Greener and regioselective ring opening of epoxides with TMSCN using potassium salts of magnetic carbon nitride

Article abstract of DOI:10.1007/s00706-020-02689-0

Abstract: Potassium salts of magnetic graphitic carbon nitride (Fe₃O₄?g-C₃N₄-K) synthesized and proved to be a green and recyclable catalyst for rapid and regioselective ring opening of epoxides with TMSCN, yiel

Full text of DOI:10.1007/s00706-020-02689-0

Monatshefte für Chemie - Chemical Monthly (2020) 151:1597–1602
https://doi.org/10.1007/s00706-020-02689-0
ORIGINAL PAPER
Greener and regioselective ring opening of epoxides with TMSCN
using potassium salts of magnetic carbon nitride
Mostafa Saadat1 · Mahnaz Qomi1 · Najmedin Azizi2
Received: 9 May 2020 / Accepted: 14 September 2020 / Published online: 14 October 2020
© Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract
Potassium salts of magnetic graphitic carbon nitride (Fe3O4@g-C3N4-K) synthesized and proved to be a green and recycla-
ble catalyst for rapid and regioselective ring opening of epoxides with TMSCN, yielding the β-hydroxynitrile ring-opened
products under mild reaction conditions. It is manageable to large-scale preparation with simple instruments and gives the
desired compounds in short reaction times with good-to-excellent yields (73–95%) under solvent-free conditions. Magnetic
separation protocol has used to achieve a simple separation and reuse of catalysts from unpurifed reaction mixtures using
external magnets without loss of catalytic operation after fve cycles.
Graphic abstract
Keywords Ionic catalyst · Graphitic carbon nitride · TMSCN · Ring opening of epoxides · Hydroxy nitrile
Introduction
energy sources, such as microwaves, ultrasound, and ball
milling alternative to conventional heating to increase the
efciency of the reactions [6].
Green Chemistry, the design of chemical processes to
minimize the environmental pollution caused by solvents
in industry and retail, is a comprehensive strategy [1, 2].
Solvent-free synthesis is receiving signifcant as a tool for
the combination of a broad range of useful and essential bio-
logically active compounds to improve old methodologies
making them more clean, safe, and comfortable to perform
[3–5]. Furthermore, solvent-free reactions can moreover be
enhanced to take advantage of utilizing nonconventional
Carbon-based composites are smart support material for
potential applications in the feld of gas adsorption, het-
erogeneous catalysis, water treatment, energy storage, and
conversion devices [7, 8]. Among the carbon composite,
carbon nitrides (CNs) are fascinating materials with distinc-
tive properties due to their high chemical and mechanical
stability, availability, and ease of functionalization [9–11].
The features of the CN materials mostly controlled by the
structure, nitrogen contents, source of starting material,
temperature, and carbon precursors [12–14]. In this context,
it is possible to optimize their properties such as surface
areas and tunable pore diameters for specifc applications.
Furthermore, CN materials can straightforwardly produce
from cheap nitrogen-rich organic molecules such as mela-
mine or urea derivatives under thermal treatment [15–18].
* Najmedin Azizi
azizi@ccerci.ac.ir
1
Active Pharmaceutical Ingredients Research Center
(APIRC), Tehran Medical Sciences, Islamic Azad
University, Tehran, Iran
2
Chemistry and Chemical Engineering Research Center
of Iran, P.O. Box 14335-186, Tehran, Iran
Vol.:(0123456789)
1 3

1598
M. Saadat et al.
Therefore, signifcant progress has been made recently not
only on the design of novel and smart CN materials but also
on the new area of photocatalytic application [19–22]. How-
ever, to the best of our knowledge, CN materials, have not
investigated for the ring opening of epoxide for the synthesis
of β-hydroxynitrile derivatives in the literature.
are stereoselective, proceeding with inversion of confgu-
ration [34–37]. β-Hydroxynitriles are essential and highly
versatile building blocks in the industrial organic synthesis.
They have extensively used for the combination of bioac-
tive natural products and a variety of fne chemicals [38,
39]. Therefore, there is a signifcant current interest in the
ring opening of epoxides [40–43]. In the literature, the regi-
oselective ring opening of epoxides with various cyanation
agents, for example, hydrogen cyanide, cyanide, TMSCN,
and acetone cyanohydrin for the preparation of the titled
compounds were reported [38, 41, 44–48]. They are usu-
ally exemplifed for acid or base catalyzed under requires
extended reaction times and lack noticeable regioselectivity
when dealing with sensitive and bulky epoxides.
In recent years, the concept of magnetic nanomaterials
has enriched a rapidly growing feld of catalysis for the
development of sustainable processes [23, 24]. Magnetic
separation is a versatile and often cost-saving technique in
many critical areas of interest and makes a positive impact
on a wide variety of industrial processes are procedures [25].
Magnetic separation obviates the requirement of catalyst fl-
tration or centrifugation after completion of the reaction and
provided high catalytic activity and stability in diagnostic
purposes [26–28].
The chemistry of three-membered rings, such as epox-
ides, is remarkable heterocyclic ring systems [29–31].
Epoxides are considered as the reactive and readily avail-
able synthons of organic transformations, because they are
easily prepared from a pure starting material and cleaved
with diferent nucleophiles under a broad range of conditions
giving a wide range of products [32, 33]. One promising
feature of the ring-opening reactions of epoxides is that they
Results and discussion
In continuation of the development of a versatile catalyst and
promoter for various organic transformations [49–53], we
began to explore the catalytic activity of the graphitic carbon
nitride derivatives in organic synthesis. It seems that g-C3N4
are becoming advantageous heterogeneous carbon-based
catalysts due to the simple product isolations using only
Table 1 Optimization of reaction conditions
Entry
Solvent
Catalyst (30 mg)
Temp./°C
Time/h
Yield/%a
1
2
3
4
5
6
7
8
–
–
–
–
–
–
–
–
g-C3N4
Fe3O4
Fe3O4@g-C3N4
g-C3N4-SO3H
g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
Fe3O4@g-C3N4-K
–
rt
rt
rt
rt
rt
rt
40
60
70
70
70
70
70
70
70
70
70
6
6
6
6
6
6
6
6
3
3
3
3
3
3
3
3
3
20
28
35
46
52
54
62
90
95
51
59
62
58
45
75
71
36
9
–
10
11
12
13
14
15
16
17
Ethyl acetate
Toluene
CH3CN
Ethanol
Water
DMSO
CHCl3
Neat
aIsolated yields
1 3

Greener and regioselective ring opening of epoxides with TMSCN using potassium salts of magnetic…
1599
fltrations, and synergistic catalytic efects by acid and base
site on the surface of the graphitic carbon nitride. In this
paper, we report the application of magnetic g-C3N4-K as the
selective and efcient catalyst to an epoxide ring-opening
reaction with TMSCN to convert functionalized epoxides to
β-hydroxycyanides under solvent-free conditions.
catalysts under solvent-free condition revealed that magnetic
g-C3N4-K (30 mg) was the most efective catalyst in terms
of yield and time (Table 1, entries 1–9). With the suitable
g-C3N4-based catalyst for the reaction decided, we optimized
diferent solvents and temperatures. No response detected
in the absence of the catalyst and reactions in solvents such
as ethyl acetate, toluene, CH3CN, ethanol, water, DMSO,
and CHCl3, gave the desired product in modest yields and
lower regioselectivity in the prolonged reaction time (entries
10–16). The reaction temperature was also studied. When
the model reaction performed at 70 °C under solvent-free
conditions, the best conversion in terms of yields and times
observed.
A series of preliminary tests achieved on the model
reaction of cyclohexene oxide (1.0 mmol) with TMSCN
(1.2 mmol) in the presence of various g-C3N4 catalysts to
determine the best reaction conditions (Table 1). First, to
study the infuence of the functional groups of the g-C3N4
for the reaction, various carbon nitride was prepared accord-
ing to our previous paper [51] and explored for the model
ring-opening reactions. The screening of various g-C3N4 as
Table 2 Ring opening of various epoxides promoted by magnetic support catalyst
aIsolated yields
1 3

1600
M. Saadat et al.
of the epoxide by the g-C3N4 system through electronic
interaction and the proton of NH through a hydrogen
bond. Then, the TMSCN can activated by the nitrogen
provided by the g-C3N4 system. After the nucleophilic
attack of the TMSCN to the activated epoxide, the desired
β-hydroxynitrile generated.
Recyclability and catalytic stability are a crucial feature
of the heterogeneous magnetic catalyst that plays an essen-
tial role in sustainable developments. In this context, fve
runs of ring-opening reactions carried out to investigate the
magnetic recyclability and activity of the prepared magnetic
catalyst. Recycled experiments carried out under the opti-
mized reaction conditions of the model reaction. At the end
of each run, an external magnet used to recover the catalyst.
The recovered catalyst was washed with ethyl acetate and
reused for the next cycling run (Fig. 2). The results revealed
that the prepared magnetic catalyst was stable and active
with excellent and straightforward reusability. The X-ray dif-
fraction (XRD) patterns and as well as the FT-IR spectrum
used to confrm the stability of the reused catalyst, and the
results showed that there is no change in the structure and
morphology of nonmagnetic catalyst.
Fig. 1 Proposed reaction mechanism
100
80
60
40
20
0
1
2
3
4
5
Conclusion
Run
In summary, we have succeeded in establishing a highly
proftable magnetic g-C3N4-K catalytic system in the regi-
oselective ring-opening reactions of epoxide with TMSCN
with good-to-excellent yields in shorter reaction times. The
strong synergistic cooperation between the acidic and basic
sites on the surface of g-C3N4 may play an essential role
in the catalytic process. Magnetic separation protocol has
used to achieve a simple separation and reuse of catalysts
from unpurifed reaction mixtures using external magnets.
Fig. 2 Recyclability experiments of nanocomposite
After establishing the optimal reaction conditions, the
ring-opening reactions of various epoxides with TMSCN
under solvent-free conditions investigated (Table 2). The
reaction occurred practically fast and was accomplished
completely on the magnetic g-C3N4-K system. From the pre-
sent results (Table 2), it is evident that selective cyanolysis
of a range of epoxides with aryl and alkyl groups and dif-
ferent substituents epoxides by TMSCN to obtain the corre-
sponding β-hydroxynitrile in good-to-excellent yields under
mild reaction conditions. All the reactions proceeded quickly
and were complete with 1–3 h. However, the aliphatic epox-
ides are less reactive and more regioselective than the aro-
matic ones. The nucleophilic attack of cyanide occurred at
the less hindered carbon (β-attack) of the aliphatic epoxides.
On the other hand, in the case of aromatic epoxides, mix-
tures of the product were obtained. The regioselectivity and
stereochemistry of the ring-opened product were determined
Experimental
All chemicals were used without further purifcation and
purchased from commercial sources. The purity of desired
products approved by infrared 1H NMR and GC. 1H NMR
spectra recorded on 500 MHz NMR spectrometer using
CDCl3 as a solvent. Melting points reported on Buchi 535
melting point apparatus.
1
by H NMR spectroscopy of the crude products and were
Preparation of potassium salts of magnetic
graphitic carbon nitride (Fe3O4@g‑C3N4‑K)
similar to those of the reported respective β-hydroxynitrile.
The mechanism of the ring-opening reaction of epox-
ide catalyzed by the magnetic g-C3N4-K system illustrated
in Fig. 1. Based on experimental studies, the mechanism
of the model reaction proposed to proceed via activation
The Fe3O4@g-C3N4 used for this study prepared accord-
ing to in our previous works and potassium salts of this
1 3

Greener and regioselective ring opening of epoxides with TMSCN using potassium salts of magnetic…
1601
Scheme 1
Acknowledgements Financial support of this work by Chemis-
try and Chemical Engineering Research Center of Iran is gratefully
appreciated.
composite were synthesized in the aqueous KOH solu-
tion as described here. The mixture of 2 g Fe3O4@g-C3N4
in 100 cm3 of 8 M KOH solution was stirred vigorously
at 80 °C for 24 h using a mechanical stirring apparatus.
The obtained solid washed several times to remove any
redundant KOH, and it was dried overnight and used as a
catalyst (Scheme 1).
References
1. Crabtree RH, Anastas PT (2009) Handbook of Green Chemistry.
Wiley-VCH
2. Gui QW, He X, Wang W, Zhou H, Dong Y, Wang N, Tang JX,
Cao Z, He WM (2020) Green Chem 22:118
General procedure
3. Cave GWV, Raston CL, Scott JL (2001) Chem Commun. https://
doi.org/10.1039/b106677n
A mixture of TMSCN (1.2 mmol), epoxide (1.0 mmol),
and 30 mg Fe3O4@g-C3N4-K was stirred at 70 °C under
solvent-free conditions for the appropriate time (Table 2).
After completion of the reaction (monitored by TLC and
GC), 10 cm3 ethyl acetate added, and the catalyst removed
by the external magnet. The reaction mixture was washed
with 10 cm3 water and organic solvent evaporated under
reduced pressure. In a few cases, the resulting crude prod-
uct was purifed by fash chromatography on silica gel to
aford an analytically pure corresponding product in yields
given in Table 2.
4. Wu C, Lu LH, Peng AZ, Jia GK, Peng C, Cao Z, Tang Z, He WM,
Xu X (2018) Green Chem 20:3683
5. Lu LH, Wang Z, Xia W, Cheng P, Zhang B, Cao Z, He WM (2019)
Chin Chem Lett 30:1237
6. Bruckmann A, Krebs A, Bolm C (2008) Green Chem 10:1131
7. Ong WJ, Tan LL, Ng YH, Yong ST, Chai SP (2016) Chem Rev
116:7159
8. Wang K, Jia Z, Yang X, Wang L, Gu Y, Tan B (2017) J Catal
348:168
9. Wang Y, Wang X, Antonietti M (2012) Angew Chem Int Ed 51:68
10. Zhang M, Liu YH, Shang ZR, Hu HC, Zhang ZH (2017) Catal
Commun 88:39
11. Wang YF, Xu BH, Du YR, Zhang SJ (2018) Mol Catal 457:59
1 3

1602
M. Saadat et al.
12. Thomas A, Fischer A, Goettmann F, Schlögl R, Carlsson JM
(2018) J Mater Chem 18:4893
35. Fringuelli F, Pizzo F, Tortoioli S, Vaccaro L (2003) J Org Chem
68:8248
13. Niu P, Zhang L, Liu G, Cheng HM (2012) Adv Func Mat 22:4763
14. Du YR, Xu BH, Pan JH, Wu YW, Peng XM, Wang YF, Zhang SJ
(2019) Green Chem 21:4792
36. Liu YH, Zhang ZH, Li TS (2008) Synthesis 20:3314
37. Chakraborti AK, Rudrawar S, Kondaskar A (2004) Org Biomol
Chem 2:1277
15. Liu G, Niu P, Sun C, Lu GQ, Cheng HM (2010) J Am Chem Soc
132:11642
38. Chakraborti AK, Kondaskar A, Rudrawar S (2004) Tetrahedron
60:9085
16. Wang X, Maeda K, Chen X, Fu X, Antonietti M (2009) J Am
Chem Soc 131:1680
39. Sabitha G, Babu RS, Rajkumar M, Yadav JS (2002) Org Lett
4:343
17. Jia Z, Wang K, Tan B, Gu Y (2017) ACS Catal 7:3693
18. Zheng Y, Liu J, Liang J, Jaroniec M, Qiao SZ (2012) Energy
Environ Sci 5:6717
40. Liardo E, Rios-Lombardía N, Morís F, González-Sabín J,
Rebolledo F (2016) Org Lett 18:3366
41. Chakraborti AK, Rudrawar S, Kondaskar A (2004) Eur J Org
Chem. https://doi.org/10.1002/ejoc.200400253
42. Konno H, Toshiro E, Hinoda N (2003) Synthesis 14:2161
43. Brahmam Pujala S, Chakraborti AK (2007) J Org Chem 72:3713
44. Seth K, Raha Roy S, Pipaliya BV, Chakraborti AK (2013) Chem
Commun 49:5886
19. Zhou L, Zhang H, Sun H, Liu S, Tade MO, Wang S, Jin W (2016)
Catal Sci Technol 6:7002
20. Zhao Z, Sun Y, Dong F (2015) Nanoscale 7:15
21. Lei Y, Wan Y, Li G, Zhou XY, Gu Y, Fenga J, Wanga R (2017)
Mater Chem Front 1:1541
22. Nagaki M, Tsumur T, Kinumoto T, Toyod M (2019) Carbon
141:580
45. Pujala B, Rana S, Chakraborti AK (2011) J Org Chem 76:8768
46. Iranpoor N, Firouzabadi H, Shekarize M (2003) Org Biomol
Chem 1:724
23. Lu F, Astruc D (2020) Coord Chem Rev 4081:213180
24. Chen MN, Mo LP, Cui ZH, Zhang ZH (2019) Curr Opin Green
Sustain Chem 15:27
47. Lourenco NMT, Monteiro CM, Afonso CA (2010) Eur J Org
Chem 36:6938
25. Lim CW, Lee IS (2010) Nano Today 5:412
26. Li Z, Li M, Bian Z, Kathiraser Y, Kawi S (2016) Appl Catal B:
Environ 1885:324
48. Azizi N, Edrisi M (2016) Tetrahedron Lett 57:525
49. Azizi N, Batebi E, Bagherpour S, Ghafuri H (2012) RSC Adv
2:2289
27. Gao G, Di JQ, Zhang HY, Mo LP, Zhang ZH (2020) J Catal
387:39
50. Azizi N, Mirmashhori B, Saidi MR (2007) Catal Commun 8:2198
51. Azizi N, Saidi MR (2006) Catal Commun 7:224
52. Mirmashhori B, Azizi N, Saidi MR (2006) J Mol Catal A Chem
247:159
28. Zhang M, Liu YH, Shang ZR, Hu HC, Zhang ZH (2017) Catal
Commun 885:39
29. Rawn JD, Ouellette R (2018) Ethers and Epoxides. In: Organic
Chemistry, 2nd edn, chapter 16. Academic Press
30. Parker RE, Isaacs NS (1959) Chem Rev 59:737
31. Chakraborti AK, Kondaskar A (2003) Tetrahedron Lett 44:8315
32. Liu YH, Liu QS, Zhang ZH (2008) J Mol Catal A Chem 296:42
33. Wilson SC, Howard PW, Forrow SM, Hartley JA, Adams LJ, Jen-
kins TC, Kelland LR, Thurston DE (1999) J Med Chem 42:4028
34. Shivani, Chakraborti AK (2007) J MolCatal A Chem 263:137
53. Azizi N, Saidi MR (2005) Org Lett 7:3649
Publisher’s Note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional afliations.
1 3