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New naphthalene complexes of Ru(0) with various Ru(η6-naphthalene)(cyclic diene) (3) ligands catalyze linear cross-dimerization between conjugated di...
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Regio- and Enantioselective Linear Cross-Dimerizations between Conjugated Dienes and Acrylates Catalyzed by New Ru(0) Complexes Yuki Hiroi,† Nobuyuki Komine,†,‡ Sanshiro Komiya,† and Masafumi Hirano*,†,‡ †

Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588, Japan ‡ Japan Science and Technology Agency (JST), ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan S Supporting Information *

ABSTRACT: New naphthalene complexes of Ru(0) with various Ru(η6naphthalene)(cyclic diene) (3) ligands catalyze linear cross-dimerization between conjugated dienes and acrylates. One of the noteworthy catalysts is the dibenzocyclooctatetraene complex 3d, which shows high catalytic activity for the cross-dimerization between 1,3-pentadiene and methyl acrylate to give the cross-dimers in 99% yield (branch/linear = 77/23) within 1 h at 50 °C with 1 mol % catalyst loading. When Ru(η6-naphthalene)[(−)-Ph-bod*] (3f) was used as the catalyst, treatment of 2,4-dimethylhexa-2,4-diene with tert-butyl acrylate produced the chiral cross-dimer in 44% yield with 49% ee. This is the first example of enantioselective cross-dimerization between conjugated dienes and substituted alkenes.

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INTRODUCTION Catalytic cross-dimerization between substituted alkenes is a unique, powerful, and environmentally benign C−C bond formation process with high atom efficiency.1 The linear crossdimerization between a conjugated diene and substituted alkene is limited, and most of the pioneering examples are catalyzed by Ziegler-type catalysts/hydrido species or by an in situ reduction system of high valent metal compounds.2 Among these coupling processes, one of the ultimate goals is the enantioselective reaction. Although the related enantioselective hydrovinylation1,3 is already reported as an extension of π-allyl chemistry, ethylene must be used as one of the coupling partners. We previously reported cross-dimerizations between conjugated alkene and alkene4 or conjugated diene and alkene5 catalyzed by Ru(naphthalene)(cod) (3a; cod = 1,5-cyclooctadiene) by an oxidative coupling mechanism.6,7 In these reactions, the (η6-naphthalene)ruthenium(0) complex 3a releases the naphthalene ligand to generate [Ru(cod)], a putative coordinatively unsaturated species having 6e vacant coordination sites, to which a conjugated compound and a substituted alkene are expected to coordinate in κ4- and η2fashions, respectively. Therefore, the activity and selectivity of the subsequent reactions on the related [Ru(cyclic diene)] would be controlled by the ancillary cyclic diene ligand. Because this reaction is disturbed by the addition of tertiary phosphines,7b we need to use chiral diene ligands if we extend this reaction to the enantioselective reaction. Hayashi, and shortly later Carreira, developed catalytic asymmetric syntheses by use of chiral diene ligands,8 and nowadays, they are powerful chiral scaffolds for catalytic asymmetric synthesis. However, © XXXX American Chemical Society

almost all of these catalyses are promoted by group 9 metal complexes and are limited to either conjugate addition of arylborane or kinetic resolutions.9,10 Recently, we synthesized a new Ru(0) complex having a bicyclononadiene ligand Ru(naphthalene)((S,S)-Me-bnd) (3bb; bnd = bicyclononadiene) and achieved the enantioselective linear coupling reaction between methyl methacrylate and 2,5-dihydrofuran by 3bb, which is the first example of enantioselective cross-dimerization between substituted alkenes.4a Herein we disclose the synthesis of new ruthenium(0) complexes having various bicyclic dienes or phosphaalkene ligands and their catalytic activities toward cross-dimerizations of conjugated dienes with substituted alkenes. The enantioselective cross-dimerization between conjugated diene and substituted alkene is also described.

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RESULTS AND DISCUSSION Synthesis of (η6-Naphthalene)ruthenium(0) Complexes. The optimized synthetic method for the cod complex 3a was established by Bennett et al.,11 and we achieved the synthesis of the bnd analogues 3ba, 3bb, and 3bc.4a In order to survey the suitable ligand for cross-dimerization, we newly synthesized a series of (η6-naphthalene)ruthenium(0) complexes 3 from Ru(acac)3 through Ru(acac)2(L2) (2) using dibenzo[a,e]cyclooctatetraene (1d; dbcot), bicyclooctadiene (1e; bod), (−)-(1S,4R,8R)-8-methoxy-1,8-dimethyl-2Received: September 9, 2014

A

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phenylbicyclo[2.2.2]octa-2,5-diene (1f; Ph-bod*), and 5diphenylphosphonyl-5H-dibenzocycloheptene (1g; troppPh) as spectator ligands (Scheme 1). Scheme 1

Figure 2. Molecular structure of 3d. All hydrogen atoms and molecule of cocrystallized solvent are omitted for clarity. Ellipsoids represent 50% probability.

and the overall structure is very similar to the cod complex 3a.11b In order to understand the effect of the ancillary cyclic diene ligand on the electronic properties, some naphthalene complexes 3 were converted into the corresponding carbonyl complexes 4 (Scheme 2).14 The stretching vibration of the Scheme 2 The preparation of Ru(acac)2(dbcot) (2d) was achieved by the reaction of Ru(acac)3 with dbcot and Zn powder in refluxing aqueous THF, during which time the red solution turned pale yellow. After the workup procedures involving recrystallization from THF/hexane, 2d was isolated as yellow crystals in 67% yield. The molecular structures of the newly prepared analogues 2e−g are illustrated in Figure 1. The overall molecular structures of 2e−g are not so different from each other and from the cod analogue 2a.12,13 The Ru(η6-naphthalene)(dbcot) (3d) complex was prepared by the reduction of 2d with sodium/naphthalene in THF solution at −78 °C to rt in 24% yield after recrystallization from THF/hexane. Other naphthalene complexes 3 were also synthesized by the same method from the corresponding complex 2 in moderate isolated yields. Compounds 3d−g were characterized by 1H NMR, 1H−1H COSY, 13C NMR, and 13 C−1H HETCOR spectra, IR spectra, and elemental analysis, and 3d was also characterized by X-ray analysis. The molecular structure of 3d is shown in Figure 2. No special differences are there for the bond distances [2.133(3)− 2.144(4) Å] among coordinating carbons and the Ru(0) center,

carbonyl group by IR suggests that the bnd ligand (1960 cm−1) is close to the cod (1964 cm−1), while the band for the oxa-bnd (1976 cm−1) and dbcot complex (1984 cm−1) shifted to higher frequency. These facts clearly suggest that the oxa-bnd and dbcot are more electron-withdrawing ligands than cod. Cross-Dimerization of Pentadiene with Methyl Acrylate Catalyzed by Various Naphthalene Ru(0) Complexes. In order to understand the catalytic properties of

Figure 1. Molecular structures of 2e, 2f, and 2g. All hydrogen atoms are omitted for clarity. Ellipsoids represent 50% probability. B

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(5Z)-octa-2,5-dienoate (5b) in moderate yield (entry 1). The bnd complexes 3b,c showed low to moderate catalytic activity (entries 2−5). In these reactions, cross-trimerization by the reaction between the cross-dimers 5 and methyl acrylate was observed in 3−13% yields under the reaction conditions, and this type of co-oligomerization is the main side reaction to suppress the yield of cross-dimers. To our delight, the dbcot complex 3d produced 5 in quantitative yield only by 1 mol % catalyst loading (entry 6). Complex 3d also showed high catalytic activity of the cross-dimerization even with 0.5 mol % catalyst loading (entry 7). On the other hand, the catalytic activity diminished for the bod complexes 3e and 3f probably due to instability under the reaction conditions (entries 8 and 9). The phosphaalkene complex 3g also showed good catalytic activity comparable to that of 3d (entry 10). From these results, one of the features of this catalytic system is the high branch selectivity.15 We have reported that this regioselectivity comes from the electrophilic attack of the coordinating alkene to the coordinating 1,3-diene. Another interesting feature of the reaction is the Z-stereochemistry at the 5-position in both 5a and 5b. This suggests involvement of the cisoid coordination of 1,3-pentadiene at the C−C bond forming step (vide infra). Cross-Dimerization between Conjugated Dienes and Acrylates. The scope of conjugated dienes in the crossdimerization between conjugated dienes and methyl acrylate was investigated under the optimized conditions using dbcot complex 3d (1 mol %) in toluene at 50 °C (Table 2).16 All of the mono- to tetrasubstituted butadienes gave the cross-dimers in high yield (79−97%). In the case of isoprene, it showed high reactivity but the regioselectivity was poor (entry 1). The reaction of 2,4-hexadiene dominantly produced an expected product 7a, but an unexpected minor isomer 7a′ also formed, probably from 1,3-hexadiene through the isomerization of the substrate (entry 2). In spite of higher steric hindrance, 3methyl-1,3-pentadiene mainly produced branched cross-dimer 9a (entry 4). Interestingly, selectivity was drastically changed to

these naphthalene complexes for the conjugated diene, we screened complexes 3 for the cross-dimerization of 1,3pentadiene with methyl acrylate as an example (Table 1). Table 1. Cross-Dimerization of Pentadiene with Methyl Acrylatea,b

a Yields are estimated on the basis of pentadiene. determined by GC. cRacemic products were observed.

b

Yields were

These cross-dimer products contain two regioisomers, the branch and linear isomers. Because these isomers were very difficult to separate, they were characterized by 1H NMR, 1 H−1H COSY, 13C{1H} NMR, and GC-MS. The cod complex 3a catalyzes the cross-dimerization between 1,3-pentadiene and methyl acrylate to give the branched product methyl (5Z)-4-methylhepta-2,5-dienoate (5a) as a major product along with a small amount of methyl

Table 2. Cross-Dimerization between Conjugated Dienes and Acrylates

C

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the linear product 10b when 2,3-dimethyl-1,3-pentadiene was used as a substrate (entry 5). Furthermore, bulky tert-butyl acrylate was also reacted with dimethylhexadiene to give the cross-dimer in 79% yield (entry 6). Enantioselective Cross-Dimerization between Diene and Acrylate. Since these branched products have a chiral center at the 4-position, we screened these reactions by the chiral catalysts (Scheme 3). These chiral cross-dimers were Scheme 3. Enantioselective Linear Cross-Dimerization between Conjugated Dienes and Acrylates

Figure 3.

Scheme 4. Proposed Catalytic Cycle

characterized by chiral stationary phase gas chromatography (CSP GC). Because we could not separate the chiral peaks in the CSP GC for t-butyl and 1-adamantyl analogues, we measured them after ester exchange reaction to the methyl analogue. In Scheme 3, only ee values for the E-isomers were noted because ee values for the minor Z analogues were not clear. Since these branched products have a chiral center at the 4position, we screened these reactions by use of the chiral catalysts (S,S)-3bb and (S,R,R)-3f. Because application to an enantioselective reaction by simple 1,3-pentadiene is difficult to apply (see Table 1, entry 9), we use multisubstituted butadiene as a coupling partner in order to increase the prochiral face selectivity of the diene. The reaction of 2,3-dimethylpentadiene produced a small amount of desired 10a with small enantiomeric excess. As a consequence, enantioselective linear cross-dimerization between 3,4-dimethyl-2,4-hexadiene and methyl acrylate was achieved by chiral catalyst 3f to give a sole cross-dimer 11a in 31% yield with 36% ee. The asymmetric yield was improved by use of a bulky ester (R = t-Bu, 58% ee), which suggests the enantioselectivity is determined at the coordination step of substituted alkenes by face- and orientation-selective coordination of acrylate to avoid steric repulsion between the ester and ligand/conjugated diene (Figure 3). Unfortunately, the use of bulky adamantyl acrylate decreased product yield without increasing enantioselectivity. By use of an excess amount of conjugated diene, the yield was slightly improved. Interestingly, the enantiomeric excess was increased in the case of methyl acrylate and decreased in the case of t-Bu acrylate. Mechanism. All these experimental data of the present cross-dimerization are consistent with the catalytic cycle shown in Scheme 4 as a representative of reaction.7 The crossdimerization between 2,3-dimethyl-2,4-hexadiene and methyl

acrylate is illustrated as a typical example. First, this reaction is considered to proceed by the oxidative coupling mechanism that gives a ruthenacyclopentane the same as in the case of the Ru(naphthalene)(cod) catalyst. The active species [Ru(L2)] is formally generated by liberation of naphthalene, a 6-electron ligand, from Ru(naphthalene)(L2) to which dimethylhexadiene and methyl acrylate coordinate as 4e and 2e donors, respectively, to the Ru(0) center. This is the origin of the substrate selectivity in this reaction. We have observed selective formation of the Z configuration at the 5-position in all of the cross-dimers. This stereochemistry arises from the cisoid conformation of the coordinating diene. The absolute configuration is determined by face- and orientation-selective coordination of acrylate to avoid steric repulsion between the ester and ligand/conjugated diene. The oxidative coupling reaction forms the ruthenacyclopentane, followed by subsequent β-hydride elimination and reductive elimination to release the final coupling product.

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CONCLUSION In summary, we have reported preparations of a series of new Ru(η6-naphthalene)(η4-cyclic diene ligand) complexes and their use for catalytic linear cross-dimerization of conjugated dienes with acrylates. The dibenzocyclooctatetraene complex showed high activity. When we employed a chiral diene complex of Ru(0) 3, the first enantioselective crossdimerization between conjugated dienes and substituted alkenes was achieved. D

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J = 6.9 Hz, 2H, CHMe). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.53, 14.07, 119.26, 137.06. Synthesis of Bicyclo[2.2.2]octa-2,5-diene (1e). The suspension of bicyclo[2.2.2]octane-2,5-dione (1.0110 g, 7.3174 mmol) and TsNHNH2 (2.7441 g, 14.735 mmol) in EtOH (10 mL) was heated at reflux for 4 h. The mixture was cooled to rt to fully precipitate the product. The white precipitate was collected by suction filtration and washed with EtOH (1 mL) and hexane (2 mL) and dried under vacuum to give bicyclo[2.2.2]octane-2,5-dione bistosylhydrazone (3.2694 g, 6.8782 mmol, 94%) as a white powder. 1H NMR (400 MHz, rt, DMSO-d6): δ 1.55 (m, 4H, −CH2−), 2.23 (d, J = 18.4 Hz, 2H, −CH2−), 2.37 (m, 8H, −Me and −CH2−), 2.49 (overlapped with DMSO, 2H, >CH−), 7.37 (d, J = 8.0 Hz, 4H, Ar), 7.69 (d, J = 8.6 Hz, 4H, Ar), 9.98 (br s, 2H, −NH−). A mixture of iPr2NH (4.2 mL) and TMEDA (10 mL) was cooled to 0 °C, and then BuLi (2.6 M in hexane, 5.8 mL, 15.1 mmol) was added dropwise carefully followed by portionwise addition of the bistosylhydrazone (1.4407 g, 3.0356 mmol) at 0 °C. The mixture was allowed to warm to rt and stirred overnight. The reaction mixture was cooled to 0 °C and quenched by aqueous NH4Cl (10 mL). The aqueous layer was extracted with pentane (10 mL × 3). The combined organic layer was carefully concentrated by an evaporator to give a pale yellow oil. Silica gel column chromatography of the residue (eluted with pentane) gave 1e (91.4 mg, 0.8797 mmol, 29%) as a colorless oil. 1H NMR (400 MHz, rt, CDCl3): δ 1.24 (m, 4H, −CH2−), 3.60 (m, 2H, bridgehead), 6.28 (m, 4H, CH−). General Procedure for Synthesis of Ru(acac)2(L2) (2). The reaction mixture of activated Zn dust (10 equiv), Ru(acac)3 (1 equiv), and ligand (1.05 equiv) in aqueous THF (THF (10 mL/1 mmol of Ru) and water (2% v/v)) was vigorously stirred at rt for a few minutes and then refluxed for 4 h. The burgundy solution turned pale yellow. After the mixture was cooled to rt, the Zn dust was filtered off by an alumina short column (after the reaction, the mixture can be treated under air). The mixture was concentrated by an evaporator to dryness to a give crude product as a yellow powder. The crude product was purified by recrystallization. Ru(acac)2(dibenzo[a,e]cyclooctatetraene) (2d). Complex 2d was synthesized according to the general procedure from Ru(acac)3 (1.0335 g, 2.5943 mmol) and 1d (554.8 mg, 2.716 mmol). Compound 2d (881.5 mg, 1.751 mmol, 67%) was obtained as pale yellow needles from hot THF and hexane. 1H NMR (400 MHz, rt, CDCl3): δ 1.87 (s, 6H, acac-Me), 1.96 (s, 6H, acac-Me), 4.93 (d, J = 9.2 Hz, 2H,  CH−), 5.11 (d, J = 9.2 Hz, 2H, CH−), 5.35 (br s, 2H, acac-γ), 6.86−6.92 (m, 6H, aromatics), 7.01 (m, 2H, aromatics). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 27.45, 28.16, 91.03, 94.99, 98.59, 125.48, 125.54, 126.80, 128.08, 143.98, 144.08, 186.57, 187.01. Anal. Calcd for RuC26H26O4: C, 62.02; H, 5.20. Found: C, 61.89; H, 5.19. Ru(acac)2(bicyclo[2.2.2]octa-2,5-diene) (2e). Complex 2e was synthesized according to the general procedure from Ru(acac)3 (331.1 mg, 0.8311 mmol) and 1e (91.4 mg, 0.8797 mmol). The title compound (207.1 mg, 0.5108 mmol, 61%) was obtained as yellow needles from hot acetone. 1H NMR (400 MHz, rt, CDCl3): δ 1.24 (m, 4H, −CH2−), 1.87 (s, 6H, acac-Me), 2.18 (s, 6H, acac-Me), 3.62 (m, 2H, bridgehead), 4.02 (t, J = 6.3 Hz, 2H, CH−), 4.21 (t, J = 6.3 Hz, 2H, CH−), 5.31 (br s, J = 8.6 Hz, 4H, Ar), 5.32 (br s, 2H, acac-γ). 13 C{1H} NMR (100.5 MHz, rt, CDCl3): δ 26.10, 27.50, 28.07, 39.06, 73.01, 75.26, 98.77, 186.42, 186.86. Ru(acac)2((−)-(1S,4R,8R)-8-methoxy-1,8-dimethyl-2phenylbicyclo[2.2.2]octa-2,5-diene) (2f). Complex 2f was synthesized according to the general procedure from Ru(acac)3 (481.5 mg, 1.209 mmol) and 1f (301.9 mg, 1.255 mmol). The title compounds of Λ-2f (301.5 mg, 0.5587 mmol, 46%) and Δ-2f (95.8 mg, 0.118 mmol, 15%) as secondary crystals were obtained as orange plates from pentane (diastereomeric ratio of the crude product was observed to be Λ-2f/Δ2f = 61:39). Λ-2f: 1H NMR (400 MHz, rt, CDCl3): δ 0.89 (d, J = 14.0 Hz, 1H, −CH2−), 1.20 (s, 3H, −Me), 1.37 (s, 3H, −Me), 1.42 (d, J = 14.0 Hz, 1H, −CH2−), 1.54 (s, 3H, acac-Me), 1.89 (s, 3H, acac-Me), 2.14 (s, 3H, acac-Me), 2.22 (s, 3H, acac-Me), 3.24 (s, 3H, −OMe), 3.75 (t, J = 6.3 Hz, 1H, >CH−), 3.85 (d, J = 5.7 Hz, 1H, CH−), 3.92 (d, J = 5.7 Hz, 1H, CH−), 4.30 (t, J = 6.3 Hz, 1H, CH−),

EXPERIMENTAL SECTION

General Considerations. All procedures described in this paper were carried out under a nitrogen or argon atmosphere by use of Schlenk and vacuum line techniques. Benzene, toluene, hexane, THF, and Et2O were dried and purified using a solvent purification system. Acetone was dried over Drierite and distilled under nitrogen. Benzened6 was dried over a sodium wire and stored under vacuum, and it was used by vacuum distillation prior to use. Chloroform-d1 was dried over P2O5 and stored under vacuum. Methyl acrylate and tert-butyl acrylate were dried over CaCl2 and distilled over CaH2 under nitrogen. 1,3Pentadiene, 2,4-hexadiene, 2,3-dimethylbutadiene, and 3-methyl-1,3pentadiene were dried over CaH2 and purified by valve-to-valve distillation under reduced pressure. Cyclic diene ligands 1d,17 1f,8b 1g,18 and adamantyl acrylate19 were prepared according to the literature methods. Other coupling partners (2,3-dimethyl-1,3pentadiene and 3,4-dimethyl-2,3-hexadiene) and ligand (bicyclo[2.2.2]octa-2,5-diene (1e)) were synthesized (vide infra) and used after degassed by freeze−pump−thaw cycles. Ru(η 6 naphthalene)(η4-cod) (3a) was prepared according to the reported method.11c Complexes 2ba−2c and 3ba−3c were synthesized according to our previous reported procedures.4a NMR spectra were recorded on FT NMR spectrometers (399.8 MHz for 1H) with chemical shifts reported in δ parts per million downfield from TMS (the solvent peak as an internal standard) for 1H. IR spectra were recorded on a FT/IR spectrometer using KBr disks. GC analysis was performed on a GC chromatogram with an FID detector equipped with a capillary column (PEG column, 0.25 mmf × 30 m). General GC conditions: injector, 220 °C; detector, 220 °C; initial temp, 50 °C; initial time, 5 min; program rate, 10 °C/min; final temp, 220 °C. GCMS spectra were obtained on a GC chromatogram equipped with a capillary column (PEG column, 0.25 mmf × 30 m). Chiral stationary phase gas chromatography (CSP GC) analyses of the cross-dimers 5a, 10a, and 11a were accomplished using a GC chromatogram equipped with a chiral capillary column (Rt-γDEXsa, 0.25 mmf × 30 m). The elemental analyses were performed on a CHN analyzer. Synthesis of 2,3-Dimethyl-1,3-pentadiene. The reaction mixture of triphenylmethylphosphonium iodide (39.8 g, 98.4 mmol) in Et2O (200 mL) was cooled to −40 °C, and then n-BuLi/hexane (2.53 M, 38.5 mL, 15.2 mmol) was added dropwise. The yellow solution was left at rt for 1 h, cooled to 0 °C, and then a solution of 3methyl-3-pentene-2-one (10.3 mL, 91.8 mmol) in ether (40 mL) was added dropwise. The reaction mixture was stirred at rt for 2 h. The reaction was quenched by addition of aqueous NH4Cl (20 mL) and water (20 mL). The reaction mixture was separated, and the aqueous phase was extracted with Et2O (20 mL × 2). The combined organic phase was dried over MgSO4 and carefully concentrated by an evaporator. The crude product was purified by a silica gel short column (eluted with pentane) to afford (E)-2,3-dimethyl-1,3pentadiene (1.58 g, 16.4 mmol, 18% yield as a pentane solution). 1 H NMR (400 MHz, rt, CDCl3): δ 1.71 (d, J = 6.9 Hz, 3H, −Me), 1.78 (s, 3H, −Me), 1.89 (s, 3H, −Me), 4.85 (s, 1H, CH2), 4.95 (s, 1H, CH2), 5.68 (q, J = 6.9 Hz, 1H, CHMe). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.24, 14.17, 20.83, 110.50, 122.12, 135.65, 144.59. Synthesis of 3,4-Dimethyl-2,3-hexadiene. The reaction mixture of triphenylethylphosphonium bromide (14.2 g, 38.4 mmol) in Et2O (75 mL) was cooled to 0 °C, and then n-BuLi/hexane (2.10 M, 20.0 mL, 42.0 mmol) was added dropwise. The orange solution was stirred at 0 °C for 1 h, and then a solution of 3-methyl-3-pentene2-one (4.2 mL, 37.4 mmol) in ether (10 mL) was added dropwise. The reaction mixture was stirred at rt overnight. The reaction was quenched by addition of aqueous NH4Cl (10 mL) and water (10 mL). The reaction mixture was separated, and the aqueous phase was extracted with pentane (10 mL × 2). The combined organic phase was dried over Na2SO4 and carefully concentrated by an evaporator. The crude product was purified by a silica gel short column (eluted with pentane) to afford (E,E)-3,4-dimethyl-2,4-hexadiene (1.11 g, 10.0 mmol, 27% yield as a pentane solution). 1H NMR (400 MHz, rt, CDCl3): δ 1.69 (d, J = 6.9 Hz, 6H, −Me), 1.75 (s, 6H, −Me), 5.56 (q, E

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Organometallics

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5.15 (s, 1H, acac-γ), 5.41 (s, 1H, acac-γ), 7.16 (m, 3H, −Ph), 7.72 (m, 2H, −Ph). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 21.51, 22.08, 26.74, 27.23, 27.36, 27.89, 49.38, 50.34, 50.50, 50.82, 70.34, 70.97, 78.73, 82.04, 85.23, 99.11, 99.24, 126.42, 126.77, 130.62, 138.70, 185.95, 186.26, 187.14, 187.21. Δ-2f: 1H NMR (400 MHz, rt, CDCl3): δ 1.00 (d, J = 13.8 Hz, 1H, −CH2−), 1.19 (s, 3H,−Me), 1.43 (d, J = 13.8 Hz, 1H, −CH2−), 1.67 (s, 3H, −Me), 1.69 (s, 3H, acac-Me), 1.84 (s, 3H, acac-Me), 2.18 (s, 3H, acac-Me), 2.19 (s, 3H, acac-Me), 3.22 (s, 3H, −OMe), 3.79 (t, J = 4.0 Hz, 1H, >CH−), 4.09 (dd, J = 1.1, 6.3 Hz, 1H, CH−), 4.13 (t, J = 5.7 Hz, 1H, CH−), 4.48 (d, J = 5.7 Hz, 1H, CH−), 5.26 (s, 1H, acac-γ), 5.30 (s, 1H, acac-γ), 7.02−7.11 (m, 3H, −Ph), 7.19−7.22 (m, 2H, −Ph). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 21.10, 22.46, 26.93, 27.23, 27.71, 28.10, 49.41, 50.04, 50.34, 51.42, 69.99, 74.26, 79.70, 81.82, 88.09, 98.38, 99.43, 126.41, 127.02, 129.40, 138.63, 186.34, 186.36, 186.62, 187.07. Anal. Calcd for RuC27H34O5: C, 60.10; H, 6.35. Found: C, 59.62; H, 6.44. Ru(acac)2(5-diphenylphosphonyl-5H-dibenzocycloheptene) (2g). Complex 2g was synthesized according to the general procedure from Ru(acac)3 (1.2087 g, 3.0340 mmol) and 1g (1.1854 g, 3.1491 mmol). Compound 2g (1.6503 g, 2.4423 mmol, 80%) was obtained as orange plates from hot THF and hexane. 1H NMR (400 MHz, rt, CDCl3): δ 1.59 (s, 3H, −Me), 1.60 (s, 3H, −Me), 1.76 (s, 3H, −Me), 2.02 (s, 3H, −Me), 4.76 (s, 1H, acac-γ-H), 4.94 (d, J = 10.3 Hz, 1H, CH−), 5.04 (d, JP−H = 13.8 Hz, 1H, >CH−PPh2), 5.31 (s, 1H, acac-γ-H), 5.44 (d, J = 10.3 Hz, 1H, CH−), 6.08 (t, J = 8.0 Hz, 2H), 6.80 (m, 2H), 6.93 (m, 2H), 7.01 (m, 1H), 7.07 (m, 3H), 7.13 (m, 1H), 7.2−7.3 (m, 4H), 7.65 (d, J = 7.5 Hz, 1H), 7.83 (m, 2H). 31P{1H} NMR (161.8 MHz, rt, CDCl3): δ 89.52 (s). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 27.07, 28.18, 28.30 (d, JC−P = 5.7 Hz), 28.68, 50.87 (d, JC−P = 22.9 Hz), 80.89, 83.36, 97.81, 98.52, 125.69, 125.98, 126.04, 126.57, 126.73, 126.81, 126.92, 127.01, 128.51, 129.15 (d, JC−P = 6.7 Hz), 129.30 (d, JC−P = 5.8 Hz), 129.46, 129.84, 131.32, 132.40 (d, JC−P = 8.6 Hz), 134.64 (d, JC−P = 8.6 Hz), 134.75, 135.10, 135.66 (d, JC−P = 3.8 Hz), 136.02 (d, JC−P = 2.9 Hz), 140.78 (d, JC−P = 6.7 Hz), 141.50 (d, JC−P = 5.8 Hz), 184.24, 185.54, 186.29, 186.55. Anal. Calcd for RuC37H35O4P: C, 65.77; H, 5.22. Found: C, 65.78; H, 5.27. General Procedure for Synthesis of Ru(naphthalene)(L2) (3). A solution of sodium naphthalene, prepared from naphthalene (3 equiv) and cut sodium (10 equiv) in THF (10 mL/1 mmol of Ru) stirred over 3 h, was added dropwise to a solution of 2 (1 equiv) in THF (10 mL/1 mmol of Ru), which was stirred and cooled to −78 °C. The solution was stirred for 3 h at −78 °C and then allowed to warm to rt overnight with stirring. The solution was filtered through a neutral alumina column (eluted with THF). The collected deep orange solution was evaporated to dryness. Naphthalene was removed from the residual solid by sublimation at rt under high vacuum. The crude product was purified by recrystallization. Ru(naphthalene)(dibenzo[a,e]cyclooctatetraene) (3d). Complex 3d was synthesized according to the general procedure from 2d (974.2 mg, 1.935 mmol). Compound 3d was obtained as yellow needles from THF and hexane, and the crystal contains 1 equiv of THF (237.4 mg, 0.4695 mmol, 24%). 1H NMR (400 MHz, rt, C6D6): δ 4.30 (s, 4H,  CH−), 4.37 (m(AA′BB′), 2H, coord. naphthalene), 5.60 (m(AA′BB′), 2H, coord. naphthalene), 6.70 (m(AA′BB′), 4H, ligand), 6.88 (m(AA′BB′), 2H, uncoord. naphthalene), 6.91 (m(AA′BB′), 4H, ligand), 7.04 (m(AA′BB′), 2H, uncoord. naphthalene). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 66.57, 77.53, 93.85, 107.03, 124.98, 126.75, 127.16, 128.00 (overlapped with C6D6, determined from dept135), 148.93 Anal. Calcd for RuC26H20(C4H8O)0.25: C, 71.82; H, 4.91. Found: C, 71.53; H, 5.22. Ru(naphthalene)(bicyclo[2.2.2]octa-2,5-diene) (3e). Complex 3e was synthesized according to the general procedure from 2e (230.5 mg, 0.5685 mmol). Compound 3e (80.9 mg, 0.241 mmol, 42%) was obtained as brown powder from cold hexane. 1H NMR (400 MHz, rt, C6D6): δ 1.08 (m, 4H, −CH2−), 2.80 (dd, J = 2.3, 4.6 Hz, 4H,  CH−), 2.89 (m, 2H, >CH− (bod bridgehead)), 4.34 (dd(AA′BB′), J = 2.3, 4.0 Hz, 2H, coord. naphthalene), 5.68 (dd(AA′BB′), J = 2.3, 4.6 Hz, 2H, coord. naphthalene), 7.10−7.14 (m, 2H, uncoord. naphthalene), 7.16−7.20 (m, 2H, uncoord. naphthalene). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 28.43, 33.80, 38.17, 71.68, 87.69,

103.49, 125.34, 126.42. Anal. Calcd for RuC18H18: C, 64.46; H, 5.97. Found: C, 63.93; H, 5.62. Ru(naphthalene)((−)-(1S,4R,5R)-8-methoxy-1,8-dimethyl-2phenylbicyclo[2.2.2]octa-2,5-diene) (3f). Complex 3f was synthesized according to the general procedure from 2f (325.6 mg, 0.6039 mmol). Compound 3f (97.8 mg, 0.208 mmol, 33%) was obtained as an orange powder from pentane. 1H NMR (400 MHz, rt, C6D6): δ 0.60 (d, J = 13.2 Hz, 1H, −CH2−), 0.97 (s, 3H, −Me), 1.14 (s, 3H, −Me), 1.29 (d, J = 13.8 Hz, 1H, −CH2−), 2.53 (d, J = 5.2 Hz, 1H, >CH−), 2.61 (t, J = 5.7 Hz, 1H, CH−), 2.96 (t, J = 6.3 Hz, 1H, CH−), 3.03 (d, J = 6.3 Hz, 1H, overlapped, CH−), 3.04 (s, 3H, −OMe), 4.21 (d, J = 5.7 Hz, 1H, coord. naphthalene), 4.37 (d, J = 5.2 Hz, 1H, coord. naphthalene), 5.53 (t, J = 6.3 Hz, 1H, coord. naphthalene), 5.73 (t, J = 6.3 Hz, 1H, coord. naphthalene), 7.0−7.2 (m, 7H, uncoord. naphthalene and −Ph(m,p)), 7.53−7.57 (m, 2H, −Ph(o)). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 21.37, 23.79, 32.11, 32.57, 42.08, 46.61, 48.20, 48.81, 48.97, 56.13, 72.50, 73.23, 80.17, 89.22, 90.00, 104.24, 104.55, 125.53, 125.71,125.97, 127.13, 127.47, 128.28, 132.77, 144.72. Ru(naphthalene)(troppPh) (3g). Complex 3g was synthesized according to the general procedure from 2g (204.4 g, 0.3025 mmol). The deep red microneedles of compound 3g contain 0.25 equiv of THF as the crystallization solvent (44.9 mg, 0.0720 mmol, 24%). 1H NMR (400 MHz, rt, C6D6): δ 4.10 (s, 2H, CH−), 4.44 (d, JP−H = 13.2 Hz, 1H, >CH−PPh2), 4.63 (m, 2H, coord. naphthalene), 5.44 (m, 2H, coord. naphthalene), 6.61 (d, J = 6.9 Hz, 2H, aromatics), 6.72 (t, J = 7.5 Hz, 2H, aromatics), 6.78 (m, 2H, aromatics), 6.88 (m, 2H, aromatics), 6.92−7.06 (m, 12H, aromatics), 7.31 (d, J = 7.5 Hz, 2H, aromatics). 31P{1H} NMR (161.8 MHz, rt, C6D6): δ 105.64 (s). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 45.60, 52.69 (d, JC−P = 19.2 Hz), 76.01 (d, JC−P = 3.8 Hz), 88.50, 104.04, 123.10, 125.62, 125.85, 126.75, 127.53 (d, JC−P = 10.0 Hz, overlapped with C6D6, determined from dept135), 127.94 (overlapped with C6D6, determined from dept135 ), 128.78 (d, JC−P = 5.8 Hz), 128.96, 133.10 (d, JC−P = 10.5 Hz), 135.25 (d, JC−P = 3.8 Hz), 137.42 (d, JC−P = 36.4 Hz), 145.96 (d, JC−P = 10.5 Hz). Ge neral Procedure for Synthesis of Ru(η 4 -2,3dimethylbutadiene)(CO)(L2) (4). The reaction mixture of 3 (1 equiv) and 2,3-dimethylbutadiene (2 equiv) in THF/MeCN (10/1, (30 mL/1 mmol of Ru)) was stirred at rt for 2 h. The orange solution turned dark yellow. After the mixture was degassed by a freeze− pump−thaw cycle, excess CO (0.1 MPa) was introduced into the reaction vessel. After additional stirring for 2 h, the solution was evaporated to dryness under vacuum. The title compound was obtained as beige powder. Ru(2,3-dimethylbutadiene)(CO)(1,5-cyclooctadiene) (4a). Complex 4a was synthesized according to general procedure. The compound 4a (44.5 mg, 0.139 mmol, 94%) was obtained as a beige powder from 3a (50.0 mg, 0.148 mmol). This product was characterized by 1H NMR and compared with reported data.10 1H NMR (400 MHz, rt, C6D6): δ 0.16 (d, J = 2.3 Hz, 2H, CH2), 0.86 (d, J = 2.3 Hz, 2H, CH2), 1.80−1.85 (m, 2H, −CH2−), 1.83 (s, 6H, −Me), 1.95−2.00 (m, 2H, −CH2−), 2.32−2.38 (m, 2H, −CH2−), 2.45−2.55 (m, 2H, CH2−), 3.71−3.77 (m, 2H, CH−). Ru(2,3-dimethylbutadiene)(CO)(bicyclo[3.3.1]nona-2,6-diene) (4b). Complex 4b was synthesized according to the general procedure. The title compound (46.2 mg, 0.139 mmol, 96%) was obtained as beige powder from 3b (50.6 mg, 0.145 mmol). The compound was recrystallized from cold ether/hexane and characterized by spectral as well as X-ray crystallographic studies. 1H NMR (400 MHz, rt, C6D6): δ 0.13 (d, J = 2.9 Hz, 1H, CH2), 0.16 (d, J = 2.9 Hz, 1H, CH2), 0.74(d, J = 2.9 Hz, 1H, CH2), 1.07 (m, 2H, −CH2− (bridge)), 1.16 (d, J = 2.9 Hz, 1H, CH2), 1.55 (s, 3H, −Me), 1.84 (s, 4H, −Me, >CH− (bridgehead)), 2.05 (dm, J = 13.8 Hz, 1H, −CH2−), 2.14 (m, 1H, >CH− (bridgehead)), 2.41 (d, J = 13.2 Hz, 1H, −CH2−), 2.45 (dd, J = 8.0, 5.7 Hz, 1H, CH−), 2.54 (d, J = 13.8 Hz, 1H, −CH2−), 2.78 (br d, J = 8.6 Hz, 1H, CH−), 3.21 (dm, J = 14.3 Hz, 1H, −CH2−), 3.95 (br t, J = 6.9 Hz, 1H, CH−), 4.20 (d, J = 8.0 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 16.75, 17.84, 28.57, 29.20, 33.09, 33.53, 36.17, 43.82, 45.97, 76.04, 77.01, 81.93, F

dx.doi.org/10.1021/om500927z | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

82.36, 97.00, 99.84, 219.72. IR (KBr, cm−1): 3018(w), 3002(w), 2940(m), 2891(s), 2828(m), 1960(vs), 1463(w), 1435(w), 1374(m), 1330(m), 1177(w), 1026(w), 805(w), 488(s), 472(s), 454(m). Anal. Calcd for RuC16H22O: C, 57.99; H, 6.69. Found: C, 58.46; H, 7.00. Ru(2,3-dimethylbutadiene)(CO)(9-oxa-bicyclo[3.3.1]nona-2,6diene) (4c). Complex 4c was synthesized according to the general procedure. The title compound (42.7 mg, 0.128 mmol, 89%) was obtained as beige powder from 3c (50.5 mg, 0.144 mmol). 1H NMR (400 MHz, rt, C6D6): δ 0.09 (d, J = 2.3 Hz, 1H, CH2), 0.14(d, J = 2.3 Hz, 1H, CH2), 0.72 (d, J = 2.3 Hz, 1H, CH2), 1.12(d, J = 2.9 Hz, 1H, CH2), 1.38 (s, 3H, −Me), 1.59 (dt, J = 13.8, 2.9 Hz, 1H, −CH2−), 1.76 (s, 3H, −Me), 2.43 (dd, J = 8.6, 4.0 Hz, 1H, CH−), 2.67 (dt, J = 13.8, 2.9 Hz, 1H, −CH2−), 2.74 (br s, 1H, −CH2−), 2.77 (br s, 1H, CH−), 2.92 (d, J = 13.8 Hz, 1H, −CH2−), 3.91 (dd, J = 8.0, 4.6 Hz, 1H, CH−), 4.01 (m, 1H, >CH− (bridgehead)), 4.12 (dm, J = 8.6 Hz, 1H, CH−), 4.26 (m, 1H, >CH− (bridgehead)). 13 C{1H} NMR (100.5 MHz, rt, C6D6): δ 16.92, 17.70, 33.55, 34.27, 41.39, 43.11, 68.45, 68.82, 72.86, 75.09, 79.43, 80.75, 97.43, 99.73, 218.65. IR (KBr, cm−1): 3029(w), 3009(w), 2967(w), 2934(m), 2915(m), 2832(w), 1975(vs), 1428(m), 1376(m), 1354(m), 1316(m), 1250(m), 1185(s), 1053(s), 1032(m), 983(m), 822(s), 803(m), 786(s), 543(w), 527(w), 503(m), 483(s), 470(s), 459(s). Anal. Calcd for RuC15H20O2: C, 54.04; H, 6.05. Found: C, 54.28; H, 6.02. Ru(2,3-dimethylbutadiene)(CO)(dibenzo[a,e]cyclooctatetraene) (4d). Complex 4d was synthesized according to the general procedure. The title compound (45.3 mg, 0.109 mmol, 98%) was obtained as beige powder from 3d (50.3 mg, 0.111 mmol). The compound was recrystallized from cold ether/hexane and characterized by spectral as well as X-ray crystallographic studies. 1H NMR (400 MHz, rt, C6D6): δ 0.30 (d, J = 2.3 Hz, 2H, =CH2), 0.87 (d, J = 2.3 Hz, 2H, CH2), 1.77 (s, 6H, −Me), 3.05 (d, J = 9.2 Hz, 2H, CH−), 4.52 (d, J = 9.2 Hz, 2H, CH−), 6.58−6.66 (m, 4H, Ar), 6.79 (AA′BB′, 2H, −Ar), 6.96 (AA′BB′, 2H, −Ar). 13C{1H} NMR (100.5 MHz, rt, C6D6): δ 18.14, 36.92, 79.49, 84.39, 100.56, 125.82, 125.89, 126.88, 127.53, 144.78, 145.40, 218.74. IR (KBr, cm−1): 3066(w), 3011(w), 2964(w), 2910(w), 1984(vs), 1577(w), 1486(m), 1374(m), 1252(w), 1021(w), 984(w), 824(w), 751(s), 741(s), 667(m), 560(m), 520(m), 463(s). Anal. Calcd for RuC23H22O: C, 66.49; H, 5.34. Found: C, 66.02; H, 5.74. General Procedure for Catalytic Cross-Dimerization between Conjugated Dienes and Acrylates. Conjugated diene (20−100 equiv) and acrylate (22−110 equiv) in toluene (1 mL) were added into 3 (5−25 μmol, 1 equiv) in a Schlenk tube by the valve-tovalve distillation under reduced pressure. The mixture was stirred in the reaction conditions. Yield and product ratio were determined by GC analysis using biphenyl as an initial standard. Products were identified by various NMR spectra after purification by flash chromatography (silica gel: hexane/AcOEt = 20:1−10:1). (E)-1,3-Pentadiene with Methyl Acrylate. Reaction with 3a (1 mol %) at 50 °C for 1 h produced cross-dimers in 48% yield (E-5a:Z-5a:E5b:Z-5b = 83:1:14:2). Reaction with 3ba (5 mol %) at 70 °C for 2 h produced cross-dimers in 27% yield (E-5a:Z-5a:E-5b:Z-5b = 87:3:9:0) with 8% cross-trimers. Reaction with 3bb (5 mol %) at 70 °C for 2 h produced cross-dimers in 55% yield (E-5a:Z-5a:E-5b:Z-5b = 81:3:15:1) with 4% cross-trimers. Reaction with 3bc (5 mol %) at 70 °C for 8 h produced cross-dimers in 56% yield (E-5a:Z-5a:E-5b:Z5b = 82:4:14:0) with 3% cross-trimers. Reaction with 3c (5 mol %) at 70 °C for 1 h produced cross-dimers in 25% yield (E-5a:Z-5a:E-5b:Z5b = 82:3:14:1) with 13% cross-trimers. Reaction with 3d (1 mol %) at 50 °C for 1 h produced cross-dimers in 99% yield (E-5a:Z-5a:E5b:Z-5b = 72:5:19:4). Reaction with 3d (0.5 mol %) at 50 °C for 8 h produced cross-dimers in 90% yield (E-5a:Z-5a:E-5b:Z-5b = 71:6:12:11). Reaction with 3e (1 mol %) at 50 °C for 4 h produced cross-dimers in 6% yield (E-5a:Z-5a:E-5b:Z-5b = 75:7:18:0). Most of the reactant was not reacted. Reaction with 3f (5 mol %) at 70 °C for 4 h produced cross-dimers in 44% yield (E-5a:Z-5a:E-5b:Z-5b = 78:8:13:1). The 5a was the racemic product. Reaction with 3g (1 mol %) at 50 °C for 4 h produced cross-dimers in 83% yield (E-5a:Z-5a:E5b:Z-5b = 65:22:12:1). CSPl GC (Rt-γDEXsa, oven temp = 80 °C, linear velocity 50 cm/s): RT5a1 = 76.87 min, RT5a2 = 78.90 min.

(2E,5Z)-Methyl 4-Methylhepta-2,5-dienoate (E-5a). This product was characterized by 1H NMR and compared with reported data.2e 1H NMR (400 MHz, rt, CDCl3): δ 1.09 (d, J = 6.9 Hz, 3H, −Me), 1.59 (dd, J = 6.9, 2.3 Hz, 3H, −Me), 3.30 (sextet, J = 6.9 Hz, 1H, >CH−), 3.68 (s, 3H, −OMe), 5.18 (ddq, J = 10.9, 9.2, 1.7 Hz, 1H, CH−), 5.49 (ddq, J = 10.9, 6.9, 1.2 Hz, 1H, CH−), 5.75 (dd, J = 16.0, 1.2 Hz, 1H, CH−), 6.86 (dd, J = 16.0, 6.9 Hz, 1H, CH−). (2Z,5Z)-Methyl 4-Methylhepta-2,5-dienoate (Z-5a). 1H NMR (400 MHz, rt, CDCl3): δ 1.05 (d, J = 6.9 Hz, 3H, −Me), 1.64 (dd, J = 6.9, 1.7 Hz, 3H, −Me), 3.70 (s, 3H, −OMe), 4.57 (m, 1H, >CH−), 5.21 (ddq, J = 10.9, 9.2, 1.7 Hz, 1H, CH−), 5.42 (dq, J = 10.9, 6.9 Hz, 1H, CH−), 5.64 (d, J = 11.5 Hz, 1H, CH−), 6.00 (dd, J = 11.5, 10.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.15, 20.95, 31.09, 51.05, 116.54, 124.78, 133.09, 153.68, 166.69. GC-MS(EI): m/z = 154 (M+), 139 (M+ − Me), 123 (M+ − OMe), 95 (M+ − CO2Me). (2E,5Z)-Methyl Octa-2,5-dienoate (E-5b). This product was characterized by 1H NMR and compared with reported data.2e 1H NMR (400 MHz, rt, CDCl3): δ 0.94 (t, J = 7.5 Hz, 3H, −Me), 2.01 (quintet, J = 7.5 Hz, 2H, −CH2−), 2.91 (t, J = 6.9 Hz, 1H, >CH−), 3.69 (s, 3H, −OMe), 5.31 (dtt, J = 10.9, 6.9, 1.7 Hz, 1H, CH−), 5.49 (m, 1H, CH−), 5.81 (dt, J = 15.5, 1.7 Hz, 1H, CH−), 6.93 (dt, J = 15.5, 6.3 Hz, 1H, CH−). (2Z,5Z)-Methyl Octa-2,5-dienoate (Z-5b). 1H NMR (400 MHz, rt, CDCl3): δ 0.94 (t, J = 7.5 Hz, 3H, −Me), 2.06 (quintet, J = 7.5 Hz, 2H, −CH2−), 3.40 (t, J = 7.5 Hz, 2H, −CH2−), 3.69 (s, 3H, −OMe), 5.33 (dtt, J = 10.3, 7.5, 1.7 Hz, 1H, CH−), 5.44 (m, 1H, CH−), 5.75 (dt, J = 11.2, 2.3 Hz, 1H, CH−), 6.15 (dt, J = 11.2, 7.5 Hz, 1H,  CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 14.14, 20.61, 27.36, 51.05, 118.89, 125.05, 133.70, 148.66, 166.76. GC-MS(EI): m/z = 154 (M+), 139 (M+ − Me), 123 (M+ − OMe), 95 (M+ − CO2Me). Cross-Trimers. Cross-trimers were observed in some reactions. The two major cross-trimers were identified by various NMR spectra. All cross-trimers were composed of one pentadiene and two MA from GC-MS (m/z = 240 (M+)).

Dimethyl 4-Methyl-6-methylenenona-4-enedioate (5a′). 1H NMR (400 MHz, rt, CDCl3): δ 1.72 (s, 3H, −Me), 2.25−2.45 (m, 4H, −CH2−), 2.35 (br s, 4H, −CH2−), 3.63 (s, 3H, −OMe), 3.64 (s, 3H, −OMe), 4.75 (s, 1H, CH2), 4.97 (s, 1H, CH2), 5.55 (s, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 17.63, 32.59, 32.80, 32.95, 35.15, 51.50, 51.55, 113.69, 125.74, 137.36, 144.07, 173.60. GC-MS(EI): m/z = 240 (M+), 208 (M+ − MeOH), 176 (M+ − 2MeOH). Dimethyl 4,6-Dimethylnona-2,5-dienedioate (5a″). 1H NMR (400 MHz, rt, CDCl3): δ 1.06 (d, J = 6.9 Hz, 3H, −Me), 1.59 (s, 3H, −Me), 3.16 (sextet, J = 6.9 Hz, 1H, −CHCH−), 3.70 (s, 3H, −OMe), 5.28 (br.q, J = 6.3 Hz, 1H, CH−), 5.76 (dd, J = 15.5, 1.7 Hz, 1H,  CH−), 6.90 (dd(m), J = 15.5, 6.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 12.87, 16.70, 18.96, 36.41, 51.38, 119.40, 120.79, 136.10, 152.08, 167.31. GC-MS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − OMe). (2Z,5Z)-Methyl 4,5-Dimethylhepta-2,5-dienoate (Z-9a). 1H NMR (400 MHz, rt, CDCl3): δ 1.07 (d, J = 6.9 Hz, 3H, >CHMe), 1.61 (dm, J = 6.9 Hz, 3H, CHMe), 1.64 (m, 3H, −Me), 3.69 (s, 3H, −OMe), 4.71 (dq, J = 10.3, 6.9 Hz, 1H, >CHMe), 5.21 (q, J = 6.9 Hz, 1H,  CHMe), 5.68 (d, J = 11.5 Hz, 1H, CH−), 6.18 (dd, J = 11.5, 10.9 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 12.92, 18.64(2C), 33.08, 51.06, 117.37, 120.80, 137.08, 152.49, 166.56. GCMS(EI): m/z = 168 (M+), 153 (M+ − Me), 109 (M+ − CO2Me). (2E,5Z)-Methyl 6-Methylocta-2,5-dienoate (E-9b). 1H NMR (400 MHz, rt, CDCl3): δ 0.94 (t, J = 7.5 Hz, 3H, −CH2Me), 1.69 (m, 3H, −Me), 1.99 (q, J = 7.5 Hz, 2H, −CH2Me), 2.86 (t, J = 6.9 Hz, 2H, −CH2−), 3.69 (s, 3H, −OMe), 5.07 (t, J = 7.5 Hz, 1H, CH−), 5.79 (dt, J = 15.5, 1.7 Hz, 1H, CH−), 6.93 (dt, J = 15.5, 6.3 Hz, 1H,  CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 12.67, 22.83, 24.72, 30.43, 118.50, 120.56, 148.35 (other peaks could not be identified.). GC-MS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et). (2Z,5Z)-Methyl 6-Methylocta-2,5-dienoate (Z-9b). 1H NMR (400 MHz, rt, CDCl3): δ 0.95 (t, J = 7.5 Hz, 3H, −CH2Me), 1.67 (m, 3H, −Me), 2.04 (q, J = 7.5 Hz, 2H, −CH2Me), 3.35 (t, J = 7.5 Hz, 2H, −CH2−), 3.66 (s, 3H, −OMe), 5.09 (t, J = 7.5 Hz, 1H, CH−), 5.73 (dt, J = 11.5, 1.7 Hz, 1H, CH−), 6.14 (dt, J = 11.5, 7.5 Hz, 1H,  CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 24.85, 27.84, 118.44, 149.33 (other peaks could not be identified). GC-MS(EI): m/ z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et). (3E,5Z)-Methyl 6-Methylocta-3,5-dienoate (9c). 1H NMR (400 MHz, rt, CDCl3): δ 0.97 (t, J = 7.5 Hz, 3H, −CH2CH3), 1.73 (s, 3H, −Me), 2.13 (q, J = 8.0 Hz, 2H, −CH2CH3), 3.09 (d, J = 7.5 Hz, 2H, −CH2−), 3.65 (s, 3H, −OMe), 5.59 (dt, J = 14.9, 7.5 Hz, 1H,  CH−), 5.76 (overlapped with main product, 1H, CH−), 6.32 (br dd, J = 14.9, 10.9 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 12.89, 22.83, 25.26, 38.14, 51.79, 121.99, 123.77, 129.93, 141.04, 172.32. GC-MS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − OMe). 2,3-Dimethyl-1,3-pentadiene with Methyl Acrylate. Reaction with 3d (1 mol %) at 50 °C for 2 h produced cross-dimers in 100% yield (E-10a:Z-10a:E-10b:Z-10b:10c = 10:1:37:46:6). CSP GC (RtγDEXsa, oven temp = 120 °C, linear velocity 50 cm/s): RT10a1 = 16.35 min, RT10a2 = 17.31 min (ee = (Area10a2 − Area10a1)/(Area10a2 + Area10a1) × 100%). Reaction with (S,S)-3bb (10 mol %) at 70 °C for 4

CH−), 5.73 (dt, J = 11.5, 1.7 Hz, 1H, CH−), 6.14 (dt, J = 11.5, 7.5 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 17.80, 25.64, 28.24, 51.03, 118.49, 120.57, 133.89, 149.08, 166.84. GCMS(EI): m/z = 154 (M+), 139 (M+ − Me), 95 (M+ − CO2Me). (2E,5Z)-Methyl 5-Methylhepta-2,5-dienoate (E-6b). This product was characterized by 1H and 13C NMR and compared with reported data.2e 1H NMR (400 MHz, rt, CDCl3): δ 1.54 (d, J = 6.9 Hz, 3H,  CHMe), 1.65 (br s, 3H, −Me), 2.87 (d, J = 6.3 Hz, 2H, −CH2−), 3.69 (s, 3H, −OMe), 5.34 (dt, J = 6.5 Hz, 1H, CHMe), 5.79 (dt, J = 15.5, 1.7 Hz, 1H, CH−), 6.88 (dt, J = 15.5, 6.3 Hz, 1H, CH−). 13 C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.29, 23.43, 34.47, 51.34, 121.17, 121.69, 135.28, 146.50, 167.10. (2Z,5Z)-Methyl 5-Methylhepta-2,5-dienoate (Z-6b). 1H NMR (400 MHz, rt, CDCl3): δ 1.58 (d, J = 6.9 Hz, 3H, CHMe), 1.67 (br s, 3H, −Me), 3.40 (d, J = 7.5 Hz, 2H, −CH2−), 3.70 (s, 3H, −OMe), 5.28 (q, J = 6.9 Hz, 1H, CHMe), 5.80 (dt, J = 10.9, 1.7 Hz, 1H, CH−), 6.11 (dt, J = 11.5, 7.5 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.32, 23.35, 31.39, 51.03, 119.47, 120.90, 133.14, 147.97, 166.84. GC-MS(EI): m/z = 154 (M+), 139 (M+ − Me), 95 (M+ − CO2Me). (3E)-Methyl 6-Methylhepta-3,5-dienoate (6c). 1H NMR (400 MHz, rt, CDCl3): δ 1.71 (s, 3H, −Me), 1.73 (s, 3H, −Me), 3.09 (t, J = 7.5 Hz, 2H, −CH2−), 3.65 (s, 3H, −OMe), 5.58 (dt, J = 15.5, 6.9 Hz, 1H, CH−), 5.79 (d, J = 10.3 Hz, 1H, CH−), 6.30 (dd, J = 14.9, 10.9 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 18.22, 25.29, 38.13, 51.79, 121.80, 124.29, 130.37, 131.49, 172.31 GCMS(EI): m/z = 154 (M+), 139 (M+ − Me), 95 (M+ − CO2Me). 2,4-Hexadiene with Methyl Acrylate. Reaction with 3d (1 mol %) at 50 °C for 2 h produced cross-dimers in 97% yield (E-7a:Z-7a:E7a′:Z-7a′ = 62:26:7:5). Since cross-dimers could not be separated form the mixture, 7a and 7a′ were characterized spectroscopically. (2E,5Z)-Methyl 4-Methylocta-2,5-dienoate (E-7a). 1H NMR (400 MHz, rt, CDCl3): δ 0.94 (t, J = 8.0 Hz, 3H, −CH2Me), 1.10 (d, J = 6.9 Hz, 3H, >CHMe), 2.02 (ddq, J = 9.2, 1.7, 7.5 Hz, 2H, −CH2Me), 3.29 (sext., J = 7.5 Hz, 1H, >CHMe), 3.70 (s, 3H, −OMe), 5.13 (dd, J = 10.3, 9.2 Hz, 1H, CH−), 5.41 (dt, J = 10.3, 7.5 Hz, 1H, CH−), 5.76 (dd, J = 16.0, 1.7 Hz, 1H, CH−), 6.87 (dd, J = 15.4, 6.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 14.21, 20.05, 20.77, 34.41, 51.41, 118.87, 130.37, 132.62, 152.90, 167.37. GCMS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et), 125 (M+ − (C3H6 + H)), 109 (M+ − CO2Me). (2Z,5Z)-Methyl 4-Methylocta-2,5-dienoate (Z-7a). 1H NMR (400 MHz, rt, CDCl3): δ 0.92 (t, J = 7.5 Hz, 3H, −CH2Me), 1.04 (d, J = 6.9 Hz, 3H, >CHMe), 2.0−2.1 (m, 2H, −CH2Me), 3.70 (s, 3H, −OMe), 4.5−4.6 (m, 1H, >CHMe), 5.15 (overlapped with major product, 1H, CH−), 5.35 (dt, J = 10.3, 7.5 Hz, 1H, CH−), 5.63 (dd, J = 11.5, 1.2 Hz, 1H, CH−), 6.00 (dd, J = 11.5, 10.3 Hz, 1H, CH−). GCMS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et), 125 (M+ − (C3H6 + H)), 109 (M+ − CO2Me). (2E,5Z)-Methyl 4-Ethylhepta-2,5-dienoate (E-7a′). 1H NMR (400 MHz, rt, CDCl3): δ 0.8−0.9 (overlapped, 3H, −Me), 1.38 (m, 1H, −CH2−), 1.51 (m, 1H, −CH2−), 1.58 (dd, J = 6.9, 1.7 Hz, 3H,  CHMe), 3.07 (quintet, J = 8.0 Hz, 1H, >CHEt), 3.70 (s, 3H, −OMe), 5.17 (m, 1H, CH−), 5.56(dq, J = 10.9, 6.9 Hz, 1H, CH−), 5.77 ((dd) overlapped with major product, 1H, CH−), 6.83 (dd, J = 15.5, 6.9 Hz, 1H, CH−). GC-MS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et), 109 (M+ − CO2Me). (2Z,5Z)-Methyl 4-Ethylhepta-2,5-dienoate (Z-7a′). 1H NMR (400 MHz, rt, CDCl3): δ 0.8−0.9 (overlapped, 3H, −Me), 1.3−1.5 (overlapped, 2H, −CH2−), 1.64 (dd, J = 6.9, 1.7 Hz, 3H,  CHMe), 3.70 (s, 3H, −OMe), 4.4−4.5 (m, 1H, >CHEt), 5.16 (overlapped with major product, 1H, CH−), 5.50 (dq, J = 10.9, 6.9 Hz, 1H, CH−), 5.70 (d, J = 11.5 Hz, 1H, CH−), 5.95 (dd, J = 11.5, 10.3 Hz, 1H, CH−). GC-MS(EI): m/z = 168 (M+), 153 (M+ − Me), 139 (M+ − Et), 109 (M+ − CO2Me). Dimethylbutadiene with Methyl Acrylate. Reaction with 3d (1 mol %) at 50 °C for 4 h produced cross-dimers in 97% yield (E-8a:Z8a:8c = 50:45:5). (2E)-Methyl 5,6-Dimethylhepta-2,5-dienoate (E-8a). 1H NMR (400 MHz, rt, CDCl3): δ 1.62 (s, 6H, −Me), 1.65 (s, 3H, −Me), 2.88 H

dx.doi.org/10.1021/om500927z | Organometallics XXXX, XXX, XXX−XXX

Organometallics

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J = 1.2 Hz, 3H, −Me), 2.01 (m(overlapped with isomer), 1H, −CH2Me), 2.19 (dq, J = 14.3, 7.5 Hz, 1H, −CH2Me), 3.69 (s, 3H, −OMe), 4.78 (dq, J = 10.3, 6.9 Hz, 1H, >CH−), 5.64 (dd, J = 11.5, 1.2 Hz, 1H, CH−), 6.21 (dd, J = 11.5, 10.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 12.91, 13.19, 18.54, 19.24, 27.10, 34.36, 51.03, 116.67, 128.22, 132.28, 153.28, 166.65. GC-MS(EI): m/z = 196 (M+), 181 (M+ − Me), 167 (M+ − Et), 165 (M+ − OMe). 3,4-Dimethyl-2,4-hexadiene with tert-Butyl Acrylate. Reaction with 3d (1 mol %) at 50 °C for 2 h produced cross-dimers in 79% yield (E-11a′:Z-11a′ = 84:16). Reaction with (−)-3f (10 mol %) at 50 °C for 4 h produced cross-dimers in 31% yield (E-11a′:Z-11a′ = 94:6). Cross-dimer 11a′ was converted to 11a by an ester exchange reaction (11a′ was refluxed in MeOH with 1 equiv of TsOH for 2 h). After transformation, 11a was analyzed by CSP GC (58% ee). Reaction with (−)-3f (10 mol %) with twice the amount of diene at 50 °C for 4 h produced cross-dimers in 44% yield (E-11a′:Z-11a′ = 98:2). Crossdimer 11a′ was converted to 11a by an ester exchange reaction. After transformation, 11a was analyzed by CSP GC (49% ee). (2E,5Z)-tert-Butyl 4,5,6-Trimethylocta-2,5-dienoate (E-11a′). 1H NMR (400 MHz, rt, CDCl3): δ 0.93 (t, J = 7.5 Hz, 3H, −CH2Me), 1.08 (d, J = 6.9 Hz, 3H, −Me), 1.45 (s, 9H,-tBu), 1.46 (s, 3H, −Me), 1.62 (s, 3H, −Me), 2.02 (m, 2H, −CH2Me), 3.50 (quintet, J = 6.5 Hz, 1H, >CH−), 5.63 (dd, J = 15.5, 1.7 Hz, 1H, CH−), 6.80 (dd, J = 16.0, 5.7 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.39, 13.47, 17.31, 18.48, 27.08, 28.14, 37.82, 79.97, 121.29, 127.82, 131.80, 151.72, 166.44. GC-MS(EI): m/z = 238 (M+), 182 (M+ − C(Me)Et), 165 (M+ − OtBu). (2Z,5Z)-tert-Butyl 4,5,6-Trimethyl-octa-2,5-dienoate (Z-11a′). 1H NMR (400 MHz, rt, CDCl3): δ 1.05 (d, J = 6.9 Hz, 3H, −Me), 4.69 (dq, J = 10.3, 6.9 Hz, 1H, >CH−), 5.53 (d, J = 11.5 Hz, 1H, CH−), 6.07 (dd, J = 10.3, 11.5 Hz, 1H, CH−); other peaks were overlapped with major products peaks. 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 19.01, 34.27, 118.95, 165.82 other peaks could not identified. GC-MS(EI): m/z = 238 (M+), 182 (M+ − C(Me)Et), 165 (M+ − OtBu). 3,4-Dimethyl-2,4-hexadiene with Adamantyl Acrylate. Reaction with 3a (5 mol %) at 50 °C for 4 h produced cross-dimer 11a″ in 48% yield. Reaction with (−)-3f (10 mol %) at 50 °C for 4 h produced cross-dimer 11a″ in 18% yield. Cross-dimer 11a″ was converted to 11a by an ester exchange reaction (11a″ was refluxed in MeOH with 1 equiv of TsOH for 2 h). After transformation, 11a was analyzed by CSP GC (48% ee). (2E,5Z)-Adamantyl 4,5,6-Trimethylocta-2,5-dienoate (11a″). 1H NMR (400 MHz, rt, CDCl3): δ 0.93 (t, J = 7.5 Hz, 3H, −CH2Me), 1.08 (d, J = 7.5 Hz, 3H, −Me), 1.46 (s, 3H, −Me), 1.62 (s, 3H, −Me), 1.64 (br s, 6H, −Ad), 2.03 (m, 2H, −CH2Me), 2.12 (br s, 12H, −Ad), 3.50 (ddq, J = 6.9, 1.7, 7.5 Hz, 1H, >CH−), 5.63 (dd, J = 16.0, 1.7 Hz, 1H, CH−), 6.79 (dd, J = 15.5, 5.7 Hz, 1H, CH−). 13C{1H} NMR (400 MHz, rt, CDCl3): δ 13.41, 13.51, 17.33, 18.50, 27.09, 30.81 (3C), 36.22 (3C), 37.83, 41.36 (3C), 80.10, 121.44, 127.88, 131.78, 151.67, 166.15. GC-MS(EI): m/z = 316 (M+), 287 (M+ − Et), 164 (AdOH+), 135 (Ad+). Crystallographic Study. The single crystals were obtained by recrystallization from hot THF/hexane solution (2g), from hot acetone (2e), from pentane (2f), and from cold THF/hexane (3d). A selected crystal was mounted on the top of a glass capillary using Paraton-N oil. A Rigaku AFC-7R Mercury II diffractometer with graphite monochromated Mo Kα radiation (λ = 0.71075 Å) was used for data collection at 200.0 K. The collected data were solved by direct methods (SIR92), and refined by a full-matrix least-square procedure using SHELXL-97.20 All non-hydrogen atoms were refined with anisotropic displacement parameters.

h produced cross-dimers in 43% yield (E-10a:Z-10a:E-10b:Z-10b:10c = 40:2:30:2:26). Cross-dimer E-10a was observed in 17% yield with −10% ee. Reaction with (−)-3f (5 mol %) at 50 °C for 4 h produced cross-dimers in 72% yield (E-10a:Z-10a:E-10b:Z-10b:10c = 36:2:26:2:34). Cross-dimer E-10a was observed in 26% yield with 29% ee. (2E)-Methyl 4,5,6-Trimethylhepta-2,5-dienoate (E-10a). 1H NMR (400 MHz, rt, CDCl3): δ 1.08 (d, J = 6.9 Hz, 3H, −Me), 1.47 (br s, 3H, −Me), 1.63 (s(overlapped with a), 3H, −Me), 1.66 (br s, 3H, −Me), 3.52 (ddq, J = 1.7, 6.3, 6.9 Hz, 1H, >CH−), 3.69 (s(overlapped with a), 3H, −OMe), 5.71 (dd, J = 15.5, 1.7 Hz, 1H, CH−), 6.90 (dt, J = 15.5, 6.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.38, 16.77, 19.95, 20.94, 38.36, 51.37, 119.06, 126.05, 127.72, 152.90, 167.45. GC-MS(EI): m/z = 182 (M+), 167 (M+ − Me), 153 (M+ − OMe), 139 (M+ − (C3H6 + H)), 123 (M+ − CO2Me). (2Z,5Z)-Methyl 4,5,6-Trimethylhepta-2,5-dienoate (Z-10a). This product was estimated by comparison to MS spectra of E-10a. GCMS(EI): m/z = 182 (M+), 167 (M+ − Me), 153 (M+ − OMe), 139 (M+ − (C3H6 + H)), 123 (M+ − CO2Me). (2E,5Z)-Methyl 5,6-Dimethylocta-2,5-dienoate (E-10b). 1H NMR (400 MHz, rt, CDCl3): δ 0.92(t, J = 7.5 Hz, 3H, −Me), 1.59 (s, 3H, −Me), 1.63 (s(overlapped with a), 3H, −Me), 1.98 (q, J = 7.5 Hz, 2H, −CH2Me), 2.88 (d, J = 6.3 Hz, 2H, −CH2−), 3.69 (s(overlapped with a), 3H, −OMe), 5.76 (dt, J = 15.5, 1.7 Hz, 1H, CH−), 6.89 (dt, J = 15.5, 6.3 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.00, 17.90, 18.60, 27.24, 36.92, 51.37, 120.75, 122.70, 133.19, 147.82, 167.23. GC-MS(EI): m/z = 182 (M+), 167 (M+ − Me), 153 (M+ − OMe), 125 (M+ − (C4H8 + H)). (2Z,5Z)-Methyl 5,6-Dimethylocta-2,5-dienoate (Z-10b). 1H NMR (400 MHz, rt, CDCl3): δ 0.91 (t, J = 8.0 Hz, 3H, −CH2Me), 1.61 (s, 3H, −Me), 2.02 (q, J = 7.5 Hz, 2H, −CH2Me), 3.39 (dd, J = 7.5, 1.2 Hz, 2H, −CH2−), 3.69 (s, 3H, −OMe), 5.76 (dt, J = 11.5, 1.7 Hz, 1H, CH−), 6.09 (dt, J = 11.5, 7.5 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.06, 17.99, 18.39, 27.26, 33.73, 50.98, 118.82, 124.44, 132.39, 149.36, 166.93. GC-MS(EI): m/z = 182 (M+), 167 (M+ − Me), 153 (M+ − OMe), 125 (M+ − (C4H8 + H)). (3E,5Z)-Methyl 5,6-Dimethylocta-3,5-dienoate (10c). 1H NMR (400 MHz, rt, CDCl3): δ 0.95 (t, J = 7.5 Hz, 3H, −Me), 1.73 (s, 2H, −Me), 2.16 (q, J = 7.5 Hz, 2H, −CH2Me), 3.13 (d, J = 7.5 Hz, 2H, −CH2−), 3.66 (s, 3H, −OMe), 5.62 (dt, J = 15.5, 8.0 Hz, 1H,  CH−), 6.56 (d, J = 15.5 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.19, 14.40, 19.33, 27.06, 38.60, 51.77, 118.54, 125.17, 132.43, 136.88, 172.63. GC-MS(EI): m/z = 182 (M+), 167 (M+ − Me), 153 (M+ − OMe), 123 (M+ − CO2Me). 3,4-Dimethyl-2,4-hexadiene with Methyl Acrylate. Reaction with 3d (1 mol %) at 50 °C for 2 h produced cross-dimers in 81% yield (E-11a:Z-11a = 66:34). CSP GC (Rt-γDEXsa, oven temp = 140 °C, linear velocity 40 ca/s): RT11a1 = 13.01 min, RT11a2 = 13.40 min (ee = (Area11a2 − Area11a1)/(Area11a2 + Area11a1) × 100%). Reaction with (S,S)-3bb (10 mol %) at 50 °C for 4 h produced cross-dimers in 9% yield (E-11a:Z-11a = 100:0). Cross-dimer E-11a was observed in 9% yield with −34% ee. Reaction with (−)-3f (10 mol %) at 50 °C for 4 h produced cross-dimers in 31% yield (E-11a:Z-11a = 93:7). Crossdimer E-11a was observed in 29% yield with 36% ee. Reaction with (−)-3f (10 mol %) with twice the amount of diene at 50 °C for 4 h produced cross-dimers in 39% yield (E-11a:Z-11a = 98:2). Crossdimer E-11a was observed in 38% yield with 50% ee. (2E,5Z)-Methyl 4,5,6-Trimethylocta-2,5-dienoate (E-11a). 1H NMR (400 MHz, rt, CDCl3): δ 0.93 (t, J = 7.5 Hz, 3H, −CH2Me), 1.10 (d, J = 6.9 Hz, 3H, −Me), 1.46(s, 3H, −Me), 1.63 (d, J = 1.2 Hz, 3H, −Me), 2.03 (q, J = 7.5 Hz, 2H, −CH2Me), 3.53 (m, 1H, >CH−), 3.70 (s, 3H, −OMe), 5.73 (dd, J = 15.5, 2.3 Hz, 1H, CH−), 6.92 (dd, J = 15.5, 5.2 Hz, 1H, CH−). 13C{1H} NMR (100.5 MHz, rt, CDCl3): δ 13.39, 13.48, 17.18, 18.50, 27.10, 37.99, 51.41, 119.23, 127.50, 132.15, 153.35, 167.45. GC-MS(EI): m/z = 196 (M+), 181 (M+ − Me), 167 (M+ − Et), 165 (M+ − OMe). (2Z,5Z)-Methyl 4,5,6-Trimethylocta-2,5-dienoate (Z-11a). 1H NMR (400 MHz, rt, CDCl3): δ 0.91 (t, J = 7.5 Hz, 3H, −CH2Me), 1.06 (d, J = 6.9 Hz, 3H, −Me), 1.58 (d, J = 1.2 Hz, 3H, −Me), 1.61 (d,

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ASSOCIATED CONTENT

S Supporting Information *

Crystallogarphic data for 4ba and 4d, preliminary crystallographic data for 2d, CSP GC chromatograms for 10a and 11a, NMR data for dimethylpentadiene, dimethylhexadiene, and 1eI

dx.doi.org/10.1021/om500927z | Organometallics XXXX, XXX, XXX−XXX

Organometallics

Article

(8) Pioneering catalytic asymmetric reaction using chiral diene ligand: (a) Hayashi, T.; Ueyama, K.; Tokunaga, N.; Yoshida, K. J. Am. Chem. Soc. 2003, 125, 11508. (b) Fischer, C.; Defieber, C.; Suzuki, T.; Carreira, E. M. J. Am. Chem. Soc. 2004, 126, 1628. (9) For reviews, see: (a) Defieber, C.; Grutzmacher, H.; Carreira, E. M. Angew. Chem., Int. Ed. 2008, 47, 4482. (b) Shintani, R.; Hayashi, T. Aldrichimica Acta 2009, 42, 31. (10) For selected recent examples of chiral dienes in catalytic asymmetric reactions, see: (a) Ebe, Y.; Nishimura, T. J. Am. Chem. Soc. 2014, 136, 9284. (b) Shibata, T.; Shizuno, T. Angew. Chem., Int. Ed. 2014, 53, 5410. (c) Roy, I. D.; Burns, A. R.; Pattison, G.; Michel, B.; Parker, A. J.; Lam, H. W. Chem. Commun. 2014, 50, 2865. (d) Chen, Y.-J.; Chen, Y.-H.; Feng, C. G.; Lin, G.-Q. Org. Lett. 2014, 16, 3400. (e) Cui, Z.; Chen, Y.-J.; Gao, W.-Y.; Feng, C.-G.; Lin, G.-Q. Org. Lett. 2014, 16, 1016. (f) Gopula, B.; Chiang, C.-W.; Lee, W.-Z.; Kuo, T.-S.; Wu, P.-Y.; Henschke, J. P.; Wu, H.-L. Org. Lett. 2014, 16, 632. (g) Liu, Y.; Du, H. J. Am. Chem. Soc. 2013, 135, 6810. (h) Nishimura, T.; Ebe, Y.; Fujimoto, H.; Hayashi, T. Chem. Commun. 2013, 49, 5504. (i) Nishimura, T.; Nagamoto, M.; Ebe, Y.; Hayashi, T. Chem. Sci. 2013, 4, 4499. (j) Nishimura, T.; Noishiki, A.; Ebe, Y.; Hayashi, T. Angew. Chem. 2013, 125, 1821. (k) Keilitz, J.; Newman, S. G.; Lautens, M. Org. Lett. 2013, 15, 1148. (l) Fairhurst, N. W. G.; Munday, R. H.; Carbery, D. R. Synlett 2013, 24, 496. (m) Yang, H.; Xu, M. Chin. J. Chem. 2013, 31, 119. (11) Ru(η6-naphthalene)(η4-1,5-COD): (a) Vitulli, G.; Pertici, P.; Salvadori, P. J. Chem. Soc., Dalton Trans. 1984, 2255. (b) Crocker, M.; Green, M.; Howard, J. A. K.; Norman, N. C.; Thomas, D. M. J. Chem. Soc., Dalton Trans. 1990, 2299. (c) Bennett, M. A.; Neumann, H.; Thomas, M.; Wang, X.-Q.; Pertici, P.; Salvadori, P.; Vitulli, G. Organmetallics 1991, 10, 3237. (12) Renfrew, A. K.; Phillips, A. D.; Tapavicza, E.; Scopelliti, R.; Rothlisberger, U.; Dyson, P. J. Organometallics 2009, 28, 5061. (13) The preliminary molecular structure of 2d and the crystallographic data are also described in Supporting Information. (14) This synthetic method is modification of the literature method: Hirano, M.; Sakate, Y.; Inoue, H.; Arai, Y.; Komine, N.; Komiya, S.; Wang, X.-Q.; Bennett, M. A. J. Organomet. Chem. 2012, 46. (15) The branch selectivity is dependent on the nucleophilicity of the coordinated 1,3-diene. More electron-rich reaction side will be attacked by electron-deficient alkene. This detailed mechanism was discussed in ref 8a. (16) The cross-dimerizations between 3,4-dimethyl-2,4-hexadiene and other electron-deficient alkenes such as N,N-dimethyl acrylamide and acrylonitrile remained unreacted under the optimized conditions. The reaction of 3,4-dimethyl-2,4-hexadiene with methyl methacrylate gave the following cross-dimers (A and B) in moderate yield (53%, A/ B = 62/38).

11. CIFs for 2e−g, 3d, 4ba, and 4d. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

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

S.K.: Gakushuin University. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Ms. S. Kiyota for elemental analysis. This work was financially supported by JST ACT-C. A part of this work was supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas “3D Active-Site Sicence”, 26105003. Y.H. thanks Grant-in-Aid for JSPS Fellows, 25·4284.

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REFERENCES

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