Reusable rhodium catalyst for the selective transvinylation of sp2-C linked carboxylic acid

Article abstract of DOI:10.1016/j.tetlet.2018.07.039

The vinyl benzoate derivatives were successfully synthesized by the transvinylation reactions that vinyl group transferred from vinyl acetate to aromatic carboxylic acids with the recoverable catalyst RhCl₃·3H₂O. This catalyst features air stable and tolerance of water, good reusable ability, meanwhile, shows high selectivity for aromatic carboxylic acid in the presence of phenolic hydroxyl. With this method, a variety of vinyl benzoate derivatives can be produced with up to 95% yield.

Full text of DOI:10.1016/j.tetlet.2018.07.039

Tetrahedron Letters xxx (2018) xxx–xxx
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Reusable rhodium catalyst for the selective transvinylation
of sp2-C linked carboxylic acid
1
Ruihang Jiang , Zhangpei Chen ,1, Kun Zhan, Lei Liu, Junjie Zhou, Yongjian Ai, Shuang Li,
⇑
⇑
Hongjie Bao, Ze’nan Hu, Li Qi, Jingting Wang, Hong-bin Sun
Department of Chemistry, Northeastern University of China, Shenyang 110819, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
The vinyl benzoate derivatives were successfully synthesized by the transvinylation reactions that vinyl
group transferred from vinyl acetate to aromatic carboxylic acids with the recoverable catalyst
RhCl3Á3H2O. This catalyst features air stable and tolerance of water, good reusable ability, meanwhile,
shows high selectivity for aromatic carboxylic acid in the presence of phenolic hydroxyl. With this
method, a variety of vinyl benzoate derivatives can be produced with up to 95% yield.
Ó 2018 Elsevier Ltd. All rights reserved.
Received 30 May 2018
Revised 10 July 2018
Accepted 13 July 2018
Available online xxxx
Keywords:
Rhodium chloride
Transvinylation
Vinyl benzoate
Vinyl ester
Transesterification
Introduction
research. Among all the synthetic methods, utilizing benzoate acid
and vinyl acetate via transvinylation was an economic pathway
Vinyl esters are widely used in polymer chemistry for their
finely adjusted properties [1]. Particularly, as one of the most
important vinyl esters, vinyl benzoates are widely used in practical
chemicals such as degradable materials, coating materials, adhe-
sive and printing ink [2]. They can also be used in organic synthetic
chemistry like cycloadditions [3], hydroformylations [4], metathe-
sis reactions [5], and Claisen rearrangements [6], enantioselective
cyclopropanation reactions [7], as well as Heck reactions [8].
Vinyl benzoate was practically synthesized by esterification of
carboxylic acids with terminal alkynes, nonetheless, the high cost
of the raw materials decreased the synthetic value of the reaction
(Fig. 1. Entry 1) [9–14]. Other methods for synthetizing vinyl ben-
zoate compounds were also reported such as arylation of esters
[15], thermal decomposition of carbonyl(1-oxoalkyl)metalate salts
[16], decomposition of anhydrides [17], Baeyer-Villiger oxidation
and this research field had received an increasing attention in
recent years. Several catalysts were reported such as [IrCl(cod)]2
[13,20], AuClPPh3 [21] and PdX2(CH3CN)2 (X = Cl, Br) (Fig. 1. Entry
2) [22,23]. However, the AuClPPh3 catalysts and [IrCl(cod)]2 cata-
lyst require harsh reaction conditions and are limited to a narrow
substrate scope. In addition, the efficiency of PdX2(CH3CN)2 cata-
lysts was barely satisfactory, such as the transvinylation reactions
with a catalytic amount of PdCl2(CH3CN)2 resulted in only up to
51% yield. In a word, the above mentioned catalysts usually needed
additional ligand and extra solvent (toluene or THF) to promote the
reactivity and selectivity toward obtaining the corresponding
products with good yields. Herein, as Fig. 1. Entry 3 shown, we
reported
a ligand-free, air-stable and less toxic [24] Rh(III)
catalyzed selective transvinylation reaction to synthesize the vinyl
benzoates under the neat reaction conditions.
of
a,b-unsaturated ketones [18] and so on [19]. However, these
reactions require harsh reaction conditions, additional additives,
and limited to narrow substrate scope. Consequently, reliable
methods toward the facile generation of vinyl benzoates would
be very desirable in both organic synthesis and material science
Results and discussion
Initially, we began our investigation with vinyl acetate and ben-
zoic acid as the model substrates. Considering of developing a con-
venient method for scale-up reaction, the evaluating of several
easy available and air & water stable inorganic compounds as the
catalysts was firstly conducted. After screening an array of cata-
lysts, including some copper, nickel, cobalt salts, and RhCl3Á3H2O
as well as Pd/C, only the last two catalysts could promote this
⇑
Corresponding authors.
E-mail addresses: chenzhangpei@mail.neu.edu.cn (Z. Chen), sunhb@mail.neu.
edu.cn (H.-b. Sun).
1
These authors contributed equally.
https://doi.org/10.1016/j.tetlet.2018.07.039
0040-4039/Ó 2018 Elsevier Ltd. All rights reserved.
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2
R. Jiang et al. / Tetrahedron Letters xxx (2018) xxx–xxx
omy, less amount of solvent and reactant was conducted but
yielded less vinylation product as entry 16 shown. Then, the con-
dition listed in entry 7 was employed as the optimum reaction
condition.
With the optimum reaction conditions in hand, we then exam-
ined the substrate scope of this vinyl ester synthesis method
(Table 2). The general yields of vinyl benzoate were moderate to
excellent. Vinyl benzoates and p-substituted vinyl benzoates were
obtained with excellent yields such as 2a, 2b and 2c. The yields of
m-substituted (2d) and o-substituted (2e) vinyl benzoates were
lower than p-substituted vinyl benzoates, this may due to the
steric effect hindered the transvinylation reaction. Similarly, the
yields of 2h and 2i showed the same pattern. Othersubstrates with
electron-withdrawing group, such as 2j and 2k, were well-toler-
ated and the 1-naphthoic acid substrate also shown the excellent
yields (2l). It is worthy to point out that with both phenolic hydro-
xyl and carboxyl group, we could selectively obtain the carboxyl
group vinylation products employing RhCl3Á3H2O as the catalyst
(2f and 2g). Esterification of phenolic hydroxyl was observed when
this reaction was catalyzed by Wilkinson catalyst, which gave low
selectivity of this reaction. Subsequently, we used the model reac-
tion condition to investigate the reuse ability of this catalyst. After
completion of the transvinylation, the reaction mixture was evap-
orated to remove the organic compounds and thus remained the
rhodium catalyst for further recycling properties investigation.
The residual was then employed as the catalyst to promote the
transvinylation of benzoate acid without addition of extra sodium
formate. The results show that the catalyst is recyclable in 4 con-
secutive runs and the yields of vinyl benzoate, which was deter-
mined by GC with benzoate acid as external standard, were 85%,
71%, 74% and 58%, respectively.
The selectivity comparison of RhCl3Á3H2O catalyst with Wilkin-
son catalyst was then investigated by utilizing the aromatic acid
and aromatic alcohols as the substrates (Table 3). We obtained
the selective vinylation product a1 and a2 without esterification
by-products b1 and b2 with RhCl3Á3H2O as the catalyst. What’s
more, only trace amount of vinylation side-product (4-(vinyloxy)
benzoic acid) relative to a1 was observed (entry 1) and no vinyla-
tion side-product was observed with 3-hydroxybenzoic acid as the
substrate (entry 2). However, the Wilkinson catalyst showed lower
selectivity of vinyl benzoates which preferred to esterification,
yielded the side product b1 and b2 in good conversions. For the
Fig. 1. Methods to synthesis of vinyl esters.
transvinylation reaction with 85% and 32% of yield, respectively
(Table S1 in the supporting information). The assessment of other
reaction parameters was summarized in Table 1. From entry 1 to
entry 7, we screened some other rhodium complex catalysts to
facilitate this reaction. Compared to Rh(acac)3, the Rh(CO)2acac
catalyst showed the moderate catalytic activity with or without
sodium formate (entries 1,2 vs entries 3,4) which implied the
necessity of carbonyl ligand. The CO-contained Rh catalyst such
as RhH(PPh3)3CO was also tested and shown the moderate yields
(entry 5). However, the Rh(PPh3)3Cl and RhCl3Á3H2O exhibited
the highest conversion with HCOONa as the additive. It is notable
that the basic additive is necessary in the reaction which is consid-
ered to promote the generating of CO ligand according to the Jen-
nifer Ziriakus’ report [25]. Considering the moderate price and
without phosphorus ligand, we finally chose RhCl3Á3H2O as the cat-
alyst for further optimizing. From entry 9 to entry 13, several
bases were evaluated and only the sodium formate showed the
best efficiency. The temperature was investigated in entry 14
and entry 15 and decreasing the reaction temperature was harmful
to the reactivity. In addition, for the consideration of atomic econ-
Table 1
Optimization of reaction conditions with benzoic acid substrate.a
Table 2
Synthesis vinyl esters catalyzed by RhCl3Á3H2O.a
Entry
Rh catalyst
Additive
T (°C)
Yieldsb
1
2
3
4
5
6
7
8
Rh(CO)2acac
Rh(CO)2acac
Rh(acac)3
–
80
80
80
80
80
80
80
80
80
80
80
80
80
71
64
80
27%
60%
0%
HCOONa
–
Entry
R
Product
Yield/%
Rh(acac)3
HCOONa
HCOONa
HCOONa
HCOONa
–
0%
RhH(PPh3)3CO
Rh(PPh3)3Cl
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
RhCl3Á3H2O
31%
86%
85%
0%
32%
0%
0%
0%
20%
25%
19%
72%
1
2
3
4
H
2a
2b
2c
2d
2e
2f
2g
2h
2i
85
95
82
61
30
76
74
56
80
76
84
90
4-tBu
4-Me
3-Me
2-Me
4-OH
3-OH
2-Cl
4-Cl
4-Br
4-NO2
1-naphthoic acid
9
NaOAc
5
6b
7b
8b
9b
10b
11b,c
12b
10
11
12
13
14
15
16c
Cl3CCOONa
Na2C2O4
Na2HPO4
HCOONH4
HCOONa
HCOONa
HCOONa
2j
2k
2l
a
a
Conditions: 0.5 mmol benzoic acid, 2 mL vinyl acetate, 2 mmol% Rhodium
Conditions: 0.5 mmol acid, 2 mL vinyl acetate, 2 mmol% RhCl3Á3H2O catalyst,
catalyst, base (0.2 equiv), 24 h.
sodium formate (0.2 equiv), 24 h, yields determined by GC relative to acid external
standard.
b
Yields determined by GC relative to benzoic acid external standard.
0.5 mmol benzoic acid, 1 mL vinyl acetate, 2 mmol% Rhodium catalyst, base (0.2
c
b
Yields determined by HPLC relative to acid external standard.
4 mL vinyl acetate.
c
equiv), 24 h.
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R. Jiang et al. / Tetrahedron Letters xxx (2018) xxx–xxx
3
Table 3
Selectivity of RhCl3Á3H2O compared with Wilkinson catalyst.a
Entry
1
Product A
Product B
Ratio of A:B
100:0b
RhCl3Á3H2O
37:63e
Wilkinson cat.
2
100:0b
52:48e
3
4
100:0b
0:0c
5:95e
0:100d
a
b
c
Reaction conditions, 0.5 mmol substrates, 2 mol% rhodium catalyst, HCOONa 0.2 equiv, 80 °C for 24 h.
Only transvinylation product was found (a1–a3), and the yields of vinyl esters were 76%, 74% and 33% determined by GC–MS, respectively.
None of transvinylation or esterification product were found.
Only esterification product (b4) was found, and the yields were 86% determined by GC–MS.
The conversion of substrates in entries 1–3 were 89%, 73% and 37% respectively.
d
e
phenol substrate, only transvinylation of phenol (a3) was observed
catalyzed by RhCl3Á3H2O while phenol had been mostly esterifi-
cated (b3) catalyzed by Wilkinson catalyst. The RhCl3Á3H2O also
showed catalytic activity for phenol substrate albeit with moderate
efficiency (33% yields). In addition, no transvinylation product (a4)
of benzyl alcohol catalyzed by RhCl3Á3H2O was observed and all
these means that RhCl3Á3H2O shows higher selectivity of carboxyl
than that of phenolic hydroxyl.
In order to further estimate the application possibility, we
applied this attractive protocol to the transvinylation of other car-
boxylic acids. To our delight, the RhCl3Á3H2O catalyst exhibited
good efficiency for the vinylation of sp2-C linked carboxylic acid
towards alkyl carboxylic acid. The yields of 3a and 3b were good
(Table 4). What’s more, the cinnamic acid was applied to this reac-
tion and the yield of 3c was also good.
Jochanan’s reported [27]. However, no esters could be detected
from the GC–MS analysis, this phenomenon confirmed our above
hypothesis. Then we investigated the influence of chloride ions in
the model reaction by changing the ratio of RhCl3Á3H2O to AgBF4
(Table S2 listed in Supporting information) and the results showed
that the chloride ions were necessary to high conversion. What’s
more, we also observed the side production acetic acid in the reac-
tion system, implied that the reaction pathway was transvinylation
rather than transesterification. In order to further understanding
the reaction mechanism, we conducted the XPS experiments to
The reaction mechanism was then investigated. From the
results of optimum reaction conditions, catalysts without CO
ligand couldn’t promote this reaction unless with NaOAc or
HCOONa as the additive. According to the Jennifer Ziriakus’
research, CO ligand could derive from the substrates and solvent
with the assistance of base NaOH, we supposed that the formate
sodium was indispensable to provide CO ligand through dehydra-
tion in our reaction [26]. The vinyl esters would further to hydro-
genate and convert to esters in our reaction conditions if the
formate sodium undergoes the dehydrogenation according to Blum
Table 4
Transvinylation of a
-olefin carboxylic acid.a
Entry
R
Product
Yield (%)
1
2
3
(E)-Me
H
(E)-phenyl
3a
3b
3c
71
67
59
a
Conditions: 0.5 mmol acid, 2 mL vinyl acetate, 2 mmol% RhCl3Á3H2O, sodium
formate (0.2 equiv), 24 h, yields determined by GC relative to acid external
standard.
Fig. 2. Proposed reaction mechanism for transvinylation catalyzed by RhCl3Á3H2O.
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R. Jiang et al. / Tetrahedron Letters xxx (2018) xxx–xxx
analysis the structure of Rh species. As Fig. S1 shown (in Support-
ing information), two peaks of Rh were observed at 314.1 eV and
309.4 eV which corresponded to Rh 3d3/2 level and 3d5/2 level,
assigned to Rh(III) species [28]. These results demonstrated that
the valence state of the Rh species maintained in trivalence.
Based on these facts, we proposed the mechanism for the RhCl3-
Á3H2O catalyzed transvinylation reactions that depicted in Fig. 2.
The intermediate 1 was generated from RhCl3Á3H2O with sodium
formate [29], which underwent coordination with benzoic acid to
form the intermediate 2. Then the intermediate 3 was formed via
addition of the Rh center and the carboxylate ligand to the vinyl
double bond [25]. Sequent, such intermediate transformed to
intermediate 5 through transient intermediate 4. After the b-elim-
ination of acetyl, the vinyl benzoate was generated and the Rh spe-
cies coordinated with benzoic acid to regenerate intermediate 1 to
further facilitate the reaction.
References
[1] S. Harrisson, X. Liu, J.-N. Ollagnier, O. Coutelier, J.-D. Marty, M. Destarac,
Polymers 6 (2014) 1437.
[2] R. Labruere, R. Sicard, R. Cormier, E. Turos, L. West, J. Control. Release 148
(2010) 234.
[3] J. Esquivias, R. Gomez Arrayas, J.C. Carretero, J. Am. Chem. Soc. 129 (2007)
1480.
[4] J.J. Kim, H. Alper, Chem. Commun. (2005) 3059.
[5] Y. Terada, M. Arisawa, A. Nishida, Angew. Chem.-Int. Ed. 43 (2004) 4063.
[6] X. Wei, J.C. Lorenz, S. Kapadia, A. Saha, N. Haddad, C.A. Busacca, C.H.
Senanayake, J. Org. Chem. 72 (2007) 4250.
[7] H. Suematsu, S. Kanchiku, T. Uchida, T. Katsuki, J. Am. Chem. Soc. 130 (2008)
10327.
[8] S. Liu, N. Berry, N. Thomson, A. Pettman, Z. Hyder, J. Mo, J. Xiao, J. Org. Chem. 71
(2006) 7467.
[9] L.J. Goossen, J. Paetzold, D. Koley, Chem. Commun. (2003) 706.
[10] J. Jeschke, T.B. Engelhardt, H. Lang, Eur. J. Org. Chem. (2016) 1548.
[11] J. Jeschke, C. Gabler, H. Lang, J. Org. Chem. 81 (2016) 476.
[12] E. Musengimana, C. Fatakanwa, J. Iran. Chem. Soc. 13 (2016) 253.
[13] H. Nakagawa, Y. Okimoto, S. Sakaguchi, Y. Ishii, Tetrahedron Lett. 44 (2003)
103.
[14] F. Nicks, R. Aznar, D. Sainz, G. Muller, A. Demonceau, Eur. J. Org. Chem. 2009
(2009) 5020.
Conclusions
[15] J. Schranck, A. Tlili, H. Neumann, P.G. Alsabeh, M. Stradiotto, M. Beller,
Chemistry 18 (2012) 15592.
[16] B.C. Soderberg, J. Liu, T.W. Ball, M.J. Turbeville, J. Org. Chem. 62 (1997) 5945.
[17] S.K. Appaye, S.P. Nikumbh, R.R. Govindapur, S. Banerjee, D.S. Bhalerao, U.K.S.
Kumar, Helv. Chim. Acta 97 (2014) 1115.
In conclusion, we reported a rhodium catalyst for selective
transvinylation of aromatic carboxylic acids. The catalyst system
is ligand-free and air & water stable, does not generate esters
byproduct while the substrates contain hydroxyl. The reusability
of the rhodium catalyst shows its high practical application value.
[18] X. Zhang, J. Ye, L. Yu, X. Shi, M. Zhang, Q. Xu, M. Lautens, Adv. Synth. Catal. 357
(2015) 955.
[19] M.I. Weinhouse, K.D. Janda, Synthesis-Stuttgart (1993) 81.
[20] Y. Okimoto, S. Sakaguchi, Y. Ishii, J. Am. Chem. Soc. 124 (2002) 1590.
[21] A. Nakamura, M. Tokunaga, Tetrahedron Lett. 49 (2008) 3729.
[22] P. Rashidi-Ranjbar, F. Piri, Molecules 4 (1999) 135.
[23] A. Hamasaki, S. Maruta, A. Nakamura, M. Tokunaga, Adv. Synth. Catal. 354
(2012) 2129.
[24] K.S. Egorova, V.P. Ananikov, Angew. Chem. Int. Ed. 55 (2016) 12150.
[25] J. Ziriakus, T.K. Zimmermann, A. Pöthig, M. Drees, S. Haslinger, D. Jantke, F.E.
Kühn, Adv. Synth. Catal. 355 (2013) 2845.
[26] H.-C. Böttcher, P. Mayer, Zeitschrift für Naturforschung B 69 (2014) 376.
[27] J. Blum, I. Amer, A. Zoran, Y. Sasson, Tetrahedron Lett. 24 (1983) 4139.
[28] Y. Jung, T. Shin, K. Kim, H. Byun, S.J. Cho, H. Kim, H. Song, Chem. Commun.
(Camb) 53 (2016) 384.
Acknowledgments
This work was financially supported by the Ministry of Science
and Technology (Nos. 2017YFC0906902 and 2017ZX09301032)
and National Natural Science Foundation of China (Nos.
21621003, 21702026).
A. Supplementary data
[29] C. Dragonetti, L. Garlaschelli, P. Mussini, D. Roberto, J. Organomet. Chem. 694
(2009) 3718.
Supplementary data associated with this article can be found, in
the online version, at https://doi.org/10.1016/j.tetlet.2018.07.039.
Please cite this article in press as: R. Jiang et al., Tetrahedron Lett. (2018), https://doi.org/10.1016/j.tetlet.2018.07.039