An efficient route to 1,8-dioxo-octahydroxanthenes and

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Mar 24, 2017 - a Department of Chemistry, B. N. Bandodkar College of Science, Thane, India b Department of Chemistry, Wilson College, Chowpatty, Mumbai, ...
Catalysis Communications 97 (2017) 138–145

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An efficient route to 1,8-dioxo-octahydroxanthenes and -decahydroacridines using a sulfated zirconia catalyst

MARK

Sandeep S. Kahandala, Anand S. Burangeb,⁎, Sandip R. Kalec, Pepijn Prinsend, Rafael Luqued, Radha V. Jayarame,⁎ a

Department of Chemistry, B. N. Bandodkar College of Science, Thane, India Department of Chemistry, Wilson College, Chowpatty, Mumbai, India c Department of Chemistry, SIES College of Arts, Science and Commerce, Mumbai, India d Departamento de Quimica Organica, Universidad de Cordoba, Edificio Marie Curie (C-3), Ctra Nnal IV-A, km 396, E14014 Cordoba, Spain e Department of Chemistry, Institute of Chemical Technology, Matunga, Mumbai, India b

A R T I C L E I N F O

A B S T R A C T

Keywords: 1,8-dioxo-octahydroxanthenes 1,8-dioxo-decahydroacridines Sulfated zirconia Heterogeneous catalyst

Sulfated zirconia results to be a very efficient catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8dioxo-decahydroacridines without tedious work-up procedures. While 1,8-dioxo-octahydroxanthenes are prepared from aldehyde and 5,5-dimethyl-1,3-cyclohexenedione (dimedone), 1,8-dioxo-decahydroacridines are prepared from this reactant mixture with amines. This method provides a mild catalytic protocol for the synthesis of functionalized xanthene and acridine derivatives. The catalysts were characterized by XRD, FT-IR, TGA-DSC, SEM-EDAX and surface acidity and showed excellent re-usability up to 6 consecutive cycles.

1. Introduction Xanthene derivatives are interesting compounds with potential high-added value for the pharmaceutical sector. They can used as dyes, fluorescents and chiroptical molecular switches [1–4]. Xanthenedione derivatives have been used as versatile synthons due to the inherent reactivity of its pyran ring [5] and show antibactericidal [6], antiviral [7] and anti-inflammatory activity [8]. Some benzoxanthenes are also used as dyes in laser technology [9–12]. Acridine derivatives have been used as antimalarials [13,14] and some of them exhibited promising results in chemotherapy of cancer [15,16]. These derivatives are also frequently used in the industry, especially for the production of dyes [17]. The importance of xanthenes and acridines has promoted chemists to explore greener synthesis routes and protocols. In recent years various advances have been achieved in this field using Lewis and Brönsted acids. The methods developed for the synthesis of xanthenes employ HCl [18], p-dodecylbenzenesulfonic acid (p-docecylSO3H) [19], triethylbenzylammonium chloride [20], diammonium hydrogen phosphate [21], methylSO3H [22], β-cyclodextrinSO3H [23],ultrasonic irradiation [24], Amberlyst-15 [25], H3PW12O40 supported MCM-41 [26], LiBr [27], MCM-41SO3H assisted by ultrasonics [28] and ionic liquids [29]. Previously reported acridine synthesis protocols employ commercial quinolones through five consecutive steps followed by a Rh



catalysed benzannulation. Although a considerable amount of improved methods are available and despite the potential utility of these protocols, they still present one or several drawbacks such as the poor catalyst re-usability, prolonged reaction time, harsh conditions and/or poor product yields. These drawbacks have led us to further improve the synthesis of xanthene derivatives using a novel protocol. Here, we report a mild protocol for the synthesis of 1,8-dioxo-octahydroxanthenes and 1,8-dioxo-decahydroacridines using sulfated zirconia (Zr) as a catalyst (Scheme 1, 2). 2. Experimental 2.1. Reagents All chemicals and reagents were purchased from SD Fine Chemicals with their highest purity available and used without further purification. 2.2. Preparation of sulfated zirconia catalysts The catalyst was prepared according to a previously reported procedure [30]. Zr(IV) hydroxide was prepared by adding aqueous ammonia to an aqueous solution of ZrOCl2.8H2O (0.3 M), until pH 8.4 was achieved with constant stirring. The precipitate was digested at

Corresponding authors. E-mail addresses: [email protected] (A.S. Burange), [email protected] (R.V. Jayaram).

http://dx.doi.org/10.1016/j.catcom.2017.03.017 Received 14 February 2017; Received in revised form 16 March 2017; Accepted 18 March 2017 Available online 24 March 2017 1566-7367/ © 2017 Elsevier B.V. All rights reserved.

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Scheme 1. SO42 −/ZrO2 catalysed synthesis of 1,8-dioxo-octahydroxanthenes.

100 °C in a water bath for 1 h, washed with deionised water until a chloride free filtrate was obtained and finally dried at 120 °C for 24 h. For sulfation, 5 g of dry gel was introduced into 75 mL solution of 1.0 N H2SO4 for 30 min under vigorous stirring and then filtered without washing, dried at 100 °C and calcined at 600 °C for 4 h. The solid obtained after sulfation and calcination is designated as SO42 −/ZrO2 catalyst. 2.3. Characterization of sulfated zirconia catalyst Fig. 1. SEM image of the sulfated zircona catalyst (SO42 −/ZrO2).

Sulfated zirconia was characterized by XRD, FT-IR, TGA-DSC, total acidity (n-butylamine potentiometric titration method) and SEM/ EDAX. Powder XRD patterns of catalysts were recorded on a Bruker AXS diffractometer D8 Cu-Kα radiation (λ = 1.540562) in a 2θ range of 0–80°. Surface topographic and elemental analysis was done by Scanning Electron Microscopy. Energy Dispersive X-ray Analysis (SEMEDX) were recorded using a Tungsten source on JEOL model JSM-6390 instrument. Thermogravimetric analysis (TGA) was carried out using a TGA-SDT device (Q600 V8.2 Build 100) in dynamic nitrogen atmosphere between 30 and 900 °C at constant heating rate (10 °C/min.). Potentiometric titrations were carried out using a Equip-tronic model (EQ-614A) instrument with double Junction electrodes. All the products obtained and discussed in this work were characterized by 1H NMR (Varian 300 MHz) and FT-IR.

mixture was cooled to room temperature and the catalyst was recovered by filtration, followed by washing with pure acetone to remove all traces of product or reactant if present. The recovered catalyst was used further for the next catalytic cycle after drying in an oven at 80 °C for 2 h. 3. Results and discussion 3.1. Characterization of sulfated zirconia catalyst Fig. 1 shows a SEM micrograph of the sulfated zirconia catalyst (Zr/ SO42 −) catalyst with particles sizes in the 10–40 μm range. The SO42 −/ ZrO2 catalyst was characterized by FT-IR analysis (see Fig. S1 in the Electronic Supporting Information). The strong absorption at 1114 and 1081 cm− 1 are assigned to bidentate sulfate ions coordinated to a metal oxide [31,32]. These bands are absent in non-sulfated ZrO2. The band at 1625 cm− 1 is assigned to the deformation vibration mode of the adsorbed water. The XRD patterns of the ZrO2 and SO42 −/ZrO2 samples calcined at 600 °C (Fig. S2) show the tetragonal phase of ZrO2. The hydrous zirconia sample calcined at 600 °C contains a mixture of monoclinic and tetragonal phases. The prominent lines attributed to the tetragonal phase indicate that the impregnated sulfate ions exert a strong influence on the zirconia phase modification. The EDS spectrum of sulfated zirconia confirms the presence of S and Zr (Fig. S3). The thermal stability of the SO42 −/ZrO2 catalyst is also analyzed using TGA-DSC (Fig. S4). The weight loss occurs mainly from 30 to 276 °C (4.4% weight loss), while hereafter up to 770 °C the catalyst shows good thermal stability. Significant weight loss occurs from 770 to 900 °C (3.1% weight loss). The determination of the total acidic sites of the catalysts is carried out by potentiometric titration using n-butylamine in acetonitrile as non-aqueous medium (Fig. 2). In this method, the initial electrode potential (Ei) indicates the strength of the acid sites and the end point of the titration the total number of surface acid sites, expressed as mmol acid sites per g catalyst [33]. The amount of n-butylamine consumed was 2.07 and 0.81 mmol/g for SO42 −/ZrO2 and ZrO2, respectively.

2.4. Experimental procedure for the synthesis of 1,8-dioxooctahydroxanthenes The SO42 −/ZrO2 catalyst (15 wt%) was added to a solution of an aromatic aldehyde (1 mmol) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) (2 mmol) in ethanol (3 mL). The mixture was heated at 70 °C for 8–15 h and the reaction was monitored by TLC. After completion of the reaction, the catalyst was separated by filtration, the filtrate dried over anhydrous Na2SO4 and concentrated to dryness. The 1,8-dioxo-octahydroxanthene product was recrystallized from ethanol. All detected products were characterized by comparison of their spectral and physical data with those of reported in literature [15,19,20–27]. 2.5. Experimental procedure for the synthesis of 1,8-dioxodecahydroacridines The SO42 −/ZrO2 catalyst (15 wt%) was added to a solution of an aromatic aldehyde (1 mmol) and 5,5-dimethyl-1,3-cyclohexanedione (2 mmol) followed by an amine (1 mmol) in ethanol (3 mL). The mixture was heated at 70 °C for 8–15 h and the reaction was monitored by TLC. After completion of the reaction, the catalyst was separated by filtration, the filtrate dried over anhydrous Na2SO4 and concentrated to dryness. The 1,8-dioxo-octahydroacridine product was recrystallized from ethanol. All detected products were characterized by comparison of their spectral and physical data with those of reported in literature [15,22,25,27]. The products were further analyzed by 1H and 13C NMR (Varian 300) using TMS as internal standard.

3.2. Application of sulfated zirconia catalyst for the synthesis of 1,8-dioxooctahydroxanthenes In continuation of our efforts in exploring metal oxide based catalysis [34–35], here we screen various (surface modified) metal oxides for the synthesis of 1,8-dioxo-octahydroxanthenes from benzaldehyde with 5,5-dimethyl-1,3-cyclohexanedione as a model reaction (Scheme 1). When the reaction was carried out without any catalyst, no

2.6. Catalyst re-usability After completion of the reaction as described above, the reaction 139

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ranging from 5 to 25 wt% (Table S2). Initially higher catalyst loading gives higher product yield, up to 15 wt% (Table S2, entries 1–3); but on further increase in catalyst loading no profound effect on the product yield was observed (entries 4–5). 3.4. Catalyst versatility and re-usability To check the versatility of the catalyst, reactions of dimedone with a variety of aldehydes are carried out as depicted in Table 2. The IR and NMR spectra from the obtained products are available in Fig. S5–S9 in the ESI. The reaction of 5,5-dimethyl-1,3-cyclohexanedione with benzaldehyde provided 95% yield of the desired xanthene (Table 2, entry 1). Reactions of aldehydes with electron donating and withdrawing substituents such as –OCH3, –C10H6(OCH3), −(OCH3)2, −(NCH3)2, –OH, eCl, −(CHCH3)2, eBr, and –NO2 are also studied; the corresponding xanthenes are all obtained in good yields (Table 2, entries 2–12), showing its tolerance to electronic effects. Changing the substituent (−OH and eCl) position to ortho, meta or para shows only minor effects (Table 2, entries 6–9). Aromatic aldehydes react faster as compared to aliphatic aldehydes (Table 2, entry 13). Excellent yields are achieved with cinammaldehyde, in which the olephinic bond remains intact (Table 2, entry 14). The heterocyclic aldehyde 2formylthiophene also reacts efficiently with 5,5-dimethyl-1,3-cyclohexanedione (Table 2, entry 15). Similar yields were observed when replacing the latter reactant by 1,3-cyclohexanedione for the reactions with benzaldehyde and 4-hydroxy-benzaldehyde (Table 2, entries 16–17). To further extend the reaction scope of the catalyst, the synthesis of 1,8-dioxo-octahydroacridines (Scheme 2) is carried out under identical reaction conditions as used for the synthesis of the corresponding xanthenes. Various aldehydes are tested, but with several amines along with 5,5-dimethyl-1,3–cyclohexenedione, giving good yields (89–95%) of the desired acridines (Table 2, entries 18–23). The re-usability of the catalysts is a key factor that highly determines the potential applications for industries. The re-usability of the SO42 −/ZrO2 catalyst was analyzed in the synthesis of 1,8-dioxooctahydroxanthenes for 6 consecutive cycles (Fig. 3). During the study, it was observed that the catalyst was effectively recycled without any significant loss in catalytic activity. These results demonstrate the effectiveness of the presented protocol and shows some advantages over other synthesis protocols (see ESI). Earlier, the sulfated zirconia has been used as a catalyst for the trans esterification of soyabean oil and for various organic transformations (see ESI for details). Herein, we observed it's effectiveness in multicomponent reaction for the synthesis of xanthenes and acridines.

Fig. 2. Potentiometric n-butylamine titration curves of a) ZrO2, b) B2O3/ZrO2, c) PO43 −/ ZrO2, d) SO42 −/ZrO2, e) CeO2, f) SO42 −/CeO2, g) SO42 −/SnO2 and h) SO42 −/Fe2O3. Table 1 Effect of catalyst on the synthesis of 1,8 dioxo-octahydroxanthenes.a Entry

Catalyst

Ei (mV)b

Surface acidity (mmol/g)

Yieldc

1 2 3 4 5 6 7 8 9

CeO2 ZrO2 SO42 −/CeO2 SO42 −/ZrO2 SO42 −/Fe2O3 SO42 −/SnO2 SO42 −/TiO2 PO43 −/ZrO2 B2O3/ZrO2

27 55 154 168 156 160 162 125 145

0.3 0.8 1.22 2.07 1.74 1.95 1.83 1.01 1.54

12 22 25 95 73 82 85 56 68

a Reaction conditions: benzaldehyde (1 mmol), dimedone (2 mmol) in ethanol (3 mL), 8 h, 70 °C, 15 wt% catalyst (on dimedone weight). b Inital electrode potential (mV). c Isolated yield of 1,8 dioxo-octahydroxanthenes after 15 h.

product formation was observed even after 15 h. Among the various catalysts, the SO42 −/ZrO2 catalyst provides the highest yield whereas other sulfated catalysts give only moderate yields (Table 1). The results indicate a good correlation between the strength and number of acid sites and the product yield. With CeO2 or ZrO2 only (entries 1–2), the product yield was much less and predominantly reaction intermediate was observed. The SO42 −/CeO2 catalyst (entry 3) yields only 25% of 1,8-dioxo-octahydroxanthene, even after 15 h. The SO42 −/ZrO2 gives the highest yield (95%) as compared to the SO42 −/Fe2O3, SO42 −/SnO2 and SO42 −/TiO2 catalysts (25–85%) (entries 4–8). We have also carried out the reaction using PO43 −/ZrO2 and B2O3/ZrO2 catalysts; both show significant lower activity (entries 8–9). The high catalytic activity of the SO42 −/ZrO2 catalyst can mostly be attributed to the high total number of acidic sites. Moreover, this catalyst showed the highest Ei value (168 mV), corresponding to some highly acidic sites present on the surface.

4. Conclusions We report an efficient protocol for the synthesis of 1,8-dioxooctahydroxanthenes from 5,5-dimethyl-1,3-cyclohexanedione (dimedone) and an aromatic aldehyde using sulfated zirconia as the catalyst. Using the same catalyst and adding an amine to the reaction mixture, we also report the synthesis of 1,8-dioxo-decahydroacridines. The catalyst shows remarkable activity tolerance when using aldehydes and amines with both electron withdrawing and donating aromatic substituents. The catalysts can be readily recovered by simple filtration and re-used with retention of catalytic activity up to six consecutive cycles. The simple work-up procedure makes the protocol superior to existing methodologies.

3.3. Optimization of the 1,8-dioxo-octahydroxanthene synthesis The effect of various polar and non-polar solvents on the reaction is also studied (see Table S1). A polar solvents like 1,4-dioxane, toluene and ethyl acetate show moderate product yields (Table 2, entries 1–3), whereas tetrahydrofuran and dichloro-ethane give 56 and 83% product yield, respectively (entries 4 and 5). Among polar aprotic solvents, acetonitrile provides a maximum yield of 87% (entry 6). Among all the screened solvents, ethanol performs the best (95% yield, entry 7) and is therefore further used for optimization. In an effort to determine the optimum catalyst loading, we studied the effect of catalyst loadings

Acknowledgements The author (S.S. Kahandal) is greatly thankful to Council of Scientific and Industrial Research, New Delhi (CSIR, India) for providing Senior Research Fellowship (SRF). Author A.S. Burange is thankful to CSIR-India for Nehru Postdoctoral Fellowship. 140

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Table 2 Synthesis of 1,8-dioxo-octahydroxanthenes (Scheme 1) and 1,8-dioxo- decahydroacridine (Scheme 2) using SO42 −/ZrO2 catalyst.a Entry

Ar-CHO

R-NH2

Product

Time (h)

Yield (%)

1



8

95

2



8

90

3



8

84

4



8

89

5



8

85

6



8

91

7



8

89

8



8

93

(continued on next page)

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Table 2 (continued) Entry

Ar-CHO

R-NH2

Product

Time (h)

Yield (%)

9



8

87

10



8

92

11



8

94

12



8

89

13



12

84

14



8

94

15



8

86

16b



8

142

90 (continued on next page)

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Table 2 (continued) Entry

Ar-CHO

R-NH2

Time (h)

Yield (%)

8

93

18c

8

89

19c

8

92

20c

8

95

21c

8

89

22c

8

92

17b

Product



(continued on next page)

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Table 2 (continued) Entry

Ar-CHO

R-NH2

Product

23c

a b c

Time (h)

Yield (%)

8

95

Reaction conditions:aldehyde (1 mmol), dimedone (2 mmol), ethanol (3 mL), 70 °C, 15 wt% SO42 −/ZrO2 (on dimedone weight). 1,3-cyclohexanedione. Aldehyde (1 mmol), dimedone (2 mmol), amine (1 mmol), ethanol (3 mL), 70 °C, 15 wt% SO42 −/ZrO2 (on dimedone weight). [3] B.L. Feringa, The art of building small: from molecular switches to molecular motors, J. Org. Chem. 72 (2007) 6635–6652. [4] K. Chibale, M. Visser, D.V. Schalkwyk, P.J. Smith, A. Saravanamuthu, A.H. Fairlamb, Exploring the potential of xanthene derivatives as trypanothione reductase inhibitors and chloroquine potentiating agents, Tetrahedron 59 (2003) 2289–2296. [5] C.N. O'Callaghan, T.B.H. McMurry, Synthetic reactions of methyl XY-carbonyl-4H1-benzopyran-4-yl cyanoethanoate, J. Chem. Res. (1995) 214–218. [6] R.W. Lambert, J.A. Martin, J.H. Merrett, K.E.B. Parkes, G.J. Thomas, Pyrimidines nucleosides, Patent WO 1997006178, 20 February 1997. [7] S. Hatakeyma, N. Ochi, H. Numata, S. Takano, A new route to substituted 3methoxycarbonyldihydropyrans; enantioselective synthesis of (−)-methyl elenolate, J. Chem. Soc. Chem. Commun. (1988) 1202–1204. [8] S. Girault, P. Grellier, A. Berecibar, L. Maes, E. Mouray, P. Lemiere, M. Debreu, E. Davioud-Charvet, C. Sergheraet, Antimalarial, antitrypanosomal, and antileishmanial activities and cytotoxicity of bis(9-amino-6-chloro-2-methoxyacridines): influence of the linker, J. Med. Chem. 43 (2000) 2646–2654. [9] W. Cholody, B. Horowska, J. Paradziej-Lukowicz, S. Martelli, J. Konopa, Structureactivity relationship for antineoplastic imidazoacridinones: synthesis and antileukemic activity in vivo, J. Med. Chem. 39 (1996) 1028–1032. [10] T. Chen, R. Fico, E.S. Cancellakis, Diacridines, bifunctional intercalators. Chemistry and antitumor activity, J. Med. Chem. 21 (1978) 868–874. [11] W. Denny, G.J. Atwell, B.C. Baguley, L.P.G. Wakelin, J. Med. Chem. 28 (1985) 1568–1574. [12] G. Rewcastle, G.J. Atwell, D. Chambers, B.C. Baguley, W.A. Denny, J. Med. Chem. 29 (1986) 472–477. [13] B.D. Tilak, N.R. Ayyangar, Acridine dyes, Chem. Heterocycl. Comp. 9 (1973) 579–613. [14] A. Albert, The Acridines, Edward Arnold Publications Ltd., London, 1966. [15] N. Srividya, P. Ramamurthy, P. Shanmugasundaram, V.T. Ramakrishnan, Synthesis, characterization, and electrochemistry of some acridine-1,8-dione dyes, J. Org. Chem. 61 (1996) 5083–5089. [16] F. Dolle, F. Hinnen, H. Valette, C. Fuseau, R. Duval, J. Peglion, C. Crouzel, Synthesis of two optically active calcium channel antagonists labelled with carbon-11for in vivo cardiac PET imaging, Bioorg. Med. Chem. 5 (1997) 749–764. [17] Z. Hernandez-Gallegos, P.A.F. Lehman, E. Hong, F. Posadas, E. Hernandez-Gallegos, Novel halogenated 1,4-dihydropyridines:synthesis, bioassay, microsomal oxidation and structure-activity relationships, Eur. J. Med. Chem. 30 (1995) 355–364. [18] E.C. Horning, M.G. Horning, Methone derivatives of aldehydes, J. Org. Chem. 11 (1946) 95–99. [19] T.S. Jin, J.S. Zhang, J.C. Xiao, A.Q. Wang, T.S. Li, Clean synthesis of 1,8-dioxooctahydroxanthene derivatives catalyzed by p-dodecylbenezenesulfonic acid in aqueous media, Synlett 5 (2004) 866–870. [20] X.-S. Wang, D.-Q. Shi, Y.-L. Li, H. Chen, X.-Y. Wei, Z.-M. Zong, A clean synthesis of 1-Oxo-hexahydroxanthene derivatives in aqueous media catalyzed by TEBA, Synth. Commun. 35 (2005) 97–104. [21] F. Darvish, S. Balalaei, F. Chadegani, P. Salehi, Diammonium hydrogen phosphate as a neutral and efficient catalyst for synthesis of 1,8-dioxo-octahydroxanthene derivatives in aqueous media, Synth. Commun. 37 (2007) 1059–1067.

Scheme 2. SO42 −/ZrO2 catalysed synthesis of 1,8 dioxo-decahydroacridines.

Fig. 3. Recyclability of the SO42 −/ZrO2 catalyst in consecutive 1,8-dioxo-octahydroxanthenes synthesis runs.

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