(CTA)3[SiW12]-Li+-MMT: A novel, efficient and simple nanocatalyst for facile and one-pot access to diverse and densely functionalized 2-amino-4H-chromene derivatives via an eco-friendly multicomponent reaction in water

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ARTICLE

(CTA)₃[SiW₁₄]-Li⁺-MMT: A Novel, Efficient and Simple Nanocatalyst

for the Facile and One-pot Access to Diverse and Densely

Functionalized 2-amino-4H-chromene Derivatives via an Eco-

Friendly Multicomponent Reaction in Water

Received 00th January 20xx,

Accepted 00th January 20xx

DOI: 10.1039/x0xx00000x

Esmayeel Abbaspour-Gilandeh^*a, Mehraneh Aghaei-Hashjin^b, Asieh Yahyazadeh^c, and Hadi Salemi^d

www.rsc.org/

A simple, facile and highly efficient one-pot synthesis of a pharmaceutically interesting diverse kind of functionalized 2-

amino-4H-chromenes by a straightforward and three-component reaction of an aromatic aldehyde, malononitrile (or ethyl

cyanoacetate) and diverse enolizable C-H activated acidic compounds in the presence of a catalytic amount of

(CTA)₃[SiW₁₄]-Li⁺-MMT is reported as a novel, environmental friendly, reusable and promising nanocatalyst in refluxing

water. Based on the procedure, it was feasible to synthesize 2-amino-3-cyano-pyrano[3,2-c]chromen-5(4H)-one (4a−4y), 2-

amino-3-cyano-pyrano[3,2-c]quinolin-5(4H)-ones (6a−6s), 2-amino-3-cyano-7,8-dihydro-4H-chromen-5(6H)-one (8a−8u),

2-amino-3-cyano-pyrano[4,3-b]pyran-5(4H)-ones (12a−12f), 2-amino-3-cyano-pyrano[3,2-c]pyridine-6(5H)-ones (13a−13f)

and 1H-pyrano[2,3-d]pyrimidine-2,4(3H,5H)-diones (14a−14f). The structure of the nanocatalyst was conﬁrmed by various

techniques such as IR, SEM, TGA-DTG, EDX, ICP and XRD analyses. In comparison to the conventional methods, the salient

features of the present protocol are green reaction conditions, high quantitative yields, short reaction time, high atom-

economy, low cost, easy isolation of products and no column chromatographic separation.

[3]. Heteropolyacids have attracted high attention due to

unique Keggin structures, strong acidity and solubility in nonꢀ

Introduction

The usage of heterogeneous catalysts in organic synthesis is

an interesting method to access to green catalysts, which are

compatible with the environment and highꢀinterest in

different processes of chemical transformations has occurred

by catalysts in heterogeneous conditions [1]. In recent years,

the synthesis of catalysts based on heteropolyacids and related

compounds due to some reasons such as the lack of need for

separation through distillation or extraction has attracted high

attraction in synthetic chemistry, technology and

pharmaceutical industry fields and [2] only partial changes in

selectivity and activity provide the possibility of their reuse

polar solutions [4]. This class of compounds as an excellent

and versatile catalyst owing to some interesting features

including nonꢀcorrosiveness, flexible acidic strength, high

reductivity, high hydrolytic and thermal stability and also low

toxicity can be utilized to catalyze a wide range of

homogeneous and heterogeneous catalytic processes [5].

Nevertheless, drawbacks such as the problem of separation

from reaction mixture and low surface area (1–10 m²/g) have

encountered the aboveꢀmentioned advantages with difficulties

[6]. It seems that the heterogenization of heteropolyacids in

an insoluble organic and separable matrix with a wide surface

extent such as zeolite and clay or by formation of micro and

mesoporosity salts of cesium or potassium (Cs_2.5H_0.5PW or

K_2.5H_0.5PW) makes the increase of access to acid sites and

control of acidic strength of solid possible [7].

Montmorillonite (MMT) is one of the most applicable

compounds of layered silicate, which its usage has attracted

^a.Young Researchers and Elites Club, Ardabil Branch, Islamic Azad University,

Ardabil, Iran. E-mail: abbaspour1365@yahoo.com; Fax: +98 45 33332238.

^b.Department of Chemistry, Payame Noor University (PNU), Tehran, Iran.

^c.Chemistry Department, University of Guilan, Rasht, Iran.

^d.Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS),

Gava Zang, Zanjan, Iran

Electronic Supplementary Information (ESI) available: [details of any

supplementary information available should be included here]. See

DOI: 10.1039/x0xx00000x

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high attention due to large specific surface area, high Moreover, it was found that the natural products containing

modulus, layered structure, high cation exchange capacity, chromene moiety can play an important role in synthetic

chemical and mechanical stability as well as having natural approaches to promising compounds in the field of

resources [8]. The building blocks of Montmorillonite layers biodegradable agrochemicals [21], medicinal [22], pigments

consist of an aluminum octahedral layer [Al(OH₆)⁻³] and cosmetic industries [23]. These valued features have

−2

sandwiched between two tetrahedral siliconꢀoxygen (Si₂O₅

)

inspired chemists to simulate such natural designs in

layers [9]. According to the ion exchange property of developing the derived analogues of alkaloids, for instance,

montmorillonite, the ions of Mg²⁺and Fe²⁺can be replaced arisugacin [24], amarogentin [25], (+)ꢀcalanolide A [26],

with Al³⁺. Owing to these substitutions, negative electric huajiaosimuline and veprisine [27], which all contain the key

charge appears in lattice that the unit of positive electrical pyranꢀannulated pharmacophoric motif (Scheme 1).

R¹

charge as an alkali cation or earth alkaline such as Na⁺, K⁺,

R²

R³

O

Ca⁺and Mg²⁺can replace itself in the space between layers

and the bond in the threeꢀunit layers of montmorillonite is

established by these cations [10]. Montmorillonite layers with

thickness of approximately 1nm and lateral dimensions of

30nm up to several micrometers are known as a nanoꢀporous

with regular structure [11]. The common phenomenon of the

broken bonds of layered silicate causes the formation of

hydroxyl groups that can be used for chemical modifications

[12]. It should be noted that the distribution property of MMT

in water increases its basic distance and this swell can be

attributed to the cation collection in its interlayer. According

to this point that clay soil benefits from high adsorption

capacity, but the modification of their structure increases the

efficacy of these compounds so that they can react with

reactants better [13].

O

OH

H

O

H

O

OH

HO

O

HO

OH

amarogentin

arisugacin A: R¹=R²=OMe; R³=H

arisugacin B: R¹=R³=H; R²=OMe

O

N

O

R

O

N

O

R

R=OMe, veprisine

R=H, findersine

(+)-calanolide A

huajiaosimuline

Scheme 1 Examples of bioactive compounds bearing

pyran-annulated scaffolds.

Experimental

General

4HꢀPyrans and 4Hꢀpyranꢀannulated heterocyclic scaffolds,

namely, 4Hꢀchromene moieties are the key building block of

numerous oxygenꢀcontaining heterocyclic natural compounds

possessing distinct properties of general interest. This

structural motif is broadly represented by several types of

alkaloids manifesting diverse biological and pharmacological

activities including antitumor [14], antiꢀHIV [15], antiꢀ

inflammatory [16], antimicrobial and antifungal [17], and

antiallergenic ones [18], along with antineurodegenerative

disorders such as Alzheimer’s disease (AD), Parkinson’s

disease (PD), Huntington’s Diseases (HD) and few others

[19]. Furthermore, many of these functionalized 4Hꢀpyran

derivatives demonstrate cancer cell growth inhibitory activity

and are surveyed as potential anticancer agents [20].

All chemical materials were purchased from Fluka and

Merck companies and used without further purification.

The purity determination of the product and reaction

monitoring were accomplished by TLC on silica gel

PolyGram SILG/UV 254 plates. The Melting points were

determined using an Electrothermal 9100 apparatus and

are uncorrected. The IR spectra were recorded as KBr

pellets on a PerkinElmer PXI instrument. The NMR

spectra were obtained using

a BRUKER DRXꢀ300

AVANCE spectrometer at room temperature in DMSO

using TMS as an internal standard. Inductively coupled

plasma atomic emission spectrometry (ICPꢀAES),

measurements were performed on a VARIAN VISTAꢀ

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o

MPX. Thermogravimetric analyses (TGA) were conducted material was kept at 100 C for 2 days to obtain CTAꢀLi⁺ꢀ

by using Linseis SATꢀPT 1000 thermoanalyzer MMT as a white powder.

a

instrument. Samples were heated from 25 to 650 ^oC at

ramp 10 °C/min under N₂atmosphere. Scanning election

microphotographs (SEM) were obtained on a SEMꢀLEO

1430VP. The low and broad angle Xꢀray diffraction

(XRD) measurements were accomplished in the 2θ range

of 3ꢀ80^oat room temperature on a Siemens Dꢀ500 Xꢀray

diffractometer (Germany), using Niꢀfiltered CoꢀKα

radiation. Elemental analyses were conducted on a Carloꢀ

Erba EA1110CNNOꢀS analyzer and agreed (within 0.30)

with the calculated values.

Preparation of (CTA)₃[SiW₁₄]-Li⁺-MMT. 1.40

g of

H₄SiW₁₂O₄₀(HPA) was dissolved in 20 mL methanol and

added dropwise to 50 mL aqueous suspension of 4.70 g of

CTAꢀLi⁺ꢀMMT. Then, the reaction mixture was stirred at

ambient temperature for 1 day. The heterogeneous catalyst

was filtered off and washed with deionized water several

o

times and thereafter it was dried in an oven at 120 C for 7

hours to obtain (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT.

General Procedure for the Preparation of 2-amino-4H-

chromene Derivatives (4, 6, 8, 12- 14)

Catalyst Synthesis

In a ovenꢀdried screw cap test tube equipped with a magnetic

stir bar, enolizable compound (1, 5, 7, 9ꢀ11, 1mmol),

aldehyde (2, 1 mmol), malononitrile (or ethyl cyanoacetate)

(3, 1.1 mmol) and (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT (10 mg) were

combined with each other in water (5 mL) and the mixture

was refluxed at 100 ^oC. The progress of the reaction was

monitored using silica gel coated on aluminum sheets and

ethyl acetateꢀpetroleum ether as eluent. After the completion

of the reaction, the reaction mixture was filtered off and the

catalyst was washed twice with CH₂Cl₂(8 mL). With the

evaporation of the solvent under reduced pressure pure

product was almost obtained.

Preparation of Li⁺-MMT. The ionꢀexchanged Li⁺ꢀMMT

clays were prepared via cation exchange between natural

montmorillonite (Cloisite®Na⁺, Southern Clay Products) and

lithium chloride. Cloisite®Na⁺slowly dispersed into LiCl

solution with vigorous stirring. The suspension was stirred

with magnetic stirrer for 48 hours at 40 ^oC to replace the

sodium completely by lithium cations and then centrifuged at

5000 rpm to separate the Li⁺ꢀMMT clay from the supernatant

containing the excess ions. The mixture was washed with deꢀ

ionized water until chloride ions were completely removed as

indicated by AgNO₃test. The modified samples were dried in

o

a vacuum oven at 60 C for 24 hours and were grinded. The

analysis of atomic absorption for this solid metal has shown

that it is 0.05 mol% in the concentration of dissolved Li⁺ions.

Spectral data of the new products

2-Amino-5-oxo-4-(naphthalen-1-yl)-4,5-

dihydropyrano[3,2-c]chromene-3-carbonitrile (Table 1,

Preparation of CTA-Li⁺-MMT. In a 250 mL of roundꢀ

bottom flask, 4.50 g Li⁺ꢀmontmorillonite was taken in 50 ml

of distilled water and magnetically stirred till a uniform

dispersion was formed. 2.90 g hexadecyltrimethylazanium

bromide (CTAB) was then dissolved in 20 mL distilled water

and the two solutions were mixed together. After the

completion of the addition, the reaction mixture was stirred

for 1 day. The resultant solid sample was collected by

centrifugation and washed several times with deionized water

to remove the free CTAB until no bromide ion was detected

with a 0.1 mol/L aqueous AgNO₃solution. Finally, the

o

Entry 4t): Yellow powder (92%); mp> 300 C; IR (KBr)

1

ν_max/cm⁻: 1384, 1365 (NꢀH bend), 1669 (C=O), 2195

1

(CN), 3163 (NꢀH amidic), 3390, 3454 (NꢀH amine); H

NMR (400.22 MHz, DMSOꢀd₆): δ 5.50 (s, 1H, CH),7.17

(d, 1H, CH), 7.22 (s, 2H, NH₂), 7.34 (dt, 1H, CH), 7.37 (d,

1H, CH), 7.41 (t, 1H, CH ), 7.55 (dt, 1H, CH), 7.37ꢀ7.57

(m, 2H), 7.80 (d, 1H, CH), 7.95 (dd, 1H, CH), 7.99 (d, 1H,

CH), 8.49 (d, 1H, CH). ¹³CNMR (100.6 MHz, DMSOꢀd₆):

56.4, 59.9, 109.7, 112.5, 116.0, 1120.4, 122.3, 122.6,

124.5, 125.5, 126.1, 126.3, 126.4, 127.6, 129.0, 131.5,

131.8, 133.9, 138,9, 141.9, 152.1, 159.5, 161.0.

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Li⁺ꢀMMT samples in the region of 400ꢀ4000 cm^ꢀ1are

presented in Figure 1. In the spectrum of the pure Na⁺ꢀMMT,

2-Amino-5-oxo-4-(thiophen-2-yl)-4,5-

dihydropyrano[3,2-c]quinoline-3-carbonitrile (Table 2,

Entry 6r): White powder (93%); mp: 285ꢀ287 ^oC; IR the observed peak at 3629 cm⁻¹is related to the OH groups

1

(KBr) ν_max/cm⁻: 1389, 1367 (NꢀH bend), 1665 (C=O),

attached to the aluminum and/or magnesium while appeared

peaks in the 3439 and 1645 cm^ꢀ1region can be respectively

2198 (CN), 3174 (NꢀH amidic), 3325, 3462 (NꢀH amine);

¹H NMR (400.22 MHz, DMSO): δ 4.90 (s, , 1H, CH), 6.94

attributed to the stretching and bending vibrations of the

water molecules OH bond. The 1040 and 916 cm⁻¹bands in

(dd, 1H, CH),7.30 (dt, 1H, CH), 7.34 (dd, 1H, CH), 7.36

this sample have been collectively assigned to the SiꢀO

stretching vibrations. The presented spectra of Li⁺ꢀMMT are

nearly identical with the Na⁺ꢀMMT, indicating that FTIR is

not sensitive to the occurred changes in the system. In the

case of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT, the absorption peaks at

2855 and 2927 cm⁻¹have been assigned to the stretching

vibration of CꢀH bond. The bending vibrations presence of

this bond at 1400ꢀ1500 cm⁻¹is associated to the CTA⁺cations

arrival to this material. The presence of Kegginꢀtype HPW

groups was confirmed by stretching vibrations appeared at

approximately 925 cm⁻¹(SiꢀO in central tetrahedral), 975

cm⁻¹(terminal W=O), 896 cm⁻¹(WꢀObꢀW in corner shared

octahedral) and 807 cm⁻¹(WꢀOcꢀWin edge shared octahedral)

in the FTꢀIR spectrum. Therefore, despite these peaks, it can

be concluded that the [SiW₁₄] is surrounded into the Li⁺ꢀ

MMT.

(d, 1H, CH), 7.41 (s, 2H, NH₂), 7.57 (dt, 1H, CH), 7.59 (dt,

1H, CH),7.89 (dd, 1H, CH), 7.90 (dd, 1H,CH), 11.90 (s,

1H, NH). ¹³C NMR (100.6 MHz, DMSO): δ 33.2, 58.1,

110.5, 112.8, 116.0, 120.1, 122.4, 122.6, 125.0, 125.3,

127.5, 132.0, 138.4, 149.4, 151.9, 160.3, 161.0.

Results and discussion

Catalyst Characterization

ICP analysis of (CTA)₃[SiW₁₄]-Li⁺-MMT. Inductively

coupled plasma atomic emission spectrometry (ICPꢀAES)

to show insertion of the H₄SiW₁₂O₄₀(SiW₁₄) to the CTAꢀ

Li⁺ꢀMMT was used. The ICP analysis showed about 0.09

mmol per gram of H₄SiW₁₂O₄₀heteropoly acid is

successfully encapsulated into the montmorillonite layers.

IR Analysis of (CTA)₃[SiW₁₄]-Li⁺-MMT. The infrared

spectra of the pure Na⁺ꢀMMT, Li⁺ꢀMMT and (CTA)₃[SiW₁₄]ꢀ

Fig. 1 FT-IR spectra of (CTA)₃[SiW₁₄]-Li⁺-MMT.

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Thermal studies of (CTA)₃[SiW₁₄]-Li⁺-MMT. The TGA structural OHꢀgroups of lithium montmorillonite. The TGA of

and DTG analysis have been carried out to characterize (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT illustrates approximately 5%

(CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT and Li⁺ꢀMMT samples towards weight loss in the range from 350 to 400 ^oC due to the

each other. The results of these analyses are provided in decomposition of the organic part of CTAB and degradation

Figure 2. The TGA curve of Li⁺ꢀMMT demonstrates a weight of the tungstophosphoric acid. Furthermore, a small weight

o

loss of approximately 6% up to a temperature of 150 ^oC, loss of approximately 5% is appeared up to 650 C, which is

which is concerned with the loss of trapped and interlayer associated with the decomposition of the remaining organic

moisture. In addition, there is a slight weight loss between compound and conversion of silicotungstate anion to the

150ꢀ600 ^oC, probably corresponding to the breaking of tungsten and silicon oxides [28].

Fig. 2 TGA/DTG curves of (a) Li⁺-MMT and (b) (CTA)₃[SiW₁₄]-Li⁺-MMT.

SEM analysis of (CTA)₃[SiW₁₄]-Li⁺-MMT. The surface these nanoparticles. In the case of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT

morphology, size distribution and particle shape of the Li⁺ꢀ with disappearing the lumpy shape of Li⁺ꢀMMT, some layers

MMT and (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT nanocatalyst were were formed as uniform and flaky structure that this could be

investigated by SEM (Scanning Electron Microscopy) as attributed to the reduction of hydrophilisity property and

represented in Figure 3. The SEM images for Li⁺ꢀMMT and adherence among montmorillonite particles.

modified Li⁺ꢀMMT clearly show variations in the surface of

Fig.

3

SEM images of Li⁺-MMT (a) and (CTA)₃[SiW₁₄]-Li⁺-MMT (b).

EDX analysis of (CTA)₃[SiW₁₄]-Li⁺-MMT. EDX (Energy composition of Li⁺ꢀMMT and (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT

Dispersive Xꢀray) mapping was carried out to verify the nanocatalysts, respectively (Figure 4a and b). The EDX

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analysis confirmed the existence of a number of tungsten nanocatalyst denoting tungstophosphoric acid was inserted

peaks. Morever, strong oxygen and silicon peaks in the successfully in the mesoporous Li⁺ꢀMMT.

Fig. 4 EDX spectrum of (a) Li⁺-MMT and (b) (CTA)₃[SiW₁₄]-Li⁺-MMT.

XRD analysis of (CTA)₃[SiW₁₄]-Li⁺-MMT. Figure 5a presence of these groups in the montmorillonite layers

represents the XRD (XꢀRay Diffraction) patterns of the used increases the lipophilic character of this compound, which

Li⁺ꢀMMT and (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT catalyst to illustrate can be led to its performance improvement in organic

the changes of distance between the montmorillonite layers reactions. Also, Figure 5b illustrates the XRD (XꢀRay

(d₀₀₁). The calculated basal spacing for the Li⁺ꢀMMT Diffraction) patterns of the used Li⁺ꢀMMT and

appeared at 2θ = 8.6^o, while in the pattern of (CTA)₃[SiW₁₄]ꢀ (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT catalyst. As observed in XRD

Li⁺ꢀMMT, this peak has shifted to a lower value at 2θ = 6.1^o. patterns, a similar nature in the spectrum of the Li⁺ꢀMMT and

These observations suggest that the CTAB as a long chain (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT samples indicates the retention of

alkyl group and HPA as a bulky mineral group have been the

original crystalline structure

and

morphology

intercalated into montmorillonite interlayer spaces. The of montmorillonite nanoparticles.

Fig. 5 Low angle (a) and Broad angle (b) XRD patterns of (CTA)₃[SiW₁₄]-Li⁺-MMT and Li⁺-MMT.

In continuation of our efforts to the synthesis of pyranꢀ transformations with the aid of green synthetic methodologies

annulated compounds and in performing organic [29], we decided to investigate the synthesis of 2ꢀaminoꢀ3ꢀ

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cyanoꢀ4Hꢀpyrans with diverse substituents from the reaction (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT as a novel, ecoꢀfriendly, reusable

of C−Hꢀactivated acid varieties, aldehyde and malononitrile and promising nanocatalyst (Scheme 2).

(or ethyl cyanoacetate) in water reflux conditions using

R

O

X

H

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

R

H

X

NC

O

NH₂

OH

X = CN, COOEt

Scheme 2 One-pot three-component reaction of different C−H-activated acidic compounds, aldehydes and active methylene

nitriles catalyzed by (CTA)₃[SiW₁₄]-Li⁺-MMT in water.

In order to screen the reaction conditions for the synthesis 2ꢀ chemical reaction under study. In the next phase of survey,

aminoꢀ4ꢀ(4ꢀchlorophenyl)ꢀ3ꢀcyanoꢀpyrano[3,2ꢀc]chromeneꢀ

the effect of catalyst loading on the completion of the reaction

5(4H)ꢀone (4c), a systematic study considering different was evaluated (Entries 12ꢀ14). After several screening

variables affecting the reaction yield has been investigated in experiments with different amount of catalyst, it was found

the reaction of 4ꢀhydroxycoumarin (1), 4ꢀchlorobenzaldehyde that the highest yield (97%) was obtained when a catalytic

(2c) and malononitrile (3a) (molar ratio: 1:1:1.1) as the model amount (10 mg) of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT was applied in

reaction (Scheme 2). The results are indicated in the Table 1. H₂O under reflux conditions (Entry 13). Decreasing the

The primary optimization experiments revealed that any amount of catalyst (10 mg to 5 mg) resulted in lower yield of

formation of the desired product 4c was achieved under the product, while increasing the amount of catalyst required

solventꢀfree conditions even at 100 ^oC (Entries 1, 2). for the reaction from 10 mg to 15 mg did not affect the

Although, the trial reaction in the presence of water, as a duration of the reaction and the product yield (Entries 12, 14).

solvent, afforded the desired product 4c in slightly high yield In addition, to delineate the role of catalyst and temperature

compared to solventꢀfree conditions (Entries 3, 4). As could effect under solventꢀfree conditions, the reaction was

be seen in entry 4, the use of reflux conditions improved the investigated with and without temperature at the same amount

yield of the desired product. Unfortunately, the utilization of of catalyst (10 mg) (Entries 10, 11). It was observed that the

different solvents such as DMF, DMSO, CH₂Cl₂, CHCl₃and use of temperature leads to a faster reaction and a higher

toluene resulted in low product yields under reflux conditions yield.

(Entries 5ꢀ9). It was found that H₂O is the best solvent for

Table 1 Optimization of the three-component reaction of 4-hydroxycoumarin (1), 4-chlorobenzaldehyde (2c) and

malononitrile (3a) conditions under various conditions ^a

NH₂

CN

CHO

O

OH

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

CN

NC

O

Cl

O

1

Cl

2c

4c

3a

Entry

Catalyst

Catalyst loading Solvent

(mg)

Temperature

(°C)

Time

(min)

Yield^b

(%)

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1

2

3

4

5

6

7

8

9

10

11

12

13

14

ꢀ

10

5

10

15

ꢀ

r.t.

100

r.t.

Reflux

r.t.

6

-

H₂O

DMF

DMSO

CH₂Cl₂

CHCl₃

toluene

ꢀ

15%

33%

18%

20%

17%

21%

49%

73%

66%

97%

91%

ꢀ

(CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT

ꢀ

100

H₂O

Reflux

^aReaction conditions: 4-hydroxycoumarin (1 mmol), 4-Chlorobenzaldehyde (1 mmol), malononitrile (1.1 mmol), water (5 mL) and required amount of the

catalysts.

^bThe yields refer to the isolated product.

In order to generalize the optimum conditions, we extended show relatively low reactivity compared to the electronꢀ

the reaction of 4ꢀhydroxycoumarin (1) with a range of withdrawing groups (Entries 2ꢀ6 and 22ꢀ24). In addition to

appropriate aldehydes (2a–t), malononitrile (3a) or the aromatic aldehydes, the generality and substituent scope

ethylcyanoacetate (3b) under similar conditions (using of this method were evaluated by employing several

H₂O/(CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT), furnishing the respective 2ꢀ heterocyclic aldehydes in high to excellent yields (Entries 16ꢀ

aminoꢀ3ꢀcyanoꢀpyrano[3,2ꢀc]chromenꢀ5(4H)ꢀone derivatives 19, Table 2). It is also remarkable that with malononitrile (3a)

(4a-y) in high yields (Scheme 3). The optimized results are a slightly lower reaction time was required compared to ethyl

listed in Table 2. It was found that, aromatic aldehydes with cyanoacetate (3b) (entries 21ꢀ25, Table 2).

electronꢀdonating groups (entries 7ꢀ15 and 25, Table 2) did

NH₂

X

OH

O

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

R

H

NC

X

O

1

O

4

O

2

X = CN (3a), COOEt (3b)

Scheme 3 One-pot three-component condensation of 4-hydroxycoumarin (1), various aldehydes (2) and malononitrile or

ethyl cyanoacetate (3a-b).

Table

2 Synthesis of derivatives of 2-amino-3-cyano-pyrano[3,2-c]chromen-5(4H)-one (4) via condensation of 4-

hydroxycoumarin (1), various aldehydes (2) and malononitrile or ethyl cyanoacetete (3a-b) in the presence of (CTA)₃[SiW₁₄]-

Li⁺-MMT ^a

Time

(min)

M.P(Obsd)

(^oC)

M.P (Lit)

(^oC)

Carbon acid

(3) (X)

Entry

4a

RCHO (2)

Product

Yield%

NH₂

O

H

CN

O

3a (CN)

9

95

257ꢀ259

256ꢀ258^30a

O

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ARTICLE

NH₂

CN

Cl

O

Cl

4b

3a (CN)

6

4

8

96

97

95

245ꢀ246

244ꢀ246^30b

263–265^30l

260ꢀ262^30a

260ꢀ262^30c

H

O

NH₂

O

CN

O

4c

4d

4e

H

265ꢀ267

258ꢀ259

259ꢀ261

Cl

O

Cl

NH₂

O

H

F

O

F

NH₂

O

CN

O

O₂N

92

H

NO₂

O

NH₂

CN

O

4f

4g

4h

3a (CN)

8

95

251ꢀ253

258ꢀ260

253ꢀ255

250ꢀ252^30c

260ꢀ262^30a

252ꢀ254^30a

O₂N

O

NO₂

NH₂

Me

O

CN

O

Me

10

89

H

O

NH₂

CN

O

90

H

Me

O

Me

NH₂

OMeO

CN

O

4i

4j

3a (CN)

15

12

10

12

96

90

91

89

96

235ꢀ237

241ꢀ243

220ꢀ222

227ꢀ229

254ꢀ256

236–238^30h

242–244^30h

221ꢀ223^30b

228ꢀ230^30a

253ꢀ254^30j

OMe

H

O

NH₂

O

CN

O

MeO

H

OMe

O

NH₂

O

CN

O

4k

4l

O

OMe

NH₂

O

CN

O

MeO

H

OMe

O

NH₂

O

MeO

HO

4m

H

OMe

OH

O

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Journal Name

NH₂

O

CN

O

H

3a (CN)

10

15

97

87

259ꢀ260

259ꢀ261^30e

4n

HO

O

OH

NH₂

CN

O

4o

264ꢀ266

265ꢀ267^30a

N

O

N

NH₂

O

CN

O

S

4p

4q

4r

4s

3a (CN)

6

91

90

87

89

250ꢀ251

255ꢀ256

253ꢀ255

239ꢀ241

251ꢀ253^30d

256ꢀ258^30m

255ꢀ257^30c

238ꢀ240^30k

O

H

O

NH₂

O

CN

O

S

H

O

NH₂

CN

O

15

N

O

NH₂

O

CN

O

H

N

O

NH₂

O

4t

3a (CN)

8

92

285ꢀ287

ꢀꢀꢀ

H

O

NH₂

O

COOEt

O

4u

4v

4w

4x

3b (COOEt)

20

15

18

10

91

89

88

90

208ꢀ210

210ꢀ212

190ꢀ192

233ꢀ235

210ꢀ212^30f

209ꢀ212^30g

192ꢀ194^30h

232ꢀ234³⁰ⁱ

H

O

NH₂

Cl

COOEt

Cl

O

NH₂

O

COOEt

O

H

Cl

O

Cl

NH₂

O

COOEt

O

H

O₂N

O

NO₂

10 | J. Name., 2012, 00, 1-3

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NH₂

O

COOEt

O

4y

H

3b (COOEt)

20

87

197ꢀ199

199ꢀ201³⁰ⁱ

Me

O

Me

^aReaction conditions: 4-hydroxycoumarin (1 mmol), aldehyde (1 mmol), malononitrile or ethyl cyanoacetate (1.1 mmol), water (5 mL, reflux), (CTA)₃[SiW₁₄]-

Li⁺-MMT (10 mg).

^bAll compounds are known and their structures were determined from their spectral data and melting points as compared with literature values.

^cThe yields refer to Isolated products.

In the following conducted study, and in order to expand use presence of a catalytic amount of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT

of this nanocatalyst to the other reactions of these categories, (10 mg) under reflux conditions (Scheme 4). The similar

a series of polyfunctionalized 2ꢀaminoꢀ3ꢀcyanoꢀpyrano[3,2ꢀ trend of reactivity was obtained for different aldehydes when

c]quinolinꢀ5(4H)ꢀone derivatives (6a-s) were prepared from the reaction was repeated with 4ꢀhydroxyquinolone (5) under

the aqueous reaction mixture of 4ꢀhydroxyquinolone (5), the optimized conditions, which was mentioned above.

different aldehydes (2a-s) and malononitrile (3a) in the

NH₂

CN

O

OH

O

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

R

CN

NC

R

H

N

H

O

N

H

O

6

3a

5

2

Scheme 4 One-pot three-component reaction of 4-hydroxyquinolone (5), different aldehydes (2) and malononitrile (3a).

Table

3 Synthesis of derivatives of 2-amino-3-cyano-pyrano[3,2-c]quinolin-5(4H)-one (6) via condensation of 4-

hydroxycoumarin (5), various aldehydes (2) and malononitrile (3a) in the presence of (CTA)₃[SiW₁₄]-Li⁺-MMT ^a.

Carbon acid

(3) (X)

Time

(min)

M.P(Obsd)

(^oC)

M.P (Lit)

(^oC)

Entry

6a

RCHO (2)

Product

Yield%

NH₂

CN

O

H

O

3a (CN)

10

93

295ꢀ297

>300

>300^31a

>300^31b

>300^31c

>300^31b

N

H

O

NH₂

CN

Cl

O

Cl

6b

6c

6d

8

94

95

98

H

N

H

O

NH₂

CN

O

Cl

6

>300

H

Cl

N

H

O

NH₂

O

CN

O

8

298ꢀ300

Cl

N

H

Cl

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NH₂

CN

Cl

O

Cl

6e

H

3a (CN)

5

95

>300

>300^31b

Cl

N

H

O

Cl

NH₂

CN

O

>300^31a

H

6f

3a (CN)

7

8

96

97

>300

F

N

H

O

F

NH₂

O

>300^31c

Br

6g

H

Br

N

H

O

NH₂

CN

O

6h

6i

3a (CN)

6

9

93

94

92

91

>300

>300^31a

>300^31b

>300^31a

Br

N

H

O

Br

NH₂

CN

O

O₂N

NO₂

H

N

H

O

NH₂

O

CN

O

6j

12

O₂N

N

H

O

NO₂

NH₂

O

6k

H

NC

N

H

O

CN

NH₂

O

6l

6m

6n

6o

3a (CN)

13

12

13

93

88

89

>300

>300^31a

H

Me

N

H

O

Me

NH₂

CN

O

>300^31c

MeO

OMe

H

N

H

O

NH₂

O

297ꢀ299

296ꢀ298

>300^31b

MeO

HO

N

H

O

OMe

NH₂

O

>300^31a

H

N

O

OH

H

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NH₂

CN

O

MeO

HO

6p

H

3a (CN)

94

>300

>300^31a

OMe

12

N

O

OH

H

NH₂

CN

O

>300^31a

O

6q

6r

6s

3a (CN)

O

7

93

92

>300

H

N

H

O

NH₂

CN

O

S

---

H

N

H

O

NH₂

CN

H

O

N

13

>300^31a

N

O

H

a

Reaction conditions: 4-hydroxyquinolin-2(1H)-one (1 mmol), aldehyde (1 mmol), malononitrile or ethyl cyanoacetate (1.1 mmol), water (5 mL, reflux),

(CTA)₃[SiW₁₄]-Li⁺-MMT (10 mg).

^bAll compounds are known and their structures were determined from their spectral data and melting points as compared with literature values.

^cThe yields refer to Isolated products.

After successfully synthesizing a series of 2ꢀaminoꢀ3ꢀcyanoꢀ replaced the dimedone compound with 4ꢀhydroxyquinolone

pyrano[3,2ꢀc]quinolinꢀ5(4H)ꢀones in good to high yields, we in the same conditions (Scheme 5). In this case, the use of

turned our attention to the synthesis of 2ꢀaminoꢀ3ꢀcyanoꢀ7,8ꢀ dimedone, as an enolic component, improved the reaction

dihydroꢀ4Hꢀchromenꢀ5(6H)ꢀone under similar conditions. We time of the desired product 8 slightly.

O

R

O

X

O

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

X

NC

R

H

NH₂

X = CN (3a), COOEt (3b)

7

2

8

Scheme 5 One-pot three-component reaction of dimedone (7), different aldehydes (2) and malononitrile or ethyl

cyanoacetate (3a-b).

Table 4 Synthesis of derivatives of 2-amino-3-cyano-7,8-dihydro-4H-chromen-5(6H)-one (8) via condensation of dimedone

(7), various aldehydes (2) and malononitrile (3a) in the presence of (CTA)₃[SiW₁₄]-Li⁺-MMT ^a.

Time

(min)

M.P(Obsd)

(^oC)

M.P (Lit)

(^oC)

Carbon acid

(3) (X)

Entry

8a

RCHO (2)

Product

Yield%

O

H

O

3a (CN)

95

233ꢀ235

234ꢀ235^32d

CN

15

O

NH₂

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Cl

O

Cl

CN

O

8b

3a (CN)

97

95

213ꢀ215

198ꢀ200^32b

H

O

15

12

O

NH₂

Cl

214ꢀ216

215ꢀ217^32a

8c

O

H

CN

Cl

O

F

NH₂

O

3a (CN)

14

17

12

97

96

95

208ꢀ210

227ꢀ228

205ꢀ207

210ꢀ211^32d

228ꢀ230^32j

207ꢀ209³²ⁱ

8d

8e

H

CN

F

O

NH₂

Br

O

Br

H

CN

O

NH₂

Br

O

CN

8f

Br

O

NH₂

NO₂

O

O₂N

3a (CN)

11

93

89

215ꢀ217

181ꢀ183

214ꢀ216^32a

H

8g

CN

O

NH₂

NO₂

O

11

179ꢀ180^32c

8h

H

O

CN

O₂N

O

NH₂

CN

O

227ꢀ230³²ⁱ

220ꢀ222^32e

201ꢀ202^32d

8i

H

3a (CN)

13

20

22

91

89

226ꢀ228

219ꢀ221

200ꢀ202

CN

NC

O

NH₂

Me

O

8j

CN

H

Me

O

NH₂

OMe

O

H

8k

O

MeO

CN

O

NH₂

14 | J. Name., 2012, 00, 1-3

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OH

O

H

8l

O

3a (CN)

19

27

19

91

96

95

225ꢀ227

224ꢀ226^32d

238ꢀ240^32f

210ꢀ212^30g

CN

HO

O

NH₂

OH

OMe

O

MeO

HO

O

H

239ꢀ241

211ꢀ213

CN

8m

O

NH₂

N(CH₃)₂

O

H

O

8n

8o

CN

N

O

NH₂

O

S

O

H

3a (CN)

12

15

96

95

221ꢀ223

223ꢀ225

220ꢀ223^32g

224ꢀ226^32h

CN

NH₂

S

8p

8q

H

CN

O

N

NH₂

O

3a (CN)

15

45

87

88

213ꢀ215

150ꢀ152

214ꢀ216^32k

CN

N

O

NH₂

8r

8s

O

H

3b (COOEt)

151ꢀ153^32e

COOEt

NH₂

O

Cl

O

H

153ꢀ154^32e

O

3b (COOEt)

29

32

92

93

152ꢀ155

153ꢀ155

Cl

COOEt

NH₂

O

NO₂

O

O₂N

O

H

154ꢀ156^30g

COOEt

NH₂

8t

3b (COOEt)

O

Me

O

8u

O

H

151ꢀ152^30g

COOEt

NH₂

3b (COOEt)

45

89

149ꢀ151

Me

O

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^aReaction conditions: dimedone (1 mmol), aldehyde (1 mmol), malononitrile or ethyl cyanoacetate (1.1 mmol), water (5 mL, reflux), (CTA)₃[SiW₁₄]-Li⁺-MMT

(10 mg).

^bAll compounds are known and their structures were determined from their spectral data and melting points as compared with literature values.

^cThe yields refer to Isolated products

.

The scope of the present protocol was further surveyed with pyrano[2,3ꢀd]pyrimidineꢀ2,4(3H,5H)ꢀdiones

(14a−14f),

other C−Hꢀactivated acidic compounds such as 4ꢀhydroxyꢀ6ꢀ respectively in good to high yields (83−97%) within sensible

methylpyrone (9), 4ꢀhydroxyꢀ6ꢀmethylpyridone (10) and time frame (Scheme 6). However, the threeꢀcomponent

pyrimidineꢀ2,4,6ꢀtrione (11). All of the C−Hꢀactivated acids reaction of pyrimidineꢀ2,4,6ꢀtrione (11), as an cyclic 1,3ꢀ

9, 10 and 11 undergo smooth condensation under the reaction dicarbonyl, required longer reaction times compared to 4ꢀ

conditions providing the desired products, 2ꢀaminoꢀ3ꢀcyanoꢀ hydroxyꢀ6ꢀmethylpyrone (9), 4ꢀhydroxyꢀ6ꢀmethylpyridone

pyrano[4,3ꢀb]pyranꢀ5(4H)ꢀones (12a−12f), 2ꢀaminoꢀ3ꢀcyanoꢀ (10) under similar reaction conditions.

pyrano[3,2ꢀc]pyridineꢀ6(5H)ꢀones (13a−13f) and 1Hꢀ

NH₂

CN

OH

O

R

12

13

O

9

O

OH

NH₂

CN

O

(CTA)₃[SiW₁₄] -Li⁺-MMT

Water, Reflux

HN

CN

NC

R

H

N

H

10

O

R

O

3a

2

H

N

OH

NH₂

CN

O

HN

14

HN

O

N

H

O

R

O

11

Scheme 6 One-pot three-component reaction of C−H-activated acids (9-11), different aldehydes (2) and malononitrile (3a).

Table 5 Synthesis of derivatives of 2-Amino-3-cyano-4H-pyran (12-14) via condensation of C−H-activated acids (9-11), various

aldehydes (2) and malononitrile (3a) in the presence of (CTA)₃[SiW₁₄]-Li⁺-MMT ^a.

Time

(min)

M.P(Obsd)

(^oC)

M.P (Lit)

(^oC)

Carbon acid

(3) (X)

Entry

12a

RCHO (2)

Product

Yield%

NH₂

O

H

CN

O

3a (CN)

18

15

93

235ꢀ237

238-

236^33a

O

NH₂

O

CN

O

H

97

230

-

232

232-

231^33b

12b

Cl

O

Cl

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NH₂

O

CN

O

H

3a (CN)

15

20

95

96

85

222

-

224

219

223

211

225

-

223^33c

218^33c

220^33d

210^33e

12c

F

O

F

NH₂

O

CN

O

217

-

220-

H

12d

12e

Br

O

Br

NH₂

O

CN

O

H

221

-

222-

O₂N

O

NO₂

NH₂

O

CN

O

H

209

-

212-

12f

13a

MeO

O

OMe

NH₂

CN

O

3a (CN)

20

18

90

277ꢀ278

241ꢀ242

257ꢀ258

279ꢀ282³⁴

245ꢀ247³⁴

258ꢀ259^33c

H

N

H

O

NH₂

CN

O

93

H

13b

13c

N

H

O

Cl

F

NH₂

O

CN

O

H

92

93

N

H

O

F

NH₂

CN

O

3a (CN)

18

253ꢀ254

254ꢀ255^33c

H

13d

N

H

O

Br

NH₂

O

CN

O

278ꢀ279^33c

224ꢀ225³⁴

206ꢀ209^35a

H

3a (CN)

15

18

35

95

277ꢀ278

223ꢀ225

205ꢀ207

13e

13f

O₂N

N

H

O

NO₂

NH₂

O

CN

O

H

85

MeO

N

H

O

OMe

NH₂

O

CN

O

90

H

HN

14a

O

N

H

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Journal Name

NH₂

O

CN

O

H

3a (CN)

30

94

93

234ꢀ236

234ꢀ237^35b

14b

HN

Cl

O

N

H

O

Cl

NH₂

O

CN

O

H

HN

191ꢀ193

233ꢀ235

194ꢀ196^32k

14c

14d

F

O

N

H

O

F

NH₂

CN

O

HN

3a (CN)

30

91

235ꢀ236^35c

H

O

N

H

O

Br

NH₂

O

CN

O

H

3a (CN)

25

35

95

83

226ꢀ228

281ꢀ283

227ꢀ229^35b

14e

14f

HN

O₂N

O

N

H

O

NO₂

O

NH₂

CN

H

O

280^35d

MeO

HN

O

N

H

O

OMe

^aReaction conditions: 4-hydroxycoumarin (1 mmol), aldehyde (1 mmol), malononitrile or ethyl cyanoacetate (1.1 mmol), water (5 mL, reflux), (CTA)₃[SiW₁₄]-

Li⁺-MMT (10 mg).

^bAll compounds are known and their structures were determined from their spectral data and melting points as compared with literature values.

^cThe yields refer to Isolated products

.

We herein suggest a mechanism in Scheme 7 for oneꢀpot chlorophenyl)ꢀ3ꢀcyanoꢀpyrano[3,2ꢀc]chromeneꢀ5(4H)ꢀone

threeꢀcomponent condensation of various enols, aldehydes (4c). As shown in Figure 6, this nanocatalyst can be recycled

and active methylene nitriles catalyzed by (CTA)₃[SiW₁₄]ꢀ at least five times without significant decrease in catalytic

Li⁺ꢀMMT) in water. Firstly, cyanocinnamonitriles or ethyl activity, the yields ranged from 97% to 93%.

cyanocinnamates (15) was formed from the Knoevenagel

condensation reaction of aldehyde and malononitrile (or ethyl

cyanoacetate) in presence of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT. Then

product of the first step by Michael addition was reacted with

enolate of the C−Hꢀactivated acid (1, 5, 7, 9, 10 or 11) in

presence of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT to create Michael

adduct (16). The Michael adduct (16) tautomerizes and

cyclizes using (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT catalyst to form

intermediate (17) and which then tautomerized to give the

desired product (4, 6, 8, 12, 13 or 14).

In the next phase of study, the recovery and reuse cycle of

(CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT was also evaluated. Hence, we

investigated the recyclability of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT for

Fig.6 Reusability of the catalyst.

five consecutive cycles to afforded of synthesis 2ꢀaminoꢀ4 (4ꢀ

18 | J. Name., 2012, 00, 1-3

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ARTICLE

Furthermore, a comparative evaluation of the catalytic the synthesis of different 4Hꢀpyran derivatives (Table 6). It is

efficiency and the capability of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT obvious that a suitable methodology in terms of product yield,

were compared with some of the obtained results in this study reaction time and using green solvent to several of the others

with those methodologies, which have been reported using has been developed.

other earlier homogeneous and heterogeneous catalysts for

Conclusion

In conclusion, we have introduced a simple, facile, green and tedious separation procedures as well as reusability of the

conveniently practical oneꢀpot methodology for the synthesis reaction media are the most important advantages of the

of a wide range of biologically and pharmacologically present method. Considering that the synthetic significance of

interesting functionalized 2ꢀaminoꢀ4Hꢀchromenes in the such densely functionalized and biologically important 2ꢀ

presence of (CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT as a ecoꢀfriendly and aminoꢀ4Hꢀchromenes

scaffolds

directly

relate

to

reusable nanocatalyst via oneꢀpot Knoevenagel condensation pharmaceutical chemistry, the present strategy with green

of C−Hꢀactivated acids, aldehydes and malononitrile (or ethyl reaction conditions and easy workꢀup offers the possibility of

cyanoacetate) in water under reflux conditions. The use of its use with affordable and ecoꢀfriendly features as

costꢀeffective and ecoꢀfriendly catalyst, aqueous conditions, appropriate ways for the scaleꢀup of these oneꢀpot three

absence of hazardous organic solvents, operational simplicity, component reactions.

excellent yields, high atomꢀeconomy and avoidance of

T

A

)

[

S

i

W

NH₂

]

-

X

L

i

NC

O

-

O

R

M

H

T

R

X

3

2

(4, 6, 8, 12, 13, 14)

X

3

(

C

R

1

C

T

4

A

)

15

+

[

S

N

H

i

W

]

-

L

i

H

-

M

T

N

O

C

X

H

17

R

(1, 5, 7, 9, 10, 11)

HN

X

O

C

R

16

Scheme 7 A plausible mechanism for the one-pot three-component reaction of various enols (1, 5, 7,9, 10, 11), aldehydes (2)

and active methylene nitriles (3) catalyzed by (CTA)₃[SiW₁₄]-Li⁺-MMT in water.

Table 6 Comparison of the present method with other reported strategies for the synthesis of compound 4c.

Catalyst

loading

Temp

(°C)

Time Yield

Entry

Catalyst

Solvent

Ref.

(min)

150

6

(%)

88

93

94

93

96

1

2

3

4

5

SDS

CuO nanoparticles

DBU

20 mol %

15 mol %

10 mol %

5 mol %

H₂O

60

100

30a

36a

30h

30d

36b

100

5

TBAB

100

45

POPINO

Reflux

10

J. Name., 2013, 00, 1-3 | 19

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Journal Name

6

(CTA)₃[SiW₁₄]ꢀLi⁺ꢀMMT

10 mg

10 mol %

100 mg

H₂O

Reflux

100

25

6

97

This work

36c

7

Sꢀproline

DAHP

H₂O/EtOH

180

240

420

150

170

40

78

85

93

90

91

95

89

94

90

8

30g

9

Urea

25

32k

10

11

12

13

14

15

PBBS

H₂O/EtOH Reflux

36d

TBBDA

0.18 mmol

10 mol %

25 mol %

20mg

36d

Hexamethylenetetramine (HMT)

Nano Al₂O₃

EtOH

ꢀꢀꢀ

78

25

30j

300

15

36e

MNP@AVOPc

[Sipim]HSO₄

25

36f

0.08 mmol

ꢀꢀꢀ

100

30

36g

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(CTA)₃[SiW₁₄]-Li⁺-MMT: A Novel, Efficient and Simple Nanocatalyst for the

Facile and One-pot Access to Diverse and Densely Functionalized 2-amino-

4H-chromene Derivatives via an Eco-Friendly Multicomponent Reaction in

Water

Esmayeel Abbaspour-Gilandeh^*, Mehraneh Aghaei-Hashjin, Asieh Yahyazadeh, and Hadi Salemi

Article Doi

(CTA)3[SiW12]-Li+-MMT: A novel, efficient and simple nanocatalyst for facile and one-pot access to diverse and densely functionalized 2-amino-4H-chromene derivatives via an eco-friendly multicomponent reaction in water

DOI: 10.1039/c6ra09818e

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