus we suggest that fluoroalkenes
1-6 react by a concerted pathway.
Figure 1. Transition states for the concerted pathway and
a portion of a stepwise pathway were calculated for reaction
of CSI with vinyl fluoride (Supporting Information). Intrin-
sic reaction coordinate calculations were performed to trace
the minimum energy paths connecting the transition states
to the corresponding local minima, i.e., reactants and prod-
ucts. The calculated stepwise transition state that connects
to a high energy intermediate is 56.9 kcal/mol above the
separated reactants (Supporting Information, structures
1 and 2 and Table S1). This stepwise transition state was
found to be 26.6 kcal/mol higher in energy than the concerted
transition state. Furthermore, the calculated stepwise transi-
tion state and intermediate have the nitrogen interacting with
the fluorine-bearing carbon of vinyl fluoride, and that inter-
mediate was also higher in energy than the concerted transi-
tion state (Supporting Information, Tables S1 and S2).
The stepwise pathway does not include the expected inter-
mediate with the carbonyl carbon of CSI attached to the
terminal carbon of vinyl fluoride. All attempts to locate that
Quantum chemical calculations at the MP2/6-311G(d,p)
level of theory13a-e,14 also support our claim of a one-step
process for reaction of CSI with fluoroalkenes as described in
(11) Presented in part at the 19th Winter Fluorine Conference at St.
Petersburg Beach, FL on January 16, 2009.
(12) Paquette, L. A.; Broadhurst, M. J. J. Org. Chem. 1973, 38, 1893.
Hoffmann, R. W.; Becherer, J. Tetrahedron 1978, 34, 1187.
(13) (a) Møller, C.; Plesset, M. S. Phys. Rev. 1934, 46, 618. (b) Pople, J. A.;
Binkley, J. S.; Seeger, R. Int. J. Quantum Chem. 1976, S10, 1. (c) Frisch, M. J.;
Head-Gordon, M. J.; Pople, A. Chem. Phys. Lett. 1990, 166, 275. (d) Bartlett,
R. J.; Silver, D. M. Int. J. Quantum Chem. 1975, S9, 183. (e) Aikens, C. M.;
Webb, S. P.; Bell, R.; Fletcher, G. D.; Schmidt, M. W.; Gordon, M. S. Theor.
Chem. Acc. 2003, 110, 233.
(14) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem. Phys.
1980, 72, 650.
7914 J. Org. Chem. Vol. 75, No. 22, 2010

Shellhamer et al.
JOCNote
ice-water. The organic layer was separated, and the aqueous
layer was extracted with methylene chloride. The combined
organic extractions were washed with 2% aqueous sodium
bicarbonate, dried over anhyd magnesium sulfate, and concen-
trated. 19F NMR analysis on the crude mixture showed 8 cis/
trans to be formed in a ratio of 1.0/3.0, respectively. Column
chromatography (10 g silica gel) of the crude mixture with
hexanes/chloroform gave 194 mg, 65%, of pure 8 cis/8 trans in
1
a ratio of 1.0/2.6 respectively. 8 trans/cis: H NMR 400 MHz
(CDCl3) δ 0.89 (s, 9H); 1.20-2.30 (m, 6H); [trans 2.55-2.75 (m)
and cis 2.78-2.90 (m), 1H]; [cis 3.50 (m) and trans 3.67 (dm, J =
13 Hz), 1H]. 19F NMR 376 MHz (CDCl3) trans δ -117.7 (m)
and cis -114.1 (m), ratio 3/1, respectively on the crude reaction
mixture. 13C NMR 100.6 MHz (CDCl3) 8 trans δ 19.2 (d, J = 8
Hz); 21.6 (s); 26.4 (d, J = 26 Hz); 26.7 (s); 33.2 (s); 40.0 (s); 57.5
(d, J = 21 Hz); 105.2 (d, J = 248 Hz); 161.7 (d, J = 6 Hz). 8 cis δ
21.2 (d, J = 9 Hz); 22.9 (s); 26.9 (s); 29.4 (d, J = 26 Hz); 32.9 (s);
43.2 (s); 55.5 (d, J = 22 Hz); 105.1 (d, J = 246 Hz); 162.9 (d, J =
FIGURE 2. (Left) C-N π bond orbital. (Right) Lone pair orbital
on the nitrogen atom.
intermediate resulted in separation to CSI and vinyl fluoride
or collapse to the β-lactam product. The hydrocarbon ethylene
has a stepwise transition state 27 kcal/mol higher than that of
the concerted transition state presumably from the high energy
required to form a primary cation (Supporting Information,
Table S2).
The concerted transition state is not orthogonal as reported
for ketene cycloadditions where the orbitals mix by a [π2(s) þ
π2(a)] process.15 A six-electron process, involving the lone pair
on nitrogen represented as [π2(s) þ π2(s) þ n2(s)], would allow
for a concerted cyclization where the alkene carbon atoms and
the OdCdN- moiety of CSI are in the same plane. Calculated
localized molecular orbitals of the cyclic 2 þ 2 transition state
for the cycloaddition of CSI to vinyl fluoride show significant
mixing between the C-N π-bond in CSI and the nitrogen lone
pair electrons (Figure 2).
Our data support a concerted reaction of CSI with these less
reactive fluoroalkenes because (i) reactions with 3E and 3Z are
stereospecific; (ii) neat reactions of CSI with 1, 2, 3E, 3Z 4, 5,
and 6 do not give uracil products; and (iii) a concerted pathway
is supported by quantum chemical calculations. A stepwise
pathway is untenable since it is prohibitively high in energy.
The expected dipolar intermediate with the carbonyl attached to
the fluoroalkene could not be located.
4 Hz). IR (KBr) neat mixture trans 1826 cm-1, cis 1838 cm-1
.
Exact mass [MH]þ calcd for C11H18NO3FSCl 298.067996;
found 298.068000.
Reactions of fluoroalkenes 1, 3E, 3Z, and 4 with CSI were
done similarly and the following data were obtained. 7: isolated
(50%) by column chromatography on silica gel with hexanes/
1
methylene chloride. H NMR 400 MHz (CDCl3) δ 1.59-1.72
(m, 3H); 1.81-1.99 (m, 2H); 2.01-2.21 (m, 2H); 2.69-2.80 (m,
1H); 3.52-3.63 (m, 1H). 19F NMR 376 MHz (CDCl3) δ -112.8
(m). 13C NMR 100.6 MHz (CDCl3). δ 15.5 (d, J = 8 Hz); 16.0
(s); 18.4 (s); 24.7 (d, J = 25 Hz); 53.5 (d, J = 21 Hz); 102.9 (d,
J = 248 Hz); 160.1 (d, J = 4 Hz). IR (KBr) neat 1832 cm-1
.
Exact mass [MH]þ calcd for C7H10NO3FSCl 242.00539; found
242.00470. 9E: isolated (50%) by column chromatography as
described above. 1H NMR 400 MHz (CDCl3) δ 1.18 (t, J = 7.4
Hz, 6H); 1.65-1.98 (m, 2H); 2.03-2.23 (m, 1H); 2.54-2.68 (m,
1H); 3.42-3.52 (m, 1H). 19F NMR 376 MHz (CDCl3) δ -119.4
(ddd, J = 30.5, 13.7, and 9.2 Hz). 13C NMR 100.6 MHz (CDCl3)
δ 7.6 (d, J = 4 Hz); 11.6 (s); 18.5 (d, J = 2 Hz); 24.7 (d, J = 28
Hz; 63.1 (d, J = 24 Hz); 108.2 (d, J = 247 Hz); 162.2 (d, J = 5
Hz). IR (KBr) neat 1830 cm-1. Exact mass [MH]þ calcd for
C7H12NO3FSCl 244.0210; found 244.0202. 9Z: isolated (55%)
by column chromatography as described above. 1H NMR 400
MHz (CDCl3) δ 1.11 (t, J = 7.6 Hz, 3H); 1.14 (t, J = 7.4 Hz,
3H); 1.78-1.99 (m, 2H); 2.10-2.29 (m, 1H); 2.47-2.60 (m, 1H);
3.36-3.43 (m, 1H). 19F NMR 376 MHz (CDCl3) δ -137.3 (dt,
J = 27.5 and 6.9 Hz). 13C NMR 100.6 MHz (CDCl3) δ 7.8 (d,
J = 4 Hz); 11.7 (s); 17.7 (d, J = 5 Hz); 27.5 (d, J = 28 Hz); 60.2
(d, J = 22 Hz); 107.6 (d, J = 249 Hz); 162.4 (d, J = 1.5 Hz). IR
(KBr) neat 1833 cm-1. Exact mass, negative ion ESI [Mþ - H]
calcd for C7H10NO3FSCl 242.0054; found 242.0051. 10 cis/
trans: cis and trans refers to the two methyl groups on the
cyclohexane ring; isolated (48%) by column chromatography as
described above. 1H NMR 600 MHz (C6D6) δ [cis 1.15 (dd, J =
7.0 and 1.8 Hz) and trans 1.26 (d, J = 7.0 Hz, 3H)]; [trans 1.30 (d,
J = 2.9 Hz) and cis 1.33 (d, J = 2.9 Hz, 3H); cis and trans
1.43-1.62 (m, 2H); cis and trans 1.62-1.73 (m, 2H); cis and
trans 1.80-1.96 (m, 2H); [cis 2.26 (m) and trans 2.78 (m), 1H].
19F NMR 376 MHz (CDCl3) trans δ -135.3 (s); cis -138.6 (brd.
s), ratio of 1.0/1.1, respectively on the crude reaction mixture.
13C NMR 150.8 MHz (C6H6) assignments supported by DEPT
and HSQC experiments. 10 cis δ 15.2 (CH3, d, J = 8.4 Hz); 16.1
(CH3, d, J = 7.9 Hz); 16.0 (CH2, s); 26.0 (CH2, d, J = 4.5 Hz);
28.7 (CH2, s); 31.5 (CH, d, J = 24.7 Hz); 59.9 (C adj. to the
carbonyl, d, J = 20.2 Hz); 108.7 (d, J = 256.4 Hz); 166.3 (d, J =
2.8 Hz). 10 trans: δ 14.4 (CH3, d, J = 9.0 Hz); 14.7 (CH3, d, J =
2.8 Hz); 17.1 (CH2, s); 25.6 (CH2, d, J = 7.3 Hz); 28.8 (CH2, s);
32.4 (CH, d, J = 24.1 Hz); 61.8 (C adj to the carbonyl, d, J =
18.0 Hz); 111.2 (d, J = 256.4 Hz); 166.7 (d, J = 2.8 Hz).
Experimental Section
Diethylaminosulfur trifluoride was added to cyclohexanones
in methylene chloride to give mixtures of 1,1-difluorocyclohex-
anes and 1-fluorocyclohexenes. After water workup, the methy-
lene chloride was removed by distillation, and the mixture was
distilled through a vigreux column to give enriched 1-fluorocy-
clohexenes 1, 2, and 4 containing various amounts of 1,1-difluoro-
cyclohexanes. Acyclic fluoroalkenes 3E,16 3Z,16 5,16 and 617 were
prepared as described in the literature. The β-fluorolactam pro-
ducts were isolated by chromatography (column or preparative
thin layer), or in one case by recrystallization. Spectral data
(NMR, IR) of crude reaction mixtures did not show other minor
stereo- or regioisomer products. The following procedure is
representative.
To 156 mg (1.00 mmol) of 4-tert-butyl-1-fluorocyclohexene
(2) in a small round-bottom flask was added 155 mg (96 μL, 1.10
mmol) of chlorosulfonyl isocyanate (CSI). The stirred mixture
was heated to 65-70 °C for 1 h and then cooled. Methylene
chloride (2-3 mL) was added, followed by dropwise addition of
(15) Woodward, R. B., Hoffmann, R. The Conservation of Orbital
Symmetry; Verlag Chemie, GmbH: Weinheim, Germany, 1970.
(16) Bache, G.; Fahrmann, U. Chem. Ber. 1981, 114, 4005.
(17) Eckes, L.; Hanack, M. Synthesis 1978, 217. Haufe, G.; Alvernhe, G.;
Laurent, A.; Ernet, T.; Goj, O.; Kroger, S.; Sattler, A. Org. Synth. 1999,
76, 159.
J. Org. Chem. Vol. 75, No. 22, 2010 7915

Shellhamer et al.
JOCNote
IR (KBr) neat mixture 1834 cm-1. Exact mass, negative ion ESI
[Mþ - H] calcd for C9H12NO3FSCl 268.0210; found 268.0212.
CSI (1.10 mmol) was added to fluoroalkenes 5 or 6 (1.00
mmol) in 0.2-4 mL of methylene chloride at 0 °C. The mixture
was allowed to warm to room temperature and then stirred for
4 h. Workup was accomplished as described above. Product
11 was obtained 90% pure (NMR) by preparative TLC,
and product 12 was isolated pure by recrystallization from
ether. Crystals from 12 decomposed in several minutes at room
temperature but were sufficiently stable in solution to obtain
spectral data. Wet crystals of 12 were kept cold during trans-
portation for X-ray analysis at low temperature. The following
data were obtained. 11: decomposition produced 8% side
products during purification by preparative thin layer chroma-
tography on silica gel with chloroform/methanol (95:5); isolated
in 33% yield. 1H NMR 400 MHz (CDCl3) δ 0.89 (t, J = 7.0 Hz,
3H); 1.29 (m, 10H); 1.38-1.62 (m, 2H); 2.06-2.26 (m, 1H);
2.44-2.56 (m, 1H); 3.33-3.48 (m, 2H). 19F NMR 376 MHz
(CDCl3) δ -120.9 (m). The 8% impurity around -131 to -132
ppm is from decomposition during purification by TLC. 13C
NMR 100.6 MHz (CDCl3) δ 14.0 (s); 22.5 (s); 23.5 (s); 23.7 (s);
29.0 (s); 29.1 (d, J = 14.0 Hz); 31.7 (s); 48.9 (d, J = 25.1 Hz); 76.8
(d, J = 4.8 Hz); 105.7 (d, J = 246.1 Hz); 158.6 (d, J = 3.0 Hz).
vibrational frequencies were computed to verify each stationary
point as either a local minimum (with all real frequencies) or
a transition state (with exactly one imaginary vibrational
frequency). Free energies were obtained using the computed
vibrational frequencies (which were scaled by 0.9748)19 and the
ideal gas þ rigid rotor þ harmonic oscillator models.20 Follow-
ing an approach similar to that of Lopez et al.,5b electrostatic free
ꢀ
energies of salvation were obtained using the conductor polariza-
tion continuum model (C-PCM),21a-c with methylene dichloride
as the solvent, via single point energy calculations at the MP2/
6-311G(d,p) stationary points. Intrinsic reaction coordinate
(IRC) calculations22a-e using the Gonzalez-Schlegel second
order method23 were performed to trace the minimum energy
reaction paths connecting each transition state to reactants and
products. All calculations were performed using the GAMESS
quantum chemistry code.24a,b
Acknowledgment. Support for this work was provided by
the National Science Foundation (NSF-RUI Grant No.
CHE-0640547) and Research Associates of PLNU (alumni
support group). We would like to acknowledge our use of the
400 MHz NMR at the University of San Diego obtained by
support from the National Science Foundation (NSF MRI
Grant No. CHE-0417731). We thank Dr. Leroy Lafferty at
San Diego State University for conducting the 1-dimensional
ROESY experiments at 600 MHz.
IR (KBr) neat 1831 cm-1. Exact mass, negative ion ESI [Mþ
-
H] calcd for C11H18NO3FSCl 298.0680; found 298.0716. 12:
yield (65%) by 19F NMR with 4-fluoroanisole as internal
1
standard. H NMR 400 MHz (CDCl3) δ 3.62-3.85 (m, 2H);
7.51 (m, 3H); 7.61 (m, 2H). 19F NMR 376 MHz (CDCl3) δ
-129.0 (t, J = 10.5 Hz). 13C NMR 100.6 MHz (CDCl3) δ 53.4
(d, J = 25 Hz); 103.7 (d, J = 246 Hz); 125.2 (d, J = 8 Hz); 129.2
(s); 130.9 (s); 132.0 (d, J = 29 Hz); 158.9 (d, J = 2 Hz). IR (KBr)
Supporting Information Available: Spectral data to char-
acterize the products, X-ray data for 12 in CIF format, and quantum
chemical data are in the Supporting Information. This material is
available free of charge via the Internet at http://pubs.acs.org.
neat 1834 cm-1
.
Quantum chemical calculations were performed using second
order perturbation theory (MP2, also known as MBPT(2)13a-e
)
(22) (a) Ishida, K.; Morokuma, K.; Komornicki, A. J. Chem. Phys. 1977,
66, 2153. (b) Muller, K. Angew. Chem., Int. Ed. Engl. 1980, 19, 1. (c) Schmidt,
M. W.; Gordon, M. S.; Dupuis, M. J. Am. Chem. Soc. 1985, 107, 2585. (d)
Garrett, B. C.; Redmon, M. J.; Steckler, R.; Truhlar, D. G.; Baldridge, K. K.;
Bartol, D.; Schmidt, M. W.; Gordon, M. S. J. Phys. Chem. 1988, 92, 1476. (e)
Baldridge, K. K.; Gordon, M. S.; Steckler, R.; Truhlar, D. G. J. Phys. Chem.
1989, 93, 5107.
and the 6-311G(d,p) basis set.14 All structures were fully opti-
mized using a quasi-Newton-Raphson approach based
upon the quadratic approximation, also known as the trust
radius image minimization (TRIM) method.18 Harmonic
(23) Gonzales, C.; Schlegel, H. B. J. Chem. Phys. 1989, 90, 2154.
(24) (a) Schmidt, M. W.; Baldridge, K. K.; Boatz, J. A.; Elbert, S. T.;
Gordon, M. S.; Jensen, J. H.; Koseki, S.; Matsunaga, N.; Nguyen, K. A.; Su,
S.; Windus, T. L.; Dupuis, M.; Montgomery, J. A. J. Comput. Chem. 1993,
14, 1347. (b) Gordon, M. S. Schmidt, M. W. Advances in electronic structure
theory: GAMESS a decade later. In Theory and Applications of Computa-
tional Chemistry: The First Forty Years; Dykstra, C. E., Frenking, G., Kim,
K. S., Scuseria, G. E., Eds.; Elsevier: Amsterdam, 2005; pp 1167-1189.
(18) Helgaker, T. Chem. Phys. Lett. 1991, 182, 503.
(19) Scott, A. P.; Radom, L. J. Phys. Chem. 1996, 100, 16502.
(20) Statistical Mechanics; McQuarrie, D. A., Woods, J. A., Eds.; Harper
& Row: New York, 1976.
(21) (a) Li, H.; Pomelli, C. S.; Jensen, J. H. Theor. Chim. Acta 2003, 109,
71. (b) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995. (c) Cossi, M.;
Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem. 2003, 24, 669.
7916 J. Org. Chem. Vol. 75, No. 22, 2010