2022 Volume 5 Issue 2

Open Access

INEOS OPEN, 2022, 5 (2), 38–41  Journal of Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences Download PDF DOI: 10.32931/io2208a

Mixtures of Di- or Triamines and Iodine as Effective Catalysts for the Formation of
Organic Carbonates from Epoxides and CO₂: Effect of 2,2,2-Trifluoroethanol

Abstract

Mixing di- and triamines with iodine leads to the formation of cheap and efficient catalysts for the preparation of cyclic carbonates from epoxides and CO₂. The activity of these catalytic systems is found to increase upon addition of 2,2,2-trifluoroethanol.

Key words: diethylenetriamine, hexamethylenediamine, iodine, epoxides, CO₂ fixation, 2,2,2-trifluoroethanol.

 

Introduction

CO₂ is one of the large-scale industrial side products that acts as a greenhouse gas, which stimulates the investigation of its conversion to widely used commercial products [1]. In addition to high availability, CO₂ features liquefiability, nonflammability, and lower toxicity than many organic reagents [2]. However, the widespread use of carbon dioxide is limited due to its low dissolving ability and inertness associated with a zero dipole moment and dielectric constant ranging from 1.1 to 1.5, depending on the pressure and temperature [3]. One of the efficient and synthetically convenient approaches is the use of CO₂ as a synthon for the formation of organic cyclic carbonates from epoxides [4–6]. It should be noted that organic carbonates are widely used as fuel additives, polar solvents, including those used in lithium-ion batteries, and monomers for the production of polycarbonates and non-isocyanate polyurethanes [7]. In the mentioned process, CO₂ serves simultaneously as a reactant and reaction medium, and only the epoxide and catalyst are additionally required. Currently, transition metal complexes, ionic liquids, and non-metallic catalysts such as organic ammonium, imidazolium, and phosphonium salts, including those covalently or weakly bound to solid supports, are used as catalysts for this process; nevertheless, almost all of these catalysts can be considered as sources of a halide ion compatible with CO₂ [8]. Recently, it has been reported that simple mixing iodine and amines can afford the catalysts that provide 100% conversion in this reaction [9–13]. In order to increase the efficiency of catalysts, we decided to test diethylenetriamine 1 and hexamethylenediamine 2 (Scheme 1), which are characterized by the high content of iodine-binding amino groups. The latter will make the process more ecologically friendly and mass-efficient. Of special note is the low cost of these industrial amines.

Scheme 1. Addition of СО₂ to epoxides.

Results and discussion

The catalysts generated in situ from diethylenetriamine (0.5 mol %) and iodine (0.5–1.5 mol %, see Table 1) were initially tested in the addition of CO₂ to propylene oxide (3a) for 1 h.

Table 1. Parameters of the addition of CO₂ to oxiranes

Entry	Amine	Oxirane	I2, mol %	Alcohol	P, atm	T, °С	t, h	Conversion (yield), %
1	1	3a	0.5	–	10	110	1	35
2	1	3a	1.0	–	10	110	1	44
3	1	3a	1.5	–	10	110	1	50
4	1	3a	1.5	CF3CH2OH	10	110	1	75
5	1	3a	1.5	CH3CH2OH	10	110	1	56
6	1	3a	1.5	CH3OH	10	110	1	58
7	2	3a	0.5	–	10	110	1	42
8	2	3a	1.0	–	10	110	1	50
9	2	3a	1.0	CF3CH2OH	10	110	1	61
10	1	3a	1.5	–	10	110	2	67
11	1	3a	1.5	–	56	110	2	81
12	1	3a	1.5	–	56	120	2	100 (97)
13	2	3a	1.0	–	56	120	2	87
14	2	3a	1.0	CF3CH2OH	56	120	2	100 (94)
15	1	3b	1.5	–	56	120	2	87
16	1	3b	1.5	–	56	120	3	100 (96)
17	1	3b	1.5	CF3CH2OH	56	120	2	100 (93)
18	1	3c	1.5	–	56	120	2	100 (96)
19	1	3d	1.5	–	56	120	2	100 (95)
20	1	3e	1.5	–	56	120	2	100 (94)
21	1	3f	1.5	–	56	120	2	100 (95)
22	1	3g	1.5	–	56	120	2	100 (97)

It was found that the increased amount of iodine facilitates the process, which is most likely associated with the binding of an equivalent of I₂ by each amino group (Table 1, entries 1–3). Taking into account the cocatalytic effect of fluorinated alcohols on a number of processes [14], in order to optimize the result obtained, 2,2,2-trifluoroethanol was added to the reaction mixture. This afforded a significant increase in the conversion (entries 3 and 4). In this case, 2,2,2-trifluoroethanol is likely to form a hydrogen bond with an oxirane, which facilitates its subsequent opening with CO₂ insertion (Scheme 2).

Scheme 2. Proposed process mechanism.

It should be noted that ethanol and methanol are almost ineffective as additives (entries 5, 6). This can be explained by their lower acidity compared to 2,2,2-trifluoroethanol. The positive effect of the increased amount of iodine and 2,2,2-trifluoroethanol additive were also observed in the case of hexamethylenediamine (entries 7–9).

In order to achieve a quantitative conversion in the reaction of CO₂ with propylene oxide, the additional experiments were carried out at the elevated pressure and temperature for 2 h (entries 10–12). In these experiments, the quantitative conversion was observed and its expected growth with increasing CO₂ pressure and temperature was demonstrated. In the case of the catalyst based on hexamethylenediamine and iodine, the reaction optimization required not only an increase in the temperature and pressure but also the addition of 2,2,2-trifluoroethanol (entries 13, 14).

The effect of an epoxide substituent on the process rate was also evaluated. Thus, in the case of 1,2-epoxybutane, either the longer reaction time or the addition of 2,2,2-trifluoroethanol is required to reach the quantitative conversion (entries 15–17). Epoxides 3c–g bearing electron-withdrawing substituents can be quantitatively converted to the target carbonates in 2 h without the addition of the fluorinated alcohol.

The adducts of amines with iodine were studied using Raman spectroscopy. The Raman spectrum of hexamethylenediamine and iodine (Fig. 1a) shows a narrow intensive line at 176 cm^–1 that corresponds to the νI–I stretching vibrations of the I₅^– anion and a weak line at 110 cm^–1 that relates to the I–I stretching vibrations of the I₃^– anion. The Raman spectrum of a mixture of I₂ and diethylenetriamine (Fig. 1b) shows two intensive lines at 110 and 163 cm^–1 with other distribution of intensities [15, 16]. The lack of a line at ~220 cm^–1 indicates the absence of molecular I₂ in both cases.

Figure 1. Raman spectra of the adducts of 2 with I₂ (a) and 1 with I₂ (b).

The interaction of iodine with amines was also studied by IR spectroscopy (Fig. 2). Thus, the IR spectrum of starting amine 1 demonstrates three bands at 3194, 3278, and 3355 cm^–1 which are associated with the stretching vibrations of NH and NH₂ groups. The band at 1601 cm^–1 refers to the bending vibration δNH. Slightly broadened shapes of these bands are typical for weak NH…N hydrogen bonds formed by amines in the liquid state.

Figure 2. IR spectra of amine 1 (a) and its adduct with I₂ (b)_.

Figure 3. IR spectra of amine 2 (a) and its adduct with I₂ (b).

Experimental

General remarks

The ¹H (400.13 MHz) and ¹³C (101 MHz) NMR spectra were registered on a Bruker Avance 400 spectrometer in CDCl₃. The Raman spectra were recorded in the range of 100–4000 cm^–1 on a JobinYvon LabRAM 300 spectrometer (He-Ne laser 632.8 nm, 1 mW). The IR spectra were registered in the range of 400–4000 cm^–1 on Bruker Vector 70v FTIR-spectrometer. Amines 1 and 2, 2-methyloxirane (3a), 2-ethyloxirane (3b), 2-fluoromethyloxirane (3с), 2-chloromethyloxirane (3d), 2-bromomethyloxirane (3e), and 2-(pehnoxymethyl)oxirane (3f) were purchased from commercial sources (Sigma-Aldrich and Acros).

Syntheses

1-(Oxiran-2-ylmethyl)-1-pyrrole, 3g. A solution of pyrrole (3.000 g, 0.045 mol) in toluene (5 mL) was added to a suspension of NaH (60% dispersion in mineral oi; 1.780 g, 0.045 mol) in toluene (20 mL) under an argon atmosphere. The resulting mixture was stirred at room temperature and heated to reflux. After cooling to room temperature, epichlorohydrin (4.137 g, 0.045 mol) was added. The reaction mixture was stirred at room temperature for 1 h and then refluxed for 1.5 h. After addition of water (20 mL), the organic layer was separated, washed with water (10 mL), dried over anhydrous Na₂SO₄, and evaporated to dryness. The residue obtained was distilled under vacuum to give 2.000 g of the target product as a colorless viscous oil. Yield: 36%. Bp: 100 °С (1 Torr). ¹H NMR (CDCl₃): δ 2.49–2.50 (m, 1H), 2.85 (t, J = 4 Hz, 1H), 3.25–3.29 (m, 1H), 3.99 (dd, J = 8 Hz, 16 Hz, 1H), 4.20 (dd, J = 4 Hz, 12 Hz, 1H), 6.22 (t, J = 4 Hz, 2H), 6.75 (t, J = 4 Hz, 2H) ppm. ¹³C NMR (CDCl₃): δ 42.62 (CH₂), 48.66 (CH₂), 48.89 (CH), 106.25 (CH), 118.58 (CH) ppm. Anal. Calcd for C₇H₉NO: C, 68.27; H, 7.37; N, 11.37. Found: C, 68.34; H, 7.45; N, 11.31%.

General procedure for the synthesis of carbonates 4a–g from epoxides. A 10 mL autoclave was charged with the corresponding amine (0.03 mmol), iodine (0.03, 0.06, or 0.09 mmol). Then the corresponding epoxide (6 mmol) and, in some cases, alcohol (1.2 mmol) were added. The autoclave was filled with CO₂ and heated to the required temperature in a thermostat. After the reaction completion, the autoclave was cooled to 5 °С, CO₂ was blown off, and CDCl₃ (2 mL) was added to the resulting mixture. After filtration through a thin layer of silica gel to remove the residual catalyst, the filtrate was analyzed by NMR spectroscopy. The spectral characteristics of the resulting carbonates were identical to the reported ones [17–20]. When 2,2,2-trifluoroethanol was used, the alcohol was additionally evaporated under vacuum after determining the conversion.

4-((1H-Pyrrol-1-yl)methyl)-1,3-dioxolan-2-one, 4g. Yellow viscous oil. ¹H NMR (CDCl₃): δ 4.09–4.13 (m, 1H), 4.15 (dd, J = 8 Hz, 16 Hz, 1H), 4.27 (dd, J = 4 Hz, 16 Hz, 1H), 4.49 (t, J = 8 Hz, 1H), 4.91–4.97 (m, 1H), 6.23 (t, J = 1 Hz, 2H), 6.71 (t, J = 1 Hz, 2H) ppm. ¹³C NMR (CDCl₃): δ 50.65 (CH₂), 66.34 (CH₂), 75.69 (CH), 109.67 (CH), 121.45 (CH), 154.33 (CO) ppm. Anal. Calcd for C₈H₉NO₃: C, 57.48; H, 5.43; N, 8.38. Found: C, 57.56; H, 5.49; N, 8.31%.

Conclusions

Hence, we showed that mixing di- and triamines with iodine can afford cheap and efficient catalysts for the formation of cyclic carbonates from epoxides and СО₂, which demonstrated higher performance than the previously reported analogs [9–13]. The activity of these catalytic systems can be enhanced upon addition of 2,2,2-trifluoroethanol. The investigations by Raman spectroscopy revealed the presence of polyiodide ions (I₃^–, I₅^–), which can potentially participate in the catalytic cycle analogously to the I^– ion. The analysis of the spectral data confirmed the interaction of iodine with the amines upon formation of the catalytic systems.

Acknowledgements

This work was supported by the Ministry of Science and Higher Education of the Russian Federation (agreement no. 075-00697-22-00).

References

1. C. Le Quere, R. B. Jackson, M. W. Jones, A. J. P. Smith, S. Abernethy, R. M. Andrew, A. J. De-Gol, D. R. Willis, Y. Shan, J. G. Canadell, P. Friedlingstein, F. Creutzig, G. P. Peters, Nat. Clim. Change, 2020, 10, 647. DOI: 10.1038/s41558-020-0797-x
2. E. J. Beckman, J. Supercrit. Fluids, 2004, 28, 121–191. DOI: 10.1016/S0896-8446(03)00029-9
3. A. van Itterbeek, K. de Clippeleir, Physica, 1947, 13, 459–464. DOI: 10.1016/0031-8914(47)90033-5
4. C. Calabrese, F. Giacalone, C. Aprile, Catalysts, 2019, 9, 325. DOI: 10.3390/catal9040325
5. A. J. Kamphuis, F. Picchioni, P. P. Pescarmona, Green Chem., 2019, 21, 406–448. DOI: 10.1039/C8GC03086C
6. L. Guo, K. J. Lamb, M. North, Green Chem., 2021, 23, 77–118. DOI: 10.1039/D0GC03465G
7. Y. Fan, M. Tiffner, J. Schörgenhumer, R. Robiette, M. Waser, S. R. Kass, J. Org. Chem., 2018, 83, 9991–10000. DOI: 10.1021/acs.joc.8b01374
8. T. Weidlich, B. Kamenicka, Catalysts, 2022, 12, 298. DOI: 10.3390/catal12030298
9. B. Chowdhury, A. A. Zvinchuk, R. R. Aysin, E. A. Khakina, P. V. Cherkasova, S. E. Lyubimov, Catal. Surv. Asia, 2021, 25, 419–423. DOI: 10.1007/s10563-021-09341-9
10. O. Coulembier, S. Moins, V. Lemaur, R. Lazzaroni, P. Dubois, J. CO₂ Util., 2015, 10, 7–11. DOI: 10.1016/j.jcou.2015.02.002
11. S. E. Lyubimov, P. V. Cherkasova, R. R. Aysin, Russ. Chem. Bull., 2022, 71, 577–579. DOI: 10.1007/s11172-022-3451-0
12. S. E. Lyubimov, P. V. Cherkasova, R. R. Aysin, B. Chowdhury, Russ. Chem. Bull., 2022, 71, 408–411. DOI: 10.1007/s11172-022-3427-0
13. S. E. Lyubimov, P. V. Cherkasova, R. R. Aysin, INEOS OPEN, 2022, 5, 7–9. DOI: 10.32931/io2202a
14. I. A. Shuklov, N. V. Dubrovina, A. Börner, Synthesis, 2007, 19, 2925–2943. DOI: 10.1055/s-2007-983902
15. J. D. Comins, T. P. Nguyen, M.-A. Pariselle, S. Lefrant, A. M. T. Allen, Radiat. Eff. Defects Solids, 1995, 134, 437–441. DOI: 10.1080/10420159508227264
16. E. M. Nour, L. H. Chen, J. Laane, J. Phys. Chem., 1986, 90, 2841–2846. DOI: 10.1021/j100404a014
17. H. Zhou, G.-X. Wang, W.-Z. Zhang, X.-B. Lu, ACS Catal., 2015, 5, 6773–6779. DOI: 10.1021/acscatal.5b01409
18. P. A. Carvalho, J. W. Comerford, K. J. Lamb, M. North, P. S. Reiss, Adv. Synth. Catal., 2019, 361, 345–354. DOI: 10.1002/adsc.201801229
19. H. Chang, Q. Li, X. Cui, H. Wang, C. Qiao, Z. Bu, T. Lin, Mol. Catal., 2018, 449, 25–30. DOI: 10.1016/j.mcat.2018.02.007
20. H. Chen, Z. Zhang, T. Hu, X. Zhang, Inorg. Chem., 2021, 60, 16429–16438. DOI: 10.1021/acs.inorgchem.1c02262