Stereoselective synthesis of α-trifluoromethyl enones by AuI/CuI-co-catalyzed tandem 1,3-acyloxy migration/trifluoromethylation reaction of propargyl acetates

Article abstract of DOI:10.1002/ejoc.201403115

Au^I/Cu^I-co-catalyzed tandem 1,3-acyloxy migration/trifluoromethylation reaction of propargyl esters to give α-trifluoromethyl enones in moderate yields and with excellent stereoselectivity is described. It is proposed that the reacti

Full text of DOI:10.1002/ejoc.201403115

FULL PAPER
DOI: 10.1002/ejoc.201403115
Stereoselective Synthesis of α-Trifluoromethyl Enones by
AuI/CuI-Co-Catalyzed Tandem 1,3-Acyloxy Migration/Trifluoromethylation
Reaction of Propargyl Acetates
Yun-Long Ji,[a] Jin-Hong Lin,*[a] Ji-Chang Xiao,*[a] and Yu-Cheng Gu[b]
Keywords: Synthetic methods / Trifluoromethylation / Gold / Copper / Stereooselectivity / Enones
AuI/CuI-co-catalyzed tandem 1,3-acyloxy migration/tri-
fluoromethylation reaction of propargyl esters to give α-tri-
fluoromethyl enones in moderate yields and with excellent
stereoselectivity is described. It is proposed that the reaction
proceeds through the 1,3-acyloxy migration of the propargyl
esters catalyzed by AuI to produce an allenic intermediate,
followed by its trifluoromethylation to give the final product.
ucts (Scheme 1, Equation 1).[7] We have also found that the
use of electrophilic trifluoromethylating reagent (S-tri-
fluoromethyl)diphenyl sulfonium triflate results in the same
conversion in the presence of copper powder (Scheme 1,
Equation 2).[8] During the preparation of this manuscript,
Liu and co-workers reported a domino copper-catalyzed
trifluoromethylated Meyer–Schuster rearrangement reac-
tion of propargyl alcohols with Togni’s reagent II that leads
Introduction
Compounds that contain a trifluoromethyl moiety have
proved to be very important in pharmaceuticals and agro-
chemicals owing to its unique properties, such as metabolic
stability, strong electronegativity, and good lipophilicity.[1]
Consequently, intensive research efforts have been made
towards the development of versatile approaches for incor-
poration of trifluoromethyl functionality.[2] In recent years,
transition-metal-mediated or -catalyzed trifluoromethyl-
ation reactions have emerged as powerful synthetic tools
because of their high level of functional group tolerance
and mild reaction conditions.[3] However, in these studies,
gold has never been reported to be involved in trifluorome-
thylation reactions except in the trifluoromethylation of
gold complexes.[4] In this paper, we describe the AuI/CuI-
co-catalyzed tandem 1,3-acyloxy migration/trifluoromethyl-
ation reaction of propargyl esters to α-trifluoromethyl en-
ones, which to date has been largely unexplored.[5]
Propargyl esters and halides have been found to be valu-
able building blocks in synthetic chemistry.[6] Trifluoro-
methylation of these intermediates by employing a CuCF3
reagent prepared in advance or generated in situ from nu-
cleophilic trifluoromethyl sources has been reported, but
these processes give trifluoromethyl-allenes as final prod-
[a] Key Laboratory of Organofluorine Chemistry, Shanghai Insti-
tute of Organic Chemistry, Chinese Academy of Sciences,
345 Lingling Road, Shanghai 200032, P. R. China
E-mail: jlin@sioc.ac.cn
jchxiao@sioc.ac.cn
http://xiaojichang.sioc.ac.cn
[b] Syngenta, Jealott’s Hill International Research Centre,
Bracknell, Berkshire, RG42 6EY, UK
Scheme 1. Trifluoromethylation reactions of propargyl halides and
esters; DMF = dimethylformamide.
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201403115.
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Eur. J. Org. Chem. 2014, 7948–7954

Stereoselective Synthesis of α-Trifluoromethyl Enones
to α-trifluoromethyl enone products (Scheme 1, Equa- Table 1. AuI/CuI-co-catalyzed trifluoromethylation reactions of
1a[a]
.
tion 3).[9] However, the transformation works less well for a
1-aryl-substituted substrate (R1 = Ar) than for 1,1-dialkyl-
substituted or 1-alkyl-substituted substrates, and only one
example of a 1-aryl-substituted substrate was described in
34% yield. Furthermore, stereoselectivity is an issue that
remains to be addressed. Interestingly, Sodeoka and co-
workers found that dual catalysis with copper and rhenium
for trifluoromethylation of propargyl alcohols resulted in
Z-selectivity (Scheme 1, Equation 4).[10] It is well known
that propargylic esters undergo 1,3-acyloxy migration cata-
lyzed by gold to give allenic intermediates,[11] which could
applied to a variety of further transformations. In continua-
tion of our research interest into the chemistry of trifluoro-
methylation,[8,12] we have investigated the AuI/CuI-co-cata-
lyzed tandem 1,3-acyloxy migration/trifluoromethylation
reaction of 1-arylpropargyl esters; a transformation that
gives α-trifluoromethyl enones with excellent stereoselec-
tivity (E/Z Ͼ 97:3; Scheme 1, Equation 5).
Entry Au
Cu
Solvent Temp. Yield [%][b]
Results and Discussion
1[c]
2
3
4
5
PPh3AuCl
PPh3AuCl
AuCl
AuCl
AuCl
AuCl
AuCl
AuCl
–
–
–
–
CH3CN
CH3CN
CH3CN
CH2Cl2
CH2Cl2
CH2Cl2
60
60
60
45
45
45
45
45
45
45
45
45
45
45
80
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
0
0
0
Our initial attempts at gold-catalyzed electrophilic tri-
fluoromethylation reactions of propargylic esters in aceto-
nitrile failed, although similar halogenation reactions have
been reported (Table 1, Entries 1–3).[13] In dichloromethane,
a trace amount of desired product was detected by 19F
NMR spectroscopy (Table 1, Entry 4). The presence of
CuTc improved the yield slightly (Table 1, Entry 5). An ex-
amination of the copper source showed that (MeCN)4-
CuPF6 gave better results (Table 1, Entries 7 versus 5 and
6). The use of a AuCl/AgOTf catalytic system instead of
AuCl resulted in a lower yield (Table 1, Entry 8). Other
catalytic systems composed of various gold complexes and
silver triflate were not effective (Table 1, Entries 9–11).
However, we found that a catalytic amount of a ligand was
favorable for this reaction (Table 1, Entries 12 and 13) and
2,2Ј-biquinoline was identified as a suitable ligand (Table 1,
Entry 13). The reaction in 1,2-dichloroethane (DCE) pro-
ceeded much better in 52% yield (Table 1, Entry 14). A rise
in the reaction temperature led to an inferior result (Table 1,
Entry 15), whereas a decrease in temperature gave a slightly
higher yield (Table 1, Entry 16). Gold complex
Ph3PAuNTf2, prepared by anion metathesis between
Ph3PAuCl and AgNTf2, served as a highly efficient and air-
stable catalyst.[14] In our reaction system this catalyst gave
superior results (Table 1, Entry 17). Use of both the gold
trace
11
10
12
5
13
11
8
24
30
52
46
53
64
0
trace
64
68
CuTc
Cu(OTf)2
6
7
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 CH2Cl2
(MeCN)4CuPF6 DCE
(MeCN)4CuPF6 DCE
(MeCN)4CuPF6 DCE
8[d]
9[d]
10[d]
11[d]
PPh3AuCl
IPrAuCl
SIPrAuCl
12[d] ,[e] Ph3PAuCl
13[d] ,[f] Ph3PAuCl
14[f] ,[g] Ph3PAuCl
15[f] ,[g] Ph3PAuCl
16[f] ,[g] Ph3PAuCl
17[f]
18[f]
19[f]
20[f]
Ph3PAuNTf2 (MeCN)4CuPF6 DCE
–
Ph3PAuNTf2
Ph3PAuNTf2 CuOTf
(MeCN)4CuPF6 DCE
–
DCE
DCE
DCE
21[f] ,[h] Ph3PAuNTf2 CuOTf
[a] Reaction conditions: 1a (0.3 mmol, 1.0 equiv.), II (1.0 equiv.),
[Au] (10 mol-%), [Cu] (10 mol-%), in solvent (3 mL). [b] Deter-
mined by 19F NMR spectroscopy. [c] Reagent I (1.0 equiv.) was
used instead of II. [d] AgOTf (10 mol-%) was added. [e] Bathocup-
roin L1 (10 mol-%) was added. [f] 2,2Ј-Biquinoline L2 (10 mol-%)
was added. [g] AgPF6 (10 mol-%) was added. [h] CuOTf (5 mol-%)
was used.
To explore the scope of this trifluoromethylation reaction
and copper complexes were necessary for this conversion, the optimized conditions (Table 1, Entry 21) were applied
and the absence of either significantly suppressed the de- to the reaction of a variety of propargyl esters with Togni’s
sired transformation. This difference indicates that this re- reagent. As shown in Table 2, the reaction proceeded well
action proceeds through a different path relative to that of with a variety of substrates and gave the corresponding tri-
the reported halogenation reaction (Table 1, Entries 18 and fluoromethylation products in moderate yields and with ex-
19).[13] Without the presence of gold complex, substrate 1a cellent stereoselectivity (E/ZϾ97:3). Irrespective of whether
remained intact (Table 1, Entry 18). Without the presence the aryl group at the 1-position contained an electron-with-
of copper complex, the reaction was complex and only trace drawing or electron-donating group, the products were ob-
substrate 1a remained (Table 1, Entry 19). Another copper tained in moderate yields (Table 2, Entries 1–9). Substrates
source, CuOTf, was also suitable, even with a lower loading with electron-donating groups on the 3-phenyl ring were
(Table 1, Entries 20 and 21).
converted smoothly into the expected products (Table 2,
Eur. J. Org. Chem. 2014, 7948–7954
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Y.-L. Ji, J.-H. Lin, J.-C. Xiao, Y.-C. Gu
FULL PAPER
Entries 10–13), whereas the transformations of substrates
The group of Liu has previously described the copper-
with electron-withdrawing groups on 3-phenyl ring were catalyzed trifluoromethylation reaction of propargyl
quite complex. This tandem reaction cannot be applied well alcohols to afford α-trifluoromethyl enones.[9] Unfortu-
to alkyl-substituted substrates (Table 2, Entries 14 and 15). nately, their reaction conditions are not suitable for the tri-
fluoromethylation reaction of propargyl esters, even though
Table 2. AuI/CuI-co-catalyzed trifluoromethylation reaction of
2 equiv. of Togni’s reagent was used (Scheme 2). Therefore,
Liu’s and our protocols are complementary for the tri-
fluoromethylation reaction of different substrates that lead
to α-trifluoromethyl enones.
propargyl acetates[a]
.
Entry
R1
Ph
R2
2, Yield [%][b]
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
2a, 56
2b, 46
2c, 58
2d, 49
2e, 40
2f, 38
2g, 45
2h, 40
2i, 42
2j, 60
2k, 68
2l, 45
2m, 52
2n, 25[c]
2o, 9[c]
Scheme 2. Attempts at the trifluoromethylation reaction of prop-
argyl acetate by using a previously described method.[9]
4-Me-C6H4
4-Ph-C6H4
2-Cl-C6H4
3-Cl-C6H4
3-F-C6H4
4-Br-C6H4
3,5-Br2-C6H3
4-MeO2C-C6H4
Ph
Ph
Ph
Ph
Ph
The trifluoromethylation of propargyl esters might in-
volve a radical process. Well-known radical scavenger
2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) can sup-
press the desired reaction completely (Scheme 3). A radical
trap reaction gave TEMPO-CF3 complex 3 in 40% yield as
determined by 19F NMR spectroscopy.
9
Ph
10
11
12
13
14
15
4-Ph-C6H4
4-MeO-C6H4
3-Me-C6H4
4-pentyl-C6H4
nBu
Cy
Ph
[a] Propargyl acetate (0.3 mmol, 1.0 equiv.), II (1 equiv.),
Ph3PAuNTf2 (10%), CuOTf (5%) and 2,2Ј-biquinoline (10%) in
DCE (3 mL) at room temperature. [b] Isolated yields. [c] Deter-
mined by 19F NMR spectroscopy.
The structure of product 2i was determined by single-
crystal X-ray diffraction (Figure 1).[15] The structures of the
other products were determined by analogy.
Scheme 3. Examination of a radical process.
On the basis of our and related reports,[2h,2i,11] we pro-
pose the reaction mechanism as shown in Scheme 4. The
redox reaction of Togni’s reagent with CuI affords CuII (in-
termediate A) and a trifluoromethyl radical. The trifluoro-
methyl radical is trapped by allenic intermediate B, which
Scheme 4. Proposed mechanism for the trifluoromethylation reac-
tion of propargyl acetates.
Figure 1. Crystal structure of 2i.
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Eur. J. Org. Chem. 2014, 7948–7954

Stereoselective Synthesis of α-Trifluoromethyl Enones
689 cm–1. HRMS (EI): calcd. for C17H13ClO2 284.0604; found
284.0601.
is generated from the propargyl esters in the presence of
gold, to selectively give radical intermediate C with the CF3
group trans to Ar (E-selective isomer). The trifluoromethyl
radical should approach the more electron-rich enolic C–C
double bond from the less-hindered face. Subsequent oxid-
ization of radical intermediate C by CuII releases CuI and
cationic intermediate D, which is transformed into the final
product.
1-(3-Chlorophenyl)-3-phenylprop-2-yn-1-yl Acetate (1e): Yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.59 (s, 1 H), 7.55–7.42 (m, 3
H), 7.40–7.27 (m, 5 H), 6.66 (s, 1 H), 2.14 (s, 3 H) ppm. 13C NMR
(101 MHz, CDCl3): δ = 169.58, 139.16, 134.56, 131.94, 129.99,
129.10, 129.01, 128.35, 127.86, 125.91, 121.82, 87.48, 84.98, 65.29,
21.02 ppm. IR (KBr): ν = 3061, 2230, 1740, 1368, 1215, 1014, 788,
˜
755, 688 cm–1. HRMS (EI): calcd. for C17H13ClO2 284.0604; found
284.0602.
1-(3-Fluorophenyl)-3-phenylprop-2-yn-1-yl Acetate (1f): Yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.53–7.44 (m, 2 H), 7.41–7.27
(m, 6 H), 7.14–6.99 (m, 1 H), 6.68 (s, 1 H), 2.15 (s, 3 H) ppm. 13C
NMR (101 MHz, CDCl3): δ = 169.71, 162.77 (d, J = 246.8 Hz),
139.50 (d, J = 7.4 Hz), 131.93, 130.24 (d, J = 8.2 Hz), 128.97,
128.32, 123.35 (d, J = 3.0 Hz), 121.79, 115.91 (d, J = 21.2 Hz),
114.75 (d, J = 22.6 Hz), 87.33, 84.90, 65.29 (d, J = 2.0 Hz),
Conclusions
In conclusion, we have described AuI/CuI-cocatalyzed
tandem 1,3-acyloxy migration/trifluoromethylation reac-
tions of 1-arylpropargyl esters to give α-trifluoromethyl en-
ones with excellent stereoselectivity and in moderate yields.
Both gold and copper complexes were necessary for this
transformation. To the best of our knowledge, this is the
first report of the trifluoromethylation reaction of organic
intermediates in which gold is involved.
21.08 ppm. IR (KBr): ν = 3064, 2230, 2228, 1742, 1594, 1489, 1215,
˜
1014, 755, 688 cm–1. HRMS (EI): calcd. for C17H13FO2 268.0900;
found 268.0906.
1-(4-Bromophenyl)-3-phenylprop-2-yn-1-yl Acetate (1g): Yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.55–7.50 (m, 2 H), 7.49–7.45
(m, 4 H), 7.34–7.29 (m, 3 H), 6.65 (s, 1 H), 2.12 (s, 3 H) ppm. 13C
NMR (101 MHz, CDCl3): δ = 169.68, 136.25, 131.89, 131.84,
129.48, 128.95, 128.31, 123.09, 121.82, 87.36, 85.02, 65.40,
Experimental Section
1
General Information: H, 13C and 19F NMR spectra were recorded
with a 500 MHz, 400 MHz or 300 MHz NMR spectrometer. Data
for 1H, 13C and 19F NMR were recorded as follows: chemical shift,
multiplicity (s = singlet, d = doublet, t = triplet, m = multiplet, q
= quartet). Mass spectra were obtained on a GC-MS. HRMS data
were recorded in EI or ESI mode.
21.07 ppm. IR (KBr): ν = 3056, 2229, 1738, 1487, 1368, 1217, 1010,
˜
818, 754, 689 cm–1. HRMS (EI): calcd. for C17H13BrO2 328.0099;
found 328.0104.
1-(3,5-Dibromophenyl)-3-phenylprop-2-yn-1-yl Acetate (1h): White
1
solid, m.p. 73 °C. H NMR (400 MHz, CDCl3): δ = 7.69–7.63 (m,
General Procedure for the Preparation of Propargyl Acetates: Prop-
argyl acetates were synthesized according to the procedure reported
in literature.[12]
3 H), 7.54–7.44 (m, 2 H), 7.42–7.29 (m, 3 H), 6.60 (s, 1 H), 2.16 (s, 3
H) ppm. 13C NMR (101 MHz, CDCl3): δ = 169.46, 140.84, 134.52,
131.95, 129.49, 129.13, 128.34, 123.10, 121.52, 87.92, 84.20, 64.49,
21.00 ppm. IR (KBr): ν = 3073, 2962, 2927, 2232, 1741, 1559, 1214,
˜
1,3-Diphenylprop-2-yn-1-yl Acetate (1a): Colorless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.64–7.56 (m, 2 H), 7.50–7.45 (m, 2 H),
7.43–7.33 (m, 3 H), 7.33–7.24 (m, 3 H), 6.70 (s, 1 H), 2.11 (s, 3
H) ppm.
1014, 855, 755, 737, 688 cm–1. HRMS (EI): calcd. for C17H12Br2O2
405.9204; found 405.9206.
Methyl 4-(1-Acetoxy-3-phenylprop-2-yn-1-yl)benzoate (2i): Yellow
oil. 1H NMR (400 MHz, CDCl3): δ = 8.10–8.03 (m, 2 H), 7.70–
7.61 (m, 2 H), 7.52–7.42 (m, 2 H), 7.36–7.27 (m, 3 H), 6.72 (s, 1
H), 3.91 (s, 3 H), 2.14 (s, 3 H) ppm. 13C NMR (101 MHz, CDCl3):
δ = 169.64, 166.53, 141.86, 131.90, 130.57, 129.97, 128.97, 128.30,
3-Phenyl-1-(p-tolyl)prop-2-yn-1-yl Acetate (1b): Yellow oil. 1H
NMR (400 MHz, CDCl3): δ = 7.62–7.46 (m, 4 H), 7.41–7.28 (m, 3
H), 7.26–7.21 (m, 2 H), 6.72 (s, 1 H), 2.39 (s, 3 H), 2.13 (s, 3
H) ppm. 13C NMR (101 MHz, CDCl3): δ = 169.86, 138.93, 134.33,
131.92, 129.39, 128.77, 128.29, 127.84, 122.20, 86.89, 85.83, 66.02,
127.58, 121.78, 87.55, 84.88, 65.46, 52.21, 21.03 ppm. IR (KBr): ν
˜
= 2952, 2230, 1721, 1275, 1216, 1106, 1015, 756, 690 cm–1. HRMS
(EI): calcd. for C19H16O4 308.1049; found 308.1050.
21.25, 21.16 ppm. IR (KBr): ν = 3055, 2924, 2229, 2202, 1739,
˜
1490, 1368, 1219, 1012, 815, 755, 690 cm–1. HRMS (EI): calcd. for
C18H16O2 264.1150; found 264.1147.
3-([1,1Ј-Biphenyl]-4-yl)-1-phenylprop-2-yn-1-yl Acetate (1j): Yellow
solid, m.p. 110 °C. 1H NMR (400 MHz, CDCl3): δ = 7.66–7.51 (m,
8 H), 7.51–7.30 (m, 6 H), 6.72 (s, 1 H), 2.14 (s, 3 H) ppm. 13C
NMR (101 MHz, CDCl3): δ = 169.88, 141.53, 140.18, 137.14,
132.35, 128.99, 128.86, 128.72, 127.83, 127.73, 127.03, 126.95,
1-([1,1Ј-Biphenyl]-4-yl)-3-phenylprop-2-yn-1-yl Acetate (1c): Yellow
oil. 1H NMR (400 MHz, CDCl3): δ = 7.71–7.55 (m, 6 H), 7.52–
7.47 (m, 2 H), 7.47–7.40 (m, 2 H), 7.39–7.28 (m, 4 H), 6.75 (s, 1
H), 2.14 (s, 3 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 169.86,
141.97, 140.52, 136.13, 131.94, 128.84, 128.83, 128.30, 127.58,
127.47, 127.19, 122.09, 87.16, 85.57, 65.90, 21.18 ppm. IR (KBr):
120.93, 86.93, 86.19, 66.14, 21.19 ppm. IR (KBr): ν = 3062, 3033,
˜
2300, 1739, 1486, 1369, 1220, 1013, 951, 840, 763, 697 cm–1. HRMS
(EI): calcd. for C23H18O2 326.1307; found 326.1310.
ν = 3056, 3031, 2229, 1738, 1487, 1218, 1008, 754, 691 cm–1.
˜
HRMS (EI): calcd. for C23H18O2 326.1307; found 326.1310.
3-(4-Methoxyphenyl)-1-phenylprop-2-yn-1-yl Acetate (1k): Yellow
oil. 1H NMR (400 MHz, CDCl3): δ = 7.66–7.55 (m, 2 H), 7.48–
1-(2-Chlorophenyl)-3-phenylprop-2-yn-1-yl Acetate (1d): Yellow so-
1
lid, m.p. 73 °C. H NMR (400 MHz, CDCl3): δ = 7.87–7.83 (m, 1 7.31 (m, 5 H), 6.88–6.78 (m, 2 H), 6.70 (s, 1 H), 3.79 (s, 3 H), 2.12
H), 7.51–7.46 (m, 2 H), 7.44–7.39 (m, 1 H), 7.38–7.28 (m, 5 H),
(s, 3 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 169.84, 159.98,
6.98 (s, 1 H), 2.15 (s, 3 H) ppm. 13C NMR (101 MHz, CDCl3): δ 137.37, 133.43, 128.86, 128.64, 127.77, 114.13, 113.89, 87.08, 84.25,
= 169.43, 134.54, 133.45, 131.93, 130.20, 129.80, 129.50, 128.85,
128.24, 127.10, 121.94, 87.32, 84.54, 63.31, 20.86 ppm. IR (KBr):
ν = 3063, 2229, 1742, 1474, 1369, 1215, 1214, 1014, 954, 913, 752,
˜
66.22, 55.26, 21.15 ppm. IR (KBr): ν = 2935, 2838, 2228, 1736,
˜
1605, 1509, 1218, 1014, 831, 697 cm–1. HRMS (EI): calcd. for
C18H16O3 280.1099; found 280.1102.
Eur. J. Org. Chem. 2014, 7948–7954
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7951

Y.-L. Ji, J.-H. Lin, J.-C. Xiao, Y.-C. Gu
FULL PAPER
1-Phenyl-3-(m-tolyl)prop-2-yn-1-yl Acetate (1l): Yellow oil. 1H H), 7.43 (tt, J = 7.4, 1.4 Hz, 1 H), 7.34–7.22 (m, 3 H), 7.17–7.07
NMR (400 MHz, CDCl3): δ = 7.64–7.56 (m, 2 H), 7.44–7.35 (m, 3 (m, 2 H), 6.96 (td, J = 7.6, 0.6 Hz, 1 H) ppm. 19F NMR (376 MHz,
H), 7.33–7.26 (m, 2 H), 7.22–7.17 (m, 1 H), 7.16–7.12 (m, 1 H),
6.69 (s, 1 H), 2.31 (s, 3 H), 2.12 (s, 3 H) ppm. 13C NMR (101 MHz,
CDCl3): δ = –63.19 (s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ
= 191.74, 135.50, 134.81 (q, J = 6.1 Hz), 134.13, 133.79, 131.06,
CDCl3): δ = 169.86, 137.98, 137.19, 132.49, 129.70, 128.97, 128.94, 131.01, 130.73 (q, J = 30.2 Hz), 130.52, 129.48, 129.28, 128.59,
128.68, 128.18, 127.82, 121.85, 87.24, 85.17, 66.11, 21.18 ppm. IR 126.79, 121.91 (q, J = 274.7 Hz) ppm. IR (KBr): ν = 3065, 1668,
˜
(KBr): ν = 3063, 3035, 2922, 2234, 1737, 1368, 1218, 1013, 949, 1594, 1292, 1162, 1058, 757, 717, 687 cm–1. HRMS (EI): calcd. for
˜
784, 691 cm–1. HRMS (EI): calcd. for C18H16O2 264.1150; found
264.1147.
C16H10ClF3O 310.0372; found 310.0369.
(E)-3-(3-Chlorophenyl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-one
1
3-(4-Pentylphenyl)-1-phenylprop-2-yn-1-yl Acetate (1m): Yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.62–7.57 (m, 2 H), 7.46–7.30
(m, 5 H), 7.14–7.09 (m, 2 H), 6.70 (s, 1 H), 2.59 (t, J = 7.6 Hz, 2
H), 2.12 (s, 3 H), 1.64–1.55 (m, 2 H), 1.42–1.21 (m, 4 H), 0.88 (t,
J = 6.9 Hz, 3 H) ppm. 13C NMR (101 MHz, CDCl3): δ = 169.83,
144.00, 137.28, 131.82, 128.87, 128.63, 128.37, 127.79, 119.18,
87.29, 84.87, 66.15, 35.84, 31.37, 30.86, 22.48, 21.14, 13.99 ppm.
(2e): Yellow oil. H NMR (400 MHz, CDCl3): δ = 7.90–7.83 (m, 2
H), 7.51 (tt, J = 7.4, 1.4 Hz, 1 H), 7.45–7.40 (m, 1 H), 7.39–7.33
(m, 2 H), 7.24–7.21 (m, 1 H), 7.19–7.15 (m, 1 H), 7.11–7.08 (m, 2
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –62.88 (s, 3 F) ppm.
13C NMR (101 MHz, CDCl3): δ = 192.08, 135.32 (q, J = 6.0 Hz),
135.23, 134.65, 134.48, 133.67, 130.27 (q, J = 30.2 Hz), 130.07,
129.92, 129.49, 128.85, 127.26, 122.00 (q, J = 274.6 Hz) ppm. IR
IR (KBr): ν = 2956, 2928, 2857, 2230, 1740, 1509, 1455, 1386, 1220,
˜
(KBr): ν = 3066, 2320, 1665, 1369, 1287, 1214, 1160, 927, 908,
˜
1013, 697 cm–1. HRMS (EI): calcd. for C22H24O2 320.1776; found
320.1780.
785, 683, 616 cm–1. HRMS (EI): calcd. for C16H10ClF3O 310.0372;
found 310.0377.
General Trifluoromethylation Procedure for the Propargyl Acetates:
PPh3AuNTf2 (22.2 mg, 0.03 mmol), CuOTf (3.2 mg, 0.015 mmol),
Togni’s reagent II (94.8 mg, 0.3 mmol), propargyl acetate
(0.3 mmol), and DCE (3 mL) were added sequentially to a flame-
dried tube under argon. The tube was then sealed and the resulting
mixture was stirred at room temperature. When the reaction was
complete, as monitored by 19F NMR spectroscopy, the crude reac-
tion mixture was filtered through a short pad of silica gel and
eluted with CH2Cl2. After evaporation, the residue was purified by
chromatography on silica gel (eluent: petroleum ether/dichloro-
methane) to afford the desired product.
(E)-3-(3-Fluorophenyl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-one
(2f): Colorless oil. H NMR (400 MHz, CDCl3): δ = 7.91–7.85 (m,
1
2 H), 7.52 (tt, J = 7.4, 1.6 Hz, 1 H), 7.44 (s, 1 H), 7.41–7.34 (m, 2
H), 7.19–7.11 (m, 1 H), 7.06–7.00 (m, 1 H), 6.98–6.87 (m, 2
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –62.87 (s, 3 F), –110.80
to –110.89 (m, 1 F). 13C NMR (101 MHz, CDCl3): δ = 192.13,
162.43 (d, J = 247.7 Hz), 135.40 (qd, J = 5.9, 2.6 Hz), 135.20,
134.49, 134.01 (d, J = 7.9 Hz), 130.34 (d, J = 8.3 Hz), 130.17 (q, J
= 29.9 Hz), 129.53, 128.85, 125.22 (d, J = 2.9 Hz), 122.01 (q, J =
274.5 Hz), 117.08 (d, J = 21.2 Hz), 116.13 (d, J = 22.7 Hz) ppm.
IR (KBr): ν = 3069, 1665, 1585, 1234, 1123, 789, 683 cm–1. HRMS
˜
(E)-1,3-Diphenyl-2-(trifluoromethyl)prop-2-en-1-one (2a): Colorless
oil. 1H NMR (400 MHz, CDCl3): δ = 7.93–7.86 (m, 2 H), 7.53–
7.46 (m, 2 H), 7.39–7.31 (m, 2 H), 7.29–7.13 (m, 5 H) ppm. 19F
NMR (376 MHz, CDCl3): δ = –62.61 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 192.65, 136.91 (q, J = 5.9 Hz), 135.38,
134.26, 131.94, 130.12, 129.58, 129.53, 128.75, 128.69 (q, J =
(EI): calcd. for C16H10F4O 294.0668; found 294.0669.
(E)-3-(4-Bromophenyl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-one
(2g): White solid, m.p. 69 °C. 1H NMR (400 MHz, CDCl3): δ =
7.97–7.79 (m, 2 H), 7.52 (tt, J = 7.4, 1.3 Hz, 1 H), 7.43–7.34 (m, 3
H), 7.33–7.27 (m, 2 H), 7.13–7.06 (m, 2 H) ppm. 19F NMR
(376 MHz, CDCl3): δ = –62.74 (s, 3 F) ppm. 13C NMR (101 MHz,
CDCl3): δ = 192.32, 135.45 (q, J = 6.0 Hz), 135.14, 134.57, 131.98,
130.89, 130.83, 129.56, 129.44 (q, J = 30.1 Hz), 128.91, 124.67,
30.1 Hz), 128.66, 122.28 (q, J = 274.3 Hz) ppm. IR (KBr): ν =
˜
3063, 1665, 1450, 1292, 1157, 1121, 935, 687 cm–1. HRMS (EI):
calcd. for C16H11F3O 276.0762; found 276.0760.
122.11 (q, J = 274.4 Hz) ppm. IR (KBr): ν = 3064, 2926, 1666,
˜
(E)-1-Phenyl-3-(p-tolyl)-2-(trifluoromethyl)prop-2-en-1-one
(2b):
1489, 1309, 1285, 1160, 1127, 1074, 1011, 917, 818, 687 cm–1
HRMS (EI): calcd. for C16H10BrF3O 353.9867; found 353.9866.
.
1
Yellow oil. H NMR (400 MHz, CDCl3): δ = 8.01–7.82 (m, 2 H),
7.50 (tt, J = 7.5, 1.4 Hz, 1 H), 7.44 (s, 1 H), 7.39–7.32 (m, 2 H),
7.16–7.10 (m, 2 H), 7.01–6.95 (m, 2 H), 2.22 (s, 3 H) ppm. 19F
NMR (376 MHz, CDCl3): δ = –62.44 (s, 3 F) ppm. 13C NMR
(101 MHz, CDCl3): δ = 192.93, 140.62, 136.83 (q, J = 6.0 Hz),
135.47, 134.21, 129.65, 129.60, 129.42, 129.09, 128.76, 127.51 (q, J
(E)-3-(3,5-Dibromophenyl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-
one (2h): Yellow oil. 1H NMR (400 MHz, CDCl3): δ = 7.87–7.81
(m, 2 H), 7.53 (tt, J = 7.4, 1.2 Hz, 1 H), 7.47 (s, 1 H), 7.43–7.33
(m, 3 H), 7.31–7.27 (m, 2 H) ppm. 19F NMR (376 MHz, CDCl3):
δ = –63.06 (s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 191.51,
135.30, 135.23, 135.18, 134.68, 133.76 (q, J = 6.0 Hz), 131.74 (q, J
= 30.4 Hz), 130.78, 129.37, 128.95, 123.12, 121.72 (q, J =
= 29.8 Hz), 122.43 (q, J = 274.2 Hz), 21.25 ppm. IR (KBr): ν =
˜
3050, 1662, 1450, 1293, 1190, 1148, 1057, 953, 924, 849, 723, 699,
649 cm–1. HRMS (EI): calcd. for C17H13F3O 290.0918; found
290.0923.
274.9 Hz) ppm. IR (KBr): ν = 3067, 1666, 1548, 1277, 1163, 1128,
˜
926, 751, 739, 665 cm–1. HRMS (EI): calcd. for C16H9Br2F3O
431.8972; found 431.8973.
(E)-3-([1,1Ј-Biphenyl]-4-yl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-
one (2c): Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 8.00–7.95
(m, 2 H), 7.57–7.47 (m, 4 H), 7.47–7.37 (m, 6 H), 7.37–7.30 (m, 3
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –62.40 (s, 3 F) ppm.
13C NMR (101 MHz, CDCl3): δ = 192.79, 142.79, 139.60, 136.44
(q, J = 5.9 Hz), 135.46, 134.37, 130.80, 130.17, 129.65, 128.86,
128.85, 128.44 (q, J = 29.9 Hz), 127.96, 127.25, 126.93, 122.39 (q,
(E)-Methyl 4-(2-benzoyl-3,3,3-trifluoroprop-1-en-1-yl)benzoate (2i):
White solid, m.p. 81 °C. 1H NMR (400 MHz, CDCl3): δ = 7.89–
7.79 (m, 4 H), 7.54–7.46 (m, 2 H), 7.38–7.27 (m, 4 H), 3.82 (s, 3
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –62.95 (d, J = 1.5 Hz, 3
F) ppm. 13C NMR (101 MHz, CDCl3): δ = 192.04, 166.02, 136.19,
135.57 (q, J = 5.9 Hz), 135.11, 134.55, 131.23, 130.75 (q, J =
30.3 Hz), 129.79, 129.52, 129.32, 128.86, 121.96 (q, J = 274.6 Hz),
J = 274.3 Hz) ppm. IR (KBr): ν = 3060, 3033, 1665, 1291, 1121,
˜
798, 724, 697 cm–1. HRMS (EI): calcd. for C22H15F3O 352.1075;
found 352.1077.
52.22 ppm. IR (KBr): ν = 2960, 1723, 1666, 1266, 1110, 812, 798,
˜
(E)-3-(2-Chlorophenyl)-1-phenyl-2-(trifluoromethyl)prop-2-en-1-one
688, 671 cm–1. HRMS (EI): calcd. for C18H13F3O3 334.0817; found
334.0820.
1
(2d): Yellow oil. H NMR (400 MHz, CDCl3): δ = 7.83–7.73 (m, 3
7952
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 7948–7954

Stereoselective Synthesis of α-Trifluoromethyl Enones
Purser, P. Moore, S. Swallow, V. Gouverneur, Chem. Soc. Rev.
2008, 37, 320–330.
(E)-1-([1,1Ј-Biphenyl]-4-yl)-3-phenyl-2-(trifluoromethyl)prop-2-en-1-
one (2j): Colorless oil. 1H NMR (400 MHz, CDCl3): δ = 8.06–7.91
(m, 2 H), 7.63–7.52 (m, 5 H), 7.49–7.36 (m, 3 H), 7.35–7.28 (m, 2
H), 7.25–7.18 (m, 3 H) ppm. 19F NMR (376 MHz, CDCl3): δ =
–62.50 (d, J = 2.3 Hz, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ
= 192.16, 146.85, 139.41, 136.70 (q, J = 5.9 Hz), 134.07, 131.96,
130.19, 130.13, 129.54, 128.90, 128.73 (q, J = 30.3 Hz), 128.71,
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128.43, 127.36, 127.21, 122.28 (q, J = 275.1 Hz) ppm. IR (KBr): ν
˜
= 3060, 3032, 1663, 1599, 1292, 1156, 1121, 765, 690 cm–1. HRMS
(EI): calcd. for C22H15F3O 352.1075; found 352.1078.
(E)-1-(4-Methoxyphenyl)-3-phenyl-2-(trifluoromethyl)prop-2-en-1-
1
one (2k): White solid, m.p. 70 °C. H NMR (400 MHz, CDCl3): δ
= 7.93–7.76 (m, 2 H), 7.42 (q, J = 1.1 Hz, 1 H), 7.31–7.15 (m, 5
H), 6.87–6.76 (m, 2 H), 3.78 (s, 3 H) ppm. 19F NMR (376 MHz,
CDCl3): δ = –62.74 (d, J = 1.1 Hz, 3 F) ppm. 13C NMR (101 MHz,
CDCl3): δ = 190.93, 164.55, 136.05 (q, J = 6.0 Hz), 132.11, 132.06,
130.02, 129.53, 128.85 (q, J = 29.9 Hz), 128.67, 128.51, 122.39 (q,
[3]
[4]
J = 274.2 Hz), 114.10, 55.43 ppm. IR (KBr): ν = 2843, 1656, 1594,
˜
1266, 1244, 1156, 1120, 847, 691 cm–1. HRMS (EI): calcd. for
C17H13F3O2 306.0868; found 306.0865.
(E)-3-Phenyl-1-(m-tolyl)-2-(trifluoromethyl)prop-2-en-1-one (2l):
1
Yellow oil. H NMR (400 MHz, CDCl3): δ = 7.74 (s, 1 H), 7.70–
7.65 (m, 1 H), 7.48 (q, J = 1.2 Hz, 1 H), 7.35–7.29 (m, 1 H), 7.28–
7.15 (m, 6 H), 2.32 (s, 3 H) ppm. 19F NMR (376 MHz, CDCl3): δ
= –62.56 (s, 3 F) ppm. 13C NMR (101 MHz, CDCl3): δ = 192.84,
138.67, 136.74 (q, J = 5.9 Hz), 135.34, 135.20, 132.01, 130.10,
129.84, 129.53, 128.78 (q, J = 30.3 Hz), 128.67, 128.64, 127.14,
122.31 (q, J = 274.3 Hz), 21.19 ppm. IR (KBr): ν = 3010, 1667,
˜
1291, 1156, 1122, 942, 755, 690, 660 cm–1. HRMS (EI): calcd. for
C17H13F3O 290.0918; found 290.0921.
[5]
(E)-1-(4-n-Pentylphenyl)-3-phenyl-2-(trifluoromethyl)prop-2-en-1-
1
one (2m): Yellow oil. H NMR (400 MHz, CDCl3): δ = 7.89–7.75
(m, 2 H), 7.46 (s, 1 H), 7.34–7.08 (m, 7 H), 2.58 (t, J = 7.6 Hz, 2
H), 1.68–1.48 (m, 2 H), 1.40–1.19 (m, 4 H), 0.86 (t, J = 6.5 Hz, 3
H) ppm. 19F NMR (376 MHz, CDCl3): δ = –62.62 (s, 3 F) ppm.
13C NMR (101 MHz, CDCl3): δ = 192.20, 150.35, 136.46 (q, J =
5.9 Hz), 133.19, 132.05, 129.99, 129.78, 129.55, 128.92 (q, J =
29.7 Hz), 128.84, 128.63, 122.35 (q, J = 274.3 Hz), 35.99, 31.35,
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30.48, 22.41, 13.92 ppm. IR (KBr): ν = 2957, 2931, 2859, 1664,
˜
1603, 1271, 1158, 1123, 756, 691 cm–1. HRMS (EI): calcd. for
C21H21F3O 346.1545; found 346.1549.
Supporting Information (see footnote on the first page of this arti-
1
cle): Copies of H and 13C NMR spectra of all products and the
crystal data and structural refinement details of 2i.
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The authors thank the National Natural Science Foundation (grant
numbers 21032006, 21172240, 21472222), National Basic Research
Program of China (grant number 2015CB931900), the 973, Pro-
gram of China (grant number 2012CBA01200), Science and Tech-
nology Commission of Shanghai Municipality (grant number
14ZR1448800), the Chinese Academy of Sciences, and the
Syngenta PhD Studentship Award for financial support. The au-
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national Research Centre for proofreading of the manuscript.
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7953

Y.-L. Ji, J.-H. Lin, J.-C. Xiao, Y.-C. Gu
FULL PAPER
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Received: September 15, 2014
Published Online: October 29, 2014
7954
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Eur. J. Org. Chem. 2014, 7948–7954