Stoichiometric and Catalytic Cross Dimerization between Conjugated

Article pubs.acs.org/Organometallics

Stoichiometric and Catalytic Cross Dimerization between Conjugated Dienes and Conjugated Carbonyls by a Ruthenium(0) Complex: Straightforward Access to Unsaturated Carbonyl Compounds by an Oxidative Coupling Mechanism Masafumi Hirano,* Yasutomo Arai, Yuka Hamamura, Nobuyuki Komine, and Sanshiro Komiya Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan S Supporting Information *

ABSTRACT: A series of stoichiometric and catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are studied. The reaction of Ru(η4-cisoid-1,3-butadiene)(η4-1,5COD)(NCMe) (2a) with methyl acrylate gives a Ru(0) complex, Ru[methyl η4-cisoid-(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa) in 97% yield. Similar treatments of 2a with a series of tert-butyl acrylate, methyl crotonate, 3-buten-2-one, and N,N-dimethylacrylamide produce similar analogues of 3ac. When (E)-1,3-pentadiene complex 2d is employed in the reaction with methyl acrylate, the branched coupling product Ru[methyl η4-cisoid-(2E,4E)-4-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-b) is dominantly obtained in 65% yield along with the linear product in 19% yield. In the case of the (E)-2,5-dimethylhexa1,3-diene complex 2e, the corresponding branch product is exclusively obtained in 86% yield. The catalytic cross dimerizations between conjugated dienes and conjugated carbonyls are established by 2. The origin of the present chemoselectivity is the η4-coordination of a conjugated diene and η2-coordination of an electron-deficient alkene to formal 6e coordination sites at Ru(0), and the regioselectivity being prone to giving branched products is interpreted as an oxidative coupling mechanism, involving nucleophilic attack of the coordinated diene to the coordinated electron-deficient alkene.

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INTRODUCTION One promising and valuable use of olefin dimerization is the chemoselective cross dimerization of substituted olefins, since it would provide an easy and versatile synthetic methodology for a variety of highly functionalized organic molecules. Cationic and neutral Ru(II) complexes having a Cp or Cp* ligand are known to catalyze cross dimerization reactions among conjugated dienes, electron-rich olefins, distorted olefins, and alkynes.1 Such processes are undoubtedly important, but they often fail when applied to electron-deficient alkenes in general, owing to the formal oxidation state of the metal center.2 We previously reported the high reactivity of Ru(η6-naphthalene)4 (η -1,5-COD) (1) toward oxidative coupling reactions3 such as the catalytic tail-to-tail dimerization of methyl acrylate4 and methyl methacrylate,5 chemo- and diasteroselective cross dimerization of methyl methacrylate and 2,5-dihydrofuran,6 and stoichiometric stereoselective coupling of conjugated dienes.7 In the line of exploration assessment, we found and communicated the reaction of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with methyl acrylate to produce Ru[methyl cisoid-η4-(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa) in quantitative yield, which catalyzed the cross dimerization of 1,3-butadiene and methyl acrylate to give a mixture of (2E,5Z)-MHD and (2E,4E)-MHD (Chart 1).8 © 2012 American Chemical Society

Chart 1. Methyl Heptadienoates (MHD) by Cross Dimerization between 1,3-Butadiene and Methyl Acrylate

The cross dimerization between 1,3-butadiene and methyl acrylate has a long history extending back to the first brief report by Witternberg of a diene complex of Co giving 4,6MHD; however, it fails to address the details of the catalyst and stereoselectivity.9 Uchida and co-workers documented a compelling example reporting the treatment of Fe(acac)3 or Co(acac)3 with AlEt3 to give 2,5-MHD and 3,5-MHD.10 The Fe(acac)3/AlEt3 system was modified to give (2Z,5Z)-MHD and (2E,5Z)-MHD in 1:1 ratio by the addition of Sb(OPh)3,11 or (2Z,5Z)-MHD exclusively in the presence of SbPh3.12 Received: March 21, 2012 Published: May 10, 2012 4006

dx.doi.org/10.1021/om300234d | Organometallics 2012, 31, 4006−4019

Organometallics

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The formation process of 3aa obviously involves a C−C bond-forming step between 1,3-butadiene and methyl acrylate and migration steps of the hydrogen atoms. In order to understand the pathway of hydrogen migration, the naphthalene complex 1 was treated with [1,1,4,4-2H4]-1,3-butadiene (1,3butadiene-d4) (>98 atom % D) in the presence of acetonitrile to give an isotopically labeled 1,3-butadiene complex. These four deuterium atoms in the 1,3-butadiene ligand were unexpectedly distributed among endo-methylene protons in the 1,5-COD ligand of 2a-d4 (Scheme 1).

Branching out from Ziegler-type systems, Wilke and co-workers demonstrated that a “naked cobalt” catalyst displayed poor activity, but CoH(η4-1,5-COD)2 and its equilibrium isomer Co(η1:η2-cyclooct-4-ene-1-yl)(η4-1,5-COD) effectively catalyzed the reaction quantitatively, giving a 4:1 mixture of (2E,5Z)-MHD and (E)-4,6-MHD.13 The related Co(η3-cyclooctenyl)(η4-1,5COD) catalyst was reported to give a 24:1 mixture of (2E,5Z)MHD and (E)-4,6-MHD in hexane.14 The first Ru system was communicated by Mitsudo and co-workers wherein a Ru(0) complex, Ru(η4-1,5-COD)(η6-1,3,5-COT), produces methyl (3E,5Z)-MHD and (2E,5Z)-MHD in a 80:20 ratio.15 In all cases, these pioneering examples, including the Ru(η4-1,5COD)(η6-1,3,5-COT) system, are proposed to proceed by a so-called “hydrido insertion mechanism” with some supporting evidence.16 Herein we disclose a full account of the stoichiometric and catalytic cross dimerization reactions between conjugated dienes and conjugated carbonyls promoted by Ru(η4-conjugated diene)(η4-1,5-COD)(NCMe). The present system offers several advantages over these pioneering systems to give perfect cross selectivity, high tolerance of functional groups, and high branch selectivity for substituted dienes by an oxidative coupling mechanism.

Scheme 1

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Although we do not reveal mechanistic details of this process, we previously documented similar endo-methylene selective deuteration of the 1,5-COD ligand in [RuD(η6-9,10dihydroanthracene)(η4-1,5-COD)]PF6.19 Thus, one of the possible mechanisms for this H/D exchange reaction is C−H bond oxidative addition of a methylene group in the 1,5-COD ligand, giving RuH(η4-CD2CHCHCD2)(η5-C8H11), which reversibly isomerizes to Ru(η3-CD2CHCHCD2H)(η5-C8H11). By this rapid reversible process, the D atoms in the butadiene ligand exchange with the endo-methylene protons in the 1,5COD ligand, and the deuterium content drops to a statistical 50 atom % D. Treatment of 2a-d4 with methyl acrylate gave the 2,4-MHD complex 3aa-d4, where the deuterium atoms were exclusively distributed among the 4- and 5-methines (50 atom % D) and 7methyl (33 atom % D), in addition to the endo-methylenes (50 atom % D) in the 1,5-COD ligand. For a further understanding of this reaction, we have screened the reactivity of substituted alkenes as summarized in Scheme 2. Compound 2a readily reacts with 3-butene-2-one, tert-butyl acrylate, and N,N-dimethylacrylamide (e = −0.26) to give similar coupling products of Ru(0). Of particular interest is the immediate formation of the branched diene compound 3ad by the reaction of 2a with methyl (E)-2-butenoate as a 1,2disubstituted electron-deficient alkene. On the other hand, treatment of 2a with methyl methacrylate (e = 0.40), a 1,1disubstituted electron-deficient alkene, was sluggish and eventually afforded a complex mixture. The reactions of 2a with styrene (e = −0.80) and ethyl vinyl ether (e = −1.80) were also very slow and ultimately produced a mixture of unidentified products. When vinyl acetate (e = −0.88) was employed in this reaction, formation of a thermally unstable coupling product, Ru[(η3-CH2CHCH)CH2CH2{C1H(OC(O1)Me-η1C1,κ1O1)}](η4-1,5-COD)(NCMe) (3af), was observed, which was characterized by 1H NMR, 1H−1H COSY, 13C{1H} NMR, and 13C−1H HETCOR spectroscopic methods. The 13C{1H} NMR spectrum displayed 16 resonances, suggesting all carbon atoms are inequivalent. One of the characteristic features of 3af

RESULTS AND DISCUSSION 1. Reactions of (η4-cisoid-1,3-Butadiene)ruthenium(0) with Substituted Alkenes. A few conjugated diene complexes of Ru(0) containing a 1,5-COD ligand were prepared by Bennett et al.,17 and in a recent collaborative article, we reported the preparation, molecular structures, and properties of an additional series of conjugated diene complexes.18 Conversely, we found that treatment of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with methyl acrylate (e = 0.64) in benzene at 6 °C for 3 h produced the Ru(0) complex Ru[methyl cisoid-η4-(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa), which was isolated as an air-sensitive brown oil in 97% yield (eq 1).

Complex 3aa was characterized by 1H NMR and 1H−1H COSY spectroscopy and interestingly indicated that an ethyl group is attached to the conjugated diene moiety. In the 1H NMR spectrum, the methylene protons of the ethylene fragment are observed to be diastereotopic at δ 1.30 (dquint) and 1.48 (dquint). The correlated 1H resonances at δ 1.22 (q), 1.39 (d), 4.86 (dd), and 6.10 (dd) are assigned as the 5-CH, 2-CH, 4-CH, and 3-CH protons, respectively. The characteristic 3H resonances at δ 0.82 (s) and 3.49 (s) are assignable to the acetonitrile and the methyl ester fragments, respectively. These observations are consistent with the formation of the methyl cisoid-η4-(2E,4E)-hepta-2,4-dienoate fragment at the ruthenium center. The formation of the conjugated diene moiety was also confirmed by the chemical reactions described below. 4007


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α-methine proton in CH{OC(O)Me} fragments. A high-field shift of one of the methine protons in the 1,5-COD ligand at δ 0.68 is probably due to the shielding effect caused by π-electrons in the closely neighboring carbonyl group. Taking into account these features, it is reasonable to postulate the contribution of the (acetato)(carbene) ruthenium(II) resonance extreme in 3af (eq 2). The reason for the thermal

Scheme 2. Reactions of a 1,3-Butadiene Complex with Substituted Olefins

instability of 3af is not clear to date, but one of the possible reasons is the formation of the reactive carbene complex by this α-acetato elimination.22 According to the results in this section, the treatment of 1,3butadiene complex 2a with conjugated carbonyl compounds produced a series of conjugated diene-carbonyl complexes of ruthenium(0). In the case of the reaction of 2a with vinyl acetate, an η1:η3-ruthenacycle was obtained. 2. Reactions of a Series of (η4-cisoid-Diene)ruthenium(0) with Conjugated Carbonyls. Similar treatment of the isoprene analogue 2b with 3-buten-2-one or N,N-dimethylacrylamide produces the related conjugated diene complexes of Ru(0) having a carbonyl group in the conjugated position in 46−59% yields (Scheme 3). Comparatively, similar treatment of the 2,3-dimethylbutadiene complex 2c with conjugated carbonyl compounds gave the coupling products 3ca, 3cb, and 3ce, but subsequent conjugation of the carbonyl groups with the diene fragments was not observed. In fact, the IR spectra of 3aa and 3ca display the ν(CO) band at 1685 and 1730 cm−1, respectively, suggesting stabilization by strong conjugation of the carbonyl group with the diene fragment in 3aa. Nevertheless, 3ca disfavors the 2,4-diene-carbonyl structure. This probably arises from steric repulsion between an endo substituent and the methine proton in cisoid-2,4- and cisoid-3,5diene carbonyl ligands (Chart 2). In order to understand this system’s preference for nonconjugated products, DFT calculations (B3LYP/6-31G*) have been performed. As shown in Chart 3, Ru[methyl cisoid-η4(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3aa), having a conjugated carbonyl group, is 42.6 kJ mol−1 more stable than the terminal diene complex Ru[methyl cisoid-η4-(4E,6E)hepta-4,6-dienoate](η4-1,5-COD)(NCMe) (3aa′). On the other hand, the conjugated carbonyl complex Ru[methyl cisoid-η 4 -(2E,4E)-5,6-dimethylhepta-2,4-dienoate](η 4 -1,5COD)(NCMe) (3ca′) is 30.0 kJ mol−1 less stable than the most stable terminal diene complex, Ru[methyl cisoid-η4-(4E)5,6-dimethylhepta-4,6-dienoate](η4-1,5-COD)(NCMe) (3ca). These thermodynamic analyses help us to understand this experimental result. To our surprise, when the 1,3-pentadiene complex 2d reacted with conjugated carbonyls, the C−C bond-forming reactions primarily took place at the 4-position of the 1,3-pentadiene, giving branched products 3da-b, 3db-b, and 3de-b in 41−65% yields, along with the minor linear regioisomers 3da-l, 3db-l, and 3de-l in 4−21% yields (Scheme 3). The DFT calculations of 2d and the putative key intermediates Ru[cisoid-η4-(E)-1,3pentadiene](η2-methyl acrylate)(η4-1,5-COD) (2dMA) indicate that the 4-position of the 1,3-pentadiene fragment has significantly larger HOMO coefficients than the 1-position in

in the 1H NMR is four allylic resonances at δ 2.28 (td), 2.73 (d), 3.82 (d), and 4.38 (ddd), with coupling constants suggesting anti stereochemistry of the monosubstituted allylic group. Moreover, a slightly broad singlet assignable to C1H was observed at δ 7.74. Although this resonance appeared as a slightly broad singlet, 1H−1H COSY analysis indicated the spin correlation between this resonance and the diastereotopic resonances at δ 3.19 (C2H2, 1H) and 3.27 (C2H2, 1H). Thus, this resonance is assigned as C1H{OC(O)Me}. The low-field resonance of these α-methine protons in the Ru-CH{OC(O)Me} fragment seems to be a common feature, whereas those in [Ru{C1H(Me)OC(O1)Et-η1C1,κ1O1}(SO3CF3)(CO)2]2 and RuCp[C 1 H{OC(O 1 )Me}(CO 2 Et)-η 1 C 1 ,κ 1 O 1 ](PPh 3 ) were documented to appear at δ 6.45 (q) in THF-d820 and δ 6.29 (d) in toluene-d8,21 respectively. We therefore concluded that a low-field resonance is a common characteristic feature for the 4008


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Scheme 3. Reactions of Branched Conjugated Diene Complexes with Conjugated Carbonyls

A branched product, 3ea, was exclusively obtained when we employed (cisoid-η4-2,5-dimethylhexa-1,3-diene)ruthenium(0) (2e) in this reaction. Despite the large steric congestion, this observation implies their electron-deficient alkene favors attack at the diene carbon having an isopropyl group in 2e. We also conclude that this exclusive regioselectivity is achieved by significant induction effects of the isopropyl group in 2e. To summarize, electronic factors likely govern the regioselectivity in the carbon−carbon bond-forming reaction, which involves nucleophilic attack of the Ru(0)-coordinated 1,3-diene on the coordinated electron-deficient alkene. Thermodynamic stability of the coupled products determined the regiochemistry of the CC bond. 3. Molecular Structures of Diene Complexes. As described above, the coupling product 3aa was obtained as an oil. In our previous communication, we have reported the molecular structures of Ru[methyl cisoid-η4-(2E,4E)-hepta-2,4dienoate](η4-1,5-COD)(CO) (3aaCO) and also Ru[methyl cisoid-η 4 -(2E,4E)-hepta-2,4-dienoate](η 4 -1,5-COD)(PPh 3 ) (3aaPPh3) in the Supporting Information. In this article, we report the structures of related compounds. Although single

Chart 2. Potential Regioisomers of 3ca

both cases (Figure 1). Since the present system favors electrondeficient alkenes as described below, the Me group in the 1,3pentadiene fragment enhances the susceptibility toward electrophilic attack at the 4-position through induction effects. For 2dMA, strong interaction with the same phase among the 4-position in 1,3-pentadiene, Ru, and the β-carbon in methyl acrylate is demonstrated in the HOMO level. This scenario is consistent with the product selectivity for 2d. 4009


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recrystallization in cold Et2O. They are depicted in Figure 2, and the selected bond distances and angles are listed in Table 1.23 Although the structure analysis of 3ea is not of high precision, the essential features of the structure are evident. The revealed molecular structure indicates a C−C bond-forming

Chart 3. Relative Thermodynamic Stability between Regioisomers for 3aa and 3ca

Figure 1. Orbital diagrams showing the HOMO for Ru{cisoid-η4-(E)1,3-pentadiene}(η4-1,5-COD)(NCMe) (2d) (left) and Ru[cisoid-η4(E)-1,3-pentadiene](η 2 -methyl acrylate)(η4 -1,5-COD) (2dMA) (right).

crystals of 3ae suitable for X-ray structure analysis could not be obtained, its PPh3 analogue 3aePPh3 produced suitable crystals grown in cold Et2O. Similarly, single crystals of the stoichiometric coupling product between the 2,3-dimethylbutadiene complex 2c and methyl acrylate 3ca were also obtained by

Figure 2. Molecular structures of 3aePPh3, 3ca, and 3ea with selected numbering schemes. All hydrogen atoms are omitted for clarity. Ellipsoids represent 50% probability. These crystallographic and refinement details are summarized in Table 3. 4010


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are only −0.013 Å for 3aePPh3 and 0.006 Å for 3ca and lie in the range −0.1 < Δd < +0.1 Å. Moreover, the external C−Ru− C angles (α) [C(3)−Ru(1)−C(6) for 3aePPh3: 77.77(8)°, C(1)−Ru(1)−C(4) for 3ca: 77.9(4)°] lie between 75° and 90°. Thus, according to Müller’s distinguish method,24 the main contributors to the bonding in 3aePPh3 and 3ca are not the ene-diyl but the diene extreme. Although the dihedral angles for C(5)−C(6)−C(7)−O(1) [−16.8(3)°] and C(5)−C(6)− C(7)−N(1) [164.3(2)°] in 3aePPh3 showed slight deviations out of the plane of the coordinating diene fragment, these groups are likely to conjugate with the diene fragment. 4. Reactions of Diene Complexes. As a typical example for characterization of the coupling products by chemical reactions, a series of reactions of 3aa and the PPh3 analogue 3aaPPh3 are described in this section. As summarized in Scheme 4, iodolysis of 3aa and 3aaPPh3 instantly liberated (2E,4E)-MHD in 80% and 81% yields, respectively, which was confirmed by the authentic sample.25 Thermolysis of 3aa in benzene at 70 °C gave a complex mixture, but that of 3aaPPh3 quantitatively produced Ru(methyl anti,anti-η3-hept-4-enoate-3-yl)(η5-cyclohexa-2,4-diene1-yl) (6), which was characterized by 1H NMR, 1H−1H COSY, 13 C NMR, NOESY, 13C−1H HETCOR, and HOHAHA26 spectroscopic methods. A set of characteristic correlated 1H resonances at δ 4.72 (t, J = 9.0 Hz), 1.77 (t, J = 9.0 Hz) and an overlapping resonance around δ 1.16−1.23 are assignable to the three allylic protons, and the central allylic proton (4-CH) at δ 4.72 is coupled with two allylic protons (3JH−H = 9.0 Hz). The 3 JH−H coupling constants for the syn and anti protons in the η3allylic group (7 and 11 Hz) are typical,27 while the coupling constants of 6 could not be resolved. Since the NOESY spectrum of 6 displayed very weak correlating signals among 3CH, 4-CH, and 5-CH protons, we tentatively assign 6 as the anti product. The methylene protons at 2- and 6-CH2 are observed as diastereotopic, suggesting this fragment coordinates to the Ru center. The correlated 5-methine protons are assigned to the 1,5-η5-cyclooctadienyl ligand. Compound 6 is probably formed by proton migration from the 1,5-COD ligand to the methyl heptadienoate ligand. The most notable reaction is liberation of (2E,4E)-MHD by exposure of 3aaPPh3 to 1,3-butadiene, where a butadiene complex of Ru(0), 2aPPh3, has been reproduced. This stoichiometric reaction promises the catalytic cross dimerization process. In the case of the reaction of 3aa with 1,3-butadiene, supine,proneRu(η3:η3-octa-2,6-diene-1,8-diyl)(η4-1,5-COD) (supine,prone-5) was obtained in 54% yield along with (2E,4E)-MHD. We have reported formation of supine,prone-5 by the treatment of 1 with an excess amount of 1,3-butadiene through Ru(cisoid-η4-1,3butadiene)(transoid-η2-1,3-butadiene)(η4-1,5-COD) as the intermediate.7 Therefore, this reported reaction between 3aa and 1,3-butadiene probably results in the re-formation of 2a with liberation of (2E,4E)-MHD, and 2a successively converts into supine,prone-5. 5. Catalytic Cross Dimerization between Conjugated Dienes and Conjugated Carbonyls. Catalytic reactions between conjugated dienes and conjugated carbonyls have been screened. The rate of catalysis at room temperature was very sluggish, and the yield decreased at high temperature due to catalyst deactivation. With the optimized reaction conditions, the scope of the Ru(0)-catalyzed cross dimerization reaction with respect to various conjugated dienes and conjugated carbonyls was investigated (Table 2).

Table 1. Selected Bond Distances (Å) and Angles (deg) for 3aePPh3, 3ca, and 3ea 3aePPh3 Ru(1)−P(1) Ru(1)−C(4) Ru(1)−C(6) C(4)−C(5) C(6)−C(7) N(1)−C(7) C(3)−Ru(1)−C(6) C(3)−C(4)−C(5) C(5)−C(6)−C(7) O(1)−C(7)−C(6)

2.4350(5) 2.193(2) 2.284(2) 1.407(3) 1.483(2) 1.357(3) 77.77(8) 120.5(2) 116.23(19) 121.8(2)

C(4)−C(5)−C(6)−C(7)

177.2(2)

C(5)−C(6)−C(7)−N(1)

164.3(2) 3ca

Ru(1)−N(1) Ru(1)−C(2) Ru(1)−C(4) C(2)−C(3) C(4)−C(5) C(6)−C(7) O(2)−C(7) C(1)−Ru(1)−C(4) C(2)−C(3)−C(4) C(4)−C(5)−C(6) O(1)−C(7)−C(6) C(1)−C(2)−C(3)−C(4)

2.119(4) 2.203(5) 2.181(4) 1.428(5) 1.512(5) 1.501(6) 1.334(5) 78.39(15) 117.8(4) 114.0(4) 125.9(4) −177.9(4)

C(3)−C(4)−C(5)−C(6)

83.2(5)

Ru(1)−C(3) Ru(1)−C(5) C(3)−C(4) C(5)−C(6) O(1)−C(7)

2.235(2) 2.193(2) 1.407(3) 1.427(3) 1.236(3)

Ru(1)−C(3)−C(4) C(4)−C(5)−C(6) O(1)−C(7)−N(1) C(3)−C(4)−C(5)− C(6) C(5)−C(6)−C(7)− O(1)

69.85(13) 120.0(2) 119.2(2) −5.5(3) −16.8(3)

Ru(1)−C(1) Ru(1)−C(3) C(1)−C(2) C(3)−C(4) C(5)−C(6) O(1)−C(7)

2.160(5) 2.218(5) 1.420(6) 1.422(6) 1.529(7) 1.187(5)

C(1)−C(2)−C(3) C(3)−C(4)−C(5) C(5)−C(6)−C(7) O(1)−C(7)−O(2) C(2)−C(3)−C(4)− C(5) C(4)−C(5)−C(6)− C(7)

117.3(4) 121.6(4) 113.3(4) 123.4(4) 172.4(4)

Ru(1)−C(1) Ru(1)−C(3) C(1)−C(2) C(3)−C(4) O(1)−C(5) C(1)−C(7)

2.223(10) 2.176(9) 1.443(15) 1.423(14) 1.235(13) 1.521(14)

C(1)−C(2)−C(3) C(3)−C(4)−C(5) O(1)−C(5)−O(2) C(11)−C(10)−C(12) C(2)−C(3)−C(4)− C(5)

115.8(9) 118.6(9) 124.8(9) 108.1(10) −179.9(8)

−172.6(4)

3ea Ru(1)−N(1) Ru(1)−C(2) Ru(1)−C(4) C(2)−C(3) C(4)−C(5) O(2)−C(5) C(2)−C(10) C(1)−Ru(1)−C(4) C(2)−C(3)−C(4) O(1)−C(5)−C(4) C(8)−C(7)−C(9) C(1)−C(2)−C(3)−C(4)

2.108(9) 2.233(11) 2.197(10) 1.422(13) 1.478(13) 1.336(13) 1.515(15) 77.9(4) 120.8(9) 124.4(9) 108.8(10) −1.4(14)

C(3)−C(4)−C(5)−O(1) −18.0(15)

product at the more congested side in 2e with methyl acrylate. The unit cell contains two crystallographically independent molecules, one of which is depicted in Figure 2. The metrical data are listed in Table 1 (the second molecule displays similar structural properties). This is consistent with the structural conclusion hypothesized from NMR spectral data. As expected by NMR spectroscopy, complex 3aePPh3 has the carbonyl group in a conjugated position relative to the diene, while the carbonyl group in 3ca is devoid of diene conjugation. The bond distances for the formal C−C single bond in these cisoid diene fragment [1.407(3) Å for 3aePPh3, 1.428(5) Å for 3ca] are almost the same as those for the formal CC double bond [1.407(3) and 1.427(3) Å for 3aePPh3, 1.420(6) and 1.422(6) Å for 3ca], and those differences (Δd) 4011


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Table 2. Ru(0)-Catalyzed Cross Dimerization between Conjugated Dienes and Conjugated Carbonylsb

a

A 1:1 mixture of (2E,4E)-2,4-hexadiene and (2E,4Z)-2,4-hexadiene was used. bCatalyst: 2 mol %, reaction time: 4 h, solvent: benzene. Yields were determined by GLC based on the biphenyl as an internal standard.

As mentioned above, Mitsudo et al. reported this cross dimerization to give (3E,5Z)-MHD as a dominant product by use of a Ru(0) complex, Ru(η4-1,5-COD)(η6-1,3,5-COT), as a catalyst

The cross dimerization reaction between butadiene and methyl acrylate proceeded by both 1,3-butadiene and methyl η4-(2E,4E)hepta-2,4-dienoate complexes of Ru(0) (entries 1 and 2). 4012


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discussed in greater detail in the next section. For the treatment of butadiene with 3-butene-2-one, the catalytic cross dimerization failed, while 3-hexenyl methyl ketone was produced by a Diels−Alder reaction (entry 3). Contrary to these catalyses using electron-deficient olefins, vinyl acetate did not react with 1,3-butadiene at all, although Fujiwara and co-workers indicated that this reaction proceeds by RuCp*Cl(η4-1,5-COD).29 The reaction of 2,3-dimethylbutadiene with methyl acrylate gave cross dimers in almost quantitative total yield (entry 7). 1,3Pentadienes also react with conjugated carbonyls, producing primarily branched products (entries 10−12). A 1:1 mixture of (2E,4E)- and (2E,4Z)-2,4-hexadienes was converted into the branched product (entry 13), although the stoichiometric reaction between 1 and the 2,4-hexadienes produced (cisoidexo-η4-2,5-dimethylhexa-1,3-diene)ruthenium(0) (2e) via isomerization.18 Notably, myrcene, as a branched triene, can also be used in the reaction with methyl acrylate (entry 14). Although myrcene is prone to oligomerization by heat or even at room temperature, this reaction proceeds quantitatively without formation of homocoupling oligomers. Although Jolly and co-workers reported an η4:η2-coordination of the related 2vinylhexa-1,5-diene in the Fe(0) center,30 our preliminary data suggested myrcene also coordinates to Ru(0) in an η4-fashion. It is noteworthy that such cross dimerizations between myrcene and substituted alkenes is still limited.31,32 Catalytic transformation of plant oils is one of the current topics in organometallic chemistry as a renewable feedstock,33 and this reaction opens up potential utilization of the present system for catalytic conversion of terpenoids. 6. Mechanism and the Supporting Reactions. Considering the isotopic labeling experiment and the experimental results described above, the present coupling reaction can be explained as summarized in Scheme 5. It is reported that the naphthalene ligand in 1 is removed in the presence of auxiliary ligand, due to the facile ring-slippage.34

Scheme 4

precursor.15 They confirmed the in situ formation of a (hydrido)ruthenium(II) species28 and proposed a hydrido-insertion mechanism. In our case however, the dominant product is (2E,5Z)-MHD, suggesting a different mechanism. This issue is

Scheme 5. Mechanism for the Stoichiometric and Catalytic Coupling Reactionsa

a

Deuterium labels are shown only for explanation of trails of hydrogen migrations. 4013


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suggested to be described as oxidative coupling. The formations of branched coupling products and 3af underpin this mechanism.

The removal of the coordinated naphthalene ligand formally generates a 6e coordination site at the Ru(0) center, to which the conjugated diene (4e donor) and the alkene (2e donor) coordinate by η4- and η2-fashions, respectively, giving B. This coordination geometry must be the origin of the chemoselectivity in this cross dimerization reaction. In fact, we have isolated similar Ru(0) compounds such as Ru(η4-cisoid-1,3butadiene)(η2-transoid-1,3-butadiene)(η4-1,5-COD) at low temperature as intermediates for the formation of supine,prone-Ru(η3:η3-2,6-octadiene-1,8-diyl)(η4-1,5-COD).7 We have observed formation of the η1:η3 complex 3af when vinyl acetate is employed, which well explains the oxidative coupling mechanism between 1,3-diene and alkene. The highly basic Ru(0) center can be expected to enhance susceptibility toward oxidative coupling. A similar mechanism can most likely be applied to the conjugated carbonyls as well. Following this, oxidative coupling occurs to give C. In the intermediate C, the η3-allylic fragment must have anti stereochemistry because the original butadiene ligand has a cisoid configuration. β-Hydride elimination from C gives D, from which reductive elimination leads to E, where the stereochemistry of the MHD ligand must be (2E,5Z)-MHD. Such an unconjugated diene ligand must be labile and would readily be displaced by 1,3-butadiene if this system is operated under the catalytic conditions. This scenario well accounts for the predominant formation of (2E,5Z)-MHD in the present catalysis. It is less clear how 3aa is formed, but the observed isotopic labeling experiment is consistent with the following pathway. The intermediate E can convert into the more thermodynamically stable conjugated compound. For such isomerization, a C−H bond activation process must be involved. On the basis of the deuterium labeling experiment, the most probable process is the C−H bond oxidative addition of the alkenyl proton at the 5-position to form an (alkenyl)(hydrido)ruthenium(II) species F, which isomerizes to the carbene species G. Notably, no incorporation of deuterium occurred at the 6-position during the formation of 3aa-d4, suggesting selective migration of a deuterium atom from the 4to 5-position in the MHD ligand without scrambling. Although such isomerization processes are rare, it is difficult to explain such selective migration of a deuterium atom to the 5-position in 3aa-d4 without postulation of G. Similar isomerizations from alkenyls to carbenes are well documented.35 Next, G isomerizes to H followed by the reductive elimination giving I. Finally, by displacement of the (2E,4E)-MHD ligand by butadiene produces free (2E,4E)-MHD and 3aa. Alternatively, isomerization of (2E,5Z)-MHD to (2E,4E)-MHD by the in situ formed hydride species may be a potential mechanism for the formation of (2E,4E)-MHD. However, we believe this is fairly unlikely because the (2E,5Z)-MHD/(2E,4E)-MHD ratio does not become altered regardless of the reaction time.

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EXPERIMENTAL SECTION

General Procedures. All manipulations and reactions were performed under dry nitrogen or argon with use of standard Schlenk and vacuum line techniques. Benzene, toluene, hexane, pentane, tetrahydrofuran (THF), and Et2O were distilled over sodium benzophenone ketyl, and dichloromethane and acetonitrile were distilled from Drierite; ethanol was dried over calcium chloride and distilled under nitrogen from magnesium ethoxide. These solvents were stored under a nitrogen atmosphere. 1,3-Butadiene (99.0% pure) was purchased from Takachiho Chemical Industry and used as received. Ru(η6-naphthalene)(η4-1,5-COD) (1) was prepared according to the literature procedure.36 Ru(η4-cisoid-1,3-butadiene)(η4-1,5COD)(NCMe) (2a) and other reported conjugated diene complexes were prepared from 1 based on the literature method.17,18 All other reagents were obtained from commercial suppliers (Wako Pure Chemical Industry, Aldrich, or TCI) and used as received. Benzene-d6 and toluene-d8 were dried over sodium wire, acetonitrile-d3 was dried over Drierite, and dichloromethane-d2 was dried over P4O10, these solvents being stored under vacuum. NMR spectra were recorded on a JEOL LA300 (1H at 300 MHz, 31P at 122 MHz) or a JEOL ECX400P (1H at 399.8 MHz, 13C at 100.5 MHz, 31P at 161.8 MHz) spectrometer. Tetramethylsilane was used as reference for 1H and 13C spectra, and external 85% H3PO4 for 31P spectra. IR spectra were measured on a JASCO FT/IR-4100 spectrometer. Elemental analyses were performed on a Perkin-Elmer 2400 Series II CHN analyzer. The GLC analyses were performed on a Shimadzu GC14B equipped with a TC-WAX (0.25 mm ⦶ × 30 m) under the following conditions: initial temp = 50 °C, initial time = 5 min, program rate = 5 °C/min, final temp = 220 °C, injector temp = 200 °C, detector temp = 200 °C. GC-MS was measured on a Shimadzu QP2010 by use of the electron impact method. Several conjugated diene-carbonyl complexes of Ru(0) were difficult to isolate with satisfactory elemental analysis data, probably due to low stability. They were identified by spectroscopic methods. Reactions of Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe) (2a) with Substituted Alkenes. With Methyl Acrylate. Into a benzene solution (6 mL) of 2a (98.8 mg, 0.325 mmol), methyl acrylate (30.0 μL, 0.333 mmol) was added by a hypodermic syringe, and the solution was stirred at 6 °C for 3 h and then allowed to rise to room temperature for an additional 3 h. After removal of all volatile materials, Ru[methyl η4-cisoid-(2E,4E)-hepta-2,4-dienoate](η4-1,5COD)(NCMe) (3aa) was obtained as a brown oil in 97% yield (122.5 mg, 0.314 mmol). 1H NMR (300 MHz, C6D6, rt): δ 0.82 (s, 1H, NCMe), 0.99 (t, 3H, J = 7.2 Hz, −CH2Me), 1.22 (d, J = 8.4 Hz, 1H, CH), 1.30 (m, 1H, −CHH), 1.39 (d, J = 7.2 Hz, 1H, CH), 1.48 (m, 1H, −CHH), 1.95- 2.1 (m, 4H, COD), 2.15−2.3 (m, 2H, COD), 2.4−2.55 (m, 2H, COD), 3.0−3.1 (m, 1H, COD), 3.3−3.45 (m, 2H, COD), 3.49 (s, 3H, −OMe), 4.52−4.57 (m, 1H, COD), 4.86 (dd, J = 8.1, 4.5 Hz, 1H, CH), 6.10 (dd, J = 7.2, 4.8 Hz, 1H, CH). IR (KBr, cm−1): 1685 (νCO), 2277 (νNCMe), 1586, 1570 (νCC). Anal. Calcd for C18H27NO2Ru: C, 55.37; H, 6.97; N, 3.59. Found: C, 55.46; H, 7.16; N, 2.74. The PPh3 analogue 3aaPPh3 was prepared as follows: complex 3aa (127.3 mg, 0.418 mmol) was treated with methyl acrylate (38.0 μL, 0.420 mmol) in benzene for 6 h as described above, and then PPh3 (109.7 mg, 0.418 mmol) was added into the solution and the reaction mixture was stirred at room temprature for 3 h. After removal of all volatile materials, the resulting yellow powder was recrystallized from cold Et2O to give yellow but slightly black block crystals of Ru[methyl η4-cisoid-(2E,4E)-hepta-2,4-dienoate](η4-1,5COD)(PPh3) (3aaPPh3) in 36% yield (92.3 mg, 0.150 mmol). 1H NMR (300 MHz, C6D6, rt): δ −0.59 (m, 1H, CH), 0.36 (t, J = 7.5 Hz, 1H, CH), 0.69 (t, J = 7.2 Hz, 1H, −CH2Me), 0.75−0.82 (m, 1H, COD), 0.92−1.02 (m, 1H, −CHH), 1.20−1.27 (m, 1H, −CHH), 1.38−1.65 (m, 1H, COD), 1.66−2.42 (m, 7H, COD), 3.44 (s, 3H, −OMe), 3.17−3.20 (m, 1H, COD), 3.81−3.90 (m, 1H, COD),

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CONCLUDING REMARKS In summary, the reactions reported here provide chemoselective cross dimerization between conjugated dienes and electron-deficient alkenes. The formal 6e coordination sites at Ru(0) favor the conjugated diene (4e) and electron-deficient alkene (2e), while the highly Lewis basic Ru(0) center facilitates the oxidative coupling reaction between them. The C−C bondforming step can be regarded as the nucleophilic attack of the coordinated diene fragment to the coordinating alkene, and C−C bond formation prefers the sterically congested side of the 1,3-dienes having an alkyl group owing to the induction effect. The overall mechanism toward the coupling reaction is 4014


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4.70−4.77 (m, 1H, COD), 4.91 (t, J = 7.5 Hz, 1H, CH), 6.27 (t, J = 7.5 Hz, 1H, CH), 6.89−7.08 (m, 9H, PPh3), 7.69−7.80 (m, 6H, PPh3). 31P{1H} NMR (122 MHz, C6D6): δ 51.84 (s). IR (KBr, cm−1): 1691 (νCO), 1586, 1570 (νCC). Anal. Calcd for C34H39O2PRu: C, 66.76; H, 6.43. Found: C, 66.64; H, 6.52. The CO analogue 3aaCO was prepared as follows: similar to 3aaPPh3, complex 3aa was prepared in situ by the reaction of 2a (94 mg, 0.31 mmol) with methyl acrylate (27.8 μL, 0.309 mmol). Then, excess CO (0.1 MPa) was introduced into the solution and the system was stirred for 3 h under CO atmosphere. After removal of all volatile materials, a yellow powder was obtained, which was recrystallized from cold Et2O to give yellow needles of Ru[methyl η4-cisoid-(2E,4E)-hepta-2,4-dienoate](η4-1,5-COD)(CO) (3aaCO) in 53% yield (62.3 mg, 0.165 mmol). 1 H NMR (300 MHz, C6D6, rt): δ 0.77 (m, 1H, CH), 0.78 (t, J = 7.2 Hz, 1H, −CH2Me), 1.01 (m, 1H, −CHH), 1.12 (d, J = 6.9 Hz, 1H, CH), 1.60−1.73 (m, 2H, COD), 1.88−2.01 (m, 4H, COD), 3.31 (s, 3H, −OMe), 3.08−3.10 (m, 2H, COD), 3.41 (m, 1H, −CHH), 3.43− 3.48 (m, 1H, COD), 4.46−4.49 (m, 1H, COD), 4.64 (t, J = 5.7 Hz, 1H, CH), 5.94 (dd, J = 6.9, 5.7 Hz, 1H, CH). IR (KBr, cm−1): 1739 (νRuCO), 1699 (νCO), 1588, 1541 (νCC). Heating of 3aaPPh3 at 70 °C in benzene-d6 produced Ru(methyl anti,anti-η3-hept-4enoate-3-yl)(η5-cyclohexa-2,4-diene-1-yl) (6) in quantitative yield. 6: 1H NMR (300 MHz, C6D6): δ 0.08−0.21 (m, 1H, CH2 in cyclooctadienyl), 0.45−0.55 (m, 1H, CH2 in cyclooctadienyl), 0.68−0.71 (m, 2H, CH2 in cyclooctadienyl), 0.78 (t, J = 7.2 Hz, 3H, 7-Me), 1.16− 1.23 (overlapped, 2H, 6-CH2 and 5-CH), 1.34−1.43 (overlapped, 1H, 6-CHH), 1.42−1.51 (overlapped, 1H, CH2 in cyclooctadienyl), 1.56 (br, 1H, CH2 in cyclooctadienyl), 1.61−1.67 (m, 1H, 2-CH2), 1.77 (t, J = 9.0 Hz, 1H, 3-CH), 3.17 (br, 1H, CH in cyclooctadienyl), 3.41−3.44 (m, 1H, 2-CH2), 3.44−3.55 (m, 1H, CH in cyclooctadienyl), 3.62 (s, 3H, −OMe), 3.89 (br, 1H, CH in cyclooctadienyl), 3.92−3.97 (m, 1H, CH in cyclooctadienyl), 4.72 (t, J = 9.0 Hz, 1H, 4-CH), 5.60 (t, J = 6.0 Hz, 1H, CH in cyclooctadiehyl), 6.98−7.21 (m, 9H, meta- and para-PPh3), 7.62−7.81 (m, 6H, orthoPPh3). 31P{1H} (122 MHz, C6D6): δ 57.31 (s). With 3-Buten-2-on. Similar to the reaction of 2a with methyl acrylate, 2a (5.1 mg, 0.017 mmol) was treated with 3-buten-2-one (2.4 μL, 0.017 mmol) in benzene-d6 (600 μL) under an ice bath for 10 min and then at room temperature for 24 h to give Ru[η4-cisoid(3E,5E)-octa-3,5-dien-2-one](η4-1,5-COD)(NCMe) (3ab) in 92% yield. 1H NMR (300 MHz, C6D6, rt): δ 0.89 (s, 3H, NCMe), 1.02 (t, J = 7.2 Hz, 1H, CH2Me), 1.30−1.24 (m, 1H, CHH), 1.47 (d, J = 7.5 Hz, 1H, CH), 1.52−1.40 (m, 1H, CHH), 1.57−2.50 (m, 8H, COD), 1.87 (s, 3H, −OMe), 2.98−3.04 (m, 1H, COD), 3.15−3.34 (m, 2H, COD), 4.39−4.46 (m, 1H, COD), 4.81 (dd, J = 8.0, 5.3 Hz, 1H, CH), 6.15 (dd, J = 7.5, 5.3 Hz, 1H, CH). Anal. Calcd for C18H27NORu: C, 57.73; H, 7.27; N, 3.74. Found: C, 57.48; H, 7.04; N, 2.46. With tert-Butyl Acrylate. Similar to the reaction with methyl acrylate, the reaction of 2a (6.6 mg, 0.022 mmol) with tert-butyl acrylate (1.9 μL, 0.022 mmol) produced Ru[tert-butyl η4-cisoid-(2E,4E)-hepta2,4-dienoate](η4-1,5-COD)(NCMe) (3ac) in 53% yield. 1H NMR (300 MHz, C6D6, rt): δ 0.88 (s, 3H, −NCMe), 1.01 (t, J = 7.8 Hz, 1H, −CH2Me), 1.16 (m, 1H, CH), 1.32 (d, J = 7.8 Hz, 1H, CH), 1. 38 (m, 1H, −CHH), 1.44 (m, 1H, −CHH), 1.48 (s, 3H, −OMe), 1.9− 2.6 (m, 8H, COD), 3.0−3.1 (m, 1H, COD), 3.3−3.5 (m, 2H, COD), 4.59 (m, 1H, COD), 4.85 (dd, J = 4.8, 8.4 Hz, 1H, CH), 6.07 (dd, J = 4.8, 7.8 Hz, 1H, CH). With Methyl (E)-2-Butenoate. Complex 2a (8.6 mg, 0.028 mmol) in benzene-d6 (600 μL) reacted with methyl (E)-crotonate (5.8 μL, 0.056 mmol) under an ice bath for 10 min and then at room temperature for 4 h to give Ru[methyl cisoid-η4-(2E,4E)-3-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3ad) in 41% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.86 (s, 3H, NCMe), 1.05 (t, J = 7.3 Hz, 3H, 7-Me), 1.07 (s, 1H, 2-CH), 1.22 (dt, J = 7.4, 14.2 Hz, 1H, 5-CH), 1.33 (dquintet, J = 14.2, 7.4 Hz, 1H, 6-CH2), 1.44 (dquintet, J = 14.2 7.4 Hz, 1H, 6-CH2), 1.9−2.1 (m, 3H, COD), 2.2−2.3 (m, 2H, COD), 2.4−2.5 (m, 2H, COD), 2.6 (m, 1H, COD), 2.65 (s, 3H, 3-Me), 2.9 (m, 1H, COD), 3.2−3.3 (m, 2H, COD), 3.46 (s, 3H, −OMe), 4.0−4.1 (m, 1H, COD), 4.66 (d, J = 8.2 Hz, 1H, 4-CH).

With N,N-Dimethylacrylamide. Into an NMR tube containing 2a (7.2 mg, 0.029 mmol) and benzene-d6 (600 μL), N,N-dimethylacrylamide (2.5 μL, 0.029 mmol) was added under an ice bath for 10 min and then at room temperature for 4 h to give Ru[η4-cisoid-(2E,4E)N,N-dimethylhepta-2,4-dienylamide](η4-1,5-COD)(NCMe) (3ae) in 96% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.61 (s, 3H, NCMe), 0.93 (s, 6H, −NMe2), 1.04 (t, J = 7.3 Hz, 1H, 7-Me), 1.15−1.20 (m, 1H, 5CH), 1.25 (d, J = 6.9 Hz, 1H, 2-CH), 1.29−1.40 (m, 1H, 6-CHH), 1.47−1.56 (m, 1H, 6-CHH), 1.89−3.03 (m, 8H, COD), 3.18−3.23 (m, 2H, COD), 3.42−3.47 (m, 1H, COD), 4.55−4.60 (m, 1H, COD), 4.92 (dd, J = 13.8, 5.5 Hz, 1H, 4-CH), 6.43 (dd, J = 6.9, 5.5 Hz, 1H, 3-CH). The PPh3 anaglogue 3aePPh3 was prepared as follows: complex 2a (109.5 mg, 0.360 mmol) was dissolved in benzene (6 mL) and N,N-dimethylacrylamide (37.0 μL, 0.360 mmol) was added. The reaction mixture was stirred under an ice bath for 3 h and then at room temperature for an additional 3 h. Then, PPh3 (94.4 mg, 0.360 mmol) was added into the solution and the mixture was stirred for 3 h. After removal of all volatile materials, a yellow powder was obtained, which was recrystallized from cold Et2O to give yellow block crystals of Ru[η4 -cisoid-(2E,4E)-N,N-dimethylhepta-2,4-dienylamide](η 4-1,5COD)(PPh3) (3aePPh3) in 32% yield (73 mg, 0.117 mmol). 1H NMR (300 MHz, C6D6, rt): δ −0.45 (q, J = 10.8 Hz, 1H, 5-CH), 0.47−0.52 (m, 1H, 2-CH), 0.58 (m, 1H, COD), 0.72 (dt, J = 7.3, 2.8 Hz, 1H, 7-Me), 0.73−0.84 (m, 1H, COD), 0.98−1.20 (m, 2H, 6-CH2), 1.38−1.41 (m, 1H, COD), 1.75−1.95 (m, 3H, COD), 2.09 (m, 1H, COD), 2.18 (s, 3H, −NMe2), 2.27−2.29 (m, 1H, COD), 2.46−2.53 (m, 1H, COD), 2.81 (s, 3H, −NMe2), 3.23−3.27 (m, 1H, COD), 3.76−3.83 (m, 1H, COD), 5.04 (m, 1H, 4-CH), 5.59 (m, 1H, COD), 6.50 (m, 1H, 3-CH), 7.03 (m, 9H, PPh3), 7.64−7.68 (m, 6H, PPh3). IR (KBr, cm−1): 1608 (νCO). Anal. Calcd for C35H42NOPRu: C, 67.12; H, 6.96. Found: C, 67.29; H, 6.78. With Vinyl Acetate. Complex 2a (8.0 mg, 0.026 mmol) in benzened6 (600 μL) reacted with vinyl acetate (2.4 μL, 0.026 mmol) at room temperature immediately to give Ru[(η3-CH2CHCH)CH2CH2{CH(OC(O)Me-η1C,κ1O)}](η4-1,5-COD)(NCMe) (3af) in 68% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.69 (td, 3J = 8.7, 4.1 Hz, 1H, CeH), 1.34 (s, 3H, OC(O)Me), 1.4 (m, 1H, C3H2), 1.7 (m, 1H, CcH2), 2.2 (m, 1H, C3H), 2.2 (m, 1H, CcH2), 2.28 (br m, 1H, CfH), 2.36 (td, 3J = 10.5, 4.1 Hz, 1H, syn-C4H), 2.56 (td, 3J = 8.7, 4.1 Hz, 1H, CaH2), 2.75 (m, 2H, CdH2 and CgH2), 2.80 (d, 3J = 12.8 Hz, 1H, anti-C6H2), 3.07 (dddd, J = 11.4, 10.4, 8.7, 6.2 Hz, 1H, CdH2), 3.28 (tdd, 2J = 3J = 17.4 Hz, 3J = 5.4, 2.3 Hz, 1H, C2H2), 3.36 (br dm, 2J = 17 Hz, 1H, C2H2), 3.64 (br t, 3J = 7 Hz, 1H, CbH), 3.89 (d, 3J = 8.7 Hz, 1H, syn-C6H2), 4.46 (ddd, 3J = 12.8, 10.5, 8.7 Hz, 1H, C5H), 7.86 (br s, 1H, C1H). 13 C{1H} NMR (100 MHz, C6D6, rt): δ 17.8 (s, OC(O)Me), 28.3 (s, Ch), 30.8 (s, Cc), 33.5(or 33.6) (s, C3), 33.6(or 33.5) (s, Cd), 36.1 (s, Cg), 43.5 (s, C6), 56.4 (s, C2), 65.9 (s, Cb), 70.5(or 70.6) (s, Ce), 70.6(or 70.5) (s, Cf), 73.4 (s, Ca), 93.1 (s, C4), 119.9 (s, C5), 124.8 (s, C1), 179.9 (s, OC(O)Me). Reactions of Ru(η4-cisoid-isoprene)(η4-1,5-COD)(NCMe) (2b) with Conjugated Carbonyls. With Methyl Acrylate. Similar to 2a, treatment of 2b (12.8 mg, 0.040 mmol) with methyl acrylate (3.6 μL, 0.040 mmol) produced Ru[methyl η4-cisoid-(2E,4E)-6-methylhepta2,4-dienoate](η4-1,5-COD)(NCMe) (3ba) in 54% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.85 (s, 3H, NCMe), 0.90 (d, J = 6.9 Hz, 3H, 7-Me), 1.04 (t, J = 8.4 Hz, 1H, 5-CH), 1.12 (d, J = 6.9 Hz, 3H, 7-Me), 1.37 (d, J = 7.8 Hz, 1H, 2-CH), 1.33−1.40 (m, 1H, 6-CH), 1.90−2.25 (m, 4H, COD), 2.29−2.56 (m, 3H, COD), 2.61−2.71 (m, 1H, COD), 3.10−3.15 (m, 1H, COD), 3.30−3.34 (m, 1H, COD), 3.40−3.43 (m, 1H, COD), 3.40−3.43 (m, 1H, COD), 3.45 (s, 3H, −OMe), 4.55− 4.60 (m, 1H, COD), 4.85 (dd, J = 8.4, 5.3 Hz, 1H, 4-CH), 6.07 (dd, J = 7.8, 5.3 Hz, 1H, 5-CH). With 3-Buten-2-one. Similar to 2a, treatment of 2b (10.9 mg, 0.034 mmol) with 3-buten-2-one (2.9 μL, 0.035 mmol) gave Ru[η4cisoid-(3E,5E)-7-methylocta-3,5-dien-2-one](η4-1,5-COD)(NCMe) (3bb) in 59% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.90 (s, 3H, NCMe), 0.92 (d, J = 6.4 Hz, 3H, 7-Me), 1.07 (t, J = 8.4 Hz, 1H, 5-CH), 1.14 (d, J = 6.4 Hz, 3H, 7-Me), 1.25−1.37 (m, 1H, 6-CH), 1.43 (d, J = 7.5 Hz, 1H, 2-CH), 1.62−1.65 (m, 1H, COD), 1.89 (s, 3H, −COMe), 1.97−2.05 (m, 2H, COD), 2.16−2.25 (m, 2H, COD), 4015


Organometallics

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2.39−2.56 (m, 2H, COD), 3.06−3.11 (m, 1H, COD), 3.15−3.19 (m, 1H, COD), 3.26−3.29 (m, 1H, COD), 4.42−4.47 (m, 1H, COD), 4.81 (dd, J = 8.6, 5.3 Hz, 1H, 4-CH), 6.12 (dd, J = 7.5, 5.3 Hz, 1H, 5CH). Anal. Calcd for C19H29NORu: C, 58.74; H, 7.52; N, 3.61. Found: 53.93; H, 7.15; N, 2.83. With N,N-Acrylamide. Treatment of 2b (7.1 mg, 0.022 mmol) with N,N-dimethylacrylamide (2.3 μL, 0.023 mmol) gave Ru[η4-cisoid(2E,4E)-N,N,6-trimethyl-2,4-heptadienylamide](η 4 -1,5-COD)(NCMe) (3be) in 46%. 1H NMR (400 MHz, C6D6, rt): δ 0.90 (s, 3H, NCMe), 0.92 (d, J = 6.4 Hz, 3H, 7-Me), 1.07 (t, J = 8.4 Hz, 1H, 5CH), 1.14 (d, J = 6.4 Hz, 3H, 7-Me), 1.25−1.37 (m, 1H, 6-CH), 1.43 (d, J = 7.5 Hz, 1H, 2-CH), 1.62−1.65 (m, 1H, COD), 1.89 (s, 3H, −COMe), 1.97−2.05 (m, 2H, COD), 2.16−2.25 (m, 2H, COD), 2.39−2.56 (m, 2H, COD), 3.06−3.11 (m, 1H, COD), 3.15−3.19 (m, 1H, COD), 3.26−3.29 (m, 1H, COD), 4.42−4.47 (m, 1H, COD), 4.81 (dd, J = 8.6, 5.3 Hz, 1H, 4-CH), 6.12 (dd, J = 7.5, 5.3 Hz, 1H, 5-CH). Reactions of Ru(η4-cisoid-2,3-dimethyl-1,3-butadiene)(η41,5-COD)(NCMe) (2c) with Conjugated Carbonyls. With Methyl Acrylate. Complex 2c (106.1 mg, 0.320 mmol) in benzene (5 mL) was treated with methyl acrylate (28.8 μL, 0.320 mmol) under an ice bath for 3 h and then at room temperature for 3 h. After removal of all volatile materials, a yellow powder was obtained, which was recrystallized from cold Et2O to give yellow block crystals of Ru[methyl η4-cisoid-(6E)-5,6-dimethylhepta-4,6-dienoate](η4-1,5-COD)(NCMe) (3ca) in 32% yield (50.6 mg, 0.102 mmol). 1H NMR (400 MHz, C6D6, rt): δ 0.29 (s, 1H, 7-endo-CH), 0.60 (dd, J = 8.0, 5.1 Hz, 1H, 3-CH), 0.99 (s, 3H, −NCMe), 1.59 (s, 1H, 7-exo-CH), 1.65 (dq, J = 14.7, 8.0 Hz, 1H, 3-CH2), 1.84 (s, 3H, 5- or 6-Me), 2.00 (s, 3H, 6- or 5-Me), 2.02−2.11 (m, 1H, −CH2), 1.91−2.18 (m, 4H, COD), 2.39 (t, J = 8.0 Hz, 2H, 2-CH2), 2.43−2.49 (m, 2H, COD), 2.65−2.87 (m, 3H, COD), 3.17−3.21 (m, 1H, COD), 3.31 (s, 3H, −OMe), 3.68−3.93 (m, 1H, COD). Anal. Calcd for C20H31NO2Ru: C, 57.39; H, 7.47; N, 3.35. Found: 57.05; H, 7.32; N, 3.16. With 3-Buten-2-on. Complex 2c (15.4 mg, 0.046 mmol) in benzene-d6 (600 μL) reacted with 3-buten-2-one (3.9 μL, 0.046 mmol) under an ice bath for 10 min and then at room temperature for 4 h to give Ru{η4-cisoid-(5E)-6,7-dimethylocta-5,7-dien-2-one}(η4-1,5COD)(NCMe) (3cb) in 58% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.52 (s, 1H, 8-endo-CH), 0.69 (s, 3H, NCMe), 1.60 (s, 3H, 6-CMe), 1.62 (m, 2H, 4-CH2), 1.65 (m, 1H, 5-endo-CH), 1.71 (m, 1H, 8-exoCH), 1.73−1.77 (m, 1H, COD), 1.81−1.88 (m, 2H, COD), 1.93 (t, J = 8.6 Hz, 2H, 3-CH2), 1.95−2.00 (m, 3H, COD), 2.02 (s, 3H, 7CMe), 2.02 (s, 3H, −COMe), 2.14−2.20 (m, 1H, COD), 2.23−2.29 (m, 1H, COD), 2.47−2.53 (m, 1H, COD), 2.68−2.71 (m, 1H, COD), 2.76−2.80 (m, 1H, COD), 3.68−3.72 (m, 1H, COD). With N,N-Dimethylacrylamide. Complex 2c (10.2 mg, 0.031 mmol) in benzene-d6 reacted with N,N-dimethylacrylamide (3.2 μL, 0.030 mmol) under an ice bath for 10 min and then at room temperature for 4 h to give Ru[η4-cisoid-(2E,4E)-N,N-dimethylhepta-2,4dienylamide](η4-1,5-COD)(NCMe) (3ce) in 84% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.53 (s, 1H, 7-endo-CH), 0.75 (s, 3H, −NCMe), 0.84−0.88 (m, 1H, 3-CH), 1.71 (s, 1H, 7-exo-CH), 1.88− 1.90 (m, 1H, 3-CH2), 1.92−1.93 (m, 1H, 4-endo-CH), 2.02 (s, 3H, −NMe2), 2.02 (s, 3H, 5-CMe), 2.04 (s, 3H, 6-CMe), 2.02−2.05 (m, 2H, COD), 2.11−2.18 (m, 3H, COD), 2.47−2.53 (m, 2H, COD), 2.65 (s, 3H, NMe2), 2.67−2.70 (m, 2H, COD), 2.76−2.79 (m, 1H, COD), 2.93−2.98 (m, 1H, COD), 3.93 (m, 1H, COD). Anal. Calcd for C21H34N2ORu: C, 58.44; H, 7.94; N, 6.49. Found: 58.77; H, 7.93; N, 5.39. Reaction of Ru[η4-cisoid-(E)-1,3-pentadiene](η4-1,5-COD)(NCMe) (2d) with Conjugated Carbonyls. With Methyl Acrylate. Treatment of 2d (13.3 mg, 0.042 mmol) with methyl acrylate (3.8 μL, 0.042 mmol) gave a mixture of Ru[methyl η4-cisoid-(2E,4E)4-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-b) (65%) and Ru[methyl η4-cisoid-(2E,4E)-octa-2,4-dienoate](η4-1,5-COD)(NCMe) (3da-l) (19%). 3da-b: 1H NMR (400 MHz, C6D6, rt): δ 0.85 (s, 3H, NCMe), 0.95 (t, J = 7.4 Hz, 3H, 7-Me), 1.03 (t, J = 7.4 Hz, 1H, 5-CH), 1.18 (dqui, J = 14.8, 7.4 Hz, 1H, 6-CHH), 1.35 (d, J = 7.1 Hz, 1H, 2-CH), 1.50 (dqui, J = 14.8, 7.4 Hz, 1H, 6-CHH), 1.89 (s, 3H, 4-Me),

1.95−2.04 (m, 3H, COD), 2.21−2.30 (m, 2H, COD), 2.46−2.71 (m, 3H, COD), 3.16−3.21 (m, 1H, COD), 3.29−3.41 (m, 2H, COD), 3.50 (s, 3H, −OMe), 4.43−4.47 (m, 1H, COD), 5.88 (d, J = 7.1 Hz, 1H, 3-CH). Minor: δ 0.83 (s, 3H, NCMe), 0.92 (t, J = 6.9 Hz, 3H, 8-Me), 1.03 (t, J = 7.4 Hz, 1H, 5-CH), 1.20 (m, 1H, 5-CH), 1.38 (d, J = 7.8 Hz, 1H, 2-CH), 1.81−2.87 (overlapped, 8H, COD), 1.95−1.97 (overlapped, 2H, 7-CH2), 2.22−2.24 (overlapped, 2H, 6-CH2), 3.01− 3.06 (m, 1H, COD), 3.48 (s, 3H, −OMe), 3.59−3.63 (m, 1H, COD), 4.24−4.27 (m, 1H, COD), 4.49−4.53 (m, 1H, COD), 4.85−4.89 (m, 1H, 4-CH), 6.08−6.11 (m, 1H, 3-CH). Anal. as a mixture of isomers: Calcd for C19H29NO2Ru: C, 56.41; H, 7.23; N, 3.46. Found: 56.00; 6.64; N, 2.44. With 3-Buten-2-one. Treatment of 2d (15.8 mg, 0.050 mmol) with 3-buten-2-one (4.2 μL, 0.050 mmol) gave a mixture of Ru[η4-cisoid(3E,5E)-5-methylocta-3,5-dien-2-one](η4-1,5-COD)(NCMe) (3db-b) (41%) and Ru[η4-cisoid-(3E,5E)-nona-3,5-dien-2-one](η4-1,5-COD)(NCMe) (3db-l) (21%). 3db-b: 1H NMR (400 MHz, C6D6, rt): δ 0.90 (s, 3H, NCMe), 0.98 (t, J = 6.9 Hz, 3H, 7-Me), 1.07 (t, J = 6.9 Hz, 1H, 5-CH), 1.15 (dqui, J = 13.8, 6.9 Hz, 1H, 6-CHH), 1.43 (d, J = 7.4 Hz, 1H, 2-CH), 1.44−1.56 (m, 1H, 6-CHH), 1.89 (s, 3H, 4-Me), 1.93 (s, 3H, −COMe), 1.70−2.58 (m, 9H, COD), 3.12−3.15 (m, 2H, COD), 4.30−4.34 (m, 1H, COD), 5.95 (d, J = 7.4 Hz, 1H, 3-CH). Minor: δ 0.87 (s, 3H, NCMe), 0.94 (t, J = 7.4 Hz, 3H, 9-Me), 1.08− 1.11 (overlapped, 1H, 7-CHH), 1.31−1.34 (m, 1H, 6-CH), 1.38−1.44 (overlapped, 2H, 8-CH2), 1.47 (d, J = 6.4 Hz, 1H, 5-CH), 1.89 (s, 3H, −COMe), 1.91−2.58 (overlapped, 7H, COD), 2.76−2.81 (m, 1H, COD), 2.98−3.02 (m, 1H, COD), 3.15−3.19 (overlapped, 1H, COD), 3.32−3.36 (m, 1H, COD), 4.40−4.43 (m, 1H, COD), 4.83 (t, J = 6.4 Hz, 1H, 5-CH), 6.15 (t, J = 6.4 Hz, 1H, 4-CH). With N,N-Dimethylacrylamide. Treatment of 2d (16.1 mg, 0.051 mmol) with N,N-dimethylacrylamide (5.2 μL, 0.051 mmol) gave Ru[η4-cisoid-(2E,4E)-N,N,4-trimethylhepta-2,4-dieylamide](η4-1,5COD)(NCMe) (3de-b) (60%) and Ru[η4-cisoid-(2E,4E)-N,N-dimethylocta-2,4-dienylamide](η4-1,5-COD)(NCMe) (3de-l) (4%). 3de-b: 1 H NMR (400 MHz, C6D6, rt): δ 0.95 (s, 3H, NCMe), 0.99 (t, J = 7.3 Hz, 3H, 7-Me), 1.20 (t, J = 7.3 Hz, 1H, 5-CH), 1.21 (d, J = 6.9 Hz, 1H, 2-CH), 1.18−1.27 (m, 1H, 6-CHH), 1.55 (dqui, J = 14.6, 7.3 Hz, 1H, 6-CHH), 1.96 (s, 3H, 4-Me), 1.96 (s, 3H, -NMe2), 1.97−2.23 (m, 3H, COD), 2.27 (s, 3H, −NMe2), 2.41−3.04 (m, 6H, COD), 3.10−3.15 (m, 2H, COD), 4.45−4.50 (m, 1H, COD), 6.22 (d, J = 6.9 Hz, 1H, 3-CH). The resonances of the minor isomer were almost overlapped with the major isomer. Because of the general treand of these reactions, we tentatively assigned it as the linear isomer. 1H NMR (400 MHz, C6D6, rt): δ 4.56 (m, 1H, COD), 4.82 (m, 1H, 4-CH), 6.22 (m, 1H, 3-CH). Anal. as a mixture of isomers: Calcd for C20H32N2ORu: C, 57.53; H, 7.72; N, 6.71. Found: C, 57.22; H, 7.78; N, 5.87. Reaction of Ru[η4-cisoid-(E)-2,5-dimethylhexa-1,3-diene](η41,5-COD)(NCMe) (2e) with Methyl Acrylate. Treatment of 2e (9.8 mg, 0.027 mmol) with methyl acrylate (2.5 μL, 0.029 mmol) gave Ru[methyl η4-cisoid-(2E,4E)-4-isopropyl-6-methylhepta-2,4-dienoate](η4-1,5-COD)(NCMe) (3ea) in 87% yield. 1H NMR (400 MHz, C6D6, rt): δ 0.74 (d, J = 9.2 Hz, 1H, 5-CH), 0.89 (s, 3H, NCMe), 0.95 (t, J = 7.4 Hz, 3H, 7-Me), 1.05 (s, 3H, 6 or 7-Me), 1.11 (s, 3H, 6 or 7-Me), 1.20 (s, 3H, 4-CHMe), 1.30 (d, J = 7.6 Hz, 1H, 2-CH), 1.35− 1.42 (m, 1H, 6-CHMe), 1.45 (s, 3H, 4-CHMe), 1.82−1.87 (m, 1H, COD), 1.95−2.09 (m, 1H, COD), 2.26 (septet, J = 6.6 Hz, 1H, 4CHMe), 2.35−2.52 (m, 3H, COD), 2.60−2.74 (m, 2H, COD), 3.03− 3.08 (m, 1H, COD), 3.13−3.17 (m, 1H, COD), 3.39−3.44 (m, 1H, COD), 3.50 (s, 3H, −OMe), 4.43−4.47 (m, 1H, COD), 6.08 (d, J = 7.6 Hz, 1H, 3-CH). Anal. Calcd for C22H35NO2Ru, C, 59.17; H, 7.90; N, 3.14. Found: C, 59.30; H, 8.03; N, 3.14. Catalytic Reactions between Conjugated Dienes and Conjugated Carbonyls. As a typical example, the reaction of 1,3butadiene with methyl acrylate was described. The product yields were estimated from the GLC analysis with an internal standard method (dibenzyl as a standard). The minor species, which could not be characterized by NMR spectrum, were determined by GLC and GCMS by assuming the same relative sense as the major species in GLC. 1,3-Butadiene with Methyl Acrylate. In a Schlenk tube, 2a (30.0 mg, 0.10 mmol) was dissolved in benzene (2 mL), and then 4016


Organometallics

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methyl acrylate (480 μL, 5.0 mmol) was introduced by a hypodermic syringe. The solution was moved to a stainless steel autoclave (50 mL volume) by a cannular tube. 1,3-Butadiene (113 mL, 5.0 mmol) was introduced into the autoclave, and the reaction vessel was heated at 70 °C for 4 h. After the reaction, the solution was moved to an Erlenmeyer flask, and all volatile materials were removed by a rotary evaporator. The product was confirmed by 1H NMR, GLC, and GCMS. (2E,5Z)-MHD: 1H NMR (CDCl3, 300 MHz): δ 1.60 (d, J = 7.5 Hz, 3H, 7-Me), 2.93 (t, J = 6.3 Hz, 2H, 4-CH2), 3.70 (s, 3H, −OMe), 5.38 (dtq, J = 13.8, 6.9, 1.5 Hz, 1H, 5-CH), 5.61 (dqt, J = 14.4, 5.4, 1.5 Hz, 1H, 6-CH), 5.82 (dt, J = 15.6, 1.8 Hz, 1H, 2-CH), 6.94 (dt, J = 15.6, 6.2 Hz, 1H, 3-CH). GLC: retention time (min) = 17.33. MS (m/ e): 140 (M+), 111, 109, 81. Lit.14 1H NMR (CDCl3, 360 MHz): δ 1.63 (d, J = 6.7 Hz, 3H), 2.95 (dd, J = 6.6, 6.4 Hz, 2H), 3.73 (s, 3H), 5.35− 5.48 (m, 1H), 5.55−5.71 (m, 2H), 5.84 (dt, J = 15.7, 1.7 Hz, 1H), 6.96 (dt, J = 15.7, 6.3 Hz, 1H). Minor species: retention time (min) = 14.20, 16.12. 1,3-Butadiene with 3-Buten-2-one. 3-Cyclohexenyl-2-ethanone. Yield: 85%. 1H NMR (400 MHz, C6D6, rt): δ 1.43−1.46 (m, 1H, 1-CH in cyclohexenyl), 1.59−1.66 (m, 2H, 2- and 5-CH of cyclohexenyl), 1.67 (s, 3H, −COMe), 1.73−1.94 (m, 2H, 2- and 5-CH of cyclohexenyl), 2.08−2.11 (m, 2H, 6-CH2 of cyclohexenyl), 5.56−5.62 (m, 2H, 3- and 4-CH2 of cyclohexenyl). GLC: retention time (min) = 15.81. MS (m/z): 124 (M+). 1,3-Butadiene with N,N-Dimethylacrylamide. (2E,5Z)-N,NDimethylhepta-2,5-dienylamide. Yield: 35%. 1H NMR (400 MHz, C6D6, rt): δ 1.59 (dd, J = 6.8, 1.2 Hz, 3H, 7-CH3), 2.15 (s, 3H, −NMe2), 2.62 (s, 3H, −NMe2), 2.83 (d, J = 6.8 Hz, 2H, 2-CH2), 5.34 (dq, J = 10.7, 6.8 Hz, 1H, 6-CH), 5.93 (dt, J = 15.3, 6.8 Hz, 1H, 3CH), 6.08 (t, J = 10.7 Hz, 1H, 4-CH), 6.39 (ddq, J = 15.3, 10.7, 1.2 Hz, 1H, 5-CH). GLC: retention time (min) = 32.45. Minor species: retention time (min) = 31.43, 32.31. 2,3-Dimethylbutadiene with Methyl Acrylate. Methyl (3E)5,6-dimethyl-3,5-heptadienoate. Yield: 71%. 1H NMR (400 MHz, C6D6, rt): δ 1.58 (s, 3H, 5, 6, or 7-Me), 1.64 (s, 3H, 5, 6, or 7-CH3), 1.70 (s, 3H, 5, 6, or 7-CH3), 2.99 (d, J = 7.5 Hz, 2H, 2-CH2), 3.32 (s, 3H, −OMe), 5.74 (dt, J = 15.4, 7.5 Hz, 1H, 3-CH), 6.58 (d, J = 15.4 Hz, 1H, 4-CH). GC: retention time (min) = 24.58. Methyl (2E)5,6-dimethyl-2,5-heptadienoate. Yield: 26%. 1H NMR (400 MHz, C6D6, rt): δ 1.43 (s, 3H, 5, 6, or 7-CH3), 1.44 (s, 3H, 5, 6, or 7-CH3), 1.48 (s, 3H, 5, 6, or 7-CH3), 2.57 (d, J = 6.6 Hz, 2H, 4-CH2), 3.38 (s, 3H, −OMe), 5.89 (d, J = 15.6 Hz, 1H, 2-CH), 7.01 (dt, J = 15.6, 6.6 Hz, 1H, 3-CH). GLC: retention time (min) = 22.03. Minor species: retention time (min) = 31.43, 32.31. 2,3-Dimethylbutadiene with 3-Buten-2-one. 1H NMR (400 MHz, C6D6, rt): δ 1.47 (s, 6H, 6, 7, or 8-Me), 1.52 (s, 3H, 6, 7, or 8-Me), 1.84 (s, 3H, −COMe), 2.57 (d, J = 6.2 Hz, 2H, 3-CH2), 5.98 (d, J = 15.8 Hz, 1H, 5-CH), 6.43 (dt, J = 15.8, 6.2 Hz, 1H, 3-CH),. GLC: retention time (min) = 22.81. Minor species: retention time (min) = 22.53. 2,3-Dimethylbutadiene with N,N-Dimethylacrylamide. (3E)N,N,5,6-Tetramethyl-3,5-heptadienylamide. Yield: 75%. 1H NMR (400 MHz, C6D6, rt): δ 1.60 (s, 3H, 5, 6, or 7-CH3), 1.70 (s, 3H, 5, 6, or 7-CH3), 1.74 (s, 3H, 5, 6, or 7-CH3), 2.21 (s, 3H, −NMe2), 2.65 (s, 3H, −NMe2), 2.95 (d, J = 6.8 Hz, 1H, 2-CH), 5.92 (dt, J = 15.6, 6.8 Hz, 1H, 3-CH), 6.52 (d, J = 15.6 Hz, 1H, 4-CH). GLC: retention time (min) = 37.95. Minor species: retention time (min) = 35.82, 37.07. Isoprene with Methyl Acrylate. Methyl (3E)-6-methyl-3,5heptadienoate. 1H NMR (400 MHz, C6D6, rt): δ 1.52 (s, 3H, 6 or 7-Me), 1.58 (s, 3H, 6 or 7-Me), 2.91 (d, J = 7.1 Hz, 2H, 2-CH2), 3.31 (s, 3H, −OMe), 5.68 (dt, J = 15.0, 7.1 Hz, 1H, 3-CH), 5.80 (d, J = 11.1 Hz, 1H, 5-CH), 6.26 (dd, J = 15.0, 11.1 Hz, 1H, 4-CH). GLC: retention time (min) = 22.54. Minor species: retention time (min) = 16.81, 19.37, 20.22, 21.93. Isoprene with 3-Buten-2-one. (3E)-7-Methyl-3,6-octadien-2one. Yield: 23%. 1H NMR (400 MHz, C6D6, rt): δ 1.39 (s, 3H, 7 or 8-Me), 1.58 (s, 3H, 8 or 7-Me), 1.89 (s, 3H, −COMe), 2.55 (m, 2H, 5-CH2), 4.99 (t, J = 7.3 Hz, 1H, 5-CH), 6.00 (d, J = 15.7 Hz, 1H, 3CH), 6.41 (dt, J = 15.7, 6.4 Hz, 1H, 4-CH). GC: retention time (min) = 20.73. (4E)-7-Methyl-4,6-octadien-2-one. Yield: 12%. 1H NMR

(400 MHz, C6D6, rt): δ 1.51 (s, 3H, 7 or 8-Me), 1.61 (s, 3H, 7 or 8Me), 1.85 (s, 3H, −COMe), 2.79 (d, J = 7.3 Hz, 2H, 3-CH2), 5.59 (dt, J = 15.2, 7.3 Hz, 1H, 4-CH), 5.81 (d, J = 11.0 Hz, 1H, 6-CH), 6.21 (dd, J = 15.2, 11.0 Hz, 1H, 5-CH). GLC: retetntion time (min) = 19.69. (E)-1,3-Pentadiene with Methyl Acrylate. Methyl (2E,5Z)-4methyl-2,5-heptadienoate. Yield: 41%. 1H NMR (400 MHz, C6D6, rt): δ 0.84 (d, J = 6.9 Hz, 3H, 4-Me), 1.35 (dd, J = 6.9, 1.8 Hz, 3H, 7-Me), 3.01 (sextet, J = 6.9 Hz, 1H, 4-CH), 3.45 (s, 3H, −OMe), 5.05 (dt, J = 10.0, 1.8 Hz, 1H, 5-CH), 5.33 (dq, J = 10.0, 6.9 Hz, 1H, 6-CH), 5.86 (d, J = 15.6 Hz, 1H, 2-CH), 6.99 (dd, J = 15.6, 6.9 Hz, 1H, 3-CH). GLC: retention time (min) = 18.24. Minor species: retetntion time (min) = 16.93, 20.11, 21.54. (Z)-1,3-Pentadiene with Methyl Acrylate. Methyl (2E,5Z)-4methyl-2,5-heptadienoate. Yield: 23%. (E)-1,3-Pentadiene with 3-Buten-2-one. (3E,6Z)-5-Methylocta3,6-dien-2-one. Yield: 16%. 1H NMR (400 MHz, C6D6, rt): δ 0.85 (d, J = 6.9 Hz, 3H, 5-Me), 1.38 (d, J = 6.9 Hz, 3H, 8-Me), 1.84 (s, 3H, 1COMe), 3.01 (m, 1H, 5-CH), 5.06 (m, 1H, 6-CH), 5.35 (dq, J = 11.0, 6.9 Hz, 1H, 7-CH), 5.95 (d, J = 16.0 Hz, 1H, 3-CH), 6.44 (dd, J = 16.0, 6.4 Hz, 1H, 4-CH). GLC: retention time (min) = 18.16. Minor species: retention time (min) = 18.85, 20.34, 21.16. (E)-1,3-Pentadiene with N,N-Dimethylacrylamide. (2E,5Z)N,N,4-Trimethylhepta-2,5-dienylamide. Yield: 44%. 1H NMR (400 MHz, C6D6, rt): δ 0.97 (d, J = 6.9 Hz, 3H, 4-Me), 1.45 (d, J = 6.9 Hz, 3H, 7-Me), 2.36 (s, 3H, −NMe2), 2.72 (s, 3H, −NMe2), 3.17 (m, 1H, 4-CH), 5.21 (m, 1H, 5-CH), 5.39 (m, 1H, 6-CH), 6.09 (d, J = 15.1 Hz, 1H, 2-CH), 7.10 (m, 1H, 3-CH). GLC: retention time (min) = 31.97. Minor species: retention time (min) = 26.26, 33.78, 34.62. 2,4-Hexadiene with Methyl Acrylate. Methyl (2E,5Z)-4methylocta-2,5-dienoate. Yield: 18%. 1H NMR (400 MHz, C6D6, rt): δ 0.80 (t, J = 7.6 Hz, 3H, 8-Me, 0.85 (d, J = 6.9 Hz, 3H, 4-CHMe), 1.81 (m, 2H, 7-CH2), 3.01 (m, 1H, 4-CH), 3.43 (s, 3H, −OMe), 5.01 (dd, J = 10.6, 9.2 Hz, 2H, 5-CH), 5.32 (dt, J = 10.6, 7.4 Hz, 1H, 6-CH), 5.86 (d, J = 15.6 Hz, 1H, 2-CH), 6.98 (dd, J = 15.6, 6.4 Hz, 1H, 3CH). GLC: retention time (min) = 20.17. 2,4-Hexadiene with N,N-Dimethylacrylamide. Methyl (2E,5Z)-4-methylocta-2,5-dienoate. Yield: 18%. 1H NMR (400 MHz, C6D6, rt): δ 0.86 (t, J = 7.3 Hz, 3H, 8-Me), 0.98 (d, J = 6.9 Hz, 3H, 4CHMe), 1.90 (m, 2H, 7-CH2), 2.31 (s, 3H, −NMe2), 2.72 (s, 3H, −NMe2), 3.16 (m, 1H, 4-CH), 5.17 (m, 1H, 5-CH), 5.37 (dt, J = 11.0, 6.9 Hz, 1H, 6-CH), 6.09 (d, J = 15.1 Hz, 1H, 2-CH), 7.15 (dd, J = 15.1, 6.9 Hz, 1H, 3-CH). GLC: retention time (min) = 33.23. Myrcene with Methyl Acrylate. Methyl (3E,5Z)-6,10-dimethylundeca-3,5,9-trienoate. Yield: 67%.1H NMR (400 MHz, C6D6, rt): δ 1.53 (s, 3H, 6, 10, or 11-Me), 1.59 (s, 3H, 6, 10, or 11-Me), 1.64 (s, 3H, 6, 10, or 11-Me), 1.91−2.13 (m, 4H, 7 and 8-CH2), 2.91 (d, J = 7.3 Hz, 2H, 2-CH2), 3.30 (s, 3H, −OMe), 5.11−5.18 (m, 1H, 9-CH), 5.71 (dt, J = 15.1, 7.3 Hz, 1H, 3-CH), 5.89 (d, J = 10.8 Hz, 1H, 5-CH), 6.29 (dd, J = 15.1, 10.8 Hz, 1H, 4-CH). GLC: retention time (min) = 34.43. Methyl (3E)-5-ethylydene-9-methylundeca-3,8-dienoate. Yield: 23%. 1H NMR (400 MHz, C6D6, rt): δ 1.37 (d, J = 6.9 Hz, 3H, 4 CHMe), 1.52 (s, 3H, 9 or 10-Me), 1.65 (s, 3H, 9 or 10-Me), 1.91−2.13 (m, 4H, 6 and 7-CH2), 2.61 (d, J = 6.4 Hz, 2H, 2-CH2), 3.41 (s, 3H, −OMe), 5.11−5.18 (m, 1H, 8-CH), 5.25 (d, J = 6.9 Hz, 1H, 4 CHCH3), 5.91 (d, J = 15.6 Hz, 1H, 4-CH), 7.01 (dt, J = 15.6, 6.4 Hz, 1H, 3-CH). GLC: retention time (min) = 31.43. Ru(η4-myrcene)(η4-1,5-COD)(NCMe). Treatment of 1 (178.0 mg, 0.5275 mg) with myrcene (91.0 μL, 0.528 mmol) in MeCN (6 mL) at rt for 2 h and then at 50 °C for 2.5 h followed by the workup procedure produced a light brown powder of Ru(η4-myrcene)(η4-1,5COD)(NCMe) in 54% yield (111.0 mg, 0.287 mmol). 1H NMR (400 MHz, rt, C6D6): δ 0.49 (d, J = 7.3 Hz, 1H, endo-1-CH), 0.59 (s, 1H, endo-3′-CH), 0.74 (br s, 3H, NCMe), 1.66 (s, 3H, 7 or 8-Me), 1.74 (s, 3H, 8 or 7-Me), 1.74 (s, 1H, exo-3′-CH), 1.76 (d, J = 7.3 Hz, 1H, exo-1CH), 2.2−2.3 (m, 2H, 4-CH2), 2.6−2.7 (m, 2H, 5-CH2), 2.0−2.8 (overlapped, 8H, CH2 in COD), 2.86 (m, 1H, CH in COD), 3.17 (m, 1H, CH in COD), 3.53 (m, 1H, CH in COD), 3.75 (m, 1H, CH in COD), 4.99 (t, J = 7.3 Hz, 1H, 2-CH), 5.53 (t, J = 7.3 Hz, 1H, 6-CH). Computations. Density functional calculations37 were carried out on compounds 2d, 3aa, and 3ca and on the model complexes 2dMA, 4017


Organometallics

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*Phone and Fax: +81 423 877 044. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Ms. S. Kiyota for elemental analysis. We also wish to thank Dr. M. T. Zamora for stimulating discussions. This work was financially supported from the Ministry of Education, Culture, Science and Technology of Japan.

3aa′, and 3ca′ using Spartan’0638 with the hybrid Becke 3LYP/6-31G*. All relative energy values discussed and displayed throughout the computational section of this paper are in kJ mol−1 and were calculated at 298 K. X-ray Structure Analysis. Single crystals suitable for X-ray structure analysis were obtained from recrystallization of 3aePPh3, 3ca, and 3ea from cold Et2O. A Rigaku AFC-7R-Mercury II diffractometer with graphitemonochromated Mo Kα radiation (λ = 0.71075 Å) was used for data collection at 200.0 K. A selected single crystal was mounted on a glass capillary by use of Paraton N oil. The collected data were solved by direct methods (SIR92) and refined by a full-matrix least-squares procedure using SHELXL-97.39 All non-hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms were placed using the riding model. The crystallographic and refiment details are listed in Table 3.

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(1) (a) Ura, Y.; Sato, Y.; Shiotsuki, M.; Kondo, T.; Mitsudo, T. J. Mol. Catal. A: Chem. 2004, 209, 35. (b) Ura, Y.; Sato, Y.; Tsujita, H.; Kondo, T.; Imachi, M.; Mitsudo, T. J. Mol. Catal. A: Chem. 2005, 239, 166. (c) Kondo, T. Bull. Chem. Soc. Jpn. 2011, 84, 441. (2) Ru(0)-catalyzed dimerization and trimetization of ethylene and stryrene: (a) Kondo, T.; Yamamoto, K.; Takagi, D.; Shen, L.; Yoshida, Y.; Kimura, Y.; Toshimitsu, A.; Kuramoto, M.; Shiraki, Y. ChemCatChem 2010, 2, 1565. (b) Kondo, T.; Takagi, D.; Tsujita, H.; Ura, Y.; Wada, K.; Mitsudo, T. Angew. Chem., Int. Ed. 2007, 46, 5958. N-Methyl-N-vinylacetamide with ethyl acrylate: Tsujita, H.; Ura, Y.; Matsuki, S.; Wada, K.; Kondo, T. Angew. Chem., Int. Ed. 2007, 46, 5160. (3) The term “oxidative coupling” is also used for the coupling of two molecular entities through an oxidative process with an oxidant. However, in this article, the oxidative coupling reaction is defined as the metal-induced coupling reactions between two unsaturated compounds to give a metallacycle: Crabtree, R. H. The Organometallics Chemistry of the Transition Metals, 3rd ed.; Wiley: New York, 2001; p 168. (4) Hirano, M.; Sakate, Y.; Komine, N.; Komiya, S.; Bennett, M. A. Organometallics 2009, 28, 4902. (5) Hirano, M.; Hiroi, Y.; Komine, N.; Komiya, S. Organometallics 2010, 29, 3690. (6) Hiroi, Y.; Komine, N.; Hirano, M.; Komiya, S. Organometallics 2011, 30, 1307. (7) Hirano, M.; Sakate, Y.; Komine, N.; Komiya, S.; Wang, X.-Q.; Bennett, M. A. Organometallics 2011, 30, 768. (8) Hirano, M.; Arai, Y.; Komine, N.; Komiya, S. Organometallics 2010, 29, 5741. (9) Witternberg, D. Angew. Chem. 1963, 75, 1124. (10) Misono, A.; Uchida, Y.; Saito, T.; Uchida, K. Bull. Chem. Soc. Jpn. 1967, 40, 1889. (11) Tolstikov, G. A.; Dzhemilev, U. M.; Khusnutdinov, R. I. Z. Obshch. Khim. 1975, 45, 1322. (12) Singer, H.; Umbach, W.; Dohr, M. Synthesis 1971, 265. (13) Bönnemann, H.; Grard, C.; Kopp, W.; Pump, W.; Tanaka, K.; Wilke, G. Angew. Chem., Int. Ed. Engl. 1973, 12, 964. (b) Bönnemann, H.; Grard, C.; Kopp, W.; Wilke, G. Pure Appl. Chem. 1971, 6, 265. (14) Feldman, K. S.; Grega, K. C. J. Organomet. Chem. 1990, 381, 251. (15) Mitsudo, T.; Zhang, S.-W.; Kondo, T.; Watanabe, Y. Tetrahedron Lett. 1992, 33, 341. (16) The general mechanisms for olefin dimerization are summarized in ref 4. (17) Bennett, M. A.; Wang, X.-Q. J. Organomet. Chem. 1992, 428, C17. (18) Hirano, M.; Sakate, Y.; Inoue, H.; Arai, Y.; Komine, N.; Komiya, S.; Wang, X.-Q.; Bennett, M. A. J. Organomet. Chem. 2012, 708−709, 46. (19) Hirano, M.; Shibasaki, T.; Komiya, S.; Bennett, M. A. Organometallics 2002, 21, 5738. (20) Funaioli, T.; Marchetti, F.; Fachinetti, G. Angew. Chem., Int. Ed. 2002, 41, 3905.

Table 3. Crystallographic and Refinement Details for 3aePPh3, 3ca, and 3ea 3aePPh3 formula fw cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z temp (K) cryst size (mm) color F(000) μ (mm−1) absorp corr radiation diffractometer measurement method reflns (total) params goodness of fit R (Rw)a a

3ca

3ea

C35H42NOPRu 624.77 triclinic P1̅(No. 2) 10.199(2) 10.922(3) 13.664(4) 82.687(6) 87.793(8) 76.674(8) 1468.9(6) 2 200.0 0.32 × 0.11 × 0.08 pale yellow 652.00 0.617 numerical Mo Kα (λ = 0.71075 Å) Rigaku AFC7RMercury II ω

C20H31NO2Ru 418.54 triclinic P1̅(No. 2) 8.464(3) 10.961(3) 11.182(3) 84.032(10) 86.657(11) 69.827(6) 968.2(5) 2 200.0 0.27 × 0.06 × 0.03 yellow 436.00 0.821 numerical Mo Kα (λ = 0.71075 Å) Rigaku AFC7RMercury II ω

4223(3) 8 200.0 0.14 × 0.07 × 0.07 pale yellow 1872.00 0.758 numerical Mo Kα (λ = 0.71075 Å) Rigaku AFC7RMercury II ω

6635 489 1.053 0.0302(0.0800)

4370 212 1.227 0.0401(0.1183)

9669 469 1.012 0.0962(0.2624)

C22H35NO2Ru 446.59 monoclinic P21/c(No. 14) 14.246(5) 14.126(5) 21.015(8) 93.084(5)

R = ∑[|Fo| − |Fc|]/∑|Fo|. Rw = [∑w(|Fo|2 − |Fc|2)2/∑w|Fo]2]1/2.

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Stoichiometric and Catalytic Cross Dimerization between Conjugated

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