Ultrasound promoted efﬁcient and green protocol for the expeditious

This article appeared in a journal published by Elsevier. The attachedcopy is furnished to the author for internal non-commercial researchand education use, including for instruction at the authors institution

and sharing with colleagues.

Other uses, including reproduction and distribution, or selling orlicensing copies, or posting to personal, institutional or third party

websites are prohibited.

In most cases authors are permitted to post their version of thearticle (e.g. in Word or Tex form) to their personal website orinstitutional repository. Authors requiring further information

regarding Elsevier’s archiving and manuscript policies areencouraged to visit:

http://www.elsevier.com/authorsrights

http://www.elsevier.com/authorsrights

Author's personal copy

Research paper

Ultrasound promoted efficient and green protocol for the expeditioussynthesis of 1, 4 disubstituted 1, 2, 3-triazoles using Cu(II) doped clayas catalyst

Bashir Ahmad Dar a, Amrita Bhowmik a, Amit Sharma b, Parduman R. Sharma a, Anish Lazar c, A.P. Singh c,Meena Sharma b,⁎, Baldev Singh a,⁎a Indian Institute of Integrative Medicine (CSIR), Canal Road Jammu, Indiab Department of Chemistry University of Jammu, (J & K) 180004, Indiac Catalysis Division, National Chemical Laboratory, Pune (Maharastra) 411008, India

a b s t r a c ta r t i c l e i n f o

Article history:Received 12 March 2013Received in revised form 16 May 2013Accepted 18 June 2013Available online 26 July 2013

Keywords:Copper catalystCatalyst supportSelectivitySustainabilityCrystallization

Cu(II) doped clay catalyst has been prepared by an easy technique from inexpensive starting materials andinvestigated for the one pot synthesis of 1, 4-disubstituted 1, 2, 3-triazoles via Huisgen [3 + 2] cycloadditionunder ultrasonic irradiation at room temperature. The catalyst is highly active, selective, and stable and canbe reused several times. The prepared catalyst has been characterized by XRD, BET-SA, H2-TPR, SEM andXPS techniques. This transformation is fast, efficient and does not require nitrogen atmosphere or anoxic con-ditions and additive.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

As a hallmark of click chemistry, Meldal Sharpless Cu(I)-catalyzedversion of the Huisgen (Huisgen, 1963) azide alkyne cycloaddition(CuAAC) reaction has received remarkable, almost explosive amplifica-tion of attention since its discovery independently by Meldal (Tornøeet al., 2002) and Sharpless(Hoogenboom, 2010; Kolb et al., 2001;Rostovtsev et al., 2002). CuAAC finds wide spread applications in broadrange of fields (Jason and Fokin, 2010; Katayama et al., 2009), becauseof its good atom efficiency, complete regioselectivity, and rapid kineticsunder mild reaction conditions (Altintas et al., 2012; Brantley et al.,2011). Susceptibility of copper (I) salts to redox processes desires the uti-lization of protecting agents and stabilizing ligands to protect and stabi-lize the active Cu(I) catalyst during CuAAC, which led to the discovery ofseveral modified procedures (Meldal and Tornoe, 2008), like using Cu(I)salts with nitrogen ligands (Doez-Gonzolez et al., 2006), iminopyridine(Mantovani et al., 2005), triphenylphosphine (Wu et al., 2004). Somealternatives have also been developed to generate Cu(I) in-situ likecomproportionation of a Cu(0)/Cu(II) couple (Appukkuttan et al., 2004)or reduction of Cu(II) to Cu(I) catalyst by using some reducing agents(Feldman et al., 2004). The problem of catalyst separation, requirementof reducing agents and stabilizing ligands in these homogeneous catalytic

systems restricts their utilization in practical processes. To overcomethese complications Cu(I) species immobilized onto various supportssuch as activated charcoal (Lee et al., 2009), Montmorillonite (Jlalia etal., 2008), zeolites (Beneteau et al., 2010; Chassaing et al., 2008, 2010),chitosan (Chtchcigrovsky et al., 2009), silica (Li et al., 2008) and IsonitrileComplex (Liu and Reiser, 2011) N-heterocyclic carbene (NHC) (Wang etal., 2011a), nano ferrite-glutathione (Baig and Varma, 2012) etc. havebeen employed. However, these heterogeneous systems retain ther-modynamic instability of Cu(I) (Adzima et al., 2011). Furthermore,anhydrous organic solvents, inert atmosphere and tedious catalystpreparation techniques are usually required for these catalyst systemsto attain stabilization and high reactivity (Wang et al., 2011b). There-fore development of an efficient, simple, robust, cleaner and greenerheterogeneous catalytic system with high stability is highly demanded.Nevertheless, most of the reported CuAAC methods involve two-component azide and alkyne reaction systems. Organic azides beingconsidered explosive in nature; their preparation, isolation, purifica-tion or storage is very difficult. Thus one-pot procedure for the synthesisof 1, 4-disubstituted 1, 2, 3-triazoles from a halide, sodium azides andalkyne is rapid, inexpensive and easily by-passing the safety issuesassociated with the handling of potentially explosive azides (Bolla etal., 2011; Scriven and Turnbull, 1988; Zhao et al., 2006). In continuationof our research interest for eco-friendly organic transformations (Daret al., 2012a, 2013), we herein report Cu(II) doped Clay as a novel, envi-ronmentally benign, recyclable, efficient, and heterogeneous catalyst

Applied Clay Science 80–81 (2013) 351–357

⁎ Corresponding authors. Tel.: +91 191 2572002; fax: +91 191 2548607.E-mail address: [email protected] (B. Singh).

0169-1317/$ – see front matter © 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.clay.2013.06.030

Contents lists available at ScienceDirect

Applied Clay Science

j ourna l homepage: www.e lsev ie r .com/ locate /c lay


for the one pot synthesis of 1, 2, 3-triazoles via a three-component reac-tion of benzyl or alkyl halides, sodium azide and terminal alkynes, with-out using sacrificial reducing agents or ligands (using H2O:EtOH(1:1)mixture as solvent) under ultrasonic conditions at room temperature.Application of ultrasound irradiation along with heterogeneous Cu(II)catalyst makes this protocol far more advantageous than the earlier re-ported methods, which usually suffer from long reaction times even atelevated temperature. Ultrasound irradiation has been well establishedenergy source to promote chemical reactions (Cella and Stefani, 2009;Cravotto and Cintas, 2006; Dar et al., 2012b; Driowya et al., 2012;Mason, 1997). Many homogeneous and heterogeneous reactions can beconducted smoothly by sonication under milder conditions and shorterreaction times to afford improved yields and increased selectivities(Ding et al., 2007). Ultrasound irradiation has some potential effectson a heterogeneous catalytic system, like increase of active catalystsurface area, promotion of cavitation bubble formation and removal ofimpurities deposited on the catalyst (Kim et al., 2007). The cavitationalenergy induced by ultrasonication, augments both mass transfer andelectron transfer from the catalyst surface to the organic substrate andfacilitates the catalyst reactant interaction (Cintas et al., 2010; Cravottoet al., 2010). Clays and modified clays have received substantial con-sideration as heterogeneous catalysts in organic synthesis because oftheir high catalytic activity, environmental compatibility and reusability(Nagendrappa, 2011). Due to their typical layer structure and the excel-lent intercalation properties, clays have a great potential to host metalsand metal oxides (Gao and Xu, 2006). Inspired by these properties ofclays we prepared the Cu(II) doped clay catalyst (CDC) using commer-cially availableMontmorillonite KSF and studied its catalytic activity forultrasound promoted one pot synthesis of triazoles.

2. Experimental

2.1. General remarks

All chemicals were obtained from Sigma-Aldrich Company andused as received. NMR spectra were recorded on Brucker-AvanceDPX FT-NMR 400 MHz instrument. ESI-MS and HRMS spectra were

recorded on Agilent 1100 LC and HRMS-6540-UHD machines. Thesurface area and the reducible character of catalyst were determinedby Chembet-3000 TPR/TPD/TPO instrument. XRD spectra and scan-ning electron micrograph were obtained on D-8 ADVANCE (BRUKERAXS, Germany) and Jeol.JEM100C-XII electron microscope respectively.XPS analysis was performed on a KRATOS-AXIS 165 instrument.

2.2. Preparation of Cu(II) doped clay catalyst (CDC)

Cu(II) doped clay catalyst was prepared by suspendingMontmorillonite-KSF (10 g) with cation exchange capacity of120 meq./100 g clay in 200 ml distilled water and the suspensionwas vigorously stirred at room temperature for 30 min. Copperoligomer (base hydrolyzed cupric chloride with OH/Cu molar ratio of2.0) was added drop wise to prepare 10 wt.% copper loading (pre-optimized loading) on to Montmorillonite KSF clay and the systemwas stirred for 15 h followed by filtration and then washed with dis-tilled water several times to remove chlorides. The cake so formedwas dried at room temperature, kept overnight in air oven at 110 °Cand then powdered and calcined at 425 °C for 3 h. The calcined productis referred to as Cu(II) doped clay catalyst (CDC 2) and the catalyst soformed was used in the experiments without further activation.

2.3. CDC catalyzed one-pot synthesis of 1, 2, 3-triazoles

2.3.1. Typical procedure for one-pot synthesis of 1, 2, 3-triazolesOrganic halide (1 mmol) and sodium azide (2 mmol) and the alkyne

(1.1 mmol) were added to a suspension CDCC (2 mol%) in 1 ml of EtOH:H2O (1:1) in a 5 ml glass test tube (Scheme 1) and subjected to ultrasonic

+ NaN3H2O:EtOH, rt,15 min.

Br

+ N

NNCu(II)-Clay ))))))))

1a 2 3a 4a

Scheme 1. Cu(II) doped clay catalyzed one pot synthesis of 1, 4 disubstituted 1,2,3-triazoles.

Table 1Optimization of reaction under ultra-sonication.

Entry Catalyst (mol%) Solvent Time (min) Yielda (%)

1 CDC 1(20) Water 30 612 CDC 2(20) Water 15 873 CDC 3(20) Water 15 724 CDC 4(20) Water 30 575 CDC 2(15) Water 15 866 CDC 2(10) Water 15 867 CDC 2(5) Water 15 598 CDC 2(10) Solvent free 60 99 CDC 2(10) Tetrahydrofuran (THF) 15 4310 CDC 2(10) Dimethylformamide 15 1111 CDC 2(10) Toluene 15 212 CDC 2(10) Dichloromethane 15 213 CDC 2(10) Ethanol 15 8414 CDC 2(10) Water:ethanol 15 9815 CDC 2(10) Water:methanol 15 9816 CDC 2(10) Acetonitrile 15 8117 CDC 2(10) Methanol 15 82

a Isolated yield.

Table 2Effect of different reaction conditions on the model reaction.

Entry Condition Solvent Time Yielda (%)

1 Without sonication EtOH:H2O 17 h 682 Without sonication No solvent 18 h 173 Sonication No solvent 60 min 94 Sonication without catalyst EtOH:H2O 7 h Traces5 Reflux without sonication EtOH:H2O 2 h 336 Reflux, no catalyst, no sonication EtOH:H2O 2 h Traces7 Sonication with catalyst EtOH:H2O 15 min 98

EtOH:H2O = (1:1).a Isolated yield.

Table 3Comparison of catalytic activity of Cu doped clay catalyst with other Cu catalysts.

S. no. Catalyst Mol% of catalyst Solvent Time % yielda

1 CuNi/clay 10 EtOH:H2O 30 min 602 CuMn/clay 10 EtOH:H2O 30 min 643 CuZn/clay 10 EtOH:H2O 30 min 724 CuAl/clay 10 EtOH:H2O 30 min 635 CuFe/clay 10 EtOH:H2O 30 min 716 CuSn/clay 10 EtOH:H2O 30 min 627 CuCo/clay 10 EtOH:H2O 30 min 678 CuO 10 EtOH:H2O 30 min 549 Cu2O 10 EtOH:H2O 30 min 56

a Isolated yield.

352 B.A. Dar et al. / Applied Clay Science 80–81 (2013) 351–357


irradiation at room temperature for specified time duration using aBandelin Sonorex Super RK 510 Hultrasonic bathwith Inner tank dimen-sions l × w × d: 300 × 240 × 150 mm, Exterior dimensions l × w × h:325 × 265 × 305 mm, Frequency: 35 kHz and Ultrasonic peak output:640 W*. The completion of reaction was monitored by TLC. The reactionmixturewasfiltered throughWhatmanfilter paper. Filtratewas extractedwith EtOAc (3 × 50 mL) and dried over anhydrous sodium sulfate. Com-bined organic layer was concentrated in vacuo. The crude product thus

obtained was purified by the process of crystallization. The spectral data(1H, C13 NMR) of all the products obtained were confirmed by compari-son with spectra of the authentic samples reported in the literature.

Spectral data of some representative compounds are given below.

2-((1-benzyl-1H-1, 2, 3-triazol-4-yl)methyl)isoindoline-1,3-dione1HNMR (400 MHz CDCl3); δ = 4.96 (s, 2H), 5.47 (s,2H), 7.24-7.71(m, 10H)

Table 4Synthesis of 1, 4-disubstituted 1, 2, 3-triazoles with different alkyl halides,terminal alkynes, and sodium azidea.

Entry Halide Alkyne Product Time (min) Yield (%)b

1 15 98

2 25 94

3 25 86

4 30 84

5 30 95

6 20 91

7 25 90

8 20 95

9 25 86

10 35 83

11 35 81

12 30 85

a = Reaction conditions as exemplified in the typical experimental procedure.b = Isolated yields.

353B.A. Dar et al. / Applied Clay Science 80–81 (2013) 351–357


13C-NMR (100 MHz CDCl3); δ = 33.51, 55.10, 123.13, 123.52,128.33, 128.69, 129.21, 132.15, 134.21, 134.39, 143.24, 167.551-(1-benzyl-1H-1, 2, 3-triazol-4-yl)-1-phenylethanol1HNMR (400 MHz, CDCl3); δ = 1.97 (s, 3H), 3.08 (s, 1H), 5.47 (s, 2H),7.21-7.38 (m, 11H)C13 NMR (125 MHz, CDCl3); δ = 30.72, 54.18, 72.14, 120.41, 125.21,127.91, 128.09, 128.22, 128.77, 129.14, 134.52, 146.47, 155.35

3. Results and discussion

At the onset of this work one reaction between benzyl bromide(1a), sodium azide (2) and phenyl acetylene (3a) to the triazoles(4a) was selected as model reaction. Cu(II) doped Montmorillonite-KSF catalysts with copper loading of 5 wt.% (CDC 1), 10 wt.% (CDC 2),15 wt.% (CDC 3) and 20 wt.% (CDC 4) were prepared and investigatedfor this reaction to screen the optimum copper loading. CDC 2 catalyst(10 wt.% copper loading) proved to be the best in EtOH: H2O (1:1)under ultrasound radiations. The desired triazole 4a (Scheme 1) wasobtainedwithin 15 min. with 98% yield (monitored by TLC) and the op-timum quantity of this catalyst was (10 mg) (Table 1, entry 14). Whenthe reaction was performed in solvent free conditions merely 8–9%yield was observed even after 60 min. (Table 1, entry 8). Poor yieldswere also obtained in organic solvents viz. toluene, DCM, DMF andTHF (Table 1, entries 9–12). The reaction in acetonitrile medium

produced corresponding triazole with 81% yield in 15 min. (Table 1,entry 16), but we encountered difficulty in catalyst recovery with theuse of ACN solvent. Reaction yields were more (82–87%) when polarprotic solvents were used (Table 1, entries 1–6, 13 and 17). The combi-nation ofwater: ethanol (1:1), was found to be the bestmedium for thisreaction (Table 1, entry 14), where the reaction yield was enhanced to98%. This may be due to the increased miscibility and hence enhancedcollision rate between the reactants. Similar results were obtained insolvent system composed of H2O-MeOH (1:1) (Table 1, entry 15), butwater: ethanol (1:1) combination was recommended in order to attainoptimum results in greener medium.

We conducted the reaction under ultrasonic irradiation inH2O-EtOHwithout using the catalyst; only traces of product were observed after7 h (Table 2, entry 4). When the catalyst was tried for the model re-action without sonication at room temperature with constant stir-ring for 17 h the yield of the triazole obtained was found to be 68%(Table 2, Entry1) and only 17% under solvent free conditions evenafter 18 h (Table 2, entry 2). The activity of the catalyst was foundto be very less under reflux conditions also, where the model reactionyielded only 33% with solvent (H2O-EtOH 1:1) and mere traces in sol-vent free conditions (Table 2, entries 5 and 6 respectively). When themodel reaction was performed in the absence of solvent for 60 min,only 9% of the 4a was obtained (Table 2, entry 3). Thus there may besynergistic relation between the catalyst, the solvent and ultrasonicirradiation (Tornøe et al., 2002).

Comparing the catalytic activity of the catalyst with some claysupported copper bimetallic catalysts (prepared for this study) andcommercially available CuO and Cu2O for the model reaction underoptimized conditions, we found that combining other metals to Cu(II)could not improve the activity of the catalyst and no improvement inthe results was observed upon using copper bimetallic clay catalysts in-stead somedecreased yieldswere obtained (Table 3, entries 1–7). Cu(II)doped clay catalyst was also found to show much better results thancommercially available CuO and Cu2O (Table 3, entries 8 and 9). Thismay be due to high dispersion and the nanosized character of Cu(II)ions on clay support (Alonso et al., 2010a,b).

After optimization of reaction conditions, the scope of this proto-col was explored for an assortment of alkyl halides and alkynes(Table 4).

It was observed that excellent yields of the triazole products wereformed with different reaction times. The reaction time was found todependent on the type of alkyl halide as well as on the type of alkynesused. Benzyl bromide furnished the respective triazoles in shorterreaction time irrespective of type of alkynes used (Table 4, entries 1–4,8, 9). However, the reaction of Benzyl Chloride required 30 min for

Fig. 1. Recyclability of the catalyst for one pot synthesis of 1, 4-disubstituted 1, 2,3-triazolesa. a = Model reaction.

Fig. 2. TPR curves of CDCC.



completion (Table 3, entry 5). Reaction of aliphatic alkynes completed inlonger reaction times irrespective of alkyl halide used (Table 4, en-tries 9–12). The methodology also proved to be effective for alkynesother than phenylacetylene and simple aliphatic alkynes, such asN-propargylphtalimide (Table 4, entry 3) or 4-NO2-phenyl propargylether (Table 4, entry 4). All the compounds so prepared were stableand were characterized by NMR, and MS analysis.

Recyclability of the catalyst was investigated using model reactionbetween benzyl bromide (1a), sodium azide (2) and phenylacetylene(3a). The catalyst could be easily recovered by simple filtrationand reused; leading to triazole (4a) in quantitative yield even up to sixconsecutive cycles (Fig. 1). This experiment proved excellent recyclingcapability of the catalyst without significant loss of activity.

[1] The reducible character of catalyst was determined byCHEMBET-3000 TPR/TPD/TPO instrument, containing a quartz reactor

(i.d. = 4 mm) and a T.C.D. detector. The H2 TPR curves of the catalyst(Fig. 1) show three reduction peaks, a major peak centered at 225 °C,small broad shoulder at 370 °C and a small broad peak at 540 °Cwhich indicates stepwise reduction of Cu2+. The large signal peakat 225 °C can be attributed to the reduction of highly dispersedsmall CuO particles to Cu1+ and the small peak at 370 °C is assignedto the reduction of bulk Cu1+ to Cu0+. The small broad peak at and540 °C is attributed to reduction of iron impurities present in theclay (Ben Achma et al., 2008; Mishra et al., 2008; Oubagaranadinand Murthy, 2010).

To know the surface area of the catalyst nitrogen adsorption anddesorption were determined at −196 °C by means of an automatedCHEMBET-3000 adsorption apparatus.

Specific surface areas were calculated. Samples were pretreated inhigh vacuum at 200 °C for 2 h.

Fig. 3. The comparative XRD spectrum of fresh and used catalyst.

Fig. 4. A. SEM image of Montmorilonite-KSF. B. SEM image of Cu(II) doped Montmorilonite-KSF.



Total specific area Montmorillonite-KSF clay = 37 m2/gSupported Montmorillonite-KSF = 96 m2/gThe surface area analysis indicates that the pillaring process produces

a significant increase in the surface area from 37 m2/g corresponding tothe original clay to 96 m2/g corresponding to the Cu(II) doped clay(Table 2), might be due to the formation of microspores.

The powder X-ray diffraction patterns of the fresh catalyst (A) andafter 6th cycle (B) were recorded using a D-8 ADVANCE (BRUKERAXS, Germany) X-ray diffractometer using Ni filter and Gobel Mirrorparallel beam geometry (CuKα: λ = 0.15418 nm) in the 2θ range10–75° in step scan mode (Step Size: 0.02°, Scan Speed: 2 s/step).The phases are identified by search match procedure with the helpof DIFFRACPLUS software using JCPDS databank. The phases are iden-tified with the 2θ values like; shown in Fig. 2.

The presence of very low intensity diffraction peaks at 2θ = 36.1,37.7, 38.9, 48.8, 53.60 and 58.7 attributing to (110), (002), (111),(202) of CuO indicates that there are no sharp crystalline phases, in-dicating that CuO is supported on MKSF in the form highly dispersedfine particles. These results are in close agreement with TPR studiesmentioned above. Peaks at 2θ of 20.9, 26.9, 36.5, 39.2, 48.6, 50.0 and59.6 are due to reflection of the quartz [SiO2] impurities. The 2θ at

8.7 is a characteristic peak of basal spacing (d 001) (2:1 TOT) of Mont-morillonite KSF. Other peaks for Montmorillonite appear at 2θ of 20.0,24.3, 29.8 and 35.5. A sharp peak observed at 2θ of 17.8 along withsome small peaks at 30.1, 36.0 and 47.2 correspond to the presenceof Melanothallite [Cu2OCl2]. Presence of Kaolinite is implied to asharp peak at 12.0 which corresponds to (001) and other peaks forthis material appear at 24.1, 32.3, 38.0, and 42.7. The remainingpeaks at 229.5, 32.3, 41.5, 45.5, 55.0 and 59.6 are due to the formationof CuAl2O4. There are two additional humps one at 55.0 and other at61.9 which are due to Montmorillonite and CuO in bulk respectively.By comparison of XRD patterns for the fresh catalyst with used cata-lyst (Fig. 3), it is clear that there is almost no variation in the catalyst.

To study the morphology, SEM of the catalyst was carried outusing JEOL.JEM100CXII ELECTRON MICROSCOPE with ASID Accelerat-ing Voltage 40.0 kV. The SEM images of the Montmorillonite-KSF andcopper doped Montmorillonite-KSF with 20000 magnifications aredisplayed in Fig. 4. From this study it is clear that after copper loadingthe smooth surface of the clay turns patchy so it is confirmed that theCuO particles are highly dispersed over the support surface in theform of nano aggregates. The nanosized CuO distributed in mosaicform on the surface of the clay leads to coarse surface (thus elevated

Fig. 5. XPS spectra of Cu(II) doped Montmorilonite-KSF.

R

H+

R1 X

CuClayCuClay R

NaN3

CuClay R

NR1

N

CuClayN3 R1

N+ _

CuClay

NN

N

R

R1

H+

NN

N

R

R1

Step 1

Step 2A

Step 2B

Step 3

Step 4

Scheme 2. Plausible mechanism of one-pot CuAAC protocol using Cu(II) doped Montmorilonite-KSF catalyst.



surface area). From the SEM (EDAX) elemental analysis it was foundthat the catalyst prepared contains 9.21% of copper loaded.

XPS is a surface technique which provides valuable informationabout the oxidation state and chemical environment of atoms dueto the shift in binding energies. Fig. 5 shows the high resolution nar-row X-ray photoelectron spectra (XPS) for fresh clay supported Cu(II)catalyst, recorded to know the oxidation state of Cu. As observed inthis figure, binding energy peaks at 935.6 eV and 955.3 eV can be at-tributed to 2p3/2 and 2p1/2 spin–orbit split-doublets, respectively,which are characteristic of Cu in 2 oxidation state.

By analogy with previous reports, a stepwise mechanism (Scheme 2)involving an initial copper (I) acetylide is formation which proba-bly occurs through a π-alkyne copper complex intermediate. Thisπ-coordination of alkyne to copper activates the terminal hydrogenof the alkyne to be deprotonated in the aqueous medium to form aσ-acetylide (Step 1). The alkyl or benzyl azide [in situ formation(Step 2A)] is then activated by coordination to copper formingintermediate (Step 2B). The coordination event is synergistic for bothreactive partners. Coordination of the azide reveals the β-nucleophilic,vinylidene-like properties of the acetylide, whereas the azide's termi-nus becomes even more electrophilic and a strained copper triazolideis formed (Step 3). Protonation of the triazole–copper derivative follow-ed by dissociation of the product completes the reaction and regener-ates the catalyst (Step 4). The presence of basic and acidic sites onmontomorillonite-KSF assists the formation of acetylide and proton-ation of the triazole–copper respectively. There is no experimental evi-dence to support this proposal.

4. Conclusion

In conclusion, we have described heterogeneous Cu(II) catalyzedone-pot synthesis of 1, 2, 3-triazoles regioselectively under ultrasoundirradiation at room temperature. The catalyst is easy to prepare, envi-ronmentally benign, highly stable, and leaching-free. This catalyst canbe recycled several timeswithout significant loss of activity. The reactionis easy to handle, fast and involves Cu(II) instead of unstable Cu(I) ingreen solvent system under ligand-free and base free conditions. More-over, being fast and high yielding this protocol will be highly useful foreconomical synthesis of 1, 4-disubstituted 1, 2, 3-triazoles. From thisstudy it is obvious that instead of unstable Cu(I) species a more stableCu(II) can directly be used for one pot synthesis of 1, 2, 3-triazoles.

Acknowledgment

We are grateful to the Director Indian Institute of IntegratedMedicine (IIIM), Canal Road, Jammu for providing necessary facilitiesand good environment to carry out the research work. We are alsothankful to CSRI-DELHI for the financial support.

References

Adzima, B.J., Tao, Y., Kloxin, C.J., DeForest, C.A., Anseth, K.S., Bowman, C.N., 2011. NatureChemistry 3, 256.

Alonso, F., Moglie, Y., Radivoy, G., Yus, M., 2010a. Advanced Synthesis and Catalysis352, 3208.

Alonso, F., Yus, M., Radivoy, G., Moglie, Y., 2010b. European Journal of Organic Chemistry1875.

Altintas, O., Vogt, A.P., Barner-Kowollik, C., Tunca, U., 2012. Polymer Chemistry 3, 34.Appukkuttan, P., Dehaen,W., Fokin, V.V., van der Eycken, E., 2004. Organic Letters 6, 4223.Baig, R.B.N., Varma, R.S., 2012. Green Chemistry 14, 625.Ben Achma, R., Ghorbel, A., Sayadi, S., Dafinov, A., Medina, F., 2008. Journal of Physical

Chemistry of Solids 69, 1116.Beneteau, V., Olmas, A., Boningari, T., Sommer, J., Pale, P., 2010. Tetrahedron Letters 513673.Bolla, K., Kim, T., Song, J.H., Lee, S., Hama, J., 2011. Tetrahedron 67, 5556.Brantley, J.N., Wiggins, K.M., Bielawski, C.W., 2011. Science 333, 1606.Cella, R., Stefani, H.A., 2009. Tetrahedron 65, 2619.Chassaing, S., Sido, A.S.S., Alix, A., Kumarraja, M., Pale, P., Sommer, J., 2008. Chemistry —

A European Journal 14, 6713.Chassaing, S., Alix, A., Boningari, T., Sido, K.S.S., Keller, M., Kuhn, P., Louis, B., Sommer, J., Pale,

P., 2010. Synthesis 1557.Chtchcigrovsky, M., Primo, A., Gonzalez, P., Molvinger, K., Robitzer, M., Quignard, F.,

Taran, F., 2009. Angewandte Chemie 121, 6030.Cintas, P., Barge, A., Tagliapietra, S., Boffa, L., Cravotto, G., 2010. Nature Protocols 5,607.Cravotto, G., Cintas, P., 2006. Chemical Society Reviews 35, 180.Cravotto, G., Fokin, V.V., Garella, D., Binello, A., Boffa, L., Barge, A.J., 2010. Journal of

Combinatorial Chemistry 12, 13.Dar, B., Singh, A., Sahu, A., Patidar, P., Chakraborty, A., Sharma, M., Singh, B., 2012a.

Tetrahedron Letters 53, 5497.Dar, B., Sharma,M., Singh, B., 2012b. Bulletin of Chemical Reaction Engineering & Catalysis

7, 79.Dar, B., Sahu, A.K., Patidar, P., Sharma, P.R., Vyas, D., Maity, S., Sharma, M., Singh, B.,

2013. Journal of Industrial and Engineering Chemistry 19, 407.Ding, L.Q., Wang, W., Zhang, A.Q., 2007. Ultrasonics Sonochemistry 14,563.Doez-Gonzolez, S., Correa, A., Cavallo, L., Nolan, S.P., 2006. European Journal of Chemistry

12, 7558.Driowya,M., Puissant, A., Robert, G., Auberger, P., Benhida, R., Bougrin, K., 2012. Ultrasonics

Sonochemistry 19, 1132.Feldman, A.K., Colasson, B., Fokin, V.V., 2004. Organic Letters 6, 3897.Gao, X., Xu, J., 2006. Applied Clay Science 33, 1.Hoogenboom, R., 2010. Angewandte Chemie 49, 3415.Huisgen, R., 1963. Angewandte Chemie 75, 604.Jason, E.H., Fokin, V.V., 2010. Chemical Society Reviews 39, 1302.Jlalia, I., Elamari, H., Meganem, F., Herscovici, J., Girard, C., 2008. Tetrahedron Letters 49, 6756.Katayama, T., Kamata, K., Yamaguchi, K., Mizuno, N., 2009. ChemSusChem 2, 59.Kim, J.K., Martinez, F., Metcalfe, I.S., 2007. Catalysis Today 124, 224.Kolb, H.C., Finn, M.G., Sharpless, K.B., 2001. Angewandte Chemie 113, 2056.Lee, C.T., Huang, S., Lipshutz, B.H., 2009. Advanced Synthesis and Catalysis 351, 3139.Li, P., Wang, L., Zhang, Y., 2008. Tetrahedron 64, 10825.Liu, M., Reiser, O., 2011. Organic Letters 13,1102.Mantovani, G., Ladmiral, V., Tao, L., Haddleton, D.M., 2005. Chemical Communications 2089.Mason, T.J., 1997. Chemical Society Reviews 26, 443.Meldal, M., Tornoe, W., 2008. Chemical Reviews 108, 2952.Mishra, T., Mohapatra, P., Parida, K.M., 2008. Applied Catalysis B: Environmental 79, 279.Nagendrappa, G., 2011. Applied Clay Science 53,106.Oubagaranadin, J.U.K., Murthy, Z.V.P., 2010. Applied Clay Sciences. 50,409.Rostovtsev, V.V., Green, L.G., Fokin, V.V., Sharpless, K.B., 2002. Angewandte Chemie

114, 2708.Scriven, E.F.V., Turnbull, K., 1988. Chemical Reviews 88, 297.Tornøe, C.W., Christensen, C., Meldal, M.J., 2002. Journal of Organic Chemistry 67, 3057.Wang, W., Wu, J., Xiaa, C., Li, F., 2011a. Green Chemistry 13, 3440.Wang, Y., Liu, J., Xia, C., 2011b. Advanced Synthesis and Catalysis 353, 1534.Wu, P., Feldman, A.K., Nugent, A.K., Hawker, C.J., Scheel, A., Voit, B., Pyun, J., Frochet,

J.M., Sharpless, K.B., Fokin, V.V., 2004. Angewandte Chemie 116, 4018.Zhao, Y., Yan, Z., Liang, Y., 2006. Tetrahedron Letters 47, 1545.


Ultrasound promoted efﬁcient and green protocol for the expeditious

Documents

Transcript of Ultrasound promoted efﬁcient and green protocol for the expeditious