Tandem Cyclization of Enynes Containing a Thioether or Ether

Nov 1, 2013 - Complex 2a, with a seven-membered thio ring bonded at Cβ of the vinylidene ... 9a, and 10c have been confirmed by X-ray diffraction ana...
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Tandem Cyclization of Enynes Containing a Thioether or Ether Linkage via Ruthenium Allenylidene and Vinylidene Complexes Yi-Jhen Feng, Ji-Xian Lo, Ying-Chih Lin,* Shou-Ling Huang, Yu Wang, and Yi-Hung Liu Department of Chemistry, National Taiwan University, Taipei, Taiwan 106, Republic of China S Supporting Information *

ABSTRACT: The two aromatic S-enynes HCCCH(OH)(C6H4)SCH2C(R)CH2 (1a, R = Me; 1b, R = H) containing olefinic groups with and without an internal methyl substitutent and the O-enyne HCCCH(OH)CMe2CH2OCH2C(Me)CH2 (1c) also with an internal methyl substituent on the olefinic group but with no aromatic group have been prepared. In the [Ru]Cl-induced ([Ru] = Cp(PPh)3Ru) reactions of 1a,c, the presence of the methyl group promotes cyclization reactions and their tandem cyclizations are further induced by MeOH. The reaction of 1a in CH2Cl2 gives the three products 2a−4a. Complex 2a, with a seven-membered thio ring bonded at Cβ of the vinylidene ligand, is formed via a C−C bond formation between two unsaturated groups in moderate yield. Complex 3a is formed via migration of PPh3 from the metal onto the terminal carbon of the alkynyl group followed by coordination of the S atom. The carbene complex 4a is formed by S addition to the internal carbon of the alkynyl group accompanied by migration of the allylic group from sulfur to the newly formed thiophene ring. Tandem cyclization of 1a in MeOH generates the organic product 8a via 2a. In the reaction, the vinylidene complex 7a, a formal methanol addition product of 2a, is also formed as a side product. Deprotonation of 7a gives the acetylide complex 9a. The reaction of 1c affords the vinylidene complex 2c in CH2Cl2 via a similar cyclization process with no other side product. Deprotonation of 2c followed by allylation gave the disubstituted vinylidene complex 10c. Tandem cyclization of 1c in MeOH also gives the organic product 8c. In the reaction of [Ru]Cl with 1b containing no methyl group in the olefinic part, no C−C bond formation was observed. The reactions of [Ru]NCCH3+ with 1a,b each gave only 4a,b, respectively, with no side product. All of these reaction products are characterized by spectroscopic methods as well as elemental analysis. In addition, the structures of three complexes 5a, 9a, and 10c have been confirmed by X-ray diffraction analysis.

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product in MeOH.7 The methyl substituent on the internal carbon of the olefinic part of enynes promotes cyclization reactions.5g,7 We now extend our study to explore the cyclization of S- and O-containing 1,8-enynes, also with a methyl substituent on the internal carbon of the olefinic group, using ruthenium complexes. Vinylidene complexes retaining an olefinic group are obtained after the first cyclization, which progress to further cyclization in different solvents to give a tricyclic product. In addition, for S-enynes, we observed the exclusive formation of substituted benzothiophene and its subsequent oxidation to yield the corresponding aldehyde, both in high yield, when the reaction conditions are properly modified. Cyclizations of a similar enyne system with two terminal methyl substituents, instead of one internal methyl substituent, at the olefinic groups was also investigated. The presence of two methyl substituents along with their location significantly alters the cyclization reactivity. These results will be reported separately.7b

INTRODUCTION Sulfur- and oxygen-containing heterocyclic compounds are widely found in natural products, and many of them display biological activity.1 In addition, compounds of this type also serve as valuable building blocks in organic synthesis and are now considered as important structural units in materials development. Therefore, many new synthetic approaches to these heterocyclic compounds have been reported.2 Transitionmetal-catalyzed cycloisomerization and olefin metathesis are now regularly employed for preparations of these heterocycles.3,4 It is now well-known that the ruthenium-catalyzed or induced intra- and intermolecular carbon−carbon bond forming reactions between propargylic alcohols and alkenes5 readily proceed via an allenylidene intermediate under mild conditions. Enynes with no hydroxyl group undergo ruthenium-induced cyclizations most likely via vinylidene intermediates.6 These allenylidene and vinylidene complexes play crucial roles in inducing intramolecular enyne coupling, leading to cyclized products. Previously, we described the ruthenium-mediated cycloisomerizations of 1,n-enynes (n = 6− 8), each with a methyl substituent at the internal carbon of the terminal olefinic group, producing a vinylidene complex with a newly formed five- to seven-membered ring containing an olefinic group.5g,7 Such a vinylidene complex can undergo further cyclization using the olefinic group to give a tricyclic © 2013 American Chemical Society

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RESULTS AND DISCUSSION First Cyclization. Treatment of the aromatic S-enyne 1a, containing one methyl group on the internal carbon of the Received: July 26, 2013 Published: November 1, 2013 6379

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attests to the C−C bond formation, and the separation C(11)− C(13) = 1.315(5) Å corresponds to a double bond. As shown in Scheme 2, the cyclization reaction is proposed to proceed via the allenylidene complex A, acting as enophile.

olefinic group, with [Ru]Cl ([Ru] = Cp(PPh3)2Ru) in the presence of NH4PF6 in CH2Cl2 at room temperature afforded the vinylidene complex 2a, the metallacyclic complex 3a, and the carbene complex 4a, in a ratio of 25:67:8, as determined by NMR in a 93% total yield (see Scheme 1). Deprotonation of 2a

Scheme 2. Formation of 2a−4a from 1a Scheme 1. Reaction of 1a with [Ru]Cl in CH2Cl2

took place when the mixture was passed through an Al2O3 column, yielding the acetylide complex 5a as the first yellow band. The second band contained a mixture of 3a and 4a. Protonation of 5a with HBF4 at 0 °C quantitatively yielded 2a. The structures of 2a and 5a, each with a newly formed sevenmembered ring, have been determined by 2D-NMR data and 5a have been further characterized by single-crystal X-ray diffraction analysis. In the 2D-HMBC NMR spectrum of 2a, the triplet peak at δ 344.77 with 2JCP = 15.7 Hz assigned to Cα shows correlation with the multiplet 1H resonance at δ 4.44 assigned to CγH, which shows correlations with two 1H multiplet resonances at δ 2.65 and 2.37, assigned to the neighboring CH2 group in the COSY NMR spectrum. The 2D NMR spectra of 5a also display similar correlations. Single crystals of 5a are obtained from an ether/n-pentane solution at 0 °C. An ORTEP type view of 5a is shown in Figure 1, with

Addition of the tethering olefinic group5d,f to the electrophilic Cγ causes C−C bond formation, giving B bearing a cationic charge at the methyl-substituted tertiary carbon. The stability of the tertiary carbocationic intermediate assists this cyclization. A concerted allenylidene−ene5a,c process, not shown in the scheme, could be an alternative pathway. For a similar ruthenium allenylidene complex with no methyl group on the olefinic part, no cyclization reaction was observed.5g,7 Interestingly, at slightly higher temperature, the C−C bond formation leading to 2a is hindered in CH2Cl2. The reaction yields 3a as the major product at 40 °C. The relatively upfield shifted 31P resonance at δ −5.52 along with the doublet 1H peak at δ 5.65 with 2JHP = 34.0 Hz in the NMR spectra of 3a reveal the presence of a phosphonium group. The singlet 1H resonance at δ 3.38, which disappears upon addition of D2O, is assigned to OH. These data clearly reveal migration of a PPh3 from metal to Cα and the presence of a hydroxyl group. Therefore, formation of 3a should proceed via π coordination of the triple bond to the metal center to give C,8 as shown in Scheme 2, instead of via the allenylidene intermediate A. Then migration of PPh3 to Cα provides a vacant site for subsequent sulfur coordination to afford 3a. Thermolysis of 2a in CH3CN at 50 °C affords the enyne product 6a and [Ru]NCCH3+ (see Scheme 1).9 Previously, [Ru]NCCH3+-catalyzed cyclization reactions of aromatic allcarbon enynes containing propargyl alcohol with one methyl group on the internal carbon of the olefinic group bound to the ortho position of the aromatic ring was reported7 to afford organic products with newly formed six-membered rings. However, when 1a was directly treated with [Ru]NCCH3+ in CH2Cl2, conversion of 1a to 6a was not observed; instead, the reaction produced 4a as the only product. A series of 2D NMR studies and mass spectroscopy established the structure of 4a. In the 1H NMR spectrum of 4a, the relatively downfield triplet resonance at δ 14.92 is assigned to CαH. As shown in Scheme 2, the cyclization yielding 4a is believed to proceed by π coordination of the triple bond to the metal center to give C. Then nucleophilic addition of S atom to Cβ of the activated triple bond gives intermediate E. Dehydroxylation is followed by a migration of the methyl-substituted allylic group to give 4a. Migration of the allylic group to Cγ could proceed either via a direct 1,3-allyl shift10 or by a Cope rearrangement.11 Oxidation of 4a to Aldehyde. A recent study by our group revealed that a metal carbene complex with a highly

Figure 1. ORTEP drawing of 5a. For clarity, aryl groups of the PPh3 ligands, except the ipso carbons on Ru, are omitted (thermal ellipsoids are set at the 50% probability level). Selected bond distances (Å) and angles (deg): Ru(1)−C(1), 2.021(3); C(1)−C(2), 1.207(4); C(2)− C(3), 1.481(4); C(3)−C(4), 1.518(4); S(1)−C(9), 1.768(3); S(1)− C(10), 1.826(4); C(11)−C(12), 1.518(4); C(11)−C(13), 1.315(5); C(3)−C(12), 1.549(4); C(2)−C(1)−Ru(1), 172.4(2); C(1)−C(2)− C(3), 178.0(3); C(9)−C(4)−C(3), 118.6(3); C(9)−S(1)−C(10), 104.66(16); C(10)−C(11)−C(12), 116.3(3); C(13)−C(11)−C(12), 122.0(4); C(13)−C(11)−C(10), 121.6(4).

selected bond distances and angles. Obviously, a new C−C bond formed between Cγ and the terminal carbon of the olefinic group. The acetylide ligand is nearly linear (C(2)− C(1)−Ru(1) = 172.4(2)°), showing the bond lengths Ru(1)− C(1) = 2.021(3) Å, C(1)−C(2) = 1.207(4) Å, and C(2)−C(3) = 1.481(4) Å. The bond length of C(3)−C(12), 1.549(4) Å, 6380

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methoxide addition to B shown in Scheme 2. For 7a, with no olefinic group, no further cyclization is observed. However, deprotonation of 7a yields the acetylide complex 9a. The structures of 7a−9a have also been established by a series of 2D NMR studies and mass spectra, and complex 9a was characterized by single-crystal X-ray diffraction analysis. Diastereoisomers are observed for both 7a and 9a in an approximate ratio of 1:0.5 due to the presence of two stereogenic centers. Spectroscopic data clearly reveal additions of OMe groups to the newly formed seven-membered ring in 7a and 9a. For 8a, the two multipet peaks at δ 5.82 and 5.65 are assigned to two olefinic hydrogens in the 1H NMR spectrum. In the HMBC spectra of 8a, the 13C resonance at δ 41.16 assigned to SCH2 shows correlation with the 1H resonances at δ 2.46, 2.24, and 2.09 assigned to two other methylene groups. These correlations support the proposed structure of 8a. The cascade cyclization of 1a is proposed to proceed via 2a, as shown in Scheme 4. Then the second C−C bond formation between the olefinic moiety and Cα yields the cationic species G. Addition of methoxide at the cationic carbon followed by protonation gives 8a and [Ru]Cl. Single crystals of 9a were obtained from a solution of ether/acetone at 0 °C. An ORTEP type view of 9a is shown in Figure 2, with selected bond distances and angles.

conjugated ring system may be readily oxidized in the presence of tertiary amines under an oxygen atmosphere to yield the corresponding aldehyde.12 Also having a highly conjugated ring system, 4a was thus reacted with O2 in the presence of excess NEt3 in CH3CN at ambient temperature to afford 2benzothiophenecarbaldehyde (11a) in 83% yield. In the absence of NEt3, no aldehyde was obtained even under an oxygen atmosphere. Compound 11a has been used as a precursor for the synthesis of dihydrofuro[3,4-c]pyridinones, showing inhibition of the cytolytic effects of the lymphocyte toxin perforin.13 The proposed pathway for the oxygenation is shown in Scheme 3.12 Activation of O2 by coordination to the metal Scheme 3. Mild Oxidation of 4a To Give Aldehyde

center is initiated by dissociation of a PPh3 ligand.14 Then, NEt3 is reacted with the activated oxygen to yield ONEt3 and an unobserved metal oxo carbene complex.15 Coupling of the oxo and carbene ligands is promoted by recoordination of PPh3, leading to the intermediate M,16 which readily generates 11a in good yield. Tandem Cyclization of 1a. Previously the Ru-catalyzed cyclization of the aromatic enynes HCCCH(OH)(C6H4)(CH2)nCMeCH2 (n = 1, 2) with a methyl group on the olefinic unit in CH2Cl2 was reported to afford the vinylidene complexes, each with an olefinic group which would undergo further cyclization in MeOH.7 While the first cyclization product 6a from 1a is also an enyne, more cyclization is thus expected. Indeed, the reaction of 1a with [Ru]Cl in MeOH yields the tandem cyclization product 8a together with 2a, 3a, and the vinylidene complex 7a, in a ratio of 15:45:29:11 in a 95% total yield at room temperature (see Scheme 4). The yield of 8a is improved to 40% at 50 °C. In EtOH, thermal treatment of 1a with [Ru]Cl also affords 3a and 8a′, with an ethoxy group. The formation of 7a is reasonably explained by the

Figure 2. ORTEP drawing of 9a. For clarity, aryl groups of the PPh3 ligands on Ru, except the ipso carbons, are omitted (thermal ellipsoids are set at the 50% probability level). Selected bond distances (Å) and angles (deg): Ru(1)−P(1), 2.2917(11); Ru(1)−P(2), 2.2901(9); Ru(1)−C(1), 2.041(4); C(1)−C(2), 1.198(6); C(2)−C(3), 1.499(6); C(3)−C(4), 1.509(7); C(3)−C(12), 1.571(7); S(1)−C(9), 1.756(6); S(1)−C(10), 1.795(7); C(10)−C(11), 1.545(9); C(11)−C(12), 1.501(8); C(11)−C(13), 1.531(9); O(1)−C(11), 1.417(8); O(1)− C(14), 1.341(9); C(11)−C(13), 1.531(9); C(2)−C(1)−Ru(1), 178.6(4); C(1)−C(2)−C(3), 173.6(5); C(9)−S(1)−C(10), 102.2(3); C(12)−C(11)−C(10), 115.3(5); C(11)−C(12)−C(3), 117.2(5).

Scheme 4. Tandem Cyclization of 1a in MeOH

Tandem Cyclization of 1c. The aliphatic enyne 1c, also containing a methyl substituent in the olefinic group but with an ether linkage instead of the thio ether linkage of 1a, underwent similar [Ru]Cl-induced cyclization to give simpler cyclization products. Treatment of 1c with [Ru]Cl in the presence of NH4PF6 in CH2Cl2 afforded the vinylidene complex 2c with a newly formed seven-membered oxepane derivative. Deprotonation of 2c at the vinylidene ligand with NaOMe/ MeOH gave the acetylide complex 5c as a light yellow powder, which regenerated 2c in HBF4. Complex 5c, with a relatively remote stereogenic center at Cγ, displays a somewhat broad 31P 6381

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resonance at δ 51.94 for 5c. The doublet resonance at δ 4.57 assigned to CβH in the 1H NMR spectrum of 2c disappears in the 1H NMR spectrum of 5c. Heating 2c in CH3CN to reflux for 1 day affords the organic enyne 6c, as shown in Scheme 5.

distances and angles, confirming the presence of the sevenmembered oxepane ring in the vinylidene ligand. The bond lengths Ru(1)−C(1) = 1.864(3) Å and C(1)−C(2) = 1.308(5) Å show a typical vinylidene bond skeleton. The bond length C(3)−C(4) = 1.539(6) Å attests to the C−C bond formation and C(5)−C(9) = 1.367(9) Å is a double bond. The promotional effect of MeOH for tandem cyclization is also observed in this system. Thermolysis of 2c and [Ru]Cl in CHCl3/MeOH at 50 °C generated the fused cyclic organic product 8c in 90% yield. In addition, thermolysis of 6c with 30 mol % of [Ru]NCCH3+ in CHCl3/MeOH at 50 °C also afforded 8c in high yield. Compound 8c was also directly obtained from the reaction of 1c with 30 mol % of [Ru]NCCH3+ in CHCl3/MeOH at 50 °C, in 70% yield. In EtOH and i-PrOH, treatment of 1c with [Ru]NCCH3+ afforded 8c′ and 8c″, respectively. As the steric bulk of the alcohol increases, the yield of 8c″ decreases to about 30% yield. The structure of 8c has been determined by spectroscopic methods. When 1c is treated with [Ru]NCCH3+ in CDCl3/ CD3OD, both olefinic protons of 8c-D are deuterated. Therefore, the cascade cyclization of 1c should first give 2c, undergoing a fast H/D exchange process between the vinylidene hydrogen and solvent. Then, addition of the olefinic moiety to Cα of the vinylidene ligand in 2c yields the cationic species J. Addition of alkoxide at the cationic site, followed by protonation or deuteration, gives 8c and [Ru]NCCH3+ (see Scheme 5). Enynes with No Methyl Group. To study the effect of the methyl substituent in the olefinic group on the cyclization reaction, we prepared the similar aromatic propargylic alcohol 1b, containing an analogous ortho-substituted olefinic chain but no methyl group. Treatment of 1b with [Ru]Cl in CH2Cl2 at ambient temperature afforded a mixture of the metallacyclic complex 3b, the phosphonium acetylide complex 12b, and the allenylidene complex 13b, in a ratio of 52:14:34 in a 93% total yield (see Scheme 6). The same reaction at 40 °C yields 3b as

Scheme 5. Tandem Cyclization Reactions of 1c

Alternatively, direct conversion of 1c to 6c is catalyzed by 30 mol % of [Ru]NCCH3+ in CHCl3 at 60 °C in 78% yield. In the 1 H NMR spectrum of 6c, the characteristic doublet acetylenic resonance appears at δ 2.10 with 4JHH = 2.5 Hz. Two multiplet resonances at δ 4.92 and 4.83 are assigned to the olefinic methylene group on the oxepane ring. The cyclization reaction is believed to proceed via formation of the allenylidene intermediate H (see Scheme 5) followed by an intramolecular attack of the alkene group onto Cγ of the allenylidene ligand, giving the alkynyl complex I with a cationic charge at the methyl-substituted tertiary carbon. A subsequent 1,5-hydrogen shift then yields 2c. The vinylidene ligand is readily replaced by CH3CN to produce 6c. Treatment of 5c with allyl bromide and methyl iodide afforded the vinylidene complexes 10c and 10c′, respectively (see Scheme 5), which are stable under thermolytic conditions and display similar characteristic NMR data. Single crystals of 10c, with an allylic group at Cβ, were obtained in diethyl ether/ CH2Cl2 solution, and the structure was determined by a singlecrystal X-ray diffraction study. An ORTEP type view of the cationic complex 10c is shown in Figure 3 with selected bond

Scheme 6. Reactions of 1b

the major product along with the allyltriphenylphosphonium product.17 For the reaction of 1b with [Ru]Cl in the presence of excess PPh3, a 95% yield of 12b is obtained.18 Unlike 1a, which shows reactivity for cyclization, compound 1b in CH2Cl2 displays no cyclization involving C−C bond formation. The stability of the tertiary carbocation originating from the presence of the methyl group in 1a should play a key role in promoting the cyclization reaction. The reaction of 1b in MeOH yields no cyclization product. Interestingly, when 1b was treated with [Ru]NCCH3+ in CH2Cl2, the carbene complex 4b, analogous to 4a, was isolated as the only product. Sulfur attack at Cβ indicates the

Figure 3. ORTEP drawing of 10c. For clarity, phenyl groups of the PPh3 ligands on Ru, except the ipso carbons, and PF6−, are omitted (thermal ellipsoids are set at the 25% probability level). Selected bond distances (Å) and angles (deg): Ru(1)−C(1), 1.864(3); C(1)−C(2), 1.308(5); C(2)−C(12), 1.536(5); C(3)−C(4), 1.539(6); C(5)−C(9), 1.367(9); C(13)−C(14), 1.241(7); Ru(1)−C(1)−C(2), 168.0(3); C(4)−C(3)−C(8), 115.4(3); C(6)−C(5)−C(4), 117.0(6); C(6)− O(1)−C(7), 115.5(6). 6382

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intermediacy of the π-coordinated alkynyl ligand. Allylic migration also takes place. The reaction of 4b with oxygen in the presence of excess NEt3 was also carried out in CH3CN at ambient temperature for 1 day to afford aldehyde 11b in 88% yield (Scheme 6). Isomerization of the double bond is caused by a more stable conjugation with the ring system.

6.8 Hz, 1H, OH), 1.85 (s, 3H, Me), 0.18 (s, 9H, TMS). 13C NMR (CDCl3, 100.6 MHz): δ 141.73 (CH), 140.67 (Ph), 134.31 (Ph), 132.88 (Ph), 128.74 (Ph), 127.62 (Ph), 127.46 (Ph), 114.44 (CH2), 104.93 (C), 91.75 (C), 63.15 (CH), 43.30 (CH2), 21.22 (Me), −0.17 (Me3Si). To a solution of S1 (3.0 g, 10 mmol) in 10 mL of THF at room temperature was added Bu4NF (20.7 mL, 21 mmol). After 4 h the reaction mixture was extracted with diethyl ether. The organic layers were washed with brine, dried over MgSO4, and subjected to flash column chromatography over silica gel (SiO2) with a 9/1 hexane/EA mixture as eluent to give the light yellow oil 1a (2.14 g, 98% yield). Spectroscopic data of 1a are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.72 (m, 1H, Ph), 7.44 (m, 1H, Ph), 7.29 (m, 2H, Ph), 5.96 (dd, 3JHH = 6.1 Hz, 4JHH = 2.3 Hz, 1H, CH), 4.80 (t, 3 JHH = 1.5 Hz, 1H, CH2), 4.74 (d, 3JHH = 0.7 Hz, 1H, CH2), 3.52 (s, 2H, CH2), 2.74 (m, 1H, CCH), 2.66 (d, 3JHH = 2.3 Hz, 1H, OH), 1.86 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 141.28 (CH), 140.59 (Ph), 134.31 (Ph), 132.72 (Ph), 128.94 (Ph), 127.63 (Ph), 127.47 (Ph), 114.43 (CH2), 83.37 (C), 74.94 (CH), 62.52 (CH), 43.35 (CH2), 21.20 (Me). MS ESI: m/z 219.0844 [M + H]+. Anal. Calcd for C13H14OS: C, 71.52; H, 6.46. Found: C, 71.47; H, 6.49. Synthesis of 1b. Compound S2 (2.83 g, 93% yield) was similarly prepared from Me3SiCCH (3.5 mL, 25 mmol), n-BuLi (7.2 mL, 18 mmol), and 2-(allylthio)benzaldehyde21b (2.0 g, 11 mmol). Spectroscopic data of S2 are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.69 (m, 1H, Ph), 7.43 (m, 1H, Ph), 7.28 (m, 2H, Ph), 5.92 (d, 3JHH = 6.1 Hz, 1H, CH), 5.85 (m, 2H, CH), 5.05 (d, 3JHH = 8.6 Hz, 1H, cis  CH2), 5.04 (d, 3JHH = 17.3 Hz, 1H, trans CH2), 3.54 (d, 3JHH = 7.0 Hz, 2H, CH2), 2.90 (d, 3JHH = 6.1 Hz, 1H, OH), 0.18 (s, 9H, Me3Si). 13 C NMR (CDCl3, 100.6 MHz): δ 141.81 (Ph), 133.72 (CH), 133.39, 132.88, 128.73, 127.67, 127.66 (Ph), 118.01 (CH2), 104.94 (C), 91.72 (C), 63.12 (CH), 38.62 (CH2), −0.17 (Me3Si). Then compound 1b (1.41 g, 96% yield) was similarly prepared from Bu4NF (14.5 mL, 14.5 mmol) and S2 (3.0 g, 9.9 mmol). Spectroscopic data of 1b are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.72 (m, 1H, Ph), 7.44 (m, 1H, Ph), 7.29 (m, 2H, Ph), 5.95 (dd, 3JHH = 6.1 Hz, 4JHH = 2.2 Hz, 1H, CH), 5.86 (m, 1H, CH), 5.06 (m, 2H, CH2), 3.55 (d, 3 JHH = 7.1 Hz, 2H, CH2), 2.92 (d, 3JHH = 2.3 Hz, 1H, CCH), 2.66 (d, 3JHH = 2.3 Hz, 1H, OH). 13C NMR (CDCl3, 100.6 MHz): δ 141.31 (Ph), 133.69 (CH), 133.27, 132.63, 128.93, 127.66, 127.52 (Ph); 118.14 (CH2), 83.40 (C), 75.01 (CH), 62.46 (CH), 38.60 (CH2). MS ESI: m/z 205.0687 [M + H]+. Anal. Calcd for C12H12OS: C, 70.55; H, 5.92. Found: C, 70.50; H, 5.94. Synthesis of 2a and 5a. A mixture of [Ru]Cl (300 mg, 0.41 mmol), 1a (143 mg, 0.62 mmol), and NH4PF6 (166 mg, 1.02 mmol) in CH2Cl2 (40 mL) was stirred at ambient temperature for 1 day. The solvent was removed under vacuum, CH2Cl2 was used to extract the product, and the crude mixture was filtered through Celite to remove the insoluble precipitates. The filtrate was concentrated to ca. 5 mL and was added to stirred diethyl ether (60 mL) to produce an olive precipitate. The powder was collected, washed with diethyl ether, and dried under vacuum to give a mixture of 2a, 3a, and 4a. The mixture was dissolved in CH2Cl2 and was passed through an acidic Al2O3 column with hexane/ether/CH2Cl2 as eluent. Collecting the yellow band followed by drying under vacuum resulted in the yellow powder 5a (278 mg, 79% yield), mp 127−129 °C. Spectroscopic data of 5a are as follows. 1H NMR (C6D6, 400.1 MHz): δ 8.55−6.886.90 (m, Ph), 5.11 (d, 3JHH = 9.1 Hz, 1H, CγH), 4.73 (s, 1H, CH), 4.64 (s, 1H,  CH), 4.45 (s. 5H, Cp), 3.21−3.15 (m, 3H, SCH2 and CHCH2), 2.52 (m, 1H, CHCH2). 13C NMR (C6D6, 100.6 MHz): δ 148.86−126.01 (Ph, C), 114.02 (CH2), 112.39 (Cβ), 96.40 (t, 2JCP = 24.9 Hz, Cα), 85.12 (Cp), 47.40 (CH2), 40.33 (C), 38.50 (SCH2). 31P NMR (C6D6, 162.0 MHz): δ 51.22, 50.71 (2 d, 2Jpp = 37.4 Hz, PPh3). MS ESI: m/z 891.19 [M + 1]+. Anal. Calcd for C54H46P2RuS: C, 72.81; H, 5.21. Found: C, 73.11; H, 5.34. Single crystals of 5a were obtained from a hexane/acetone solution at 5 °C. A solution of HBF4·Et2O (48%, 0.02 mL, 0.11 mmol) in diethyl ether (20 mL) was added dropwise at 0 °C to a stirred solution of 5a (300 mg, 0.33 mmol) in 10 mL of ether. Immediately, insoluble solid precipitated but the addition was continued until no further solid was

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CONCLUSION The [Ru]Cl-induced cyclization reactions of S- and O-enynes 1a,c involving C−C bond formation are promoted by the presence of a methyl substituent in the olefinic part via formation of a carbocationic intermediate. Because of the higher coordinating ability of S, the reaction of S-enyne 1a produces the cyclized product along with several side products. On the other hand, the reaction of O-enyne 1c gives the cyclized product with no side products. Furthermore, tandem cyclizations of both 1a,c are induced in MeOH, yielding benzofused cyclic thioether 8a and fused cyclic ether 8c, respectively, while in CH2Cl2 only one cyclization is observed. For the Senyne 1b with no methyl substituent, a similar cyclization is not observed. However, for 1a,b, cyclization involving C−S bond formation is achieved by the use of [Ru]NCCH3+. The cyclization is accompanied by allylic migration to give exclusively the carbene complexes 4a,b, respectively. Triethylamine is found to promote oxidation of the carbene ligand of 4 in the presence of oxygen to give aldehyde in high yield. Even though many products are obtainable from S-enynes 1a,b induced by [Ru]Cl, product selectivity is achieved by careful control of the reaction conditions.

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EXPERIMENTAL SECTION

General Procedures. The manipulations were performed under an atmosphere of dry nitrogen using vacuum-line and standard Schlenk techniques. Solvents were dried by standard methods and distilled under nitrogen before use. The ruthenium complex Cp(PPh3)2RuCl19 and 1c20 were prepared by following the methods reported in the literature. The C and H analyses and X-ray diffraction studies were carried out at the Regional Center of Analytical Instrument at the National Taiwan University. Mass spectra were recorded using a LCQ Advantage (ESI) and Finnigan MAT 95S (EI) mass spectrometers. NMR spectra were recorded on Bruker Avance III 400 and 500 FT-NMR spectrometers at room temperature (unless stated otherwise). 1H NMR and 13C NMR spectra were obtained at ambient temperature, and chemical shifts are expressed in parts per million (δ, ppm). Proton chemical shifts are referenced to δ 7.26 (CDCl3), 5.32 (CD2Cl2), 7.15 (C6D6), and 2.05 (acetone-d6). Carbon chemical shifts are referenced to δ 77.1 (CDCl3), 53.92 (CD2Cl2), 127.69 (C6D6), and 205.36 and 28.99 (acetone-d6). The 31P NMR spectra were measured relative to external 85% phosphoric acid. Both 13 C and 31P spectra were proton-decoupled spectra. Melting points were measured in open capillaries on a MPA100 melting point apparatus and are uncorrected. Synthesis of 1a. To a solution of Me3SiCCH (4.1 mL, 28.6 mmol) in 10 mL of THF at −78 °C, under nitrogen, was added n-BuLi (8.3 mL, 21 mmol). After 20 min, 2-(2-methylallylthio)benzaldehyde21a (2.5 g, 13 mmol) in 10 mL of dry diethyl ether was added. The mixture was kept at −78 °C for 30 min and was warmed to room temperature. The mixture was quenched with saturated aqueous NH4Cl solution and extracted with diethyl ether (3 × 10 mL). The combined organic layers were washed with brine, dried over MgSO4, and evaporated to give the crude product, which was purified by flash chromatography on a silica gel column (hexane/EA, 9/1) to give S1 (3.28 g, 87% yield). Spectroscopic data of S1 are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.69 (m, 1H, Ph), 7.40 (m, 1H, Ph), 7.26 (m, 2H, Ph), 5.93 (s, 1H, CH), 4.78 (t, 3JHH = 1.5 Hz, 1H, CH2), 4.72 (s, 1H, CH2), 3.50 (s, 2H, CH2), 2.97 (t, 3JHH = 6383

dx.doi.org/10.1021/om400742x | Organometallics 2013, 32, 6379−6387

Organometallics

Article

formed. The solution was then decanted, and the pink solid was washed with diethyl ether and dried in vacuo to give the pink powder 2a (225 mg, 75% yield), mp 137−139 °C. Spectroscopic data of 2a are as follows. 1H NMR (CD2Cl2, 400.1 MHz): δ 7.58−7.03 (m, Ph), 5.65 (d, 2JHH = 10.0 Hz, 1H, CβH), 5.09 (s, 5H, Cp), 4.96 (s, 1H, CH2), 4.89 (s, 1H, CH2), 4.44 (m, 1H, CH), 3.35, 3.21 (2 d, 2JHH = 12.4 Hz, 2H, SCH2), 2.65 (m, 1H, CH2), 2.37 (m, 1H, CH2). 13C NMR (CD2Cl2, 100.6 MHz): δ 344.77 (t, 2JCP = 15.7 Hz, Cα), 146.89− 127.20 (Ph, C), 115.96 (CH2), 115.67 (Cβ), 94.40 (Cp), 45.11 (CH2), 39.40 (SCH2), 38.83 (Cγ). 31P NMR (CD2Cl2, 162.0 MHz): δ 44.07, 42.73 (2 d, 2Jpp = 26.6 Hz, PPh3). MS ESI: m/z 891.19 [M]+. Anal. Calcd for C54H47BF4P2RuS: C, 66.33; H, 4.84. Found: C, 66.91; H, 5.08. Synthesis of 3a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 1a (88 mg, 0.41 mmol), and NH4PF6 (111 mg, 0.69 mmol) in CH2Cl2 (40 mL) was stirred at 40 °C for 1 day. The solvent was removed under vacuum, CH2Cl2 was used to extract the crude product, and the mixture was filtered through Celite to remove the insoluble precipitates. The filtrate was concentrated to ca. 5 mL and added to stirred diethyl ether (60 mL) to produce a green-yellow precipitate, which was collected, washed with diethyl ether, and dried under vacuum to give a green-yellow powder containing mostly 3a and a trace amount of unidentified product (less than 5% of the mixture from NMR) (total weight 236 mg, yield of 3a ca. 80%). Spectroscopic data of 3a are as follows. 1H NMR (CDCl3, 500.2 MHz): δ 7.75−6.87 (m, Ph), 5.87 (d, 2JHP = 36.2 Hz, 1H, CHPPh3), 4.81 (s, 1H,  CH), 4.63 (s, 5H, Cp), 4.53 (s, 1H, CH), 3.79 (d, 2JHH = 12.5 Hz, 1H, CH2), 3.47 (d, 2JHH = 12.6 Hz, 1H, CH2), 3.40 (s, 1H, OH), 1.71 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 233.50 (t, 2JCP = 16.4 Hz, Cα), 145.55−120.50 (Ph, C), 117.08 (CH), 100.75 (d, 1JCP = 64.8 Hz), 81.68 (Cp), 78.23 (CH), 56.87 (CH2), 21.29 (Me). 31P NMR (CDCl3, 202.5 MHz): δ 55.73 (br, PPh3), −5.67 (br, PPh3). MS ESI: m/z 909.20 [M]+. Anal. Calcd for C54H49F6OP3RuS: C, 61.53; H, 4.69. Pure complex 3a was not obtained. Synthesis of 4a. A mixture of [Ru]NCCH3+ (300 mg, 0.34 mmol), 1a (112 mg, 0.51 mmol), and NH4PF6 (166 mg, 1.02 mmol) in CH2Cl2 (40 mL) was stirred at ambient temperature for 1 day. A procedure similar to that used to obtain the crude mixture of 3a yielded a filtrate, which was concentrated to ca. 5 mL and added to stirred diethyl ether (60 mL) to produce an olive precipitate. The powder was collected, washed with diethyl ether, and dried under vacuum to give the olive powder 4a (186 mg, 83% yield), mp 184− 185 °C. Spectroscopic data of 4a are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 14.92 (t, 3JPH = 11.3 Hz, 1H, CαH), 8.05−6.95 (m, Ph), 5.15 (s, 5H, Cp), 4.41 (s, 1H, CH2), 3.76 (s, 1H, CH2), 2.67 (s, 2H, CH2), 1.66 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 280.26 (t, 2JCP = 12.2 Hz, Cα), 162.58−123.65 (Ph, C), 112.69 ( CH2), 94.78 (Cp), 35.45 (CH2), 23.70 (Me). 31P NMR (CDCl3, 162.0 MHz): δ 45.23 (s, PPh3). MS ESI: m/z 891.19 [M]+. Anal. Calcd for C54H47F6P3RuS: C, 62.60; H, 4.57. Found: C, 62.35; H, 4.46. Synthesis of 6a. A solution of 2a (200 mg, 0.20 mmol) in CH3CN (10 mL) was stirred at 50 °C for 1 day. The crude mixture was concentrated to ca. 3 mL and added to a stirred diethyl ether (20 mL) to produce a precipitate and a yellow filtrate. The yellow filtrate was collected and subjected to flash column chromatography over silica gel (SiO2) with hexane as eluent to give the light yellow oil 6a (37.3 mg, 91% yield). Spectroscopic data of 6a are as follows. 1H NMR (CD2Cl2, 400.1 MHz): δ 7.76 (m, 1H, Ph), 7.51 (m, 1H, Ph), 7.33 (m, 1H, Ph), 7.18 (m, 1H, Ph), 4.82 (m, 2H, CH2), 4.50 (m, 1H, CH), 3.35 (q, 3 JHH = 12.2 Hz, 2H, SCH2), 2.93 (m, 1H, CH2), 2.43 (d, 3JHH = 2.5 Hz, 1H, CH), 2.36 (m, 1H, CH2). 13C NMR (CDCl3, 100.6 MHz): δ 143.35 (C), 143.01, 134.33, 133.27, 128.33, 127.32, 127.07 (Ph), 116.00 (CH2), 85.06 (C), 72.02 (CH), 44.25 (CH2), 38.62 (SCH2), 35.77 (CH). MS ESI: m/z 223.0549 [M + Na]+. Anal. Calcd for C13H12S: C, 77.95; H, 6.04. Found: C, 77.75; H, 6.11. Synthesis of 7a and 9a. A mixture of [Ru]Cl (300 mg, 0.41 mmol), 1a (134 mg, 0.62 mmol), and KPF6 (189 mg, 1.04 mmol) in MeOH (40 mL) was stirred at ambient temperature for 1 day. The crude product containing a mixture of 2a, 3a, and 7a from the reaction was obtained using the same procedure as that described for 2a−4a.

The powder was collected, washed with diethyl ether, and dried under vacuum. The mixture was then dissolved in CH2Cl2 and was passed through an Al2O3 column with hexane/ether/CH2Cl2 as eluent. Collecting the yellow band followed by drying under vacuum resulted in a mixture of 5a and 9a as a yellow powder from deprotonation of 2a and 7a, respectively (388.37 mg; the ratio of 5a and 9a is about 0.3:1.6 and the ratio of major and minor diastereomers of 9a is ca. 1:0.6 from the NMR spectrum). Spectroscopic data of 9a are as follows for the major diastereomer. 1H NMR (C6D6, 400.1 MHz): δ 8.75−7.24 (m, Ph), 4.83 (d, 3JHH = 9.8 Hz, 1H, CγH), 4.44 (s, 5H, Cp), 2.93 (s, 3H, OMe), 2.69−2.57 (m, 3H, SCH2 and CHCH2), 1.95 (m, 1H, CH2), 1.63 (s, 3H, Me). 13C NMR (C6D6, 100.6 MHz): δ 151.79−125.58 (Ph), 113.63 (Cβ), 95.33 (t, 2JCP = 25.1 Hz, Cα), 85.08 (Cp), 76.58 (C(OMe)(Me)), 48.36 (OMe), 47.90 (CH2), 42.28 (SCH2), 36.51 (Cγ), 21.49 (Me). 31P NMR (C6D6, 162.0 MHz): δ 51.58, 50.18 (2 d, 2 Jpp = 37.4 Hz, PPh3). Spectroscopic data are as follows for the minor distereomer. 1H NMR (C6D6, 400.1 MHz): δ 8.75−7.24 (m, Ph), 5.50 (d, 3JHH = 9.3 Hz, 1H, CγH), 4.44 (s, 5H, Cp), 3.15 (s, 3H, OMe), 2.77 (m, 1H, SCH2), 2.69 (m, 1H, CH2), 2.33 (d, 3JHH = 14.5 Hz, 1H, SCH2), 1.54 (m, 1H, CH2), 0.84 (s, 3H, Me). 13C NMR (C6D6, 100.6 MHz): δ 151.79−125.58 (Ph), 114.21 (Cβ), 93.42 (t, 2JCP = 24.8 Hz, Cα), 85.08 (Cp), 73.47 (C(OMe)(Me)), 49.95 (COMe), 46.31 (CH2), 42.62 (SCH2), 34.19 (Cγ), 25.26 (Me). 31P NMR (C6D6, 162.0 MHz): δ 51.53, 50.26 (2 d, 2Jpp = 37.6 Hz, PPh3). MS: m/z: 923.22 [M + 1]+. Single crystals of 9a are obtained from a solution of ether/acetone at 0 °C. Anal. Calcd for C55H50OP2RuS: C, 71.64; H, 5.47. Found: C, 71.31; H, 5.40. A solution of HBF4·Et2O (48%, 0.02 mL, 0.11 mmol) in diethyl ether (20 mL) was added dropwise at 0 °C to a stirred solution of the mixture of 5a and 9a (300 mg) in 10 mL of ether. Immediately, an insoluble solid precipitated but the addition was continued until no further solid was formed. The solution was then decanted, and the pink solid was washed with diethyl ether and dried under vacuum to yield a mixture of 2a and 7a as a pink powder (the ratio of 2a and 7a is about 0.3:1.3 and the ratio of major and minor diastereomers of 7a is ca. 1:0.3. from the 1H NMR spectrum). Spectroscopic data of 7a are as follows for the major diastereomer. 1H NMR (CD2Cl2, 400.1 MHz): δ 7.43−7.00 (m, Ph), 5.41−5.25 (m, 2H, CβH and CγH), 5.19 (s, 5H, Cp), 3.43 (s, 3H, OMe), 3.03 (d, 2JHH = 15.0 Hz, 1H, SCH2), 2.49− 2.39 (m, 2H, SCH2 and CH2), 1.65 (m, 1H, CH2), 1.23 (s, 3H, Me). 13 C NMR (CD2Cl2, 100.6 MHz): δ 346.64 (t, 2JCP = 15.6 Hz, Cα), 149.56−125.01 (Ph), 119.21 (Cβ), 94.49 (Cp), 73.96 (C(OMe)(Me)), 49.34 (OMe), 48.46 (CH2), 40.57 (SCH2), 31.48 (Cγ), 25.30 (Me). 31P NMR (CD2Cl2, 162.0 MHz): δ 44.16, 43.64 (2 d, 2Jpp = 27.0 Hz, PPh3). Spectroscopic data are as follows for the minor distereomer. 1H NMR (CD2Cl2, 400.1 MHz): δ 7.43−7.00 (m, Ph), 5.25 (s, 5H, Cp), 5.00 (m, 1H, CβH), 3.79 (m, 1H, CγH), 3.37 (s, 3H, OMe), 2.68 (m, 2H, SCH2), 2.21 (m, 1H, CH2), 1.76 (m, 1H, CH2), 1.31 (s, 3H, Me). 13C NMR (CD2Cl2, 100.6 MHz): δ 346.54 (t, 2JCP = 15.3 Hz, Cα), 149.56−125.01 (Ph), 118.00 (Cβ), 94.81 (Cp), 81.53 (C(OMe)(Me)), 49.04 (OMe), 45.14 (SCH2), 43.44 (CH2), 32.00 (Cγ), 25.54 (Me). 31P NMR (CD2Cl2, 162.0 MHz): δ 43.84, 43.28 (2 d, 2Jpp = 26.2 Hz, PPh3). MS: m/z 923.22 (M)+. Pure complex 7a was not obtained. Synthesis of 8a. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 1a (88 mg, 0.41 mmol), and KPF6 (126 mg, 0.69 mmol) in MeOH (40 mL) was heated to 50 °C for 1 day. A crude mixture was similarly obtained using the same procedure as for 3a. The mixture in CH2Cl2 (5 mL) was added to stirred hexane (60 mL) to produce an olive precipitate and yellow filtrate. The yellow solution was purified by flash chromatography on a silica gel column (hexane/ether, 9/1) to give the light yellow oil 8a (22.6 mg, 40% yield). Spectroscopic data of 8a are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.36 (d, 2JHH = 7.5 Hz, 1H, Ph), 7.22−7.06 (m, 3H, Ph), 5.82 (m, 1H, CH), 5.65 (m, 1H, CH), 3.75 (br, 1H, CH), 3.30 (s, 3H, OMe), 3.06, 2.83 (2 d, 2JHH = 14.4 Hz, 2H, SCH2), 2.47 (m, 2H, CHCH2, CHCH2), 2.24 (m, 1H, CHCH2), 2.09 (m, 1H, CHCH2). 13C NMR (CDCl3, 100.6 MHz): δ 142.51, 136.58, 132.25, 130.99 (Ph), 128.01 (C), 127.03 (Ph), 126.32 (C), 126.16 (Ph), 74.45 (MeOC), 48.87 (OMe), 43.51 (CH), 41.16 (SCH2), 34.71 (CHCH2), 34.47 (CHCH2). MS ESI: 6384

dx.doi.org/10.1021/om400742x | Organometallics 2013, 32, 6379−6387

Organometallics

Article

1H, CH), 2.10 (d, 4JHH = 2.50 Hz, 1H, CH), 1.03 (s, 3H, Me), 0.94 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 147.49 (C), 112.67 (CH2), 85.72 (C), 77.28 (CH2), 74.59 (CH2), 36.23 (CH2), 70.97 (CH), 34.21 (C), 37.74 (C), 25.31 (Me), 20.92 (Me). MS ESI: m/z 165.1217 [M + H]+. Anal. Calcd for C11H16O: C, 80.44; H, 9.82. Found: C, 80.19; H, 9.93. Synthesis of 10c. Complex 5c (110 mg, 0.13 mmol) and KPF6 (26 mg, 0.14 mmol) were placed in a Schlenk flask, and CH2Cl2 (20 mL) was added under nitrogen. After allyl bromide (17 mg, 0.14 mmol) was added, the resulting solution was stirred for 8 h. A crude mixture was obtained using the same procedure as for 3a. The mixture was extracted with a small volume of CH2Cl2 followed by reprecipitation with 50 mL of diethyl ether. The precipitate thus formed was collected on a glass frit, washed with 1/1 ethyl ether/ hexane, and dried under vacuum to give the pink powder 10c (100 mg, 90% yield), mp 180−181 °C. Spectroscopic data of 10c are as follows. 1 H NMR (CDCl3, 400.1 MHz): δ 7.74−6.79 (m, 49H, Ph), 5.89 (m, 1H, C(C)H), 5.11 (s, 5H, Cp), 5.11 (m, 2H, CH2), 4.63 (s, 1H, CH2), 4.55 (s, 1H, CH2), 4.16, 3.75 (2 d, 2JHH = 14.25 Hz, 2H, OCH2), 3.26, 2.72 (2 d, 2JHH = 12.21 Hz, 2H, OCH2), 3.13 (dd, 2JHH = 16.79 Hz, 3JHH = 6.11 Hz, 1H, CH2), 2.77−2.65 (m, 2H, CH2), 2.25 (m, 1H, CH2), 2.22 (d, 3JHH = 6.11 Hz, 1H, CH), 1.04 (s, 3H, Me), 0.83 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 349.67 (t, 3JCP = 14.04 Hz, Cα), 148.16−111.99 (Cβ, Ph, C(CH2)2, CH2), 94.02 (Cp), 81.98 (OCH2), 74.50 (OCH2), 4.77 (CH), 39.97 (CH2), 38.33 (C), 27.56 (CH2), 26.46 (Me), 21.00 (Me). 31P NMR (CDCl3, 162.0 MHz): δ 41.38, 40.68 (2 d, 2JPP = 27.68 Hz, PPh3). MS ESI: m/z 895.28 [M]+. Anal. Calcd for C55H55F6OP3Ru: C, 63.52; H, 5.33. Found: C, 63.19; H, 5.55. Single crystals of 10c were obtained from an ether/CH2Cl2 solution at 0 °C. Synthesis of 10c′. Complex 10c′ (120 mg, 93% yield) was similarly prepared from 5c (130 mg, 0.15 mmol), KPF6 (31 mg, 0.18 mmol), and methyl iodide (26 mg, 0.18 mmol), mp 174−176 °C. Spectroscopic data of 10c′ are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.77−6.93 (m, 42H, Ph), 5.14 (s, 5H, Cp), 4.63 (s, 1H,  CH2), 4.41 (s, 1H, CH2), 4.18, 3.87 (2 d, 2JHH = 14.18 Hz, 2H, OCH2), 3.34, 2.92 (2 d, 2JHH = 12.02 Hz, 2H, OCH2), 2.49 (t, 3JHH = 12.91 Hz, 1H, CH), 2.20, 1.86 (2 d, 2JHH = 11.57 Hz, 2H, CH2), 1.76 (s, 3H, Me), 1.04 (s, 3H, Me), 0.93 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 350.81 (t, 3JCP = 15.19 Hz, Cα), 148.22 (C(CH2)2), 135.23−128.42 (Cβ, Ph), 112.23 (CH2), 93.93 (Cp), 81.00 (OCH2), 74.59 (OCH2), 43.85 (CH2), 40.15 (CH2), 36.34 (C), 27.12 (Me), 21.65 (Me), 7.98 (Me). 31P NMR (CDCl3, 162.0 MHz): δ 42.43, 41.44 (2 d, 2JPP = 26.42 Hz, PPh3). MS ESI: m/z 869.26 [M]+. Anal. Calcd for C53H53F6OP3Ru: C, 62.78; H, 5.27. Found: C, 63.01; H, 5.13. Synthesis of 8c. A solution of 1c (65 mg, 0.36 mmol) and [Ru]NCCH3+ (78 mg, 0.11 mmol) in 2/1 CHCl3/MeOH cosolvent was heated to 50 °C for 1 day. A crude mixture was similarly obtained using the same procedure as for 6c. Then the mixture was added to diethyl ether (10 mL) to produce a pale orange precipitate and filtrate. The precipitate was collected, washed with diethyl ether, and dried under vacuum to give [Ru]NCCH3+. The filtrate was dried under vacuum and the crude product purified by flash chromatography (silica gel, hexanes/EtOAc 10/1) to afford the light yellow oil 8c (55 mg, 77%). Spectroscopic data for 8c are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 5.81 (m, 1H, C(C)H), 5.70 (m, 1H, C(C)H), 4.12, 3.19 (2 d, 2JHH = 14.07 Hz, 2H, OCH2), 3.44, 3.11 (2 d, 2JHH = 12.27 Hz, 2H, OCH2), 3.28 (s, 3H, OMe), 2.62 (2 d, 2JHH = 12.82 Hz, 1H, CH2), 2.12 (m, 1H, CH2), 1.92 (m, 1H, CH2), 2.05 (br, 1H, CH), 1.43 (dd, 2JHH = 12.82 Hz, 3JHH = 7.31 Hz, 1H, CH2), 1.14 (s, 3H, Me), 0.81 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 128.96 ( C), 126.25 (C), 83.09 (OCH2), 81.60 (OCH2), 78.42 (C), 49.29 (OMe), 44.46 (CH), 38.01 (C), 36.57 (CH2), 28.91 (CH2), 26.67 (Me), 23.75 (Me). MS ESI: m/z 197.8102 [M + H]+. Anal. Calcd for C12H20O2: C, 73.43; H, 10.27. Found: C, 73.28; H, 10.33. Synthesis of 8c′. Compound 8c′ (49 mg, 70% yield) was similarly prepared from 1c (61 mg, 0.33 mmol) and [Ru]NCCH3+ (73 mg, 0.10 mmol) in 2/1 CHCl3/EtOH cosolvent, and the solution was heated to 50 °C for 1 day. Spectroscopic data of 8c′ are as follows. 1H NMR

m/z 255.0812 [M + Na]+. Anal. Calcd for C14H16OS: C, 72.37; H, 6.94. Found: C, 72.13; H, 7.03. Synthesis of 8a′. Compound 8a′ (30 mg, 42% yield) was similarly prepared from [Ru]Cl (200 mg, 0.27 mmol), 1a (88 mg, 0.41 mmol), and KPF6 (126 mg, 0.69 mmol) in EtOH (40 mL) at 50 °C. Spectroscopic data of 8a′ are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 7.35 (d, 2JHH = 8.3 Hz, 1H, Ph), 7.21−7.05 (m, 3H, Ph), 5.82 (m, 1H, CH), 5.63 (m, 1H, CH), 3.75 (br, 1H, CH), 3.53 (m, 2H, OCH2), 3.05, 2.84 (2 d, 2JHH = 14.5 Hz, 2H, SCH2), 2.46 (m, 2H, CHCH2, CHCH2), 2.26 (m, 1H, CHCH2), 2.10 (m, 1H, CHCH2), 1.21 (t, 3JHH = 7.03 Hz, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 142.50, 136.70, 132.34, 131.06 (Ph), 127.95 (C), 127.09 (Ph), 126.60 (C), 126.23 (Ph), 74.45 (CH2OC), 56.36 (OCH2), 43.65 (CH), 41.86 (SCH2), 35.54 (CHCH2), 35.08 (CHCH2), 16.30 (Me). MS ESI: m/z 269.0967 [M + Na]+. Anal. Calcd for C15H18OS: C, 73.13; H, 7.36. Found: C, 72.79; H, 7.48. Synthesis of 2c. A mixture of [Ru]Cl (250 mg, 0.34 mmol), 1c (61 mg, 0.34 mmol), and NH4PF6 (81 mg, 0.50 mmol) in CH2Cl2 (20 mL) was stirred at ambient temperature for 1 day. A crude mixture was obtained using the same procedure as for 3a. The mixture was extracted with a small volume of CH2Cl2 followed by reprecipitation by addition to 50 mL of diethyl ether. The precipitate thus formed was collected in a glass frit, washed with 1/1 diethyl ether/hexane, and dried under vacuum to give the deep yellow product 2c. Purification by deprotonation of 2c with NaOMe/MeOH described below gave 5c, which regenerated pink powder 2c in HBF4 (210 mg, 70% yields), mp: 156−158 °C. Spectroscopic data of 2c are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 6.94−7.66 (m, 34H, Ph), 5.13 (s, 5H, Cp), 4.57 (d, 3JHH = 10.47 Hz, 1H, CβH), 4.76 (s, H, CH2), 4.54 (s, H, CH2), 4.12 (t, 3JHH = 15.11 Hz, 2H, CH2), 3.30, 3.16 (2 d, 2JHH = 12.71 Hz, 2H, CH2), 2.35 (m, 1H, CH2), 2.15 (m, 1H, CH2), 0.99 (s, 3H, Me), 0.97 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 343.94 (t, 3JCP = 15.21 Hz, Cα), 147.04 (C), 128.21−134.61 (Ph), 115.64 (Cβ), 112.92 (CH2), 94.32 (Cp), 76.80 (CH2), 74.43(CH2), 38.69 (CH2), 44.23 (CH), 38.16(Me), 26.09 (Me), 21.90 (Me). 31P NMR (CDCl3, 162.0 MHz): δ 43.24, 43.02 (2 d, 2JPP = 26.35 Hz, PPh3). MS ESI: m/z 855.25 [M]+. Anal. Calcd for C52H51BF4OP2Ru: C, 66.32; H, 5.46. Found: C, 66.68; H, 5.71. Synthesis of 5c. A mixture of 2c (85 mg, 0.099 mmol) and NaOMe (6.0 mg, 0.11 mmol) in MeOH (30 mL) was stirred for 5 min at room temperature. Then, the solvent was removed under vacuum and the residue was extracted with diethyl ether (20 mL). The yellow filtrate was passed through a neutral Al2O3 column to remove the insoluble salts. Collecting the yellow band followed by drying under vacuum resulted in THE yellow powder 5c (77 mg, 90% yield), mp 179−181 °C. Spectroscopic data of 5c are as follows. 1H NMR (C6D6, 500.2 MHz): δ 7.69−7.73 (m, 12H, Ph), 6.92−6.98 (m, 18H, Ph), 5.00 (s, 1H, CH2), 4.79 (s, 1H, CH2), 4.39 (s, 5H, Cp), 4.59, 4.26 (2 d, 2JHH = 14.17 Hz, 2H, OCH2), 3.90, 3.33 (2 d, 2JHH = 11.81 Hz, 2H, OCH2), 2.86 (m, 2H, CH2), 2.76 (m, 1H, CγH), 1.51 (s, 3H, Me), 1.22 (s, 3H, Me). 13C NMR (C6D6, 125.8 MHz): δ 127.39−140.12 (Ph), 113.45 (Cβ), 92.69 (t, 2JCP = 24.43 Hz, Cα), 85.44 (Cp), 110.72 (CH2), 151.45 (C), 78.96 (CH2), 75.42 (CH2), 39.64 (CH2), 26.63 (Me), 21.74 (Me), 39.59 (C). 31P NMR (C6D6, 162.0 MHz): δ 51.94 (s, PPh3). MS ESI: m/z 855.25 [M + 1]+. Anal. Calcd for C52H50OP2Ru: C, 73.14; H, 5.90. Found: C, 72.85; H, 5.73. Synthesis of 6c. A solution of 2c (150 mg, 0.17 mmol) in CDCl3 (1.5 mL) and CH3CN (0.15 mL) in a tube was heated to 60 °C for 1 day. The solvent was removed under vacuum, CH2Cl2 (1.0 mL) was used to extract the product, and the mixture was filtered through Celite to remove the insoluble precipitate. Then the filtrate was added to diethyl ether (6 mL) to produce a pale orange precipitate, which was collected by filtration, washed with diethyl ether, and dried under vacuum to give [Ru]NCCH3+. The filtrate was dried under vacuum and the crude product purified by flash chromatography (silica gel, hexanes/EtOAc 10/1) to afford the light yellow oil 6c (26 mg, 92%). Spectroscopic data for 6c are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 4.92 (s, 1H, CH2), 4.83 (s, 1H, CH2), 4.23, 4.13 (2 d, 2 JHH = 14.51 Hz, 2H, OCH2), 3.35, 3.13 (2 d, 2JHH = 12.51 Hz, 2H, OCH2), 2.48 (m, 2H, CH2), 2.23 (dt, 3JHH = 9.54 Hz, 4JHH = 2.50 Hz, 6385

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Organometallics

Article

MHz): δ 49.62, 48.50 (dd, 2Jpp = 36.5 Hz, 5JPP = 5.1 Hz, PPh3), 15.85 (t, 5Jpp = 5.1 Hz, CPPh3). MS ESI: m/z 1139.27 [M]+. Anal. Calcd for C71H60F6P4RuS: C, 66.40; H, 4.71. Found: C, 66.21; H, 4.59. Spectroscopic data of 13b are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 9.67 (s, 1H, CγH), 7.70−6.99 (m, 34H, Ph), 5.92 (m, 1H,  CH), 5.18 (s, 1H, CH2), 5.14 (s, 5H, Cp), 5.10 (s, 1H, CH2), 3.67 (d, 3JHH = 6.0 Hz, 2H, CH2). 31P NMR (CDCl3, 162.0 MHz): δ 46.55 (s, PPh3). MS ESI: m/z 877.18 [M]+. Anal. Calcd for C53H45F6P3RuS: C, 62.29; H, 4.44. Pure complex 13b was not obtained. Synthesis of 3b. A mixture of [Ru]Cl (200 mg, 0.27 mmol), 1b (83 mg, 0.41 mmol), and NH4PF6 (111.7 mg, 1.03 mmol) in CH2Cl2 (40 mL) was stirred at 40 °C for 1 day. The crude mixture was obtained using the same procedure as for 3a. The powder was collected, washed with diethyl ether, and dried under vacuum to give an olive powder (188 mg) containing mostly 3b (ca. 78% yield). Attempts to purify 3b failed. Spectroscopic data of 3b are as follows. 1 H NMR (CDCl3, 400.1 MHz): δ 7.77−6.86 (m, Ph), 5.83 (d, 2JHP = 36.2 Hz, 1H, CHPPh3), 5.72 (m, 1H, CH), 5.01 (s, 1H, CH2), 4.95 (s, 1H, CH2), 4.89 (s, 1H, CH), 4.64 (s, 5H, Cp), 3.76 (m, 1H, CH2), 3.58 (m, 1H, CH2), 3.29 (br, 1H, OH). 13C NMR (CDCl3, 100.6 MHz): δ 233.47 (br, Cα), 160.36−127.49 (Ph, CH), 120.81 (CH2), 100.95 (br, CHPPh3), 81.64 (Cp), 78.15 (CH), 53.72 (CH2). 31P NMR (CDCl3, 162.0 MHz): δ 56.26 (br, PPh3), −5.50 (br, PPh3). MS ESI: m/z 895.02 [M]+. Anal. Calcd for C53H47F6OP3RuS: C, 61.21; H, 4.56. Pure complex 3b was not obtained. Synthesis of 4b. Complex 4b (239 mg, 80% yield) was prepared from [Ru]NCCH3+ (300 mg, 0.34 mmol), 1b (104 mg, 0.51 mmol), and NH4PF6 (166 mg, 1.02 mmol) in CH2Cl2 (40 mL), mp 184−186 °C, using a procedure similar to that for 4a. Spectroscopic data of 4b are as follows. 1H NMR (CDCl3, 400.2 MHz): δ 15.03 (t, 3JPH = 10.51 Hz, 1H, CαH), 8.05−6.96 (m, Ph), 5.54 (m, 1H, CH), 5.15 (s, 5H, Cp), 4.72 (d, 3JHH = 9.4 Hz, 1H, CH2), 4.46 (d, 3JHH = 17.2 Hz, 1H, CH2), 2.90 (s, 2H, CH2). 13C NMR (CDCl3, 100.6 MHz): δ 280.19 (t, 2JCP = 12.3 Hz, Cα), 162.12−123.75 (Ph, C), 117.31 (CH2), 94.64 (Cp), 31.66 (CH2). 31P NMR (CDCl3, 162.0 MHz): δ 45.33 (s, PPh3). MS ESI: m/z 877.18 [M]+. Anal. Calcd for C53H45F6P3RuS: C, 62.29; H, 4.44. Found: C, 62.57; H, 4.53. Synthesis of 11b. Compound 11b (36 mg, 88% yield), similar to the preparation of 11a from 4a, was prepared from 4b (200 mg, 0.20 mmol), NEt3 (5 mL), and CH3CN (10 mL) in air. Spectroscopic data for 11a are as follows. 1H NMR (CDCl3, 400.2 MHz): δ 10.21 (s, 1H, CHO), 7.96 (d, 3JHH = 8.1 Hz, 1H, Ph), 7.86 (d, 3JHH = 8.1 Hz, 1H, Ph), 7.50 (t, 3JHH = 7.1 Hz, 1H, Ph), 7.43 (t, 3JHH = 7.4 Hz, 1H, Ph), 6.87 (m, 1H, CH), 6.29 (m, 1H, CH), 2.06 (m, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 185.07 (CHO), 144.58, 141.88, 138.72, 138.07 (Ph), 137.34 (CH), 128.28, 124.94, 124.64, 123.27 (Ph), 121.42 (CH), 19.30 (Me). MS ESI: m/z 203.0503 [M + H]+. Anal. Calcd for C12H10OS: C, 71.25; H, 4.98. Found: C, 71.07; H, 5.05. Single-Crystal X-ray Diffraction Analyses. Single crystals of complexes 5a, 9a, and 10c suitable for X-ray diffraction study were grown as mentioned above. Single crystals were glued to a glass fiber and mounted on a SMART CCD diffractometer. The diffraction data were collected by using 3 kW sealed-tube Mo Kα radiation (T = 295 K). The exposure time was 5 s per frame (Siemens area detector absorption). SADABS22 absorption correction was applied, and decay was negligible. Data were processed, and the structure was solved and refined by the SHELXTL23 program. Hydrogen atoms were placed geometrically by using a riding model with thermal parameters set to 1.2 times that for the atoms to which they are attached and 1.5 times for the methyl hydrogen atoms.

(CDCl3, 400.1 MHz): δ 5.80 (m, 1H, C(C)H), 5.70 (m, 1H,  C(C)H), 4.11, 3.22 (2 d, 2JHH = 13.96 Hz, 2H, OCH2), 3.53 (m, 2H, OCH2), 3.43, 3.11 (2 d, 2JHH = 12.16 Hz, 2H, OCH2), 2.61 (d, 2JHH = 12.77 Hz, 1H, CH2), 2.14 (m, 1H, CH2), 1.93 (m, 1H, CH2), 2.04 (br, 1H, CH), 1.47 (dd, 2JHH = 13.30 Hz, 3JHH = 7.48 Hz, 1H, CH2), 1.15 (t, 3JHH = 7.06 Hz, 3H, Me), 1.13 (s, 3H, Me), 0.81 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 128.94 (C), 126.34 (C), 83.08 (OCH2), 81.60 (OCH2), 78.42 (C), 49.29 (OMe), 44.46 (CH), 38.01 (C), 36.57 (CH2), 28.91 (CH2), 26.67 (Me), 23.75 (Me). MS ESI: m/ z 211.8102 [M + H]+. Anal. Calcd for C13H22O2: C, 74.24; H, 10.54. Found: C, 73.94; H, 10.41. Synthesis of 8c″. Compound 8c″ (30 mg, 43% yield) was similarly prepared from 1c (57 mg, 0.31 mmol) and [Ru]NCCH3+ (68 mg, 0.093 mmol) in 2/1 CHCl3/i-PrOH cosolvent, and the solution was heated to 50 °C for 1 day. Spectroscopic data of 8c″ are as follows. 1 H NMR (CDCl3, 400.1 MHz): δ 5.78 (m, 1H, C(C)H), 5.68 (m, 1H, C(C)H), 4.11, 3.23 (2 d, 2JHH = 13.95 Hz, 2H, OCH2), 3.94 (septet, 3JHH = 6.18 Hz, 1H, CH), 3.44, 3.12 (2 d, 2JHH = 12.12 Hz, 2H, OCH2), 2.58 (d, 2JHH = 12.68 Hz, 1H, CH2), 2.12 (m, 1H, CH2), 1.91 (m, 1H, CH2), 2.03 (br, 1H, CH), 1.51 (dd, 2JHH = 12.51 Hz, 3 JHH = 7.33 Hz, 1H, CH2), 1.14 (s, 3H, Me), 0.81 (s, 3H, Me), 1.13 (s, 6H, 2 Me). 13C NMR (CDCl3, 100.6 MHz): δ 128.86 (C), 126.38 (C), 83.16 (OCH2), 83.07 (OCH2), 79.03 (C), 64.23 (OCH), 44.53 (CH), 37.98 (C), 37.64 (CH2), 31.07 (CH2), 26.70 (Me), 25.54 (Me), 25.33 (Me), 23.76 (Me). MS ESI: m/z 247.1661 [M + Na]+. Anal. Calcd for C14H24O2: C, 74.95; H, 10.78. Found: C, 74.74; H, 10.86. Synthesis of 11a. In a flask containing 4a (300 mg, 0.29 mmol) were added NEt3 (5 mL) and CH3CN (10 mL) in air. The mixture was stirred at room temperature for 1 day. The originally brown solution turned dark brown. Then the solvent was removed under vacuum. The residue was purified by flash chromatography (silica gel, hexane/ether 4/1) to afford the light yellow oil 11a (52.0 mg, 83%). Spectroscopic data for 11a are as follows. 1H NMR (CDCl3, 400.1 MHz): δ 10.30 (s, 1H, CHO), 7.88 (m, 2H, Ph), 7.49 (m, 1H, Ph), 7.41 (m, 1H, Ph), 4.88 (s, 1H, CH2), 4.67 (s, 1H, CH2), 3.95 (s, 2H, CH2), 1.81 (s, 3H, Me). 13C NMR (CDCl3, 100.6 MHz): δ 184.08 (CHO), 144.27, 142.86, 142.24, 139.71, 138.65, 128.25, 124.84, 142.38, 123.32 (Ph and C), 113.14 (CH2), 34.58 (CH2), 22.74 (Me). MS ESI: m/z 217.0687 [M + H]+. Anal. Calcd for C13H12OS: C, 72.19; H, 5.59. Found: C, 71.97; H, 5.68. Synthesis of 12b and 13b. A mixture of [Ru]Cl (300 mg, 0.41 mmol), 1b (109 mg, 0.53 mmol), KPF6 (189 mg, 1.03 mmol), and PPh3 (323 mg, 1.23 mmol) in MeOH (40 mL) was stirred at ambient temperature for 1 day. The crude mixture was obtained using the same procedure as for 3a. The crude mixture in 5 mL of CH2Cl2 was added to diethyl ether to produce a yellow precipitate, which was filtered and dried under vacuum to give the yellow powder 12b (491 mg, 95% yield), mp 148−150 °C. Compound 12b (250 mg, 0.20 mmol) was treated with excess K2CO3 (81 mg, 0.58 mmol) in 20 mL of MeOH at room temperature for 15 min under nitrogen. Then dimethyl acetylenedicarboxylate (DMAD; 28 mg, 0.19 mmol) was added, and the mixture was stirred for 10 min. The resulting yellow solution was reduced to ca. 5 mL under vacuum to produce a precipitate. The precipitate thus formed was collected on a glass frit, and hexane was used to wash the precipitate to yield a yellow solution, which was dried and redissolved in diethyl ether. Then a solution of HBF4·Et2O (48%, 0.02 mL, 0.11 mmol) in diethyl ether (20 mL) was added dropwise at 0 °C to this yellow solution. Immediately, insoluble solid precipitated but the addition was continued until no further solid was formed. The solution was then decanted, and the red solid was washed with diethyl ether and dried in vacuo to yield the red powder 13b (127 mg, 78%). Spectroscopic data of 12b are as follows. 1H NMR (d-acetone, 400.1 MHz): δ 7.92−7.06 (m, 49H, Ph), 6.78 (d, 3JHH = 17.9 Hz, 1H, CγH), 5.63 (m, 1H, CH), 5.00 (d, 3JHH = 17.2 Hz, 1H, trans CH2), 4.93 (d, 3JHH = 10.2 Hz, 1H, cis CH2), 4.31 (s, 5H, Cp), 3.40 (m, 1H, CH2), 3.16 (m, 1H, CH2). 13C NMR (d-acetone, 100.6 MHz): δ 138.75−133.66 (Ph), 133.04 (CH), 132.81−127.39 (Ph), 118.68 (Cβ), 117.95 (CH2), 97.96 (d, 2JCP = 9.4 Hz, Cα), 84.97 (Cp), 38.29 (d, 1JCP = 46.9 Hz, Cγ), 37.48 (CH2). 31P NMR (d-acetone, 162.0

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S Supporting Information *

CIF files, tables, and figures giving crystallographic data for 5a, 9a, and 10c and NMR spectra of new complexes. This material is available free of charge via the Internet at http://pubs.acs.org. 6386

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Organometallics

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AUTHOR INFORMATION

Corresponding Author

*Y.C.L.: e-mail, [email protected]; fax, (+886) 233668670. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank the National Science Council of Taiwan for financial support. REFERENCES

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dx.doi.org/10.1021/om400742x | Organometallics 2013, 32, 6379−6387