Domino Hydroboration/Trifluoromethylation of Alkynes Using Fluoroform-Derived [CuCF3]

Article abstract of DOI:10.1021/acs.joc.7b00755

A domino hydroboration/trifluoromethylation (formal hydrotrifluoromethylation) of alkynes using the fluoroform-derived [CuCF₃] reagent is achieved. Synthetically useful (E)-alkenyl-CF₃ building blocks and 1,1-bis(trifluoromethyl)-substituted alkenes can be prepared under ambient conditions in one pot/one step from alkynes. The ultimate source of CF₃ is the inexpensive industrial waste fluoroform.

Full text of DOI:10.1021/acs.joc.7b00755

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Article
Domino Hydroboration/Trifluoromethylation
of Alkynes Using Fluoroform- Derived CuCF3
Lisi He, Xinkan Yang, and Gavin Chit Tsui
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 19 May 2017
Downloaded from http://pubs.acs.org on May 19, 2017
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Domino Hydroboration/Trifluoromethylation of Alkynes Using
Fluoroform-Derived CuCF3
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Lisi He, Xinkan Yang, and Gavin Chit Tsui*
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New
Territories, Hong Kong SAR
ABSTRACT
A domino hydroboration/trifluoromethylation (formal hydrotrifluoromethylation) of
alkynes using the fluoroform-derived [CuCF3] reagent is achieved. Synthetically
useful (E)-alkenyl-CF3 building blocks and 1,1-bis(trifluoromethyl)-substituted
alkenes can be prepared under ambient conditions in one-pot/one-step from alkynes.
The ultimate source of CF3 is the inexpensive industrial waste fluoroform.
CF3H
(fluoroform)
24 examples
up to 85% yield
(E/Z >20:1)
CF3
CF3
R
R
R
[CuCF3]
(stabilized with Et3N·3HF)
or
or
B2Pin2
5 examples
DMF, 23 oC, 8 h
open to air
up to 85% yield
(both CF3 groups
from CF3H)
R
CF3
CF3
INTRODUCTION
The importance of organofluorine compounds in pharmaceuticals, agrochemicals
and materials cannot be overstated.1 In particular, the incorporation of trifluoromethyl
(CF3) groups can significantly enhance the bioavailability, metabolic stability,
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lipophilicity and binding selectivity of drug candidates.2 Driven by its high demand, a
surge of new trifluoromethylation methods can be witnessed in recent years.3
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Compared to the formation of aryl-CF3 bonds,3g-i the area of alkenyl-CF3 bond
formation is underdeveloped.3i,4,5,7 Traditional approaches such as Horner or Julia–
Kocienski olefination reactions generally provide E/Z mixtures of trifluoromethylated
alkenes.4 More modern approaches involve transition metal-catalyzed/-mediated
cross-coupling reactions between alkenyl species and CF3 sources.5 The alkenyl
coupling partners, including vinyl boronic acids,5a-c trifluoroborates,5d-f carboxylic
acids,5g-j halides5k-l and sulfonates,5m are pre-functionalized substrates and usually
tedious to synthesize. In most cases, electrophilic CF3 sources, e.g. Togni6a and
Umemoto6b reagents, were employed that were expensive or need to be prepared
separately.7 Direct trifluoromethylation of terminal alkenes have also been reported,
however, the substrate scopes were rather limited to specialized alkenes.8
An alternative approach is the hydrotrifluoromethylation of terminal alkynes to
obtain the trifluoromethylated alkenyl-CF3 products.9 Apart from an isolated early
example of ultrasound-promoted reaction,10a only a handful of methods are available
using photocatalytic,10b-d radical-mediated10e and metal-catalyzed10f reactions. They
provided convenient access to trifluoromethylated alkenes but suffered universally
from the problems of E/Z selectivities. Therefore, the search for an efficient, selective
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and convenient method for synthesizing trifluoromethylated alkenes is still much
needed. Inspired by the precedents of trifluoromethylation of vinyl boron species5a-f
and Cu-mediated hydroboration of alkynes,11 we envision that a domino
hydroboration/trifluoromethylation process12 (formal hydrotrifluoromethylation) can
be developed to selectively construct the C(sp2)-CF3 bond in one-pot/one-step from
terminal alkynes (Scheme 1).
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Scheme 1. Synthesis of (E)-alkenyl-CF3 products via copper-mediated
domino hydroboration/trifluoromethylation of terminal alkynes
RESULTS AND DISCUSSION
We began the studies by identifying a suitable combination of CF3 source and
copper promoter, using 2-ethynylnaphthalene 1a as the substrate and
bis(pinacolato)diboron (B2Pin2)11e-i as the borylation reagent (Scheme 2). In the
presence of CuCl under aerobic conditions, electrophilic Togni reagent6a and
3c
nucleophilic TMSCF3 were ineffective in forming the desired product 2a, giving
alkynyl-CF3 3a and dimer 4a instead as major side products (conditions A-B).13
Adding proton sources such as MeOH or Et3N·3HF also did not give the desired
product 2a in condition B. The copper complex (PPh3)3CuCF314 gave 28% yield of 2a
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but a significant amount of dimer 4a (condition C). To our delight, the
fluoroform-derived [CuCF3],15 prepared by Grushin's method,16a provided a good
yield (80%) of 2a (E/Z >20:1) with minimum amounts of side products (condition D).
Fluoroform (CF3H, trifluoromethane, HFC-23) is an industrial byproduct from Teflon
manufacturing and is commercially available at low cost. Grushin's pioneering work
on the preparation and applications of fluoroform-derived [CuCF3] is one of the most
useful and practical approaches for utilizing fluoroform as a CF3 source in organic
synthesis.16 We have also previously employed this reagent for efficient C(sp)-CF3
and C(sp3)-CF3 bond formations with alkynes and alkenes.17
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Scheme 2. Initial studies of CF3 sources and copper promoter
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Encouraged by the promising initial results, we proceeded with the optimization
studies (Table 1, see Supporting Information for full details). Using pinacolborane
(HBPin) or without borylation reagent afforded only trace products (entries 1-2).
Control experiment showed no conversion in the absence of [CuCF3]. A slight excess
(1.2 equiv) of B2Pin2 increased the yield but the yield was decreased with larger
excess (entries 3-4). On the other hand, increasing the equivalents of [CuCF3] (2.5
equiv) had no effect but less [CuCF3] (1.5 equiv) caused a drop in yield (entry 5-6).
Increasing the reaction temperature gave lower yields (entries 7-8). The highest yield
of alkene 2a (92%, 85% isolated, E/Z >20:1) was obtained with a lower concentration
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(0.05M) (entry 9). The reaction was best run open to air, bubbling oxygen or using
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Ag2CO3 as an oxidant led to much poorer yields (entries 10-11).
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Table 1. Optimization studies.a
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entry
equiv of
[CuCF3]
borylation reagent temp
yield of 2a
(%)b
(equiv)
(oC)
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35
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1
2.0
2.0
2.0
2.0
2.5
1.5
2.0
2.0
2.0
2.0
2.0
HBPin (1.0)
none
<5
2
<5
3
B2Pin2 (1.2)
B2Pin2 (2.0)
B2Pin2 (1.2)
B2Pin2 (1.2)
B2Pin2 (1.2)
B2Pin2 (1.2)
B2Pin2 (1.2)
B2Pin2 (1.2)
B2Pin2 (1.2)
89
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40
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89
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81
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85
8
70
9c
10e
11f
92 (85)d
23
21
aGeneral conditions: [CuCF3] (in DMF solution, stabilized by Et3N·3HF) was added to a mixture of 1a
(0.1 mmol) and borylation reagent in DMF (1.0 mL). The [CuCF3] was prepared from
CuCl/t-BuOK/fluoroform according to Grushin’s procedure in ref 16a. Yield was determined by 19F
b
c
d
e
NMR analysis using fluorobenzene as the internal standard. 1.5 mL of DMF. Isolated yield. Oxygen
f
was bubbled through the reaction mixture. Reaction was under argon in the presence of Ag2CO3 (2.0
equiv).
With the optimized conditions in hand, we next investigated the scope of
terminal alkynes
1
in this reaction (Table 2).
A
wide range of
aryl-/heteroaryl-substituted alkenyl-CF3 products (2a-v) were obtained in moderate to
good yields with broad functional group compatibility. In general, electron-rich
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aromatic alkynes gave higher yields (2a-f vs. 2g-i). Substituents at the para (2c-l),
meta (2m-n) and ortho (2o-q) positions of the aromatic ring were all tolerated.
Bulkier aromatic (2s) and heteroaromatic groups (2u-v) were also compatible. The
structurally intriguing bis-trifluoromethylated product 2t could be obtained from the
corresponding 1,4-diyne substrate using a larger excess of the reagents. The
chemoselectivity of the reaction was remarkable as trifluoromethylation of
arylsilanes18 and aryl bromides16a,e with copper CF3 reagents are known, and yet the
aromatic silyl (2f) and halogen (2j-l) substituents remained intact under the reaction
conditions. Moreover, sensitive groups such as the unprotected amino (2e,q) and
hydroxy (2n) groups were also tolerated. The volatility of some products made the
isolation difficult, therefore these reactions were carried out on a larger scale and
NMR yields were given for comparison. Finally, alkyl-substituted products (2w-x)
were obtained albeit in lower yields. Attempted optimization including changing the
reaction temperature and equivalents of CuCF3, prolonging reaction time and adding
ligands did not improve the yield of 2x. In all cases, the E/Z selectivity of the reaction
was excellent (>20:1).
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Table 2. Scope of terminal alkynes 1 in the synthesis of (E)-alkenyl-CF3
products 2.a
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aGeneral conditions: [CuCF3] (in DMF solution, 2.0 equiv, prepared from CuCl/t-BuOK/fluoroform,
stabilized by Et3N·3HF) was added to the mixture of 1 (0.2 mmol) and B2Pin2 (1.2 equiv) in DMF (3.0
b
c
mL). 1 mmol scale. Yield was determined by 19F NMR analysis using fluorobenzene as the internal
standard. d4.0 equiv of [CuCF3] and 2.4 equiv of B2Pin2.
Some of the terminal alkynes such as 1a were prepared from the TMS-protected
alkynes
by
desilylation.
We
envisioned
that
a
one-pot/one-step
desilylation/hydroboration/trifluoro-methylation of TMS-protected alkyne 1a’ was
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possible (Scheme 3). Indeed, the one-pot protocol was equally efficient as the
two-step sequence (80% yield vs. 77% yield over two steps), using extra
tetrabutylammonium fluoride (TBAF), but without the separation and purification of
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1a.
Scheme 3. One-pot synthesis of 2a from TMS-protected alkyne 1a'
When applying the reaction to internal alkynes 5, we encountered low
conversions and yields (Scheme 4a). We were able to isolate 33% yield of the
phenyl/methyl-substituted alkenyl product (E)-6a. However, reactivity decreased
sharply with alkynes containing bulkier phenyl/n-butyl (5b) and phenyl/phenyl (5c)
substituents. On the other hand, an electron-withdrawing group such as 4-CF3 on the
phenyl ring improved the yield to a certain extent (6c vs. 6d). Conversion improved
significantly in the case of internal alkyne having an electron-withdrawing group such
as COOEt (5e). However, an unidentified mixture of isomers (regio- and/or stereo-)
was observed. These results pointed to the probable tolerance of a small and
electron-deficient substituent group on the internal alkyne. Indeed, the CF3-containing
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internal alkynes 3 were suitable substrates for the reaction, which can be prepared
conveniently from terminal alkynes 1 by our previously reported trifluoromethylation
method using fluoroform-derived [CuCF3] (Scheme 4b).17a A variety of
1,1-bis(trifluoromethyl)-substituted alkenyl products 7a-e were synthesized from 3 in
moderate to good yields. The steric bias of the alkyne substituents (aryl vs. CF3) could
account for the high regioselectivity.20,21 The preparation of these potentially useful
fluorinated building blocks have only been described by a handful of early reports
using indirect approaches.22 Our method offered an easy access to 7 in only two steps
from readily available terminal alkynes 1 and notably the source of both CF3 groups
was fluoroform.
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Scheme 4. (a) Using Internal Alkynes as substrates. (b) Synthesis of
1,1-Bis(trifluoromethyl)-Substituted Alkenes 7 using CF3-Containing Internal
Alkynes 3.
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A series of experiments were conducted to gain mechanistic insights (Scheme 5).
We were able to intercept the (E)-vinyl BPin intermediate 8a in 80% yield after 10
min reaction time. Prolonged reaction time led to the expected alkenyl-CF3 product 2a
(Scheme 5a). This (E)-vinyl BPin 8a participated in the trifluoromethylation reaction
smoothly using fluoroform-derived [CuCF3] to provide (E)-2a (Scheme 5b). The E/Z
(56:44) mixture of 8a and 8a’ gave the E/Z mixture of 2a and 2a’ in similar ratio
(57:43) under identical conditions (Scheme 5c). When the reaction was carried out
under argon, the major product obtained from 1a was the vinyl BPin 8a instead
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(Scheme 5d). When using a catalytic amount of [CuCF3] (0.1 equiv), only 13% of 8a
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was obtained with low conversion of 1a (Scheme 5e).
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Scheme 5. Mechanistic Studies
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Based on these studies and known literature examples, we propose the following
reaction mechanism for the domino hydroboration/trifluoromethylation of terminal
alkynes using the fluoroform-derived [CuCF3] (Scheme 6). In the presence of B2Pin2,
the initial [CuICF3] presumably generates a borylcopper species for the regio- and
stereoselective hydroboration of terminal alkyne 1 to form (E)-vinyl BPin 8. This
process can occur via anti-Markovnikov syn-borylcupration and subsequent
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protonation thus accounting for the high levels of regio- and stereo-control.11e-g,19,20
An excess amount of the unstable [CuICF3]16a,17a is needed for the efficient
hydroboration (c.f. Scheme 5d-e). The stabilizer Et3N·3HF also plays the role as the
proton source. The [CuICF3] species can be oxidized to [CuIICF3]16b in air, which is
needed for transmetallation to form the (E)-vinyl CuCF3 species 9. The exact nature
of this species is unclear, however, the involvement of [CuIIICF3] cannot be
completely ruled out.23 The final reductive elimination leads to the (E)-alkenyl CF3
product 2. Overall, the (E)-selective hydrotrifluoromethylation of terminal alkynes 1
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is achieved.
Scheme 6. Proposed Mechanism
CONCLUSION
In summary, we have developed a new synthetic method for the preparation of
useful (E)-alkenyl-CF3 building blocks 2 and 1,1-bis(trifluoromethyl)-substituted
alkenes 7 using the fluoroform-derived [CuCF3] reagent. The reaction has the
following unique features: (1) converting easily accessible terminal alkynes into
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alkenyl-CF3 products with excellent E-selectivity and good functional group tolerance;
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(2) utilizing
a
domino hydroboration/trifluoromethylation sequence in
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one-pot/one-step without the isolation of intermediates; (3) mild reaction conditions at
room temperature and open to air; (4) using the inexpensive industrial waste
fluoroform as the CF3 source.
EXPERIMENTAL SECTION
General Experimental. Unless otherwise noted, the hydrotrifluoromethylation
reactions were carried out open to air in a test tube or round bottom flask (RBF) with
magnetic stirring. Analytical thin layer chromatography (TLC) was performed with
EM Science silica gel 60 F254 aluminum plates. Visualization was done under a UV
lamp (254 nm) and by immersion in ethanolic phosphomolybdic acid (PMA) or
potassium permanganate (KMnO4), followed by heating using a heat gun. Organic
solutions were concentrated by rotary evaporation at 23–35 °C. Purification of
reaction products was generally done by flash column chromatography with Grace
Materials Technologies 230−400 mesh silica gel. It should be noted that most of the
hydrotrifluoromethylated products 2 are volatile and therefore high vacuum should be
avoided.
Materials. Fluoroform (Research Grade, Purity: 99.999% min., 9.1kg in 16 L size
cylinder) was purchased from SynQuest Laboratories, USA. Copper (I) chloride
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(extra pure, 99.99%) and Et3N·3HF (97%) were purchased from Acros. Potassium
tert-butoxide (97%) was purchased from Alfa Aesar. B2Pin2 was purchased from J&K
Scientific. DMF was dried over solvent purification system, stored over 4Å molecular
sieves and degassed before use. Other reagents were purchased from Acros, J&K
Scientific and Aldrich. Alkynes 1b,d,h,j,p,u,v,x and 5a,b,c were purchased from
commercial sources. Other alkynes and the (E)-vinyl BPin 8a were known
compounds and prepared according to literature procedures.24
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Instrumentation. Proton nuclear magnetic resonance spectra (1H NMR) spectra,
carbon nuclear magnetic resonance spectra (13C NMR) and fluorine nuclear magnetic
resonance spectra (19F NMR) were recorded at 23 °C on a Bruker 400 spectrometer in
CDCl3 (400 MHz for 1H and 100 MHz for 13C and 376 MHz for 19F). Chemical shifts
for protons were reported as parts per million in δ scale using solvent residual peak
13
(CHCl3: 7.26 ppm) as internal standards. Chemical shifts of C NMR spectra were
reported in ppm from the central peak of CDCl3 (77.16 ppm) on the δ scale. Chemical
shifts of 19F NMR are reported as parts per million in δ scale using fluorobenzene
(-113.15 ppm) as internal standards. Data are represented as follows: chemical shift,
integration, multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, quint =
quintuplet, oct = octuplet, m = multiplet, br = broad), and coupling constant (J, Hz).
Infrared spectra were recorded on a Nicolet 420 FT-IR spectrophotometer and
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reported in wave numbers (cm-1).High resolution mass spectra (HRMS) were obtained
on a Finnigan MAT 95XL GC Mass Spectrometer with the mass analyzer of magnetic
sector used.
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Experimental Procedures.
Procedures for the preparation of fluoroform-derived CuCF3 reagent: 16a,17a
In a glove box, to a 50 mL RBF was charged CuCl (0.50 g, 5.05 mmol), t-BuOK (1.18
g, 10.54 mmol) and a stir bar. The flask was sealed with a septum, brought out of the
glove box and put under an argon atmosphere. Degassed DMF (11 mL) was added via
syringe and the mixture was stirred at room temperature for 30 min. The flask was
then evacuated on a vacuum line for 10 seconds (the weight of the whole flask was
obtained). Then fluoroform was quickly bubbled into the mixture by using a needle
connected to the fluoroform cylinder or a fluoroform balloon at room temperature for
5 min. After removing the fluoroform inlet, the weight of the whole flask was
obtained again, and the amount of fluoroform in the flask was calculated (~1.1 g, ~15
mmol). The mixture was stirred for 5 min and Et3N·3HF (0.43 mL, 2.65 mmol) was
added under argon and the mixture was stirred for another 5 min. A colorless/slightly
brown solution with some white solid was obtained as the [CuICF3] solution in DMF
(~0.4 M). The yield of [CuICF3] was generally >90% determined by 19F NMR
analysis (DMF, unlocked) using fluorobenzene as the internal standard.
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General procedure for the synthesis of (E)-alkenyl-CF3 products 2 with
fluoroform-derived CuCF3 and B2Pin2 (Table 1−2, Scheme 2 Condition D,
Scheme 4): Alkynes (1, 3 or 5, 0.2 mmol, 1.0 equiv.), B2Pin2 (0.24 mmol, 1.2 equiv.)
and DMF (3 mL) were added to a 10 mL RBF with a magnetic stir bar. Then the flask
was sealed with a septa and flushed with argon. Fluoroform-derived CuCF3 (0.4 M in
DMF, 1.0 mL, 2.0 equiv.) was then added under argon. Then the septa was removed
and the mixture was stirred in air at room temperature for 8 h. The reaction mixture
turned dark brown when adding the CuCF3 and some black solid formed in a few
minutes, and then the solid slowly dissolved during the reaction. The reaction mixture
was filtered through a short pad of silica gel and rinsed with 30% diethyl ether in
hexanes (100 mL) and then concentrated by rotary evaporator. The crude mixture was
purified by flash column chromatography on silica gel.
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2a: (E)-2-(3,3,3-trifluoroprop-1-en-1-yl)naphthalene. Prepared according to the
general procedure and purified by flash column chromatography (hexane). White
solid; 38 mg, 85% (0.2 mmol scale); 176 mg, 80% (1 mmol scale). Rf = 0.55 (hexane).
1H NMR (400 MHz, CDCl3): δ 7.87–7.84 (m, 4H), 7.60 (dd, JH-H= 8.7, 1.5 Hz, 1H),
7.55–7.51 (m, 2H), 7.32 (dq, JH-H = 16.1 Hz, JH-F = 2.1 Hz, 1H), 6.32 (dq, JH-H = 16.1
13
Hz, JH-F = 6.5 Hz, 1H) ppm. C NMR (100 MHz, CDCl3): δ 137.9 (q, JC-F = 6.8 Hz),
134.2, 133.4, 131.0, 129.2, 128.9, 128.6, 127.9, 127.3, 126.9, 123.9 (q, JC-F = 268.9 Hz),
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123.3, 116.1 (q, JC-F = 33.8 Hz) ppm. F NMR (376 MHz, CDCl3): δ -63.2 (dd, JH-F
=
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6.5, 2.0 Hz, 3F) ppm. The spectral data are in accordance with the literature report.16i
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2b: (E)-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the general
procedure and purified by flash column chromatography (pentane). Colorless oil, 90
1
mg, 52% (1 mmol scale). Rf = 0.72 (hexane). H NMR (400 MHz, CDCl3): δ 7.48–
7.39 (m, 5H), 7.17 (dq, JH-H = 16.1 Hz, JH-F = 2.2 Hz, 1H), 6.22 (dq, JH-H = 16.1 Hz, JH-F
13
= 6.5 Hz, 1H) ppm. C NMR (100 MHz, CDCl3): δ 137.8 (q, JC-F = 6.8 Hz), 133.6,
130.2, 129.1, 127.7, 123.8 (q, JC-F = 268.7 Hz), 116.0 (q, JC-F = 33.8 Hz) ppm. 19F NMR
(376 MHz, CDCl3): δ -63.4 (dd, JH-F = 6.6, 2.2 Hz, 3F) ppm. The spectral data are in
accordance with the literature report.25
2c: (E)-1-methoxy-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to
the general procedure and purified by flash column chromatography (5%
1
EtOAc/hexane). White solid; 33 mg, 82%. Rf = 0.65 (10% EtOAc/hexane). H NMR
(400 MHz, CDCl3): δ 7.39 (d, JH-H = 8.8 Hz, 2H), 7.09 (dq, JH-H = 16.1 Hz, JH-F = 2.1
Hz, 1H), 6.91 (d, J = 8.8 Hz, 2H), 6.07 (dq, JH-H = 16.1 Hz, JH-F = 6.6 Hz, 1H), 3.84 (s,
3H) ppm. 13C NMR (100 MHz, CDCl3): δ 161.2, 137.2 (q, JC-F = 6.8 Hz), 129.2, 126.2,
19
124.1 (q, JC-F = 268.5 Hz), 114.5, 113.5 (q, JC-F = 33.6 Hz), 55.5 ppm. F NMR (376
MHz, CDCl3): δ -62.9 (dd, JH-F = 6.6, 2.0 Hz, 3F) ppm. The spectral data are in
accordance with the literature report.22
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2d: (E)-1-methyl-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (pentane). White
solid; 117 mg, 63% (1 mmol scale). Rf = 0.75 (hexane). 1H NMR (400 MHz, CDCl3):
δ 7.36 (d, JH-H = 8.8 Hz, 2H), 7.21 (d, JH-H = 8.8 Hz, 2H), 7.14 (dq, JH-H = 16.1 Hz, JH-F
= 2.0 Hz, 1H), 6.17 (dq, JH-H = 16.1 Hz, JH-F = 6.6 Hz, 1H), 2.40 (s, 3H) ppm. 13C NMR
(100 MHz, CDCl3): δ 140.5, 137.7 (q, JC-F = 6.8 Hz), 130.8, 129.8, 127.6, 124.0 (q, JC-F
= 268.7 Hz), 114.9 (q, JC-F = 33.7 Hz), 21.5 ppm. 19F NMR (376 MHz, CDCl3): δ -63.2
(d, JH-F = 6.7 Hz, 3F) ppm. The spectral data are in accordance with the literature
report.5j
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2e: (E)-4-(3,3,3-trifluoroprop-1-en-1-yl)aniline. Prepared according to the general
procedure and purified by flash column chromatography (15% EtOAc/hexane). Light
1
brown solid, 27 mg, 73%. Rf = 0.48 (20% EtOAc/hexane). H NMR (400 MHz,
CDCl3): δ 7.26 (d, JH-H = 8.4 Hz, 2H), 7.02 (dq, JH-H = 16.1 Hz, JH-F = 2.1 Hz, 1H), 6.66
(d, JH-H = 8.4 Hz, 2H), 5.98 (dq, JH-H = 16.1 Hz, JH-F = 6.7 Hz, 1H), 3.88 (brs, 2H) ppm.
13C NMR (100 MHz, CDCl3): δ 148.3, 137.6 (q, JC-F = 6.8 Hz), 129.2, 124.3 (q, JC-F
=
268.2 Hz), 123.8, 115.1, 111.7 (q, JC-F = 33.6 Hz) ppm. 19F NMR (376 MHz, CDCl3): δ
-62.5 (d, JH-F = 6.7 Hz, 3F) ppm. The spectral data are in accordance with the literature
report.5j
2f: (E)-trimethyl(4-(3,3,3-trifluoroprop-1-en-1-yl)phenyl)silane. Prepared according
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to the general procedure and purified by flash column chromatography (hexane).
Colorless oil, 40.5 mg, 83%. Rf = 0.70 (hexane). 1H NMR (400 MHz, CDCl3): δ 7.55
(d, JH-H = 8.0 Hz, 2H), 7.43 (d, JH-H = 8.0 Hz, 2H), 7.15 (dq, JH-H = 16.1 Hz, JH-F = 2.1
Hz, 1H), 6.23 (dq, JH-H = 16.1 Hz, JH-F = 6.5 Hz, 1H), 0.28 (s, 9H) ppm. 13C NMR (100
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MHz, CDCl3): δ 143.4, 137.8 (q, JC-F = 6.6 Hz), 134.0, 133.8, 126.8, 123.8 (q, JC-F
=
268.8 Hz), 116.1 (q, JC-F = 33.8 Hz), -1.1 ppm. 19F NMR (376 MHz, CDCl3): δ -63.4 (d,
JH-F = 6.8 Hz, 3F) ppm. IR (neat): 2957, 1665, 1271(br), 1124, 972, 842 cm-1. HRMS
m/z (EI): calcd. for C12H15F3Si [M]+: 244.0890; found: 244.0891.
2g: ethyl (E)-4-(3,3,3-trifluoroprop-1-en-1-yl)benzoate. Prepared according to the
general procedure and purified by flash column chromatography (5% EtOAc/hexane).
1
Colorless oil, 25 mg, 52%. Rf = 0.52 (10% EtOAc/hexane). H NMR (400 MHz,
CDCl3): δ 8.06 (d, JH-H = 8.3 Hz, 2H), 7.51 (d, JH-H = 8.3 Hz, 2H), 7.18 (dq, JH-H = 16.2
Hz, JH-F = 2.0 Hz, 1H), 6.30 (dq, JH-H = 16.1 Hz, JH-F = 6.4 Hz, 1H), 4.39 (q, JH-H = 7.1
Hz, 2H), 1.40 (t, JH-H = 7.1 Hz, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ 166.1, 137.6,
136.8 (q, JC-F = 6.8 Hz), 131.8, 130.3, 127.6, 123.4 (q, JC-F = 269.1 Hz), 118.2 (q, JC-F
=
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34.1 Hz), 61.4, 14.4 ppm. F NMR (376 MHz, CDCl3): δ -63.7 (d, JH-F = 6.4 Hz, 3F)
ppm. The spectral data are in accordance with the literature report.26
2h:
(E)-1-(trifluoromethyl)-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene.
Prepared
according to the general procedure and purified by flash column chromatography
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(pentane). Colorless oil, 72 mg, 30% (1 mmol scale). Rf = 0.73 (hexane). H NMR
(400 MHz, CDCl3): δ 7.66 (d, JH-H = 8.3 Hz, 2H), 7.57 (d, JH-H = 8.3 Hz, 2H), 7.19 (dq,
JH-H = 16.2 Hz, JH-F = 2.0 Hz, 1H), 6.30 (dq, JH-H = 16.2 Hz, JH-F = 6.4 Hz, 1H) ppm. 13C
NMR (100 MHz, CDCl3): δ 136.9, 136.4 (q, JC-F = 6.8 Hz), 131.9 (q, JC-F = 32.7 Hz),
127.9, 126.1 (q, JC-F = 3.8 Hz), 123.9 (q, JC-F = 272.2 Hz), 123.3 (q, JC-F = 269.2 Hz),
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118.6 (q, JC-F = 34.2 Hz) ppm. F NMR (376 MHz, CDCl3): δ -62.9 (s, 3F), -63.8 (d,
JH-F = 6.4 Hz, 3F) ppm. The spectral data are in accordance with the literature report.5e
2i: (E)-1-(4-(3,3,3-trifluoroprop-1-en-1-yl)phenyl)ethan-1-one. Prepared according to
the general procedure and purified by flash column chromatography (5%
EtOAc/hexane). White solid, 21.5 mg, 51% Rf = 0.45 (10% EtOAc/hexane). 1H NMR
(400 MHz, CDCl3): δ 7.98 (d, JH-H = 8.3 Hz, 2H), 7.55 (d, JH-H = 8.3 Hz, 2H), 7.19 (dq,
JH-H = 16.2 Hz, JH-F = 2.0 Hz, 1H), 6.31 (dq, JH-H = 16.2 Hz, JH-F = 6.4 Hz, 1H), 2.62 (s,
3H) ppm. 13C NMR (100 MHz, CDCl3): δ 197.4, 138.1, 137.8, 136.7 (q, JC-F = 6.7 Hz),
129.1, 127.9, 123.4 (q, JC-F = 269.2 Hz), 118.5 (q, JC-F = 34.1 Hz), 26.8 ppm. 19F NMR
(376 MHz, CDCl3): δ -63.7 (dd, JH-F = 6.5, 2.0 Hz, 3F) ppm. The spectral data are in
accordance with the literature report.5f
2j: (E)-1-fluoro-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (pentane), containing
4% of inseparable side product 4-fluorostyrene. Colorless oil, 114 mg, 60% (1 mmol
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scale). Rf = 0.70 (hexane). 1H NMR (400 MHz, CDCl3): δ 7.46–7.43 (m, 2H), 7.14–
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8
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7.07 (m, 3H), 6.13 (dq, JH-H = 16.1 Hz, JH-F = 6.4 Hz, 1H) ppm. C NMR (100 MHz,
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CDCl3): δ 163.9 (d, JC-F = 250.5 Hz), 136.6 (q, JC-F = 6.8 Hz), 129.8 (d, JC-F = 3.2 Hz),
129.5 (d, JC-F = 8.5 Hz), 123.7 (q, JC-F = 268.8 Hz), 116.2 (d, JC-F = 21.9 Hz), 115.8 (q,
JC-F = 34.1 Hz) ppm. 19F NMR (376 MHz, CDCl3): δ -63.4 (dd, JH-F = 6.4, 2.0 Hz, 3F),
-110.3 (m, 1F) ppm. The spectral data are in accordance with the literature report.5g
2k: (E)-1-chloro-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (pentane). Colorless
1
oil, 34 mg, 83%. Rf = 0.74 (hexane). H NMR (400 MHz, CDCl3): δ 7.46−7.31 (m,
4H), 7.11 (dq, JH-H = 16.2 Hz, JH-F = 2.1 Hz, 1H), 6.18 (dq, JH-H = 16.2 Hz, JH-F = 6.5 Hz,
1H) ppm. 13C NMR (100 MHz, CDCl3): δ 136.6 (q, JC-F = 6.8 Hz), 136.1, 132.0, 129.4,
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128.9, 123.6 (q, JC-F = 268.9 Hz), 116.6 (q, JC-F = 34.1 Hz) ppm. F NMR (376 MHz,
CDCl3): δ -63.5 (d, JH-F = 6.8 Hz, 3F) ppm. The spectral data are in accordance with
the literature report.5g
2l: (E)-1-bromo-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (hexane). White
solid, 35 mg, 70%. Rf = 0.65 (hexane). 1H NMR (400 MHz, CDCl3): δ 7.53 (d, JH-H
=
8.4 Hz, 2H), 7.32 (d, JH-H = 8.4 Hz, 2H), 7.09 (dq, JH-H = 16.1 Hz, JH-F = 1.9 Hz, 1H),
6.20 (dq, JH-H = 16.1 Hz, JH-F = 6.4 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ
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136.6 (q, JC-F = 6.8 Hz), 132.5, 132.3, 129.1, 124.4, 123.5 (q, JC-F = 269.0 Hz), 116.7 (q,
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JC-F = 34.1 Hz) ppm. F NMR (376 MHz, CDCl3): δ -63.5 (d, JH-F = 6.5 Hz, 3F) ppm.
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The spectral data are in accordance with the literature report.5g
2m: (E)-1-methoxy-3-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to
the general procedure and purified by flash column chromatography (5%
EtOAc/hexane). Pale-yellow oil, 32 mg, 80%. Rf = 0.62 (10% EtOAc/hexane). 1H
NMR (400 MHz, CDCl3): δ 7.31 (t, JH-H = 7.9 Hz, 1H), 7.12 (dq, JH-H = 16.1 Hz, JH-F
=
2.0 Hz, 1H), 7.05 (d, JH-H = 7.7 Hz, 1H), 6.97 (s, 1H), 6.93 (dd, JH-H = 8.2, 2.2 Hz, 1H),
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6.20 (dq, JH-H = 16.1 Hz, JH-F = 6.5 Hz, 1H), 3.84 (s, 3H) ppm. C NMR (100 MHz,
CDCl3): δ 160.1, 137.7 (q, JC-F = 6.9 Hz), 134.9, 130.1, 123.7 (q, JC-F = 269.0 Hz),
120.3, 116.3 (q, JC-F = 33.8 Hz), 115.8, 112.9, 55.5 ppm. 19F NMR (376 MHz, CDCl3):
δ -63.4 (dd, JH-F = 6.8, 2.2 Hz, 3F) ppm. The spectral data are in accordance with the
literature report.25
2n: (E)-3-(3,3,3-trifluoroprop-1-en-1-yl)phenol. Prepared according to the general
procedure and purified by flash column chromatography (15% EtOAc/hexane).
Brown oil, 26 mg, 70%. Rf = 0.48 (20% EtOAc/hexane). 1H NMR (400 MHz, CDCl3):
δ 7.26 (t, JH-H = 7.9 Hz, 1H), 7.09 (dq, JH-H = 16.1 Hz, JH-F = 2.1 Hz, 1H), 7.03 (d, JH-H
= 7.7 Hz, 1H), 6.93 (s, 1H), 6.85 (dd, JH-H = 8.0, 2.3 Hz, 1H), 6.17 (dq, JH-H = 16.1 Hz,
JH-F = 6.5 Hz, 1H), 5.02 (brs, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ 156.1, 137.4 (q,
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=
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34.0 Hz), 114.1 ppm. 19F NMR (376 MHz, CDCl3): δ -63.5 (d, JH-F = 7.0 Hz, 3F) ppm.
The spectral data are in accordance with the literature report.5j
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2o: (E)-1-methoxy-2-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to
the general procedure and purified by flash column chromatography (5%
EtOAc/hexane). Pale-yellow oil, 31 mg, 78%. Rf = 0.60 (10% EtOAc/hexane). 1H
NMR (400 MHz, CDCl3): δ 7.45−7.41 (m, 2H), 7.37−7.33 (m, 1H), 6.97 (t, JH-H = 7.5
Hz, 1H), 6.93 (d, JH-H = 8.3 Hz, 1H), 6.34 (dq, JH-H = 16.3 Hz, JH-F = 6.6 Hz, 1H), 3.89
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(s, 3H) ppm. C NMR (100 MHz, CDCl3): δ 158.1, 133.2 (q, JC-F = 7.0 Hz), 131.3,
128.8, 124.1 (q, JC-F = 269.1 Hz), 122.5, 120.9, 116.6 (q, JC-F = 33.3 Hz), 111.2, 55.6
ppm. 19F NMR (376 MHz, CDCl3): δ -63.3 (dd, JH-F = 6.6, 2.0 Hz, 3F) ppm. The
spectral data are in accordance with the literature report.5j
2p: (E)-1-methyl-2-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (pentane). Colorless
oil, 112 mg, 60% (1 mmol scale). Rf = 0.75 (hexane). 1H NMR (400 MHz, CDCl3): δ
7.49−7.42 (m, 2H), 7.33−7.29 (m, 1H), 7.27−7.23 (m, 2H), 6.13 (dq, JH-H = 16.0 Hz,
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JH-F = 6.5 Hz, 1H), 2.42 (s, 3H) ppm. C NMR (100 MHz, CDCl3): δ 137.1, 135.6 (q,
JC-F = 6.7 Hz), 132.7, 130.9, 129.9, 126.6, 126.3, 123.7 (q, JC-F = 269.4 Hz), 117.2 (q,
JC-F = 33.5 Hz), 19.7 ppm. 19F NMR (376 MHz, CDCl3): δ -63.4 (dd, JH-F = 6.6, 2.1 Hz,
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3F) ppm. The spectral data are in accordance with the literature report.25
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2q: (E)-2-(3,3,3-trifluoroprop-1-en-1-yl)aniline. Prepared according to the general
procedure and purified by flash column chromatography (10% EtOAc/hexane). Light
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brown solid, 24 mg, 65%. Rf = 0.65 (20% EtOAc/hexane). H NMR (400 MHz,
CDCl3): δ 7.30−7.23 (m, 2H), 7.18 (t, JH-H = 7.5 Hz, 1H), 6.80 (t, JH-H = 7.5 Hz, 1H),
6.72 (d, JH-H = 8.0 Hz, 1H), 6.13 (dq, JH-H = 16.0 Hz, JH-F = 6.5 Hz, 1H), 3.82 (brs, 2H)
ppm. 13C NMR (100 MHz, CDCl3): δ 144.9, 133.5 (q, JC-F = 6.7 Hz), 131.1, 128.1,
123.8 (q, JC-F = 268.8 Hz), 119.6, 119.4, 116.9, 116.8 (q, JC-F = 33.7 Hz) ppm. 19F NMR
(376 MHz, CDCl3): δ -63.2 (d, JH-F = 6.5 Hz, 3F) ppm. The spectral data are in
accordance with the literature report.25
2r: (E)-1,2-dimethyl-4-(3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to
the general procedure and purified by flash column chromatography (pentane).
Pale-yellow oil, 130 mg, 65% (1 mmol scale). Rf = 0.70 (hexane). 1H NMR (400 MHz,
CDCl3): δ 7.20−7.11 (m, 3H), 7.07 (dq, JH-H = 16.1 Hz, JF-H = 2.2 Hz, 1H), 6.13 (dq,
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JH-H = 16.1 Hz, JH-F = 6.6 Hz, 1H), 2.26 (s, 6H) ppm. C NMR (100 MHz, CDCl3): δ
139.2, 137.8 (q, JC-F = 6.7 Hz), 137.3, 131.2, 130.3, 128.9, 125.2, 124.0 (q, JC-F = 268.5
Hz), 114.6 (q, JC-F = 33.6 Hz), 19.8, 19.8 ppm. 19F NMR (376 MHz, CDCl3): δ -63.1 (d,
JH-F = 6.4 Hz, 3F) ppm. The spectral data are in accordance with the literature report.5i
2s: (E)-9-(3,3,3-trifluoroprop-1-en-1-yl)phenanthrene. Prepared according to the
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general procedure and purified by flash column chromatography (hexane). White
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solid, 45 mg, 83%. Rf = 0.48 (hexane). 1H NMR (400 MHz, CDCl3): δ 8.75 (d, J H-H
=
=
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8.2 Hz, 1H), 8.68 (d, J H-H= 8.2 Hz, 1H), 8.07 (d, J H-H= 7.8 Hz, 1H), 7.96 (dq, JH-H
16.1 Hz, JH-F = 1.9 Hz, 1H), 7.92 (d, J H-H= 7.6 Hz, 1H), 7.88 (s, 1H), 7.74–7.61 (m, 4H),
6.37 (dq, JH-H = 16.1 Hz, JH-F = 6.5 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ
136.1 (q, JC-F = 6.7 Hz), 131.2, 131.1, 130.5, 130.3, 130.0, 129.2, 127.7, 127.2, 127.2,
127.2, 126.4, 124.3, 123.4, 123.4 (q, JC-F = 269.7 Hz), 122.8, 119.5 (q, JC-F = 33.6 Hz)
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ppm. F NMR (376 MHz, CDCl3): δ -63.5 (d, JH-F = 6.7 Hz, 3F) ppm. The H NMR
and 19F NMR spectral data are in accordance with the literature report.4d
2t: 1,4-bis((E)-3,3,3-trifluoroprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (hexane). White
1
solid, 40 mg, 75%. Rf = 0.42 (hexane). H NMR (400 MHz, CDCl3): δ 7.48 (s, 4H),
7.15 (dq, JH-H = 16.2 Hz, JH-F = 2.1 Hz, 2H), 6.25 (dq, JH-H = 16.2 Hz, JH-F = 6.5 Hz, 2H)
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ppm. C NMR (100 MHz, CDCl3): δ 136.8 (q, JC-F = 6.7 Hz), 135.1, 128.2, 123.5 (q,
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JC-F = 268.9 Hz), 117.2 (q, JC-F = 34.1 Hz) ppm. F NMR (376 MHz, CDCl3): δ -63.5
(d, JH-F = 6.7 Hz, 3F) ppm. The 1H NMR and 19F NMR spectral data are in accordance
with the literature report.27
2u: (E)-2-(3,3,3-trifluoroprop-1-en-1-yl)pyridine. Prepared according to the general
procedure and purified by flash column chromatography (25% Et2O/hexane).
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Pale-yellow oil, 52 mg, 30% (1 mmol scale). Rf = 0.60 (20% EtOAc/hexane). H
NMR (400 MHz, CDCl3): δ 8.64 (d, JH-H = 4.2 Hz, 1H), 8.64 (td, JH-H = 7.7, 1.7 Hz, 1H),
7.35 (d, JH-H = 7.7 Hz, 1H), 7.28 (dd, JH-H = 7.6, 5.3 Hz, 1H), 7.18 (dq, JH-H = 15.7 Hz,
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JH-F = 2.0 Hz, 1H), 6.81 (dq, JH-H = 15.7 Hz, JH-F = 6.9 Hz, 1H) ppm. C NMR (100
MHz, CDCl3): δ 151.9, 150.2, 137.0, 136.8 (q, JC-F = 6.6 Hz), 124.4, 124.0, 123.6 (q,
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JC-F = 268.8 Hz), 120.2 (q, JC-F = 34.1 Hz) ppm. F NMR (376 MHz, CDCl3): δ-63.9
(dd, JH-F = 6.8, 2.2 Hz) ppm. The spectral data are in accordance with the literature
report.5g
2v: (E)-3-(3,3,3-trifluoroprop-1-en-1-yl)thiophene. Prepared according to the general
procedure and purified by flash column chromatography (pentane). Colorless oil, 70
mg, 40% (1 mmol scale). Rf = 0.72 (hexane). 1H NMR (400 MHz, CDCl3): δ 7.42 (d,
JH-H = 2.4 Hz, 1H), 7.35 (dd, J H-H= 5.0, 3.0 Hz, 1H), 7.24 (dd, J H-H= 5.1, 1.0 Hz, 1H),
7.15 (dq, JH-H = 16.1 Hz, JH-F = 2.1 Hz, 1H), 6.05 (dq, JH-H = 16.1 Hz, JH-F = 6.6 Hz, 1H)
ppm. 13C NMR (100 MHz, CDCl3): δ 136.4, 131.5 (q, JC-F = 7.0 Hz), 127.3, 127.1,
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125.0, 123.8 (q, JC-F = 268.7 Hz), 115.6 (q, JC-F = 33.9 Hz) ppm. F NMR (376 MHz,
CDCl3): δ -63.3 (d, JH-F = 7.0 Hz) ppm. The spectral data are in accordance with the
literature report.5e
2w: (E)-(((4,4,4-trifluorobut-2-en-1-yl)oxy)methyl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (5% EtOAc/hexane),
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containing 4% of inseparable side product 3w. Colorless oil, 18 mg, 43%. Rf = 0.70
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(10% EtOAc/hexane). H NMR (400 MHz, CDCl3): δ 7.39–7.30 (m, 5H), 6.44
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(doublet of octuplets, JH-H = 15.8 Hz, JH-F = 2.0 Hz, 1H), 6.03–5.92 (m, 1H), 4.58 (s,
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2H), 4.15–4.11 (m, 2H) ppm. C NMR (100 MHz, CDCl3): δ 137.6, 136.6 (q, JC-F
=
6.4 Hz), 128.7, 128.1, 127.8, 123.2 (q, JC-F = 269.2 Hz), 118.9 (q, JC-F = 34.1 Hz), 73.1,
67.9 ppm. 19F NMR (376 MHz, CDCl3): δ -64.3 (m, 3F) ppm. The spectral data are in
accordance with the literature report.28
2x: (E)-1,1,1-trifluorotridec-2-ene. Prepared according to the general procedure and
purified by flash column chromatography (hexane), obtained as an inseparable
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mixture with 3x (2x:3x = 2.4:1). Colorless oil, 24 mg, 35%. Rf = 0.85 (hexane). H
NMR (400 MHz, CDCl3): δ 6.42–6.34 (m, 1H), 5.64–5.56 (m, 1H), 2.18–2.11 (m, 2H),
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1.45–1.27 (m, 16H), 0.88 (t, JH-H = 6.8 Hz, 3H) ppm. C NMR (100 MHz, CDCl3): δ
141.0 (q, JC-F = 6.5 Hz), 123.3 (q, JC-F = 268.8 Hz), 118.4 (q, JC-F = 33.1 Hz), 32.1, 31.6,
29.7, 29.7, 29.5, 29.5, 29.2, 28.1, 22.8, 14.3 ppm. 19F NMR (376 MHz, CDCl3): δ
-63.9 (m, 3F) ppm. The spectral data are in accordance with the literature report.8d
6a: (E)-(3,3,3-trifluoro-2-methylprop-1-en-1-yl)benzene. Prepared according to the
general procedure and purified by flash column chromatography (pentane), containing
5% of inseparable isomer Z-6a. Colorless oil, 61.5 mg (1 mmol scale), 33%. Rf = 0.68
(hexane). 1H NMR (400 MHz, CDCl3): δ 7.44–7.34 (m, 5H), 7.08 (s, 1H), 2.04 (s, 3H)
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ppm. C NMR (100 MHz, CDCl3): δ 134.7, 131.4 (q, JC-F = 6.2 Hz), 129.3, 128.6,
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128.4, 126.4 (q, JC-F = 28.8 Hz), 124.7 (q, JC-F = 272.7 Hz), 12.3 ppm. F NMR (376
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MHz, CDCl3): δ -69.5 (s, 3F) ppm. The H NMR and F NMR spectral data are in
accordance with the literature report.5g
7a:
2-(3,3,3-trifluoro-2-(trifluoromethyl)prop-1-en-1-yl)naphthalene.
Prepared
according to the general procedure and purified by flash column chromatography
(hexane). White solid, 49 mg, 85%. Rf = 0.70 (hexane). 1H NMR (400 MHz, CDCl3):
δ 7.93–7.86 (m, 4H), 7.80 (s, 1H), 7.60–7.51 (m, 3H) ppm. 13C NMR (100 MHz,
CDCl3): δ 143.4 (m), 134.0, 132.8, 130.4, 128.8, 128.5, 128.5, 128.0, 127.9, 127.1,
125.6 (q, JC-F = 2.6 Hz), 121.7 (qq, JC-F = 273.2, 2.2 Hz), 121.1 (q, JC-F = 274.8 Hz),
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120.4 (quint, JC-F = 32.5 Hz) ppm. F NMR (376 MHz, CDCl3): δ -57.5 (q, JF-F = 7.2
Hz, 3F), -63.5 (q, JF-F = 7.2 Hz, 3F) ppm. IR (KBr): 1657, 1363, 1295, 1219, 1129,
969 cm-1. HRMS m/z (EI): calcd. for C14H8F6 [M]+: 290.0525; found: 290.0526.
7b: 1-methoxy-4-(3,3,3-trifluoro-2-(trifluoromethyl)prop-1-en-1-yl)benzene. Prepared
according to the general procedure and purified by flash column chromatography (5%
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EtOAc/hexane). Pale-yellow oil, 26 mg, 48%. Rf = 0.60 (10% EtOAc/hexane). H
NMR (400 MHz, CDCl3): δ 7.51 (s, 1H), 7.45 (d, JH-H = 8.8 Hz, 2H), 6.94 (d, JH-H = 8.8
Hz, 2H), 3.86 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3): δ 161.9, 142.7 (m), 132.2 (q,
JC-F = 2.8 Hz), 123.2, 122.0 (qq, JC-F = 272.7, 2.5 Hz), 121.4 (q, JC-F = 274.3 Hz), 117.3
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