One-Pot Synthesis of 7, 7-Dimethyl-4-Phenyl-2-Thioxo-2,3,4,6,7, 8-Hexahydro-1H-Quinazoline-5-OnesUsing Zinc Ferrite Nanocatalyst and Its Bio Evaluation

: A simple and highly efﬁcient protocol for the synthesis of derivatives 7, 7-dimethyl-4-phenyl-2-thioxo-2, 3, 4, 6, 7, 8-hexahydro-1H-quinazoline-5-one from 5, 5-dimethyl cyclohexane-1, 3-dione ( 4a – 4h ) (dimedone) has been described. The aryl aldehydes were substituted with thiourea in the presence of synthesized zinc ferrite nanocatalyst, which increased the yield under reﬂux through condensation, followed by cyclization to give desired products. The other advantages are that it is eco-friendly and economically affordable for large-scale production. Structural validation and characterization of all the newly synthesized compounds were evaluated by spectral analysis (mass spectrometry, proton nuclear magnetic resonance ( 1 HNMR), and Carbon-13 nuclear magnetic resonance( 13 CNMR)spectroscopies. The structure of antibacterial and antifungal assays was performed with the newly synthesized compounds. The antimicrobial activity of title compounds possessing electron-withdrawing groups such as ( 4e – 4h ) (Cl, Br, and cyano group) exhibited more active potential than the electron-donating groups, C 6 H 5 ,4-C 6 H 4 , 3-OC 2 H 5 -4OH-C 6 H 3 , etc., ( 4a – 4d ) containing moiety.


XRDPattern of ZnFe2O4 NPs
The X-ray diffraction (XRD) pattern of ZnFe2O4( Figure 1) shows clear diffraction peaks. The diffraction peak of the powder sample was indexed according to Joint Committee on Powder Diffraction Standards (JCPDS) card no. 22-1012. The material crystallized in a cubic unit cell with space group Fd-3m( Figure 2). The structure was refined by the Rietveld refinement method with the Fullprof software package using the single-phase Fd-3m diffraction data. The unit cell parameters (Table 1) of the crystallite size of the sample were calculated from the most intense diffraction by using Scherrer's formula. The Scherrer method (usingfull width at half maximum (FWHM)) calculates the Scheme 1. Synthesisof 7, 7-dimethyl-4-phenyl-2-thioxo-2, 3,4,6,7, 8-hexahydro-1H-quinazolin-5-ones using zinc ferrite.

XRD Pattern of ZnFe 2 O 4 NPs
The X-ray diffraction (XRD) pattern of ZnFe 2 O 4 ( Figure 1) shows clear diffraction peaks. The diffraction peak of the powder sample was indexed according to Joint Committee on Powder Diffraction Standards (JCPDS) card no. 22-1012. The material crystallized in a cubic unit cell with space group Fd-3m( Figure 2). The structure was refined by the Rietveld refinement method with the Fullprof software package using the single-phase Fd-3m diffraction data. The unit cell parameters (Table 1) of the crystallite size of the sample were calculated from the most intense diffraction by using Scherrer's formula. The Scherrer method (using full width at half maximum (FWHM)) calculates the ratio of the thickness's root-mean-fourthpower to its root-mean-square value. We illustrated that the Scherrer equation's calculation of crystallite size is accurate by comparing it to X-ray Catalysts 2021, 11, 431 3 of 12 diffraction peaks produced by the dynamical theory. In terms of crystalline size and Bragg angle, we also established the range of validity of the acceptable Scherrer equation.
where K is dimensionless shape factor and generally taken 0.94 for spherical particles, λ is the wavelength of X-ray used (Cu − K α = 1.540 Å), and β and θ are the full widths of half maxima and diffraction angle of corresponding diffraction peak.
ratio of the thickness's root-mean-fourthpower to its root-mean-square value. We illus-trated that the Scherrer equation's calculation of crystallite size is accurate by comparing it to X-ray diffraction peaks produced by the dynamical theory. In terms of crystalline size and Bragg angle, we also established the range of validity of the acceptable Scherrer equation.
whereK is dimensionless shape factor and generally taken 0.94 for spherical particles, is the wavelength of X-ray used (Cu−Kα = 1.540 Å ), and and are the full widths of half maxima and diffraction angle of corresponding diffraction peak. The average crystallite size of the powder sample was estimated in the close approximation of 39.16 nm. The difference between the calculated and observed data in the Rietveld refinement method elucidates the goodnessoffit (χ 2 ) of the diffraction pattern. The minimal χ 2 value achieved for the synthesized ZnFe2O4 sample was 2.02, which is implicit in the observed XRD pattern. The lower χ 2 of refined XRD pattern indicates the single-phase and high purity of prepared ZnFe2O4 nanoparticles.
The average crystallite size of the powder sample was estimated in the close approximation of 39.16 nm. The difference between the calculated and observed data in the Rietveld refinement method elucidates the goodness of fit (χ 2 ) of the diffraction pattern. The minimal χ 2 value achieved for the synthesized ZnFe 2 O 4 sample was 2.02, which is implicit in the observed XRD pattern. The lower χ 2 of refined XRD pattern indicates the single-phase and high purity of prepared ZnFe 2 O 4 nanoparticles.

SEM Analysis of ZnFe 2 O 4 NPs
The surface morphology of the acquired ZnFe 2 O 4 (NPs) was documented using a scanning electron microscope (FESEM) (Figure 3). The FESEM image indicated that the ZnFe 2 O 4 (NPs) have a smooth surface, and the agglomeration of NPs is also visible there.

SEM Analysis of ZnFe2O4 NPs
The surface morphology of the acquired ZnFe2O4 (NPs) was documented using a scanning electron microscope (FESEM) (Figure 3). The FESEM image indicated that the ZnFe2O4 (NPs) have a smooth surface, and the agglomeration of NPs is also visible there.

HRTEM Analysis of ZnFe 2 O 4 Nano Composite
The high-resolution transmission electron microscopy (HRTEM) images of ZnFe 2 O 4 (NPs) are shown ( Figure 4). The figure indicates that ZnFe 2 O 4 NPs are uniform and cylindrical. The average particle size was calculated using Image-J software and the particle size is ranged about 50 nm.

HRTEM Analysis of ZnFe2O4nanoComposite
The high-resolution transmission electron microscopy (HRTEM) images of ZnFe2O4 (NPs) are shown (Figure 4). The figure indicates that ZnFe2O4 NPs are uniform and cylindrical. The average particle size was calculated using Image-J software and the particle size is ranged about 50 nm.

EDS Analysis of ZnFe2O4 NPs
The elemental composition of ZnFe2O4 NPs was studied by energy-dispersive X-ray spectroscopy (EDS), as shown in Figure 5. The ZnFe2O4 NPs exhibit three elemental peaks-one for zinc element located at 1.1 keV, one for oxygen element located at 0.

Mass Spectra of Synthesized Compounds
The mass spectrum of 4a revealed a molecular ion peak at m/z 286, which is consistent with the formula weight (285). This result confirmed the identity of the structure

EDS Analysis of ZnFe 2 O 4 NPs
The elemental composition of ZnFe 2 O 4 NPs was studied by energy-dispersive X-ray spectroscopy (EDS), as shown in Figure 5. The ZnFe 2 O 4 NPs exhibit three elemental peaks-one for zinc element located at 1.1 keV, one for oxygen element located at 0.5 keV, and two for iron element located at 0.65 and 6.4 keV. From the EDS data, the weight ratio of Zn:Fe:O is around 43.91:13.97:42.12. The sample consists of only O, Fe, and Znelements.

HRTEM Analysis of ZnFe2O4nanoComposite
The high-resolution transmission electron microscopy (HRTEM) images of ZnFe2O4 (NPs) are shown (Figure 4). The figure indicates that ZnFe2O4 NPs are uniform and cylindrical. The average particle size was calculated using Image-J software and the particle size is ranged about 50 nm.

EDS Analysis of ZnFe2O4 NPs
The elemental composition of ZnFe2O4 NPs was studied by energy-dispersive X-ray spectroscopy (EDS), as shown in Figure 5. The ZnFe2O4 NPs exhibit three elemental peaks-one for zinc element located at 1.1 keV, one for oxygen element located at 0.5 keV, and two for iron element located at 0.65 and 6.4 keV. From the EDS data, the weight ratio of Zn:Fe:O is around 43.91:13.97:42.12. The sample consists of only O, Fe, andZnelements.

Mass Spectra of Synthesized Compounds
The mass spectrum of 4a revealed a molecular ion peak at m/z 286, which is consistent with the formula weight (285). This result confirmed the identity of the structure

Mass Spectra of Synthesized Compounds
The mass spectrum of 4a revealed a molecular ion peak at m/z 286, which is consistent with the formula weight (285). This result confirmed the identity of the structure of 4a. Similarly, the mass spectra of other compounds are also consistent with the proposed structures (for 4d, m/z = 321, 4g, m/z= 472 and 4h, m/z= 310) ( Figures S1-S4),

NMR Spectral Analysis
The 1 HNMR spectra of the compounds 7, 7-dimethyl-4-phenyl-2-thioxo-2, 3, 4, 6, 7, 8-hexahydro-1H-quinazolin-5-one from 5, 5-dimethyl cyclohexane-1, 3-diones (4a, 4d, 4g, 4h) ( Figures S5-S8) were assigned based on the observed chemical shift and relative intensities of the signals. The 1 HNMR spectra of the compounds displayed sharp singlets owing to the two -NH protons in each compound at 9.52-10.36 ppm. 1 HNMR spectral values of -NH groups in quinazolones nucleus showed down fields, namely,10.23, 10.13, 10.29, 10.34 ppm (halogens and cyano group). The -NH-groups of quinazolones containing electron donating group (EDG) showed the 1 HNMR values in the upfield region such as 9.58, 9.73, 9.54, 9.74, 9.72, 9.84, and 9.52 ppm and also the showed-OH group at 10.24 ppm. The derivatives were obtained by the cyclization with the thiourea added. The two methyl group protons of the compounds fell at 0.92-1.15 ppm. A singlet at 3.57 ppm and a broad singlet at 3.66 ppm for 4b and 4f accounts for protons of p-methoxy (-OCH 3 ) and dimethoxy (3,5-OCH 3 ) groups, respectively. In the case of 4c and 4d, the hydroxy (-OH) protons were observed as singlets at 9.33 and 10.24 ppm, respectively. A singlet appeared at 2.74 ppm due to the N-Me proton in 4d. The resonances due to aryl ring protons appeared in the range of 6.70-7.56 ppm. The quintets in 2.14-3.46 ppm and singlet around 2.40 ppm corresponded to methylene protons of dimedone ring.
The 13 CNMR spectra revealed the presence of the expected number of signals corresponding to different types of carbon atoms present in the compounds. The -OCH 3 group absorbs at 55.25 (4g) and 55.30 (4h) ppm slightly downfield to the methyl group carbon due to the deshielding of the directly attached electronegative oxygen atom. The spectra of the compounds exhibit a strong band at 169.8-174.2 ppm and are assigned as C=S group. The 13 CNMR display signals in the range 112.4-151.7 ppm, which has been assigned to the aromatic carbon atoms. The signals due to the C attached to the methyl group resonate at 141.4-147.8 ppm. The resonance arising from the carbon attached to the hydroxyl (4a and 4d) group is observed at 158.4 and 158.6 ppm, respectively. Values of downfield (195.2 ppm) compared with other groups (Figures S9-S12).

Discussion
Dimedone also called 5, 5-dimethylcyclohexane-1, 3-dione is a cyclic diketone, which is used as a key sample molecule for the synthesis of the various moiety in synthetic organic chemistry. These are white to light yellow crystals in color and also have other names such asdimedone, Cyclomethicone, 5, 5-dimethyl-1,3-cyclohexanedione, dimethyl-dihydro resorcinol, and Methone. The molecular formula is C 8 H 12 O 2 , and its molecular weight is 140.17968 g/mol with a melting point of 147-150 • C (420-423 K). It is stable under ambient conditions and soluble in organic solvents (CHCl 3 , CC 4 , toluene, etc.,) and in methanol, ethanol, and water. One-step reduction of dimedone to 3, 3-dimethylcyclohexanone compound with a yield of 69-73% (98-99% purity) by using Pd-catalyzed medium-pressure dimedone hydrogenation (1) in a solvent mixture of concentrated H 2 SO 4 and propionic acid [26] was made. Dimedone and its derivatives have been previously documented to have various biological properties such as anticarcinogenic [27], antioxidant [28], antihistamine [29], and anticoagulant [30]. A three-component one-pot reaction of dimedone, 1, 3-cyclohexanedione, aromatic aldehydes, and malononitrile in the presence of D, L-proline under solvent-free conditions at ambient temperature to produce 2-amino-3-cyano-4-aryl-7,7-dimethyl-5,6,7 8-tetrahydrobenzopyrans has been reported [31]. The reaction proceeded at room temperature clearly shows to provide good yields for the products (ae = 94%). An efficient one-pot synthesis of 4H-benzopyrans via a threecomponent cyclo condensation of malononitrile using CeCl 3 ·7H 2 O (10 mol percent) as a catalyst in a 1:2 mixture of water/ethanol under reflux conditions that yielded 70-94% within 1-2 h [32]. Sadehet al. (2017) [33] reported that in most organic transformations, dimedoneis a flexible and fascinating moiety. A wide variety of organic reactions, including one-pot multi-step syntheses, used the white to light yellow crystals of dimedone as a substrate. Dimedone has acidic properties in its methylene group, which is in harmony with its tautomericenol shape, making it possible to use them in various organic reactions. They are also used to evaluate the efficiency of some organic molecules, which have active pharmaceutical properties. Low-cost processing, ease of handling, low toxicity, easy accessibility, and moisture stability made it fascinating for use by synthetic organic chemists. Dimedone was concentrated in much of the reaction with a view to the media solvent. The temperature of the transformations in each segment has been subdivided, and this is used to achieve an organic transition based on green chemistry.
Leoa and Maryam (2018) [34]  @MSA shows that, due to the particle size of modified magnetite nanoparticles, the methane sulfonic acid layer attached to the nanoparticle surface is very thin because it is not larger than raw Fe 3 O 4 . These findings are in line with XRD trends [30].
Antibacterial activity was documented by Appaniet al. [35]. Electron withdrawing groups were demonstrated to have better behavior over aliphatic substituents among the various substituents on the C-2. Compounds with electron withdrawal substituents such as -Cl and-F showed increased activity over unsubstituted and electron releasing substituted moieties. As the most active compounds of the sequence, compounds 9a and 9h appeared to have the most potent activity against P. Vulgaris and B. Dimedone could be prepared from diethyl malonate and mesityl oxide, which is a safe compound with no or fewer hazards during usage. This dimedone is in equilibrium with its tautomericenol form in chloroform and the hydrogen bonding between the enolic structure results in the crystalline appearance. Dimedone and its analogs have been previously well documented with a wide spectrum of biological properties such as anticarcinogenic, antioxidant, antihistaminic, and anticoagulant [36].
The chemiluminescence property observed during the oxidation process belongs to 4-peroxydimedone radicals that are being synthesized from the first step of oxidation. Other applications of dimedone are colorimetry, crystallography, luminescence, and spectrophotometric analysis. Different types of reactions that include dimedone as a substrate have been presented and are classified based on the reaction media used. This is due to the importance of economical and green transformations in organic synthesis. The reaction could occur under solvent-free conditions, in aqueous media, and in the presence of various organic solvents. Some cases required heat to enhance them, and some others have taken place at room temperature. The above-discussed multiple properties of dimedone create a strong interest for utilizing them in different reactions by the synthetic chemists [37].

Materials
All the reagents, chemicals, and solvents (Merck, Mumbai, India) were procured and the melting points of the newly synthesized compounds were determined by using Agrawal 535 melting point apparatus. All the reactions were checked by thin-layer chromatography using ethyl acetate and n-hexane (5:5) performed on percolated silica gel (Merck, Mumbai, India). The 1 HNMR spectra of these compounds were recorded on BRUKER 400 MHz spectrometers and 13 CNMR were recorded on BRUKER 100 MHz using CDCl 3 as the solvent and Tetramethylsilane as an internal standard. The molecular weight of compounds was determined by mass spectrometry.
The precursors were dissolved in 50 mL ethylene glycol aliquot (C 2 H 6 O 2 ) and then agitated at room temperature for 2 h using a magnetic bead to form a homogenized aqueous solution (0.1 M). To evaporate all the material, the solution was dried for 6 h at 130 • C. Finally, the dry powder was annealed for crystallization at 500 • C for 1 h in the air.

Structural Characterization
The XRD profile at room temperature of the synthesized ZnFe 2 O 4 (NPs) was obtained. The crystal structure and phase purity of the sample were evaluated, and the crystalline size was determined using the Debye-Scherrer equation. ZnFe 2 O 4 (NPs) surface morphology was analyzed using the scanning electron microscope (SEM) (TESCAN, CZ/MIRA I LMH). Transmission electron microscope (TEM) (FEI, TECNAIG2TF20-ST) measured the particle size, and the elements present were analyzed by the energy dispersive x-ray analysis (EDS).

AntimicrobialAssays
Theantimicrobial activity of the titled compounds namely:7,7-dimethyl-4-phenyl-2thioxo-2,3,4,6,7,8-hexahydro-1H-quinazolin-5-ones and its derivatives have been in vitro screened with both bacterial and fungal strains: Gram-negative-Escherichia coli, Pseudomonas aeruginosa; Gram-positive-Bacillus subtilisin, Bacillus megaterium; Fungal strains-Aspergillusniger and Candida albicans. The synthesized compounds were laid using agar plates containing nutrient broth for bacteria in vitro activities [8][9][10][11]. The antibacterial streptomycin and fluconazole were used as standards for antibacterial and antifungal assays, respectively. Dimethyl sulfoxide (DMSO) was used as solvent control. The antimicrobial inhibitions of test compounds were expressed as a zone of inhibition in standard units (mm). This marked antibacterial activity may be due to the presence of high hydrophobic content of this family of compounds and the quinazoline ring system. The compounds containing the quinazalone segment are more active against bacteria due to the strong interaction of the latter with the agar medium; this hinders their diffusion in the agar medium.