Synthesis of 14-Aryl-14 H-dibenzo [ a , j ] xanthene Derivatives Using H-Zeolite A as an Efficient and Reusable Catalyst under Solvent-Free Condition

H-Zeolite A is an efficient, excellent, and reusable catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives by one-pot synthesis of β-naphthol with various aromatic aldehyde derivatives under solvent-free condition. The synthesized zeolite H-Zeolite A was characterized by XRD, SEM, and FT-IR. The synthesized products were characterized by FT-IR and H-NMR spectra. Simple workup procedure, short reaction time, high yield, and reusability of the catalyst are the characteristic features of these reactions.


Synthesis of Zeolite A.
Zeolite A was prepared by dissolving 0.723 g of sodium hydroxide in 80 mL distilled water which was then divided into two equal volumes in polypropylene bottles.).The progress of the reaction was monitored by TLC (n-hexane : ethyl acetate, 3 : 1).After completion of the reaction, mixture was cooled to room temperature.Then the product was washed with ethyl acetate and filtered to remove catalyst.After removal of the solvent, the solid product was obtained and was further recrystallized for ethanol to afford the pure xanthene derivatives.

The Synthesized Zeolite A Was Characterized by XRD, FT-IR, and SEM Techniques and the Reaction Products
Were Characterized by FT-IR and 1 H-NMR

X-Ray Diffraction (XRD).
For X-ray diffraction, the samples were sieved in an ABNT number 200 (0.074 mm) sieve and then placed in an aluminum sample holder for Xray diffraction assays, using Shimadzu XRD 6000 equipment.
The operational details of the technique were set as follows: copper K radiation at 40 KV/30 mA, with a goniometer speed of 2 ∘ /min and a step of 0.02 ∘ in the 2 range scanning from 10 ∘ to 70 ∘ for Na-LTA and 2 range scanning from 0 ∘ to 80 ∘ for H-LTA.

Scanning Electron Microscopy (SEM).
Surface micrographs of H form of Zeolite A were obtained by SEM instrument.Scanning electron micrograms of these materials were taken at 10,000x magnifications to understand their surface morphology and to get the clear view of crystals.

Fourier Transform-Infrared Spectroscopy (FT-IR).
For FT-IR analysis, the H form Zeolite A sample and reaction products were subjected to physical treatment in accordance with the KBr method, which consists of mixing 0.007 g of the sample and 0.1 g KBr and grinding and pressing the solid mixture to 5 tons for 30 s in order to form a pellet that allows the passage of light.The H form of Zeolite A and its reaction products was performed using an infrared spectrophotometer Shimadzu FT-IR in the wavelength ranging from 500 to 4500 cm −1 .

Nuclear Magnetic Resonance (NMR) Spectroscopy
. 1 H-NMR spectra were obtained on Bruker 400 MHz spectrophotometer with CDCl 3 as solvent using tetramethylsilane (TMS) as an internal standard; the chemical shift values are in .

Results and Discussion
The X-ray diffraction pattern of Zeolite-A and its H form is shown in Figure 1.In the X-ray diffraction pattern it is shown that degree of crystallinity is very high and all the materials are crystalline in nature without any amorphous    phase.The sharp peak 2 value for calcined Zeolite A and its H form is 24.5 which is easily observed.Further confirmation from Figure 1 shows that the powder X-ray diffraction pattern of H form Zeolite A is similar to the diffraction pattern of its parent Zeolite A. There is no doubt that there is small difference in crystalline peaks between these two because during the formation of H form some impurities are present in ammonium salt.The SEM morphology of H-form Zeolite A is expressed in Figure 2. The SEM image of H-form Zeolite A shows that particles appear to have a cuboidal shape with extraordinary crystal edges and the particle size ranges between 2 and 5 microns.The FT-IR spectrum of H-form Zeolite A is shown in Figure 3. FT-IR spectrum shows absorption bands at 450 cm −1 which is attributed to Si, Al-O band, and those at 1000 cm −1 and 750 cm −1 are, respectively, attributed to asymmetric and symmetric stretches of the zeolite framework.A band for the OH group is clearly observed at 3400 cm −1 .We have created an excellent and highly efficient method for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives from the reaction of 2-naphthol, various derivatives of aromatic aldehydes, and catalyst H-Zeolite A (0.05 g or 5 mol%) under solvent-free condition at 100 ∘ C, so the concerned reaction was carried out between 4-chlorobenzaldehyde and 2-naphthol as shown in Scheme 2.            To select reaction conditions, first the effect of solvents on the rate of reaction for the synthesis of 14-(4-chlorophenyl)-14H-dibenzo[a,j]xanthene by two-component reaction of 4-chlorobenzaldehyde and 2-naphthol in the presence of catalyst H-Zeolite A (0.05 g) under various solvents is shown in Table 1.
It was detected that the best result was obtained when reaction was carried out under solvent-free condition (Table 1, entry 4).The reaction was over within 15 minutes and the reaction product was obtained in a 95% yield.Next the study was carried out to determine the effect of amount of catalyst H-Zeolite A. The reaction was carried out by varying different amount of catalyst.The best yield was obtained with 0.05 g of the catalyst.Further increase in the amount of catalyst in the above-mentioned reaction did not have any significant change in the reaction product shown in Table 2.
The reason is that the additional acid sites cause no effect because the reactants may reduce sufficient sites to bind with.Hence we used weight of catalyst (0.05 g) for the rest of the reactions.The reusability of the catalyst was clarified in the synthesis of 14-(4-chlorophenyl)-14H-dibenzo[a,j]xanthene.After each run, the catalyst was recovered, washed with solvents, namely, chloroform and ethyl acetate, dried in an oven at 100 ∘ C for 2 h before use, and tested for its activity in the consecutive runs with no fresh catalyst added.The catalyst was tested for four runs as shown in Table 3.The small reduction in the catalytic activity is mainly due to the loss of the catalyst structure during recovery process.To show the advantages of H-Zeolite A in comparison with some other reported catalysts, we found that some results for the synthesis of 14-(4-chlorophenyl)-14Hdibenzo[a,j]xanthene shown in Table 4 indicate that H-Zeolite A is an excellent catalyst with respect to reaction time and yield compared to previously reported literature.
To study the scope of the reaction we utilized various derivatives of aromatic aldehydes to evaluate this procedure.The reaction time and % yield of the products are shown in Table 5.
The electronic effect and the nature of substituents have a strong effect on the yield of the products.Benzaldehyde and other aromatic aldehydes having electronwithdrawing and electron-donating group were used and reacted to give the corresponding xanthene derivatives.In all these above-mentioned cases the yield was excellent and electron-withdrawing groups were strongly more effective than electron-donating group.

Conclusion
In conclusion, an excellent and highly efficient method for the preparation of 14-aryl-14H-dibenzo[a,j]xanthene derivatives has been obtained by the condensation of 2-naphthol with various aromatic aldehydes using the reusable H-Zeolite A as a solid acid heterogeneous catalyst under solvent-free condition.Simple workup procedure, short reaction time, high yield, and reusability of the catalyst are the characteristic features of these reactions.

Figure 2 :
Figure 2: SEM image of H form of Zeolite A.

Figure 3 :
Figure 3: FT-IR pattern of H form of Zeolite A.
To first half add 8.258 g sodium aluminate and mix gently in capped polypropylene bottle until it becomes clear.To the second half add 15.4 g sodium metasilicate and mix gently in capped polypropylene bottle until it becomes clear.Now the silicate solution was poured into

Table 1 :
Effect of different solvents on the reaction between 4chlorobenzaldehyde and 2-naphthol.

Table 2 :
Effect of different amount of catalyst on the reaction between 4-chlorobenzaldehyde and 2-naphthol.

Table 5 :
One-pot synthesis of different xanthene derivatives catalyzed by H-Zeolite A.