Regioselective Formation of Enol Esters from the Ruthenium-Catalyzed Markovnikov Addition of Carboxylic Acids to Alkynes

Article abstract of DOI:10.1021/acs.joc.5b02293

The ruthenium complexes [Ru(CO)₂(P(p-C₆H₄-X)₃)₂(O₂CPh)₂] (1a, X = CF₃; 1b, X = Cl; 1c, X = H; 1d, X = Me; 1e, X = OMe) were successfully applied in the regioselective Markovnikov addition of carboxylic acids to terminal alkynes, yielding valuable enol esters. Catalyst screening revealed a significant influence of phosphine's electronic nature on activity and selectivity. The highest activity was achieved with catalyst 1a, featuring the most electron-withdrawing phosphine ligand. Selectivity and activity could be further improved by the addition of catalytic amounts of AgOTf. Moreover, excellent selectivities with up to 99% of the Markovnikov product were achieved. The electronic influence of the substrates on the reaction rate was quantified by Hammett plots. By the use of electron-rich alkynes or highly acidic carboxylic acids, the reaction rate could be increased. Hence, the addition of highly acidic pentafluorobenzoic acid to electron-rich 4-methoxyphenylacetylene can even be carried out quantitatively at 25°C within 4 h. Furthermore, a broad range of simple as well as electronically or sterically challenging substrates could be isolated in good to excellent yields with high regioselectivity and under mild reaction conditions (25-70°C). The best reported activities and selectivities were obtained for the conversion of aromatic alkynes.

Full text of DOI:10.1021/acs.joc.5b02293

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Article
Regioselective Formation of Enol Esters from the Ruthenium-
catalyzed Markovnikov Addition of Carboxylic Acids to Alkynes
Janine Jeschke, Christian Gäbler, and Heinrich Lang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.5b02293 • Publication Date (Web): 18 Dec 2015
Downloaded from http://pubs.acs.org on December 26, 2015
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Regioselective Formation of Enol Esters from the Ruthenium-catalyzed
Markovnikov Addition of Carboxylic Acids to Alkynes
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Janine Jeschke, Christian Gäbler and Heinrich Lang*
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Technische Universität Chemnitz, Faculty of Natural Sciences, Institute of Chemistry, Inorganic
Chemistry, 09107 Chemnitz, Germany
heinrich.lang@chemie.tuꢀchemnitz.de
ABSTRACT
The ruthenium complexes [Ru(CO)2(P(pꢀC6H4ꢀX)3)2(O2CPh)2] (1a, X = CF3; 1b, X = Cl; 1c, X = H; 1d, X = Me;
1e, X = OMe) were successfully applied in the regioselective Markovnikov addition of carboxylic acids to
terminal alkynes, yielding valuable enol esters. The catalyst screening revealed a significant influence of the
phosphine´s electronic nature on the activity and selectivity. The highest activity was achieved with catalyst 1a,
featuring the most electron withdrawing phosphine ligand. Selectivity and activity could be further improved by
the addition of catalytic amounts of AgOTf. Moreover, excellent selectivities with up to 99 % of the
Markovnikov product were achieved. The electronic influence of the substrates on the reaction rate was
quantified by Hammett plots. By the use of electron rich alkynes or highly acidic carboxylic acids the reaction
rate could be increased. Hence, the addition of highly acidic pentafluorobenzoic acid to electron rich 4ꢀ
methoxyphenylacetylene can even be carried out quantitatively at 25 °C within 4 h. Furthermore, a broad range
of simple as well as electronically or sterically challenging substrates could be isolated in good to excellent
yields with high regioselectivity and under mild reaction conditions (25–70 °C). The best reported activities and
selectivities were obtained for the conversion of aromatic alkynes.
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INTRODUCTION
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Enol esters are valuable intermediates in a variety of organic synthetic methodologies. They are widely used as
mild acylation reagents,1 as substrates in asymmetric hydrogenation,2 cycloaddition,3 aldolꢀ4 and Mannichꢀtype5
reactions and in vinyl arene synthesis by decarbonylative HeckꢀMizoroki olefination.6 Moreover, vinyl esters
such as vinyl acetate are also of considerable industrial interest as they are utilized as monomers in various
polymerization reactions.7 Classical methods for the preparation of enol esters include the acylation of enolates8
and the acetoxymercuration of alkynes.9 However, these reactions require the use of toxic mercury salts or
stoichiometric amounts of a strong acid or base. Therefore, the most straightforward and atom economic route to
enol esters is the transition metal catalyzed addition of carboxylic acids to alkynes.10
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Since the first reports on the rutheniumꢀcatalyzed enol ester synthesis in the 1980ies,11 a variety of transition
metal complexes has been investigated, including rhodium,12 rhenium,13 iridium,14 palladium,15 gold16 and
bimetallic17 catalysts. But due to their high efficiency, excellent tolerance of functional groups and ease of
preparation, ruthenium catalysts are still the most intensively studied and applied systems.18 Some ruthenium
catalysts also allow a good control of the regioꢀ and stereoselectivity, leading to the favored formation of one of
the three possible isomers (Scheme 1). Thereby, the regioselectivity of the reaction is affected by the
coordination mode of the alkyne to the metal center.19,20 The η2ꢀalkyne binding mode leads to a nucleophilic
attack at the C1 position of the alkyne and hence the Markovnikov product is obtained.21 On the contrary, a
tautomerization to the vinylidene analogue affords the antiꢀMarkovnikov products by nucleophilic attack at the
αꢀcarbon.22
Scheme 1. Proposed mechanism for the regioselective Ruꢀcatalyzed formation of enol esters23
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Much effort has been invested to adjust the selectivity in enol ester synthesis. Successful approaches include the
control of the selectivity by the solvent,24 the ligands25 or the addition of catalytic amounts of a Lewis acid or
base.26,27 However, there are only few examples of catalysts that selectively promote the formation of
Markovnikov products.23–28 Most known catalytic systems lead to the formation of the antiꢀMarkovnikov
species.29 Another challenge is that the Markovnikov selective catalysts often require quite harsh reaction
conditions or suffer from poor selectivities in the conversion of aromatic alkynes.23–28
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Recently, we reported on the synthesis of βꢀoxo esters by the Markovnikov addition of carboxylic acids to
propargylic alcohols catalyzed by mononuclear ruthenium complexes of type [Ru(CO)2(PR1 ) (O2CR2)2] (R1, R2
3 2
= aryl, alkyl).30,31 In continuation of our studies we herein describe the successful application of ruthenium
complexes [Ru(CO)2(P(pꢀC6H4ꢀX)3)2(O2CPh)2] (1a, X = CF3; 1b, X = Cl; 1c, X = H; 1d, X = Me; 1e, X = OMe)
in the regioselective Markovnikov addition of carboxylic acids to terminal alkynes, yielding valuable enol esters.
The electronic impact of the phosphine ligands as well as the effect of catalytic amounts of an additive on the
reaction´s activity and selectivity is discussed. Furthermore, the electronic influence of the substrates on the
reaction rate is investigated.
RESULTS AND DISCUSSION
For the evaluation of the catalytic performance of organometallic ruthenium complexes [Ru(CO)2(P(pꢀC6H4ꢀ
X)3)2(O2CPh)2] 31 (1a, X = CF3; 1b, X = Cl; 1c, X = H; 1d, X = Me; 1e, X = OMe) in the enol ester synthesis, the
common addition of benzoic acid to phenylacetylene was chosen as model reaction. In the initial experiments,
benzoic acid (1.0 mmol) and phenylacetylene (2.0 mmol) were dissolved in toluene (1 mL) and treated with 1.0
mol% of catalyst 1 for 24 h at 60 °C (Table 1).32 The efficiency and selectivity of the optimization reactions was
determined by 1H NMR spectroscopy applying acenaphthene as internal standard.
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Table 1. Catalyst screening in the addition of benzoic acid to phenylacetylene to give 2aa and 3aaa
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Selectivity [%]c
Entry
Catalyst
Yield [%]b
(Z)ꢀ3aa
(E)ꢀ3aa
2aa
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81
91
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97
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100
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73
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7
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2
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3
1
1a
1b
1c
1d
1e
a
Reaction conditions: benzoic acid (1.0 mmol), phenylacetylene (2.0 mmol), acenaphthene (0.5 mmol), 1 (1.0
mol%), toluene (1 mL), 60 °C, 24 h. Total yield determined by 1H NMR spectroscopy applying acenaphthene
b
as internal standard. c Relative ratio of isomers determined by 1H NMR spectroscopy.
From Table 1 it can be seen that all tested catalysts 1a–e lead to a favored formation of the Markovnikov product
2aa. Furthermore, a correlation between the basicity of the phosphine ligands and the activity and selectivity of
the resulting catalysts 1a–e could be established. The highest activity is achieved with catalyst 1a, which features
with P(pꢀC6H4ꢀCF3)3 the most electron withdrawing phosphine ligand. On the contrary, an enhanced selectivity
for the Markovnikov product 2aa is obtained with increasing basicity of the phosphine ligands.
For further optimization reactions the most active catalyst 1a was chosen. The solvent screening revealed that in
nonꢀpolar solvents like carbon tetrachloride, toluene or a toluene/cyclohexane mixture (1:1, v:v) the highest
activities were observed. Although the toluene/cyclohexane mixture gave the best Markovnikov selectivity of
79 %, we continued with the usage of toluene due to its highest observed activity (Table S1, Supporting
Information).
In order to further improve the selectivity for the Markovnikov product, the effect of catalytic amounts of
various additives in the addition of benzoic acid to phenylacetylene was tested. Gooßen et al. could control the
regioselectivity by the addition of various bases.27 Whereas, the Markovnikov addition was observed in the
presence of inorganic bases like Na2CO3, the reverse regioselectivity was obtained by the addition of organic
bases like 4ꢀN,Nꢀdimethylaminopyridine (DMAP).27 The effect of additives in the enol ester synthesis was also
studied by Tripathy and Bhattacharjee.26 Interestingly, their catalytic system leads to the opposite regioselectivity
for the addition of Na2CO3 compared to the results of Gooßen. However, they could also achieve a high
selectivity for the Markovnikov products in the presence of the Lewis acid BF3ꢁEt2O. Inspired by these results,
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we explored the impact of 1 mol% of various additives on the selectivity of our catalytic system in the addition
of benzoic acid to phenylacetylene (Table 2).
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Table 2. Influence of additives on the catalytic performance of 1a in the addition of benzoic acid to
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phenylacetylenea
Selectivity [%]c
Entry
Additive
Yield [%]b
(Z)ꢀ3aa
(E)ꢀ3aa
2aa
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62
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96
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0
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–
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0
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2
Na2CO3
Cs2CO3
NEt3
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DMAP
AgNO3
AgI
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85
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100
0
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BF3ꢁEt2O
Li(B[C6F5]4)·2Et2O
TfOH
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13d
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KOTf
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AgOTf
AgOTf
Mg(OTf)2
Yb(OTf)3
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100
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0
a
Reaction conditions: benzoic acid (1.0 mmol), phenylacetylene (2.0 mmol), acenaphthene (0.5 mmol), 1a (1.0
b
1
mol%), additive (1.0 mol%), toluene (1 mL), 70 °C, 2 h. Total yield determined by H NMR spectroscopy
c
1
applying acenaphthene as internal standard. Relative ratio of isomers determined by H NMR spectroscopy.
d Reaction performed without catalyst.
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From Table 2 it can be seen that compared to the waiving of any additive (Entry 1, Table 2), the addition of the
inorganic bases Na2CO3 and Cs2CO3 did not show an any effect on the activity nor selectivity (Entries 2 and 3,
Table 2). The addition of organic bases led to a decline of the activity, probably due to the coordination to the
ruthenium ion/center (Entries 4 and 5, Table 2). However, an obvious increase of the selectivity for the
Markovnikov product was obtained by adding Lewis acids like BF3ꢁEt2O (Entries 8 and 9, Table 2). An
additional accelerating effect was observed for TfOH (Entry 10, Table 2). Based on the excellent results for
TfOH, several triflates were tested, among which AgOTf resulted in a further improvement of the activity.33
Additionally, it was examined whether AgOTf exhibits a catalytic activity by itself, but no conversion was
detected without usage of a ruthenium catalyst (Entry 13, Table 2). The effect of the amount of the various
triflates on the productivity was also explored (Table S2, Supporting Information), but the best results in terms of
activity and selectivity were still reached with 1 mol% of AgOTf.
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Besides the productivity, the effect of AgOTf on the catalytic activity was examined. Therefore, the reaction of
benzoic acid with phenylacetylene was followed over time with and without the addition of AgOTf (Figure 1).
The reaction profile without additive shows an induction period at the beginning of the conversion and a
complete conversion after 7 h at 70 °C. However, no induction period is observed for the addition of AgOTf.33
Instead, a considerably higher reaction rate and full conversion already after 2 h is reached.
Figure 1. Effect of AgOTf on the reaction profile in the addition of benzoic acid to phenylacetylene catalyzed by
1a at 70 °C in toluene. Please, notice that upon addition of AgOTF solely 2aa is formed, while without additive
a mixture of the three isomers 2aa:(Z)ꢀ3aa:(E)ꢀ3aa in the ratio of 70:24:6 is produced (the graph contains the
sum of all three isomers).
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To check the influence of AgOTf on the activity of the other catalysts featuring more basic phosphine ligands,
additional reaction profiles for the conversion of benzoic acid with phenylacetylene catalyzed by 1c and 1e were
recorded (Figure S3, Supporting Information). The basicity of the phosphine ligand clearly affects the activity of
the resulting catalyst, whereby with increasing basicity a distinct drop of the catalytic activity is observed.
Independently of the phosphine ligands, a high selectivity for the Markovnikov product was obtained for all
catalysts by the addition of AgOTf. Complex 1a in combination with AgOTf still showed the best catalytic
performance in enol ester synthesis. It is also interesting to note that for all examined catalysts no induction
period at the beginning of the conversion was detected. For this reason it is very likely that AgOTf promotes the
formation of the catalytically active species.
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Finally, temperature dependent reaction profiles for the conversion of benzoic acid with phenylacetylene to
afford 2aa catalyzed by 1a/AgOTf were studied (Figure 2). As it was already presented in Figure 1, complete
conversion was achieved after 2 h at 70 °C. By lowering the reaction temperature to 60 °C, nearly the fourfold
reaction time is needed to reach almost full conversion. A further decrease of temperature is not appropriate as
quite low productivities were obtained at 50 °C. Apparently, the activity of the catalytic system is reduced for
longer reaction times.
Figure 2. Temperature dependent reaction profiles for the addition of benzoic acid to phenylacetylene yielding
2aa catalyzed by 1a in combination with 1 mol% of AgOTf.
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After optimization of the reaction conditions, the electronic impact of the substrates in the enol ester synthesis
was explored. Therefore, a correlation of the Hammett value σρ and the reaction rates in the conversion of a
series of paraꢀsubstituted phenylacetylenes and benzoic acids was investigated (Figure 3). The negative ρ value
(ρ = –0.294) for the addition of benzoic acid to paraꢀsubstituted phenylacetylenes pꢀYꢀC6H4ꢀC≡CH (Y = OMe,
Me, H, Cl, CF3) reveals electron rich alkynes to increase the reaction rate. This observation can be explained by
a facilitated coordination of an electron rich C,C triple bond to the electrophilic ruthenium atom. On the
contrary, for the reaction of paraꢀsubstituted benzoic acids pꢀZꢀC6H4ꢀCO2H (Z = OMe, Me, H, Cl, CF3) with
phenylacetylene a positive ρ value (ρ = +0.061) was observed. A possible interpretation of these Hammett data
might be that the carboxylic acid is involved in the alkyne activation. Thus, the coordination of more electronꢀ
deficient carboxylic acids to ruthenium, e.g. by carboxylate exchange,30 probably accelerates the alkyne
activation by increasing the electrophilicity of ruthenium. From the ρ values it can also be concluded that the
electronic effect of the substituents at the alkyne are more decisive on the product formation than that of the
carboxylic acids. Therefore, the activation of the alkyne is considered to be the rateꢀdetermining step in the enol
ester synthesis.
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Figure 3. Hammett plots for the conversion of paraꢀsubstituted phenylacetylenes pꢀYꢀC6H4ꢀC≡CH (Y = OMe,
Me, H, Cl, CF3) with benzoic acid (left; y = –0.294x – 0.008, R2 = 0.979) and the conversion of paraꢀsubstituted
benzoic acids pꢀZꢀC6H4ꢀCO2H (Z = OMe, Me, H, Cl, CF3) with phenylacetylene (right; y = 0.061x – 0.005, R2 =
0.964) in toluene.
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To assess the substrate scope as well as the tolerance of the reaction towards functional or sterically demanding
groups a substrate screening was carried out under optimized reaction conditions at 70 °C applying 1.0 mol% of
1a and AgOTf, respectively. Scheme 2 reveals that diverse aliphatic and aromatic alkynes and carboxylic acids
can be converted to enol esters in good to excellent isolated yields.
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Scheme 2. Substrate Scope in the Enol Ester Synthesis
Reaction conditions: carboxylic acid (1.0 mmol), acetylene (2.0 mmol), 1a (1.0 mol%), AgOTf (1.0 mol%),
toluene (1 mL), 70 °C, isolated yield, optimized reaction times are given in parentheses. a Reaction performed at
60 °C. b Reaction performed at 25 °C.
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The substrate screening of the electronically modified aromatic alkynes 2aa–ah confirms the findings from the
Hammett plot. Whereas substrates with electron donating substituents can even be successfully converted at a
decreased reaction temperature of 60 °C in 2 h (2ab), electron deficient alkynes need significantly longer
reaction times (2ag,ah). Next to paraꢀsubstituted phenylacetylenes, also substituents in orthoꢀposition are well
tolerated (2ac). The conversion of aliphatic alkynes (2ai–ao) was usually completed within 3 h, whereby
branched as well as linear alkynes of various chain lengths could be reacted without drop of the yields.
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The generality of the carboxylic acid allows the successful conversion of various aliphatic (2ab–ag), aromatic
(2ah–ao) and even heterocyclic compounds (2ah,ai). As estimated from the Hammett plot, strong acidic acids
are converted preferably (2al, 2af). When a highly acidic acid like pentafluorobenzoic acid is converted with an
electron rich alkyne like 4ꢀmethoxyphenylacetylene, the reaction can even be carried out quantitatively at 25 °C
within 4 h (2bl). Moreover, the reaction also proceeds smoothly in the presence of sterically demanding
substrates (2an,ao) and various functionalities like ester (2ak), ether (2ba), halide (2ab) and even hydroxy
groups (2aj) are tolerated. It is also important to note that for all reactions applying a carboxylic acid apart from
benzoic acid, the formation of up to 2 % of the benzoate product 2aa is observed. The reason for this is that the
benzoate ligands bound to the initial catalyst complex 1a can also be converted during the reaction. Thereby, the
formation of the minor product 2aa could either arise from an intramolecular attack of the already bounded
benzoate group to the activated alkyne or from an exchange of the carboxylates followed by an intermolecular
nucleophilic attack.30
In comparison to already known catalytic systems,14b,16,18d,23–28 catalyst 1a exhibits productivities, for both simple
and electronically or sterically challenging substrates that often match or even exceed those reported in literature.
Up to now, the conversion of aromatic alkynes often suffered from poor selectivities, high temperatures or long
reaction times.23–28 With our catalytic system the addition of benzoic acid to phenylacetylene proceeds smoothly
within 2 h at 70 °C, yielding 99 % of isolated Markovnikov product 2aa. Compared to established catalysts, we
obtained the best reported catalytic results for this reaction (Table 3).
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Table 3. Comparison of the isolated yields of 2aa in the addition of benzoic acid to phenylacetylene for
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literature known catalytic systems
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Entry
Catalyst
T [° C] c[cat] [mol%]a
70 1.0
90–95 2.0
t [h]
2
Yield [%]b
Reference
this work
[24]
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2
3
4
5
6
99
98
87
75
60
53
1a
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RuHCl(CO)(PCy3)2
Ru(CO)3(PCy3)2
8–12
5
75
80
60
70
1.0
1.0
2.0
0.8
[25]
[Ru(PPh3)2(CH3CN)3Cl][BPh4]
transꢀ[RuCl2(η3:η3ꢀC10H16)(PPh3)]
[RuCl2(pꢀcymene)]2/PFur3
17
[26]
24
[23]
16
[27]
a Based on [Ru]. b Isolated yield of isomer 2aa.
CONCLUSION
Ruthenium complexes [Ru(CO)2(P(pꢀC6H4ꢀX)3)2(O2CPh)2] (1a, X = CF3; 1b, X = Cl; 1c, X = H; 1d, X = Me; 1e,
X = OMe) were found to be highly efficient catalysts in the atomꢀeconomic addition of carboxylic acids to
terminal alkynes, yielding synthetically valuable enol esters. For all tested catalysts the formation of the
Markovnikov products was favored. The activity and selectivity of the catalysts could be successfully tuned by
the basicity of the phosphine ligands. The highest activity was achieved with catalyst 1a, featuring the most
electron deficient phosphine ligand. However, an enhanced selectivity for the Markovnikov product was
observed with increasing basicity of the phosphine ligands. The selectivity as well as the activity could be further
improved by the addition of catalytic amounts of AgOTf. The best catalytic performance was achieved with
catalyst 1a in combination with 1 eq. AgOTf.
The electronic influence of the substrates on the reaction rate was quantified by Hammett studies for the
conversion of paraꢀsubstituted phenylacetylenes and benzoic acids. The results indicate an increased reaction
rate for the conversion of electron rich phenylacetylenes or benzoic acids with electron withdrawing substituents.
By converting an electron rich alkyne and a highly acidic carboxylic acid, the reaction can even be carried out
quantitatively within 4 h at 25 °C. Additionally, a broad range of facile as well as challenging substrates could be
successfully converted under mild conditions, including aliphatic and aromatic alkynes and carboxylic acids. All
reactions proceeded smoothly in short reaction times with high regioselectivity for the Markovnikov products.
Furthermore, various common functional groups like esters, ethers, halides, and even sensitive hydroxy groups
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were tolerated. For the conversion of aromatic alkynes the best catalytic performance reported in literature was
obtained.23–27 Further investigations on the conversion of internal alkynes are underway.
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EXPERIMENTAL SECTION
General Information. All reactions were carried out under an atmosphere of argon using standard Schlenk
techniques. Compounds 1a–e were prepared according to previously published procedures.31 Toluene was dried
by a solvent purification system. Acenaphthene was purified by sublimation at 75 °C (1.0 mbar). All other
chemicals were purchased from commercial suppliers and used without further purification. For column
chromatography silica with a particle size of 40–60 ꢂm (230–400 mesh ASTM) was used. NMR spectra were
recorded with a spectrometer operating at 500.3 MHz for H and 125.7 MHz for 13C{1H} spectra in the Fourier
1
transform mode at 298 K. Chemical shifts are reported in δ (ppm) downfield from tetramethylsilane with the
solvent as reference signal (1H NMR, CHCl3 δ 7.26; 13C{1H} NMR, CDCl3 δ 77.16). High resolution mass
spectra were recorded with a timeꢀofꢀflight (TOF) spectrometer using electroꢀspray ionization (ESI).
General Procedure for the Catalytic Reaction. In a screwꢀcapped vial and under an atmosphere of argon the
carboxylic acid (1.0 mmol), the alkyne (2.0 mmol), the ruthenium catalyst 1 (0.01 mmol), the additive (0.01
mmol), and acenaphthene (77 mg, 0.5 mmol) as internal standard were dissolved in toluene (1 mL). The sealed
vial was immersed in a heating mantle preheated to 70 °C and stirred for 1ꢀ24 h. The progress of the reaction
1
was monitored by regular sampling and analysis by H NMR spectroscopy applying acenaphthene as internal
standard. Analytically pure products were isolated by column chromatography on silica gel. All catalytic results
have been verified by at least two independent experiments.
Hammett Study: Alkyne. In a screwꢀcapped vial and under an atmosphere of argon the respective paraꢀ
substituted phenylacetylene pꢀYꢀC6H4ꢀC≡CH (Y = OMe, Me, H, Cl, CF3) (2.0 mmol), benzoic acid (122 mg, 1.0
mmol), 1a (13.32 mg, 0.01 mmol), AgOTf (2.56 mg, 0.01 mmol), and acenaphthene (77 mg, 0.5 mmol) as
internal standard were dissolved in toluene (1 mL). The sealed vial was immersed in a heating mantle preheated
to 60 °C. The reaction was monitored by 1H NMR spectroscopy applying acenaphthene as internal standard in 15
min intervals. The kX was estimated from a firstꢀorder plot of ln[product] vs reaction time rather than ln[benzoic
acid] vs reaction time because the 1H NMR integration of the product signals (=CH2) was more accurate.
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Hammett Study: Carboxylic Acid. In a screwꢀcapped vial and under an atmosphere of argon the respective
paraꢀsubstituted benzoic acid pꢀZꢀC6H4ꢀCO2H (Z = OMe, Me, H, Cl, CF3) (1.0 mmol), phenylacetylene (204
mg, 2.0 mmol), 1a (13.32 mg, 0.01 mmol), AgOTf (2.56 mg, 0.01 mmol), and acenaphthene (77 mg, 0.5 mmol)
as internal standard were dissolved in toluene (20 mL). The sealed vial was immersed in a heating mantle
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preheated to 80 °C. The reaction was monitored by H NMR spectroscopy applying acenaphthene as internal
standard in 30 min intervals. The kX was estimated from a firstꢀorder plot of ln[product] vs reaction time rather
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than ln[carboxylic acid] vs reaction time because the H NMR integration of the product signals (=CH2) was
more accurate.
Characterization Data of Catalysis Products
1-Phenylvinyl benzoate (2aa)14,16,18b,18c,23–27,29b,29c,29e
Benzoic acid (122 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as eluent,
1
yielding the title compound as yellow liquid (221 mg, 99 %). H NMR (CDCl3, 500.3 MHz): δ 5.21 (d, J = 2.2
Hz, 1H), 5.63 (d, J = 2.3 Hz, 1H), 7.33–7.41 (m, 3H), 7.51–7.56 (m, 2H), 7.56–7.60 (m, 2H), 7.62–7.68 (m, 1H),
8.21–8.27 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 102.4, 125.0, 128.68, 128.74, 129.1, 129.6, 130.3, 133.7,
134.4, 153.3, 164.9.
1-(4-Methoxyphenyl)vinyl benzoate (2ba)18b,18c,23,24,26
Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀmethoxyphenylacetylene (264 mg, 2.0 mmol) for 2 h at
60 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
1
eluent, yielding the title compound as yellow liquid (231 mg, 91 %). H NMR (CDCl3, 500.3 MHz): δ 3.80 (s,
3H), 5.07 (d, J = 2.2 Hz, 1H), 5.48 (d, J = 2.2 Hz, 1H), 6.85–6.90 (m, 2H), 7.46–7.55 (m, 4H), 7.61–7.67 (m,
1H), 8.18–8.24 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 55.4, 100.5, 114.1, 126.5, 127.1, 128.7, 129.7, 130.2,
133.6, 153.1, 160.3, 164.9.
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1-(2-Methoxyphenyl)vinyl benzoate (2ca)
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7
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Benzoic acid (122 mg, 1.0 mmol) was converted with 2ꢀmethoxyphenylacetylene (264 mg, 2.0 mmol) for 2 h at
70 °C. The product was purified by silicaꢀgel column chromatography using cyclohexane/ethyl acetate (95:5,
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9
v/v) as eluent, yielding the title compound as yellow liquid (185 mg, 73 %). H NMR (CDCl3, 500.3 MHz): δ
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3.84 (s, 3H), 5.32 (d, J = 1.3 Hz, 1H), 5.73 (d, J = 1.4 Hz, 1H), 6.91–6.96 (m, 2H), 7.28–7.32 (m, 1H), 7.43–7.46
(m, 1H), 7.47–7.52 (m, 2H), 7.58–7.64 (m, 1H), 8.16–8.20 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 55.7,
106.8, 111.5, 120.6, 123.6, 128.5, 128.6, 130.0, 130.1, 130.2, 133.4, 150.6, 157.2, 164.9. HRMS (ESIꢀTOF) m/z:
[M + Na]+ Calcd for C16H14O3Na 277.0835; Found 277.0833.
1-(4-Tolyl)vinyl benzoate (2da)18b,18c,24,29b
Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀtolylacetylene (232 mg, 2.0 mmol) for 2 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as eluent,
yielding the title compound as pale yellow liquid (230 mg, 97 %). 1H NMR (CDCl3, 500.3 MHz): δ 2.35 (s, 3H),
5.12 (d, J = 2.2 Hz, 1H), 5.55 (d, J = 2.2 Hz, 1H), 7.13–7.18 (m, 2H), 7.42–7.46 (m, 2H), 7.49–7.54 (m, 2H),
7.61–7.67 (m, 1H), 8.18–8.23 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 21.4, 101.5, 125.0, 128.7, 129.4, 129.7,
130.3, 131.7, 133.7, 139.1, 153.4, 165.0.
1-(4-(tert-Butyl)phenyl)vinyl benzoate (2ea)
Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀtertꢀbutylphenylacetylene (316 mg, 2.0 mmol) for 3 h at
70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
1
eluent, yielding the title compound as brown liquid (258 mg, 92 %). H NMR (CDCl3, 500.3 MHz): δ 1.34 (s,
9H), 5.16 (d, J = 2.2 Hz, 1H), 5.59 (d, J = 2.2 Hz, 1H), 7.37–7.42 (m, 2H), 7.49–7.56 (m, 4H), 7.62–7.68 (m,
1H), 8.21–8.27 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 31.3, 34.7, 101.6, 124.8, 125.6, 128.7, 129.7, 130.2,
131.6, 133.6, 152.2, 153.4, 164.9. HRMS (ESIꢀTOF) m/z: (M + Na)+ Calcd for C19H20O2Na 303.1356; Found
303.1353.
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1-(4-Fluorophenyl)vinyl benzoate (2fa)24,26
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Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀfluorophenylacetylene (240 mg, 2.0 mmol) for 2 h at 70
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9
°C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
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eluent, yielding the title compound as pale yellow liquid (227 mg, 94 %). H NMR (CDCl3, 500.3 MHz): δ 5.16
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(d, J = 2.3 Hz, 1H), 5.53 (d, J = 2.3 Hz, 1H), 7.01–7.07 (m, 2H), 7.49–7.55 (m, 4H), 7.63–7.67 (m, 1H), 8.17–
8.24 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 102.3, 115.7 (d, JCF = 21.9 Hz), 127.0 (d, JCF = 8.5 Hz), 128.8,
129.5, 130.3, 130.8 (d, JCF = 3.5 Hz), 133.8, 152.5, 163.3 (d, JCF = 249 Hz), 164.9.
1-(4-Chlorophenyl)vinyl benzoate (2ga)34
Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀchlorophenylacetylene (273 mg, 2.0 mmol) for 16 h at
70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
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eluent, yielding the title compound as pale yellow liquid (243 mg, 94 %). H NMR (CDCl3, 500.3 MHz): δ 5.21
(d, J = 2.4 Hz, 1H), 5.59 (d, J = 2.4 Hz, 1H), 7.30–7.36 (m, 2H), 7.45–7.50 (m, 2H), 7.50–7.56 (m, 2H), 7.62–
7.68 (m, 1H), 8.18–8.23 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 102.9, 126.4, 128.8, 128.9, 129.3, 130.2,
133.0, 133.8, 135.0, 152.3, 164.8.
1-(4-(Trifluoromethyl)phenyl)vinyl benzoate (2ha)24
Benzoic acid (122 mg, 1.0 mmol) was converted with 4ꢀ(trifluoromethyl)phenylacetylene (340 mg, 2.0 mmol)
for 24 h at 70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate
(9:1, v/v) as eluent, yielding the title compound as yellow liquid (231 mg, 79 %). 1H NMR (CDCl3, 500.3 MHz):
δ 5.32 (d, J = 2.5 Hz, 1H), 5.70 (d, J = 2.5 Hz, 1H), 7.51–7.57 (m, 2H), 7.59–7.69 (m, 5H), 8.19–8.24 (m, 2H).
13C NMR (CDCl3, 125.7 MHz): δ 104.7, 124.0 (q, JCF = 272 Hz), 125.4, 125.7 (q, JCF = 3.8 Hz), 128.9, 129.1,
130.3, 130.9 (q, JCF = 32.6 Hz), 134.0, 137.9, 152.1, 164.8.
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3-Methylbut-1-en-2-yl benzoate (2ia)
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Benzoic acid (122 mg, 1.0 mmol) was converted with 3ꢀmethylꢀ1ꢀbutyne (136 mg, 2.0 mmol) for 3 h at 70 °C.
The product was purified by silicaꢀgel column chromatography using nꢀhexane/diethyl ether (10:1, v/v) as
eluent, yielding the title compound as colorless liquid (156 mg, 82 %). 1H NMR (CDCl3, 500.3 MHz): δ 1.15 (d,
J = 6.8 Hz, 6H), 2.58 (hept, J = 6.8 Hz, 1H), 4.82–4.89 (m, 2H), 7.44–7.51 (m, 2H), 7.57–7.63 (m, 1H), 8.07–
8.13 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 20.4, 32.6, 99.6, 128.6, 130.06, 130.09, 133.4, 161.6, 165.0.
HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C12H14O2Na 213.0886; Found 213.0903.
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3,3-Dimethylbut-1-en-2-yl benzoate (2ja)12c,23,27,29e
Benzoic acid (122 mg, 1.0 mmol) was converted with 3,3ꢀdimethylꢀ1ꢀbutyne (164 mg, 2.0 mmol) for 3 h at 70
°C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/diethyl ether (98:2, v/v) as
eluent, yielding the title compound as colorless liquid (143 mg, 70 %). 1H NMR (CDCl3, 500.3 MHz): δ 1.19 (s,
9H), 4.81 (d, J = 2.1 Hz, 1H), 4.99 (d, J = 2.1 Hz, 1H), 7.43–7.51 (m, 2H), 7.56–7.62 (m, 1H), 8.08–8.13 (m,
2H). 13C NMR (CDCl3, 125.7 MHz): δ 28.0, 36.6, 99.3, 128.6, 130.1, 130.3, 133.4, 162.8, 164.9.
Pent-1-en-2-yl benzoate (2ka)11b,11f,23
Benzoic acid (122 mg, 1.0 mmol) was converted with 1ꢀpentyne (136 mg, 2.0 mmol) for 3 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as eluent,
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yielding the title compound as pale yellow liquid (186 mg, 98 %). H NMR (CDCl3, 500.3 MHz): δ 0.98 (t, J =
7.4 Hz, 3H), 1.52–1.62 (m, 2H), 2.30–2.35 (m, 2H), 4.82–4.85 (m, 1H), 4.86–4.88 (m, 1H), 7.44–7.49 (m, 2H),
7.56–7.61 (m, 1H), 8.07–8.11 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 13.6, 20.0, 35.6, 101.6, 128.6, 130.0,
130.1, 133.4, 156.7, 164.9.
Hex-1-en-2-yl benzoate (2la)16,23,24,26,28,29e
Benzoic acid (122 mg, 1.0 mmol) was converted with 1ꢀhexyne (164 mg, 2.0 mmol) for 3 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as eluent,
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yielding the title compound as pale yellow liquid (195 mg, 96 %). H NMR (CDCl3, 500.3 MHz): δ 0.92 (t, J =
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8
9
7.3 Hz, 3H), 1.35–1.44 (m, 2H), 1.48–1.57 (m, 2H), 2.31–2.38 (m, 2H), 4.82–4.85 (m, 1H), 4.85–4.88 (m, 1H),
7.43–7.50 (m, 2H), 7.56–7.62 (m, 1H), 8.06–8.12 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 14.0, 22.3, 28.8,
33.3, 101.4, 128.6, 130.06, 130.10, 133.4, 157.0, 164.9.
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Hept-1-en-2-yl benzoate (2ma)25
Benzoic acid (122 mg, 1.0 mmol) was converted with 1ꢀheptyne (192 mg, 2.0 mmol) for 3 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (98:2, v/v) as eluent,
1
yielding the title compound as pale yellow liquid (212 mg, 97 %). H NMR (CDCl3, 500.3 MHz): δ 0.88–0.92
(m, 3H), 1.31–1.38 (m, 4H), 1.50–1.59 (m, 2H), 2.31–2.37 (m, 2H), 4.82–4.85 (m, 1H), 4.85–4.88 (m, 1H),
7.44–7.50 (m, 2H), 7.55–7.62 (m, 1H), 8.06–8.11 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 14.1, 22.5, 26.4,
31.3, 33.5, 101.4, 128.6, 130.0, 130.1, 133.4, 157.0, 164.9.
Oct-1-en-2-yl benzoate (2na)11f,12a,12c,18b,23,29e
Benzoic acid (122 mg, 1.0 mmol) was converted with 1ꢀoctyne (220 mg, 2.0 mmol) for 3 h at 70 °C. The product
was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (98:2, v/v) as eluent, yielding the
title compound as yellow liquid (226 mg, 97 %). 1H NMR (CDCl3, 500.3 MHz): δ 0.88 (t, J = 6.9 Hz, 3H), 1.24–
1.40 (m, 6H), 1.49–1.58 (m, 2H), 2.31–2.36 (m, 2H), 4.83–4.85 (m, 1H), 4.85–4.87 (m, 1H), 7.44–7.50 (m, 2H),
7.56–7.62 (m, 1H), 8.06–8.13 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 14.2, 22.7, 26.6, 28.8, 31.7, 33.6,
101.5, 128.6, 130.02, 130.05, 133.4, 157.0, 164.9.
Non-1-en-2-yl benzoate (2oa)
Benzoic acid (122 mg, 1.0 mmol) was converted with 1ꢀnonyne (248 mg, 2.0 mmol) for 3 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (98:2, v/v) as eluent,
1
yielding the title compound as pale yellow liquid (238 mg, 97 %). H NMR (CDCl3, 500.3 MHz): δ 0.88 (t, J =
7.0 Hz, 3H), 1.22–1.40 (m, 8H), 1.48–1.60 (m, 2H), 2.30–2.39 (m, 2H), 4.80–4.85 (m, 1H), 4.85–4.88 (m, 1H),
7.44–7.50 (m, 2H), 7.56–7.62 (m, 1H), 8.06–8.13 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 14.2, 22.8, 26.7,
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29.1, 29.2, 31.9, 33.6, 101.4, 128.6, 130.06, 130.11, 133.4, 157.0, 164.9. HRMS (ESIꢀTOF) m/z: [M + Na]+
Calcd for C16H22O2Na 269.1512; Found 269.1536.
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1-Phenylvinyl 2-bromoacetate (2ab)35
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2ꢀBromoacetic acid (139 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at 70
°C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as
1
eluent, yielding the title compound as yellow liquid (222 mg, 92 %). H NMR (CDCl3, 500.3 MHz): δ 4.02 (s,
2H), 5.11 (d, J = 2.6 Hz, 1H), 5.52 (d, J = 2.6 Hz, 1H), 7.30–7.41 (m, 3H), 7.49–7.55 (m, 2H). 13C NMR (CDCl3,
125.7 MHz): δ 25.5, 102.5, 125.0, 128.7, 129.4, 133.7, 152.9, 165.4.
1-Phenylvinyl pivalate (2ac)25
Pivalic acid (102 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 3 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as eluent,
yielding the title compound as yellow liquid (133 mg, 65 %). 1H NMR (CDCl3, 500.3 MHz): δ 1.36 (s, 9H), 4.98
(d, J = 2.0 Hz, 1H), 5.45 (d, J = 2.1 Hz, 1H), 7.29–7.38 (m, 3H), 7.43–7.49 (m, 2H). 13C NMR (CDCl3, 125.7
MHz): δ 27.3, 39.3, 101.9, 125.0, 128.6, 129.0, 134.9, 153.5, 176.7.
1-Phenylvinyl 3-phenylpropanoate (2ad)
3ꢀPhenylpropanoic acid (150 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at
70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as
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eluent, yielding the title compound as yellow solid (197 mg, 78 %). M.p.: 50 °C. H NMR (CDCl3, 500.3 MHz):
δ 2.90–2.96 (m, 2H), 3.10 (t, J = 7.7 Hz, 2H), 5.01 (d, J = 2.2 Hz, 1H), 5.50 (d, J = 2.2 Hz, 1H), 7.27–7.41 (m,
10H). 13C NMR (CDCl3, 125.7 MHz): δ 30.9, 35.9, 102.2, 124.9, 126.5, 128.5, 128.6, 128.7, 129.0, 134.2, 140.2,
153.0, 171.1. HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C17H16O2Na 275.1043; Found 275.1028.
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1-Phenylvinyl 2-(2-methoxyphenyl)acetate (2ae)
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2ꢀMethoxyphenylacetic acid (166 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2
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h at 70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1,
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v/v) as eluent, yielding the title compound as yellow liquid (207 mg, 77 %). H NMR (CDCl3, 500.3 MHz): δ
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3.85 (s, 3H), 3.89 (s, 2H), 5.07 (d, J = 2.2 Hz, 1H), 5.51 (d, J = 2.2 Hz, 1H), 6.91–6.95 (m, 1H), 6.96–7.01 (m,
1H), 7.27–7.37 (m, 5H), 7.43–7.48 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 36.4, 55.4, 102.0, 110.5, 120.7,
122.6, 125.0, 128.4, 128.88, 128.9, 131.1, 134.4, 153.0, 157.6, 169.9. HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd
for C17H16O3Na 291.0992; Found 291.0989.
1-Phenylvinyl 2-bromo-2-phenylacetate (2af)
αꢀBromophenylacetic acid (215 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h
at 70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v)
as eluent, yielding the title compound as colorless liquid (301 mg, 95 %). 1H NMR (CDCl3, 500.3 MHz): δ 5.07
(d, J = 2.5 Hz, 1H), 5.51 (d, J = 2.5 Hz, 1H), 5.57 (s, 1H), 7.27–7.34 (m, 3H), 7.35–7.40 (m, 2H), 7.40–7.45 (m,
3H), 7.61–7.67 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 46.6, 102.5, 124.9, 128.7, 129.0, 129.1, 129.3, 129.7,
133.6, 135.3, 152.9, 166.4. HRMS (ESIꢀTOF) m/z: [M – HBr]+ Calcd for C16H11O2 235.0754; Found 235.0776.
1-Phenylvinyl 2,2-diphenylacetate (2ag)
Diphenylacetic acid (212 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at 70
°C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
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eluent, yielding the title compound as pale yellow liquid (300 mg, 96 %). H NMR (CDCl3, 500.3 MHz): δ 5.04
(d, J = 2.3 Hz, 1H), 5.25 (s, 1H), 5.47 (d, J = 2.3 Hz, 1H), 7.21–7.25 (m, 4H), 7.27–7.34 (m, 3H), 7.34–7.39 (m,
4H), 7.39–7.44 (m, 4H). 13C NMR (CDCl3, 125.7 MHz): δ 57.1, 102.2, 124.9, 127.6, 128.4, 128.8, 128.9, 134.1,
138.0, 153.0, 170.5. HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C22H18O2Na 337.1199; Found 337.1199.
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1-Phenylvinyl 2-(thiophen-2-yl)acetate (2ah)
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2ꢀThiopheneacetic acid (142 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at
70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as
eluent, yielding the title compound as yellow liquid (210 mg, 86 %). 1H NMR (CDCl3, 500.3 MHz): δ 4.08 (d, J
= 0.8 Hz, 2H), 5.08 (d, J = 2.3 Hz, 1H), 5.50 (d, J = 2.3 Hz, 1H), 7.00–7.03 (m, 1H), 7.04–7.07 (m, 1H), 7.27–
7.29 (m, 1H), 7.31–7.34 (m, 3H), 7.38–7.42 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 35.6, 102.4, 124.9,
125.5, 127.1, 127.4, 128.6, 129.1, 134.1, 134.4, 153.0, 168.6. HRMS (ESIꢀTOF) m/z: [M + K]+ Calcd for
C14H12O2SK 283.0190; Found 283.0176.
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1-Phenylvinyl furan-2-carboxylate (2ai)
2ꢀFuroic acid (112 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as eluent,
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yielding the title compound as yellow liquid (197 mg, 92 %). H NMR (CDCl3, 500.3 MHz): δ 5.19 (d, J = 2.4
Hz, 1H), 5.59 (d, J = 2.4 Hz, 1H), 6.59 (dd, J = 3.5 Hz, 1.8 Hz, 1H), 7.30–7.39 (m, 4H), 7.51–7.56 (m, 2H), 7.67
(dd, J = 1.7 Hz, 0.8 Hz, 1H). 13C NMR (CDCl3, 125.7 MHz): δ 102.7, 112.3, 119.5, 125.1, 128.7, 129.2, 134.2,
144.1, 147.3, 152.5, 156.7. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd for C13H11O3 215.0703; Found 215.0714.
1-Phenylvinyl 2-hydroxybenzoate (2aj)
Salicylic acid (138 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at 70 °C. The
product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as eluent,
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yielding the title compound as yellow liquid (224 mg, 93 %). H NMR (CDCl3, 500.3 MHz): δ 5.22 (d, J = 2.5
Hz, 1H), 5.65 (d, J = 2.5 Hz, 1H), 6.99–7.03 (m, 1H), 7.05–7.09 (m, 1H), 7.35–7.43 (m, 3H), 7.53–7.59 (m, 3H),
8.12–8.16 (m, 1H), 10.52 (s, 1H). 13C NMR (CDCl3, 125.7 MHz): δ 102.9, 111.9, 118.0, 119.6, 124.9, 128.8,
129.4, 130.3, 133.9, 136.6, 152.8, 162.3, 168.7. HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C15H12O3Na
263.0679; Found 263.0685.
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1-Phenylvinyl 2-acetoxybenzoate (2ak)
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2ꢀAcetoxybenzoic acid (180 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 2 h at
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70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (9:1, v/v) as
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eluent, yielding the title compound as yellow liquid (277 mg, 98 %). H NMR (CDCl3, 500.3 MHz): δ 2.31 (s,
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3H), 5.17 (d, J = 2.4 Hz, 1H), 5.63 (d, J = 2.4 Hz, 1H), 7.20 (dd, J = 8.1 Hz, 1.0 Hz, 1H), 7.32–7.43 (m, 4H),
7.53–7.58 (m, 2H), 7.65 (ddd, J = 8.1 Hz, 7.5 Hz, 1.7 Hz, 1H), 8.26 (dd, J = 7.9 Hz, 1.6 Hz, 1H). 13C NMR
(CDCl3, 125.7 MHz): δ 21.0, 102.5, 122.4, 124.2, 124.9, 126.3, 128.6, 129.1, 132.3, 133.8, 134.7,151.3, 152.9 ,
162.6, 169.8. HRMS (ESIꢀTOF) m/z: [M + Na–C(O)CH2]+ Calcd for C15H12O3Na 263.0679; Found 263.0710.
1-Phenylvinyl 2,3,4,5,6-pentafluorobenzoate (2al)
Pentafluorobenzoic acid (212 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 1 h at
70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate (95:5, v/v) as
eluent, yielding the title compound as orangeꢀbrown solid (308 mg, 98 %). M.p.: 67 °C. 1H NMR (CDCl3, 500.3
MHz): δ 5.24 (d, J = 2.7 Hz, 1H), 5.61 (d, J = 2.7 Hz, 1H), 7.36–7.42 (m, 3H), 7.52–7.58 (m, 2H). 13C NMR
(CDCl3, 125.7 MHz): δ 103.2, 107.5–107.9 (m), 125.6, 128.8, 129.5, 133.4, 136.7–139.2 (m), 142.5–142.9 (m),
144.6–147.0 (m), 153.0, 157.1–157.4 (m). HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C15H7F5O2Na 337.0258;
Found 337.0290.
1-Phenylvinyl [1,1'-biphenyl]-2-carboxylate (2am)
1,1’ꢀBiphenylꢀ2ꢀcarboxylic acid (198 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol)
for 3 h at 70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate
(9:1, v/v) as eluent, yielding the title compound as yellow liquid (228 mg, 76 %). 1H NMR (CDCl3, 500.3 MHz):
δ 4.90 (d, J = 2.2 Hz, 1H), 5.42 (d, J = 2.2 Hz, 1H), 7.29–7.54 (m, 12H), 7.60–7.65 (m, 1H), 8.02–8.06 (m, 1H).
13C NMR (CDCl3, 125.7 MHz): δ 101.9, 125.0, 127.4, 127.5, 128.3, 128.5, 128.7, 128.9, 130.1, 130.4, 131.1,
131.8, 134.3, 141.1, 142.9, 153.2, 166.8. HRMS (ESIꢀTOF) m/z: [M + Na]+ Calcd for C21H16O2Na 323.1043;
Found 323.1039.
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1-Phenylvinyl 1-naphthoate (2an)
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1ꢀNaphthoic acid (172 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 6 h at 70 °C.
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yielding the title compound as yellow liquid (235 mg, 86 %). H NMR (CDCl3, 500.3 MHz): δ 5.25 (d, J = 2.2
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Hz, 1H), 5.66 (d, J = 2.2 Hz, 1H), 7.34–7.40 (m, 3H), 7.55–7.66 (m, 5H), 7.91–7.95 (m, 1H), 8.10–8.14 (m, 1H),
8.50–8.55 (m, 1H), 9.02–9.07 (m, 1H). 13C NMR (CDCl3, 125.7 MHz): δ 102.6, 124.7, 125.1, 125.8, 126.0,
126.6, 128.4, 128.76, 128.80, 129.1, 131.3, 131.9, 134.1, 134.5, 134.6, 153.5, 165.5. HRMS (ESIꢀTOF) m/z: [M
+ Na]+ Calcd for C19H14O2Na 297.0886; Found 297.0918.
1-Phenylvinyl anthracene-9-carboxylate (2ao)
Anthracene 9ꢀcarboxylic acid (222 mg, 1.0 mmol) was converted with phenylacetylene (204 mg, 2.0 mmol) for 8
h at 70 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/diethyl ether (4:1,
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v/v) as eluent, yielding the title compound as yellow solid (261 mg, 81 %). M.p.: 122 °C. H NMR (CDCl3,
500.3 MHz): δ 5.53 (d, J = 2.6 Hz, 1H), 5.73 (d, J = 2.5 Hz, 1H), 7.39–7.43 (m, 3H), 7.51–7.60 (m, 4H), 7.64–
7.68 (m, 2H), 8.05–8.09 (m, 2H), 8.16–8.21 (m, 2H), 8.60 (s, 1H). 13C NMR (CDCl3, 125.7 MHz): δ 102.8,
125.0, 125.5, 125.7, 126.9, 127.4, 128.8, 128.9, 129.4, 130.1, 131.2, 134.7, 153.6, 167.9. HRMS (ESIꢀTOF) m/z:
[M + H]+ Calcd for C23H17O2 325.1223; Found 325.1228.
1-(4-Methoxyphenyl)vinyl 2,3,4,5,6-pentafluorobenzoate (2bl)
Pentafluorobenzoic acid (212 mg, 1.0 mmol) was converted with 4ꢀmethoxyphenylacetylene (264 mg, 2.0 mmol)
for 4 h at 25 °C. The product was purified by silicaꢀgel column chromatography using nꢀhexane/ethyl acetate
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(95:5, v/v) as eluent, yielding the title compound as pale yellow solid (336 mg, 98 %). M.p.: 99 °C. H NMR
(CDCl3, 500.3 MHz): δ 3.83 (s, 3H), 5.12 (d, J = 2.7 Hz, 1H), 5.46 (d, J = 2.7 Hz, 1H), 6.88–6.93 (m, 2H), 7.44–
7.50 (m, 2H). 13C NMR (CDCl3, 125.7 MHz): δ 55.5, 101.2, 107.7–108.1 (m), 114.2, 126.0, 126.7, 136.7–139.2
(m), 142.5–142.9 (m), 144.6–147.0 (m), 152.9, 157.1–157.4 (m), 160.7. HRMS (ESIꢀTOF) m/z: [M + H]+ Calcd
for C16H10F5O3 345.0545; Found 345.0542.
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ASSOCIATED CONTENT
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Supporting Information
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Additional catalytic results and the H and 13C{1H} NMR spectra of all catalysis products can be found in the
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supporting information.
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: heinrich.lang@chemie.tuꢀchemnitz.de. Phone: +49 (0) 371ꢀ531ꢀ21210. Fax: +49 (0)371ꢀ531ꢀ21219.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
We are grateful to the Fonds der Chemischen Industrie (FCI) for financial support. J.J. thanks the FCI for a
Chemiefonds Fellowship.
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(32) The reaction conditions were adopted from ref. 31. It was found that an acid/alkyne ratio of 1:2 is not
mandatory for the reaction, as almost the same results were obtained by the usage of less alkyne (Table S4 in the
Supporting Information).
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(33) The positive impact of the AgOTf may arise from a combination of the following effects: i) alkyne
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