Process for production of ketones from secondary alcohols

Abstract

The present invention relates to the process for production of ketones from secondary alcohols by the use of a hybrid material, formed by the dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups, as efficient and selective catalyst of peroxidative oxidation, microwave-assisted and without solvent addition.

Claims

1. A process for production of ketones from secondary alcohols, assisted by microwave radiation comprising the mixture of an oxidising agent with a hybrid, material dichlorohydrotris (pyrazol-1-yl) methane iron (II) covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups as catalyst, at a temperature of 80 C.

2. The process according to claim 1, wherein the oxidising agent is a 70% aqueous solution of tert-butyl hydroperoxide.

3. The process according to claim 1, wherein the dichlorohydrotris (pyrazol-1-yl) methane iron (II) complex contains an iron content of 2% (w/w).

4. The process according to claim 1, wherein the secondary alcohols are selected from: cyclohexanol, 1-phenylethanol, o, m- or p-cresols, linear alcohols 2-hexanol, 3-hexanol, 1-butanol or 2-butanol, and diols.

5. The process according to claim 1, wherein the reaction time is one hour.

6. The process according to claim 1, which is free from solvent addition.

7. The process according to claim 1, wherein the catalyst dichlorohydrotris (pyrazol-1-yl) methane iron (II) covalently bound to multiple wall carbon nanotubes functionalized with superficial carboxylate groups is reusable in at least six subsequent catalytic cycles.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The invention relates to a process for production of ketones from secondary alcohols by the use and mixture of a hybrid material, formed by the dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups, with iron content between 1 and 5% (w/w), as efficient and recyclable catalyst of partial oxidation of secondary alcohols, with tert-butyl hydroperoxide, as oxidising agent, at a temperature between 60 and 100 C. and microwave irradiation for one hour, into respective ketones, the process being carried out in environmentally tolerable conditions (no solvents and moderate temperatures) and with high yield and selectivity.

(2) It was now shown that the use of the hybrid material formed by the dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups in the oxidation of 1-phenylethanol or cyclohexanol is a high efficacy and selectivity system on very short reaction times, and that it can easily be reused without activity loss. Quantitative conversion of the alcohols into respective ketones for at least 6 consecutive cycles was achieved, with frequencies of catalytic cycles, i.e., turnover frequencies (TOF), expressed in moles of product per mole of catalyst per hour, up to 1.810.sup.3 h.sup.1.

(3) The advantages associated with this invention are due to the use of the above-described hybrid material in the process of microwave-assisted, synthesis of ketones that allows to (i) create an almost quantitative conversion of the secondary alcohol into ketone; (ii) reuse said hybrid material in a significant number of consecutive catalytic cycles without activity loss; (iii) eliminate the use of organic solvents; and (iv) reduce significantly the reaction time to 1 h.

(4) Thus, the process for production now developed, due to the use of the above-mentioned hybrid material, looks very promising in the economic point of view and with great potential to be industrially applied, as it allows to overcome the disadvantages of the systems known so far, such as the need for i) high amounts of catalyst [16,17], ii) long reaction times [18-20], iii) presence of additives or co-catalysts [2,16-20], iv) high amounts of toxic oxidants [13-15,21,22] v) solvents [19-24]; or the formation of by-products. Moreover, the known catalysts are frequently difficult to prepare, do not show good activity in the oxidation of aliphatic alcohols and are not possible to reuse [2,4,18-20,25,26].

(5) Additionally, the process for production disclosed in the present invention, due to the use of the above-mentioned hybrid material, is also active in the oxidation of o-, m- or p-cresols, linear alcohols, such as 1-butanol, 2-butanol, 2-hexanol, and diols (e.g., 1,3-butanediol), allowing also the reuse of said hybrid material in a significant number of consecutive catalytic cycles without activity loss.

(6) In a preferred embodiment of the present invention, the hybrid material has an iron content of 2% (w/w).

(7) In another preferred embodiment of the present invention, the temperature used is 80 C.

(8) Solvents and reagents were commercially acquired (Aldrich) and used as received.

(9) The dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex was prepared according to the process described in the literature [27] and the multi-walled carbon nanotubes were functionalized by treatment with 5 M nitric acid for 3 h followed by 20 mM sodium hydroxide for 1 h, according to methods known in the art [29-31]. The hybrid material of the present invention was obtained by heterogenization of the dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex in functionalized multi-walled carbon nanotubes, carried out according to a known protocol [32].

(10) The products of the catalytic assays were analysed by gas chromatography (GC) using a FISONS Instruments GC 8000 series gas chromatograph with a DB-624 capillary column (J&W) (FID detector) and Jasco-Borwin v.1.50 software. The injection temperature was 240 C. The initial temperature was kept at 100 C. for 1 minute, then increased at 10 C./min up to 180 C. and kept at this temperature for 1 minute. Helium was used as carrier gas. The GC-MS analyses were carried out using a Perkin Elmer Clarus 600 C instrument (helium as carrier gas). The ionization voltage was 70 eV. The gas chromatography was carried out in the temperature programming mode, using a SGE BPX5 column (30 m0.25 mm0.25 m). The reaction products were identified by comparison of their retention times with known reference compounds, and by comparison of their mass spectra with the fragment standards obtained from the NIST spectral library stored in the mass spectrometer computer program.

(11) The hybrid material formed by the dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups, with an iron content of 2% (w/w) is remarkably effective and selective in the microwave-assisted oxidation of secondary alcohols into respective ketones with tert-butyl hydroperoxide, and without solvent addition.

EXAMPLES

(12) The description of the catalytic process of oxidation of the secondary alcohols cyclohexanol, 3-hexanol and 1-phenylethanol is described with more detail by the following examples, for illustrative purposes only, and non-limiting of the scope of the present invention.

Example 1

(13) Process of Microwave-Assisted Peroxidative Oxidation of Cyclohexanol to Cyclohexanone Using as Catalyst the Hybrid Material Formed by the dichlorohydrotris(pyrazol-1-yl)methane Iron (II) Complex Covalently Bound to Multi-Walled Carbon Nanotubes Functionalized with Superficial Carboxylate Groups, with an Iron Content of 2% (w/w)

(14) In a pyrex cylindrical tube of the Monowave 300 Anton Paar microwave reactor the substrate (cyclohexanol, 5 mmol), 70% aqueous solution of tert-butyl hydroperoxide (10 mmol) and 5 mol of catalyst (based on the iron complex; 0.1% mol vs. substrate) were placed. The system was closed, stirred and microwave irradiated for 60 minutes, up to 80 C., at 25 W of power. After the reaction, the reaction mixture was left to cool down to room temperature.

(15) Extraction and analysis by gas chromatography: The resulting reaction mixture was treated with 5 mL of acetonitrile and 300 L of internal standard (ex., benzaldehyde). It was stirred for 10 minutes and, after aging, a sample (4 L) from the organic phase was taken and analysed by GC (or CC-MS) using the internal standard method.

(16) TABLE-US-00001 TABLE 1 Microwave-assisted oxidation of cyclohexanol catalysed by hybrid material made of dichlorohydrotris(pyrazol-1-yl)methane iron (II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups, with an iron content of 2% (w/w)..sup.a Catalytic Selectivity.sup.d/ cycle Yield.sup.b/% TOF.sup.c/h.sup.1 % 1 98.3 984 99 2 97.8 978 99 3 97.7 977 99 4 97.7 977 99 5 97.6 976 98 6 94.1 941 96 7 88.4 884 97 .sup.aReaction conditions: 5 mmol of substrate, 5 mol of catalyst (based on the iron complex; 0.1 mol vs. substrate), 10 mmol of tert-butyl hydroperoxide (2 eq., 70% in H.sub.2O), 80 C., 60 minutes with microwave irradiation (25 W). .sup.bBased on gas chromatography analyses, moles of ketone per 100 moles of alkane, 100% of selectivity in all cases. .sup.cFrequency of catalytic cycles = number of moles of ketone per of catalyst per hour. .sup.dMoles of ketone per mole of converted alcohol.

Example 2

(17) Process of Microwave-Assisted Peroxidative Oxidation of 1-Phenylethanol to Acetophenone Using as Catalyst the Hybrid Material Formed by the dichlorohydrotris(pyrazol-1-yl)methane Iron (II) Complex Covalently Bound to Multi-Walled Carbon Nanotubes Functionalized with Superficial Carboxylate Groups, with an Iron Content of 2% (w/w)

(18) In a pyrex cylindrical tube of the Monowave 300 Anton Paar microwave reactor the substrate (1-phenylethanol, 5 mmol), 70% aqueous solution of tert-butyl hydroperoxide (10 mmol) and 5 mol of catalyst (based on the iron complex; 0.1% mol vs. substrate) were placed. The system was closed, stirred and microwave irradiated for 60 minutes, up to 80 C., at 25 W of power. After the reaction, the reaction mixture was left to cool down to room temperature.

(19) Extraction and analysis by gas chromatography: The resulting reaction mixture was treated with 5 mL of acetonitrile and 300 L of internal standard (ex., benzaldehyde). It was stirred for 10 minutes and, after aging, a sample (4 L) from the organic phase was taken and analysed by GC (or GC-MS) using the internal standard method.

(20) TABLE-US-00002 TABLE 2 Microwave-assisted oxidation of 1-phenylethanol catalysed by hybrid material made of dichlorohydrotris(pyrazol-1-yl)methane iron(II) complex covalently bound to multi-walled carbon nanotubes functionalized with superficial carboxylate groups, with an iron content of 2% (w/w)..sup.a Catalytic Selectivity.sup.d/ cycle Yield.sup.b/% TOF.sup.c/h.sup.1 % 1 94.2 942 98 2 93.5 935 98 3 93.3 933 98 4 93.3 933 98 5 92.8 928 97 6 92.1 921 97 .sup.aReaction conditions: 5 mmol of substrate, 5 mol of catalyst: (based on the iron complex; 0.1% mol vs. substrate), 10 mmol of tert-butyl hydroperoxide (2 eq., 70% in H.sub.2O), 80 C., 60 minutes with microwave irradiation (25 W) . .sup.bBased on gas chromatography analyses, moles of ketone per 100 moles of alkane, 100% of selectivity in all cases. .sup.cFrequency of catalytic cycles = number of moles of ketone, per moles of catalyst per hour. .sup.dMoles of ketone per mole of converted alcohol.

Example 3

(21) Process of Microwave-Assisted Peroxidative Oxidation of 3-Hexanol to 3-Hexanone Using as Catalyst the Hybrid Material Formed by the dichlorohydrotris(pyrazol-1-yl)methane Iron (II) Complex Covalently Bound to Multi-Walled Carbon Nanotubes Functionalized with Superficial Carboxylate Groups, with an Iron Content of 2% (w/w)

(22) In a pyrex cylindrical tube of the Monowave 300 Anton Paar microwave reactor the substrate (3-hexanol, 5 mmol), 70% aqueous solution of tert-butyl hydroperoxide (10 mmol) and 5 mol of catalyst (based on the iron complex; 0.1% mol vs. substrate) were placed. The system was closed, stirred and microwave irradiated for 60 minutes, up to 80 C., at 25 W of power. After the reaction, the reaction mixture was left to cool down to room temperature.

(23) Extraction and analysis by gas chromatography: The resulting reaction mixture was treated with 5 mL of acetonitrile and 300 L of internal standard (ex., benzaldehyde). It was stirred for 10 minutes and, after aging, a sample (4 L) from the organic phase was taken and analysed by GC (or GC-MS) using the internal standard method.

(24) 3-Hexanone was obtained as the sole product (100% of selectivity) with a 9.8% yield and TOF of 98 h.sup.1. The excellent selectivity obtained with the present process for partial oxidation of the substrate 3-hexanol is worthy of note.

REFERENCES

(25) [1] A. Pombeiro (Ed.), Advances in Organometallic Chemistry and Catalysis, The Silver/Gold Jubilee ICOMC Celebratory Book, J. Wiley & Sons, 2014. [2] M. N. Kopylovich, A. P. C. Ribeiro, E. C. B. A. Alegria, N. M. R. Martins, L. M. D. R. S. Martins, A. J. L. Pombeiro, Adv. Organomet. Chem., 2015, 63, Ch. 3, 91-174. [3] L. Martins, A. Pombeiro, Coord. Chem. Rev., 2014, 265, 74. [4] M. Sutradhar, L. M. D. R. S. Martins, M. F. C. Guedes da Silva, A. J. L. Pombeiro, Coord. Chem. Rev., 2015, 301-302, 200-239. [5] K. Weissermel, H.-J. Arpe, Industrial Organic Chemistry, 2.sup.nd ed., VCH Press, Weinheim, 1993. [6] R. Whyman, Applied Organometallic Chemistry and Catalysis, Oxford University Press, Oxford, 2001. [7] J.-E. B{hacek over (a)}ckvall, Modern Oxidation Methods, Wiley-VCH, Weinheim, 2004. [8] R. A. Sheldon, I. Arends, U. Hanefeld, Green Chemistry and Catalysis, Wiley-VCH, Weinheim, 2007. [9] G. P. Chiusoli, P. M. Maitlis (Eds.), Metal-catalysis in Industrial Organic Processes, Royal Society of Chemistry, Cambridge, 2006. [10] P. T. Anastas, J. C. Warner, Green Chemistry: Theory and Practice, Oxford University Press, Oxford, U.K., 1998. [11] P. T. Anastas, M. Kirchhoff, Acc. Chem. Res., 2002, 35, 686. [12] R. A. Smiley, H. L. Jackson, Chemistry and the Chemical Industry, CRC Press, 2002. [13] Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 6.sup.th edn., 2002. [14] R. A. Smiley, H. L. Jackson, Chemistry and the Chemical Industry, CRC Press, 2002. [15] Process Chemistry in the Pharmaceutical Industry. Vol. 2, ed. K. Gadamasetti, T. Braish, CRC Press, 2008. [16] I. E. Mark, P. R. Giles, M. Tsukazaki, S. M. Brown, C. J. Urch, Science 1996, 274, 2044. [17] D. Bogda, M. Lukasiewicz, Synlett, 2000, 143. [18] G. Ferguson, A. N. Ajjou, Tetrahedron Lett., 2003, 44, 9139. [19] G. Rothenberg, L. Feldberg, H. Wiener, Y. Sasson, J. Chem. Soc., Perkin Trans., 1998, 2, 2429. [20] R. Chakrabarty, P. Sarmah, B. Saha, S. Chakravorty, B. K. Das, Inorg. Chem. 2009, 48, 6371. [21] J. Singh, M. Shana, M. Chibber, J. Kaur, G. L. Kad, Synth. Commun., 2000, 30, 3941. [22] D. Pandey, D. S. Kotari, Oxyd. Commun., 2009, 32, 371. [23] L. Palombi, F. Bonadies, A. Scetti, Tetrahedron, 1997, 53, 15867. [24] C. Gonzlez-Arellano, J. M. Campelo, D. J. Macquarrie, J. M. Marinas, ChemSusChem., 2008, 1, 746. [25] A. Corma, H. Garcia, Chem. Soc. Rev., 2008, 37, 2096. [26] L. Tonucci, M. Nicastro, N. d'Alessandro, M. Bressan, P. D'Ambrosio, A. Morvillo, Green Chem., 2009, 11, 816. [27] T. F. S. Silva, E. C. B. A. Alegria, L. M. D. R. S. Martins, A. J. L. Pombeiro, Adv., Synth. Cat. 2008, 350, 706. [28] J. L. Figueiredo, M. F. R. Pereira, M. M. A. Freitas, J. J. M. rfo, Carbon, 1999, 37, 1379. [29] N. Mahata, M. F. R. Pereira, F. Surez-Garca, A. Martnez-Alonso, J. M. D. Tascn, J. L. Figueiredo, J. Colloid Interface Sci. 2008, 324, 150. [30] I. Gerber, M. Oubenali, R. Bacsa, J. Durand, A. Gonalves, M. F. R. Pereira, F. Jolibois, L. Perrin, R. Poteau, P. Serp, Chem. Eur. J., 2011, 17, 11467. [31] F. Maia, N. Mahata, B. Jarrais, A. R. Silva, M. F. R. Pereira, C. Freire, J. L. Figueiredo, J. Mol. Catal. A, 2009, 305, 135. [32] L. M. D. R. S. Martins, M. P. Almeida, S. A. C. Carabineiro, J. L. Figueiredo, A. J. L. Pombeiro, ChemCatChem, 2013, 5, 3847.