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Nov 28, 2016 - 1 Introduction. The concept of “click” chemical reactions was described by Sharpless, the copper(I)-catalyzed azide–alkyne cyclo-addition ...
J Inorg Organomet Polym (2017) 27:215–224 DOI 10.1007/s10904-016-0465-9

Silver and Copper-Supramolecular Coordination Polymers Inspired Alkyne–Azide Click Reactions Safaa Eldin H. Etaiw1 · Ibrahim A. Salem1 · Alaa Tawfik1 

Received: 26 September 2016 / Accepted: 1 November 2016 / Published online: 28 November 2016 © Springer Science+Business Media New York 2016

Abstract Two 3D-supramolecular coordination polymers (SCP); {[SnMe3(bpe)] [Ag(CN)2].2H2O}, 1, (bpe) = 1,2-bis(4-pyridyl)ethane and {[CuI(CN)(phen)2] [CuII(CN)2(phen)]·5H2O}, 2, (phen) = phenanthroline, have been synthesized and characterized by physicochemical and spectroscopic methods. The SCP 1 and 2 exhibit good catalytic activity for the formation of substituted triazoles (1-benzyl- 4-bromomethyl triazole and 1-benzyl4-phenyl triazole) in 98–100% yield. Of the factors investigated, the ratio of reactants and the amount of catalyst had the largest impact on yield. The use of the SCP 2 reduced by sodium ascorbate gave generally higher yields than a direct source of Cu owing to the high degree of efficiency. The general utility of the catalyst 1 and 2 indicated the formation of 1,4-substituted 1,2,3-triazoles in very good yield at shorter time in direct comparison to reactions performed in the presence of catalysts Cu(OAc)2 and AgNO3. In this case, the SCP 1 and 2-catalyzed alkyne–azide cycloaddition provide 1,4-disubstituted 1,2,3-triazoles with such efficiency and scope that the transformation has been described as “click” chemistry. Keywords Supramolecular coordination polymers · Click reactions · Copper · Silver · Azide · Alkyne

Electronic supplementary material The online version of this article (doi:10.1007/s10904-016-0465-9) contains supplementary material, which is available to authorized users. * Safaa Eldin H. Etaiw [email protected]; [email protected] 1

Department of Chemistry, Faculty of Science, University of Tanta, Tanta 31527, Egypt

1 Introduction The concept of “click” chemical reactions was described by Sharpless, the copper(I)-catalyzed azide–alkyne cyclo-addition (Cu-AAC: i.e., the copper-catalyzed Huisgen cyclo-addition) reaction has emerged as the most extensively investigated and applied [1, 2]. This reaction permits the chemo-selective, regiocontrolled conjugation of a functionalized alkyne to a functionalized azide yielding 1,4- or 1,4,5-substituted 1,2,3-triazoles and occasionally1,5-regioisomer [3–5]. Also, the CuIcatalyzed 1,3-dipolar cycloaddition of azide and alkyne to form a triazole was established recently as an important tool for the chemical and biological modification of biomolecules [1, 2]. The reactants, azide and alkyne, are convenient to introduce independently, are stable, and do not react with common organic reagents or functional groups in biomolecules. The triazole formation is irreversible and usually proceeds with high yield. In addition, this reaction benefits from an extremely mild and regioselective copper(I) catalyst system that is surprisingly indifferent to solvent and pH [6]. All these factors allow the application of “click chemistry” in many areas ranging from functional materials, drug discovery, biological, and hybrid bio-conjugate areas which have increased exponentially over the last decade [7–10]. Among the catalysts used are the silver and copper complexes which have been shown to act as mild π acids, thus effectively promoting the cyclo-addition of azides onto terminal alkynes [11–14]. Herein, we propose two versatile supramolecular coordination polymers (SCP) to be used as catalysts in Huisgen 1,3-dipolar cycloaddition of azides and alkynes for the preparation of substituted triazols. The supramolecular coordination polymers are a quite active research field because of their intriguing structural

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motifs and their wide potential applications [15–20]. In addition, the supramolecular catalysts are stable, welldefined non-solvated materials, and soluble in most organic-aqueous solvents, thus making them attractive homogeneous alternatives to copper and silver salts for potentially promoting the formation of 1,2,3-triazole.To test this hypothesis,{[SnMe3(bpe)][Ag(CN)2]·2H2O} 1, and {[CuI(CN)(phen)2][CuII(CN)2(phen)]·5H2O} 2, were prepared and characterized. Rigidity and planar structure of phenanthroline (phen) makes it an entropically better chelating molecule while 1,2-bis(4-pyridyl)ethane (bpe) acts as angular bipodal spacer ligand creating diverse topologies [21–23]. Thus, supramolecular self-assembly was used to design silver or copper cyanide SCP containing bpe or phen [24, 25], which have been carried out at room temperature between [M(CN)4]3− (M=Ag or Cu) building blocks and bpe or phen in presence of Me3SnCl. The catalytic reactivity of the SCP 1 and 2 toward azidealkyne cyclo-addition reactions was evaluated, where, for the first time, supramolecular catalysts were used for 1,2,3-triazoles formation at room temperature.

2 Experimental 2.1 Materials and Physical Measurements All chemicals and solvents used in this study were of analytical grade supplied by Aldrich or Merck and used as received. Microanalyses (C, H, N) were carried out with a Perkin Elmer 2400 automatic elemental analyzer. The infrared (IR) spectra were recorded on Perkin Elmer 1430 Ratio Recording Infrared Spectrophotometer as KBr discs. The nuclear magnetic resonance (NMR) spectra were measured using a 500-MHz AVANCE NMR spectrometer (Model DMX400), using DMSO-d6 as solvent. X-ray powder diffraction patterns were recorded using a Diang Corporation diffractometer equipped with CoKa radiation operated at 45 kV, 9 mA. The magnetic susceptibility was determined with Johnson-Matthey susceptometer.

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2.3 Synthesis of Triazole Derivatives To prepare the triazole derivatives benzyl azide is needed which was carried out according to the literature procedure [1]. Many different factors affect the yield of triazoles such as concentration of azide and alkyne, catalyst amount, time and temperature. To optimize design of an existing process, it is necessary to identify which factors have the greatest influence and which values produce the most consistent performance. Thus, the effect of azide and alkyne concentrations (1 and 2 equiv.), catalyst amount (0.025, 0.05, 0.1, 0.15 equiv.), time and temperature have been investigated to apply the best conditions to obtain 100% yield triazoles. The product of triazole was monitored during the course of the reaction by TLC until total conversion of the starting materials and detection was made by shining UV Light. Disappearance of the spots of azide and alkyne indicated 100% yield of triazole. 2.4 Synthesis of 1-Benzyl-4-Bromomethyl Triazole Propargyl bromide (1 equiv. 0.09  g) and (2 equiv. 0.18  g), benzyl azide ((1 equiv. 0.12 mL) and (2 equiv. 0.24 mL)) and the catalyst (0.025, 0.05, 0.1, 0.15 equiv.) were mixed in presence of acetonitrile and water mixture (1:1, 20 mL). The mixture was stirred at room temperature or with heating until reaction completion and then filtered off. Dichloromethane was added to the filtrate and the organic layer was separated and the organic extract was evaporated under reduced pressure in vacuum to deliver exclusively the corresponding 1,4-triazole, Scheme 1. 2.5 Synthesis of 1-Benzyl-4-Phenyl Triazole Phenyl acetylene (1 equiv. 0.1 mL) and (2 equiv. 0.20 mL), benzyl azide (1 equiv. 0.12 mL) and (2 equiv. 0.24 mL) and catalyst (0.025, 0.05, 0.1, 0.15 equiv.) were mixed in presence of acetonitrile and water mixture (1:1, 20 mL) and stirring the mixture at room temperature or with heating for until the reaction is completed. The mixture was filtered off. Dichloromethane was added to the filtrate and the organic layer was separated and the organic extract was evaporated under reduced pressure in vacuum to deliver exclusively the 1-benzyl-4-phenyl triazole, Scheme 2.

2.2 Synthesis of the SCP 1 and 2 The SCP {[SnMe3(bpe)][Ag(CN)2]·2H2O}, 1 and {[CuI(CN) (phen)2][CuII(CN)2(phen)]·5H2O}, 2 were synthesized according to the literature procedure [24, 25]. Anal. Calc. for 1 (C17H25N4O2AgSn): C, 37.53; H, 4.63; N, 10.30%. Found: C, 37.58; H, 4.47; N, 10.28% and anal. Calc. for 2 (C39H34N9O5Cu2): C, 56.0; H, 2.8; N, 15.0%. Found: C, 56.05; H, 2.7; N, 14.87%. The magnetic susceptibility of 2 is µeff. = 1.89 BM indicating the paramagnetic nature of 2.

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3 Results and Discussion 3.1 Structures of the SCP 1 and 2 The asymmetric unit of the SCP 1 contains one 1,2-bis(4pyridyl)ethane (bpe) molecule, one Me3Sn cation, one Ag atom, two cyanide ligands and two water molecules, Fig. S1. The structure of 1 consists of cationic {–(Me3)

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217

Sn–bpe–}+ chains that are neutralized by [Ag(CN)2]− anions [24]. The anionic ribbons connect the cationic layers by extensive hydrogen bonds; 2.715–2.958  Å, and π–π stacking and short contacts creating unique supramolecular 3D-network structure, Fig. 1 [24].

The structure of the SCP 2 contains [CuI(CN)(phen)2], [CuII(CN)2(phen)] fragments and five water molecules which are connected with each other by hydrogen bonds, Fig.  2. The water tapes play a complementary role via hydrogen bonds for stabilizing the network structure of the

Scheme 1 Click reactions for the formation of 1-benzyl4-bromomethyl triazole using the catalysts 1 and 2

Br

N3 HC

C

CH2

SCP 1

N

Acetonitrile/ water[1:1]

N

benzyl azide Propargyl bromide

HC

C

CH2

1-benzyl-4-(bromomethyl)-1H-1,2,3triazole

N

SCP 1

CH

1-benzyl-4-phenyl-1H-1,2,3-triazole

phenylacetylene

N3

N

N

Acetonitrile/ water[1:1]

SCP 2

N

CH Acetonitrile/ water[1:1] benzyl azide

Br

N

Acetonitrile/ water[1:1]

N3

benzyl azide

N

N

SCP 2

benzyl azide Propargyl bromide

Scheme 2 Click reactions for the formation of 1-benzyl4-phenyl triazole using the catalysts SCP 1 and 2

Br

1-benzyl-4-(bromomethyl)-1H-1,2,3triazole

Br

N3

N

phenylacetylene

N

N

1-benzyl-4-phenyl-1H-1,2,3-triazole

Fig. 1 View of the overall 3D-structure of 1 showing the alternating cationic and anionic layers

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SCP 2 in addition to the π–π stacking forming 3D-network [25], Fig. S2. 3.2 Spectral Characteristics of the SCP 1 and 2 The IR spectra of the SCP 1 and 2 exhibit strong broad band at 3425 and 3397  cm−1, respectively, corresponding to the stretching vibrations of the water molecules. Generally, the IR spectra exhibit the bands characteristic of the (MCN)n fragment and the ligands. The IR spectrum of the SCP 1 displays strong band at 2138  cm−1 corresponding to υCN. The presence of this band at lower wavenumber than those of the bridging cyanides and higher value than those of the terminal cyanides is a good evidence of the presence of the hydrogen bonds between the [Ag(CN)2]− anions and the water molecules. On the other hand, the presence of two υCN IR absorption bands in the spectrum of the SCP 2 at 2129 and 2086 cm−1 supports the presence of two different cyanide groups. The first type of the cyanide groups is bonded to CuI while the other is coordinated to CuII centers, supporting the presence of mixed valence copper cyanide coordination polymer. In addition, the υCu–C bands at 429 and 435  cm−1 confirm the presence of two (CuCN)n fragments while the band of υ(Ag−C) appears at about 468  cm−1. These bands confirm the presence of M-CN moiety. Methylene groups of the bpe ligand as well as the methyl groups of the Me3Sn fragment are characterized in the IR spectrum of 1 by C–H stretching vibrations at 2925 and 2871 cm−1 and by C–H deformation band at 1461  cm−1. The spectrum of 2 displays the bands of the phen ligand at 3059, 2926  cm−1 (υCH(arom)), 1617  cm−1 (υC=N), 1421  cm−1 (δCH) and at 770, 724 cm−1 (γCH).

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H NMR spectrum of the SCP 1 displays three distinct bands for the bipodal ligand, bpe, Fig. S3. The doublet at 8.42 and 8.43  ppm is assigned to H2,6 & H2\,6\ while the doublet at 7.24 and 7.25  ppm is assigned to H3,5&H3\,5\ where each doublet corresponds to four protons with J(1H,1H) coupling constant = 5.1. The ethylenic group gives rise to one singlet band at 2.93  ppm. The methyl protons attached to the tin atom exhibited a well-defined singlet at 0.53 ppm accompanied by two Sn(IV) satellites, 2J(1H–119Sn) coupling constant = 65.0  Hz, which falls in the range for five-coordinate trimethyltin(IV) species. The singlet band at 3.38  ppm is due to the protons of the water molecules. On the other hand, 13C-spectrum of 1 exhibits four bands for bpe; at 149.3  ppm for α carbon nuclei, at 123.4  ppm for β carbon nuclei, at 148.9 ppm for γ carbon nuclei and at 33.4  ppm for the ethylenic carbons, Fig. S4. The cyanide groups display singlet band in the 13C-spectrum; at 142.5  ppm. The Me3Sn units give rise to a triplet peak at 0.21  ppm, including characteristic satellite peaks with a 1 119 J ( Sn–13C) coupling constant of about 500.2 Hz which also supports a trigonal bipyramidal structure. Thus, the NMR spectra confirm the presence of the cyanide ligand, the bipodal ligands, water molecules as well as the Me3Sn units as bridging groups. The ratio between the peaks areas of all types in the 1H NMR spectrum of 1 support the composition elucidated by X-ray diffraction and elemental analysis. The X-ray powder diffractograms of 1 and 2 which are the products of the same ternary adducts, are very rich in sharp discrete lines, Figs.  3 and 4. Comparing the X-ray powder diffractograms of 1 and 2 with those of the simulated ones, Figs.  3 and 4, indicate that they are identical exhibiting the same 2θ values and the same lattice

Fig. 2 An ORTEP plot of the asymmetric unit of the SCP 2 with atom labeling scheme

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219

Fig. 3 The simulated (upper) and powder (lower) X-ray diffractions of the SCP 1

constants. Thus, the bulk materials of 1 and 2 are iso-structurally identical with their single crystals. 3.3 Click Reactions The advantageous properties of Huisgen cyclo-addition, together with the most useful modular nature of the click chemistry approach, make it well-suited for use in the synthesis of new molecules, especially conjugates composed of two quite different subunits. Examples are bioorganic– inorganic conjugates such as the organic azides and the boron clusters [11, 26]. A preliminary screening study using Propargyl bromide or phenyl acetylene with benzyl azide and catalysts 1 or 2, which differ in

the nature ligands, geometry and metals, was undertaken. For initial studies, reactions were performed in acetonitrile and water (1:1) at room temperature (25–28 °C). This ratio was found to be suitable solvent because of the high solubility of both alkyne and azides to give corresponding triazoles (1-benzyl-4-bromomethyl triazole and 1-benzyl-4-phenyl triazole) in 100% yield. The different factors affecting the yield of triazoles such as concentration of azide and alkyne, catalyst amount, time and temperature, have been investigated to apply the best conditions to obtain 98–100% yield triazoles. The results are shown in Tables  1, 2, 3, 4, 5 and 6. It is observed that the azide/alkyne ratio as well as the amount of catalyst (0.05–0.15  mol%) affect the time required to obtain the

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Fig. 4 The simulated (upper) and powder (lower) X-ray diffractions of the SCP 2

best yield of 1-benzyl- 4-bromomethyl triazole. Using 0.15 mol % of SCP 1 as a catalyst with the ratio 2:1 azide/ alkyne (propargyl bromide) affords the full conversion (yield 100%) of azide/alkyne to 1-benzyl- 4-bromomethyl triazole after 25  min at room temperature, Table  1, entry 3. On the other hand, full conversion [yield100%] of azide/alkyne (propargyl bromide) [1:2] to 1-benzyl4-bromomethyl triazole required the use of 0.15  mol % of the catalyst SCP 2 within 30 min at room temperature Table 2, entry 4. Above reactions represent the best conditions for the formation of 100% yield 1-benzyl- 4-bromomethyl triazole within shortest time. Also, in case of the alkyne phenyl acetylene, using 0.10 mol % of the SCP

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1 as a catalyst with the ratio 1:1 azide/ alkyne affords the full conversion (yield 100%) of azide/alkyn 1-benzyl-4-phenyl triazole after 30  min at room temperature, Table 3, entry 8. In the case of the SCP 2, full conversion [yield100%] of azide/alkyne [1:1] to 1-benzyl-4-phenyl triazole required the use of 0.15  mol % of the catalyst 2 within 35  min at room temperature Table  4, entry 7. Above reactions represent the best conditions for the formation of 100% yield 1-benzyl-4-phenyl triazole within shortest time. Varying the nature of the catalyst between the silver 1 and copper 2 metals had little impact on the yield. A key advantage of using 1 is that there was no evidence that the catalyst

J Inorg Organomet Polym (2017) 27:215–224 Table 1 Optimization with the SCP 1 catalyst in the Ag-AAC reaction

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Entry

Azide

Alkyne

Catalyst ratio/ equiv

Time/min

Temperature

Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12

2 2 2 1 1 1 1 1 1 2 2 2

1 1 1 2 2 2 1 1 1 1 1 1

0.05 0.1 0.15 0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.15 0.15

80 30 25 90 70 95 110 130 145 50 20 12

r.t r.t r.t r.t r.t r.t r.t r.t r.t r.t 40 °C 60 °C

98 98 100 97 100 98 100 100 100 100 98 100

Reaction conditions for entries 1–9 of propargyl bromide, benzyl azide. Entry 10 represents recovery reaction

Table 2 Optimization with the SCP 2 catalyst in the Cu-AAC reaction

Entry

Azide

Alkyne

Catalyst ratio/ equiv

Time/min

Temperature

Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12

2 2 2 1 1 1 1 1 1 1 1 1

1 1 1 2 2 2 1 1 1 2 2 2

0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.15 0.15

90 105 120 30 70 60 60 80 95 50 20 15

r.t r.t r.t r.t r.t r.t r.t r.t r.t r.t 40 °C 60 °C

100 100 95 100 98 98 95 100 100 100 100 100

Reaction conditions for entries 1–9 of propargyl bromide, benzyl azide. Entry 10 represents recovery reaction

and alkyne reacted vigorously, including when reactions are done at a larger scale. For instance, when a 10-fold increase in reaction scale was run using phenyl acetylene and SCP 1, the desired triazole was readily isolated in 100% yield after 30  min at room temperature. One additional advantage of using the homogeneous catalyst as opposed to AgNO3 is that at the completion of a reaction there was no evidence of silver metal deposition, owing to the robust nature of the metal complex [11–13]. The general utility of the catalyst under the most promising conditions was evaluated subsequently using SCP 1 and 2 and two of different alkynes in direct comparison to reactions performed in the presence of catalysts Cu(OAc)2 and AgNO3 as shown in Tables 5 and 6. In all cases isolated yields are reported. Under identical conditions for the AgNO3 or Cu(OAc)2 and sodium ascorabate-catalyzed reaction, it

was found that Propargyl bromide and phenyl acetylene were converted to the corresponding triazole in 100% yield in both cases after only 25–28 and 12 h, respectively, under the present conditions at room temperature, Tables  5 and 6. Also, Cycloadditions of copper(I) acetylides to azides and nitrile oxides provide ready access to 1,4-disubstituted 1,2,3-triazoles within 6–12  h at r.t. using CuSO4·5H2O in presence of sodium ascorbate [27] while decarboxylative coupling of alkynoic acids and 1,3-dipolar cycloaddition of azides avoids usage of gaseous or highly volatile terminal alkynes, reduces handling of potentially unstable and explosive azides to a minimum, and furnishes various functionalized 1,2,3-triazoles using CuSO4.5H2O as catalyst within 20–24 h at 65 °C in excellent yields and a very good purity [28, 29]. On the other hand, some AgI-catalyzed azide–alkyne cycloaddition

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Table 3 Optimization with the SCP 1 catalyst in the Ag-AAC reaction

Entry

Azide

Alkyne

Catalyst ratio/ equiv

Time/min

Temperature

Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12

2 2 2 1 1 1 1 1 1 1 1 1

1 1 1 2 2 2 1 1 1 1 1 1

0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.1 0.05 0.1 0.1 0.1

90 103 105 130 135 90 100 30 90 70 20 10

r.t r.t r.t r.t r.t r.t r.t r.t r.t r.t 40 °C 60 °C

100 95 98 98 100 97 98 100 97 100 100 100

Reaction conditions for entries 1–9 of phenyl acetylene, benzyl bromide. Entry 10 represents reaction recovery

Table 4 Optimization with the SCP 2 catalyst in the Cu-AAC reaction

Entry

Azide

Alkyne

Catalyst ratio/ equiv

Time/min

Temperature

Yield (%)

1 2 3 4 5 6 7 8 9 10 11 12

2 2 2 1 1 1 1 1 1 1 1 1

1 1 1 2 2 2 1 1 1 1 1 1

0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.1 0.05 0.15 0.15 0.15

50 80 50 60 90 75 35 50 65 55 10 7

r.t r.t r.t r.t r.t r.t r.t r.t r.t r.t 40 60

100 98 98 95 100 98 100 98 100 100 98 100

Reaction conditions for entries1–9 of phenyl acetylene, benzyl bromide. Entry 10 represents reaction recovery

Table 5 Comparison between SCP 1, AgNO3 and SCP 2, Cu(OAc)2 as catalysts for catalyzed—AAC reactions

Table 6 Comparison between SCP 1, AgNO3 and SCP 2, Cu(OAc)2 as catalysts for catalyzed - AAC reactions

Catalyst

Catalyst ratio

Alkyne

Azide

Yield (%)

Time

Catalyst

Catalyst ratio

Alkyne

Azide

Yield (%)

Time

SCP1 AgNO3 SCP 2 Cu(OAc)2

0.15 0.15 0.15 0.15

1 1 2 2

2 2 1 1

100 100 100 98

25 min 28 h 30 min 12 h

SCP1 AgNO3 SCP2 Cu(OAc)2

0.10 0.10 0.15 0.15

1 1 1 1

1 1 1 1

100 100 100 100

30 min 25 h 35 min 12 h

Reaction conditions for propargyl bromide, benzyl azide

Reaction conditions for phenyl acetylene, benzyl azide

reactions were reported leading to 1,2,3-triazoles within 16–26 h at room temperature, however no competent silver(I) species has been reported to promote the AAC reaction alone [13, 30, 31]. Thus, the SCP 1 and 2 exhibit higher catalytic

performance than the usual Cu(I) and Ag(I) salts where the triazoles are formed after few minutes rather than hours. The catalytic activity of the SCP 1 and 2 is affected by several factors as the unique structure of the SCP, the pores and cavities

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J Inorg Organomet Polym (2017) 27:215–224 Table 7 1H-NMR spectra of triazole derivatives

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Compound

δ(CH–Phenyl ring)

δ(CH–Triazole ring)

δ(CH2–Br)

δ(CH2–N)

1-Benzyl-4-(bromomethyl)-triazole 1-Benzyl-4-phenyl-triazole

7.06–7.43 7.26–7.46

7.32 7.83

4.5 –

4.82 4.44

as well as the Cu(I) and Ag(I) sites. The reactions progress were monitored by TLC and the products were purified by preparative TLC using CH2Cl2 as a mobile phase to generate the desired triazoles in quantitative high yields which were confirmed by 1H-NMR spectra, Table 7. The phenyl protons of 1-benzyl-4-bromomethyl triazole appear as multiple peaks at 7.06–7.43 ppm. The triazole proton gives rise a triplet at 7.32 ppm with 3J(1H,1H) coupling constant = 1.82. The protons of the CH2Br fragment absorb at 4.50  ppm which appears as singlet peak corresponding to two protons while the protons of the CH2N fragment exhibit a singlet corresponding to two protons at 4.82  ppm. On the other hand, a multiple peaks appear in the 1H-NMR spectrum of 1-benzyl-4-phenyl triazole at 7.26–7.46 ppm corresponding to ten protons of the two phenyl rings. A triplet at 7.83 ppm can be attributed to one proton of the triazole ring with 3J(1H,1H) coupling constant = 1.64. Also, a singlet was observed at 4.44 ppm attributed to two protons of the CH2N fragment. The SCP 2 was successful in producing 1,2,3-triazoles in 100% in 50 min without using sodium ascorbate. During the course of our studies, as previously reported by Sharpless [7], the use of the SCP 2 reduced by sodium ascorbate gave generally higher yield than a direct source of Cu owing to the high degree of efficiency, the reaction could be conducted with a stoichiometric amount (4.5 equiv.) of azides. Purification was greatly simplified by the absence of side products. The possibility of catalyst recycling was considered after the end of the experiment and collecting the triazole, and then starting a new experiment under identical conditions. It was found that the catalysts 1 and 2 maintained their catalytic activity for two cycles. However, after the second cycle, the catalytic activity decreases slightly due to the homogeneous nature of the catalysts, Tables 1, 2, 3 and 4, entry 10. When experiments are repeated at high temperatures (40–60 °C), the yields of the catalyzed reactions were 98–100% for all the compounds tested after 7–30  min, Tables 1, 2, 3 and 4. Thus, elevated temperature enhances the rate of catalyzed- AAC reactions. On the other hand, when the control reactions were run in the absence of the catalyst, yields of the products at room temperature were negligible (