Industrial-Quality Graphene Oxide Switched Highly Efficient Metal

Jan 15, 2017 - Department of Fine Arts, New Asia College, The Chinese University of Hong Kong, ... ABSTRACT: Metal- and solvent-free industrial-qualit...
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Industrial-Quality Graphene Oxide Switched Highly Efficient Metaland Solvent-Free Synthesis of β‑Ketoenamines under Feasible Conditions Dian Deng,† Lang Xiao,§ Ill-Min Chung,*,‡ Ick Soo Kim,*,† and Mayakrishnan Gopiraman*,‡ †

Nano Fusion Technology Research Group, Division of Frontier Fibers, Institute for Fiber Engineering (IFES), Interdisciplinary Cluster for Cutting Edge Research (ICCER), Shinshu University, Tokida 3-15-1, Ueda, Nagano 386-8567, Japan ‡ Department of Applied Bioscience, College of Life & Environment Science, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, South Korea § Department of Fine Arts, New Asia College, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China S Supporting Information *

ABSTRACT: Metal- and solvent-free industrial-quality graphene oxide (IQGO)-based highly efficient carbocatalytic system has been developed for the synthesis of β-ketoenamines. Initially, physicochemical properties of IQGO are briefly discussed by means of various microscopic and spectroscopic techniques. The present system accessed a wide range of substrates to yield β-ketoenamines in an excellent yield (86−100%) with 100% selectivity. Catalytic activity of IQGO is compared with other carbon materials such as carbon nanotubes, carbon nanofibers, and graphene nanoplatelets. Cost effective recovery, high level reusability, chemoselective nature, possible scale reaction, and sustainability of IQGO are demonstrated. Based upon experimental results and earlier reports, possible reaction mechanism has been proposed for the synthesis of β-ketoenamines. KEYWORDS: Graphene oxide, Carbocatalysis, β-Ketoenamines, Reusable, Sustainable

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INTRODUCTION Currently, over 90% of the potential high-value products (fine chemicals and pharmaceuticals) in chemical industries are produced from catalytic processes.1 Transition metal-based catalysts (both heterogeneous and homogeneous), mainly Ru, Cu, Ni, Pt, Rh, and Pd, are commonly used in the catalytic process.2,3 In addition to high cost, disposal of these metal catalysts often causes environmental problems.4 The U.S. Environmental Protection Agency (EPA) indicates that the disposal of metal catalysts is not only expensive but also dangerous.5 In fact, some of the catalytic materials are unusually reactive when they mixed with other wastes which pose unwanted environmental issues. Several points (in addition to the environmental pollution and high cost) should be carefully considered when we use metal-based catalysts: mainly, (1) preparation method, (2) morphology, (3) surface area, (4) pore properties, (5) metal−support interaction, and (6) chemical state of the catalysts. Moreover, after use, the metal recovery from the catalysts is quite complicated and requires high cost techniques.6 To overcome these shortcomings, researchers have widely focused on the development of metal-free green synthesis of fine chemicals and pharmaceuticals.7 Owing to the outstanding intrinsic physicochemical properties such as unique structure, huge surface area, good pore © 2017 American Chemical Society

interconnectivity and high stability, carbon materials (CMs) such as activated carbons (ACs),8 fullerenes,9 single- and multiwalled carbon nanotubes (SWCNTs and MWCNTs),10,11 and graphene oxide (GO)12 have been demonstrated as efficient carbocatalysts. Among them, GO is highly preferred due to low cost, unique 2D structure, rich chemical functionality (solid acid, solid base, redox and defect sites) and stability.13 To date, several metal-based catalytic systems have been replaced by GO-based carbocatalytic systems. For instant, Lv et al.14 demonstrated GO as a suitable metal-free carbocatalyst for the oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran. They concluded that the GO could be an alternate choice for the metal catalysts such as Co/Ce/Ru, Ru, Cu, Cu/V, Mn, Mo/V, and V. Huang and co-workers15 utilized GO as a carbocatalyst for aerobic oxidative coupling of amines to imines. Recently, a considerable number of review articles dealing the importance and development of the carbocatalysts have been published.16−23 Formation of β-enamino ketones and esters via enamination of β-dicarbonyl is one of the important and extensively used Received: November 15, 2016 Revised: December 25, 2016 Published: January 15, 2017 1253

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ACS Sustainable Chemistry & Engineering transformations in organic synthesis.24 The β-enamino ketones and esters have been used as basic units for the formation of biologically active motifs such as peptides, β-amino esters and alcohols, γ-amino alcohols and alkaloids.25 The β-ketoenamines are found to be highly efficient antitumor, antibacterial, and anti-inflammatory agents.26 Metal catalysts mediated direct condensation of β-dicarbonyl compounds with amines is the prime route to obtain these active compounds. Babu et al.27 prepared Cu/AlO(OH) and utilized as a catalyst for the formation of β-enamino ketones/esters. Later, Sun and coworkers28 developed magnetically recoverable Ag-medicated catalyst for the synthesis of β-enaminones. Similarly, there are several metal catalysts including NaAuCl4,29 Ag nanoparticles,30 Mg(ClO4)2,31 CoCl2·6H2O,32 Zn(OAc)2·2H2O,33 CeCl3· 7H2O,34 Zn(ClO4)2·6H2O,35 ZrCl4,36 SnCl4,37 Cu nanoparticles,38 Cu(II) nitrate trihydrate,39 ZrOCl2·8H2O,40 and InBr341 reported to date. Unfortunately, there is no GO-based carbocatalytic system demonstrated for the synthesis of βenaminones to date. We assumed that the GO could be an alternate choice to the existing metal catalysts for the βenaminones formation. Herein, we report low-cost industrial quality graphene oxide (IQGO) as an efficient carbocatalyst for the metal- and solvent-free synthesis of β-enamino ketones and esters. The catalytic activity of IQGO has been compared with other CMs including SWCNTs, ACs, GNPs, and MWCNTs.

as the sum of a Gaussian function (Figure 1c). The high IG/ID value (0.88) confirmed the presence of defect sites on IQGO. The XRD pattern of IQGO demonstrated a weak diffraction peak at 26.5° corresponds to well-defined (002) crystal plane of graphite (Figure 1d). Figure 2 shows XPS of IQGO. The C 1s

Figure 2. Deconvoluted XPS (a) C 1s and (b) O 1s peaks of IQGO.

and O 1s XPS peaks were noticed at ∼284.5 and ∼532.5 eV, respectively. To study the oxygen functionalities on IQGO, curve fitting was performed on C 1s and O 1s peaks using a Gaussian−Lorentzian peak shape. Both the deconvoluted C 1s and O 1s peaks resulted in five obvious peaks, and the peak values verified the presence of CC/CH, CO, −COOH, COH, −COC−, and H2O groups.42 In addition, p → p* shakeup satellite at ∼294 eV was also observed. Generally, GO is hydrophobic in nature and the presence of oxygen functional groups would make the GO hydrophilic, as consequences, better dispersion of IQGO could be achieved in reaction medium. As expected, the IQGO demonstrated a very high BET surface area of 767 m2/g with average BJH pore volume and pore size of 1.3 cm3/g and 6.8 nm, respectively (Figure 3). In the present case, the important futures of IQGO

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RESULTS AND DISCUSSION TEM image, EDS, Raman and XRD pattern of IQGO are provided in Figure 1. The TEM image showed that the IQGO

Figure 3. (a) Nitrogen adsorption−desorption isotherms and (b) pore size distribution of IQGO.

Figure 1. (a) TEM image, (b) EDS, (c) Raman spectrum, and (d) XRD pattern of IQGO.

are the smaller size and the presence of oxygen functional groups. According to Tang et al.,12 the catalytic activity of the carbon materials is highly dependent on the carbon-bond structures of carbon materials. Moreover, because they are smaller in size, their giant π-conjugated structures and presence of oxygen groups on carbon materials, and tunable electronic states are all can act as active sites in catalytic reactions. Initially, the reaction conditions were optimized using acetylacetonate (1a) and aniline (2a) as modal substrates (Table 1). In the absence of IQGO, the reaction achieved a very low 49% of the desired product (Z)-4-(phenylamino)pent3-en-2-one (3a) (Table 1, entry 1). To find out the most

is continuous, transparent and pure without any impurities (Figure 1a). In addition, wrinkles and bends on IQGO at several places could be also noticed. The mean thickness of IQGO was measured to be 0.8−2.0 nm. The wt % of C and O in IQGO was determined to be 63 and 37, respectively (Figure 1b). The Raman spectra in Figure 1c confirmed two characteristic Raman features for IQGO: the well-defined Dband at ∼1353 cm−1 and G-band at ∼1557 cm−1. The D-band corresponds to disordered graphite whereas the G-band reflects the ordered state graphite. To calculate the IG/ID ratio, baseline correction was performed and, D band and G band were fitted 1254

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understand the importance of oxygen functionalities on IQGO (Table 1, entries 17−20). For this purpose, the IQGO was calcinated under inert atmosphere at 500 °C for 1 h to remove most of the oxygen functional groups (CO, −COOH, and −COC−) and the resultant solid (IQGO-500 °C) was used as a carbocatalyst (Table 1, entry 17). However, the IQGO-500 °C gave a poor yield of 38%. Moreover, an external O2 supply also did not work well to improve the 3a yield (Table 1, entry 18). Interestingly, under various atmospheres (O2, air and N2), the IQGO gave similar yields (Table 1, entries 19 and 20). The scope of the present IQGO system was extended under the optimized reaction conditions. Results presented in Table 2 confirmed that a wide range of aromatic, aliphatic, and cyclic amines can be effectively condensed with various symmetric and unsymmetric β-diketones or β-ketoesters. The present catalytic system obtained a better 96% yield of 3a (100% selectivity) compared to 90% of 3a afford by expensive Ag NPs and Ag/HMMS systems.28,30 The substituent present (electron withdrawing and electron donating) in the β-diketones and the aromatic rings of the amines did not significantly affect the yield of the desired products. In the presence of 10 mg of IQGO, the acetylacetonate (1a) effectively reacted with various substituted aromatic amines including p-toluidine (2b), 4-methoxyaniline (2c), 4-fluoroaniline (2d), and 4-chloroaniline (2e) to obtain the corresponding β-ketoenamines, (Z)-4-(p-tolylamino)pent3-en-2-one (3b, 96%), (Z)-4-((4-methoxy-phenyl)amino)pent3-en-2-one (3c, 96%), (Z)-4-((4-fluorophenyl)amino)pent-3en-2-one (3d, 95%), and (Z)-4-((4-chlorophenyl)amino)pent3-en-2-one (3e, 93%), respectively (Table 2, entries 2−6). Alike, the aliphatic and cyclic amines, cyclohexanamine (2g), and butan-1-amine (2h), effectively condense with acetylacetonate (1a) to give respectively (Z)-4-(cyclohexylamino)pent-3en-2-one (3g, 100%) and (Z)-4-(butylamino)pent-3-en-2-one (3h, 99%) in shorter reaction time (Table 2, entries 7 and 8). The aliphatic amines have higher nucleophilicity when compared to aromatic amines, which is the obvious reason for the faster reactivity of the aliphatic amines than the aromatic amines (Table 2). Unlike other catalytic systems,27,28 the present IQGO-system worked well for the sterically hindered amine also in a shorter reaction time (Table 2, entries 6 and 22). A good 86% yield of (Z)-4-((2-chloro-phenyl)amino)pent-3-en-2-one (3f) was afforded from the reaction between 2-chloroaniline (2f) and 1a (Table 2, entry 6). Similarly, 2f condensed with 1d in the presence of IQGO to give an excellent 99% yield of (Z)-4-((2chlorophenyl)amino)-1,1,1-trifluoropent-3-en-2-one (3v) (Table 2, entry 22). Further, β-ketoesters, methyl 3oxobutanoate (1b), and ethyl 3-oxobutanoate (1c) were also allowed to react with 2a, 2b, 2g, and 2h (Table 2, entries 9− 16). The reaction gave the corresponding β-ketoenamines (3i− 3p) in an excellent yield (94−100%) with 100% selectivity. Most of the metal-based catalytic systems require longer reaction time when processing 1,1,1-trifluoropentane-2,4-dione (1d), 4-chloroaniline (2e), 2-chloroaniline (2f), and butan-1amine (2h) as substrates.27 Interestingly, the present study was highly effective when 1d reacts with 2e, 2f, and 2h to form corresponding β-ketoenamines (Table 2, entries 21, 22, and 24). The system gave (Z)-4-((4-chlorophenyl)amino)-1,1,1trifluoropent-3-en-2-one (3u), (Z)-4-((2-chlorophenyl)amino)1,1,1-trifluoropent-3-en-2-one (3v), and (Z)-4-(butylamino)1,1,1-trifluoropent-3-en-2-one (3x) in excellent yield of 100, 99, and 89%, respectively. Similarly, 1d was condensed with 2a, 2b,

Table 1. Optimization of Reaction Conditions for the Synthesis of 3aa

entry

catalyst

amount of catalyst (mg)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18c 19c 20d

CNFs SWCNTs IQGO MWCNTs GNPs IQGO IQGO IQGO IQGO IQGO IQGO IQGO IQGO IQGO IQGO IQGO-500 °C IQGO-500 °C IQGO IQGO

10 10 10 10 10 5 15 10 10 10 10 10 10 10 10 10 10 10 10

temperature (°C)

time (h)

GC yield (%)b

60 60 60 60 60 60 60 60 27 70 50 60 60 60 60 60 60 60 60 60

3 3 3 3 3 3 3 3 3 3 3 0.5 1 2 4 5 3 3 3 3

49 47 98 96 51 61 88 96 39 98 67 64 88 88 97 97 38 42 97 88

a

Reaction condition: diketone (5 mmol), amine (5.2 mmol), solventfree, air atmosphere. b GC yield. c Reaction carried under O2 atmosphere dReaction carried under N2 atmosphere

efficient carbocatalyst, in addition to IQGO, various CMs such as CNFs, SWCNTs, MWCNTs, and GNPs (Table 1, entries 2−6) were tested as catalyst. Among them, both IQGO and SWCNTs gave 3a in better yields of 96% and 98%, respectively. The better yield maybe due to the higher surface area of the IQGO (767 m2/g) and SWCNTs (462 m2/g)42 compared to MWCNTs (210 m2/g),43 CNFs (352 m2/g),44 and GNPs (63 m2/g).45 In addition, the small size, better dispersion, and the presence of oxygen functionalities would have assisted the IQGO and SWCNTs to achieve the higher yields (Table 1, entries 3 and 4). However, IQGO was chosen as a best carbocatalyst over SWCNTs due to its low-cost, easy recovery and nontoxic. Mainly, the cost of IQGO (ACS Materials, 10 g = 980 USD) is about 10 times lower than the SWCNTs (SigmaAldrich, 1 g = 1353 USD). In fact, the large scale production of SWCNTs is very complicated. Subsequently, the amount of IQGO was optimized and found that a 10 mg of IQGO is efficient enough to catalyze the reaction (Table 1, entries 4, 7, and 8). It was noticed that the temperature played a crucial role in the present IQGO system. At low temperatures (27 and 50 °C), the rate of the reaction was very slow (Table 1, entries 9 and 11). Alike, increasing the reaction temperature, from 60 to 70 °C, did not show any significant improvement in the yield (Table 1, entry 10). At 60 °C, the IQGO gave a better 96% yield of 3a (Table 1, entry 4). In time optimization, 3 h was found to be the best reaction time since it gave 96% of 3a. No significant improvement in the yield of 3a was noticed even after prolonging the reaction time (from 3 to 5 h) (Table 1, entries 15 and 16). A series of reactions was performed to 1255

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the results confirmed the superior catalytic activity of the present IQGO-system toward the synthesis of β-ketoenamines. The activity of IQGO is better or comparable with other reported metal and nonmetal catalysts including Cu/AlO(OH),27 NaAuCl4,29 Ag nanoparticles,28,30 Mg(ClO4)2,31 CoCl 2 ·6H 2 O, 32 Zn(OAc) 2 ·2H 2 O, 33 CeCl 3 ·7H 2 O, 34 Zn(ClO4)2·6H2O,35 ZrCl4,36 SnCl4,37 Cu nanoparticles,38 Cu(II) nitrate trihydrate,39 ZrOCl2·8H2O,40 Ag/γ-Fe2O3@TiO2,46 and GO-SnO247 InBr3.41 The better activity is obviously due to the three main reasons: (1) the higher surface area of IQGO (767 m2/g), (2) presence of oxygen functionalities (CO, −COOH, COH, and −COC−) and interconnected pores on IQGO, and (3) higher level of dispersion of IQGO in the reaction mixture. Mainly, the −COOH on IQGO would have played a significant role as an active site in the synthesis of β-ketoenamines. Density functional theory (DFT) calcinations are very useful to determine the suitable reaction pathway of catalytic reactions.46−49 DFT calculations were previously performed for the synthesis of β-ketoenamines by Babu and co-workers.27 The computed result confirms that the enol form of acetyl acetone is more stable and reactive than the diketone from. Moreover, the activation energy required for the uncatalyzed reaction was found to be very high compared to catalyzed reaction. In particular, the catalyst active site coordinates to the carbonyl oxygen of 1a followed by the addition of 2a could lead toward the low-energy reaction pathways. Based upon the present results and earlier reports, a possible reaction mechanism is proposed for the IQGO catalyzed synthesis of β-ketoenamines (Figure 4). In the first step, the presence of

Table 2. Scope of the IQGO System

Figure 4. Proposed mechanism for IQGO catalyzed synthesis of βketoenamines.

a

Reaction conditions: diketone (5 mmol), amine (5.2 mmol), IQGO (10 mg), air atmosphere, 60 °C. bGC conversion. cGC yield. dIsolated yield. eSelectivity.

active defect sites or soli acid groups on IQGO binds with the carbonyl oxygen of 1a and a subsequent addition of aniline in step 2 forms an intermediate 2 as shown in Figure 4. In step 3, the elimination of water molecule from 2 yields the desired product 3a. The better performance of catalysts in large scale reactions is one of the very important factors for industrial applications. Surprisingly, the IQGO worked well for scale reaction (Scheme 1). A 50 mg of IQGO was enough to transform a 100 mmol of the reactants (1a and 2a) to the corresponding product. It is worth mentioning that the present IQGO system affords 3a in

2c, 2d, and 2g in the presence of 10 mg IQGO to obtain (Z)1,1,1-trifluoro-4-(phenylamino)pent-3-en-2-one (3q), (Z)1,1,1- trifluoro-4-(phenylamino)pent-3-en-2-one (3r), (Z)1,1,1-trifluoro-4-((4-methoxyphenyl)amino)pent-3-en-2-one (3s), (Z)-1,1,1-trifluoro-4-((4-fluorophenyl)amino)pent-3-en2-one (3t), (Z)-4-(cyclohexylamino)-1,1,1-trifluoropent-3-en2-one (3w), respectively. The yield of 3q, 3r, 3s, 3t, and 3w was calculated to be 100, 100, 100, 100, and 95% (with 100% selectivity), respectively (Table 2, entries, 17−20, 23). Overall, 1256

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second, third, fourth, and fifth cycle, respectively. The stability of IQGO after fifth cycle was investigated by means of TEM, Raman, and SEM-EDS; the results are provided in Figure 5. In general, due to van der Waals interaction, GO nanosheets can be easily reassembled to form multilayer agglomerates. However, the TEM image of IQGO after fifth use shows that there is no face-to-face agglomeration between the sheets. Alike pure IQGO, wrinkles and bends at several places can be seen. The Raman spectrum of IQGO after fifth use shows the characteristic G band and D band with ID/IG ratio of 0.89. The SEM-EDS result confirmed that the wt % of C and O in used IQGO was similar to that of fresh IQGO. The results ensure that the IQGO is easily recoverable, reusable, and stable.

Scheme 1. Scale Reaction of IQGO Catalyzed Condensation of Acetyalaceton (1a) and Aniline (2a)

good 93% yield (100% selectivity) after the reaction mixture was stirred under air atmosphere at 60 °C for 6 h. Chemoselectivity of the present IQGO system was also studied (Scheme 2). A mixture of 1a (5 mmol), 2a (5 mmol),

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CONCLUSIONS A highly efficient IQGO-based carbocatalytic system was developed for the synthesis of β-ketoenamines. The IQGO system is applicable to a wide range of substrates. Chemoselectivity and scale reaction of the IQGO system were found to be very impressive. The carbocatalyst is highly reusable, easily recoverable, and stable. Overall, we postulate the advantages (metal-free, solvent-free, mild reaction conditions, easy recovery, reusability, scale reaction, chemoselectivity, and high stability) could make the IQGO system an alternate choice to the existing metal- and nonmetal-based catalytic systems.

Scheme 2. Chemoselectivity of IQGO System

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2h (5 mmol), and IQGO (10 mg) was magnetically stirred under air atmosphere at 60 °C for 3 h. It was found that the IQGO system was favored for the selective condesation of acetylacetone with butylamine but not with aniline which maybe due to the higher neucleophilic nature of the butylamine. An excellent 99% yield of 3h was obtained; whereas the yield of 3a was calculated to be 0%, indicating the high level of chemoselevtive nature of IQGO system. To further the significant features of IQGO such as recovery, reusability and stability were investigated in detail (Figure 5). After the reaction, about 95% of IQGO was recovered by simple centifugation method. The recoverd IQGO can be reused at least for 5 cycles without any significant loss in the yield. The IQGO gave 90%, 89%, 88%, and 85% of 3a at

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.6b02766. Experimental section, 1H and 13C NMR spectra, GC chromatogram and mass spectrum (GC) (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (I. M. Chung). *E-mail: [email protected] (I. S. Kim). *E-mail: [email protected] (M. Gopiraman). ORCID

Mayakrishnan Gopiraman: 0000-0002-0137-8617 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This study was supported by Konkuk University KU research professor program. Dian Deng would like to thank Epson International Scholarship Foundation for scholarship.

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REFERENCES

(1) Heveling, J. Heterogeneous Catalytic Chemistry by Example of Industrial Applications. J. Chem. Educ. 2012, 89, 1530−1536. (2) Li, Y.; Shen, W. Morphology-Dependent Nanocatalysts: RodShaped Oxides. Chem. Soc. Rev. 2014, 43, 1543−1574. (3) Fechete, I.; Wang, Y.; Vedrine, J. C. The Past, Present and Future of Heterogeneous Catalysis. Catal. Today 2012, 189, 2−27. (4) Albero, J.; Garcia, H. Doped Graphenes in Catalysis. J. Mol. Catal. A: Chem. 2015, 408, 296−309. (5) Anastas, P. T.; Kirchhoff, M. M. Origins, current status, and future challenges of green chemistry. Acc. Chem. Res. 2002, 35, 686− 694.

Figure 5. (a) Reusability test of IQGO. (b) TEM image, (c) SEMEDS, and (d) Raman spectrum of IQGO after 5th use. 1257

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ACS Sustainable Chemistry & Engineering (6) Trimm, D. L. The Regeneration or Disposal of Deactivated Heterogeneous Catalysts. Appl. Catal., A 2001, 212, 153−160. (7) Yu, D.; Nagelli, E.; Du, F.; Dai, L. Metal-Free Carbon Nanomaterials Become More Active than Metal Catalysts and Last Longer. J. Phys. Chem. Lett. 2010, 1, 2165−2173. (8) Larsen, E. C.; Walton, J. H. Activated Carbon as a Catalyst in Certain Oxidation-Reduction Reactions. J. Phys. Chem. 1940, 44, 70− 85. (9) Keller, N.; Maksimova, N. I.; Roddatis, V. V.; Schur, M.; Mestl, G.; Butenko, Y. V.; Kuznetsov, V. L.; Schlogl, R. The Catalytic Use of Onion-Like Carbon Materials for Styrene Synthesis by Oxidative Dehydrogenation of Ethylbenzene. Angew. Chem., Int. Ed. 2002, 41, 1885−1888. (10) Yan, Y.; Miao, J.; Yang, Z.; Xiao, F. X.; Yang, H. B.; Liu, B.; Yang, Y. Carbon Nanotube Catalysts: Recent Advances in Synthesis, Characterization and Applications. Chem. Soc. Rev. 2015, 44, 3295− 3346. (11) Zhang, J.; Liu, X.; Blume, R.; Zhang, A.; Schlogl, R.; Su, D. S. Surface-Modified Carbon Nanotubes Catalyze Oxidative Dehydrogenation of n-Butane. Science 2008, 322, 73−77. (12) Tang, P.; Hu, G.; Li, M.; Ma, D. Graphene-Based Metal-Free Catalysts for Catalytic Reactions in the Liquid Phase. ACS Catal. 2016, 6, 6948−6958. (13) Su, C.; Loh, K. P. Carbocatalysts: Graphene Oxide and its Derivatives. Acc. Chem. Res. 2013, 46, 2275−2285. (14) Lv, G.; Wang, H.; Yang, Y.; Deng, T.; Chen, C.; Zhu, Y.; Hou, X. Graphene Oxide: A Convenient Metal-Free Carbocatalyst for Facilitating Aerobic Oxidation of 5-Hydroxymethylfurfural into 2,5Diformylfuran. ACS Catal. 2015, 5, 5636−5646. (15) Huang, H.; Huang, J.; Liu, Y. M.; He, H. Y.; Cao, Y.; Fan, K. N. Graphite Oxide as an Efficient and Durable Metal-Free Catalyst for Aerobic Oxidative Coupling of Amines to Imines. Green Chem. 2012, 14, 930−934. (16) Liu, X.; Dai, L. Carbon-based metal-free catalysts. Nat. Rev. Mater. 2016, 1, 16064. (17) Navalon, S.; Dhakshinamoorthy, A.; Alvaro, M.; Garcia, H. Carbocatalysis by Graphene-Based Materials. Chem. Rev. 2014, 114, 6179−6212. (18) Lin, Y.; Li, B.; Feng, Z.; Kim, Y. A.; Endo, M.; Su, D. S. Efficient Metal-Free Catalytic Reaction Pathway for Selective Oxidation of Substituted Phenols. ACS Catal. 2015, 5, 5921−5926. (19) Haag, D.; Kung, H. H. Metal Free Graphene Based Catalysts: A Review. Top. Catal. 2014, 57, 762−773. (20) Kong, X. K.; Chen, C. L.; Chen, Q. W. Doped Graphene for Metal-Free Catalysis. Chem. Soc. Rev. 2014, 43, 2841−2857. (21) Gao, Y.; Tang, P.; Zhou, H.; Zhang, W.; Yang, H.; Yan, N.; Hu, G.; Mei, D.; Wang, J.; Ma, D. Graphene Oxide Catalyzed C¢H Bond Activation: The Importance of Oxygen Functional Groups for Biaryl Construction. Angew. Chem., Int. Ed. 2016, 55, 3124−3128. (22) Georgakilas, V.; Tiwari, J. N.; Kemp, K. C.; Perman, J. A.; Bourlinos, A. B.; Kim, K. S.; Zboril, R. Noncovalent, Functionalization of Graphene and Graphene Oxide for Energy Materials, Biosensing, Catalytic, and Biomedical Applications. Chem. Rev. 2016, 116, 5464− 5519. (23) Huang, C.; Li, C.; Shi. Graphene Based Catalysts. G. Energy Environ. Sci. 2012, 5, 8848−8868. (24) Eddington, N. D.; Cox, D. S.; Khurana, M.; Salama, N. N.; Stables, J. P.; Harrison, S. J.; Negussie, A.; Taylor, R. S.; Tran, U. Q.; Moore, J. A.; Barrow, J. C.; Scott, K. R. Synthesis and Anticonvulsant Activity of Enaminones: Part 7. Synthesis and Anticonvulsant Evaluation of Ethyl 4-[(Substituted Phenyl) Amino]-6-Methyl-2Oxocyclohex-3-Ene-1-Carboxylates and their Corresponding 5-Methylcyclohex-2-Enone Derivatives. Eur. J. Med. Chem. 2003, 38, 49−64. (25) Li, G.; Watson, K.; Buckheit, R. W.; Zhang, Y. Total Synthesis of Anibamine, A Novel Natural Product as a Chemokine Receptor CCR5 Antagonist. Org. Lett. 2007, 9, 2043−2046. (26) Neto, B. A. D.; Lapis, A. A. M.; Bernd, A. B.; Russowsky, D. Studies on the Eschenmoser Coupling Reaction and Insights on its

Mechanism. Application in the Synthesis of Norallosedamine and other Alkaloids. Tetrahedron 2009, 65, 2484−2496. (27) Babu, S. G.; Thomas, B.; Nijamudheen, A.; Datta, A.; Karvembu, R. Cu/AlO(OH)-Catalyzed Formation of β-Enamino Ketones/Esters Under Solvent, Ligand and Base Free Conditions − Experimental and Computational Studies. Catal. Sci. Technol. 2012, 2, 1872−1878. (28) Sun, J.; Dong, Z.; Li, P.; Zhang, F.; Wei, S.; Shi, Z.; Li, R. Ag Nanoparticles in Hollow Magnetic Mesoporous Spheres: A Highly Efficient and Magnetically Separable Catalyst for Synthesis of βEnaminones. Mater. Chem. Phys. 2013, 140, 1−6. (29) Arcadi, A.; Bianchi; Di Giuseppe, S.; Marinelli, F. Gold Catalysis in the Reactions of 1, 3-Dicarbonyls with Nucleophiles. Green Chem. 2003, 5, 64−67. (30) Bhatte, K. D.; Tambade, P. J.; Dhake, K. P.; Bhanage, B. M. Silver Nanoparticles as an Efficient, Heterogeneous and Recyclable Catalyst for Synthesis of β-Enaminones. Catal. Commun. 2010, 11, 1233−1237. (31) Zhao, Y.; Zhao, J.; Zhou, Y.; Lei, Z.; Li, L.; Zhang, H. Efficient Synthesis of β-Amino-α, β-Unsaturated Carbonyl Compounds. New J. Chem. 2005, 29, 769−772. (32) Zhang, Z. H.; Hu, J. Y. Cobalt (II) Chloride-Mediated Synthesis of beta-Enamino Compounds under Solvent-Free Conditions. J. Braz. Chem. Soc. 2006, 17, 1447−1451. (33) Vohra, R. K.; Renaud, J. L.; Bruneau, C. Efficient Synthesis of βAminoacrylates and β-Enaminones Catalyzed by Zn(OAc)2·2H2O. Collect. Czech. Chem. Commun. 2005, 70, 1943−1952. (34) Khodaei, M. M.; Khosropour, A. R.; Kookhazadeh, M. Enamination of β-Dicarbonyl Compounds Catalyzed by CeCl3· 7H2O at Ambient Conditions: Ionic Liquid and Solvent-Free Media. Synlett 2004, 11, 1980−1984. (35) Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Zn (ClO4)2·6H2O as a Powerful Catalyst for the Conversion of β-Ketoesters into β-Enamino Esters. Synlett 2004, 2, 239−242. (36) Lin, J.; Zhang, L. F. ZrCl4-Catalyzed Efficient Synthesis of Enaminones and Enamino Esters under Solvent-Free Conditions. Monatsh. Chem. 2007, 138, 77−81. (37) Astruc, F. L.; Aranzaes, J. R.; Lu, F. Nanoparticles as Recyclable Catalysts: The Frontier between Homogeneous and Heterogeneous Catalysis. Angew. Chem., Int. Ed. 2005, 44, 7852−7872. (38) Kidwai, M.; Bhardwaj, S.; Mishra, N. K.; Bansal, V.; Kumar, A.; Mozumdar, S. A Novel Method for the Synthesis of β-Enaminones using Cu-Nanoparticles as Catalyst. Catal. Commun. 2009, 10, 1514− 1517. (39) Li, G. C. Simple and Efficient Synthesis of 3-Aminopropenones and 3-Aminopropenoates Catalyzed by Copper (II) Nitrate Trihydrate under Solvent-Free Conditions. Monatsh. Chem. 2008, 139, 789−792. (40) Zhang, Z. H.; Li, T. S.; Li, J. J. Synthesis of Enaminones and Enamino Esters Catalysed by ZrOCl2·8H2O. Catal. Commun. 2007, 8, 1615−1620. (41) Zhang, Z. H.; Yin, L.; Wang, Y. M. A General and Efficient Method for the Preparation of β-Enamino Ketones and Esters Catalyzed by Indium Tribromide. Adv. Synth. Catal. 2006, 348, 184− 190. (42) Gopiraman, M.; Karvembu, R.; Kim, I. S. Highly Active, Selective, and Reusable RuO2/SWCNT Catalyst for Heck Olefination of Aryl halides. ACS Catal. 2014, 4, 2118−2129. (43) Gopiraman, M.; Babu, S. G.; Khatri, Z.; Kai, W.; Kim, Y. A.; Endo, M.; Karvembu, R.; Kim, I. S. An Efficient, Reusable CopperOxide/Carbon-Nanotube Catalyst for N-Arylation of Imidazole. Carbon 2013, 62, 135−148. (44) Wei, K.; Kim, K.-O.; Song, K.-H.; Kang, C.-Y.; Lee, J. S.; Gopiraman, M.; Kim, I. S. Nitrogen- and Oxygen-Containing Porous Ultrafine Carbon Nanofiber: A Highly Flexible Electrode Material for Supercapacitor. J. Mater. Sci. Technol. 2016, DOI: 10.1016/ j.jmst.2016.03.014. (45) Gopiraman, M.; Babu, S. G.; Khatri, Z.; Kai, W.; Kim, Y. A.; Endo, M.; Karvembu, R.; Kim, I. S. Dry Synthesis of Easily Tunable Nano Ruthenium Supported on Graphene: Novel Nanocatalysts for 1258

DOI: 10.1021/acssuschemeng.6b02766 ACS Sustainable Chem. Eng. 2017, 5, 1253−1259

Letter

ACS Sustainable Chemistry & Engineering Aerial Oxidation of Alcohols and Transfer Hydrogenation of Ketones. J. Phys. Chem. C 2013, 117, 23582−23596. (46) Huo, H.; Li, X.; Zhou, X.; Jiao, L.; Zhao, S.; Zhang, L.; Li, W.; Li, S.; Li, R. Fabrication of Ag/γ-Fe2O3@TiO2 Hollow Magnetic Core−Shell Nanospheres as Highly Efficient Catalysts for the Synthesis of β-Enaminones. RSC Adv. 2015, 5, 73612−73618. (47) Kumar, A.; Rout, L.; Dhaka, R. S.; Samal, S. L.; Dash, P. Design of a Graphene Oxide-SnO2 Nanocomposite with Superior Catalytic Efficiency for the Synthesis of β-Enaminones and β-Enaminoesters. RSC Adv. 2015, 5, 39193−39204. (48) Bhattacharjee, R.; Datta, A. Supported Sub-Nanometer Gold Cluster Catalyzed Transfer Hydrogenation of Aldehydes to Alcohols. J. Phys. Chem. C 2016, 120, 24449−24456. (49) Bhattacharjee, R.; Nijamudheen, A.; Datta, A. Mechanistic Insights into the Synergistic Catalysis by Au(I), Ga(III), and Counterions in Nakamura Reaction. Org. Biomol. Chem. 2015, 13, 7412−7420.

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DOI: 10.1021/acssuschemeng.6b02766 ACS Sustainable Chem. Eng. 2017, 5, 1253−1259