Introduction

Magnetic nanomaterials have attracted much attention owing to their inimitable features and vast utilities in diverse industries. Some features of these substances comprise high performance, eco-friendly nature, thermic and chemical durability, effortless segregation from the process medium, and capacity for constructing numerous kinds of them. Magnetic nanomaterials have been exploited for selective sorption of proteins [1], wastewater treatment [2], tamoxifen determination [3], analysis of pesticides remainder in fruits [4], and degradation of dyes [5]. They have been also utilized in solar cells [6], sensors [7], theranostic nanomedicine [8], electroanalytical methods [9], and organic synthesis (as catalyst) [10-27]. “Solvent-free conditions” is an applicatory and highly efficacious approach which has been extensively exploited in organic synthesis; its privileges compared with “solution conditions” comprise easier workup and purification of products, eco-friendly nature, higher selectivity and yield, saving energy and time, and excluding or detracting waste and sub-products [28-35]. The materials bearing xanthene component are an attractive category of heterocycles, which have a wide range of applications. Antibacterial [36], COX inhibitory [37], anticancer [37], antioxidant [37], antifungal [38], antiproliferative [39], and antileishmanial [40] activities have been reported for xanthenes. Moreover, these materials have been applied in bioimaging [41], fluorophores [42], photothermal therapy [43], and photocatalytic processes [44]. A category of xanthene-bearing heterocycles is 1,8-dioxo-octahydroxanthenes, which can be fabricated form Equation (1) of aldehyde and Equation (2) of dimedone using a catalyst [45-55]. Herein, we have accomplished construction and characterization a novel magnetic nanomaterial titled N¹-(Si-pr)-(N¹,N¹,N⁴,N⁴-tetramethylbenzene-1,4-diaminium) chloride dihydrogen phosphate grafted on Fe₃O₄@SiO₂ (STCDFS), and then we have done the fabrication of 1,8-dioxo-octahydroxanthenes form aryl aldehydes and dimedone using STCDFS.

Experimental

Materials and Apparatuses

The materials and solvents were supplied from Sigma-Aldrich Chemical Company. TLC (silica gel SIL G/UV 254 plates) was exploited to see the reactions progress. Measuring melting points was accomplished by a Thermo Scientific 9200 apparatus. A Bruker Avance DPX FT-NMR device was utilized to run NMR spectra. EDX and elemental mapping analyses were carried out using a TESCAN apparatus (model MIRA II).

FE-SEM pictures were recorded by a TESCAN device (model MIRA III). For recording the FT-IR spectra, a Thermo device (model AVATAR) was applied. XRD analysis was done by a PHILIPS device (Cu Kα radiation, λ=1.54056 Å, model PW1730). VSM analysis was performed using a MDK (Meghnatis Daghigh Kavir, Iran) apparatus at ambient temperature.

Construction of STCDFS

Nano-Fe₃O₄ (nano-magnetite) was constructed pursuant to the published method [56,57]. Nano-magnetite (0.75 g), tetraethyl orthosilicate (2.25 mL), water (15 mL), ethanol (60 mL), and ammonia (2.40 mL) were stirred and refluxed for 12 h to provide material A [23,57-58]. Thereupon, a mixture of A and (3-chloropropyl)trimethoxysilane (0.60 mL, 3.26 mmol) in dry toluene (20 mL) was stirred under reflux conditions for 12 h to synthesize B [23,57]. In continue, N¹,N¹,N⁴,N⁴-tetramethylbenzene-1,4-diamine (0.535 g, 3.26 mmol) was added to B in toluene (20 mL), and stirred under reflux and nitrogen atmosphere for 12 h to fabricate C. Lastly, H₃PO₄ (3.26 mmol) was gently added to C in CH₂Cl₂ (10 mL) at ambient temperature, and stirred under nitrogen atmosphere for 12 h at ambient temperature and 2 h under reflux conditions to construct STCDFS. Before each stage, the reaction mixture was sonicated for 20 min to scatter the particles. The fabricated material in each stage was magnetically separated, washed by the applied solvent in that stage, and dried (Scheme 1).

Scheme 1: The STCDFS fabrication

The Fabrication of 1,8-Dioxo-octahydroxanthenes

Aldehyde (0.25 mmol), dimedone (0.5 mmol, 0.070 g), and STCDFS (0.035 g) were added in a reaction vessel, and the mixture was stirred by a rod at 80 ºC. When TLC showed consuming aldehyde and dimedone, the reaction mixture was cooled to ambient temperature, EtOAc (10 mL) was added, and stirred under reflux conditions for 2 min, followed by magnetically isolation of STCDFS; then, STCDFS was washed by EtOAc (2×3 mL), dried, and utilized for next run. The attained solution after the catalyst isolation was distilled, and the remainder solid was recrystallized from EtOH (95%) to fabricate the pure xanthene.

Selected NMR Data of the Fabricated Xanthenes

3,3,6,6-Tetramethyl-9-phenyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione (a)

¹H NMR (500 MHz, DMSO-d₆): δ (ppm) 0.88 (s, 6H, 2CH₃), 1.01 (s, 6H, 2CH₃), 2.05 (d, J = 16.1 Hz, 2H, CH₂–C=C), 2.24 (d, J = 16.1 Hz, 2H, CH₂–C=C), 2.49 (d, J = 17.7 Hz, 2H, CH₂–C=O), 2.54 (d, J = 17.7 Hz, 2H, CH₂–C=O), 4.52 (s, 1H, methine CH), 7.05-7.08 (m, 1H, Ar), and 7.15-7.20 (m, 4H, Ar); ¹³C-NMR (125 MHz, DMSO-d₆): δ (ppm) 26.6 (CH₃), 28.8 (C–CH₃), 31.3 (C–C=C), 31.9 (methine C), 50.2 (CH₂–C=O), 114.5 (C–C=O), 126.3 (Ar), 127.9 (Ar), 128.2 (Ar), 144.4 (Ar), 162.9 (C–O), and 196.1 (C=O).

9-(2-Chlorophenyl)-3,3,6,6-tetramethyl-3,4,6,7-tetrahydro-2H-xanthene-1,8(5H,9H)-dione (h)

¹H-NMR (500 MHz, DMSO-d₆): δ (ppm) 0.97 (s, 6H, 2CH₃), 1.09 (s, 6H, 2CH₃), 2.09 (d, J = 16.1 Hz, 2H, CH₂–C=C), 2.31 (d, J = 16.1 Hz, 2H, CH₂–C=C), 2.53 (d, J = 17.6 Hz, 2H, CH₂–C=O), 2.64 (d, J = 17.6 Hz, 2H, CH₂–C=O), 4.87 (s, 1H, methine CH), 7.16-7.20 (m, 1H, Ar), and 7.25-7.33 (m, 4H, Ar); ¹³C-NMR (125 MHz, DMSO-d₆): δ (ppm) 26.5 (CH₃), 28.8 (C–CH₃), 31.8 (C–C=C), 33.0 (methine C), 50.2 (CH₂–C=O), 113.2 (C–C=O), 126.6 (Ar), 127.9 (Ar), 129.6 (Ar), 132.2 (Ar), 132.9 (Ar), 142.4 (Ar), 163.3 (C–O), and 196.0 (C=O).

Results and Discussion

Characterization of STCDFS

EDX, elemental mapping, FE-SEM, FT-IR, XRD, and VSM analyses were applied to characterize N¹-(Si-pr)-(N¹,N¹,N⁴,N⁴-tetramethylbenzene-1,4-diaminium) chloride dihydrogen phosphate grafted on Fe₃O₄@SiO₂ (STCDFS). The presence of Fe, O, Si, C, N, Cl, and P in STCDFS structure was corroborated by EDX and elemental mapping analyses (Figures 1 and 2). In addition, suitable distribution of the elements in STCDFS surface was confirmed by the elemental mapping pictures.

According to the FE-SEM picture (Figure 3), STCDFS is a porous material. Furthermore, the particles have diverse shapes and sizes, and are in nano-scale, e.g., 27.0, 47.2, and 57.7 nm. The spectrum and the information of FT-IR analysis are illustrated in Figure 4 and Table 1, correspondingly. Appearing the peaks pertinent to all bonds in STCDFS structure corroborated its successful fabrication.

Figure 5 demonstrates the XRD pattern of SCBFH. The broad peak at 2θ ≈ 19.4-32.3º corroborated presence of the amorphous form of silica in the nanomaterial structure. Existing a cubic spinel structure of nano-magnetite in the SCBFH structure was confirmed by appearing the sharp peaks at 2θ ≈ 30.1, 35.4, 43.2, 53.3, 57.1, and 62.7º in the XRD pattern. Magnetic behavior of STCDFS was investigated by VSM analysis (Figure 6). Saturation magnetization (Ms) of the nanomaterial was found to be ~3.99 emu.g^-1. Ms of the used nano-magnetite as precursor to fabricate STCDFS was 56.7 emu.g^-1 [14]. Coating silica layer on the nano-magnetite, and grafting N¹-(Si-pr)-(N¹,N¹,N⁴,N⁴-tetramethylbenzene-1,4-diaminium) moiety on the silica surface caused decrement of Ms in STCDFS compared with the nano-magnetite.

Catalytic Utility of STCDFS

Catalytic utility of STCDFS was investigated for the fabrication of 1,8-dioxo-octahydroxanthenes. In this regard, the fabrication of xanthene h from 4-chlorobenzaldehyde (0.25 mmol) and dimedone (0.5 mmol) in solvent-free conditions was designated as a model reaction (Scheme 2), and effect of two main factors (catalyst dosage and temperature) was perused on that (this study was done using 0.020-0.037 g of STCDFS at 70-85 °C). Completion of the reaction was occurred without formation of any byproduct using 0.035 g of STCDFS at 80 °C; in this test, isolated yield of xanthene h was 98%, and the reaction time was 5 min. No improvement in the results was observed when STCDFS dosage was increased up to 0.037 g or the temperature up to 85 °C. The domain and productivity of STCDFS for the fabrication of 1, 8-dioxo-octahydroxanthenes were perused via utility of several substituted benzaldehydes in the reaction. Table 2 presents the gained results. High yields of the xanthenes were acquired in short times for benzaldehydes possessing electron-donating, halogen or electron-attracting groups on their para, meta, or ortho positions. High catalytic productivity and widespread domain of STCDFS to fabricate 1,8-dioxo-octahydroxanthenes were confirmed by the results.

Scheme 3 represents the reaction mechanism, which was proposed on basis of the literature [48, 49]. H₂PO₄⁻ of STCDFS catalyzes the fabrication of 1,8-dioxo-octahydroxanthenes thru activation of the electrophiles (by its acidic hydrogen) and the nucleophiles (by its negative oxygen as a weak base) in stages 1, 3, and 4, facilitating elimination of H₂O in stages 2 and 5, and accelerating tautomerization of dimedone in stages 1 and 3.

STCDFS were compared with some catalysts in terms of medium, temperature, time, and yield of the reaction. For this study, the fabrication of xanthene a was chosen. The data, which are tabulated in Table 3, confirmed superiority of STCDFS in comparison with the catalysts in two or more of the factors. Lastly, STCDFS reusability was investigated. The fresh STCDFS catalyzed the fabrication of xanthene j in 98% in 5 min. In first recycling, the product was constructed in 95% in 7 min; in second recycling, the yield decreased to 87%, and the reaction time rose up to 10 min. Hence, STCDFS was reusable for one times without remarkable loss of its performance.

Conclusion

Briefly, we have developed a novel magnetic nanocatalyst, namely N¹-(Si-pr)-(N¹,N¹,N⁴,N⁴-tetramethylbenzene-1,4-diaminium) chloride dihydrogen phosphate grafted on Fe₃O₄@SiO₂. It could efficaciously catalyze the fabrication of 1,8-dioxo-octahydroxanthene from aryl aldehydes and dimedone by its H₂PO₄⁻ group; the acidic hydrogens of H₂PO₄⁻ could activate the electrophiles, and the negative oxygen (as a weak base) could activate the nucleophiles. High performance, excellent yields, quick fabrication of the products, utility of solvent-free technique, and eco-friendly conditions are some privileges of our protocol.

Acknowledgements

We appreciate our University for providing the required materials and apparatuses to accomplish this work.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Funding

This work has not received any specific grant from funding agencies.

Authors' Contributions

Zare has defined the project idea, and supervised it; he has also interpreted the analyses, and written the article and revised it. F. Mostaghar has done the experimental works of the project.

ORCID

Abdolkarim Zare

https://orcid.org/0000-0002-8210-3155

Fatemeh Mostaghar

https://orcid.org/0009-0006-1105-2297

HOW TO CITE THIS ARTICLE

Abdolkarim Zare, Fatemeh Mostaghar. Construction of a Novel Magnetic Nanomaterial, and its Utility as an Effectual Catalyst for the Fabrication of 1, 8-Dioxo-Octahydroxanthenes. Chem. Methodol., 2024, 8(1) 36-23

DOI: https://doi.org/10.48309/chemm.2024.422175.1733 

URL: https://www.chemmethod.com/article_185571.html