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Feb 13, 2013 - Chiral Palladacycles with N-Heterocyclic Carbene Ligands as Catalysts for Asymmetric Hydrophosphination. Sara Sabater, Jose A. Mata*, a...
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Chiral Palladacycles with N‑Heterocyclic Carbene Ligands as Catalysts for Asymmetric Hydrophosphination Sara Sabater, Jose A. Mata,* and Eduardo Peris †

Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castellón, Spain S Supporting Information *

ABSTRACT: Design of chiral palladacycles with N-heterocyclic carbene (NHC) ligands has been carried out in good yields starting form commercially available enantiopure benzylamines. The methodology developed consists of the formation of palladium dimers with orthometalated benzylamines. The dimers undergo facile chloride-bridge-splitting with azolium salts under basic conditions to afford the chiral palladacycles with NHC ligands and tertiary or even the more challenging primary amines. The steric and electronic properties of the resulting complexes have been modulated both by using different chelating amines and varying the topology of the NHC ligand. The new complexes have been fully characterized by means of NMR, ESI/MS, and Xray crystallography. All new complexes complexes have been used as catalysts in the 1,4-addition of diarylphosphines to α,βunsaturated ketones.

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INTRODUCTION Optically active cyclopalladated derivatives containing N-donor ligands have been extensively studied due to their applications in many areas, including organic synthesis, homogeneous catalysis, and medicinal chemistry.1 Some of the special properties of the [C,N] palladacycles have been attributed to the labile Pd−C bond, which permits intriguing insertion reactions with small molecules, facilitating the formation of various nitrogen containing heterocycles and carbocycles.2 Palladacycles containing N-heterocyclic carbene ligands (NHCs) have been less studied,3 but they have already demonstrated improved catalytic performances in catalytic reactions such as the Suzuki−Miyaura,3j Buchwald−Hartwig,3e Heck,3e,g enolate arylation,3f haloarenene dehalogenation,3a and olefin polymerization,3i even at very mild reaction conditions. It has been argued that the further exploration of the catalytic potential of NHC ligated palladacycles for palladium mediated transformations have been hampered by the lack of general methods for their synthesis, therefore some recent efforts have been done for developing a practical and general synthetic protocol for preparing families of NHC-palladacycles.3c Palladacycles introduce an easy and often effective way of introducing chirality for the formation of enantiopure complexes that can be applied in asymmetric catalysis.1b,c © 2013 American Chemical Society

While chiral NHC-containing [C,P] cyclopalladates have been described and show promising results in their application in asymmetric catalysis,3h we are unaware of the preparation of similar types of complexes based on [N,C] systems. Among cyclopalladated amines, primary amines constitute a challenging type of ligands because it is generally accepted that they are inert toward cyclometalation reactions, although they can undergo cyclopalladation under certain reaction conditions.1c On the basis of our experience in the preparation of NHC palladium complexes and their application in homogeneous catalysis,4 we now describe the systematic preparation of a series of enantiomerically pure NHC-containing palladacycles with orthometalated benzylamines. The new complexes have been tested in the asymmetric hydrophosphination of olefins, a reaction that provides direct and atom-efficient access to chiral phosphines.5 Specifically, we have studied the hydrophosphination of trans-chalcone with Ph2PH to afford the corresponding keto-substituted C*-chiral tertiaryphosphine. Received: January 7, 2013 Published: February 13, 2013 1112

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RESULTS AND DISCUSSION Orthometalated chiral N,N-dimethylbenzylaminate palladacycles 4−6 (Scheme 1) are conveniently obtained in high

in solution. Previous studies carried out with tertiary amines have demonstrated that the syn isomer interconvert to the anti in solution at room temperature.12 The molecular structures of compounds 9 and 11 were confirmed by means of X-ray diffractometry. Figure 1 shows the

Scheme 1

yields (85−95%) from commercially available chiral tertiary amines 1−3 using palladium dichloride and potassium carbonate. The same complexes have already been described starting from lithiumtetrachloropalladate.6 The 1H and 13C NMR spectra are in accordance with the published results and show cis/trans isomerism, which has already been studied in detail.7 Under similar reaction conditions, the reaction with primary amines yields monomeric diamine complexes (Scheme 2). In

Figure 1. Molecular diagram of complex 9. Ellipsoids at 50% probability level. Selected bond lengths [Å] and angles [deg]: Pd(1)−Cl(3) 2.3072(8), Pd(1)−Cl(2) 2.2946(8), Pd(1)−N(4) 2.064(2), Pd(1)−N(5) 2.061(3), Cl(2)−Pd(1)−Cl(3) 178.45(3), N(4)−Pd(1)−N(5) 179.47(12), Cl(2)−Pd(1)−N(4) 91.29(8), Cl(2)−Pd(1)−N(5) 88.18(8), Cl(3)−Pd(1)−N(4) 89.50(7), Cl(3)−Pd(1)−N(5) 91.03(8).

Scheme 2

molecular structure of 9 with the selected bond lengths and angles. The molecular structure of 9 consists of a palladium center with two chlorides and two (S)-[1-(1-naphthyl)ethyl]amine 8 ligands in a trans disposition. The average Pd−Cl distance is 2.30 Å, slightly longer than the average Pd−NH2 distance, 2.06 Å. The two primary amines are in a syn disposition in the solid state due to packing effects and a short Pd−Pd interaction with another molecule of 3.225 Å. The molecular structure of compound 11 was confirmed by means of X-ray diffractometry. Figure 2 shows the molecular structure of the complex and the selected bond lengths and angles. At this point, it is interesting to point out that despite acetate-bridged binuclear cyclopalladate complexes with primary amines are well-known, only three X-ray examples have been described to date.9b,13,14 The molecular structure of 11 consists of two palladium centers with two cis-bridging acetate groups and two cyclometalated (S)-[1-(1-naphthyl)ethyl]amines. The C−N orthometalated amine forms a fivemembered ring in a puckered conformation, where the N atom is out of the plane by 0.48 Å. The methyl group attached at the benzylic carbon adopts an axial disposition enforced by the naphthyl group as previously described for this ligand in a related palladium complex.7b For this type of acetate bridge dimers, a maximum of three isomers may be formed.12b In our case, only the antiexo isomer was observed. The folded structure of the acetate bridge brings the palladium atoms into a relatively short Pd−Pd distance of 2.92 Å. The reaction of the imidazolium salts (12−14) with the chiral N,N-dimethylbenzylaminate palladacycles 4 and 6 in acetonitrile in the presence of Cs2CO3 and an excess of KI affords the corresponding NHC-based palladacyles (15−20) of general formula [(NHC)(I)Pd(C-NMe2)] (Scheme 3). All these complexes were obtained as pale-yellow crystalline solids after recrystallization from dichloromethane/hexanes mixtures in yields ranging from 50% to 90%. In all cases, the NHC and

our case, the reaction of the primary amine (S)-[1-(1naphthyl)ethyl]amine (8) with palladium dichloride in the presence of potassium carbonate afforded the palladium diamine dichloride 9. Orthometalated chiral palladium complexes with primary amines were obtained following the methodology described by Vicente et al.1b,8 The reaction of the primary amines 7 and 8 with palladium acetate in toluene afforded the orthometalated complexes 109 and 11 in good yields. In an early work, Granell and co-workers cyclometalated the same amine using the same protocol, but further addition of LiCl allowed them to isolate the chloride-bridged dimer instead of the acetate.10 The 1H NMR of complex 11 shows broad signals for the NH2 and CH groups, indicating a dynamic behavior in solution, as observed for other acetate bridged palladium complexes.9a,11 The presence of only one singlet for the methyl of both acetates (2.17 ppm, CH3) in the proton spectrum and the presence of one set of two signals for carbons of the acetate group in the carbon NMR (181.4 and 24.6 ppm CH3COO−) are indicative that only the anti isomer is present 1113

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amount of signals, compared to the spectra shown by 15. The H NMR spectrum of 16 shows two signals for the methyl group (4.07 and 3.98 ppm) of the azole ring. The two methyl groups of the N,N-dimethylbenzylamine appear as four different singlets at 2.97, 2.98, 2.87, and 2.84 ppm, respectively. The methyl group at the chiral carbon appear as two doublets at 1.61 ppm (3JH−H = 6.5 Hz) and 1.56 ppm (3JH−H = 6.5 Hz). The 13C NMR spectrum of 16 displays the representative signals due to the Pd−Ccarbene of the two isomers at 170.0 and 169.5 ppm. The properties and characterization of complexes with asymmetrically NHC ligands (17, 19, and 20) are similar to complex 16. In the case of complex 20, the two rotamers could be separated by column chromatography on silica gel using a mixture of CH2Cl2/EtOAc (9:1). The pure complexes 20A and 20B were characterized by 1H NMR spectroscopy. Unfortunately, epimerization of both complexes was observed, rendering a 1:1 mixture of both atropisomers in solution.15 1

Chart 1

Figure 2. Molecular diagram of complex 11. Ellipsoids at 50% probability level. Selected bond lengths [Å] and angles [deg]: Pd(1)− Pd(2) 2.9159(5), Pd(1)−O(31) 2.166(3), Pd(1)−O(35) 2.049(3), Pd(1)−N(3) 2.026(4), Pd(1)−C(4) 1.962(5), Pd(2)−O(29) 2.072(3), Pd(2)−O(33) 2.165(4), Pd(2)−N(16) 2.036(4), Pd(2)− C(17) 1.957(5), O(35)−Pd(1)−O(31) 88.77(14), O(29)−Pd(2)− O(33) 87.98(14), C(4)−Pd(1)−N(3) 81.48(19), C(17)−Pd(2)− N(16) 81.0(2).

the N,N-dimethylamino ligands are mutually trans and the reaction proceeds with retention of configuration. Complexes 15−20 were fully characterized by NMR spectroscopy and mass spectrommetry. The 1H NMR spectrum of 15 shows two distinct signals for the methyl groups (3.93 and 3.83 ppm) of the azole ring, indicating the loss of the 2-fold symmetry of the ligand upon coordination to the metal. Evidence of metal coordination is the absence of the characteristic signal for the acidic NCHN proton at δ 9.54. The two methyl groups of the N,Ndimethylbenzylamine appear as two different singlets at 2.92 and 2.85 ppm, respectively. The methyl group at the chiral carbon appears as a doublet at 1.63 ppm (3JH−H = 6.5 Hz). The 13 C NMR spectrum of 15 displays the representative signal due to the Pd−Ccarbene at 173.4 ppm. The 1H NMR spectrum of 16 shows two distinct set of signals corresponding to the two Pd−NHC atropisomers in a 55/45 ratio, as a consequence of hindered rotation about the Pd−Ccarbene bond. Therefore, the NMR spectra display a double

The molecular structure of compound 15 was confirmed by means of X-ray diffractometry. Figure 3 shows the molecular structure of the two conformational isomers found in the solid state. The structure consists of a palladium center with an iodide, a NHC ligand, and a chelated (S)-N,N-dimethylbenzylamine 1. The C−N orthometalated amine forms a fivemembered ring that adopts a puckered conformation. The methyl group attached at the benzylic carbon can adopt an axial or equatorial disposition, and both of them are observed in the crystal structure (Figure 3). In solution, the interconversion between the two isomers is very fast, even at low temperatures.8a,13a,16 This situation clearly differs from that shown by complex 11 for which the equatorial disposition is not affordable for the naphthyl group (Figure 2).7b

Scheme 3

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NMR spectrum of 21 shows the characteristic signals for the azole ring 12, indicating the 2-fold symmetry of the ligand. Evidence of metal coordination is the absence of the characteristic signal for the acidic NCHN proton at δ 9.95. The signal due to the protons of the methyl group at the chiral carbon appears as a doublet at 1.99 ppm (3JH−H = 6.8 Hz). The 13 C NMR spectrum of 21 displays the representative signal due to the Pd−Ccarbene at 148.9 ppm. The 1H NMR spectrum of 24 shows two distinct set of signals corresponding to the two diastereomers in a 65/35 ratio. The 1H NMR spectrum shows two signals for the methyl group (4.03 and 3.85 ppm) of the azole ring and two overlap doublets of the methyl group at the chiral carbon between 1.97−1.86 ppm. The 13C NMR spectrum displays the representative signal due to the Pd−Ccarbene at 174.8 and 174.4 ppm, each corresponding to either isomer. The molecular structures of compounds 21 and 23 were confirmed by means of X-ray diffractometry (Figures 4 and 5).

Figure 3. Molecular diagram of complex 15 showing the two conformational isomers. Ellipsoids at 50% probability level. Hydrogens omitted for clarity except at the benzylic position. Selected bond lengths [Å] and angles [deg] for the equatorial isomer (left): Pd(1)− C(3) 1.979(5), Pd(1)−I(2) 2.7195(5), Pd(1)−C(10) 2.166(3), Pd(1)−N(13) 2.160(4), N(13)−Pd(1)−I(2) 97.71(11), N(13)− Pd(1)−C(10) 82.21(17), C(3)−Pd(1)−I(2) 90.52(14), C(10)− C(11)−C(12)−C(16) 160.3. Selected bond lengths [Å] and angles [deg] for the axial isomer (right): Pd(21)−C(23) 1.961(5), Pd(21)− I(22) 2.6948(6), Pd(21)−C(30) 2.000(5), Pd(21)−N(33) 2.145(5), N(33)−Pd(21)−I(22) 98.35(13), N(33)−Pd(21)−C(30) 82.19(19), C(23)−Pd(21)−I(22) 88.91(14), C(30)−C(31)−C(32)−C(36) 91.3.

Figure 4. Molecular diagram of complex 21. Ellipsoids at 50% probability level. Selected bond lengths [Å] and angles [deg]: Pd(1)− C(4) 1.968(6), Pd(1)−N(11) 2.125(4), Pd(1)−I(2) 2.5984(8), Pd(1)−I(3) 2.6024(8), C(4)−Pd(1)−I(2) 87.87(19), C(4)−Pd(1)− I(3) 90.3(2), N(11)−Pd(1)−I(2) 89.77(14), N(11)−Pd(1)−I(3) 92.05(14).

The synthesis of NHC palladacycles with primary amines is not as straightforward as the synthesis of NHC palladacycles with tertiary amines. If the reaction conditions depicted in Scheme 3 are used with the chiral primary amines decomposition products are observed. For this reason, an alternative procedure was developed as described in Scheme 4. The reaction of the imidazolium salts (12 and 14) with the chiral primary amine 8 in acetonitrile in the presence of Cs2CO3 and an excess of KI affords the NHC−palladium− amine complexes 21 and 22 in good yields. The reaction of these complexes with silver acetate facilitates the orthometalation of the amine, affording complexes 23 and 24. The 1H

The structure of 21 consists of a palladium center with a two iodide ligands in a trans disposition a NHC ligand and a nitrogen coordinated primary amine. The structure of 23 has a C−N cyclopalladated primary amine. The C−N orthometalated amine forms a five-membered ring with the methyl group attached at the chiral carbon in an axial disposition. The chiral palladacycles were tested as catalysts in the hydrophosphination reaction by using diphenylphosphine and 1,3-diphenyl-2(E)-propen-1-one (trans-chalcone) as model substrates. We decided to study this reaction because successful enantioselective preparation of chiral organophosphorous compounds via metal-catalyzed asymmetric addition of H−P

Scheme 4

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palladacycles 18, 19, and 23 afforded modest enantioselectivities (Table 1, entries 2−8). The best results were obtained for catalyst 20 (Table 1, entry 4), which contains the NHC ligand with the bulkier 9-methylantracyl group and a chelating N,Ndimethylnaphthylbenzylamine. This result compares well with previously published results by Leung and co-workers in which a bis-acetonitrile palladium(II) complex with the same cyclometalated amine is used, although in their case catalyst loadings of 5 mol % and temperatures of −40 °C were found to be optimum17d (the same group recently achieved much better ee values when using a chiral phosphapalladacycles19). In our case, the ee value decreased from 56% to 14% when lowering the temperature form 25 to −30 °C (Table 1, entries 4−5). Although we do not have a reasonable explanation for this behavior, there are some relevant examples in the literature in which the same effect is observed.20 In our case, at low temperatures where the catalyst may have not been activated, the noncatalytic hydrophosphination could be non-negligible, therefore favoring the formation of the racemic species. Some other authors have attributed this abnormal effect of the temperature on the enantioselectivity to the formation of dimerization of the precatalyst at low temperatures.21 The solvent had little influence on the product yield and ee values found (Table 1, entries 6−8).

Figure 5. Molecular diagram of complex 23. Ellipsoids at 50% probability level. Selected bond lengths [Å] and angles [deg]: Pd(1)− C(3) 1.975(7), Pd(1)−N(10) 2.095(5), Pd(1)−I(2) 2.6768(7), Pd(1)−C(14) 1.993(6), C(3)−Pd(1)−I(2) 93.30(19), C(14)− Pd(1)−C(3) 92.0(3), N(10)−Pd(1)−I(2) 93.85(15), N(10)− Pd(1)−C(14) 81.1(2).

bonds has recently attracted great interest.17 Also, the stereocontrolled addition of a P−H bond to a C−C bond is one of the most efficient and “green” ways to provide direct access to chiral phosphines. Only very few examples have been reported on the use of [N,C] palladacycles in this reaction.17b,d,18 NHC-based palladium complexes have never been used in this reaction. The reactions were performed at room temperature using a catalyst loading of 2 mol %. For the activation of the catalyst, a catalytic amount of base (5 mol % of K2CO3) was used. The products were isolated by column chromatography as phosphine oxides after being treated with H2O2.17h All the catalysts showed high activity in terms of conversion and yields obtained under mild reaction conditions (Table 1). The

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CONCLUSIONS Novel chiral palladacycles with N-heterocyclic carbene ligands have been synthesized and fully characterized starting from commercially available enantiopure benzylamines. The synthesis of NHC palladacycles with tertiary amines is straightforward, and a two-step procedure has been developed for obtaining NHC palladacycles with primary amines. The steric and electronic properties of the resulting complexes have been modulated both by using different chelating amines and varying the topology of the NHC ligand. The complexes with asymmetrical NHC ligands show the presence of two atropisomers that have been isolated using column chromatography and characterized by 1H NMR. Epimerization of the isolated complexes slowly occurs in solution. The new complexes have been used as catalysts in the 1,4-addition of diarylphosphines to α,β-unsaturated ketones. All the catalysts showed high activity in terms of conversion and yields obtained under mild reaction conditions. The hydrophosphination reaction proceeds with excellent regioselectivity (phosphorus addition occurs at the 3 carbon position) although modest enantioselectivities.

Table 1. Selected Data for the Chalcone Hydrophosphinationa

entry

catalyst

solvent

temp (°C)

yield (%)b

ee (%)c

1 2 3 4 5 6 7 8

11 18 19 20 20 20 20 23

CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 toluene THF CH2Cl2

25 25 25 25 −30 25 25 25

77 80 51 91 90 85 57 66

0 35 9 56 14 32 55 25

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EXPERIMENTAL SECTION

All manipulations were carried out under aerobic conditions unless otherwise stated. Compound 10 and imidazolium salts 12−14 were prepared according to literature procedures.9a,22 Anhydrous solvents were dried using a solvent purification system (SPS M BRAUN) or purchased from Aldrich and degassed prior to use by purging with dry nitrogen and kept over molecular sieves. All other reagents were used as received from commercial suppliers. High performance liquid chromatography (HPLC) analyses were carried out in a Merck HITACHI LaChrom chromatograph UV detector at 250 nm using a using a Daicel CHIRALPACK IC column (25 cm × 4.6 mm I.D.). NMR spectra were recorded on Varian Innova spectrometers operating at 300 or 500 MHz (1H NMR) and 75 and 125 MHz (13C NMR), respectively, using CDCl3 as solvent at room temperature unless otherwise stated. Elemental analyses were carried out in an EA 1108 CHNS-O Carlo Erba analyzer. Electrospray mass spectra (ESIMS) were recorded on a Micromass Quatro LC instrument, and

a

Reactions were carried out with 0.5 mmol of trans-chalcone, HPPh2 (0.6 mmol), 2 mL of solvent for 10 h. bIsolated yields after column chromatography. cDetermined using HPLC.

reaction is sensitive to the presence of oxygen due to the oxidation of diphenylphosphine. The reaction proceeds from moderate to good yields even at low temperatures (25 °C or lower). The hydrophosphination reaction proceeds with excellent regioselectivity (phosphorus addition occurs at the 3 carbon position). The chiral palladacycle 11 did not afford any enantiomeric excess (Table 1, entry1), while the NHC1116

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nitrogen was employed as drying and nebulizing gas. Melting points were determined using a Bibby Stuart apparatus (SMP10). X-ray Studies. Diffraction data was collected on a Agilent SuperNova diffractometer equipped with an Atlas CCD detector using Mo Kα radiation (λ = 0.71073 Å). Single crystals were mounted on a MicroMount polymer tip (MiteGen) in a random orientation. Absorption corrections based on the multiscan method were applied.23 The structures were solved by direct methods in SHELXS-97 and refined by the full-matrix method based on F2 with the program SHELXL-97 using the OLEX software package.24 General Procedure for the Synthesis of Chiral Palladacycles with Tertiary Amines. Complexes 4−6 have been described previously starting from lithium tetrachloropalladate.6 In a pyrex tube, 0.56 mmol of finely powered PdCl2 and 0.59 mmol of the corresponding tertiary amine were suspended in acetonitrile. The suspension was heated at 80° until an orange solution was formed. Then, 1.4 mmol of K2CO3 was added and the reaction was continued at 80° until a yellow solution was formed. The mixture was filtered over Celite, and the solvent was concentrated under reduced pressure. The crude was redisolved in dichloromethane and washed with a saturated NaCl solution (3 × 10 mL). The organic phase was dried with anhydrous MgSO4. Crystallization from dichloromethane/ hexanes afforded the products as yellow crystalline solids. General Procedure for the Synthesis of Chiral Palladacycles with Primary Amines. In a Schlenk tube were added 0.45 mmol of finely powered Pd(OAc)2 and 0.446 mmol of corresponding amine in 10 mL of deoxygenated toluene, and the suspension was heated at 50° for 15 h. The solvent was removed under reduced pressure. Recrystallization from dichloromethane/hexanes afforded the products as pale-yellow crystalline solids. Compound 11. Yield: 257 mg (85%). 1H NMR (500 MHz, CDCl3): δ 7.73 (d, 3JH,H = 7.9 Hz, 1H), 7.39 (d, 3JH,H = 8.1 Hz, 1H), 7.34−7.23 (m, 3JH,H = 18.8, 6.6 Hz, 3H), 6.96 (d, 3JH,H = 8.1 Hz, 1H), 4.36 (broad s, 1H, CHCH3), 3.61 (broad s, 1H, NH), 3.21−3.09 (m, 1H, NH), 2.17 (s, 3H, CH3COO), 1.74−1.65 (m, 3H, CHCH3). 13 C{1H} NMR (126 MHz, CDCl3): δ 181.4 (CH3COO), 149.3, 141.3, 131.6, 129.6, 128.8, 127.8, 125.9, 125.6, 123.9, 123.2, 58.3 (CHCH3), 24.6 (CHCH3, CH3COO). Anal. Calcd for C28H30N2Pd2O4 (671.39): C, 50.09; H, 4.50; N, 4.17. Found: C, 50.06; H, 4.75; N, 4.47. Electrospray MS (Cone 15 V) (m/z, fragment): 358.1 [Pd(L)(MeCN)2]+. HRMS ESI-TOF-MS (positive mode): [Pd(L) + MeCN]+ monoisotopic peak 317.0275; calcd 317.0276, εr 0.3 ppm. General Procedure for the Sythesis of Chiral Palladacycles Bearing Tertiary Amines with NHC Ligands. In a pyrex tube 0.15 mmol of chiral palladacycle, 0.30 mmol of imidazolium salt, 0.3 mmol of KI and 0.43 mmol of Cs2CO3 were heated at 100° and stirred for 1h. The resulting mixture was filtered over Celite and the solvent was removed under reduced pressure. The crude was redisolved in dichloromethane and washed with a saturated NaCl solution (3 × 10 mL). The organic phase was dried with anhydrous MgSO4. Crystallization from dichloromethane/hexanes afforded the products as pale yellow crystalline solids. Compound 15. Yield: 128 mg (90%) 1H NMR (300 MHz, CDCl3): δ 7.02−6.90 (m, 4H), 6.78−6.71 (m, 1H), 5.88−5.83 (m, 1H), 3.93 (s, 3H, NimidazoleCH3), 3.83 (s, 3H, NimidazoleCH3), 3.69 (q, 3 JH,H = 6.4 Hz, 1H,CHCH3), 2.92 (s, 3H, NamineCH3), 2.85 (s, 3H, NamineCH3), 1.63 (d, 3JH,H = 6.5 Hz, 3H, CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ 173.4 (Ccarbene−Pd), 154.9, 152.5, 134.4, 125.5, 124.1, 122.9, 122.1, 74.2 (CHCH3), 51.3 (NamineCH3), 49.2 (NamineCH3), 38.7 (NimidazoleCH3), 38.5 (NimidazoleCH3), 22.6 (CHCH3). Anal. Calcd for C15H22N3PdI (477.68): C, 37.71; H, 4.64; N, 8.79. Found: C, 37.43; H, 4.96; N, 8.89. Melting point 205−208 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 350.1 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 350.0852; calcd 350.0855, εr 0.9 ppm. Compound 16. Purification by silica gel chromatography with CH2Cl2/AcOEt = 1/1 afforded the product as a yellow solid. Yield: 93 mg (60%). Isomer 1: 1H NMR (500 MHz, CDCl3): δ 7.16 (d, 3JH,H = 2.1 Hz, 1H), 7.00−6.92 (m, 3H), 6.73 (dtd, 3JH,H = 9.0, 7.4, 1.7 Hz, 1H), 5.88 (d, 3JH,H = 7.5 Hz, 1H), 3.98 (s, 3H, NimidazoleCH3), 3.83 (q,

JH,H = 6.6 Hz, 1H, CHCH3), 2.97 (s, 3H, NamineCH3), 2.87 (s, 3H, NamineCH3), 1.90 (s, 9H, C(CH3)3), 1.56 (d, 3JH,H = 6.5 Hz, 3H, CHCH3). Isomer 2: 1H NMR (500 MHz, CDCl3): δ 7.14 (d, 3JH,H = 2.1 Hz, 1H), 7.00−6.92 (m, 3H), 6.73 (dtd, 3JH,H = 9.0, 7.4, 1.7 Hz, 1H), 5.79 (d, 3JH,H = 7.5 Hz, 1H), 4.07 (s, 3H, NimidazoleCH3), 3.56 (q, 3 JH,H = 6.5 Hz, 1H, CHCH3), 2.98 (s, 3H, NamineCH3), 2.84 (s, 3H, NamineCH3), 1.84 (s, 9H, C(CH3)3), 1.61 (d, 3JH,H = 6.5 Hz, 3H, CHCH3). Assignments for isomers are arbitrary. Diastereomeric ratio: 55/45. 13 C{1H} NMR (126 MHz, CDCl3): δ [170.0, 169.5 (Ccarbene−Pd)], 154.6, 153.6, 153.3, 152.6, 134.6, 134.5, 125.4, 125.1, 123.7, 123.7, 122.7, 122.4, 121.4, 121.2, 119.3, 119.2 [74.62, 73.40 (CHCH3)], [58.30, 58.27 (C(CH3)3)], [52.02, 51.48, 50.19, 48.02 (NamineCH3)], [40.28, 40.07 (NimidazoleCH3)], [31.91, 31.86 (C(CH3)3)], [23.41, 19.71 (CHCH3)]. Anal. Calcd for C18H28N3PdI (519.76): C, 41.59; H, 5.43; N, 8.08. Found: C, 41.92; H, 5.67; N, 8.39. Melting point 198− 201 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 392.1 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 392.1330; calcd 392.1325, εr 1.3 ppm. Compound 17. Yield: 150 mg (76%). 1H NMR (500 MHz, CDCl3): δ 8.53 (d, 3JH,H = 7.9 Hz, 2H), 8.45 (d, 3JH,H = 8.8 Hz, 2H), 8.34 (d, 3JH,H = 8.8 Hz, 2H), 8.02 (t, 3JH,H = 8.4 Hz, 4H), 7.46 (dd, 3 JH,H = 17.3, 7.8 Hz, 4H), 7.42−7.37 (m, 2H), 7.35−7.30 (m, 2H), 7.12−7.03 (m, 4H), 6.86 (ddd, 3JH,H = 10.9, 9.0, 5.0 Hz, 2H), 6.74− 6.69 (m, 2H), 6.55 (dd, 3JH,H = 33.4, 13.8 Hz, 4H), 6.29−6.22 (m, 4H), 4.07 (s, 3H, NimidazoleCH3), 3.94 (s, 3H, NimidazoleCH3), 3.89 (q, 3 JH,H = 6.8 Hz, 1H, CHCH3), 3.82 (q, 3JH,H = 6.3 Hz, 1H, CHCH3), 2.97 (s, 3H, NamineCH3), 2.93 (s, 3H, NamineCH3), 2.82 (s, 3H, NamineCH3), 2.79 (s, 3H, NamineCH3), 1.72 (d, 3JH,H = 6.5 Hz, 3H, CHCH3), 1.69 (d, 3JH,H = 6.5 Hz, 3H, CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ [173.5, 173.3 (Ccarbene−Pd)], 154.9, 154.6, 148.5, 148.2, 136.2, 136.0, 131.4, 131.3, 131.2, 131.1, 129.2, 129.1, 129.0, 127.1, 125.6, 125.6, 125.4, 125.3, 124.4, 124.3, 124.0, 123.9, 122.7, 121.6, 121.5, 120.1, 120.0, [74.3, 73.9 (CHCH3)], [50.3, 50.3, 47.7, 47.6 (NamineCH3)], [45.8, 45.3 (NimidazoleCH2−)], [38.6, 38.5 (N imidazole CH 3 )], [21.9, 20.8 (CHCH 3 )]. Anal. Calcd for C19H30N3PdI (653.89): C, 53.26; H, 4.62; N, 6.42. Found: C, 56.33; H, 4.70; N, 6.83. Melting point 196−199 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 526.3 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 526.1488; calcd 526.1486, εr 0.4 ppm. Compound 18. Yield: 135 mg (85%). 1H NMR (300 MHz, CDCl3): δ 7.72 (d, 3JH,H = 8.3 Hz, 2H), 7.44−7.25 (m, 3H), 6.98 (dd, 3 JH,H = 24.2, 1.9 Hz, 2H), 6.07 (d, 3JH,H = 8.3 Hz, 1H), 4.37 (q, 3JH,H = 6.3 Hz, 1H, (CHCH3), 4.06 (s, 3H, (NimidazoleCH3), 3.79 (s, 3H, (NimidazoleCH3), 3.16 (s, 3H, (NamineCH3), 2.80 (s, 3H, (NamineCH3)), 1.85 (d, 3JH,H = 6.4 Hz, 3H, (CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ 173.5 (Ccarbene−Pd), 151.7, 149.2, 133.3, 131.3, 129.2, 128.7, 125.7, 125.1, 123.8, 123.1, 122.1, 122.1, 71.9 (CHCH3), 51.6 (N amine CH 3 ), 51.4 (N amine CH 3 ), 38.8 (N imidazole CH 3 ), 38.2 (NimidazoleCH3), 23.9 (CHCH3). Anal. Calcd for C19H24N3PdI (527.74): C, 43.24; H, 4.58; N, 7.96. Found: C, 43.37; H, 4.56; N, 8.26. Melting point 198−201 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 400.1 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 400.1006; calcd 400.1013, εr 1.7 ppm. Compound 19. Purification by silica gel chromatography with CH2Cl2 afforded the product as a yellow solid. Yield: 85 mg (50%). Isomer 1: 1H NMR (300 MHz, CDCl3) δ 7.71 (d, 3JH,H = 8.2 Hz, 2H), 7.43−7.23 (m, 3H), 7.22 (d, 3JH,H = 2.1 Hz, 1H), 6.96 (d, 3JH,H = 2.1 Hz, 1H), 6.14 (d, 3JH,H = 8.3 Hz, 1H), 4.34 (q, 3JH,H = 6.3 Hz, 1H, CHCH3), 3.89 (s, 3H, NimidazoleCH3), 3.17 (s, 3H, NamineCH3), 2.82 (s, 3H, NamineCH3), 2.00 (s, 9H, C(CH3)3), 1.78 (d, 3JH,H = 6.3 Hz, 3H, CHCH3). Isomer 2: 1H NMR (300 MHz, CDCl3) δ 7.71 (d, 3JH,H = 8.2 Hz, 2H), 7.43−7.23 (m, 3H), 7.16 (d, 3JH,H = 2.1 Hz, 1H), 7.04 (d, 3 JH,H = 2.1 Hz, 1H), 5.98 (d, 3JH,H = 8.3 Hz, 1H), 4.34 (q, 3JH,H = 6.3 Hz, 1H, CHCH3), 4.15 (s, 3H, NimidazoleCH3), 3.13 (s, 3H, NamineCH3), 2.84 (s, 3H, NamineCH3), 1.80 (s, 9H, C(CH3)3), 1.78 (d, 3JH,H = 6.3 Hz, 3H, CHCH3). Assignments for isomers are arbitrary. Diastereomeric ratio: 70/30. 13C{1H} NMR (126 MHz, CDCl3): δ [170.6, 1117

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169.5 (Ccarbene−Pd)], 152.3, 152.1, 148.7, 148.4, 134.0, 133.5, 131.3, 131.3, 129.2, 129.1, 129.0, 128.7, 128.2, 125.7, 125.6, 125.1, 125.0, 123.7, 123.6, 123.2, 121.7, 121.3, 119.6, 119.2, [71.9, 71.8 (CHCH3)], [58.4, 58.3 (C(CH3)3)], [52.6, 52.3, 51.7, 51.4 (NamineCH3)], [40.4, 39.9 (NimidazoleCH3)], [31.9, 31.8 (C(CH3)3)], [23.6, 22.8 (CHCH3)]. Anal. Calcd for C22H30N3PdI (569.82): C, 46.37; H, 5.30; N, 7.37. Found: C, 46.81; H, 5.66; N, 7.74. Melting point 230−233 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 442.3 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 442.1480; calcd 442.1483, εr 0.7 ppm. Compound 20. Yield: 148 mg (70%). 1H NMR (300 MHz, CDCl3): δ 8.63 (s, 1H), 8.58 (d, 3JH,H = 11.7 Hz, 2H), 8.49 (s, 1H), 8.24 (d, 3JH,H J = 8.6 Hz, 2H), 8.06 (d, 3JH,H = 8.9 Hz, 2H), 7.99 (d, 3 JH,H J = 8.3 Hz, 2H), 7.85−7.75 (m, 4H), 7.52−7.28 (m, 12H), 7.21 (d, 3JH,H = 7.5 Hz, 2H), 6.99 (d, 3JH,H = 15.5 Hz, 1H), 6.75 (dd, 3JH,H = 24.5, 1.9 Hz, 2H), 6.63 (d, 3JH,H = 15.2 Hz, 1H), 6.52−6.39 (m, 4H), 6.33 (dd, 3JH,H = 23.8, 2.0 Hz, 2H), 4.44 (m, 2H, CHCH3), 4.20 (s, 3H, NimidazoleCH3), 3.80 (s, 3H, NimidazoleCH3), 3.00−2.90 (m, 12H, NamineCH3), 1.98−1.91 (m, 6H, CHCH3). Diastereomeric ratio: 50/ 50. 13C{1H} NMR (75 MHz, CDCl3): δ [173.9, 173.2 (Ccarbene−Pd)], 149.5, 149.3, 147.7, 147.4, 135.3, 134.8, 131.5, 131.4, 131.2, 131.2, 131.0, 129.2, 129.2, 129.2, 129.1, 129.1, 129.0, 128.8, 127.2, 127.1, 125.7, 125.7, 125.6, 125.30, 125.2, 125.2, 125.2, 125.2, 125.1, 124.3, 124.1, 123.8, 123.7, 123.1, 123.1, 123.0, 121.7, 121.5, 120.2, 120.0, [72.1, 72.0 (CHCH3)], [51.6, 51.4 (NimidazoleCH2−)], [47.9, 47.5, 47.4 (NamineCH3)], [38.6, 38.5 (NimidazoleCH3)], [23.8, 23.7 (CHCH3)]. Anal. Calcd for C33H32N3PdI (703.95): C, 56.30; H, 4.58; N, 5.97. Found: C, 56.47; H, 4.63; N, 6.23. Melting point 195−197 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 576.1 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 576.1644; calcd 576.1644, εr 0.01 ppm. General Procedure for the Sythesis of NHC−Palladium− Amine Complexes. In a pyrex tube, 0.3 mmol of finely powered PdCl2, 0.3 mmol of imidazolium salt, 0.35 mmol of chiral primary amine, 0.6 mmol of KI, and 0.6 mmol of Cs2CO3 were suspended in acetonitrile. The suspension was heated at 100° for 2 h. The mixture was filtered over Celite, and the solvent was concentrated under reduced pressure. The crude was redisolved in dichloromethane and washed with a saturated NaCl solution (3 × 10 mL). The organic phase was dried with anhydrous MgSO4. Crystallization from dichloromethane/hexanes afforded the products as yellow crystalline solids. Compound 21. Yield: 143 mg (71%). 1H NMR (300 MHz, CDCl3): δ 8.45 (d, 3JH,H = 8.6 Hz, 1H), 7.89 (d, 3JH,H = 8.3 Hz, 1H), 7.82 (d, 3JH,H = 7.9 Hz, 1H), 7.67−7.44 (m, 4H), 6.88 (s, 2H, CH CH), 5.63−5.39 (m, 1H,, CHCH3), 3.85 (s, 6H, NimidazoleCH3), 2.92− 2.57 (m, 2H, NH2), 1.99 (d, 3JH,H = 6.8 Hz, 3H, CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ 148.9 (Ccarbene−Pd), 140.1, 134.0, 130.3, 129.0, 128.5, 126.8, 125.9, 125.4, 122.9, 122.4, 49.8 (CHCH3), 38.7 (NimidazoleCH3), 23.3 (CHCH3). Anal. Calcd for C17H21N3PdI2 (627.60): C, 32.53; H, 3.37; N, 6.69. Found: C, 32.65; H, 3.56; N, 6.71. Melting point 179−182 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 500.0 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 499.9818; calcd 499.9822, εr 0.8 ppm. Compound 22. Yield: 190 mg (79%) 1H NMR (300 MHz, CDCl3): δ 8.57 (s, 1H), 8.42 (d, 3JH,H = 8.9 Hz, 3H), 8.06 (d, 3JH,H = 7.8 Hz, 2H), 7.83−7.73 (m, 2H), 7.64−7.40 (m, 9H), 6.60 (d, 3JH,H = 2.0 Hz, 1H), 6.58 (s, 1H), 6.09 (d, 3JH,H = 2.0 Hz, 1H), 5.47 (m, 1H, CHCH3), 4.10 (s, 3H, NimidazoleCH3), 2.91 (m, 1H, NH), 2.75 (m, 1H, NH), 2.10 (d, 3JH,H = 6.7 Hz, 3H, CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ, 151.6 (Ccarbene−Pd), 139.6, 133.9, 131.3, 131.2, 130.5, 129.5, 129.1, 128.9, 128.4, 127.4, 126.9, 125.9, 125.4, 125.4, 124.3, 124.0, 122.9, 122.4, 122.3, 120.4, 47.7 (CHCH 3 ), 46.9 (NimidazoleCH2−), 37.8 (NimidazoleCH3), 23.1 (CHCH3). Anal. Calcd for C31H29N3PdI2 (803.81): C, 46.32; H, 3.63; N, 5.22. Found: C, 46.53; H, 3.87; N, 5.67. Melting point 178−180 °C. Electrospray MS (Cone 15 V) (m/z, fragment): 676.9 [M − I]+. General Procedure for the Sythesis of Chiral Palladacycles Bearing Primary Amines with NHC Ligands. In a round-bottom flask were placed together 0.3 mmol of NHC−palladium−amine

compound and 0.72 mmol of AgOAc in 10 mL of acetonitrile. The mixture was refluxed overnight. The resulting mixture was filtered over Celite, and the solvent was removed under reduced pressure. The crude was redissolved in dichloromethane and washed with a saturated NaCl solution (3 × 10 mL). The organic phase was dried with anhydrous MgSO4. Crystallization from dichloromethane/hexanes afforded the products as pale-yellow crystalline solids. Compound 23. Yield: 120 mg (80%). 1H NMR (300 MHz, CDCl3): δ 7.70 (d, 3JH,H = 8.9 Hz, 1H), 7.64 (d, 3JH,H = 8.0 Hz, 1H), 7.42−7.26 (m, 3H), 6.95 (dd, 3JH,H = 11.3, 1.7 Hz, 2H), 6.18 (d, 3JH,H = 8.3 Hz, 1H), 5.21 (s, 1H, CHCH3), 3.94 (s, 3H, NimidazoleCH3), 3.81 (s, 3H, NimidazoleCH3), 3.76 (m, 1H, NH), 3.12 (m, 1H, NH), 1.80 (d, 3 JH,H = 6.4 Hz, 3H, CHCH3). 13C{1H} NMR (75 MHz, CDCl3): δ 174.9 (Ccarbene−Pd), 152.1, 150.1, 133.7, 131.2, 128.5, 128.3, 125.9, 125.8, 123.9, 123.5, 122.1, 122.0, 58.4 (CHCH3), 38.7 (NimidazoleCH3), 38.3 (NimidazoleCH3), 25.8 (CHCH3). Anal. Calcd for C17H20N3PdI (499.68): C, 40.86; H, 4.03; N, 8.41. Found: C, 40.57; H, 3.76; N, 8.21. Melting point 207−210 °C. Electrospray MS (Cone 20 V) (m/z, fragment): 413.0 [M − I + MeCN]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 372.0705; calcd 372.0699, εr 1.6 ppm. Compound 24. Purification by silica gel chromatography with CH2Cl2/AcOEt = 7/3 afforded the product as a pale-yellow solid. Yield: 113 mg (56%) 1H NMR (300 MHz, CDCl3): δ 8.52−8.41 (m, 4H), 8.28 (d, 3JH,H = 8.7 Hz, 2H), 8.06−7.95 (m, 4H), 7.79−7.65 (m, 4H), 7.48−7.14 (m, 16H), 6.71 (dd, 3JH,H = 11.1, 1.9 Hz, 2H), 6.56− 6.44 (m, 4H), 6.26 (dd, 3JH,H = 11.7, 1.9 Hz, 2H), 5.33 (m, 2H, CHCH3), 4.31 (broad s, 2H, NH), 4.03 (s, 3H, NimidazoleCH3), 3.85 (s, 3H, NimidazoleCH3), 3.29 (broad s, 2H, NH), 1.97−1.86 (m, 6H, CHCH3). Diastereomeric ratio: 60/40. 13C{1H} NMR (75 MHz, CDCl3):) δ [174.8, 174.4 2 (Ccarbene−Pd)], 151.5, 135.3, 134.9, 134.0, 131.3, 131.3, 131.2, 131.2, 131.0, 129.2, 129.1, 129.0, 128.9, 128.6, 128.6, 128.5, 128.5, 127.1, 127.1, 125.8, 125.6, 125.3, 125.2, 125.2, 125.1, 124.2, 124.1, 123.9, 123.8, 123.4, 123.3, 121.7, 121.4, 56.5 (CHCH3), [47.5, 47.4 (NimidazoleCH2−)], [38.6, 38.2 (NimidazoleCH3)], [29.7, 25.8 (CHCH3)]. Anal. Calcd for C31H28N3PdI (675.90): C, 55.08; H, 4.17; N, 6.22. Found: C, 55.27; H, 4.46; N, 6.35. Melting point 200−204 °C. Electrospray MS (Cone 20 V) (m/z, fragment): 548.2 [M − I]+. HRMS ESI-TOF-MS (positive mode): [M − I]+ monoisotopic peak 548.1332; calcd 548.1330, εr 0.4 ppm. Catalytic Studies. The palladium complex (2 mol %) and K2CO3 (5 mol %) were placed together in Schlenk tube with a Teflon cap. The tube was purged with nitrogen three times. The solvent (2 mL) was added, and the mixture was stirred at room temperature for 2 h. Then diphenylphosphine (106.6 μL, 0.6 mmol) was added, and the resulting yellow solution was stirred for 5 min. After addition of 1,3diphenyl-2-propen-1-one (106 mg, 0.5 mmol), the resulting mixture was stirred for 15 h at room temperature, then quenched with H2O2 aqueous solution (30%, 200 μL) and EtOAc (3 mL). The mixture was stirred for 2 h and was added 0.4 mL of a saturated Na2S2O3 aqueous solution. The mixture was extracted with dichloromethane three times. The organic phase was dried with MgSO4 and concentrated under vacuum. The residue was purified by silica gel chromatography with CH2Cl2/MeOH = 70/1 to afford the product as a white solid. The ee was determined on a Daicel Chiracel IC column at 30 °C with hexane/ 2-propanol = 70/30, flow = 0.6 mL/min, λ = 250 nm. Retention times: 13.2 min [(S)-enantiomer], 17.2 min [(R)-enantiomer].

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ASSOCIATED CONTENT

S Supporting Information *

General procedures, catalytic studies, high performance liquid chromatography, electrospray mass ionization mass spectroscopy, high resolution mass spectroscopy, nuclear magnetic resonance, X-Ray diffraction studies; crystallographic information file for compounds 9, 11, 15, 21, and 23 (CIF). This material is available free of charge via the Internet at http:// pubs.acs.org. 1118

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Sakodinskaya, I. K.; Yatsimirsky, A. K. J. Chem. Soc., Dalton Trans. 1985, 2629. (8) (a) Vicente, J.; Saurallamas, I.; Jones, P. G. J. Chem. Soc., Dalton Trans. 1993, 3619. (b) Vicente, J.; Saura-Llamas, I.; Oliva-Madrid, M.J.; Garcia-Lopez, J.-A. Organometallics 2011, 30, 4624. (c) Vicente, J.; Saura-Llamas, I.; Cuadrado, J.; de Arellano, M. C. R. Organometallics 2003, 22, 5513. (9) (a) Fuchita, Y.; Yoshinaga, K.; Ikeda, Y.; KinoshitaKawashima, J. J. Chem. Soc., Dalton Trans. 1997, 2495. (b) Yang, F.; Li, Y. P.; Nie, J.; Tang, J.; He, M. Y. Chin. J. Chem. 2003, 21, 1039. (10) Albert, J.; Cadena, J. M.; Granell, J. Tetrahedron: Asymmetry 1997, 8, 991. (11) Churchill, M. R.; Wasserman, H. J.; Young, G. J. Inorg. Chem. 1980, 19, 762. (12) (a) Fernandez, A.; Vazquez-Garcia, D.; Fernandez, J. J.; LopezTorres, M.; Suarez, A.; Castro-Juiz, S.; Vila, J. M. Eur. J. Inorg. Chem. 2002, 2389. (b) Mosteiro, R.; Fernandez, A.; Vazquez-Garcia, D.; Lopez-Torres, M.; Rodriguez-Castro, A.; Gomez-Blanco, N.; Vila, J. M.; Fernandez, J. J. Eur. J. Inorg. Chem. 2011, 1824. (13) (a) Calmuschi, B.; Englert, U. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2002, 58, m545. (b) Calmuschi, B.; Jonas, A. E.; Englert, U. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2004, 60, m320. (c) Calmuschi-Cula, B.; Kalf, I.; Timofte, C.; Englert, U. Acta Crystallogr., Sect. C: Cryst. Struct. Commun. 2009, 65, m48. (14) (a) Tomazela, D. M.; Gozzo, F. C.; Ebeling, G.; Livotto, P. R.; Eberlin, M. N.; Dupont, J. Inorg. Chim. Acta 2004, 357, 2349. (b) Vatsadze, S. Z.; Medved’ko, A. V.; Zyk, N. V.; Maximov, A. L.; Kurzeev, S. A.; Kazankov, G. M.; Lyssenko, K. A. Organometallics 2009, 28, 1027. (15) (a) Enders, D.; Gielen, H. J. Organomet. Chem. 2001, 617, 70. (b) Enders, D.; Gielen, H.; Runsink, J.; Breuer, K.; Brode, S.; Boehn, K. Eur. J. Inorg. Chem. 1998, 913. (16) Dunina, V. V.; Kuz’mina, L. G.; Kazakova, M. Y.; Golunova, O. N.; Grishin, Y. K.; Kazakova, E. I. Eur. J. Inorg. Chem. 1999, 1029. (17) (a) Huang, Y.; Pullarkat, S. A.; Teong, S.; Chew, R. J.; Li, Y.; Leung, P.-H. Organometallics 2012, 31, 4871. (b) Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P.-H. Inorg. Chem. 2012, 51, 2533. (c) Huang, Y.; Chew, R. J.; Pullarkat, S. A.; Li, Y.; Leung, P.-H. J. Org. Chem. 2012, 77, 6849. (d) Huang, Y.; Pullarkat, S. A.; Li, Y.; Leung, P.-H. Chem. Commun. 2010, 46, 6950. (e) Du, D.; Duan, W.-L. Chem. Commun. 2011, 47, 11101. (f) Yuan, M.; Zhang, N.; Pullarkat, S. A.; Li, Y.; Liu, F.; Pham, P.-T.; Leung, P.-H. Inorg. Chem. 2010, 49, 989. (g) Yuan, M.; Pullarkat, S. A.; Li, Y.; Lee, Z.-Y.; Leung, P.-H. Organometallics 2010, 29, 3582. (h) Feng, J.-J.; Chen, X.-F.; Shi, M.; Duan, W.-L. J. Am. Chem. Soc. 2010, 132, 5562. (i) Ibrahem, I.; Hammar, P.; Vesely, J.; Rios, R.; Eriksson, L.; Cordova, A. Adv. Synth. Catal. 2008, 350, 1875. (j) Butti, P.; Rochat, R.; Sadow, A. D.; Togni, A. Angew. Chem., Int. Ed. Engl. 2008, 47, 4878. (k) Barta, K.; Francio, G.; Leitner, W.; Lloyd-Jones, G. C.; Shepperson, I. R. Adv. Synth. Catal. 2008, 350, 2013. (l) Ibrahem, I.; Rios, R.; Vesely, J.; Hammar, P.; Eriksson, L.; Himo, F.; Cordova, A. Angew. Chem.,Int. Ed. Engl. 2007, 46, 4507. (m) Carlone, A.; Bartoli, G.; Bosco, M.; Sambri, L.; Melchiorre, P. Angew. Chem.,Int. Ed. Engl. 2007, 46, 4504. (n) Blank, N. F.; Moncarz, J. R.; Brunker, T. J.; Scriban, C.; Anderson, B. J.; Amir, O.; Glueck, D. S.; Zakharov, L. N.; Golen, J. A.; Incarvito, C. D.; Rheingold, A. L. J. Am. Chem. Soc. 2007, 129, 6847. (o) Xu, Q.; Han, L. B. Org. Lett. 2006, 8, 2099. (p) Shulyupin, M. O.; Francio, G.; Beletskaya, I. P.; Leitner, W. Adv. Synth. Catal. 2005, 347, 667. (q) Scriban, C.; Kovacik, I.; Glueck, D. S. Organometallics 2005, 24, 4871. (r) Douglass, M. R.; Ogasawara, M.; Hong, S.; Metz, M. V.; Marks, T. J. Organometallics 2002, 21, 283. (s) Kovacik, I.; Wicht, D. K.; Grewal, N. S.; Glueck, D. S.; Incarvito, C. D.; Guzei, I. A.; Rheingold, A. L. Organometallics 2000, 19, 950. (18) (a) Ding, Y.; Zhang, Y.; Li, Y.; Pullarkat, S. A.; Andrews, P.; Leung, P.-H. Eur. J. Inorg. Chem. 2010, 4427. (b) Xu, C.; Kennard, G. J. H.; Hennersdorf, F.; Li, Y.; Pullarkat, S. A.; Leung, P.-H. Organometallics 2012, 31, 3022. (19) Huang, M.; Li, C.; Huang, J.; Duan, W.-L.; Xu, S. Chem. Commun. 2012, 48, 11148.

AUTHOR INFORMATION

Corresponding Author

*Phone: (+34) 964387516. Fax: (+34) 964387522. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the financial support from the Ministerio de Ciencia e Innovación of Spain (CTQ2011-24055) and Bancaixa (P1.1B2010-02). We would also like to thank the “Generalitat Valenciana” for a fellowship (S.S.). We are grateful to the ́ Serveis Centrals d’Instrumentació Cientifica (SCIC) of the Universitat Jaume I for providing us with spectroscopic facilities. We thank E. Verdugo and R. Portoles for helping with HPLC chromatography.

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REFERENCES

(1) (a) Elgazwy, A. S. S. H.; Ismail, N. S. M.; Atta-Allah, S. R.; Sarg, M. T.; Soliman, D. H. S.; Zaki, M. Y.; Elgamas, M. A. Curr. Med. Chem. 2012, 19, 3967. (b) Vicente, J.; Saura-Llamas, I. Comments Inorg. Chem. 2007, 28, 39. (c) Albert, J.; Granell, J.; Muller, G. J. Organomet. Chem. 2006, 691, 2101. (2) (a) Vicente, J.; Chicote, M. T.; Martinez-Martinez, A. J.; AbellanLopez, A.; Bautista, D. Organometallics 2010, 29, 5693. (b) Gopi, K.; Thirupathi, N.; Nethaji, M. Organometallics 2011, 30, 572. (c) Omae, I. J. Organomet. Chem. 2007, 692, 2608. (d) Dupont, J.; Consorti, C. S.; Spencer, J. Chem. Rev. 2005, 105, 2527. (e) Omae, I. Coord. Chem. Rev. 2004, 248, 995. (f) Pfeffer, M. Pure Appl. Chem. 1992, 64, 335. (g) Dupont, J.; Pfeffer, M. Palladacycles: Synthesis, Characterization and Applications; Wiley-VCH: New York, 2008. (3) (a) Kong, Y.; Wen, L.; Song, H.; Xu, S.; Yang, M.; Liu, B.; Wang, B. Organometallics 2011, 30, 153. (b) Peh, G.-R.; Kantchev, E. A. B.; Er, J.-C.; Ying, J. Y. Chem.Eur. J. 2010, 16, 4010. (c) Kantchev, E. A. B.; Ying, J. Y. Organometallics 2009, 28, 289. (d) Marion, N.; Nolan, S. P. Acc. Chem. Res. 2008, 41, 1440. (e) Kantchev, E. A. B.; Peh, G.-R.; Zhang, C.; Ying, J. Y. Org. Lett. 2008, 10, 3949. (f) Broggi, J.; Clavier, H.; Nolan, S. P. Organometallics 2008, 27, 5525. (g) Frey, G. D.; Schutz, J.; Herdtweck, E.; Herrmann, W. A. Organometallics 2005, 24, 4416. (h) Bedford, R. B.; Betham, M.; Blake, M. E.; Frost, R. M.; Horton, P. N.; Hursthouse, M. B.; Lopez-Nicolas, R. M. Dalton Trans. 2005, 2774. (i) Viciu, M. S.; Kelly, R. A.; Stevens, E. D.; Naud, F.; Studer, M.; Nolan, S. P. Org. Lett. 2003, 5, 1479. (j) Navarro, O.; Kelly, R. A.; Nolan, S. P. J. Am. Chem. Soc. 2003, 125, 16194. (4) (a) Zanardi, A.; Mata, J. A.; Peris, E. Organometallics 2009, 28, 4335. (b) Zanardi, A.; Mata, J. A.; Peris, E. Organometallics 2009, 28, 1480. (c) Zanardi, A.; Mata, J. A.; Peris, E. Chem.Eur. J. 2010, 16, 10502. (d) Gonell, S.; Poyatos, M.; Mata, J. A.; Peris, E. Organometallics 2011, 30, 5985. (e) Gonell, S.; Poyatos, M.; Mata, J. A.; Peris, E. Organometallics 2012, 31, 5606. (f) Lillo, V.; Mas-Marza, E.; Segarra, A. M.; Carbo, J. J.; Bo, C.; Peris, E.; Fernandez, E. Chem. Commun. 2007, 3380. (5) (a) Harvey, J. S.; Gouverneur, V. Chem. Commun. 2010, 46, 7477. (b) Glueck, D. S. Chem.Eur. J. 2008, 14, 7108. (c) Damian, K.; Clarke, M. L.; Cobley, C. J. Appl. Organomet. Chem. 2009, 23, 272. (d) Han, L. B.; Mirzaei, F.; Zhao, C. Q.; Tanaka, M. J. Am. Chem. Soc. 2000, 122, 5407. (e) Glueck, D. S. In C−X Bond Formation; SpringerVerlag: New York, 2001; Vol. 31. (f) Grabulosa, A. P-Stereogenic Ligands in Enantioselective Catalysis; RSC Publishing: Cambridge, UK, 2010. (g) Grabulosa, A.; Granell, J.; Muller, G. Coord. Chem. Rev. 2007, 251, 25. (6) (a) Tani, K.; Brown, L. D.; Ahmed, J.; Ibers, J. A.; Yokota, M.; Nakamura, A.; Otsuka, S. J. Am. Chem. Soc. 1977, 99, 7876. (b) Gul, N.; Nelson, J. H. J. Mol. Struct. 1999, 475, 121. (7) (a) Gul, N.; Nelson, J. H. Organometallics 2000, 19, 91. (b) Hockless, D. C. R.; Gugger, P. A.; Leung, P. H.; Mayadunne, R. C.; Pabel, M.; Wild, S. B. Tetrahedron 1997, 53, 4083. (c) Ryabov, A. D.; 1119

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Organometallics

Article

(20) Xu, J. X.; Wei, T. Z.; Zhang, Q. H. J. Org. Chem. 2003, 68, 10146. (21) Xu, J. X.; Wei, T. Z.; Lin, S. S.; Zhang, Q. H. Helv. Chim. Acta 2005, 88, 180. (22) (a) Arduengo, A. J. (Du Pont) U.S. Patent 5077414, 1991. (b) Herrmann, W. A. Angew. Chem., Int. Ed. Engl. 2002, 41, 1290. (23) Clark, R. C.; Reid, J. S. Acta Crystallogr., Sect. A: Found. Crystallogr. 1995, 51, 887. (24) (a) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr. 2008, 64, 112. (b) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339.

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