Article pubs.acs.org/Organometallics
Iridium-Promoted Conversion of Chlorosilanes to Alkynyl Derivatives in a One-Pot Reaction Sequence Ireneusz Kownacki,*,† Bartosz Orwat,† and Bogdan Marciniec*,†,‡ †
Faculty of Chemistry, Adam Mickiewicz University in Poznań, Umultowska 89b, 61-614 Poznań, Poland Center of Advanced Technology, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland
‡
S Supporting Information *
ABSTRACT: By making use of the catalytic potential of the iridium system [{Ir(μ-Cl)(CO)2}2]/NEt(i-Pr)2 in the synthesis of silyl-functionalized alkynes via silylative coupling of terminal alkynes/diynes with iodosilanes, we propose a new protocol allowing employment of various mono- and dichlorosilanes as reagents. The process is based on a sequence of two reactions occurring simultaneously: i.e., conversion of initial chlorosilane (SiR1nCl4−n) to the appropriate iodosilane via Cl/I nucleophilic substitution and its further conversion to a silylalkyne derivative ((SiR1n(CCR2)4−n) via iridium-catalyzed silylative coupling with terminal alkyne. Under optimum conditions, the method has proved to be effective and versatile in the conversion of a wide range of chlorosilanes to a rich portfolio of various corresponding alkynyl-functionalized silicon derivatives. Additionally, NMR studies of the equimolar reaction of a well-defined iridium(I) alkynyl precursor with Me3Si−I revealed that Si−I bond activation in iodosilane molecules occurred via oxidative addition to the iridium center.
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CH)12 and triorganosilylacetylides ([M(CCSiR3)n]: M = MgX, n = 1; M = In, n = 3; M = ZnCl, n = 1)13 with halogenofunctionalized organic compounds, or similar nickel-catalyzed reactions14 yielding silylethynyl-functionalized aryl derivatives. Our group has also contributed to the development of new catalytic methods for the synthesis of silyl-functionalized terminal alkynes particularly through Si−Csp bond formation, with employment of vinylsilanes as silylation agents.15 Since 2006, a series of papers have been published, devoted to the synthesis of silylalkynes via the ruthenium- or rhodiumcatalyzed coupling of terminal aliphatic or silyl alkynes (RC CH) with various vinylsilanes (R3SiCHCH2).15 Recently, we have also reported a new and efficient catalytic route for the silylation of terminal alkynes/diynes by trisubstituted iodosilanes, promoted by an iridium(I) carbonyl precursor in the presence of a tertiary amine (Scheme 1).16,17
INTRODUCTION Efficient synthesis of silyl-functionalized alkynes is of great interest in organic and material chemistry because currently derivatives of this type are increasingly being used as stable and convenient synthons of alkynyl carboanions. The latter can be successfully applied as essential components for preparation of organic and natural products,1 as well as conjugated oligomers and polymers for the construction of electronic or optoelectronic materials containing a linear carbon−carbon triple bond in their structure, liquid crystals, nonlinear materials, molecular wires, and other engineering materials.2 The known methods, commonly used in the preparation of various alkynylsilanes, are based on two different pathways: namely, silyl functionalization of terminal alkynes via Si−Csp bond formation or incorporation of a whole silylethynyl function (−CCSiR3) with C−C bond creation. The first group includes methods employing the equimolar reactions of various chlorosilanes (SiClnR4−n),3 alkoxysilanes,4 or aminosilanes5 with organometallic species of the type MCCR′ (M = Li, MgX, where X = Cl, Br), as well as those that rely on zinc or zinc salt promoted coupling of terminal alkynes with aminosilanes, 6a chlorosilanes, 6b−d Me 3 SiOTf 6e (OTf = −O3SCF3) or trisubstituted silanes (SiR3H),6f and comprise also transition-metal-mediated reactions such as terminal alkyne dehydrogenative silylation with hydrosilanes,7 rutheniumpromoted coupling with chlorosilanes,8 palladium-catalyzed coupling with SiMe3CF3,9 or SiMe3OTf.10 On the other hand, the second group comprises methods that use the equimolar reactions of lithium triorganosilylacetylides (Li+−CCSiR3) with a wide range of ketones that lead to the formation of appropriate hydroxyl-functionalized aliphatic silylalkynes,11 catalytic processes such as palladiumpromoted cross-coupling of various silylalkynes (R3SiC © XXXX American Chemical Society
Scheme 1. Iridium-Promoted Silylative Coupling of Terminal Alkynes with Trisubstituted Iodosilanes
It has been shown that the iridium(I) catalytic system works perfectly only if a Si−I bond is present in the organosilicon reagent. Unfortunately, iodosilanes are less common and less stable than other halosilanes. A number of methods are available for the synthesis of such derivatives; some of them are based on PdCl2-catalyzed H/I exchange18 in hydrosilanes or Received: March 24, 2014
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nucleophilic substitution of the chlorine atom in chlorosilanes with iodide anions in a polar solvent system.19 In view of the literature devoted to the synthesis of iodosilanes, we are extraordinarily interested in the method consisting of substitution of a chlorine atom in the initial chlorosilane by an iodide anion19 with employment of inorganic salts (alkali-metal iodides). In organic chemistry, this type of process is known as the Finkelstein reaction,20 and it is commonly used for the preparation of organic iodo derivatives by reaction of alkyl chlorides or bromides with NaI in acetone solution. In this paper we present the results of our studies focused on the design of a catalytic system, based on the discovered iridium-promoted coupling reaction,16,17 enabling conversion of chlorosilanes to a wide variety of appropriate alkynylsilanes. Furthermore, mechanistic considerations based on the results of spectroscopic studies of the equimolar reaction of a welldefined iridium(I) complex with SiMe3I are also presented.
Table 1. Coupling of Trichloro-Substituted Silanes with Phenylacetylenea
Reaction conditions: [R3SiCl]:[PhCCH]:[M+I−]:[NEt(i-Pr)2]:[Ir] = 1:1.2:1.2:1.6:10−2, 80 °C, 24 h. The conversion and yield were determined by GC analysis and calculated using decane as a internal standard.
a
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RESULTS AND DISCUSSION As mentioned above, only iodosilanes can be used as silylation agents because chlorosilanes as well as bromosilanes appeared unreactive in this process. Therefore, in our study, we applied the Finkelstein method for the creation of a system that would allow combining a sequence of two reactions in a one-pot protocol: i.e., in situ transformation of chlorosilane (SiRnCl4‑n) to a corresponding iodosilane and its further conversion to silylalkyne derivative ((SiRn(CCR′)4−n) via iridium-catalyzed silylative coupling with terminal alkyne. However, to find the best inorganic reagent/solvent system allowing the reaction sequence, i.e. conversion of the initial chlorosilane to the appropriate iodosilane via Cl/I exchange and iridium-promoted silylative coupling of the iodosilane formed with terminal alkyne, as well as to recognize the efficiency of the iridium catalytic system in the alkyne silylation process in a one-pot protocol, a series of silylative coupling tests was performed (Scheme 2). The tests were aimed at optimizing the reaction
chlorosilanes (SiR3Cl) significant amounts of undesirable byproducts formed such as R3SiCH2CN, (R3Si)2CHCN, and [CH3CN+SiR3]I−.19a Similarly, as noted for MeCN, the use of other polar solvents such DMF and NMP also led to the formation of unwanted side products. The results compiled in Table 1 demonstrate that under typical reaction conditions (see footnote a) the presence of the inorganic salt has no deactivating effect on the efficiency of the iridium catalyst used (for comparison see refs 16 and 17). It should also be noted that Cl/I nucleophilic substitution is an equilibrium reaction, which can be driven to completion by the differential solubility of halide salts or by use of a large excess of the halide salt.21 In the case of our one-pot process, it is not necessary to use a large excess of iodide salts because the concentration of iodosilane formed is decreasing continuously during the consecutive catalytic process, i.e. iridium-catalyzed silylation of the alkynyl moiety; therefore, formally the equilibrium is continuously shifted toward the formation of iodosilane. Therefore, for further studies on the iridium-promoted conversion of various chlorosilanes to the corresponding alkynyl functionalized silicon derivatives, the system based on LiI/α,α,α-trifluorotoluene was chosen. The results compiled in Tables 2−4 demonstrate the versatility of the one-pot protocol in the conversion of a wide range of chlorosilanes to a rich portfolio of the corresponding alkynyl-functionalized silicon derivatives, according to Scheme 3:
Scheme 2. Silylation of Phenylacetylene by SiR3Cl in a OnePot Reaction Sequence
conditions under which various trisubstituted chlorosilanes (SiR3Cl) in situ were converted to the appropriate iodosilanes (SiR3I) by reaction with two selected iodide salts (NaI and LiI) in different polar solvents as the reaction medium. The results of screening for selected trisubstituted chlorosilanes and polar solvents, compiled in Table 1, have confirmed that the initial chlorosilane only in combination with the group 1 metal iodides (NaI, LiI) can react with terminal alkyne in the presence of iridium(I) precatalyst. The highest yield of silylated phenylacetylene was possible to obtain only with three reagent systems: i.e., SiMe3Cl/NaI in MeCN (entry 2) and SiMe3Cl/LiI and SiMe2PhCl/LiI in α,α,αtrifluorotoluene (entries 6 and 8, respectively). The use of MeCN as a reaction medium allowed obtaining the silylation product in high yield only when SiMe3Cl was employed as a silylation agent. Unfortunately, in the case of other
Scheme 3. Coupling of Mono- and Dichlorosilanes with Terminal Alkynes
Under the optimum conditions (see Table 2, footnote a) this protocol was successfully applied to the coupling of vinylfunctionalized monochlorosilanes with PhCCH and Me3SiCCH, giving desirable products in a quantitative manner (entries 1−4). B
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Considering the results shown in Tables 1 and 2, the proposed method seems to be general and can be efficient also for the alkynylation of dichloro-substituted silicon derivatives having also two chloro substituents at one silicon atom (gem position) (Table 3, entries 1−13). The examples presented in Table 3 show that iridium-promoted silylative coupling via a sequence of two reactions under one-pot conditions can be successfully used for the preparation of a wide range of bisalkynyl silicon compounds, with employment of various dichlorosilanes, even those containing a reactive vinyl group at silicon (entries 9−11), as well as in combination with a terminal alkyne containing a reactive functional group such as −B(OCMe2CMe2O) in its structure (entries 7, 8, and 11 in Table 3). For most of the dichloro silicon reagents presented in Table 3, except for ClMe2SiOSiMe2Cl (entries 12 and 13), the bis-alkynylation process with the use of selected terminal alkynes (PhCCH, Me 3 SiCCH, (OCMe 2 CMe 2 O)-
Table 2. Coupling of Selected Vinyl-Substituted Monochlorosilanes with Exemplary Terminal Alkynesa
a
Reaction conditions: [SiR3Cl]:[R1CCH]:[LiI]:[NEt(i-Pr)2]:[Ir] = 1:1.4:1.2:1.6:10−2, C6H5CF3, 90 °C, argon, 24 h. The conversion and yield were determined by GC analysis and calculated using the solvent as a standard. bYield of isolated product in parentheses.
Table 3. Coupling of Dichlorosilicon Derivatives with Selected Terminal Alkynes under One-Pot Reaction Conditionsa
Reaction conditions (unless stated otherwise): [SiR2Cl2]:[R1CCH]:[LiI]:[NEt(i-Pr)2]:[Ir] = 1:2.8:2.4:3.2:2 × 10−2, C6H5CF3, 90 °C, argon, 24 h. the The conversion and yield were determined by GC analysis and calculated using the solvent as a standard. bReaction conditions: [SiR2Cl2]: [R1CCH]:[LiI]:[NEt(i-Pr)2]:[Ir] = 1:2.06:2.4:3.2:2 × 10−2, C6H5CF3, 90 °C, argon, 24 h. cYield of isolated product in parentheses. a
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equiv of SiMe2Cl2 or 1 equiv of SiPh2Cl2 leads to selective formation of coupling products in a good yield (Table 4). The products contain in their structure the remaining one chloro substituent, in addition to the alkyne functional group, as shown in Scheme 4.
BC6H4CCH) led to complete conversion of the dichlorosubstituted silane, giving the desired products in very high yield. Considering the results shown in Tables 2 and 3, it can be concluded that the presence of a vinyl group in the chlorosilicon reagent, most likely due to its electronic properties, promotes the Cl/I exchange process as well as the coupling of iodosilane formed with terminal alkynes. On the other hand, as demonstrated by entries 12 and 13 in Table 3, the presence of siloxane moieties, presumably due to the dπ− pπ interaction between the oxygen atom and the silicon atoms, makes the latter less reactive in nucleophilic substitution by iodide anions, as well as in the Si−I bond activation process (a result of these effects), which is reflected in significantly lower yields of the expected products. Generally, the literature data concerning the synthesis of alkynyl- and bis-alkyl-functionalized vinylsilanes are very scarce, including those on silicon derivatives containing in their structures other functional groups, such as −B(OCMe2CMe2O). Very recently we have reported the preparation of mono- and bis-alkynylsilanes via iridium-catalyzed coupling of terminal alkynes with various iodo- and diiodosilanes,17b which were prepared in a catalytic manner.18 This method proved to be very efficient for simple iodosilanes; however, for the preparation of vinyl-functionalized mono- and diiodosilanes it seems to be problematic, because the synthesis of appropriate vinyl-functionalized iodo- and diiodosilanes requires several steps, including the preparation of Si−H derivatives (H2C CHSiHnR3−n) by reduction of the corresponding chlorosilanes (H2CCHSiClnR3−n or HCCHSiClnR3−n) with LiAlH422 and then palladium-catalyzed H/I substitution.18 However, as palladium compounds are also well-known as hydrosilylation catalysts,23 the use of PdCl2 as an H/I exchange catalyst in H2CCHSiHnR3−n also could lead to the formation of undesirable polyhydrosilylation products. The synthesis of mono- and bis-alkynyl silanes, according to the previously used method,17b would require two additional steps, i.e. Cl/H substitution and Pd-catalyzed H/I exchange, and it would not guarantee a high yield of the expected products. The one-pot protocol proposed has significant advantages over the previously used method,17b because it allows the direct application of chlorosilanes in the generation of the corresponding iodosilicon derivatives without any additional steps and simultaneous coupling with terminal alkynes in a single batch. It seems that in all aspects, especially the availability of chlorosilanes, the method that allows direct application of chlorosilanes in the generation of the corresponding iodo derivatives seems to be the most convenient, practical, and atom economical. We think that, in comparison with other methods, our onepot system is more convenient also for the synthesis of alkynyl silanes, particularly those containing in their structure one or more −B(OCMe2CMe2O) functional groups, because all of the substrates are commercially available (SiRnCl4−n, Si(CH CH2)RnCl3−n, (OCMe2CMe2O)BC6H4CCH) unlike the reagents necessary for carrying out the multistep synthesis via Sonogashira protocol in combination with conventional synthetic pathways: 24 e.g., B(OCMe 2 CMe 2 O)(O-i-Pr)SiR2(CCH)2, BrC6H4B(OCMe2CMe2O), BrC6H4B4C CSiMe3, etc. Surprisingly, it was also found that, for dichloro-substituted silanes, the use of a ratio of 1 equiv of terminal alkyne to 3
Table 4. Selective Monocoupling of Dichloro-Substituted Silanes with Selected Terminal Alkynesa
a Reaction conditions (unless stated otherwise): [SiR12Cl2]:[R2C CH]:[LiI]:[NEt(i-Pr)2]:[Ir] = 3:1:1:1.6:2 × 10−2, 90 °C, argon, 48 h. The conversion and yield were determined by GC analysis and calculated using the solvent as a standard. bReaction conditions: [SiR12Cl2]:[R2CCH]:[LiI]:[NEt(i-Pr)2]:[Ir] = 1:1:1:1.6:2 × 10−2. c Yield of isolated product in parentheses.
Scheme 4. Synthesis of Chloro- and Alkynyl-Substituted Silanes
Thus, the developed one-pot method allows the selective conversion of dichloro silicon compounds not only to bisalkynyl derivatives but also to alkynyl-functionalized chlorosilanes in one step. It should be noted that the synthesis of such silicon derivatives may not be difficult but may be very timeconsuming because it requires to carry out several noncatalytic steps with isolation and purification of all intermediates.25 All of the mono- and bis(alkynyl)-functionalized silicon derivatives presented in Tables 2−4 were isolated and characterized by spectroscopic methods (see the Supporting Information), to show the scope of this new versatile and efficient synthetic method. Mechanistic Considerations. Our previous publication gave the results and discussion of a preliminary study on the reactivity of the initial iridium(I) precursor ([{Ir(μ-Cl)(CO)2}2]) in sequential reactions with each of the substrates in the equimolar systems, in addition to catalytic data concerning silylation of terminal alkynes/diynes by SiMe3I.17a The outcomes presented in the cited paper have unambiguously proven that the activation of the Csp−H bond in a terminal alkyne by an iridium(I) metallic center and formation of [Ir(H)(CCR)] species is the key step of this new coupling reaction. On the basis of these studies, we have proposed a possible mechanism for this process, in which the first catalytic run involves the transformation of the initial precursor [{Ir(μCl)(CO)2}2] (I) to the four-coordinated complex [Ir(Cl)(CO)(NR′3)2] (II) in the presence of a tertiary amine. In a D
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Scheme 5. Transformation of Iridium Precursor I to Alkynyl Species IV via a Csp−H Bond Activation Step
Scheme 6. Equimolar Reaction of IVa with Iodotrimethylsilane
resonances at 131.20, 129.84, 125.17, and 121.61 ppm were assigned to a phenyl substituent bonded to the alkynyl moiety that gave two doublets located at 126.42 ppm (2JC−P = 13.5 Hz) and 83.23 ppm (3JC−P = 12.6 Hz). The line at 67.30 ppm was assigned to olefinic carbon atoms of the cyclooctadiene ligand. In the 31P NMR spectrum a resonance at 19.53 ppm was detected. The reaction of complex IVa with model iodosilane (SiMe3I) (Scheme 6) enabled us to identify the six-coordinate iridium(III) complex Va. Adding 1 equiv of SiMe3I to a solution of complex IVa and conducting the reaction at room temperature for 24 h did not result in visible changes in the spectroscopic picture of the resulting reaction mixture. Only in the 1H NMR and 13C NMR spectra was the appearance of new singlets at 0.50 and 5.35 ppm, respectively, coming from SiMe3I, observed. Heating the reaction mixture at 50 °C for 24 h resulted in a number of significant changes in the 1H, 13C, and 31P NMR spectra, confirming the transformations of the initial iridium(I) complex. After this time, the 1H NMR spectrum was found to reveal new resonance lines located in the area of chemical shifts characteristic of aromatic protons (in the ranges 7.47−7.44 and 7.00−6.94 ppm) and alkenyl protons of the cod ligand (multiplets at 5.58 and 5.42 ppm) as well as a multiplet at 3.28 ppm for protons of cod-allyl positions. Additionally, a new singlet was detected at 0.13 ppm, which was assigned to the Me3Si− moiety bonded to the iridium center. In the 13C NMR spectrum, two doublets at 128.76 ppm (2JC−P =
further step, this iridium species reacts with terminal alkyne via oxidative addition of the C−H bond, giving the sixcoordinated alkynyl−hydride iridium(III) complex III (structure determined by X-ray analysis when pyridine was used as NR′3),17a which in the presence of a tertiary amine is transformed to four-coordinated iridium(I) alkynyl derivatives IV with evolution of ammonium chloride, as shown in Scheme 5. In this mechanism, on the basis of sequential reactions, we have postulated that the activation of the Si−I bond in the silicon reagent molecules also plays an important role in the silylation process, but we did not have evidence regarding the mechanism of Si−I activation. It may take place by two possible mechanisms: namely, σ-bond metathesis or oxidative addition of the Si−I bond to the iridium center with formation of the iridium(III) species IV with iodide and silyl ligands bonded to the metallic center. In order to confirm one of the aforementioned theses, the equimolar reaction of the well-defined iridium(I) alkynyl complex [Ir(cod)(PCy3)(C CPh)]26 (IVa) with SiMe3I was performed and monitored by 1 H, 13C, and 31P NMR techniques. In the 1H NMR spectrum of the initial complex IVa, the resonances at 7.42 (d), 7.16 (t), and 6.97 (t) ppm were assigned to phenyl group protons of alkynyl ligand. The signals located at 5.26 and 3.75 ppm and the multiplet at 2.41 ppm were assigned to a cyclooctadiene ligand bonded to the iridium center. In the 13C NMR spectrum the E
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12.1 Hz) and 87.96 ppm (3JC−P = 13.09 Hz) coming from the ethynylene moiety and three singlets at 132.25, 128.53, and 123.81 ppm assigned to the phenyl ring of the phenylethynylene ligand in the new complex formed were found (compare with data for the initial complex IVa). In addition, a singlet at 53.96 ppm assigned to the alkenyl carbons of the cod ligand in the new complex formed as well as a singlet at 2.22 ppm coming from the Me3Si− ligand were found. In the 31P NMR spectrum, in addition to the resonance line derived from the initial complex (19.57 ppm), an additional line at 14.72 ppm was observed and assigned to the PCy3 ligand bonded to the iridium(III) center in the new six-coordinated complex. It should also be noted that in the 13C NMR spectrum, apart from the signals characteristic of the six-coordinated complex, the appearance of singlets at 106.04 and 94.33 ppm, typical of the ethynylene moiety present in the coupling product formed (PhCCSiMe3), was also observed (see Scheme 6). The presence of trimethylsilylphenylacetylene in the reaction mixture is direct evidence of the next step in the proposed mechanism, involving the conversion of the six-coordinate complex Va, shown in Scheme 6, to the four-coordinated iodide complex VIa with the release of the coupling product. The 1H, 13 C, and 31P NMR spectra, recorded 48 h after introduction of an additional 2 equiv of Me3Si−I to the reaction mixture, showed a substantial increase in the intensity of the aforementioned resonance lines. These spectra confirmed a significant shift of the equilibrium toward the six-coordinate complex, which is the product of oxidative addition of iodosilane to the initial complex IVa (see the Supporting Information). In summary, the stoichiometric studies described above prompted us to propose the coupling reaction mechanism shown in Scheme 7, in which we assume that the IrI alkynyl species IV, generated according to Scheme 5, is a real catalyst that initiates the reaction between iodosilanes and alkynes. Considering the above, we assume that in the first step complex IV reacts with SiR″3I via Si−I two-electron oxidative addition, which results in the formation of complex V, which
further is transformed to compound VI with the release of silylalkyne. The next stage of the cycle involves the C−H bond activation process, which occurs during the reaction of terminal alkyne with the four-coordinated complex VI. It leads to the formation of alkynyl−hydride species VII, which in the presence of tertiary amine is converted to the initial iridium alkynyl complex IV with evolution of ammonium salt according to a dehydrohalogenation process.27
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CONCLUSIONS The catalytic protocol created on the basis of the one-pot tworeaction sequence, namely in situ generation of the corresponding iodosilane from the initial chlorosilane (SiRnCl4−n) and its coupling with terminal alkyne in the presence of iridium catalyst, appeared to be very efficient and versatile in the conversion of a wide range of chlorosilanes to the appropriate alkynyl-functionalized silicon compounds. Under optimum reaction conditions, the one-pot method proposed allowed the synthesis of various mono-alkynylfunctionalized (R3SiCCR1) and bis-alkynyl-functionalized silicon derivatives ([Si](CCR1)2) as well as monoalkynyl chloro silanes (R13SiCl(CCR2)) in high yield. Most of the obtained compounds were isolated and characterized by spectroscopic methods. Moreover, an NMR study of the equimolar reaction between a well-defined iridium(I) alkynyl complex and SiMe3I gave evidence of Si−I bond activation in the iodosilanes via oxidative addition to the iridium center. This has enabled us to propose a plausible mechanism of alkyne silylative coupling with iodosilanes derived from chlorosilanes.
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EXPERIMENTAL SECTION
All synthesis and manipulations were carried out under argon using standard Schlenk-line and vacuum techniques. The chemicals were obtained from the following sources: IrCl3·3H2O from Pressure Chemicals, cod, C6D6, CDCl3, DMF, THF, decane, NEt(i-Pr)2, Me3SiI, NaI, LiI, MeCN, C6H5CF3, PhCCH, and (OCMe2CMe2O)BC6H4CCH from Aldrich, SiEt3Cl, SiMe2PhCl, SiMe2Cl2, SiPh2Cl2, H2CCHSiMe2Cl, H2CCHSiPh2Cl, and H2CCHSiMeCl2 from ABCR, CO (class 4.7) from Linde Gas. The complexes [{Ir(μCl)(cod)}2]28 and [{Ir(μ-Cl)(CO)2}2]29 were synthesized according to the published methods. All solvents and liquid reagents were dried and distilled under argon prior to use. The NMR spectra in the liquid phase were recorded in CDCl3 or benzene-d6 using 300 and 600 MHz spectrometers and referenced to the residual protonated solvent peaks (1H δH 7.26 ppm and 13C, δC 77.16 ppm for CDCl3 and 1H δH 7.16 ppm and 13C δC 128.05 ppm for benzene-d6) or external Si(CH3)4. The compound purity was determined by elemental analysis. The GC analyses were performed on gas chromatography apparatus equipped with a TCD detector and capillary column VF-5 (30 m × 0.53 mm). Products were identified by GC/MS equipped with a VF-5 column (30 m × 0.25 mm) and ion trap mass detector. General Procedure for Catalytic Tests. A thick-walled vacuum glass Schlenk reactor (25 mL) equipped with a magnetic stirring bar was evacuated and flushed with argon. Then, the calculated amount of M+I− (M = Na, Li) (6 mmol) and 10 mL of solvent were placed in the reactor. Then, to the mixture obtained were successively added SiR3Cl (5 mmol), NEt(i-Pr)2 (8 mmol), PhCCH (6 mmol), decane (10% of initial liquid substrates volume), and the complex [{Ir(μCl)(CO)2}2] (0.025 mmol) under a flow of argon. The reactor was placed in an oil bath, and the reaction was conduced at a given temperature. The reaction mixture was analyzed by GC and GC/MS at the beginning and after 24 h. The conversion and yield were calculated using the internal standard calculation method. General Procedure for Silylative Coupling of Terminal Alkynes with Chlorosilanes. A thick-walled vacuum glass Schlenk
Scheme 7. Proposed Mechanism of Terminal Alkyne Silylative Coupling with in situ Generated Iodosilanes
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Organometallics
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300 K): δ (ppm) 136.87, 135.17, 133.45, 132.92, 132.19, 129.88, 128.99, 128.25, 127.98, 122.67 (Ph and SiCHCH2), 109.33 ( SiCC), 88.46 (SiCC). 29Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −31.86. Synthesis of [(Trimethylsilyl)ethynyl]diphenylvinylsilane, SiPh2(CCSiMe3)(CHCH2) (4; Table 2). Following the procedure used for preparation of compound 1 (Table 2), a reaction was carried out with 1.93 g (14.4 mmol) of LiI, 2.94 g (12 mmol) of Si(H2C CH)Ph2Cl, 1.65 g (16.8 mmol) of Me3SiCCH, and 2.48 g (19.2 mmol) of NEt(i-Pr)2 in the presence of 34.04 mg (0.06 mmol) of the complex [{Ir(μ-Cl)(CO)2}2]. A 3.53 g amount of [(trimethylsilyl)ethynyl]diphenylvinylsilane was obtained (yield 96%). Anal. Calcd for C19H22Si2: C, 74.44; H, 7.23. Found: C, 74.50; H, 7.26. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.70 (m, 4H, m-Ph); 7.43 (m, 6H, o,pPh); 6.48 (dd, 1H, SiCHCH2); 6.30 (dd, 1H, SiCHCH2); 6.03 (dd, 1H, CH2); 0.29 (s, 9H, SiMe3). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 136.98, 135.27, 133.45, 132.97, 129.98, 128.08, (Ph and SiCHCH2), 119.46 (SiCC), 107.47 (SiCC), −0.01 (SiMe3). 29Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −17.97 (SiMe3), −33.23 (SiPh2). Synthesis of Dimethyl[bis{(4-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)phenyl)ethynyl}]silane, SiMe 2 [CCC 6 H 4 B(OCMe2CMe2O)]2 (7; Table 3). Following the methodology used for preparation of compound 1 (Table 2), a reaction was carried out in 10 mL of C6H5CF3 with 0.96 g (7.2 mmol) of LiI, 0.39 g (3 mmol) of SiMe2Cl2, 1.41 g (6.18 mmol) of (OCMe2CMe2O)BC6H4CCH, and 1.24 g (9.6 mmol) of NEt(i-Pr)2 in the presence of 17.02 mg (0.03 mmol) of the complex [{Ir(μ-Cl)(CO)2}2]. After completion of the reaction, in order to remove the catalyst and ammonium salt from the reaction mixture, the solvent and unreacted substrates were evaporated at reduced pressure and then 30 mL of Et2O was added. The resulting suspension was filtered off, and the resulting deposit was rinsed with two additional portions of Et2O. The solvent was initially evaporated from the filtrate. The residual product was sublimated under vacuum, and 1.38 g of dimethyl[bis{4-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2yl)phenylethynyl)]silane was obtained (yield of 90%). Anal. Calcd for C30H38B2O4Si;: C, 70.33; H, 7.48. Found: C, 87.52; H, 5.29. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.74 (d, 3JH−H = 8.1 Hz, 4H, C6H4); 7.50 (d, 3JH−H = 8.1 Hz, 4H, C6H4); 1.34 (s, 24H, B(OCMe2CMe2O)); 0.48 (s, 6H, SiMe2). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 134.58; 131.42; 125.41; 106.14 (CCSiMe3); 92.04 (CCSiMe3); 84.13 (B(OCMe2CMe2O)); 25.04 (B(OCMe2CMe2O)); 0.59 (SiMe2). 29Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −39.22. Synthesis of Diphenyl[bis{(4-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)phenyl)ethynyl)]silane, SiPh 2 [CCC 6 H 4 B(OCMe2CMe2O)]2 (8; Table 3). Following the methodology used for preparation of compound 1 (Table 2), a reaction was carried out in 10 mL of C6H5CF3 with 0.96 g (7.2 mmol) of LiI, 0.76 g (3 mmol) of SiPh2Cl2, 1.41 g (6.18 mmol) of (OCMe2CMe2O)BC6H4CCH, and 1.24 g (9.6 mmol) of NEt(i-Pr)2 in the presence of 17.02 mg (0.03 mmol) of the complex [{Ir(μ-Cl)(CO)2}2] After completion of the reaction, in order to remove the catalyst and ammonium salt from the reaction mixture, the solvent and unreacted substrates were evaporated at reduced pressure and then 30 mL of Et2O was added. The resulting suspension was filtered off, and the resulting deposit was rinsed with two additional portions of Et2O. The solvent was initially evaporated from the filtrate. The residual product was purified by a flash column filled with silica using hexane/Et2O (93/7%) as the mobile phase. After purification 1.66 g of diphenyl[bis{4-(4,4,5,5-tetramethyl-1,3,2dioxoboran-2-yl)phenylethynyl)]silane was obtained (yield 87%). Anal. Calcd for C40H42B2O4Si: C, 75.48; H, 6.65. Found: C, 75.57; H, 6.70. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.85 (m, 4H, m-Ph); 7.76 (d, 3JH−H = 8.1 Hz, 4H, C6H4); 7.57 (d, 3JH−H = 8.1 Hz, 4H, C6H4-); 7.43 (m, 6H, o,p-Ph); 1.34 (s, 24H, Me). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 135.09; 134.61; 132.97; 131.61; 130.43; 128.26; 125.13 (Ph, C6H4); 108.94 (CCSiPh2); 89.04 (C CSiPh2); 84.18 (B(OCMe2CMe2O)); 25.03 (B(OCMe2CMe2O)). Synthesis of Methyl[bis(phenylethynyl)]vinylsilane, SiMe(CCPh)2(CHCH2) (9; Table 3). Following the procedure used for
reactor (50 mL) equipped with a magnetic stirring bar was evacuated and flushed with argon. Then, the calculated amount of Li+I− and 20 mL of anhydrous and deoxidized C6H5CF3 were placed in the reactor. Then to the mixture obtained were successively added SiRnCl4−n, NEt(i-Pr)2, RCCH, and the complex [{Ir(μ-Cl)(CO)2}2] under a flow of argon. The reactor was placed in an oil bath, and the reaction was conduced at a given temperature. The reaction mixture was analyzed by GC and GC/MS prior to the reaction and after 24 or 48 h. The conversion and yield were calculated using the internal standard calculation method using the solvent as a standard (for detailed procedures see the Supporting Information). Synthesis of Dimethyl(phenylethynyl)vinylsilane, SiMe2(C CPh)(CHCH2) (1; Table 2). A thick-walled vacuum glass Schlenk reactor (50 mL) equipped with a magnetic stirrer was charged, under an argon atmosphere, with 1.93 g (14.4 mmol) of anhydrous lithium iodide (LiI) and 20 mL of anhydrous and deoxidized C6H5CF3. Then, to the mixture obtained were successively added 1.45 g of Si(H2C CH)Me2Cl (12 mmol), 2,48 g of NEt(i-Pr)2 (19.2 mmol), 1.71 g of PhCCH (16.8 mmol), and 34.04 mg of the complex [{Ir(μCl)(CO)2}2] (0.06 mmol) under a flow of argon. The reactor was placed in an oil bath, and the reaction was conducted at 90 °C with vigorous stirring. The reaction was carried out until complete conversion of the silicon reagent, typically 24 h. The reaction mixture was analyzed by GC and GC/MS at the beginning and after 24 h. The conversion and yield were calculated using the internal standard calculation method (the solvent pick was used as an internal standard). After completion of the reaction, in order to remove the catalyst and ammonium salt from the reaction mixture, the solvent and unreacted substrates were evaporated at a reduced pressure and then 30 mL of pentane was added. The resulting suspension was filtered off, and the resulting deposit was rinsed with two portions of pentane. The solvent was initially evaporated from the filtrate, and the residual product was distilled by means of the trap to trap technique at reduced pressure, giving 2.17 g of the final product. Dimethyl(phenylethynyl)vinylsilane was obtained in a yield of 97%. Anal. Calcd for C12H14Si: C, 77.35; H, 7.57. Found: C, 77.39; H, 7.59. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.52 (m, 2H, m-Ph); 7.33 (m, 3H, o,p-Ph); 6.26 (dd, 1H, SiCHCH2); 6.10 (dd, 1H, SiCHCH2); 5.97 (dd, 1H, =CH2); 0.37 (s, 6H, SiMe2). 13C NMR (75.46 MHz, C6D6, 300 K): δ (ppm) 136.63, 133.27, 132.13, 128.73, 128.32, 123.11 (Ph and SiCH CH2); 106.35 (CC-SiMe2); 92.09 (CCSiMe2), −1.32 (SiMe2). 29 Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −24.67. Synthesis of Methylphenyl(phenylethynyl)vinylsilane, SiMePh(CCPh)(CHCH2) (2; Table 2). Following the procedure used for preparation of compound 1 (Table 2), a reaction was carried out with 1.93 g (14.4 mmol) of LiI, 2.19 g (12 mmol) of Si(H2C CH)(Me)(Ph)Cl, 1.71 g (16.8 mmol) of PhCCH, and 2.48 g (19.2 mmol) of NEt(i-Pr)2 in the presence of 34.04 mg (0.06 mmol) of the complex [{Ir(μ-Cl)(CO)2}2]. A 2.86 g amount of methylphenyl(phenylethynyl)vinylsilane was obtained (yield 96%). Anal. Calcd for C17H16Si;: C, 82.20; H, 6.49. Found: C, 82.30; H, 6.53. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.76 (m, 2H, m-Ph); 7.58 (m, 2H, mPh); 7.46 (m, 3H, o,p-Ph); 7.37 (m, 3H, o,p-Ph); 6.38 (dd, 1H, SiCHCH2); 6.22 (dd, 1H, SiCHCH2); 6.06 (dd, 1H, CH2); 0.63 (s, 3H, SiCH3). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 135.14, 134.83, 134.76, 134.24, 132.08, 129.62, 128.80, 128.21, 127.92, 122.78 (Ph and SiCHCH2), 107.84 (SiCC), 89.99 ( SiCC), −2.54 (SiMe). Synthesis of Diphenyl(phenylethynyl)vinylsilane, SiPh2(C CPh)(CHCH2) (3; Table 2). Following the procedure used for preparation of compound 1 (Table 2), a reaction was carried out with 1.93 g (14.4 mmol) of LiI, 2.94 g (12 mmol) of Si(H2CCH)Ph2Cl, 1.71 g (16.8 mmol) of PhCCH, and 2.48 g (19.2 mmol) of NEt(iPr)2 in the presence of 34.04 mg (0.06 mmol) of the complex [{Ir(μCl)(CO)2}2]. A 3.65 g amount of diphenyl(phenylethynyl)vinylsilane was obtained (yield 98%). Anal. Calcd for C22H18Si: C, 85.11; H, 5.84. Found: C, 85.14; H, 5.86. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.82 (m, 4H, m-Ph); 7.66 (m, 2H, m-Ph); 7.51 (m, 6H, o,pPh); 7.43 (m, 3H, o,p-Ph); 6.66 (dd, 1H, SiCHCH2); 6.40 (dd, 1H, SiCHCH2); 6.15 (dd, 1H, CH2). 13C NMR (74.46 MHz, C6D6, G
dx.doi.org/10.1021/om500320t | Organometallics XXXX, XXX, XXX−XXX
Organometallics
Article
Tetrahedron Lett. 2001, 42, 4353. (f) Tykwinski, R. R. Angew. Chem., Int. Ed. 2003, 42, 1566. (g) Negishi, E.; Anastasia, L. Chem. Rev. 2003, 103, 1979. (2) (a) Brizius, G.; Bunz, U. H. F. Org. Lett. 2002, 4, 2829−2831. (b) Yamamoto, Y. Chem. Rev. 2008, 108, 3199−3222. (c) Tour, J. Acc. Chem. Res. 2000, 33, 791−804. (d) Carrolland, R. L.; Gorman, Ch. B. Angew. Chem., Int. Ed. 2002, 41, 4378−4400. (e) Nishihara, Y.; Ando, J.; Kato, T.; Mori, A. Macromolecules 2000, 33, 2779−2781. (f) Martinand, R. E.; Diederich, F. Angew. Chem., Int. Ed. 1999, 38, 1350−1377. (g) Castanet, A.-S.; Colobert, F.; Schlama, T. Org. Lett. 2000, 2, 3559−3561. (h) Blumrnkopf, T. A.; Overman, L. E. Chem. Rev. 1986, 86, 857−873. (3) (a) Weber, W. P. Silicon Reagents for Organic Synthesis; SpringerVerlag: Berlin, 1983; pp 129−158. (b) Goettmann, F.; Boissiere, C.; Grosso, D.; Mercier, F.; Floch, P. L.; Sanchez, C. Chem. Eur. J. 2005, 11, 7416−7426. (c) Nishihara, Y.; Saito, D.; Tanemura, K.; Noyori, S.; Takagi, K. Org. Lett. 2009, 11, 3546−3549. (d) Kral, K.; Hapke, M. Tetrahedron Lett. 2012, 53, 2856−2859. (e) Motokura, K.; Matsunaga, S.; Miyaji, A.; Baba, T.; Yashima, T. Tetrahedron Lett. 2011, 52, 6687− 6692. (f) Nadres, E. T.; Lazareva, A.; Daugulis, O. J. Org. Chem. 2011, 76, 471−483. (g) Hoffmann, F.; Wagler, J.; Roewer, G. Eur. J. Inorg. Chem. 2010, 1133−1142. (h) Mazeas, D.; Skrydstrup, T.; Doumeix, O.; Beau, J.-M. Angew. Chem. 1994, 106, 1457−1459. (i) Skrydstrup, T.; Mazeas, D.; Elmouchir, M.; Doisneau, G.; Riche, C. Chem. Eur. J. 1997, 3, 1342−1356. (j) Komarov, N. V.; Yarosh, O. G.; Ivanova, Z. G. Izv. Akad. Nauk SSSR, Ser. Khim. 1972, 3, 698−699. (4) (a) Volnov, I.; Reutt, A. Zh. Obshch. Khim. 1940, 10, 1600−1604. (b) Lettan, R. B.; Scheidt, K. A. Org. Lett. 2005, 7, 3227−3230. (5) (a) Jun, C.-H.; Crabtree, R. H. J. Organomet. Chem. 1993, 447, 177−187. (b) Batail, N.; Djakovitch, L.; Bendjeriou, A.; Dufaud, V.; Lomberget, T. R. Adv. Synth. Catal. 2009, 351, 2055−2062. (6) (a) Anreev, A. A.; Konshin, V. V.; Komarov, N. V.; Rubin, M.; Brouwer, C.; Gevorgyan, V. Org. Lett. 2004, 6, 421−424. (b) Jiang, H.; Zhu, S. Tetrahedron Lett. 2005, 46, 517−519. (c) Sugita, H.; Hatanaka, Y.; Hiyama, T. Pat. Appl. JP08092257A, 1996. (d) Sugita, H.; Hatanaka, Y.; Hiyama, T. Tetrahedron Lett. 1995, 36, 2769−2772. (e) Rahaim, R. J., Jr.; Shaw, J. T. J. Org. Chem. 2008, 73, 2912−2915. (f) Andreev, A. A.; Konshin, V. V.; Komarov, N. V.; Rubin, M.; Brouwer, Ch.; Gevorgyan, V. Org. Lett. 2004, 6, 421−424. (7) (a) Shimizu, R.; Fuchikami, T. Tetrahedron Lett. 2000, 41, 907− 910. (b) Kunai, A.; Ohnishi, O.; Sakurai, T.; Ishikawa, M. Chem. Lett. 1995, 11, 1051−1052. (c) Esteruelas, M. A.; Olivan, M.; Oro, L. A.; Tolosa, J. I. J. Organomet. Chem. 1995, 487, 143−150. (8) Ding, N.; Zhang, W.; Hor, T. S. A. Dalton Trans. 2012, 41, 5988− 5994. (9) Marques-Gonzalez, S.; Yufit, D. S.; Howard, J. A. K.; Low, P. J.; Martin, S.; Cea, P.; Osorio, H. M.; Garcia-Suarez, V. M.; Nichols, R. J.; Higgins, S. J. Dalton Trans. 2013, 42, 338−341. (10) (a) Nishihara, Y.; Ikegashira, K.; Hirabayashi, K.; Ando, J.; Mori, A.; Hiyama, T. J. Org. Chem. 2000, 65, 1780−1787. (b) Setayesh, S.; Grimsdale, A. C.; Weil, T.; Enkelmann, V.; Muellen, K.; Meghdadi, F.; List, E. J. W.; Leising, G. J. Am. Chem. Soc. 2001, 123, 946−953. (11) (a) Bolourtchian, M.; Zadmard, R.; Saidi, M. R. Monatsh. Chem. 1999, 130, 333−336. (b) Li, D.; Tanaka, T.; Ohmiya, H.; Sawamura, M. Org. Lett. 2010, 12, 3344−3347. (c) Cooper, M. A.; Lucas, M. A.; Taylor, J. M.; Ward, A. D.; Williamson, N. M. Synthesis 2001, 4, 621− 625. (12) (a) Lu, P.; Lam, J. W. Y.; Liu, J.; Jim, C. K. W.; Yuan, W.; Chan, C. Y. K.; Xie, N.; Hu, Q.; Tang, B. Z.; Cheuk, K. K. L. Macromolecules 2011, 44, 5977−5986. (b) Neenan, T. X.; Whitesides, G. M. J. Org. Chem. 1988, 53, 2489−2496. (c) Gelman, D.; Tsvelikhovsky, D.; Molander, G. A.; Blum, J. J. Org. Chem. 2002, 67, 6287−6290. (d) Arcadi, A.; Cacchi, S.; Marinelli, F. Tetrahedron Lett. 1986, 27, 6397−6400. (e) Erdelyi, M.; Gogoll, A. J. Org. Chem. 2001, 66, 4165− 4169. (f) Zhou, N.; Wang, L.; Thompson, D. W.; Zhao, Y. Tetrahedron 2011, 67, 125−143. (g) Hill, L. L.; Smith, J. M.; Brown, W. S.; Moore, L. R.; Guevera, P.; Pair, E. S.; Porter, J.; Chou, J.; Wolterman, C. J.; Craciun, R.; Dixon, D. A.; Shaughnessy, K. H. Tetrahedron 2008, 64, 6920−6934. (h) Fudickar, W.; Linker, T. Chem. Eur. J. 2011, 17,
preparation of compound 1, a reaction was carried out with 1.93 g (14.4 mmol) of LiI, 0.85 g (6 mmol) of Si(Me)(H2CCH)Cl2, 1.71 g (16.8 mmol) of PhCCH, and 2.48 g (19.2 mmol) of NEt(i-Pr)2 in the presence of 34.04 mg (0.06 mmol) of the complex [{Ir(μCl)(CO)2}2]. A 1.57 g amount of methylbis(phenylethynyl)vinylsilane was obtained (yield 96%). Anal. Calcd for C19H16Si: C, 83.77; H, 5.92. Found: C, 83.83; H, 5.97. 1H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.53 (m, 4H, m-Ph); 7.33 (m, 6H, o,p-Ph); 6.21 (m, 3H, SiCHCH2); 0.55 (s, 3H, Si(CH3)). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 135.30, 133.69, 132.35, 129.13, 128.37, 122.71, (Ph and SiCHCH2), 107.10 (SiCC), 88.90 (SiCC), −0.55 (Si(CH3)). 29Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −46.30. Synthesis of Methyl[bis{(4-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)phenyl)ethynyl)]vinylsilane, SiMe[CCC 6 H 4 B(OCMe2CMe2O)]2(CHCH2) (11; Table 3). Following the procedure used for preparation of compound 1, a reaction was carried out in 10 mL of C6H5CF3 with 0.96 g (7.2 mmol) of LiI, 0.42 g (3 mmol) of Si(Me)(H2CCH)Cl2, 1.41 g (6.18 mmol) of (OCMe2CMe2O)BC6H4CCH, and 1.24 g (9.6 mmol) of NEt(i-Pr)2 in the presence of 17.02 mg (0.03 mmol) of the complex [{Ir(μ-Cl)(CO)2}2]. The residual product was purified by a flash column filled with silica. After purification 1.38 g of methyl[bis{4-(4,4,5,5-tetramethyl-1,3,2-dioxoboran-2-yl)phenylethynyl)]vinylsilane was obtained (yield 88%). Anal. Calcd for C31H38B2O4Si: C, 71.01; H, 7.31. Found: C, 71.10; H, 7.36. 1 H NMR (300 MHz, CDCl3, 300 K): δ (ppm) 7.75 (d, 3JH−H = 8.1 Hz, 4H, C6H4); 7.52 (d, 3JH−H = 8.1 Hz, 4H, C6H4); 6.19 (m, 3H, CHCH2); 1.34 (s, 24H, Me); 0.55 (s, 3H, SiMe). 13C NMR (74.46 MHz, C6D6, 300 K): δ (ppm) 133.43; 134.59; 133.51; 129.18; 125.26 (C6H4, CHCH2); 107.17 (CCSiMe3); 90.16 (C CSiMe3); 84.14 -OC(Me)2); 25.03 (Me); −0.63 (SiMe). 29Si NMR (119.23 MHz, C6D6, 300 K): δ (ppm) −46.24. Stoichiometric Reaction of [Ir(cod)(PCy3)(CCPh)] (IVa) with Me3SiI. An 85 mg amount (0.125 mmol) of [Ir(cod)(PCy3)(C CPh)] (IVa) and 0.6 mL of benzene-d6 were placed in a J. Young NMR tube under an argon atmosphere, and 1H, 13C, and 31P NMR spectra were recorded. After NMR analysis, 25 mg (0.125 mmol) of Me3Si−I was added to the solution of IVa and the reaction was conducted for 24 h at room temperature. After this time 1H, 13C, and 31 P NMR spectra were also recorded, and then the reaction was carried out for 24 h at 50 °C. After NMR analysis, an additional 2 equiv of Me3Si−I was introduced into the NMR tube and the reaction was continued for the next 48 h.
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ASSOCIATED CONTENT
S Supporting Information *
Text and figures giving experimental procedures and NMR data of synthesized compounds. This material is available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Authors
*E-mail for I.K.:
[email protected]. *E-mail for B.M.:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was financially supported by the National Science Centre (Grant No. N N 204 443840). REFERENCES
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dx.doi.org/10.1021/om500320t | Organometallics XXXX, XXX, XXX−XXX
Organometallics
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dx.doi.org/10.1021/om500320t | Organometallics XXXX, XXX, XXX−XXX
