Heck Coupling in Ionic Liquids

Synthetic and medicinal chemistry intersect at the production of compounds. However there are stark contracts in approach with synthetic chemistry typically producing complex molecules and developing synthetic approaches. In medicinal chemistry, the focus is on compound access to facilitate compound screening and structure activity data acquisition to enable the synthesis of more active compounds. Medicinal chemistry relies on a small range of highly robust and reliable reactions to gain access to a wide array of potentially bioofi‐ cal reactions.[1, 2]


Introduction
Synthetic and medicinal chemistry intersect at the production of compounds.However there are stark contracts in approach with synthetic chemistry typically producing complex molecules and developing synthetic approaches.In medicinal chemistry, the focus is on compound access to facilitate compound screening and structure activity data acquisition to enable the synthesis of more active compounds.Medicinal chemistry relies on a small range of highly robust and reliable reactions to gain access to a wide array of potentially bioofical reactions.[1,2] This reliance on rebust chemistries has been significantly enhanced through the development of efficient C-C coupling protocols, in particular the coupling of aryl halides with α,βunsaturated building block.The power of these new coupling technologies has been reflected in the recent Nobel prizes in this area to Heck, [3] Suzuki, [4] Grubb and their co-workers.[5] While the development of new methodologies is of paramount importance across all areas of synthetic chemistry, simple developments and increased understanding of reaction conditions and reaction media often enhance these new methodologies.In this latter regard the growth of knowledge in and around room temperature ionic liquids and and their ability to moderate reaction outcomes through their tuneable nature and ability to act as solvents for a wide range of chemical compounds has proved, arguably, equally important.Importantly, the combination of developments in C-C coupling technology and RTILs has allowed enhancement in the overall process efficiency.That is, these processes are becoming more environmentally sustainable.
Our group's primary focus requires rapid access to focused compound libraries of bioactive molecules spanning multiple potential therapeutic targets: the inhibition of dynamin GTPase, protein phosphatases 1A and 2A and the development of anti-cancer lead compounds.[6][7][8][9][10][11][12] Where possible we are keen to apply green chemistry principles around reagent, solvent and synthetic pathway choice.[13][14][15][16] Within our own research efforts we have routinely tolerated low yields and difficult purifications to gain access to the desired compounds.[17,18] We have thus invested considerable resources in the examination, and application, of RTILs and other emerging technologies to the synthesis of bioactive focused compound libraries.[19][20][21][22][23] A current program focus within our team is the development of robust flow and microwave approaches to Pd-mediated C-C coulpling reactions, especially the Heck-Mizoroki (Heck reaction).

The Heck-Mizoroki reaction (the Heck reaction)
The cross-coupling of organic halides with alkenes in the presence of catalytic quantities of Pd(0) and a base was first reported by Mizoroki and Heck in 1971.[24,25] Over the next four decades this has become known as "the Heck reaction" and has been the subject of a number of synthetic and mechanistic studies.It is now generally accepted that there are four key requirements / conditions to a successful Heck coupling reaction: 1) Solvent: The Heck reaction generally requires a polar solvent such as dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO); 2) Base: The Heck reaction bases are usually selected from Et 3 N, NaOAc or aqueous Na 2 CO 3 or NaHCO 3 ; [26] 3) Catalyst: The Heck reaction uses 1-5 mol% catalytic palladium (0) or palladium (II) complexes.Most commonly in the form of Pd(0)-phosphine complexes such as tetrakis(triphenylphosphine)palladium(0) [Pd(PPh 3 ) 4 ] or dibenzylidene-acetone complexes of Pd(0) such as Pd 2 (dba) 3 (dba).[27] Simple palladium salts such as PdCl 2 or Pd(OAc) 2 in the absence of stabilizing phosphine ligands have also been widely used.[28] - [30] 4) Halide: The reactivity of the halide precursor effects the time and temperature required to effect the desired coupling reaction (Figure 1).also been widely used. [28]- [30 4) Halide: The reactivity of the halide precursor effect the desired coupling reaction (Figure 1).

Heck reaction in Room Temperature Ionic Liquids (RTILs
The emergence of room temperature ionic liquids (RTILs) has allowed the range of novel and tuneable solvents systems.

Heck reaction in Room Temperature Ionic Liquids (RTILs)
The emergence of room temperature ionic liquids (RTILs) has allowed the investigation of the Heck reaction in a wide range of novel and tuneable solvents systems.
These novel solvents cover a wide range of structural moiefs from the now well established methylimidazolium and pyridinium salts through ammonium and phosphonium based systems.RTILs now comprise a wide arry of sub classes including protic (PILs), basic (BILs), chiral (CILs), solid supported (SLIPs) and functionalised (FIL).[31,32] Key examples of these Ionic Liquids -Current State of the Art systems are shown in Figure 2. The custom design nature of these RTILs modifies their ability to solubulise materials and affects the outcome of a wide range of chemical transformations.Herein our focus is the Heck reaction.In addition to the variable nature of the RTIL, a number of novel Pd-catalysts have been developed to enhance the Heck coupling outcomes, especially with the use of deactivated aryl halides and olefins.Selected examples of these Pd-catalysts are also shown in Figure 2.
effect the desired coupling reaction (Figure 1). Figure 1.General reaction scheme of a Heck cross coupling between an aryl and an olefin indicating the four key solvent, catalyst and temperature.

Heck reaction in Room Temperature Ionic Liquids (RTILs)
The emergence of room temperature ionic liquids (RTILs) has allowed the investigation of the He range of novel and tuneable solvents systems.These novel solvents cover a wide range of structural moiefs from the now well established me pyridinium salts through ammonium and phosphonium based systems.RTILs now comprise a wi including protic (PILs), basic (BILs), chiral (CILs), solid supported (SLIPs) and functionalised (FIL).these systems are shown in Figure 2. The custom design nature of these RTILs modifies their materials and affects the outcome of a wide range of chemical transformations.Herein our focus is addition to the variable nature of the RTIL, a number of novel Pd-catalysts have been developed coupling outcomes, especially with the use of deactivated aryl halides and olefins.Selected e catalysts are also shown in Figure 2.
It was noted with Pd(OAc) 2 , that the addition of 1.5 eq. of NaOAc, improved the coupling rate, but decreased selectivity with 5% of the (Z)-isomer detected under these conditions.Also of note with this reaction sequence was the slow precipitation of Pd-clusters on use of PdCl 2 , but not with Pd(OAc) 2 .With Pd(OAc) 2 the catalyst remained soluble and viable, able to catalyse subsequent couplings on removal of the product from the previous catalytic cycle.It was proposed that the RTIL phosphonium salt stabilised the Pd(0) species obtained by in situ reduction of the Pd(II) catalyst precursors.This ligand free approach has attracted considerable interest and has purification benefits on reaction scale up.[51]

Ammonium RTILs
Tetraammonium salts are the archetypal ammonium based RTILs used in the Heck coupling, with the simplest being the tetrabutylammonium salts ([Bu 4 N][X]).Coupling of iodobenzene with arylacrylates gave an expedient synthesis of 3,3-diarylacrylates.This coupling was accomplished in good yield and regioselectivity in molten n-Bu 4 NOAc/n-Bu 4 NBr with Pd(OAc) 2 (Scheme 9).[52] It was noted with Pd(OAc)2, that the addition of 1.5 eq. of NaOAc, improved the coupling rate, but d with 5% of the (Z)-isomer detected under these conditions.Also of note with this reaction sequ precipitation of Pd-clusters on use of PdCl2, but not with Pd(OAc)2.With Pd(OAc)2 the catalyst re viable, able to catalyse subsequent couplings on removal of the product from the previous ca proposed that the RTIL phosphonium salt stabilised the Pd(0) species obtained by in situ reduction precursors.This ligand free approach has attracted considerable interest and has purification benef up. [51]
Others have noted the increased stability of the Pd-catalytic species in RTILs and have exploite mediated synthesis of β-arylcarbonyl compounds from allylic alcohols in [Bu4N]Br, affording (Sche of this simple procedure afforded a one-step synthesis of the nonsteroidal antiinflammatory d (Scheme 11) and allowed catalyst reuse. [53]  Figure 12.Reagents and conditions: PdCl2, NaHCO3, Bu4NBr, 120 ºC, 24 h. Figure 13.Reagents and conditions: PdCl2, NaHCO3 (1.2 equiv.),Bu4NBr, 120 ºC, 24 h.The Pd-benzothiazole carbene complex has been successfully used as the Pd-source (1.5 mol%), an the coupling of both electron rich and electron deficient trans-cinnamates in [Bu4N][Br] at 130 ºC formate and NaHCO3 (Scheme 12). [54], [55 The best yields were observed with NaOH and DBU and in reactions were complete in < 30 min.Others have noted the increased stability of the Pd-catalytic species in RTILs and have exploited this in the PdCl 2 mediated synthesis of β-arylcarbonyl compounds from allylic alcohols in [Bu 4 N]Br, affording (Scheme 10).[53] Extension of this simple procedure afforded a one-step synthesis of the nonsteroidal antiinflammatory drug (nabumethone), (Scheme 11) and allowed catalyst reuse.[53] It was noted with Pd(OAc)2, that the addition of 1.5 eq. of NaOAc, improved the coupli with 5% of the (Z)-isomer detected under these conditions.Also of note with this r precipitation of Pd-clusters on use of PdCl2, but not with Pd(OAc)2.With Pd(OAc)2 th viable, able to catalyse subsequent couplings on removal of the product from the proposed that the RTIL phosphonium salt stabilised the Pd(0) species obtained by in sit precursors.This ligand free approach has attracted considerable interest and has purif up. [51]
Others have noted the increased stability of the Pd-catalytic species in RTILs and h mediated synthesis of β-arylcarbonyl compounds from allylic alcohols in [Bu4N]Br, affo of this simple procedure afforded a one-step synthesis of the nonsteroidal antiinfla (Scheme 11) and allowed catalyst reuse. [53]  Figure 12.Reagents and conditions: PdCl2, NaHCO3, Bu4NBr, 120 ºC, 24 h.The Pd-benzothiazole carbene complex has been successfully used as the Pd-source (1.5 mol%), an the coupling of both electron rich and electron deficient trans-cinnamates in [Bu4N][Br] at 130 ºC formate and NaHCO3 (Scheme 12). [54], [55 The best yields were observed with NaOH and DBU and i reactions were complete in < 30 min.The Pd-benzothiazole carbene complex has been successfully used as the Pd-source (1.5 mol %), and easily recycled, in the coupling of both electron rich and electron deficient transcinnamates in [Bu 4 N][Br] at 130 °C with added sodium formate and NaHCO 3 (Scheme 12).[54,55] The best yields were observed with NaOH and DBU and in these instances the reactions were complete in < 30 min.Others have noted the increased stability of the Pd-catalytic species in RTILs and have exploited this in the PdCl2 mediated synthesis of β-arylcarbonyl compounds from allylic alcohols in [Bu4N]Br, affording (Scheme 10). [53]Extension of this simple procedure afforded a one-step synthesis of the nonsteroidal antiinflammatory drug (nabumethone), (Scheme 11) and allowed catalyst reuse. [53]  Figure 12.Reagents and conditions: PdCl2, NaHCO3, Bu4NBr, 120 ºC, 24 h. Figure 13.Reagents and conditions: PdCl2, NaHCO3 (1.2 equiv.),Bu4NBr, 120 ºC, 24 h.The Pd-benzothiazole carbene complex has been successfully used as the Pd-source (1.5 mol%), and easily recycled, in the coupling of both electron rich and electron deficient trans-cinnamates in [Bu4N][Br] at 130 ºC with added sodium formate and NaHCO3 (Scheme 12). [54], [55 The best yields were observed with NaOH and DBU and in these instances the reactions were complete in < 30 min.Motevalli's N-(diphenylphosphino)triethylammonium chloride (IL1) and N-(diphenylphosphino)tributylammonium chloride (IL2), have been used successfully in Heck couplings of iodobenzene and styrene (Figure 3 and Table 3). [56]  Sheme 12. Reagents and conditions: [Bu 4 N]Br, NaOAc, NaHCO 3 , 130 °C, Pd-cat.

Studies using imidazolium, pyridinium, phosphonium and ammonium RTILs
The coupling of electron poor chloroarenes with mono and di-substituted olefins across a range of RTILs and Pd-sources has been examined.[57] The model system, resulting in the synthesis of stilbene from chlorobenzene and styrene was best conducted with simple, e.g.PdCl 2 , phospha-based Pd-sources (Scheme 13).RTILs examined included: imidazolium, ammonium and phosphonium salts.The tetraalkylammonium salts, in particular [Bu 4 N][Br], were superior permitting the coupling of chloroarenes in the presence of less active catalysts such as PdCl 2 and Pd(Ph 3 P) 4 .Regardless of the conditions used, all imidazolium based RTILs gave poor results, e.g.22  and the resulting FILs used in the coupling of iodobenzene with methylacrylate.[58] The effect of anion on the coupling outcome was determined by screening using Pd 2 dba 3 .CHCl 3 and each of the phosphonium FILs in turn.High coupling efficiency was observed [P 6 , 6 , 6 , 14 ][CH 2 (CH 2 ) 8 CO 2 ] (75%) and [P 6 , 6 , 6 , 14 ][Cl] (78%), with [P 6 , 6 , 6 , 14 ][Cl] also providing a simpler work up.

Functionalized Ionic Liquids (FILs)
Functionalised (FILs) or, as they are sometimes know, task specific ionic liquids, incorporate additional functional moieties within the cation or anion.[61] FILs can be discrete liquids or be supported reagents and have applications as reagents and catalysts.[62]- [66] FILs have been examined as novel media for the Pd(OAc) 2 mediated Heck reaction of 2-methylprop-2-en- ].These outcomes correlate well with the relative basicity of these two FILs.The equivalent coupling in neat Hünig's base showed a conversion of 39%, supporting a catalytic role for the PILs.[67] The selectivity between 3-(4-tert-butylphenyl)-2-methylpropanal and 2-(4-tert-butylphenyl)-3methylpropanal was found to be >95% respect to β-Lilial ® and independent of the PIL basicity (Scheme 15).RTILs based on dialkylimidazolium salts have attracted particular attention, as they are easy to prepare and handle, having good solubility for many substrates and molecular catalyst and are readily synthesised through a variety of green chemistry approaches.Nitrile modified imidazolium and pyridinium salts have been used in Pd-catalysed crosscoupling reactions (Scheme 17).[72,73] These FILs are highly effective solvents for the Heck reaction with excellent yields observed (Table 4).[ Numerous studies have highlighted the deprotonation of imidazolium RTILs to yield an imidazol-2-ylidene N-heterocyclic carbene (NHC) as a crucial step in subsequent reactions complex generated by deprotonation of the ionic liquid cation.[75][76][77][78] Many transition-metal carbene complexes have been prepared and their catalytic applications described.[79,80] This has led to the evaluation of novel RTILs as catalysts in Pd-coupling reactions.[81,82]  Shreev, et al, synthesized the new RTIL, shown in (Scheme 21), which contain the dication 1,1'methylene-3,3'-dialkylbis(imidazolium) or 1,1'-methylene-4,'-dialkylbis(1,2,4-triazolium) with NTf 2 as the anion, and evaluated its efficacy in the Heck reaction (Table 5).[ In a related study Shreeve et al, also examined the use of a range basic RTILs as both the base and solvent for the Heck coupling of iodobenzene and butyl acrylate (see Figure 3 for chemical structutures of the BILs).With BILs, BIL-1, BIL-2 and BIL-3 quantitative conversion and regioselectivity was observed.All other BILs (BIL-4-BIL-8) displayed low to no reactivity under the conditions examined (Table 6).In this study, these results suggest that RTILs with pendant aliphatic tertiary amines are superior to the pyridinium salts.[93] 6. Heck reactions between butyl acrylate and iodobenzene in the presence of basic ionic liquid (BIL1-BIL8) (Fig. 3).
The novel imidazolium RTIL tagged Pd-Schiff base complex was active in both Heck and Suzuki couplings in aqueous media.Relative to other Pd-catalysted reactions in aqueous media, this catalyst was effective in the coupling of water insoluble aryl halides without the aid of a phase transfer catalyst or organic solvents (Scheme 22).[94] Optimised Heck coupling conditions required the use of 1 mol % catalyst, K 2 CO 3 and with iodobenznene and cyclohexyl acrylate gave benzyl cinnamate in 96% yield, (Scheme 23).
Chitosan supported Pd(OAc) 2 nanoparticles (Pd-NP) in TBAB with added tetrabutyl ammonium acetate (TBAA) gave rise to very rapid Heck couplings of aryl bromides, iodides and activated chlorides (Scheme 23).[95] The supported catalyst was amenable to multiple recycles, whereas the free nano particles rapidly lost activity.

Supported ionic liquid phase (SILP) catalyst system
Immobilisation of the Pd-catalyst and the RTIL onto high surface area porous solids such as silica yields a supported ionic liquid phase (SILP) catalyst system.SLIPs are considered, while being solids, to contain the active species comprise solubilized in the IL phase behaving as a homogeneous catalyst, and as such offer the potential for novel reactivity.Suzuki has examined this reactivity with a range of Pd(OAc) 2 /silica based SLIP catalyst systems.The SLIPs were air and thermally stable, provided simple storage conditions, easily recyclable and highly effective in the Heck coupling of substituted arylhalides with vinyl esters (Scheme 28).[101,102]  In a related study, Pd(OAc) 2 and [bmim][PF 6 ] were immobilized on reversed phase silica gels such as aminopropylated or N,N-diethylaminopropylated silica.[103] The Heck reaction between iodobenzene and cyclohexyl acrylate was carried out as shown in (Scheme 29).The catalyst was reused five times with no loss of catalytic activity.

Microwave synthesis approaches
Microwave heating has been applied to the Heck reaction in RTILs significantly reducing the time required to effect coupling, and influencing product yield and the extent of by-product generation.[106,110] Generally microwave approaches have focused on the use of aryl iodides Ionic Liquids -Current State of the Art and active aryl bromide, such as those reported by Larhed et al in [bmim][PF 6 ] (Scheme 32).[111] Using 4 mol % PdCl 2 (4 mol %), P(o-tolyl) 3 as the added Pd-ligand, reactions were complete after 5-45 min, at 180 -220 °C.The catalyst system and RTIL were and the time 20 minutes and 45 minutes for trans formations without the phosphine ligand.This system was recyclable at least five times, and the volatile product was directly isolated in high yield by rapid distillation under reduced pressure.[111] Sheme 31.Reagents and conditions: (i) 2 mol% PdCl2, [bbim][Br] or [bbim][BF4], 120 ºC, 1.5-3

Flow chemistry approaches
Micro reactor technology has and a significant impact on the chemical synthesis and production.This technology ha many advantages including: 1) highly efficient material mixing; 2) high volume to area ratio; 3) efficient heat transfer ability; 4) the avoidance of "hot spots" by effective temperature control and mixing; and 5) high operational safety. [11

Flow chemistry approaches
Micro reactor technology has and a significant impact on the chemical synthesis and production.This techn many advantages including: 1) highly efficient material mixing; 2) high volume to area ratio; 3) efficient hea ability; 4) the avoidance of "hot spots" by effective temperature control and mixing; and 5) high operational The transition metal catalysed reactions have been reported by using a micro flow system, such as hydrogenat oxidation, [121] and the Heck reaction. [122]  RTILs present a challenge for flow chemistry approaches due to their often-high viscosity.Ryu has examined t low viscosity RTIL, [bmim]NTf2 as well as a high viscosity RTIL, [bmim][PF6]. [122]The Heck coupling of iod with butyl acrylate was sluggish in [bmim][PF6], but the use of [bmim][NTf2] in a CPC CYTOS lab system ga of, and in a single run with catalyst recycling, 115.3g of buyl cinnamate (Scheme 38). [123]  Sheme 38.Reagents and conditions: 0.1-0.5 mL.h-1, [BMIM]NTf2, 130-150 ºC, 10-50 min residence time.

Conclusions
In the last twenty years has shown an increasing interest in applying ionic liquids as green solvents in organic This approach has been extended to the palladium-catalysed Heck reactions as a key synthetic protocol for formation.Factors affecting this approach including the type of ionic liquid used, the base and the catalyst investigated by many research groups.In addition, limited number of microwave-based and flow chemistry b reactions have been reported.Despite these efforts, only simple aryl halides and olefines were used in th investigations.Active research in this area is still required to increase the scope of Heck reaction in ILs to inv complicated substrates and larger scale.

Flow chemistry approaches
Micro reactor technology has and a significant impact on the chemical synthesis and production.This technology has many advantages including: 1) highly efficient material mixing; 2) high volume to area ratio; 3) efficient heat transfers ability; 4) the avoidance of "hot spots" by effective temperature control and mixing; and 5) high operational safety.[119] The transition metal catalysed reactions have been reported by using a micro flow system, such as hydrogenation [120] and oxidation, [121] and the Heck reaction.[122] RTILs present a challenge for flow chemistry approaches due to their often-high viscosity.Ryu has examined the use of a low viscosity RTIL, [bmim]NTf 2 as well as a high viscosity RTIL, [bmim][PF 6 ]. [122] The Heck coupling of iodobenzene with butyl acrylate was sluggish in [bmim][PF 6 ], but the use of [bmim][NTf 2 ] in a CPC CYTOS lab system gave 10 g.h -1 of, and in a single run with catalyst recycling, 115.3g of buyl cinnamate (Scheme 38).[123]

Flow chemistry approaches
Micro reactor technology has and a significant impact on the chemical synthesis many advantages including: 1) highly efficient material mixing; 2) high volume to ability; 4) the avoidance of "hot spots" by effective temperature control and mixin The transition metal catalysed reactions have been reported by using a micro flow s oxidation, [121] and the Heck reaction. [122]  RTILs present a challenge for flow chemistry approaches due to their often-high vis low viscosity RTIL, [bmim]NTf2 as well as a high viscosity RTIL, [bmim][PF6]. [

Conclusions
In the last twenty years has shown an increasing interest in applying ionic liquids a This approach has been extended to the palladium-catalysed Heck reactions as a formation.Factors affecting this approach including the type of ionic liquid used, investigated by many research groups.In addition, limited number of microwave-b reactions have been reported.Despite these efforts, only simple aryl halides and investigations.Active research in this area is still required to increase the scope of complicated substrates and larger scale.

Conclusions
In the last twenty years has shown an increasing interest in applying ionic liquids as green solvents in organic synthesis.This approach has been extended to the palladium-catalysed Heck reactions as a key synthetic protocol for C-C bond formation.Factors affecting this approach including the type of ionic liquid used, the base and the catalyst have been investigated by many research groups.In addition, limited number of microwave-based and flow chemistry based Heck reactions have been reported.Despite these efforts, only simple aryl halides and olefines were used in the reported investigations.Active research in this area is still required to increase the scope of Heck reaction in ILs to involve more complicated substrates and larger scale.

Figure 1 .
Figure 1.General reaction scheme of a Heck cross coupling between an aryl and an o solvent, catalyst and temperature.

Figure 1 .
Figure 1.General reaction scheme of a Heck cross coupling between an aryl and an olefin indicating the four key variables: base, solvent, catalyst and temperature.

Figure 2 .
Figure 2. Selected examples of ionic liquids and Pd-catalysts used in the Heck reaction.

Figure 2 .
Figure 2. Selected examples of ionic liquids and Pd-catalysts used in the Heck reaction.

Figure 4 .
Figure 4.Chemical structures of Basic ionic liquid cations.

Table 2 .
Selected results for Heck reaction between the listed arylhalides and ethyl acrylate o [Bmim]BF4.
a reaction with ethyl acrylate, b reaction with butyl acrylate.Yokoyama showed that heating an aryl substrate, olefin and 3 mol% of 10% Pd good yields of the Heck coupling product (Scheme 2).Product isolation was by e RTIL and catalyst without loss of coupling efficiency.[35]

Table 4 .
Selected examples of the Heck Coupling of Iodobenzene with ethyl acrylate in [C 3 CNmim][Tf 2 N] at 80 °C.
Metal-NHC complexes have been generated and examined in RTILs, with the metal-NHC complex reactivity examined for Heck coupling efficacy in DMF and [bmim][NTf 2 ] based of an NHC located from an ionic liquid cation and investigate the catalytic activity in both molecular and ionic liquid solvents in the Heck coupling of butyl acrylate and bromobenzene (Scheme 18).Reagents and conditions: (i) NH 2 , CH 2 O, CuCO 3 ; (ii) BuBr, KOtBu, EtOH; (iii) MeI, CH 2 Cl 2 ; Metal-X.Use of these fructose derived PILs in the Pd(OAc) 2 mediated Heck coupling of methyl acrylate with iodobenzene afforded rapid conversion (1 h) to methyl cinnamate in > 95% yield at 100 °C (Scheme 20).Both the PIL and catalyst were readily recycled with no loss of activity.

Table 5 .
Heck cross-coupling reactions in the ionic liquid-3 and different anions (X) with selected aryl halides and butyl acrylate.