Palladium-Free, Highly Efficient Mesoporous Tin Silicates Catalytic

May 15, 2014 - ... of Applied Sciences, RMIT University, Melbourne, Victoria 3001,. Australia. ABSTRACT: Three-dimensional mesoporous tin silicates (P...
0 downloads 0 Views 3MB Size
Download PDF
Article pubs.acs.org/IECR

Palladium-Free, Highly Efficient Mesoporous Tin Silicates Catalytic Acyl Sonogashira Coupling Reaction K. Raveendranath Reddy,† M. Suresh,† M. Lakshmi Kantam,† Suresh K. Bhargava,‡ and Pavuluri Srinivasu*,† †

Inorganic and Physical Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500007, Andhra Pradesh, India ‡ Advanced Materials and Industrial Chemistry Group, School of Applied Sciences, RMIT University, Melbourne, Victoria 3001, Australia ABSTRACT: Three-dimensional mesoporous tin silicates (PS-2) with different Si/Sn mole ratios are synthesized by direct hydrothermal treatment via a soft-templating technique under acidic conditions. The first example of PS-2 catalysts composed of tunable textural properties and designed to overcome the problems associated with stoichiometric acetylenic Grignard reagents and large amounts of uneconomical Pd catalysts indeed shows that a new synthetic approach toward direct acyl Sonogashira coupling reaction through C−C coupling has been developed under palladium metal- and ligand-free conditions. Both aromatic and aliphatic alkynes could react with acid halides to produce ynones and its derivatives under solvent-free conditions.

1. INTRODUCTION Mesoporous materials have received attention as an important class of materials because of their unique textural properties and tunable ordered pore structures that translate into potential applications in fuel cells, solar cells, and catalysis.1 Since the first synthesis of low bulk density mesoporous silica materials using cationic surfactant, they have been comprehensively studied and widely applied to many fields, such as drug delivery, adsorption, catalysis, electronics, and biosensors.2−4 In recent years, much progress has been achieved in tuning the properties of mesoporous materials by changing cationic, anionic, and neutral surfactants as structure-directing agents.5−7 Thus, various two or three-dimensional (2D or 3D) pore structure materials, such as MCM-41, MCM-48, SBA-1, SBA-15, HMS, MSU, and KIT-6 with unique textural properties such as high surface area, large pore volume, and tunable pore diameter have also been prepared.1,8−11 Interestingly, 3D porous structured materials show superior performance over 2D materials in diffusion of reactants, which avoids pore blocking. In addition, 3D porous structured materials also offer several advantages for potential applications in adsorption, separation, and catalytic transformation of bulky molecules. However, mesoporous silica materials have neutral framework and lack acidity, which could be circumvented by modification of silica for versatile applications. In particular, tin-loaded porous heterogeneous acid catalytic materials prepared under basic conditions, such as Sn-MFI, Sn-beta zeolite, and Sn-MCM-41 have been involved in important organic reactions, including Baeyer−Villiger (BV) oxidations, Meerwein−Ponndorf−Verley reductions, Mukaiyama-aldol condensations, and catalytic cellulose pyrolysis.12−15 However, incorporation of tin ions into the framework of mesoporous materials under acidic conditions is very difficult because of the cationic form of the metal rather than the corresponding oxo species. Therefore, it is a great challenge to develop a direct synthesis method for incorporation of tin in 3D mesoporous channels under acidic conditions. On the other © XXXX American Chemical Society

hand, mesoporous materials have been involved effectively in green catalytic process for the synthesis of fine chemicals and drug intermediates.1c In particular, conjugated alkynones (ynones) and their derivatives have been shown to be extremely flexible in applications as synthetic intermediates for production of saturated polycyclic compounds16 and many biologically active heterocyclic derivatives.17 The conventional approach for the synthesis of ynones involves the crosscoupling reaction between stoichiometric acetylenic Grignard reagents of thallium,18 zinc,19 lithium,20 indium,21 and stibium22 reagents with alkyl and aryl acid chloride. However, stoichiometric acetylenic Grignard reagents and large amounts of Pd catalysts23,24 made the reaction highly uneconomical. Thus, an alternative route for synthesis of ynones by direct coupling of terminal alkynes with acid halides under noblemetal-free conditions is very important. In this context, herein we describe a highly efficient coupling protocol between terminal alkynes and carboxylic acid halides for synthesis of corresponding ynones by a newly developed 3D mesoporous tin silicate catalysts consisting of tin species embedded in an ordered porous silica structure to provide ynones selectively in a most economical way under palladium-, ligand-, and solventfree conditions.

2. EXPERIMENTAL SECTION 2.1. Materials. F-127, Hydrochloric acid, tetraethyl orthosilicate [Si(OC2H5)4, TEOS], tin chloride (SnCl4· 5H2O), and other chemicals and solvents were purchased Special Issue: Ganapati D. Yadav Festschrift Received: April 5, 2014 Revised: May 14, 2014 Accepted: May 15, 2014

A

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

(s, 9H). 13C NMR (75 Hz, CDCl3): δ 178.1, 154.6, 136.9, 134.1, 133.0, 129.6, 128.6, 125.8, 117.1, 93.9, 86.8, 35.1, 31.0. Entry 3, 3-(4-Bromophenyl)-1-phenylprop-2-yn-1-one. White solid; mp =102−103 °C. Molecular formula C15H9BrO. 1H NMR (300 MHz, CDCl3): δ 8.22−8.17 (d, 2H), 7.66−7.60 (t, 1H), 7.59−7.48 (m, 6H). 13C NMR (75 Hz, CDCl3): δ 177.7, 136.6, 134.3, 132.0, 129.5, 128.6, 128.3, 125.5, 118.9, 91.6, 87.6. Entry 4, 1-Phenyl-3-p-tolylprop-2-yn-1-one. White solid; mp =66−67 °C. Molecular formula C16H12O. 1H NMR (300 MHz, CDCl3): δ 8.25−8.20 (d, J = 7.17 Hz, 2H), 7.64−7.56 (m, 3H), 7.53−7.48 (t, J = 7.73 Hz, 2H)7.24 (d, J = 7.76 Hz, 2H), 2.37 (s, 3H). 13C NMR (75 Hz, CDCl3): δ 177.7, 145.2, 134.5, 132.9, 130.6, 129.6, 129.3, 128.6, 120.2, 92.6, 86.9, 21.8. Entry 5, 1-Phenylnon-2-yn-1-one. Pale yellow liquid. Molecular formula C15H18O. 1H NMR (300 MHz, CDCl3): δ 8.17−8.12 (d, 2H), 7.62−7.57 (t, 1H), 7.50−7.45 (t, 2H), 2.51−2.47 (t, J = 7.17 Hz, 2H), 1.71−1.63 (m, 2H), 1.52−1.40 (m, 2H)1.39−1.29 (m, 4H), 0.93−0.89 (t, 3H). 13C NMR (75 Hz, CDCl3): δ 178.2, 136.9, 133.8, 129.5, 128.5, 96.9, 79.7, 31.2, 28.6, 27.8, 22.5, 19.2, 14.0. Entry 6, 3-Phenyl-1-(p-tolyl)prop-2-yn-1-one. White solid; mp = 86−87 °C. Molecular formula C16H12O.1H NMR (300 MHz, CDCl3): δ 8.14−8.10 (d, 2H), 7.71−7.67 (d, 2H), 7.51− 7.46 (t, 1H), 7.45−7.40 (t, 2H), 7.34−7.30 (d, 2H), 2.46 (s, 3H). 13C NMR (75 Hz, CDCl3): δ 177.9, 141.5, 136.9, 133.9, 130.0, 129.5, 129.4, 128.5, 116.9, 93.8, 86.7, 21.7. Entry 7, 1,3-Di-p-tolylprop-2-yn-1-one. White solid; mp =90−91 °C. Molecular formula C17H14O. 1H NMR (300 MHz, CDCl3): δ 8.11 (d, J = 8.2 Hz, 2H), 7.30 (d, J = 7.9 Hz, 2H), 7.22 (d, J = 7.78 Hz, 2H), 2.44 (s, 3H), 2.40 (s, 3H). 13C NMR (75 Hz, CDCl3): δ 176.7, 144.1, 140.1, 133.7, 132.0, 128.6, 128.4, 128.3, 116.1, 92.2, 85.8, 20.8, 20.7. Entry 8, 1-p-Tolylnon-2-yn-1-one. Pale yellow liquid. Molecular formula C16H20O. 1H NMR (300 MHz, CDCl3): δ 8.03 (d, J = 8.4 Hz, 2H), 7.27 (d, J = 8.7 Hz, 2H), 2.48 (t, J = 7.2 Hz, 2H), 2.42 (s, 3H), 1.70−1.27 (m, 8H), 0.90 (t, J = 7.0 Hz, 3H). 13C NMR (75 Hz, CDCl3): δ 177.9, 144.8, 134.6, 129.6, 129.1, 96.3, 79.6, 31.1, 28.6, 27.7, 22.4, 21.7, 19.1, 13.9. Entry 9, 1-Cyclohexyl-3-phenylprop-2-yn-1-one. Pale yellow liquid. Molecular formula C15H16O. 1H NMR (300 MHz, CDCl3): δ 7.60−7.55 (d, 2H), 7.47−7.42 (t, 3H), 7.41− 7.35 (t, 3H), 2.55−2.47 (m, 1H), 2.10−1.18 (m/w, 10H). 13C NMR (75 Hz, CDCl3): δ 191.3, 132.9, 130.5, 128.5, 120.2, 91.3, 87.2, 52.3, 28.3, 25.8, 25.4. Entry 10, 3-(4-(tert-Butyl) phenyl)-1-cyclohexylprop-2-yn1-one. Pale yellow liquid. Molecular formula C19H24O. 1H NMR (300 MHz, CDCl3): δ 7.54−7.50 (d, J = 8.54 Hz, 2H), 7.42−7.38 (d, J = 8.54 Hz, 2H), 2.54−2.46 (m, 1H), 2.10−1.18 (m/w, 10H), 1.32 (s, 9H). 13C NMR (75 Hz, CDCl3): δ 191.6, 154.3, 132.9, 125.7, 117.1, 92.1, 87.0, 52.3, 35.1, 31.0, 28.4, 25.8, 25.4. Entry 11, 1-Cyclohexyl-3-(p-tolyl)prop-2-yn-1-one. Pale yellow liquid. Molecular formula C16H18O. 1H NMR (300 MHz, CDCl3): δ 7.51−7.43 (d, 2H), 7.21−7.15 (d, 2H), 2.54− 2.45 (m, 1H), 2.39 (s,1H), 2.10−1.17 (m/w, 10H). 13C NMR (75 Hz, CDCl3): δ 191.5, 141.2, 132.9, 129.3, 116.9, 92.0, 87.0, 52.2, 28.3, 25.7, 25.4, 21.6. Entry 12, 1-Cyclohexylnon-2-yn-1-one. Pale yellow liquid. Molecular formula C15H24O. 1H NMR (300 MHz, CDCl3): δ 2.37 (m, 3H), 2.0−1.54 (m, 7H), 1.47−1.19 (m, 11H), 1.90 (m, 3H). 13C NMR (75 Hz, CDCl3): δ 191.8, 95.1, 80.1, 52.3, 31.2, 28.5, 28.3, 27.7, 25.8, 25.4, 22.5, 19.0, 14.0.

from Sigma-Aldrich and were analytical grade. All the products were purified by using ACME silica gel (100−200 Mesh). 2.2. Synthesis Procedure for Tin Silicates. The mesoporous tin silicates were synthesized by using F127 as polymer and TEOS and SnCl4·5H2O used as Si and Sn sources, respectively. In a typical synthesis, 2.9 g of F127 is completely dissolved in 140 g of HCl solution. The solution was stirred for 5 h, and then 14 g of TEOS and different amounts of tin chloride are added to get Si/Sn mole ratios of 24, 51, 75, and 97. The mixture was stirred for 24 h followed by aging at 100 °C for 24 h. Then, the solution was filtered and dried at 80 °C. Finally, mesoporous tin silicates were obtained after complete removal of the template by calcination at 550 °C for 5 h in the presence of air. The obtained products are denoted as PS-2(X), where X represents Si/Sn mole ratio. 2.3. Typical Procedure for Synthesis of Ynones. PS-2 catalyst (20 mg) and 1 mmol of terminal alkyne were placed in a 20 mL round-bottom flask. To this mixture, 7.0 mmol of dry triethyl amine (TEA) followed by 10 mg of CuI was added. After 5 min stirring, to the above mixture 1.5 mmol of acid halide was added drop-by-drop to avoid the formation of byproducts such as homo coupling under vigorous stirring. The total mixture was further stirred to complete the reaction (monitored by thin-layer chromatography). The reaction mixture was diluted with ethyl acetate, and the catalyst was recollected after complete conversion of terminal alkyne. The reaction mixture was washed with sodium bicarbonate solution and dried over anhydrous sodium sulfate. The obtained product after evaporation of solvent under reduced pressure was purified by column chromatography and confirmed by characterization techniques. 2.4. Characterizations. X-ray powder diffraction (XRD) patterns of all catalysts were recorded on a Rigaku Ultima-IV (Rigaku Corporation, Japan) using Ni-filtered Cu Kα radiation (λ = 1.5406 Å) with a scan speed of 1° min−1 and a scan range of 0.7°−80° at 40 kV and 30 mA. Both low-angle and wideangle XRD patterns of the catalyst samples were recorded to characterize the crystallinity and mesoporous ordering of the samples. The N2 adsorption−desorption isotherms were performed at 77 K using QuadraSorb SI (Quantachrome Instruments Corporation, U.S.) System after degasification under vacuum at 423 K for 12h. The specific surface areas were evaluated using the Brunauer−Emmett−Teller (BET) method in the p/p0 range of 0.05−0.35. Pore size was calculated by using the Barrett−Joyner−Halenda (BJH) method from the desorption branch of the isotherm. The total pore volume was taken by a single-point method at p/p0 = 0.99. The ultraviolet− visible (UV−vis) diffused reflectance spectra of calcined samples were recorded on a Shimadzu UV−Vis spectrophotometer (UV-3600) in the UV−vis range of 200−800 nm. Spectral grade BaSO4 was taken as reference for the reflectance spectra. The ynones were characterized by 1H NMR and 13C NMR spectrometer (TMS as an internal standard and CDCl3 as solvent). 2.5. Analytical Data. Entry 1, 1,3-Diphenylprop-2-yn-1one. White solid; mp = 43 °C. Molecular formula C15H10O. 1H NMR (300 MHz, CDCl3): δ 8.30−8.17 (d, 2H), 7.75−7.58 (m, 3H), 7.56−7.34 (m, 5H). 13C NMR (75 Hz, CDCl3): δ 177.9, 136.8, 134.1, 133.0, 130.7, 129.5, 128.6, 128.5, 120.0, 93.1, 86.8. Entry 2, 3-(4-(tert-Butyl)phenyl)-1-phenylprop-2-yn-1-one. Pale yellow liquid; molecular formula C19H18O. 1H NMR (300 MHz, CDCl3): δ 8.28−8.19 (d, 2H), 7.69−7.41 (m, 7H), 1.33 B

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

3. RESULTS AND DISCUSSION 3.1. Characterization of PS-2 Catalysts. The structural order of PS-2 material after Sn incorporation is investigated

Figure 3. UV−vis DRS spectra of calcined PS-2 materials: (a) PS2(24), (b) PS-2(51), (c) PS-2(75), (d) PS-2 (97).

Figure 1. HRTEM image of PS-2(51).

Figure 2. Low-angle XRD spectra of calcined PS-2 materials: (a) PS2(24), (b) PS-2(51), (c) PS-2(75), and (d) PS-2(97).

using high-resolution transmission electron microscopy (HRTEM). The HRTEM image of calcined PS-2(51) is shown in Figure 1. The PS-2(51) exhibits a linear array of pores and pore channels, which is a clear indication of well-ordered pore structure. In addition, it also reveals that a PS-2(51) material possesses excellent 3D mesoscopic order. Figure 2 presents the powder XRD patterns of calcined PS-2 materials. All the materials show well-resolved diffraction peaks of (111), (200), and (220) reflections of face-centered cubic Fm3m symmetry, similar to that of pure siliceous material. Interestingly, with increasing tin content, the XRD peak intensity of PS-2 materials is significantly increased, which suggests that structural order of the PS-2 materials improved with increasing tin content. In addition, the diffraction peak shifts to a lower 2θ value, suggesting that the unit cell parameter (a0) significantly increases from 17.8 to 20.1 nm as the Si/Sn mole ratio decreases from 97 to 51. The results clearly confirm pore diameter of PS-2 materials systematically

Figure 4. (A) Adsorption−desorption isotherms of (a) PS-2(24), (b) PS-2(51), (c) PS-2(75), and (d) PS-2(97). (B) Pore size distribution of PS-2 materials. C

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

Table 1. Physiochemical Properties of Calcined PS-2 Catalysts

a

catalyst

a0a (nm)

surface area (m2 g−1)

pore diameter (nm)

pore volume (cm3 g−1)

PS-2(24) PS-2(51) PS-2(75) PS-2(97) NPS

18.6 20.1 19.1 17.8 16.3

732 791 698 607 582

3.7 4.3 3.7 3.7 3.4

0.64 0.86 0.65 0.37 0.34

Unit cell parameter.

Table 3. Effect of Benzoylchloride-to-Phenyl Acetylene Molar Ratioa entry

mole ratiob

yield (%)

1 2 3 4

0.5 1.0 1.5 2.0

41 68 93 93

a

Reactions were carried out using PS-2(51) (20 mg), phenyl acetylene (1 mmol), CuI (10 mg), and TEA (1 mL) at room temperature under solvent-free conditions. bBenoyl chloride/phenylacetylene molar ratio.

range of 200−800 nm as shown in Figure 3. The UV−visible diffuse reflectance spectroscopy (DRS) spectra of PS-2 materials show a single strong absorption peak at 209 nm when the Si/Sn mole ratio increases from 51 to 97. This is mainly due to the charge transitions (CT) from O2− to Sn4+ in tetrahedral coordination of Sn4+ in tin silicates. Further incorporation of tin species (PS-2(24) sample) in the silica framework cause an additional broad peak at 281 nm. The shoulder peak indicates the presence of hexa-coordinated polymeric Sn−O−Sn species at high tin content. The intense absorption peaks are usually taken as clear evidence for high incorporation of the tin species in a porous silica matrix. As shown in Figure 3, the intensity of the absorption band at 209 nm increased with incorporation of tin species in the silica frame. UV−vis DRS results clearly reflected that the isomorphic substitution of tin species with Si/Sn mole ratios from 97 to 51 is achieved in the mesoporous silica framework. However, for PS-2(24) material with high amount of tin incorporation, the formation of hexa-coordinated polymeric Sn−O−Sn species is observed. To obtain complete information about the texture of PS-2 materials, the nitrogen adsorption−desorption isotherms are measured. The textural parameters such as surface area are obtained from the Brunauer−Emmett−Teller method. The nitrogen adsorption−desorption isotherm and corresponding BJH pore size distribution are shown in Figure 4A,B. All the PS-2 materials possess classical type IV isotherms with H2 type hysteresis and steep capillary condensation steps occurring at relative pressures P/P0 of 0.4−0.6, which is characteristic of mesoporous materials. The textural properties of PS-2 materials are depicted in Table 1. The systematic increase in surface area and pore volume from 607 m2 g−1 and 0.37 cm3 g−1 for PS2(97) to 791 m2 g−1 and 0.86 cm3 g−1 for PS-2(51), respectively, is observed with decrease in the Si/Sn mole ratio, which are higher than that of pure mesoporous silica NPS material. It is interesting to note that the capillary condensation step shifts to higher relative pressure, revealing the increase in pore size of PS-2 materials from 3.7 to 4.3 nm with increasing tin content in the porous structure, which is due to the length of the Sn−O bond being greater than that of the Si−O bond because the ionic radius of tin is larger than that of silicon.

Figure 5. Effect of Si/Sn mole ratio of PS-2 catalysts on the yield of ynones.

Table 2. Effect of Base on the Synthesis of Ynonesa entry

base

yield (%)b

1 2 3 4 5 6 7

none La(OOCCH3)3 K2CO3 Bu3N i-Pr2NEt Et3N Et3N

nr nr nr 8 39 93 nrc

a

Reaction conditions: Tin silicate (20 mg), benzoyl chloride (1.5 mmol), phenyl acetylene (1 mmol), CuI (10 mg), room temperature, solvent free. bIsolated yields. cThe reaction was carried out in the absence of catalyst.

Figure 6. Effect of catalyst amount on the yield of ynones.

increases from 3.7 to 4.3 nm with increasing tin content. The elemental composition of calcined PS-2 materials is examined by inductive coupled plasma (ICP). The coordination arrangement of tin species in PS-2 materials is investigated by using UV−visible diffuse reflectance spectroscopy in the wavelength D

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

Table 4. Mesoporous Tin Silicates Catalyzed Acyl Sonogashira Coupling Reaction for Synthesis of Ynonesa

a

Reaction conditions: tin silicate (20 mg), benzoyl chloride (1.5 mmol), phenyl acetylene (1 mmol), CuI (10 mg), TEA (1 mL) as base and solvent, room temperature, solvent free.

3.2. Catalytic Studies. To effectively tackle the problems associated with noble-metal-based catalytic systems and their

These results are in good agreement with unit cell parameter values obtained from XRD analysis. E

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

and i-Pr2NET were used in the reaction, moderate yields of ynones were obtained (Table 2, entries 4 and 5). Finally, the use of TEA as base resulted in excellent yields (93%) of ynones at room temperature under solvent-free conditions using CuI as a cocatalyst (Table 2, entry 6). Furthermore, the reaction does not proceed in absence of catalyst, which signifies the important role of the catalyst. As shown in Figure 6, the effect of the catalyst amount was also investigated using the PS-2(51) catalyst. The yield of the reaction increased with catalyst amount, and maximum yield (93%) was observed when 20 mg of catalyst was used. The constant value of yield (93%) is maintained upon further increase in the catalyst amount to 25 mg. The influence of benzoyl chloride-to-phenyl acetylene molar ratio over the yield of ynones is shown in Table 3. The yield of ynones increased up to 93% when the molar ratio changed from 0.5 to 1.5. The yield remained constant even when the molar ratio was further increased to 2.0. The above results provided the incentive to synthesize ynone derivatives under palladium- and ligand-free conditions. The generality and scope of the reaction was investigated using a variety of aryl/ alkyl terminal alkynes and aryl/alkyl acid halides, and the results are summarized in Table 4. As shown in Table 4, the catalytic system is very versatile in nature, obtaining excellent yields, and is applicable to different electron-releasing and -withdrawing terminal alkynes with aryl acid halides (Table 4, entries 1−4). It is quite interesting to note that the coupling of terminal aryl alkynes with electron-releasing substituted aryl acid halides gave a similar yield of the corresponding ynones (Table 4, entries 6 and 7). Furthermore, the catalytic performance was studied for the coupling of aliphatic acid halides with a terminal aromatic alkynes under similar optimized reaction conditions, which achieved 84−92% yield of ynones (Table 4, entries 9−11). It is noteworthy that aliphatic terminal alkynes allowed to couple with both aromatic and aliphatic acid halides also gave good yields (Table 4, entries 5, 8, 12). 3.3. Mechanism of Interaction of PS-2 with Acid Halides and Terminal Alkynes. We propose a plausible mechanism for the coupling reaction of acid halides and terminal alkynes over PS-2 catalysts (Scheme 1). The PS-2 catalysts weaken the C−Cl bond in acid halides, which facilitates the formation of the acyl carbonium ion. Meanwhile, the alkyne carbanion is formed from the terminal alkyne, TEA, and CuI. This alkyne carbanion directly coupled with acyl carbonium ion to form ynones. In this study, the role of the catalyst is creating the electrophilic center for easy attack of terminal alkyne carbanion, resulting in excellent yields of ynones. Finally, to determine the stability of the catalyst after reaction, recyclability experiments were conducted. The catalyst was activated after reaction and used for four more cycles, and the results are summarized in Figure 7. The catalyst is highly active; no significant loss in yield of corresponding ynones is observed, which reveals that the catalyst is robust and could be used for various coupling reactions, which is an interesting alternative to current specialty and fine chemical industrial processes.

Scheme 1. Plausible Mechanism Involved in the Acyl Sonogashira Coupling Reaction over PS-2 Catalysts

Figure 7. Recyclability of the catalyst.

environmental and economical issues, mesoporous tin silicate catalyzed acyl Sonogashira coupling reaction has been performed using phenyl acetylene as terminal alkyne and benzoyl chloride as acylating agent. To determine the best reaction conditions (i.e., Si/Sn mole ratio) for obtaining excellent yields of corresponding ynones, the reaction has been attempted in the presence of different PS-2 catalysts with Si/Sn mole ratios of 24, 51, 75, and 97 (Figure 5). The yield of ynones increased from 72 to 93% with increasing the tin content in porous silica framework. Among the materials tested, PS-2(51) showed high yield of ynones because of high specific surface area, large pore size, and ordered three-dimensional pore structure. As PS-2(51) has shown high yield of ynones under optimized reaction conditions, it has been chosen as the standard catalyst for further studies such as effect of base, amount of catalyst, and phenyl acetylene and benzoyl chloride mole ratio. The effect of bases such as La(OOCCH3)3, K2CO3, Bu3N, i-Pr2NEt, and Et3N on obtaining high yield of ynones over PS-2(51) catalyst is investigated and the results are shown in Table 2. Interestingly, no conversion was observed in the absence of base under both solvent and neat conditions (Table 2, entry 1). When the reaction was carried out in the presence of inorganic bases such as La(OOCCH3)3 and K2CO3, no ynones product was formed (Table 2, entries 2 and 3). However, in the case of La (OOCCH3)3, acetyl benzoyl anhydride is obtained as final product with 100% conversion of benzoyl chloride. In addition, when other bases such as Bu3N

4. CONCLUSIONS We conclude that we have explored a novel and highly efficient economical coupling protocol between terminal alkynes and carboxylic acid halides for synthesis of corresponding ynones under palladium-, ligand-, and solvent-free conditions by using highly ordered 3D mesoporous tin silicates (PS-2) as catalyst. The yields obtained in this protocol are good to excellent and F

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

(12) Corma, A.; Nemeth, L. T.; Renz, M.; Valencia, S. Sn-zeolite beta as a heterogeneous chemoselective catalyst for Baeyer−Villiger oxidation. Nature (London, U.K.) 2001, 412−423. (13) Corma, A.; Domine, M. E.; Valencia, S. Water-resistant solid Lewis acid catalysts: Meerwein−Ponndorf−Verley and Oppenauer reactions catalyzed by tin-beta zeolite. J. Catal. 2003, 215, 294−304. (14) Dapsens, P. Y.; Mondelli, C.; Kusema, B. T.; Verel, R.; PerezRamirez, J. A continuous process for glyoxal valorisation using tailored Lewis-acid zeolite catalysts. Green Chem. 2014, 16, 1176−1186. (15) Torri, C.; Lesci, I. G.; Fabbri, D. Analytical study on the pyrolytic behaviour of cellulose in the presence of MCM-41 mesoporous materials. J. Anal. Appl. Pyrolysis 2009, 85, 192−196. (16) (a) Krafft, M. E.; Bonaga, L. V. R.; Felts, A. S.; Hirosawa, C.; Kerrigan, S. A Sterically-Encumbered, C2-Symmetric Chiral Acetal for Enhanced Asymmetric Induction in the Pauson−Khand Reaction. J. Org. Chem. 2003, 68, 6039−6042. (b) Wang, J. C.; Ng, S. S.; Krische, M. J. Catalytic diastereoselective synthesis of diquinanes from acyclic precursors. J. Am. Chem. Soc. 2003, 125, 3682−3683. (17) (a) Aulakh, V. S.; Ciufolini, M. A. Total Synthesis and Complete Structural Assignment of Thiocillin. J. Am. Chem. Soc. 2011, 133, 5900−5904. (b) Kim, N. J.; Moon, H.; Park, T.; Yun, H.; Jung, J. W.; Chang, D. J.; Kim, D. D.; Suh, Y. G. Concise and Enantioselective Total Synthesis of 15-Deoxy-Δ12,14-Prostaglandin J2. J. Org. Chem. 2010, 75, 7458−7460. (c) Waldo, J. P.; Larock, R. C. Synthesis of Isoxazoles via Electrophilic Cyclization. Org. Lett. 2005, 7, 5203−5205. (d) Karpov, A. S.; Oeser, T.; Muller, T. J. J. A novel one-pot fourcomponent access to tetrahydro-β-carbolines by a coupling aminationaza-annulation-Pictet−Spengler sequence (CAAPS). Chem. Commun. (Cambridge, U.K.) 2004, 1502−1503. (e) Xing, Y.; O’Doherty, G. A. De Novo Asymmetric Synthesis of Cladospolide B−D: Structural Reassignment of Cladospolide D via the Synthesis of its Enantiomer. Org. Lett. 2009, 11, 1107−1110. (f) Rooke, D. A.; Ferreira, E. M. Stereoselective Syntheses of Trisubstituted Olefins via Platinum Catalysis: α-Silylenones with Geometrical Complementarity. J. Am. Chem. Soc. 2010, 132, 11926−11928. (18) Marko, I. E.; Southern, J. M. Triorganothallium reagents in organic chemistry. 1. A simple, efficient and versatile preparation of ketones from acid chlorides. J. Org. Chem. 1990, 55, 3368−3370. (19) Lee, K. Y.; Lee, M. J.; Kim, J. N. Facile synthesis of α, βacetylenic ketones and 2,5-disubstituted furans: Consecutive activation of triple and double bond with ZnBr2 toward the synthesis of furan ring. Tetrahedron 2005, 61, 8705−8710. (20) Brown, H. C.; Racherla, U. S.; Singh, S. M. Improved highly efficient synthesis of α,β-Acetylenic ketones. Nature of the intermediate from the reaction of Lithium acetylide with boron trifluoride etherate. Tetrahedron Lett. 1984, 25, 2411−2414. (21) Perez, I.; Sestelo, J. P.; Sarandeses, L. A. Atom-Efficient MetalCatalyzed Cross-Coupling Reaction of Indium Organometallics with Organic Electrophiles. J. Am. Chem. Soc. 2011, 123, 4155−4160. (22) Kakusawa, N.; Yamaguchi, K.; Kurita, J.; Tsuchiya, T. Palladiumcatalyzed cross-coupling reactions between 1-alkynylstibines and acyl chlorides. Tetrahedron Lett. 2000, 41, 4143−4146. (23) Cox, R. J.; Ritson, D. J.; Dane, T. A.; Berge, J.; Charmant, J. P. H.; Kantacha, A. Room temperature palladium catalysed coupling of acyl chlorides with terminal alkynes. Chem. Commun. (Cambridge, U.K.) 2005, 1037−1039. (24) Alonso, D. A.; Najera, C.; Pacheco, M. C. Synthesis of Ynones by Palladium-Catalyzed Acylation of Terminal Alkynes with Acid Chlorides. J. Org. Chem. 2004, 69, 1615−1619.

similar to those of palladium-catalyzed homogeneous reactions. This coupling reaction can be performed under normal reaction conditions with no need of specialized equipment. Furthermore, the catalyst can be recycled with similar activity at room temperature and short reaction time compared to that of other palladium-free catalysts.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS K.R. thanks UGC-New Delhi, India for the award of the research fellowship. REFERENCES

(1) (a) Srinivasu, P.; Islam, A.; Singh, S. P.; Han, L.; Kantam, M. L.; Bhargava, S. K. Highly efficient nanoporous graphitic carbon with tunable textural properties for dye-sensitized solar cells. J. Mater. Chem. 2012, 22, 20866−20869. (b) Srinivasu, P.; Singh, S. P.; Islam, A.; Han, L. Metal-free counter electrode for efficient dye-sensitized solar cells through high surface area and large-porous carbon. Int. J. Photoenergy 2011, 2011, No. 617439. (c) Srinivas, M.; Srinivasu, P.; Bhargava, S. K.; Lakshmi Kantam, M. High-performance hexagonal nanoporous copper silicates catalyzed synthesis of propargylamines. Catal. Today. 2013, 208, 66−71. (2) Chiola, V.; Ritsko, J. E.; Vanderpool, C. D. Process for producing low-bulk density silica. U.S. Patent 3556725, 1971. (3) Radu, D. R.; Lai, C. Y.; Wiench, J. W.; Pruski, M.; Lin, V. S. Y. Gatekeeping Layer Effect: A Poly(lactic acid)-coated Mesoporous Silica Nanosphere-Based Fluorescence Sensor for Detection of AminoContaining Neurotransmitters. J. Am. Chem. Soc. 2004, 126, 1640− 1641. (4) Huh, S.; Chen, H. T.; Wiench, J. W.; Pruski, M.; Lin, V. S. Y. Cooperative Catalysis by General Acid and Base Bifunctionalized Mesoporous Silica Nanospheres. Angew. Chem., Int. Ed. 2005, 44, 1826−1830. (5) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Ordered mesoporous molecular sieves synthesized by a liquidcrystal template mechanism. Nature (London, U.K.) 1992, 359, 710− 712. (6) Che, S.; Bennet, A. E. G.; Yokoi, Y.; Sakamoto, K.; Kunieda, H.; Terasaki, O.; Tatsumi, T. A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure. Nat. Mater. 2003, 2, 801−805. (7) Zhao, D.; Huo, Q.; Feng, J.; Chmelka, B. F.; Stucky, G. D. Nonionic Triblock and Star Diblock Copolymer and OligomericSurfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures. J. Am. Chem. Soc. 1998, 120, 6024− 6036. (8) Zhang, Q.; Ariga, K.; Okabe, A.; Aida, T. A Condensable Amphiphile with a Cleavable Tail as a “Lizard” Template for the SolGel Synthesis of Functionalized Mesoporous Silica. J. Am. Chem. Soc. 2004, 126, 988−989. (9) Huo, Q.; Leon, R.; Petroff, P. M.; Stucky, G. D. Mesostructure Design with Gemini Surfactants: Supercage Formation in a ThreeDimensional Hexagonal Array. Science 1995, 268, 1324−1327. (10) Kleitz, F.; Choi, S. H.; Ryoo, R. Cubic Ia3d large mesoporous silica: synthesis and replication to platinum nanowires, carbon nanorods and carbon nanotubes. Chem. Commun. (Cambridge, U.K.) 2003, 2136−2137. (11) Kim, T. W.; Kleitz, F.; Paul, B.; Ryoo, R. MCM-48-like large mesoporous silicas with tailored pore structure: Facile synthesis domain in a ternary triblock copolymer-butanol-water system. J. Am. Chem. Soc. 2005, 127, 7601−7610. G

dx.doi.org/10.1021/ie501305x | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX