Hydration of terminal alkynes catalyzed by cobalt corrole complex

Article abstract of DOI:10.1016/j.tetlet.2020.152426

Cobalt(III) corrole was firstly applied to the hydration of terminal alkynes. The alkyne hydration proceeded in good to excellent yield with 0.03 to 0.3 mol% cobalt corrole catalyst loading. A wide range of substrates were tolerated. Particularly, the reaction can give 90% yield in a gram scale experiment.

Full text of DOI:10.1016/j.tetlet.2020.152426

Tetrahedron Letters xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Hydration of terminal alkynes catalyzed by cobalt corrole complex
⇑
Jia-Wei Lai, Zhao-Yang Liu, Xiao-Yan Chen, Hao Zhang, Hai-Yang Liu
Department of Chemistry, Key Laboratory of Functional Molecular Engineering of Guangdong Province, South China University of Technology, Guangzhou 510640, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Cobalt(III) corrole was firstly applied to the hydration of terminal alkynes. The alkyne hydration pro-
ceeded in good to excellent yield with 0.03 to 0.3 mol% cobalt corrole catalyst loading. A wide range of
substrates were tolerated. Particularly, the reaction can give 90% yield in a gram scale experiment.
Ó 2020 Elsevier Ltd. All rights reserved.
Received 2 June 2020
Revised 14 August 2020
Accepted 30 August 2020
Available online xxxx
Keywords:
Cobalt(III) corrole
Hydration
Terminal alkynes
Introduction
optimized conditions. Gram scale test showed 90% yield with 300
TON, demonstrating its practical use.
Ketones are the important building blocks in organic synthesis
[
1]. Catalytic hydration of CAC triple bond is the simplest and most
Results and discussion
atom economical method for constructing ketones [2]. Although
the mercury catalyst can well catalyze the hydration of alkynes,
its application is largely limited due to the high toxicity of mercury
Firstly, we optimized the condition of the hydration of terminal
alkynes. We chose phenylacetylene as the standard substrate,
MeOH as the solvent and cobalt corrole as catalyst (Table 1). When
methanol solution of phenylacetylene (1a, 0.50 mmol), cobalt cor-
[
3]. In this connection, many other catalysts, such as Au [4], Ag [5],
Pd [6], Ir [7], Ru [8], Rh [9], Pt [10], Sn-W [11], Bi [12], Fe [13], Cu
14], Co [15] complexes and CF SO H/CF CH OH [16] have been
[
3
3
3
2
3 2 4
role (F15CCo-PPh , 0.3 mol%), H SO (2 mol%) and water (4.4
developed. Among these catalysts, cobalt catalyst is noteworthy
equiv.) was heated at 80 °C for 12 h under an aerobic atmosphere
in a closed glass vessel, 1a was totally expended, giving acetophe-
none (2a) in 100% yield (entry 1). When the sulfuric acid loading
was reduced to 1 mol% and the reaction time was extended to
due to its low cost, high efficiency and high selectivity. N-based
III
ligands (Fig. 1), L1-L5, cobalt complexes, eg. Co porphyrin [17a]
III
and its polymeric micelles [17c], Co(III)-salen [17b], Co
Porphyrin metal–organic frameworks [17d] and cobaloxime [17e]
have been successfully used in the hydration of terminal alkynes.
Corrole is an analogue of porphyrin, which is a trivalent anionic
ligand with three pyrrole NAH protons in inner ring (Fig. 1, F15C)
2
0 h, the yield of acetophenone was only 78% (entry 2). When low-
ered the reaction temperature, the higher yield can be obtained by
prolonging the reaction time or increasing the amount of acid (en-
try 3–4). To our great delight, we were able to achieve a relatively
high conversion rate by reducing the catalyst loading to 0.03 mol%,
though needing longer times and more acid (entry 5–7). The yield
of acetophenone (2a) was almost unaffected whether the reaction
was carried out under aerobic or anaerobic conditions (entry 8).
We still used alcohols with higher steric hindrance as the reaction
medium, and found that the higher steric hindrance, the lower
conversion rate of the substrate (entry 9–10), which may be due
to the fact that rate-determining step of the hydration of alkynes
catalyzed by cobalt corrole is the attack of a second alcohol to
the enol ether intermediate [12,20]. In addition, the reaction could
not proceed in the absence of cobalt corrole or when cobalt corrole
was replaced by cobalt acetate (entry 11–12). This indicates that
the corrole ligand plays an extremely important role in the
[
18]. Recently, great progress has been made in the application of
metal corrole in catalytic oxidation of olefin [19a,b], oxygen evolu-
tion reaction [19b,e,f], hydrogen evolution reaction [19c,f,g] and
oxygen reduction reaction [19d,e,f]. To the best of our
knowledge, metal corrole has not been used in the catalytic
hydration of terminal alkynes. In this communication, we wish to
report the tris-(pentafluorophenyl)corrole (Fig. 1, F15C) cobalt
complex catalyzed hydration of terminal alkynes to ketone. It
turned out cobalt corrole exhibit excellent performance with
catalyst loading as low as 0.03 mol% and nearly 100% yield under
⇑
Corresponding author.
E-mail address: chhyliu@scut.edu.cn (H.-Y. Liu).
https://doi.org/10.1016/j.tetlet.2020.152426
040-4039/Ó 2020 Elsevier Ltd. All rights reserved.
0
Please cite this article as: J.-W. Lai, Z. Y. Liu, X. Y. Chen et al., Hydration of terminal alkynes catalyzed by cobalt corrole complex, Tetrahedron Letters,
https://doi.org/10.1016/j.tetlet.2020.152426

J.-W. Lai et al.
Tetrahedron Letters xxx (xxxx) xxx
1
j). This may be due to the formation of a cationic transition state
(
D in scheme 3) in the rate-determining step [17a]. To our delight,
acid-sensitive functional groups such as amino (1e), cyano (1j),
carboxylic esters (1m), and carbon–carbon double bonds (1n)
groups were not destroyed under the condition of sulfuric acid.
When using 2 mol% sulfuric acid and the reaction time is 180 h,
the yield of 2j is 64%. When the acid loading is increased to 20%,
the yield of 2j can be increased to 92% in 108 h reaction time.
Interestingly, by adjusting the quantity of the acid and the
reaction time, which can control whether p-diethylnylbenzene
molecule (1k or 1 l) is retained a alkynyl, it can provide methyl
ketone containing alkynyl (2k) or methyl ketone containing two
carbonyls (2l). Doing everything we can, we did not find other
alkynes hydration catalyst with the performance. For aliphatic
substituents, it seems that the longer carbon chain, the higher
yield (2o and 2p).
Fig. 1. Ligands used for cobalt catalyst in hydration of alkynes.
To highlight the utility of this practical protocol for the synthe-
sis of methyl ketones, we conducted gram-scale reactions under
aerobic condition (see the Electronic Supplementary Information
for the detailed procedure) and obtained 90% isolated yield
(Scheme 1). Beside, the column chromatography recovering cata-
lyst continued to be used for the hydration of alkynes and gave
87% yield of acetophenone (2a). The yield of acetophenone did
not decrease much, indicating that cobalt corrole was particularly
stable in this system (Scheme 2).
Based on the reported pathway of cobalt-catalyzed hydration of
alkynes, there may be two mechanisms for cobalt corrole-cat-
alyzed hydration of alkynes, one is a gem-diether hydration path-
way [17a,e] and the other is an enol ether hydration pathway
[17b]. We have used phenylacetylene and 4-ethynylanisole as
substrates for the reaction under anhydrous conditions, but the
gem-diether intermediate could not be found. Therefore, the
current catalytic reaction may go through the enol ether
hydration pathway. The proposed catalytic cycle is depicted in
Scheme 3. It may go through the five steps: (1) Coordination
between the central metal and alkynes; (2) One-step
hydroalkoxylation with methanol; (3) Protonation of Co(III)-enol
hydration of alkynes. Unfortunately, this reaction cannot take place
without the acid (entry 13). Moreover, We have carried out the
optimization experiment of water amount and found there is no
big differences within 1.0–4.4 equiv. of water. With further
increasing of water, the yield will decrease (Table S1, entry 14–
8). We have tested the effect of acid additives, and found the
stronger the acidity gave better performance (Table S1, entry 15,
9–21).
With the optimized conditions in hand, we then examined the
1
1
scope of the reaction (Table 2). Generally, a wide range of terminal
alkynes containing electronically varied aromatic substituents (1a-
m) and aliphatic substituents (1n-1p) reacted smoothly with
1
0
(
.3 mol% F15CCo-PPh at 80 °C, yielding the corresponding ketones
3
2a-2p) in high yields (The average yield is 90%). However, the
electronic properties of aryl groups in aromatic alkynes have
noticeable effects on this hydration of alkynes. For instance, aro-
matic alkynes containing electron-rich aryl groups (1b-1e) reacted
better than those containing electron-deficient aryl groups (1i and
Table 1
a
Optimization of reaction conditions.
Entry
Catalyst (mol%)
H
2
SO
4
(mol%)
Temp. (°C)
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
0.3
0.3
0.3
0.3
0.03
0.03
0.03
0.3
0.3
0.3
–
2
1
2
20
2
4
20
2
2
2
4
4
80
80
50
R.T.
80
80
80
80
80
80
80
80
80
12
20
100
78
99
82
65
70
90
99
80
168
216
120
120
120
12
12
12
12
12
c
8
9
d
1
1
1
1
0e
1
2
10
N.R.
N.R.
N.R.
f
0.3
0.3
3
–
12
a
Reaction conditions: 0.5 mmol of alkyne 1a, Cat. (0.3 mol%) in MeOH (0.5 mL), H
condition.
2
SO
4
(2 mol%) in MeOH (0.5 mL) and 4.4 equivÁH
2
O. Reaction were carried under aerobic
b
The yields was determined by GC using dodecane as an internal standard.
The reaction was carried out under an nitrogen atmosphere.
EtOH as solvent.
c
d
e
f
iPrOH as solvent.
Cobalt acetate as catalyst. R.T. = Room Temperature. N.R. = No Reaction.
2

J.-W. Lai et al.
Tetrahedron Letters xxx (xxxx) xxx
Table 2
Substrate scope of alkyne hydration catalyzed by F15CCo-PPh
3
.a
2
a, 12 h, 95%
2b, 18 h, 94%
2c, 18 h, 93%
Scheme 3. Proposed mechanism for cobalt corrole catalyzed hydration of alkyne.
2
d, 18 h, 93%
g, 72 h, 98%
2e, 12 h, 99%
2h, 72 h, 99%
2f, 48 h, 99%
2i, 180 h, 68%
ether complex and formation of carbocations [21]; (4) The second
molecule of methanol replaces the protonated enol ether to form
methanol cobalt corrole; (5) Hydrolysis of the protonated enol
ether to give the final product.
In conclusion, we have demonstrated cobalt corrole is an high
efficient for the hydration of a wide array of alkynes at very low
catalyst loading. Further investigations of hydration of internal
alkynes catalyzed by cobalt corrole is still going on in our
laboratory.
2
Declaration of Competing Interest
2
jb, 108 h, 92%
2k, 84 h, 69%
2l , 108 h, 75%
b
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared
to influence the work reported in this paper.
Acknowledgments
c
2
m , 36 h, 98%
2n, 12 h, 96%
Financial support from National Natural Science Foundation of
China (No. 21671068) is gratefully acknowledged.
Appendix A. Supplementary data
2
o, 156 h, 82%
2p, 156 h, 90%
a
Reaction conditions: 0.5 mmol of alkyne 1, F15CCo-PPh
3
(0.3 mol%) in MeOH
O, isolated yield.
in MeOH (0.5 mL).
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tetlet.2020.152426.
(
0.5 mL), H SO
2
4
(2 mol%) in MeOH (0.5 mL) and 4.4 equivÁH
2
b
Reactions were carried under aerobic condition. 20 mol% H
2
SO
4
c
2 4
H SO (20 mol%) in dichloromethane (0.5 mL).
References
[
1] (a) X. Geng, C. Wang, C. Huang, Y. Bao, P. Zhao, Y. Zhou, Y.-D. Wu, L.-L. Feng, A.-
X. Wu, Org. Lett. 22 (2020) 140–144;
(
8
b) A.A. Rajkiewicz, N. Wojciechowska, M. Kalek, ACS Catal. 10 (2020) 831–
41;
(
(
c) I. Yavari, S. Shaabanzadeh, Org. Lett. 22 (2020) 464–467;
d) F.C. Sousa e Silva, N.T. Van, S.E. Wengryniuk, J. Am. Chem. Soc. 142 (2020)
64–69.
Scheme 1. Decagram-scale hydration of 1a.
[2] F. Alonso, I.P. Beletskaya, M. Yus, Chem. Rev. 104 (2004) 3079–3160.
[3] L. Hintermann, A. Labonne, Synthesis 2007 (2007) 1121–1150.
[4] J.A. Goodwin, A. Aponick, Chem. Commun. 51 (2015) 8730–8741.
[5] K.V. Rao, P.S. Prasad, N. Lingaiah, Green Chem. 14 (2012) 1507–1514.
[6] C. Xu, W. Du, Y. Zeng, B. Dai, H. Guo, Org. Lett. 16 (2014) 948–951.
[7] H. Kanemitsu, K. Uehara, S. Fukuzumi, S. Ogo, J. Am. Chem. Soc. 130 (2008)
1
7141–17147.
8] D. Tyagi, R.K. Rai, S.M. Mobin, S.K. Singh, J. Asian, Org. Chem. 6 (2017) 1647–
658.
9] X. Liu, L. Liu, Z. Wang, X. Fu, Chem. Commun. 51 (2015) 11896–11898.
[
1
[
[
10] F. Trentin, A.M. Chapman, A. Scarso, P. Sgarbossa, R.A. Michelin, G. Strukul, D.F.
Wass, Adv. Synth. Catal. 354 (2012) 1095–1104.
Scheme 2. The second run of catalyst.
[11] X. Jin, T. Oishi, K. Yamaguchi, N. Mizuno, Chem. Eur. J. 17 (2011) 1261–1267.
3

J.-W. Lai et al.
Tetrahedron Letters xxx (xxxx) xxx
[
12] S.B. Ötvös, Z. Szécsényi, F. Fülöp, ACS Sustain. Chem. Eng. 7 (2019) 13286–
3293.
[19] (a) H.-Y. Liu, M.H. Mahmood, S.-X.S. Qiu, C.K. Chang, Coord. Chem. Rev. 257
(2013) 1306–1333;
1
[13] J. Park, J. Yeon, P.H. Lee, K. Lee, Tetrahedron Lett. 54 (2013) 4414–4417.
[14] M. Hassam, W.-S. Li, Tetrahedron 71 (2015) 2719–2723.
[15] Y. Lu, X. Caixia, Chin. J. Org. Chem. 37 (2017) 3130–3145.
[16] W. Liu, H. Wang, C.-J. Li, Org. Lett. 18 (2016) 2184–2187.
[17] (a) T. Tachinami, T. Nishimura, R. Ushimaru, R. Noyori, H. Naka, J. Am. Chem.
Soc. 135 (2013) 50–53;
(b) A. Ali, W. Akram, H.-Y. Liu, Molecules 24 (2019) 78;
(c) H. Chen, D.-L. Huang, M.S. Hossain, G.-T. Luo, H.-Y. Liu, J. Coord. Chem. 72
(2019) 2791–2803;
(d) J. Meng, H. Lei, X. Li, J. Qi, W. Zhang, R. Cao, ACS Catal. 9 (2019) 4551–4560;
(e) L. Xie, X. Li, B. Wang, J. Meng, H. Lei, W. Zhang, R. Cao, Angew. Chem. Int.
Ed. 58 (2019) 18883–18887;
(
1
b) S. Wang, C. Miao, W. Wang, Z. Lei, W. Sun, Chin. J. Catal. 35 (2014) 1695–
700;
(f) H. Lei, X. Li, J. Meng, H. Zheng, W. Zhang, R. Cao, ACS Catal. 9 (2019) 4320–
4344;
(
(
c) J. Lu, J. Dimroth, M. Weck, J. Am. Chem. Soc. 137 (2015) 12984–12989;
d) Z. Lin, Z.M. Zhang, Y.S. Chen, W. Lin, Angew. Chem. Int. Ed. 55 (2016)
(g) Y. Chen, Q.H. Fan, M.S. Hossain, S.Z. Zhan, H.Y. Liu, L.P. Si, Eur. J. Inorg.
Chem. 2020 (2020) 491–498.
1
(
6
3739–13743;
e) S. Hou, H. Yang, B. Cheng, H. Zhai, Y. Li, Chem. Commun. 53 (2017) 6926–
929.
[20] D. Zuccaccia, A. Del Zotto, W. Baratta, Coord. Chem. Rev. 396 (2019) 103–116.
[21] (a) J.P. Richard, K.B. Williams, J. Am. Chem. Soc. 129 (2007) 6952–6961;
(b) W.-Y. Tsang, J.P. Richard, J. Am. Chem. Soc. 131 (2009) 13952–13962.
[
18] (a) J.F. Barata, M.G.A.P. Neves, M.A.F. Faustino, A.C. Tomé, J.A. Cavaleiro, Chem.
Rev. 117 (2017) 3192–3253;
(
b) A. Ghosh, Chem. Rev. 117 (2017) 3798–3881.
4