Retracted Article: Design of 1-methylimidazolium tricyanomethanide as the first nanostructured molten salt and its catalytic application in the condensation reaction of various aromatic aldehydes, amides and β-naphthol compared with tin dioxide nanoparticles

Abstract

1-Methylimidazolium tricyanomethanide {[HMIM]C(CN)₃} as a novel, green and nano molten salt catalyst was designed and fully identified by IR, ¹H NMR, ¹³C NMR, mass, thermal gravimetric (TG), derivative thermal gravimetric (DTG), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The catalytic application of {[HMIM]C(CN)₃} for the one-pot three-component condensation reaction of various aromatic aldehydes, amides and β-naphthol was studied through the preparation of 1-amidoalkyl-2-naphthols at room temperature under solvent-free conditions in comparison with nano SnO₂. In the presented investigations, some products were produced and reported for the first time.

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Introduction

Room temperature molten salts (RTMSs), termed as room temperature ionic liquids (RTILs), which are immiscible or only partially miscible with water, have been revealed to be promising as replacements for common organic solvents. Molten salts (MSs) have important potential as electrolyte materials. The molten salts, lately called ionic liquids, have attracted much attention in various scientific fields.¹ Generally, MSs refer to inorganic MSs and RTILs to organic onium salts molten below 100 °C. MSs are an attractive class of liquids due to their incomparable ionic interactions and their varied number of scientific usages.^2,3 Molten salts and ILs can be applied as GC stationary phases for both packed and open-tubular columns.^4–7

The nano sciences have lately developed as a main study path of our modern society, resulting from a continuing attempt to miniaturize at the nano scale operations that currently use microsystems. To this end, it is well known that the bottom-up method should now replace the classic top-down one, a strategic move that is common to various areas of the nano sciences including sensing, medicine, optoelectronics and catalysis.⁸ More lately, there have been developments towards biological and medical usages of nanoparticles. The entrapment of anticancer drugs in nanoparticles, and the decoration of the particles with molecular ligands for the targeting of cancerous cells, offers the outlook of more efficient cancer treatment with reduced side-effects.⁹ A different strategy for the use of nanoparticles in cancer therapy is photo-thermal tumor ablation.¹⁰ Tin oxide (SnO₂) is a significant material because of its properties, for example low operating temperature, strong physical and chemical interaction with adsorbed species, high degree of transparency in the visible spectrum and strong thermal stability in air (up to 500 °C).¹¹ Tin dioxide, an n-type semiconductor with a broad band gap (E_g = 3.6 eV, at 300 K), is a main functional material that has been widely applied for optoelectronic devices.¹² Tin oxide has received little consideration in the catalysis field compared to other metal oxides,¹³ although tin oxide supported catalysts have been described to be active for oxidative dehydrogenation of propane, CO oxidation and esterification reactions.¹⁴

Multi-component reactions (MCRs) for making heterocyclic compounds are influential tools in the drug-discovery process as they can offer the appropriate synthesis of libraries of drug-like compounds in a single procedure.¹⁵ The one-pot multi-component condensation reaction between aromatic aldehydes with β-naphthol and amide derivatives has been offered as a suitable synthetic method toward 1-amidoalkyl-2-naphthols.^16–23 1-Amidoalkyl-2-naphthols are imperative intermediates which can be effortlessly transformed into biologically active aminoalkyl-naphthol derivatives via amide hydrolysis. The hypertensive and bradycardiac properties of these compounds have been explored.^24,25 Several catalysts have been applied to achieve this reaction, including boric acid,¹⁶ trityl chloride,¹⁷ saccharin sulfonic acid (SASA),¹⁸ [Et₃N–SO₃H]Cl,¹⁹ nano-S (S8-NP),²⁰ [Msim]Cl, [Dsim]Cl, [Msim]AlCl₄,²¹ Fe(HSO₄)₃ (ref. 22) and [2-MPyH]OTf.²³

In this work, we have prepared a novel molten salt and catalyst, namely 1-methylimidazolium tricyanomethanide {[HMIM]C(CN)₃} (Scheme 1) and used it for the synthesis of 1-amidoalkyl-2-naphthol derivatives under solvent-free reaction conditions (Scheme 2). Also, to compare the catalytic activity of {[HMIM]C(CN)₃} at the nano scale, SnO₂ nanoparticles were applied instead of it in the synthesis of 1-amidoalkyl-2-naphthol derivatives in similar conditions.

Scheme 1 The synthesis of 1-methylimidazolium tricyanomethanide {[HMIM]C(CN)₃} as a nano molten salt catalyst.

Scheme 2 The synthesis of 1-amidoalkyl-2-naphthol derivatives in the presence of {[HMIM]C(CN)₃} as a nano molten salt (a) and SnO₂ nanoparticles (b) as green nano catalytic systems.

Results and discussion

Characterization of 1-methylimidazolium tricyanomethanide {[HMIM]C(CN)₃} as a nano molten salt catalyst

The structure of 1-methylimidazolium tricyanomethanide as a novel nano molten salt catalyst was studied and identified by FT-IR, ¹H NMR, ¹³C NMR, mass, TG, DTG, XRD, SEM and TEM analyses.

The IR spectrum of the nano molten salt displayed a special peak at 3417 cm⁻¹ which can be related to the N–H stretching group on the imidazolium ring. Furthermore, the two peaks detected at 2170 cm⁻¹ and 2081 cm⁻¹ can be related to vibrational modes of the –CN bonds (Fig. 1).

Fig. 1 The IR spectra of 1-methylimidazolium tricyanomethanide (a), tricyanomethane (b) and 1-methylimidazole (c).

Additionally, the ¹H NMR and ¹³C NMR spectra of the 1-methylimidazolium tricyanomethanide in DMSO-d₆ are demonstrated in Fig. 2 and 3, respectively. As Fig. 2 and 3 indicate, the main peak of the ¹H NMR spectrum of the nano molten salt catalyst is related to the N–H group on the methyl imidazolium ring of {[HMIM]C(CN)₃} which is observed at δ = 11.95 ppm. The peak related to the methyl group appears at 2.5 ppm and the peaks related to the imidazolium ring are depicted at 7.0 and 7.8 ppm respectively. Also, the important peak of the ¹³C NMR spectrum of the nano molten salt catalyst is linked to the –CN group on the tricyanomethanide anion which is detected at δ = 74.8 ppm and the corresponding peaks at 119.7 and 134.8 ppm are related to carbons of the imidazolium ring.

Fig. 2 The ¹H NMR spectrum of 1-methylimidazolium tricyanomethanide as a novel nano molten salt catalyst.

Fig. 3 The ¹³C NMR spectrum of 1-methylimidazolium tricyanomethanide as a novel nano molten salt catalyst.

Thermal gravimetric (TG) and derivative thermal gravimetric (DTG) analyses of 1-methylimidazolium tricyanomethanide were investigated at a range of 25 to 600 °C, with a temperature increase rate of 10 °C min⁻¹ in a nitrogen atmosphere. The results are depicted in Fig. 4 and 5. The thermal gravimetric (TG) and derivative thermal gravimetric (DTG) analysis of the nano molten salt catalyst showed weight losses in one step, and decomposition after 320 °C.

Fig. 4 The thermal gravimetric (TG) analysis of the nano molten salt catalyst.

Fig. 5 The derivative thermal gravimetric (DTG) analysis of the nano molten salt catalyst.

The size, shape and morphology of 1-methylimidazolium tricyanomethanide as the nano molten salt catalyst were studied by X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) imaging demonstrations. XRD patterns of the catalyst {[HMIM]C(CN)₃} were considered in a domain of 10–90 degrees (Fig. 6). As it is shown in Fig. 6, the XRD patterns showed diffraction lines of a highly crystalline nature at 2θ ≈ 27.20°, 38.90° and 50.90°. Peak width (FWHM), size and inter planar distance related to the XRD pattern of {[HMIM]C(CN)₃} were investigated in the 27.20° to 50.90° range and the obtained results are summarized in Table 1. For example, assignments for the highest diffraction line at 27.20° with an FWHM of 0.26 gave a crystallite size of the catalyst of ca. 31.44 nm via the Scherrer equation [D = Kλ/(β cos θ)] (where D is the crystallite size, K is the shape factor, corresponding to 0.9, λ is the X-ray wavelength, β is the full width at half maximum of the diffraction peak, and θ is the Bragg diffraction angle in degrees). An inter planar distance of 0.327462 nm (with the similar highest diffraction line at 27.20°) was calculated via the Bragg equation: dhkl = λ/(2 sin θ) (λ: Cu radiation (0.154178 nm)). The obtained crystallite sizes from various diffraction lines using the Scherrer equation were found to be in the nanometer range (29.06–47.31 nm), which is principally in a good agreement with the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses (Fig. 7 and 8).

Fig. 6 The X-ray diffraction (XRD) pattern of 1-methylimidazolium tricyanomethanide as a nano molten salt catalyst.

Table 1 X-ray diffraction (XRD) data for 1-methylimidazolium tricyanomethanide as a nano molten salt catalyst

Entry	2θ	Peak width [FWHM] (degrees)	Size (nm)	Inter planar distance (nm)
1	27.20	0.26	31.44	0.327462
2	38.90	0.29	29.06	0.231242
3	50.90	0.17	47.31	0.179181

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Fig. 7 Scanning electron microscopy (SEM) of 1-methylimidazolium tricyanomethanide as a nano molten salt catalyst.

Fig. 8 Transmission electron microscopy (TEM) of 1-methylimidazolium tricyanomethanide as a nano molten salt catalyst.

Characterization of tin dioxide (SnO₂) as a nanoparticle catalyst

The SnO₂ nanoparticles (NPs) were synthesized and investigated according to previous literature.^13,14,26,27 The size, shape and morphology of the SnO₂ NPs were investigated using XRD patterns, and FE-SEM and TEM imaging approaches. The X-ray diffraction (XRD) pattern of the SnO₂ NPs is presented in Fig. 9. Peaks at 2θ values of 26.50°, 33.75°, 37.80°, 51.60°, and 54.85° can be observed. The SnO₂ product displays a tetragonal structure. With respect to the intensity ratio of the major peak detected at 2θ equal to 51.60°, the crystalline structure of the catalyst can noticeably be recognized. The average crystallite size was proposed using the line width of the diffraction peak in radians (β), the Bragg angle in degrees (θ), and the Debye–Scherrer equation (Fig. 9 and Table 2). The average size of the catalyst consequently achieved from this equation was established to be in the nanometer range (28.73–36.66 nm), which is basically in agreement with the FE-SEM and TEM analyses (Fig. 10 and Fig. 11).

Fig. 9 The X-ray diffraction (XRD) pattern of the SnO₂ NP catalyst.

Table 2 X-ray diffraction (XRD) data for the SnO₂ NP catalyst

Entry	2θ	Peak width [FWHM] (degree)	Size (nm)	Inter planar distance (nm)
1	26.50	0.24	33.88	0.336245
2	33.75	0.25	32.92	0.265517
3	37.80	0.29	28.73	0.237654
4	51.60	0.24	36.66	0.177012
5	54.85	0.30	30.02	0.167028

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Fig. 10 Field emission scanning electron microscopy (FE-SEM) of the SnO₂ NP catalyst.

Fig. 11 Transmission electron microscopy (TEM) of the SnO₂ NP catalyst.

Application of 1-methylimidazolium tricyanomethanide nano MS and SnO₂ NPs as a catalyst

At first, to optimize the reaction conditions, the condensation reaction of naphthalene-1-carbaldehyde, β-naphthol and acetamide was selected as a model and different amounts of nano catalyst in the range of 25–125 °C were tested in it under solvent-free conditions (Table 3). As shown in Table 3, the best results were attained when the reaction was achieved in the presence of 1 mol% of the nano molten salt and SnO₂ nanoparticles at room temperature (Table 3, entry 5). No improvement was observed in the yield of the reaction by increasing the amount of the nano catalyst and the temperature (Table 3, entries 6–13). Table 3 clearly demonstrates that in the absence of the nano catalyst, the product was not prepared. A slight excess of the amide was established to be favorable and hence the molar ratio of β-naphthol and aromatic aldehyde to amide considered was 1 : 1 : 1.2.

Table 3 Result of the amount of the catalyst and temperature on the condensation reaction of naphthalene-1-carbaldehyde, β-naphthol and acetamide under solvent-free conditions

Entry	Amount of catalyst (mol%)	Reaction temperature (°C)	Reaction time (min)		Yield (%)
			Molten salt	Nano SnO2	Molten salt	Nano SnO2
1	—	r.t.	75	75	—	—
2	—	100	75	75	—	—
3	0.5	r.t.	60	60	37	25
4	0.5	100	60	60	37	25
5	1	r.t.	7	17	96	87
6	1	50	7	17	96	87
7	1	75	7	17	96	87
8	1	100	7	17	96	87
9	1	125	7	17	93	85
10	2	r.t.	7	17	96	87
11	2	100	7	17	96	87
12	5	r.t.	10	20	95	86
13	5	100	10	20	95	86

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To compare the effect of the solution to solvent-free conditions, a mixture of naphthalene-1-carbaldehyde, β-naphthol and acetamide as a model reaction, in the presence of 1 mol% of the nano molten salt or nano SnO₂ as a catalyst in several solvents such as H₂O, C₂H₅OH, CH₃CN, CH₃CO₂Et, CH₂Cl₂ and toluene, was considered at room temperature. The results are depicted in Table 4. As it is shown in Table 4, the solvent-free condition was the best condition for this reaction.

Table 4 The effect of different solvents on the reaction of naphthalene-1-carbaldehyde, β-naphthol and acetamide catalyzed by the nano molten salt (1 mol%) or SnO₂ NPs (1 mol%) at room temperature

Entry	Solvent	Reaction time (min)		Yield (%)
		Molten salt	Nano SnO2	Molten salt	Nano SnO2
1	Solvent-free	7	17	96	87
2	H2O	30	30	25	15
3	C2H5OH	30	30	25	25
4	CH3CN	30	30	20	20
5	CH3CO2Et	60	60	10	10
6	CH2Cl2	75	75	—	—
7	Toluene	120	120	—	—

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After optimization of the reaction conditions, to explore the efficiency and the scope of the presented protocol, several 1-amidoalkyl-2-naphthol derivatives were synthesized by the three-component condensation reaction of various aromatic aldehydes, β-naphthol and different amides in the presence of a catalytic amount of 1-methylimidazolium tricyanomethanide {[HMIM]C(CN)₃} as a nano molten salt catalyst or SnO₂ nanoparticles as a catalyst under solvent-free reaction conditions. The results are represented in Table 5. The effect of substituents on the aromatic ring indicated strong effects in terms of yield under these reaction conditions. All aromatic aldehydes including benzaldehyde and aldehydes containing electron-donating substituents and electron-withdrawing substituents on their aromatic ring afforded the related products in high to excellent yields in short reaction times. The reaction times of aromatic aldehydes with electron-withdrawing groups were much faster than for those with electron-donating groups. Also, amide derivatives experienced similarly good results in the transformation. Moreover, under these reaction conditions, acetamide reacted faster than benzamide and urea. Particularly, the obtained results displayed that the nano molten salt (a) was more successful as a catalyst than the nanoparticles (b) under these reaction conditions.

Table 5 Synthesis of 1-amidoalkyl-2-naphthol derivatives using 1-methylimidazolium tricyanomethanide nano molten salt (1 mol%) or SnO₂ nanoparticles (1 mol%) as a catalyst

Entry	Aldehyde	R′	Time (min)		Yield (%)		M.p (°C) [Ref.]
			Molten salt	Nano SnO2	Molten salt	Nano SnO2
1	Benzaldehyde	NH2	25	35	90	81	177–179 [23]
2	4-Nitrobenzaldehyde	NH2	15	25	94	85	200–202 [23]
3	4-Chlorobenzaldehyde	NH2	20	29	92	83	161–163 [23]
4	2,5-Dimethoxybenzaldehyde	NH2	23	31	91	83	206–208
5	Furfural	NH2	25	35	90	80	140–142 [23]
6	Thiophene-2-carbaldehyde	NH2	25	35	90	80	152–154 [23]
7	Naphthalene-1-carbaldehyde	NH2	18	27	93	84	195–197 [23]
8	α-Methylcinnamaldehyde	NH2	30	35	90	80	279–281
9	4-Nitrobenzaldehyde	CH3	5	15	97	88	248–250 [23]
10	4-Chlorobenzaldehyde	CH3	10	20	95	85	258–260 [23]
11	2,5-Dimethoxybenzaldehyde	CH3	12	20	95	85	280–282 [23]
12	Naphthalene-1-carbaldehyde	CH3	7	17	96	87	265–267
13	Cinnamaldehyde	CH3	15	25	93	83	230–232 [16]
14	Naphthalene-2-carbaldehyde	CH3	7	17	96	86	256–258 [20]
15	α-Methylcinnamaldehyde	CH3	20	27	92	83	223–225
16	Biphenyl-4-carbaldehyde	CH3	8	15	96	88	244–246
17	4-Nitribenzaldeyhe	Ph	8	20	96	87	253–255 [23]
18	4-Chlorobenzaldehyde	Ph	15	25	94	83	205–207 [23]
19	2,5-Dimethoxybenzaldehyde	Ph	18	25	93	83	271–273
20	Naphthalene-1-carbaldehyde	Ph	10	23	95	85	293–295
21	Cinnamaldehyde	Ph	18	30	92	82	201–203
22	Naphthalene-2-carbaldehyde	Ph	10	23	95	85	264–266
23	α-Methylcinnamaldehyde	Ph	25	30	92	81	244–246
24	Biphenyl-4-carbaldehyde	Ph	10	30	96	86	281–283

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In Scheme 3, we suggest a possible mechanism for the synthesis of 1-amidoalkyl-2-naphthol derivatives in the presence of {[HMIM]C(CN)₃} as a nano molten salt catalyst or SnO₂ nanoparticles as a catalyst. The reaction of aromatic aldehydes with β-naphthol in the presence of the nano catalyst is predicted to generate ortho-quinone methides (o-QMs). The prepared o-QMs have been reacted with amide derivatives to give 1-amidoalkyl-2-naphthol derivatives. A practical description for this result can be given by considering the nucleophilic addition of the amide to the o-QM intermediate and lastly the desired product was obtained after aromatization.^{17–22,28,29}

Scheme 3 Proposed mechanism for the synthesis of 1-amidoalkyl-2-naphthol derivatives in the presence of {[HMIM]C(CN)₃} as a nano MS or SnO₂ NPs as a catalyst.

Furthermore, the reusability of the catalyst was investigated for the condensation reaction between naphthalene-1-carbaldehyde, β-naphthol and acetamide. After completion of the reaction, ethyl acetate was added to the reaction mixture and stirred and heated to separate the product and the remaining starting materials from the catalyst. This solution was washed with water to separate the catalyst from the other materials (the product and starting materials are soluble in hot ethyl acetate and the nano molten salt catalyst is soluble in water). The aqueous layer was decanted and separated and the catalyst was reused for an alternative reaction after removing the water. The catalytic activity of the catalyst was restored within the limits of the experimental error for four continuous runs (Fig. 12). For recycling of the SnO₂ NPs, at the end of the reaction, warm ethyl acetate was added to the reaction mixture, stirred and heated to separate the product and the remaining starting materials from the catalyst. Afterward, the obtained mixture was centrifuged to separate the catalyst (the SnO₂ NP catalyst is insoluble in ethyl acetate and the reaction mixture is soluble in ethyl acetate). The structure of the reused {[HMIM]C(CN)₃} was also confirmed by IR, ¹H NMR and ¹³C NMR spectra after its application in the reaction. These presented spectra are in very good accordance with the spectra of the fresh catalyst (Fig. S3–S5†). Moreover, the size and morphology of the reused catalysts were studied by SEM and TEM analyses. These studies showed that the catalysts recovered were nano sized (Fig. S6 and S7†).

Fig. 12 Reusability of the nano MS catalyst at 7 minutes and NP catalyst at 17 minutes.

To compare the efficiency of our catalyst with some reported catalysts for the synthesis of 1-amidoalkyl-2-naphthols, we have tabulated the results of these catalysts to perform the condensation of 4-chlorobenzaldehyde, β-naphthol and acetamide in Table 6. As Table 6 indicates, {[HMIM]C(CN)₃} has remarkably improved the synthesis of 1-amidoalkyl-2-naphthols in different aspects (reaction time, yield and turn-over frequency (TOF)). The TOF values were calculated using the equation TOF = yield (%)/[time (min) × catalyst amount (mol%)]. The reaction times were shorter and the yields and TOFs were higher when our catalysts were utilized.

Table 6 Comparison of the results of the condensation reaction of 4-chlorobenzaldehyde, β-naphthol and acetamide catalyzed by {[HMIM]C(CN)₃} with those obtained by recently reported catalysts

Reaction conditions	Catalyst loading	Time (min)	Yield^a (%)	TOF^b (min^−1)	Ref.
a Isolated yield.b Turn-over frequency.c Our work.
Cu1.5PW12O40, 100 °C	2 mol%	90	78	0.433	30a
Fe(HSO4)3, 85 °C	5 mol%	45	88	0.125	22
Sulfamic acid, ultrasound, 28–30 °C	51.5 mol%	120	92	0.015	30b
I2, r.t.	5 mol%	690	90	0.026	30c
Cyanuric chloride, 100 °C	10 mol%	10	90	0.900	30d
H3PW12O40, 100 °C	2 mol%	80	88	0.550	30e
4-(1-Imidazolium)butane sulfonate, 80 °C	10 mol%	120	85	0.070	30f
N-(4-Sulfonic acid)butyl triethylammonium hydrogensulfate, 120 °C	5 mol%	10	85	1.7	30g
{[HMIM]C(CN)3}, r.t.	1 mol%	10	95	9.5	—^c

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The efficacy of SnO₂ nanoparticles in the synthesis of 1-amidoalkyl-2-naphthols was also studied in comparison with some other dioxide catalysts such as CeO₂, PbO₂, TiO₂, Ag–TiO₂ and ZrO₂. For this purpose, the reaction of 4-chlorobenzaldehyde, β-naphthol and acetamide was investigated in the presence of these catalysts (Table 7). As shown in Table 7, the synthesis of 1-amidoalkyl-2-naphthols in the presence of SnO₂ NPs as a catalyst was the best condition (dioxide catalyst) for this reaction.

Table 7 Comparison of the synthesis of 1-amidoalkyl-2-naphthols using different dioxide catalysts under solvent-free conditions at room temperature^a

Dioxide	Catalyst loading	Time (min)	Yield^b (%)
a Reaction conditions: 4-chlorobenzaldehyde (1 mmol), β-naphthol (1 mmol), and acetamide (1.2 mmol).b Isolated yields.
Nano-SnO2	1 mol%	20	85
CeO2	1 mol%	60	15
PbO2	2 mol%	120	——
Nano-TiO2	1 mol%	30	30
Nano-Ag–TiO2	2 mol%	60	5
ZrO2	1 mol%	30	45

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Conclusions

In summary, a novel, green and efficient nano molten salt catalyst, namely 1-methyl imidazolium tricyanomethanide {[HMIM]C(CN)₃}, was designed and completely characterized by IR, ¹H NMR, ¹³C NMR, mass, thermal gravimetric (TG), derivative thermal gravimetric (DTG), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. The catalytic application of {[HMIM]C(CN)₃} was studied in the synthesis of 1-amidoalkyl-2-naphthol derivatives for the three-component condensation reaction of various aromatic aldehydes, β-naphthol and several amides at room temperature under solvent-free conditions. Moreover, to compare the catalytic activity of the catalyst under similar conditions, nano SnO₂ was used instead of {[HMIM]C(CN)₃} in the synthesis of 1-amidoalkyl-2-naphthol derivatives. Generally, the achieved results showed that the {[HMIM]C(CN)₃} nano molten salt was more successful than SnO₂ nanoparticles as a catalyst (due to the formation of products with higher yields and a shorter reaction time, {[HMIM]C(CN)₃} as a nano molten salt catalyst is better than SnO₂ nanoparticles as a catalyst). Additional studies indicated that the nano molten salt basicity plays a main role in the dual-catalyzed reactions. The various important advantages of this study are a relatively short reaction time, high yield, cleaner reaction profile, low cost, simplicity of product isolation, reusability of the nano catalyst and compliance with the green chemistry protocols.

Experimental

General procedure for the preparation of the nano molten salt catalyst

1-Methylimidazolium tricyanomethanide. 1-Methylimidazole (3 mmol: 0.246 g) was added to 5 mL of an aqueous solution of tricyanomethane (3 mmol: 0.273 g) and stirred at room temperature for 60 minutes. Subsequently the solvent was removed by distillation under reduced pressure; the white residue was dried under vacuum at 100 °C for 3 h. A pale pink solid formed which was filtered, washed with diethyl ether three times, and then dried under vacuum (a pale pink solid was insoluble in diethyl ether) and was characterized by IR, ¹H NMR, ¹³C NMR, mass, thermal gravimetric (TG), derivative thermal gravimetric (DTG), X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses and melting-point determination (Scheme 1).

1-Methylimidazolium tricyanomethanide {[HMIM]C(CN)₃}. M.p: >300 °C; yield: 96% (0.498 g); spectral data: IR (KBr): ν 3417, 2925, 2170, 2081, 1631, 1574, 1455 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.63 (s, 3H, –CH₃), 7.00 (s, 2H, –CH); 7.63 (s, 1H, –CH), 11.95 (brs, 1H, –NH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 46.4, 67.2, 74.8, 119.8, 134.9, 160.2 ppm; MS: m/z = 173 [M]⁺, 174 [M + H]⁺.

General procedure for the preparation of the tin dioxide nanoparticle catalyst

SnO₂ NPs were prepared by dissolving 0.1 M: 2 g stannous chloride dehydrate (SnCl₂·2H₂O) in 50 mL distilled water. After complete dissolution, ammonia solution was added drop-wise to the above solution and stirred. The resulting gels were filtered and dried at 80 °C for 24 h in order to remove water. To conclude, the SnO₂ NPs were formed at 600 °C for 2 h and were considered using X-ray diffraction (XRD) patterns, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) analyses.^13,14,26,27

General procedure for the synthesis of 1-amidoalkyl-2-naphthol derivatives

To a mixture of aromatic aldehydes (1 mmol), β-naphthol (1 mmol) and amide derivatives (1.2 mmol) in a round bottom flask connected to a condenser, 1 mol% of {[HMIM]C(CN)₃} nano molten salt or SnO₂ nanoparticles was added as the catalyst and the resulting mixture was firstly stirred magnetically under solvent-free conditions at room temperature for an appropriate time. After completion of the reaction, as monitored by TLC (n-hexane/ethyl acetate: 5/1), ethyl acetate (10 mL) was added to the reaction mixture, stirred and refluxed for 5 min, and then washed with water (10 mL) and decanted to separate the catalyst from the other materials (the reaction mixture was soluble in hot ethyl acetate and the nano molten salt catalyst was soluble in water). The aqueous layer was decanted and separated, and after removing the water the remaining catalyst was used for an alternative reaction. The solvent of the organic layer was removed and the crude product was purified by recrystallization from ethanol (95%). Note: in another procedure, for the recycling of SnO₂ NPs, at the end of the reaction, warm ethyl acetate was added to the reaction mixture and centrifuged to separate the product and starting materials from the catalyst the (SnO₂ NP catalyst is insoluble in ethyl acetate). In this work, the nano molten salt or SnO₂ nanoparticles as a catalyst was recycled and reused four times without a significant loss of its catalytic activity.

Spectral data analysis of compounds

1-((2-Hydroxynaphthalen-1-yl)(4-nitrophenyl)methyl)urea (Table 3, entry 2). Yellow solid; m.p: 200–202 °C; yield: nano molten salt: 94%, nano SnO₂: 85%; IR (KBr): ν 3484, 3457, 3316, 3074, 1655, 1604, 1516, 1348 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 6.94 (brs, 1H, –OH), 7.48 (brs, 2H, –NH₂), 7.61 (d, 1H, J = 9.2 Hz, –CH aliphatic), 7.68 (d, 2H, J = 7.2 Hz, ArH), 7.94 (d, 2H, J = 8.8 Hz, ArH), 7.99 (t, 4H, J = 9.0 Hz, ArH), 8.04 (d, 2H, J = 8.8 Hz, ArH), 8.71 (d, 1H, J = 8.4 Hz, –NH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 36.7, 116.6, 118.2, 123.6, 124.2, 125.2, 127.7, 129.2, 129.5, 130.1, 131.1, 131.2, 146.3, 148.5, 153.1, 196.3 ppm.

1-((2,5-Dimethoxyphenyl)(2-hydroxynaphthalen-1-yl)methyl)urea (Table 3, entry 4). Pale yellow solid; m.p: 206–208 °C; yield: nano molten salt: 91%, nano SnO₂: 83%; IR (KBr): ν 3493, 3386, 3082, 2994, 1662, 1529, 1495, 1271 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.50 (s, 3H, –OCH₃), 3.66 (s, 3H, –OCH₃), 4.30 (brs, 2H, –NH₂), 6.75 (s, 1H, ArH), 6.81 (d, 1H, J = 9.2 Hz, –CH aliphatic), 7.13 (d, 2H, J = 8.4 Hz, ArH), 7.19 (d, 1H, J = 8.4 Hz, ArH), 7.27 (t, 1H, J = 7.4 Hz, ArH), 7.44 (t, 1H, J = 7.6 Hz, ArH), 7.69 (d, 1H, J = 8.8 Hz, ArH), 7.76 (d, 1H, J = 8.0 Hz, ArH), 8.18 (d, 1H, J = 8.8 Hz, ArH), 8.35 (d, 1H, J = 8.4 Hz, –NH), 9.83 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 44.9, 55.7, 56.4, 111.5, 112.3, 116.3, 119.1, 119.3, 122.6, 123.8, 126.3, 128.6, 128.7, 129.2, 132.1, 133.0, 151.2, 153.2, 153.7, 168.8 ppm; MS: m/z = 352 [M]⁺.

1-((2-Hydroxynaphthalen-1-yl)(naphthalen-1-yl)methyl)urea (Table 3, entry 7). Pale yellow solid; m.p: 195–197 °C; yield: nano molten salt: 93%, nano SnO₂: 84%; IR (KBr): ν 3432, 3333, 3220, 2974, 1650, 1629, 1538, 1515 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 5.40 (brs, 2H, –NH₂), 5.70 (brs, 1H, –OH), 7.04 (d, 1H, J = 8.4 Hz, –CH aliphatic), 7.26 (d, 2H, J = 8.8 Hz, ArH), 7.35 (t, 1H, J = 7.4 Hz, ArH), 7.49 (t, 2H, J = 9.9 Hz, ArH), 7.54 (d, 2H, J = 6.4 Hz, ArH), 7.77 (d, 2H, J = 8.8 Hz, ArH), 7.80 (d, 2H, J = 8.4 Hz, ArH), 7.95 (t, 2H, J = 7.0 Hz, ArH), 8.23 (d, 1H, J = 7.6 Hz, –NH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 47.8, 119.2, 119.8, 122.8, 123.0, 124.3, 125.2, 125.4, 125.5, 125.8, 126.0, 126.3, 126.8, 127.7, 128.9, 129.0, 129.1, 129.5, 131.4, 133.0, 134.0, 158.4 ppm.

1-(1-(2-Hydroxynaphthalen-1-yl)-2-methyl-3-phenylallyl)urea (Table 3, entry 8). Yellow solid; m.p: 279–281 °C; yield: nano molten salt: 90%, nano SnO₂: 80%; IR (KBr): ν 3513, 3383, 3271, 3064, 2969, 1659, 1600, 1230 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 1.11 (s, 3H, –CH₃), 4.53 (s, 1H, –CH), 5.41 (brs, 1H, –OH), 5.53 (d, 1H, J = 5.2 Hz, –CH aliphatic), 5.85 (brs, 2H, –NH₂), 6.96 (d, 1H, J = 5.0 Hz, ArH), 7.12 (t, 1H, J = 7.2 Hz, ArH), 7.20 (t, 2H, J = 7.4 Hz, ArH), 7.30 (d, 5H, J = 5.8 Hz, ArH), 7.42 (d, 1H, J = 6.4 Hz, –NH), 7.83 (t, 2H, J = 9.0 Hz, ArH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 13.5, 46.2, 75.9, 112.5, 119.0, 123.4, 123.5, 126.9, 128.7, 128.9, 129.0, 129.4, 129.6, 133.2, 146.2, 152.6, 157.8 ppm; MS: m/z = 332 [M]⁺.

N-((4-Chlorophenyl)(2-hydroxynaphthalen-1-yl)methyl)acetamide (Table 3, entry 10). White solid; m.p: 258–260 °C; yield: nano molten salt: 95%, nano SnO₂: 85%; IR (KBr): ν 3392, 3053, 2965, 1638, 1623, 1580, 1515, 1244 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.30 (s, 3H, –CH₃), 6.76 (d, 1H, J = 7.2 Hz, –CH aliphatic), 7.22 (brs, 1H, –OH), 7.47 (d, 2H, J = 7.2 Hz, ArH), 7.58 (d, 2H, J = 9.2 Hz, ArH), 7.66 (t, 4H, J = 8.4 Hz, ArH), 7.95 (d, 2H, J = 8.8 Hz, ArH), 8.68 (d, 1H, J = 8.4 Hz, –NH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 36.2, 47.5, 118.1, 123.8, 125.1, 127.5, 128.7, 128.8, 128.9, 129.0, 129.1, 129.2, 129.7, 130.1, 131.1, 131.2, 131.4, 144.9, 148.4, 191.5 ppm.

N-((2-Hydroxynaphthalen-1-yl)(naphthalen-1-yl)methyl)acetamide (Table 3, entry 12). White solid; m.p: 265–267 °C; yield: nano molten salt: 96%, nano SnO₂: 87%; IR (KBr): ν 3413, 3057, 3006, 2937, 1647, 1628, 1582, 1512, 1332 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 1.93 (s, 3H, –CH₃), 7.25 (d, 2H, J = 8.8 Hz, ArH), 7.34 (t, 1H, J = 7.4 Hz, ArH), 7.43 (d, 1H, J = 8.0 Hz, –CH aliphatic), 7.51 (t, 4H, J = 6.8 Hz, ArH), 7.64 (d, 1H, J = 8.0 Hz, ArH), 7.78 (d, 1H, J = 8.8 Hz, ArH), 7.83 (d, 1H, J = 8.8 Hz, ArH), 7.94 (d, 1H, J = 9.6 Hz, ArH), 7.99 (d, 1H, J = 8.4 Hz, ArH), 8.06 (d, 1H, J = 9.2 Hz, ArH), 8.74 (d, 1H, J = 8.0 Hz, –NH), 10.05 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 23.0, 47.4, 118.7, 119.1, 122.8, 123.6, 123.9, 125.6, 125.7, 125.9, 126.5, 126.7, 128.0, 129.0, 129.1, 129.2, 129.7, 131.5, 133.3, 134.0, 137.8, 153.8, 169.0 ppm; MS: m/z = 341 [M]⁺.

N-(1-(2-Hydroxynaphthalen-1-yl)-3-phenylallyl)acetamide (Table 3, entry 13). Yellow solid; m.p: 230–232 °C; yield: nano molten salt: 93%, nano SnO₂: 83%; IR (KBr): ν 3417, 3175, 3065, 3023, 1657, 1642, 1515, 1439, 1270 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 1.90 (s, 3H, –CH₃), 6.49 (d, 1H, J = 7.8 Hz, ArH), 6.60 (t, 1H, J = 7.4 Hz, –CH aliphatic), 6.67 (d, 1H, J = 5.6 Hz, ArH), 7.22 (t, 2H, J = 8.4 Hz, ArH), 7.31 (t, 3H, J = 7.2 Hz, ArH), 7.36 (d, 2H, J = 8.4 Hz, ArH), 7.47 (t, 1H, J = 7.2 Hz, ArH), 7.75 (d, 1H, J = 8.8 Hz, ArH), 7.81 (d, 1H, J = 7.6 Hz, ArH), 8.14 (d, 1H, J = 8.4 Hz, ArH), 8.40 (d, 1H, J = 7.6 Hz, –NH), 10.04 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 23.1, 47.8, 118.8, 119.0, 122.9, 126.5, 126.7, 127.7, 128.9, 129.0, 129.1, 129.2, 129.5, 131.1, 132.5, 137.1, 153.5, 169.2 ppm.

N-((2-Hydroxynaphthalen-1-yl)(naphthalen-2-yl)methyl)acetamide (Table 3, entry 14). White solid; m.p: 256–258 °C; yield: nano molten salt: 96%, nano SnO₂: 86%; IR (KBr): ν 3407, 3153, 3060, 3011, 1644, 1629, 1514, 1271 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.05 (s, 3H, –CH₃), 7.26 (d, 1H, J = 8.8 Hz, –CH aliphatic), 7.29 (d, 2H, J = 5.6 Hz, ArH), 7.34 (t, 2H, J = 5.6 Hz, ArH), 7.47 (t, 2H, J = 5.6 Hz, ArH), 7.53 (d, 3H, J = 5.6 Hz, ArH), 7.83 (t, 3H, J = 7.6 Hz, ArH), 7.90 (s, 1H, ArH), 8.59 (d, 1H, J = 8.4 Hz, –NH), 10.05 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 23.2, 48.4, 119.0, 119.2, 122.9, 123.8, 124.2, 125.5, 125.9, 126.5, 126.8, 127.8, 128.0, 128.1, 129.0, 129.1, 129.9, 132.2, 132.9, 133.2, 140.8, 153.7, 169.9 ppm.

N-(1-(2-Hydroxynaphthalen-1-yl)-2-methyl-3-phenylallyl)acetamide (Table 3, entry 15). White solid; m.p: 223–225 °C; yield: nano molten salt: 92%, nano SnO₂: 83%; IR (KBr): ν 3395, 3055, 3023, 2965, 1627, 1524, 1515, 1371, 1274 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 1.67 (s, 3H, –CH₃), 1.94 (s, 3H, –CH₃), 6.45 (s, 1H, ArH), 6.53 (d, 1H, J = 8.4 Hz, –CH aliphatic), 7.22 (t, 4H, J = 8.8 Hz, ArH), 7.28 (d, 1H, J = 6.8 Hz, ArH), 7.34 (d, 2H, J = 7.6 Hz, ArH), 7.45 (t, 1H, J = 7.2 Hz, ArH), 7.76 (d, 1H, J = 8.8 Hz, ArH), 7.81 (d, 1H, J = 7.6 Hz, ArH), 8.13 (d, 1H, J = 8.4 Hz, ArH), 8.28 (d, 1H, J = 8.4 Hz, –NH), 9.95 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 16.7, 23.1, 51.4, 117.8, 119.0, 122.8, 123.5, 123.6, 126.6, 126.7, 128.6, 128.9, 129.0, 129.1, 129.6, 133.4, 138.2, 138.5, 153.8, 169.5 ppm; MS: m/z = 331 [M]⁺.

N-(Biphenyl-4-yl(2-hydroxynaphthalen-1-yl)methyl)acetamide (Table 3, entry 16). White solid; m.p: 244–246 °C; yield: nano molten salt: 96%, nano SnO₂: 88%; IR (KBr): ν 3395, 3156, 3060, 3030, 3011, 1643, 1516, 1335 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 2.00 (s, 3H, –CH₃), 7.17 (d, 1H, J = 8.4 Hz, –CH aliphatic), 7.24 (t, 2H, J = 8.8 Hz, ArH), 7.27 (d, 1H, J = 8.8 Hz, ArH), 7.34 (d, 2H, J = 7.6 Hz, ArH), 7.45 (t, 2H, J = 7.6 Hz, ArH), 7.56 (d, 2H, J = 7.6 Hz, ArH), 7.61 (d, 2H, J = 7.2 Hz, ArH), 7.79 (d, 1H, J = 8.8 Hz, ArH), 7.83 (d, 2H, J = 7.6 Hz, ArH), 7.89 (t, 1H, J = 7.0 Hz, ArH), 8.51 (d, 1H, J = 8.4 Hz, –NH), 10.06 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 23.1, 48.1, 118.9, 119.2, 122.9, 126.8, 127.0, 127.1, 127.7, 128.9, 129.0, 129.3, 129.8, 132.8, 138.5, 140.4, 142.4, 153.6, 169.8 ppm; MS: m/z = 367 [M]⁺.

N-((2-Hydroxynaphthalen-1-yl)(4-nitrophenyl)methyl)benzamide (Table 3, entry 17). Yellow solid; m.p: 253–255 °C; yield: nano molten salt: 96%, nano SnO₂: 87%; IR (KBr): ν 3435, 3415, 3181, 3082, 3069, 1637, 1600, 1577, 1516, 1345 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 5.75 (brs, 1H, –OH), 7.29 (d, 1H, J = 8.8 Hz, –CH aliphatic), 7.34 (d, 1H, J = 7.6 Hz, ArH), 7.43 (d, 1H, J = 7.6 Hz, ArH), 7.50 (t, 1H, J = 7.4 Hz, ArH), 7.61 (t, 2H, J = 7.6 Hz, ArH), 7.74 (dd, 2H, J = 8.0 Hz, ArH), 7.87 (dd, 2H, J = 8.8 Hz, ArH), 7.92 (d, 2H, J = 7.2 Hz, ArH), 8.10 (d, 2H, J = 8.0 Hz, ArH), 9.18 (d, 2H, J = 8.0 Hz, ArH), 10.50 (brs, 1H, –NH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 49.4, 121.4, 122.1, 123.0, 123.3, 127.5, 127.9, 128.0, 128.7, 128.8, 128.9, 129.2, 129.6, 130.0, 130.2, 130.5, 131.7, 132.1, 132.7, 133.8, 134.4, 135.0, 145.0, 193.7 ppm.

N-((2,5-Dimethoxyphenyl)(2-hydroxynaphthalen-1-yl)methyl)benzamide (Table 3, entry 19). Yellow solid; m.p: 271–273 °C; yield: nano molten salt: 93%, nano SnO₂: 83%; IR (KBr): ν 3420, 3160, 3065, 2993, 1640, 1577, 1526, 1492, 1275 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 3.61 (s, 3H, –CH₃), 3.66 (s, 3H, –CH₃), 6.80 (d, 1H, J = 3.2 Hz, ArH), 6.91 (d, 1H, J = 8.8 Hz, –CH aliphatic), 7.09 (s, 1H, ArH), 7.20 (d, 1H, J = 8.8 Hz, ArH), 7.30 (t, 1H, J = 7.4 Hz, ArH), 7.47 (t, 4H, J = 6.4 Hz, ArH), 7.52 (d, 1H, J = 7.2 Hz, ArH), 7.74 (d, 1H, J = 8.8 Hz, ArH), 7.80 (d, 1H, J = 8.4 Hz, ArH), 7.85 (d, 2H, J = 7.2 Hz, ArH), 8.27 (d, 1H, J = 8.8 Hz, ArH), 8.84 (d, 1H, J = 8.0 Hz, –NH), 10.17 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 45.8, 55.7, 56.6, 112.0, 112.5, 116.5, 119.0, 119.2, 123.0, 123.7, 126.6, 127.6, 128.7, 128.8, 128.9, 129.4, 131.4, 131.6, 133.0, 135.0, 151.4, 153.3, 153.7, 165.5 ppm; MS: m/z = 413 [M]⁺.

N-((2-Hydroxynaphthalen-1-yl)(naphthalen-1-yl)methyl)benzamide (Table 3, entry 20). White solid; m.p: 293–295 °C; yield: nano molten salt: 95%, nano SnO₂: 85%; IR (KBr): ν 3424, 3128, 3031, 1629, 1536, 1342, 1250 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 7.28 (d, 1H, J = 3.6 Hz, –CH aliphatic), 7.30 (d, 1H, J = 5.2 Hz, ArH), 7.40 (t, 3H, J = 6.0 Hz, ArH), 7.44 (d, 2H, J = 7.6 Hz, ArH), 7.51 (t, 1H, J = 7.2 Hz, ArH), 7.57 (d, 2H, J = 8.0 Hz, ArH), 7.85 (t, 4H, J = 8.2 Hz, ArH), 7.90 (d, 1H, J = 7.2 Hz, ArH), 7.95 (d, 1H, J = 8.0 Hz, ArH), 7.99 (d, 1H, J = 8.0 Hz, ArH), 8.09 (d, 1H, J = 7.6 Hz, ArH), 8.27 (d, 1H, J = 8.0 Hz, ArH), 9.26 (d, 1H, J = 8.4 Hz, –NH), 10.22 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 48.4, 118.3, 119.2, 122.9, 123.9, 125.7, 126.1, 126.5, 126.9, 127.9, 128.4, 128.7, 129.0, 129.1, 129.2, 129.8, 131.7, 131.8, 133.3, 134.1, 134.7, 136.7, 154.1, 165.8 ppm; MS: m/z = 403 [M]⁺.

N-(1-(2-Hydroxynaphthalen-1-yl)-3-phenylallyl)benzamide (Table 3, entry 21). Yellow solid; m.p: 201–203 °C; yield: nano molten salt: 92%, nano SnO₂: 82%; IR (KBr): ν 3413, 3180, 3062, 3027, 1634, 1516, 1341, 1277 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 6.56 (d, 2H, J = 7.8 Hz, ArH), 6.78 (t, 1H, J = 9.6 Hz, –CH aliphatic), 6.84 (t, 1H, J = 6.0 Hz, ArH), 7.21 (t, 2H, J = 6.2 Hz, ArH), 7.28 (t, 3H, J = 7.6 Hz, ArH), 7.39 (d, 2H, J = 7.2 Hz, ArH), 7.51 (t, 3H, J = 9.2 Hz, ArH), 7.76 (d, 1H, J = 8.8 Hz, ArH), 7.83 (d, 1H, J = 8.4 Hz, ArH), 7.86 (d, 2H, J = 7.6 Hz, ArH), 8.30 (d, 1H, J = 8.4 Hz, ArH), 8.95 (d, 1H, J = 6.0 Hz, –NH), 10.22 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 49.2, 118.7, 119.1, 123.0, 123.3, 126.7, 126.9, 127.6, 127.6, 128.8, 129.0, 129.5, 129.8, 130.1, 131.7, 132.4, 134.9, 137.1, 153.6, 165.7, 182.9 ppm; MS: m/z = 379 [M]⁺.

N-((2-Hydroxynaphthalen-1-yl)(naphthalen-2-yl)methyl)benzamide (Table 3, entry 22). Yellow solid; m.p: 264–266 °C; yield: nano molten salt: 95%, nano SnO₂: 85%; IR (KBr): ν 3419, 3062, 3029, 1629, 1535, 1344, 1275 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 7.29 (d, 1H, J = 9.2 Hz, –CH aliphatic), 7.33 (d, 1H, J = 7.6 Hz, ArH), 7.46 (d, 4H, J = 9.6 Hz, ArH), 7.48 (s, 1H, ArH), 7.52 (d, 2H, J = 7.6 Hz, ArH), 7.58 (t, 1H, J = 7.2 Hz, ArH), 7.86 (t, 6H, J = 6.4 Hz, ArH), 7.93 (d, 2H, J = 7.2 Hz, ArH), 8.17 (d, 1H, J = 8.8 Hz, ArH), 9.15 (d, 1H, J = 8.8 Hz, –NH), 10.38 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 49.9, 118.7, 119.2, 123.2, 123.3, 124.9, 125.8, 126.1, 126.6, 127.3, 127.7, 127.8, 127.9, 128.2, 128.3, 128.9, 129.0, 129.1, 130.0, 131.9, 132.4, 132.9, 133.2, 134.8, 140.1, 153.8, 166.5 ppm; MS: m/z = 403 [M]⁺.

N-(1-(2-Hydroxynaphthalen-1-yl)-2-methyl-3-phenylallyl)benzamide (Table 3, entry 23). Yellow solid; m.p: 244–246 °C; yield: nano molten salt: 92%, nano SnO₂: 81%; IR (KBr): ν 3419, 3065, 3026, 2905, 1629, 1514, 1340, 1272 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 1.88 (s, 3H, –CH₃), 6.41 (s, 1H, –CH), 6.75 (d, 1H, J = 8.4 Hz, –CH aliphatic), 7.20 (t, 3H, J = 7.0 Hz, ArH), 7.25 (d, 1H, J = 8.8 Hz, ArH), 7.32 (t, 3H, J = 5.8 Hz, ArH), 7.47 (d, 2H, J = 7.2 Hz, ArH), 7.56 (d, 2H, J = 7.2 Hz, ArH), 7.82 (t, 2H, J = 9.6 Hz, ArH), 7.87 (d, 2H, J = 7.2 Hz, ArH), 8.23 (d, 1H, J = 8.4 Hz, ArH), 8.83 (d, 1H, J = 8.4 Hz, –NH), 10.21 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 16.7, 53.1, 117.5, 119.1, 123.0, 123.4, 124.9, 126.7, 127.0, 127.6, 128.6, 128.8, 128.9, 129.0, 129.2, 129.7, 131.8, 133.3, 135.0, 137.8, 137.9, 153.9, 166.2 ppm; MS: m/z = 393 [M]⁺.

N-(Biphenyl-4-yl(2-hydroxynaphthalen-1-yl)methyl)benzamide (Table 3, entry 24). White solid; m.p: 281–283 °C; yield: nano molten salt: 96%, nano SnO₂: 86%; IR (KBr): ν 3414, 3071, 3026, 2940, 1631, 1538, 1342 cm⁻¹; ¹H NMR (400 MHz, DMSO-d₆): δ 7.28 (d, 1H, J = 8.8 Hz, –CH aliphatic), 7.33 (d, 2H, J = 7.2 Hz, ArH), 7.38 (t, 3H, J = 7.4 Hz, ArH), 7.45 (t, 2H, J = 7.6 Hz, ArH), 7.51 (t, 3H, J = 7.4 Hz, ArH), 7.61 (d, 5H, J = 8.8 Hz, ArH), 7.83 (d, 1H, J = 8.8 Hz, ArH), 7.87 (d, 1H, J = 7.62 Hz, ArH), 7.90 (d, 2H, J = 8.4 Hz, ArH), 8.15 (d, 1H, J = 8.4 Hz, ArH), 9.10 (d, 1H, J = 8.8 Hz, –NH), 10.41 (brs, 1H, –OH) ppm; ¹³C NMR (100 MHz, DMSO-d₆): δ 49.5, 118.7, 119.1, 123.2, 127.0, 127.1, 127.3, 127.5, 127.6, 127.8, 128.8, 129.0, 129.1, 129.4, 129.9, 131.9, 132.8, 134.7, 139.0, 140.4, 141.7, 153.7166.2 ppm; MS: m/z = 429 [M]⁺.

Acknowledgements

The authors gratefully acknowledge the Bu-Ali Sina University Research Council and Center of Excellence in Development of Environmentally Friendly Methods for Chemical Synthesis (CEDEFMCS) for providing support to this work.

Notes and references

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Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c5ra02718g

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