Homogeneous Sc (OTf) 3-Catalyzed Direct Allylation Reactions of

The direct substitution reaction of a hydroxyl group in alcohols with allylsilanes is one of the most ..... Experimental Section. ARTICLE .... 2H), 2...
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Article Cite This: ACS Omega 2018, 3, 18885−18894

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Homogeneous Sc(OTf)3‑Catalyzed Direct Allylation Reactions of General Alcohols with Allylsilanes Yuanjun Di,† Tsutomu Yoshimura,† Shun-ichi Naito,† Yu Kimura,‡ and Teruyuki Kondo*,† †

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, and ‡Center for the Promotion of Interdisciplinary Education and Research, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan

ACS Omega 2018.3:18885-18894. Downloaded from pubs.acs.org by 5.189.207.244 on 01/01/19. For personal use only.

S Supporting Information *

ABSTRACT: Homogeneous Sc(OTf)3 used in nitromethane showed excellent catalytic activity for the direct allylation reactions of general alcohols including benzylic, propargylic, allylic, and some aliphatic alcohols with allyltrimethylsilane under mild and neutral reaction conditions. Metal-free β-silylsubstituted carbocations are intermediates generated by the highly oxophilic Sc(OTf)3-assisted rapid removal of a hydroxyl group in alcohols, which is supported by the result that allylation of (R)-1-(naphthalen-2-yl)ethan-1-ol with allytrimethylsilanes using the Sc(OTf)3 catalyst combined with (R)- or (S)-[1,1′binaphthalene]-2,2′-diol ligands gave only racemic 2-(pent-4-en-2-yl)naphthalene in quantitative yield. The present study resolves the argument about the uncertain catalytic activity of Sc(OTf)3.

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INTRODUCTION Rare-earth-metal triflates are promising Lewis acids that promote the fundamental and synthetically important carbon−carbon bond-forming reactions, including the aldol reaction, Mannich-type reaction, Diels−Alder reaction, Friedel−Crafts reaction, and 1,3-dipolar cycloaddition reaction even in water1 and ionic liquid solvents.2 The direct substitution reaction of a hydroxyl group in alcohols with allylsilanes is one of the most atom-efficient carbon−carbon bond-forming reactions because it does not require the prior conversion of a hydroxyl group in alcohols into a good leaving group such as acetate, trifluoroacetate, carbonates, or ethers/acetals using catalysts (Lewis acids (FeCl3, Fe(OTf)3, InCl3/I2, and B(C6F5)3), Brønsted acids (2,4-dinitrobenzenesufonic acid and o-benzenedisulfonimide), and late transition metals ([RhCl(η4-1,5-cyclooctadiene)]2)).3 Since Cella reported the first direct allylation of benzylic and allylic alcohols with allylsilanes in the presence of an excess amount of BF3·Et2O in 1982,4 [(Et2NSF2)BF4] (XtalFluorE)-5 and TiCl46-mediated reactions have been reported. The same reaction proceeded smoothly with the use of a catalytic amount of HN(SO2F)27 and I2/XB donor.8 Besides, many Lewis acid-catalyzed direct allylation reactions of mainly secondary and tertiary benzylic alcohols with allylsilanes have been developed, in which InCl3,9 InCl3/Me3SiX,10 InBr3,11 ZrCl4,12 Ca(NTf2)2/Bu4NBF4,13 FeCl3·6H2O in water,14 BiCl3,15 Bi(OTf)3 in ionic liquid,16 and solid acids such as H-montmorillonite,17 Sn-montmorillonite,18 and phosphomolybdic acid19 are used as a catalyst. However, some of the reported reactions have several drawbacks such as variable yields, a prolonged reaction time from minutes to hours, the need for cooling (−78 °C) or heating (100 °C) under an inert atmosphere, difficult work up, stoichiometric or excess amount of some Lewis acids and Brønsted acids, and the formation of © 2018 American Chemical Society

significant amounts of byproducts such as ethers through the intermolecular dehydration of benzylic alcohols. In this context, the development of more efficient catalysts for the direct allylation of general alcohols with allylsilanes remains attractive. De and Gibbs reported the low catalytic activities of both Sc(OTf)3 and ScCl3 for the direct allylation of benzhydrol with allyltrimethylsilanes.15 Independently, Yasuda and Baba also reported the low catalytic activity of Sc(OTf)3 for the same reaction,9 whereas Yadav and co-workers reported that Sc(OTf)3 showed catalytic activity for the related allylation of both secondary propargylic and allylic alcohols with allylsilanes.20 On the other hand, we recently developed a novel synthesis of 4(3H)-quinazolinones by the Yb(OTf)3catalyzed cyclo-condensation of 2-aminobenzamides with carboxamides21 or 1,3-dicarbonyl compounds.22 As a continuation of our study on the development of novel and unique rare-earth-metal triflate-catalyzed synthetic organic transformations, we considered that the low solubility and homogeneity of Yb(OTf)3 and Sc(OTf)3 in CH2Cl2 may highly affect their catalytic activity as well as the reproducibility of the reactions. Because of the above uncertain catalytic activity of Sc(OTf)3, in the present study, we clarified the extremely high catalytic activity of Sc(OTf)3 under the most suitable reaction conditions.

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RESULTS AND DISCUSSION We re-examined the catalytic activities of general metal triflates including rare-earth-metal triflates in several solvents in the model allylation of 1-phenylethan-1-ol 1a with allyltrimethylsiReceived: September 24, 2018 Accepted: November 27, 2018 Published: December 31, 2018 18885

DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894

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reason why previous studies concluded that Sc(OTf)3 has low catalytic activity is the low solubility of Sc(OTf)3 in CH2Cl2, leading to low reproducibility. The effect of the solvent was examined (entries 12, and 14−19), and the results showed that nitromethane (CH3NO2) was the best solvent for Sc(OTf)3 catalyst to give 3a, quantitatively, with good reproducibility and acceleration of the reaction (entry 12). Consequently, Sc(OTf)3 is the best catalyst for the direct allylation of 1a with 2a in a highly polar solvent, CH3NO2, to give 3a, quantitatively with good reproducibility. Primary, secondary, and tertiary benzylic alcohols as well as 2-thiophenemethanol were applicable to the present Sc(OTf)3catalyzed direct allylation reaction with allyltrimethylsilane 2a in CH3NO2 (Table 2).24 Under optimum and neutral reaction conditions, the present allylation reactions of secondary benzylic alcohols 1a−i with 2a went to completion at room temperature within 10 min, and the desired products 3a−i were obtained in high yield without the formation of byproducts such as α-methylstyrene, its dimers, or indans.4,25 Direct allylation of tertiary benzylic alcohols with 2a gave (2methylpent-4-en-2-yl)benzene 4a and but-3-ene-1,1,1-triyltribenzene 4b bearing a quaternary carbon center in respective yield of 94%. Primary benzylic alcohols as well as thiophen-2ylmethanol were also allylated, smoothly, at 80 °C for 10 min to give 5a−f in high yield, where electron-donating substituents (Me and MeO) on a phenyl ring had a positive effect (Table 3). This result suggests that the present reaction proceeds via a benzylic cation intermediate (vide infra). In addition, the direct allylation of primary, secondary, and tertiary propargylic alcohols with 2a proceeded to give the corresponding hex-5-en-1-yn-1-ylbenzenes 6a−d in good to high yield (Table 4). Diallylation of two hydroxyl groups in 4methyl-1-phenylpent-2-yne-1,4-diol with 2a also proceeded, successfully, and after the reaction at room temperature for 24 h, the corresponding diallylated product, (7,7-dimethyldeca1,9-dien-5-yn-4-yl)benzene 6e, was obtained in 78% yield (eq 1). 1,5-Dienes such as 3-allylcyclohex-1-ene 7a and (E)-hexa1,5-diene-1,3-diyldibenzene 7b were obtained in respective yields of 65 and 83% by the Sc(OTf)3-catalyzed direct allylation of cyclohex-2-en-1-ol and (E)-1,3-diphenylprop-2en-1-ol with 2a, respectively. Surprisingly, aliphatic alcohols such as 1-adamantanol, cyclohexanol, and cyclopentanol were also allylated with 2a at 80 °C for 3 h to give the corresponding allylated products 8a−c in moderate-to-high yield (Table 5). In addition, the present allylation of 2-phenylethan-1-ols with 2a gave only linear products 8d−g in high yields with high selectivity (vide infra).

lane 2a to give pent-4-en-2-ylbenzene 3a at room temperature for 3 h under an argon atmosphere. The results are summarized in Table 1, and among the catalysts examined, Sc(OTf)3 gave the desired 3a in 86% yield (Table 1, entry 1). Table 1. Catalytic Activity and Optimization of Reaction Conditionsa

entry

Lewis acid

solvent

yield of 3ab (%)

1 2 3 4 5 6 7 8 9 10 11 12 13d 14 15 16 17 18 19

Sc(OTf)3 Yb(OTf)3 Y(OTf)3 Fe(OTf)3 Fe(OTf)2 Ni(OTf)2 Cu(OTf)2 Zn(OTf)2 Sc(OAc)3 ScCl3 FeCl3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3 Sc(OTf)3

CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH2Cl2 CH3NO2 CH3NO2 ClCH2CH2Cl CH3CN toluene hexane THF 1,4-dioxane

86 0c 0c 85 7 3 2 0c 0c 0c 33 >99 (90) 30 73 10 0c 0c 0c 0c

a 1a (1.0 mmol), 2a (3.0 mmol), and catalyst (0.050 mmol, 5.0 mol %) in a solvent (2.0 mL) at room temperature for 3 h. bGas−liquid chromatography yield (isolated yield). cNo reaction occurred, and 1a was completely recovered. dWhen the amount of 2a was reduced from 3.0 to 2.0 mmol, di(1-phenylethan-1-yl)ether from dehydration of two molecules of 1a was obtained in ca. 30% yield as only byproduct. No formation of styrene, dehydrated product of 1a, was confirmed by careful GC−MS analysis (vide infra).

In sharp contrast, no reaction occurred with Sc(OAc)3 or ScCl3 (entries 9 and 10) probably because of the weak coordination ability as well as the lower electron-withdrawing effects of chloro- and acetato-ligands compared to a triflatoligand.21,22 Fe(OTf)3 also showed high catalytic activity to give 3a in 85% yield (entry 4), whereas less Lewis acidic metal triflates including Fe(OTf)2 showed almost no catalytic activity (entries 2, 3, 5−8).23 We consider that the most important

Table 2. Sc(OTf)3-Catalyzed Direct Allylation of Secondary Benzylic Alcohols with 2a in CH3NO2

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Table 3. Sc(OTf)3-Catalyzed Direct Allylation of Tertiary and Primary Benzylic Alcohols with 2a in CH3NO2

Table 4. Sc(OTf)3-Catalyzed Direct Allylation of Primary, Secondary, and Tertiary Propargylic Alcohols with 2a

Table 5. Sc(OTf)3-Catalyzed Direct Allylation of Aliphatic Alcohols with 2a

highly stabilized by the neighboring phenyl group to form two isomeric intermediates A and B.26 However, another possible carbocation intermediate C is not involved in the present reaction, because hex-5-en-2-ylbenzene generated from the intermediate C was not obtained at all (vide infra). At the lower reaction temperature such as room temperature, the rate of the allylation of the intermediates A and/or B with 2a to 9a is faster than that of the allylation of the open-chain 1phenylpropan-1-yl cation, which was formed by the rearrange-

To investigate the mechanism, Sc(OTf)3-catalyzed allylation of 1-phenylpropan-2-ol with 2a was examined, and a mixture of (2-methylpent-4-en-1-yl)benzene 9a and hex-5-en-3-ylbenzene 3f was obtained in a total isolated yield of 47% (9a/3f = 55/ 45) (eq 2). The mechanism of the reaction depicted in eq 2 is as follows (Scheme 1). The removal of a hydroxyl group in the starting 1phenylpropan-2-ol by Sc(OTf)3 catalyst occurs to give 1phenylpropan-2-yl cation, which may rapidly be captured and 18887

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Scheme 1. Possible Mechanism of the Reaction Depicted in Eq 2

Scheme 2. Possible Mechanism for Selective Formation of the Linear Allylated Products 8d−g from 2-Arylethan-1-ol

ment (1,2-hydride shift) of 1-phenylpropan-2-yl cation, with 2a to 3f. This mechanism can explain that the present reaction gave the mixture of 9a and 3f, and the yield of 9a was higher than that of 3f (Scheme 1).

On the other hand, the Sc(OTf)3-catalyzed direct allylation of 2-arylethan-1-ols with 2a gave only linear allylated products, 8d−8g. This reaction also starts from the removal of a hydroxyl group in the starting 2-arylethan-1-ols by Sc(OTf)3 18888

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catalyst occurs to give a 2-arylethan-1-yl cation, which may rapidly be captured and highly stabilized by the neighboring phenyl group to form three isomeric intermediates D, E, and D′ (D = D′). In sharp contrast to the phenonium ion intermediate B in Scheme 1, the rapid Sc(OTf)3-catalyzed ring-opening allylation of the cyclopropane in E with 2a from either site, prior to the formation of the open-chain 1arylethan-1-yl cation intermediate through the slow rearrangement (1,2-hydride shift) of 2-arylethan-1-yl cation intermediate, would proceed to give the linear allylated products 8d−8g without the formation of the branched allylated products (vide supra) (Scheme 2).27 The reaction of 1-phenylethan-1-ol 1a with (1-chloroallyl)trimethylsilane 2b gave (5-chloropent-4-en-2-yl)benzene 10 in 66% yield (E/Z = 69/31), in which the reaction occurred at the sterically less hindered γ-allylic carbon atom in 2b (eq 3). In addition, Sc(OTf)3-catalyzed allylation of (R)-1-(naphthalen-2-yl)ethan-1-ol (>99% ee) with 2a in either the presence or the absence of chiral ligands such as (R)- or (S)-[1,1′-binaphthalene]-2,2′-diol and (R)- or (S)-[1,1′binaphthalene]-2,2′-diyl bis(trifluoromethanesulfonate) gave only racemic product 3g, quantitatively, without a decrease in catalytic activity (eq 4).28 These results indicate that the present reaction proceeds via a metal-free carbocation intermediate, generated from the starting (R)-1-(naphthalen-2-yl)ethan-1-ol and subsequent allylation with 2a occurs according to an SN1-type mechanism. As the control experiments, we examined the reaction of styrene (1.0 mmol), with 2a (3.0 mmol) in the presence of Sc(OTf)3 catalyst (0.050 mmol) in CH3NO2 (2.0 mL) at rt for 30 min. However, no reaction occurred, and styrene was completely recovered. In addition, the reaction of 1a (1.0 mmol) with Sc(OTf)3 catalyst (0.050 mmol) in CH3NO2 (2.0 mL) in the absence of 2a at rt for 30 min gave a trace amount of di(1-phenylethan-1-yl)ether, and no styrene was formed. These results clearly indicate that no dehydration of the starting alcohols 1 to alkenes occurred under the present catalytic reaction conditions, and the present reaction does not involve an alkene intermediate. On the basis of all of the above results, the most plausible mechanism for the present Sc(OTf)3-catalyzed direct allylation of 1a with 2a is illustrated in Scheme 3. First, a highly oxophilic Sc(OTf)3 coordinates to an oxygen atom in 1a to promote the elimination of a hydroxyl group as −Sc(OTf)3(OH),29 which generates a carbocation. Immediate nucleophilic attack of 2a to the generated carbocation gives a β-silyl-substituted carbocation, which is stabilized by the β-effect of silicon30,31 because of a favorable interaction between the cation vacant p-orbital and the adjacent C−Si σ-bond. −Sc(OTf)3(OH) then returns to a catalytic cycle, and nucleophilic attack of Si by −Sc-

Scheme 3. Plausible Mechanism

(OTf)3(OH) occurs to give the desired 3a and Me3SiOH as a byproduct, with the regeneration of an active Sc(OTf)3 catalyst. A careful gas chromatography (GC)−mass spectrometry (MS) analysis revealed that the dehydrative dimerization of Me3SiOH occurred rapidly under the present reaction conditions to give 1,1,1,3,3,3-hexamethyldisiloxane ((Me3Si)2O), quantitatively.

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CONCLUSIONS In conclusion, we have developed homogeneous Sc(OTf)3catalyzed practical direct allylation reactions of general alcohols such as benzylic, allylic, and propargylic alcohols as well as several aliphatic alcohols under extremely mild and neutral reaction conditions, which proceed via a β-silyl groupstabilized carbocation as an intermediate to give the desired allylated products in high yield with high efficiency. Homogeneous Sc(OTf)3 catalyst dissolved completely in CH3NO2 and showed excellent and stable catalytic activity with high reproducibility in the present reaction. Consequently, this study resolves the argument about the uncertain catalytic activity of Sc(OTf)3. Further studies on the Sc(OTf)3catalyzed direct functionalization of alcohols with other silyl compounds bearing functional groups are in progress in our laboratory. 18889

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1-Methoxy-4-(pent-4-en-2-yl)benzene (3c). Colorless liquid, 95% yield. 1H NMR (400 MHz, CDCl3): δ 7.03 (d, J = 8.8 Hz, 2H), 6.76 (d, J = 8.8 Hz, 2H), 5.68−5.58 (m, 1H), 4.93−4.85 (m, 2H), 3.68 (s, 3H), 2.71−2.62 (m, 1H), 2.31− 2.14 (m, 2H), 1.15 (d, J = 6.8 Hz, 3H). 13C NMR (100 MHz, CDCl3): δ 157.75, 139.15, 137.27, 127.80, 115.75, 113.65, 55.19, 42.84, 38.90, 21.69. HRMS (APCI): calcd for C12H17O ([M + H]+), 177.1274; found, 177.1269. 1-Fluoro-4-(pent-4-en-2-yl)benzene (3d). Colorless liquid, 90% yield. 1H NMR (400 MHz, CDCl3): δ 7.07−7.02 (m, 2H), 6.91−6.85 (m, 2H), 5.65−5.55 (m, 1H), 4.92−4.86 (m, 2H), 2.74−2.65 (m, 1H), 2.29−2.14 (m, 2H), 1.14 (d, J = 6.8 Hz, 3H). 13C NMR (100 MHz, CDCl3): δ 161.21 (d, J = 242 Hz), 142.59, 142.56, 136.84, 128.27 (d, J = 8.2 Hz), 116.07, 114.97 (d, J = 20.6 Hz), 42.77, 39.08, 21.63. HRMS (EI): calcd for C11H13F ([M]+), 164.0996; found, 164.0997. 1-Chloro-4-(pent-4-en-2-yl)benzene (3e). Colorless liquid, 96% yield. 1H NMR (400 MHz, CDCl3): δ 7.24 (d, J = 8.3 Hz, 2H), 7.11 (d, J = 8.3 Hz, 2H), 5.74−5.62 (m, 1H), 5.00−4.93 (m, 2H), 2.81−2.74 (m, 1H), 2.36−2.23 (m, 2H), 1.23 (d, J = 6.8 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 145.41, 136.67, 131.51, 128.38, 128.35, 116.20, 42.52, 39.23, 21.45. HRMS (EI): calcd for C11H13Cl ([M]+), 180.0700; found, 180.0704. Hex-5-en-3-ylbenzene (3f). Colorless liquid, 85% yield. 1H NMR (400 MHz, CDCl3): δ 7.46−7.24 (m, 5H), 5.83−5.73 (m, 1H), 5.09−5.00 (m, 2H), 2.65−2.58 (m, 1H), 2.51−2.41 (m, 2H), 1.89−1.77 (m, 1H), 1.73−1.61 (m, 1H), 0.89 (t, J = 7.3 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 145.17, 137.23, 128.16, 127.75, 125.91, 115.65, 47.63, 40.90, 28.77, 11.99. HRMS (APCI): calcd for C12H17 ([M + H]+), 161.1325; found, 161.0806. 2-(Pent-4-en-2-yl)naphthalene (3g). Colorless liquid, >99% yield. 1H NMR (300 MHz, CDCl3): δ 7.70−7.65 (m, 3H), 7.51 (s, 1H), 7.36−7.23 (m, 3H), 5.70−5.57 (m, 1H), 4.95−4.83 (m, 2H), 2.91−2.79 (m, 1H), 2.43−2.33 (m, 1H), 2.31−2.21 (m, 1H), 1.23 (d, J = 6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 144.44, 137.06, 133.58, 132.18, 127.86, 127.56, 125.85, 125.80, 125.11, 125.06, 115.97, 42.52, 39.87, 21.48. HRMS (EI) [M]+: calcd for C15H16 ([M+]), 196.1247; found, 196.1245. But-3-ene-1,1-diyldibenzene (3h). Colorless liquid, >99% yield. 1H NMR (400 MHz, CDCl3): δ 7.29−7.14 (m, 10H), 5.77−5.67 (m, 1H), 5.05−4.93 (m, 2H), 4.00 (t, J = 7.8 Hz, 1H), 2.82 (dd, J = 7.8, 6.8 Hz, 2H). 13C NMR (75 MHz, CDCl3): δ 144.50, 136.83, 128.39, 127.94, 126.17, 116.25, 51.25, 39.94. HRMS (EI): calcd for C16H16 [M]+, 208.1247; found, 208.1251. 1-Chloro-4-(1-phenylbut-3-en-1-yl)benzene (3i). Colorless liquid, 78% yield. 1H NMR (300 MHz, CDCl3): δ 7.22−7.05 (m, 9H), 5.68−5.54 (m, 1H), 4.97−4.85 (m, 2H), 3.90 (t, J = 7.7 Hz, 1H), 2.73−2.67 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 143.97, 142.95, 136.37, 131.89, 129.30, 128.49, 127.80, 126.38, 116.60, 50.54, 39.80. HRMS (EI): calcd for C16H15Cl ([M]+), 242.0857; found, 242.0862. (2-Methylpent-4-en-2-yl)benzene (4a). Colorless liquid, 94% yield. 1H NMR (300 MHz, CDCl3): δ 7.33−7.12 (m, 5H), 5.59−5.45 (m, 1H), 4.95−4.89 (m, 2H), 2.33 (d, J = 7.3 Hz, 2H), 1.27 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 149.20, 135.56, 128.01, 125.81, 125.50, 116.88, 48.82, 37.57, 28.47. MS (EI): 160 [M]+, 91, 77. Anal. Calcd for C12H16: C, 89.94; H, 10.06. Found: C, 89.77; H, 10.02. But-3-ene-1,1,1-triyltribenzene (4b). White solid, 94% yield. 1H NMR (400 MHz, CDCl3): δ 7.19−7.09 (m, 15H),

EXPERIMENTAL SECTION General Information. Alcohols, allylsilanes, and nitromethane used in this study were dried and purified before use by standard procedures. 4-Methyl-1-phenylpent-2-yne-1,4diol32 and (1-chloroallyl)trimethylsilane 2b33 were prepared as described in the literature. Metal triflates including Sc(OTf)3 were purchased from commercial sources and used as received without further purification, unless otherwise noted. Dry CH2Cl2, toluene, and tetrahydrofuran (THF) were obtained by passing them through activated alumina columns of solvent-purification systems from Glass Contour Inc. under an argon atmosphere. NMR spectra were recorded on a JEOL EX-400 spectrometer (400 MHz for 1H and 100 MHz for 13C NMR) or JEOL AL-300 spectrometer (300 MHz for 1H and 75 MHz for 13C NMR). Samples were analyzed in CDCl3, and the chemical shift values were described relative to tetramethylsilane. GC analysis was carried out on a gas chromatograph equipped with a glass column (2.6 mm i.d. × 3.1 m) packed with SE-30 (5% on Uniport HP, 60−80 mesh), and GC yield was determined by using naphthalene or biphenyl as an internal standard. GC−MS analysis was performed using a Shimadzu Parvum2 mass spectrometer connected to a Shimadzu GC-2010 gas chromatograph [column: J&W Scientific fused silica capillary column DB-1 (column dimensions: 0.249 mm i.d. × 30 m, film thickness: 0.25 μm)]. High-resolution mass spectra (HRMS) were measured with a JEOL JMS-700 (EI) or Thermo Fischer Scientific Exactive spectrometer (APCI). Elemental analysis was carried out at the Center for Organic Elemental Microanalysis, Graduate School of Pharmaceutical Science, Kyoto University. Medium-pressure column chromatography was performed with a Shoko Scientific Purif-α2k equipped with a Moritex Purif-Pack (SI 60 μm and spherical) using hexane/ethyl acetate as an eluent. High-performance liquid chromatography (HPLC) analysis was performed using a Shimadzu Prominence equipped with a commercial chiral column at 25 °C with a UV detector at 254 nm. Hexane (HPLC grade) was used as an eluent. Representative Procedure. A mixture of Sc(OTf)3 (24.6 mg, 0.050 mmol, 5.0 mol %), alcohol (1.0 mmol), allyltrimethylsilane (342 mg, 3.0 mmol), and nitromethane (2.0−5.0 mL) was stirred under the reaction conditions noted in the text. After the reaction was complete, it was poured into dichloromethane or methanol (20 mL), and the samples were analyzed by GC and GC−MS. All products were purified by medium-pressure column chromatography and/or Kugelrohr distillation. Pent-4-en-2-ylbenzene (3a). Colorless liquid, 99% yield. 1H NMR (400 MHz, CDCl3): δ 7.37−7.16 (m, 5H), 5.77−5.66 (m, 1H), 5.02−4.94 (m, 2H), 2.83−2.74 (m, 1H), 2.43−2.24 (m, 2H), 1.25 (d, J = 6.8 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 147.05, 137.17, 128.28, 126.97, 125.92, 115.86, 42.65, 39.76, 21.47. HRMS (APCI): calcd for C11H15 ([M + H]+), 147.1168; found, 147.1166. 1-Methyl-4-(pent-4-en-2-yl)benzene (3b). Colorless liquid, 94% yield. 1H NMR (300 MHz, CDCl3): δ 7.10−7.04 (m, 4H), 5.76−5.62 (m, 1H), 5.01−4.91 (m, 2H), 2.77−2.68 (m, 1H), 2.40−2.19 (m, 2H), 2.30 (s, 3H), 1.21 (d, J = 6.9 Hz, 3H). 13C NMR (75 MHz, CDCl3): δ 144.04, 137.31, 135.33, 128.97, 126.83, 115.74, 42.70, 39.32, 21.60, 20.96. HRMS (EI): calcd for C12H16 ([M]+), 160.1247; found, 160.1251. 18890

DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894

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Hex-5-en-1-yne-1,3-diyldibenzene (6c). Colorless liquid, 86% yield. 1H NMR (400 MHz, CDCl3): δ 7.40−7.16 (m, 10H), 5.90−5.80 (m, 1H), 5.06−4.99 (m, 2H), 3.85 (t, J = 7.3 Hz, 1H), 2.54−2.51 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 141.36, 135.44, 131.65, 128.45, 128.17, 127.78, 127.56, 126.81, 123.66, 117.07, 90.91, 83.78, 42.77, 38.53. HRMS (EI): calcd for C18H16 ([M]+), 232.1247; found, 232.1242. Hex-5-en-1-yn-1-ylbenzene (6d). Colorless liquid, 40% yield. 1H NMR (400 MHz, CDCl3): δ 7.38−7.23 (m, 5H), 5.97−5.72 (m, 1H), 5.13−5.02 (m, 2H), 2.47 (t, J = 7.3 Hz, 2H), 2.36−2.31 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 136.94, 131.55, 128.16, 127.55, 123.89, 115.68, 89.49, 81.01, 32.96, 19.27. HRMS (EI): calcd for C12H12 ([M]+), 156.0934; found, 156.0936. (7,7-Dimethyldeca-1.9-dien-5-yn-4-yl)benzene (6e). Colorless liquid, 78% yield. 1H NMR (300 MHz, CDCl3): δ 7.31− 7.10 (m, 5H), 5.98−5.71 (m, 2H), 5.03−4.94 (m, 4H), 3.61 (dd, J = 8.0, 6.2 Hz, 1H), 2.40−2.34 (m, 2H), 2.12 (d, J = 7.3 Hz, 2H), 1.14 (s, 6H). 13C NMR (75 MHz, CDCl3): δ 142.18, 135.78, 135.62, 128.24, 127.50, 126.50, 117.05, 116.62, 90.94, 81.04, 47.91, 43.41, 37.88, 30.99, 29.20. HRMS (APCI): calcd for C18H23 ([M + H]+), 239.1794; found, 239.1788. 3-Allylcyclohex-1-ene (7a). Colorless liquid, 65% yield. 1H NMR (400 MHz, CDCl3): δ 5.86−5.75 (m, 1H), 5.70−5.66 (m, 1H), 5.59−5.56 (m, 1H), 5.05−4.98 (m, 2H), 2.19−2.11 (m, 1H), 2.07−2.03 (m, 2H), 1.99−1.94 (m, 2H), 1.79−1.67 (m, 2H), 1.58−1.46 (m, 1H), 1.28−1.19 (m, 1H). 13C NMR (100 MHz, CDCl3): δ 137.26, 131.39, 127.20, 115.70, 40.64, 35.03, 28.81, 25.28, 21.42. HRMS (EI): calcd for C9H14 ([M]+), 122.1090; found, 122.1091. (E)-Hexa-1,5-diene-1,3-diyldibenzene (7b). Pale yellow liquid, 83% yield. 1H NMR (300 MHz, CDCl3): δ 7.26− 7.06 (m, 10H), 6.34−6.22 (m, 2H), 5.74−5.60 (m, 1H), 4.99−4.88 (m, 2H), 3.43 (dt, J = 13.2, 7.3 Hz, 1H), 2.56−2.42 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 143.79, 137.42, 136.48, 133.44, 129.74, 128.47, 128.44, 127.71, 127.08, 126.32, 126.15, 116.30, 48.89, 40.16. HRMS (APCI): calcd for C18H19 ([M + H]+), 235.1481; found, 235.1477. 1-Allyladamantane (8a). Colorless liquid, 81% yield. 1H NMR (400 MHz, CDCl3): δ 5.81−5.70 (m, 1H), 4.95−4.86 (m, 2H), 1.87 (s, 3H), 1.75 (d, J = 7.3 Hz, 2H), 1.64−1.53 (m, 6H), 1.40 (d, J = 2.4 Hz, 6H). 13C NMR (100 MHz, CDCl3): δ 134.93, 116.45, 49.05, 42.51, 36.98, 32.67, 28.58. HRMS (EI): calcd for C13H20 ([M]+), 176.1560; found, 176.1560. Allylcyclohexane (8b). Colorless liquid, 44% yield. 1H NMR (400 MHz, CDCl3): δ 5.77−5.67 (m, 1H), 4.93−4.87 (m, 2H), 1.87 (t, J = 6.8 Hz, 2H), 1.65−1.54 (m, 5H), 1.28− 1.01 (m, 4H), 0.87−0.77 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 137.76, 115.11, 41.96, 37.67, 33.08, 26.58, 26.34. MS (EI): 124 ([M]+), 96, 83, 55. Anal. Calcd for C9H16: C, 87.02; H, 12.98. Found: C, 84.94; H, 12.37. Allylcyclopentane (8c). Colorless liquid, 38% yield. 1H NMR (300 MHz, CDCl3): δ 5.87−5.74 (m, 1H), 5.02−4.90 (m, 2H), 2.05 (t, J = 6.9 Hz, 2H), 1.93−1.44 (m, 7H), 1.19− 1.07 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 138.57, 114.59, 40.31, 39.59, 32.24, 25.14. HRMS (EI): calcd for C8H13 ([M − H]+), 109.1011; found, 109.1016. Pent-4-en-1-ylbenzene (8d). Colorless liquid, 84% yield. 1H NMR (400 MHz, CDCl3): δ 7.31−7.17 (m, 5H), 5.90−5.80 (m, 1H), 5.07−4.98 (m, 2H), 2.64 (t, J = 7.8 Hz, 2H), 2.14− 2.09 (m, 2H), 1.78−1.70 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 142.44, 138.59, 128.44, 128.25, 125.66, 114.68,

5.62−5.52 (m, 1H), 4.96−4.84 (m, 2H), 3.36 (d, J = 6.3 Hz, 2H). 13C NMR (100 MHz, CDCl3): δ 147.27, 135.96, 129.39, 127.72, 125.94, 117.21, 56.28, 45.53. HRMS (APCI): calcd for C22H21 ([M + H]+), 285.1638; found, 285.1629. But-3-en-1-ylbenzene (5a). Colorless liquid, 68% yield. 1H NMR (400 MHz, CDCl3): δ 7.43−7.22 (m, 5H), 5.95−5.81 (m, 1H), 5.11−5.01 (m, 2H), 2.75 (t, J = 7.3 Hz, 2H), 2.45− 2.39 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 141.85, 138.07, 128.41, 128.27, 125.79, 114.89, 35.50, 35.37. HRMS (EI): calcd for C10H12 ([M]+), 132.0934; found, 132.0938. 1-(But-3-en-1-yl)-4-methoxybenzene (5b). Colorless liquid, 78% yield. 1H NMR (300 MHz, CDCl3): δ 7.10 (d, J = 8.8 Hz, 2H), 6.82 (d, J = 8.8 Hz, 2H), 5.91−5.78 (m, 1H), 5.07−4.94 (m, 2H), 3.78 (s, 3H), 2.65 (t, J = 7.3 Hz, 2H), 2.37−2.30 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 157.74, 138.19, 133.94, 129.28, 114.77, 113.68, 55.16, 35.75, 34.45. HRMS (APCI): calcd for C11H15O ([M + H]+), 163.1117; found, 163.1113. 1-(But-3-en-1-yl)-4-methylbenzene (5c). Colorless liquid, 78% yield. 1H NMR (400 MHz, CDCl3): δ 7.00−6.97 (m, 4H), 5.81−5.71 (m, 1H), 4.97−4.86 (m, 2H), 2.57 (t, J = 7.8 Hz, 2H), 2.28−2.23 (m, 2H), 2.22 (s, 3H). 13C NMR (100 MHz, CDCl3): δ 138.77, 138.19, 135.18, 128.96, 128.27, 114.78, 35.62, 34.94, 20.98. HRMS (EI): calcd for C11H14 ([M]+), 146.1090; found, 146.1090. 1-(But-3-en-1-yl)-4-fluorobenzene (5d). Colorless liquid, 44% yield. 1H NMR (400 MHz, CDCl3): δ 7.08−7.04 (m, 2H), 6.91−6.86 (m, 2H), 5.81−5.71 (m, 1H), 4.97−4.89 (m, 2H), 2.61 (t, J = 7.3 Hz, 2H), 2.31−2.25 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 162.25 (d, J = 242 Hz), 137.76, 137.40 (d, J = 3.3 Hz), 129.72 (d, J = 7.4 Hz), 115.10 (d, J = 4.9 Hz), 114.87, 35.57, 34.52. HRMS (EI): calcd for C10H11F ([M]+), 150.0839; found, 150.0842. 1-(But-3-en-1-yl)-4-chlorobenzene (5e). Colorless liquid, 54% yield. 1H NMR (400 MHz, CDCl3): δ 7.23 (d, J = 8.3 Hz, 2H), 7.09 (d, J = 8.3 Hz, 2H), 5.86−5.76 (m, 1H), 5.04−4.96 (m, 2H), 2.66 (t, J = 7.8 Hz, 2H), 2.36−2.30 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 140.20, 137.58, 131.50, 129.66, 128.43, 115.23, 35.31, 34.67. HRMS (EI): calcd for C10H11Cl ([M]+), 166.0544; found, 166.0545. 2-(But-3-en-1-yl)thiophene (5f). Colorless liquid, 63% yield. 1H NMR (400 MHz, CDCl3): δ 7.02−6.70 (m, 3H), 5.82−5.72 (m, 1H), 5.01−4.90 (m, 2H), 2.83 (t, J = 7.3 Hz, 2H), 2.37−2.31 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 144.64, 137.40, 126.64, 124.17, 122.96, 115.43, 35.70, 29.42. HRMS (APCI): calcd for C8H11S ([M + H]+), 139.0576; found, 139.0574. (3,3-Dimethylhex-5-en-1-yn-1-yl)benzene (6a). Colorless liquid, 93% yield. 1H NMR (400 MHz, CDCl3): δ 7.31−7.14 (m, 5H), 5.98−5.87 (m, 1H), 5.04−4.99 (m, 2H), 2.17 (d, J = 7.3 Hz, 2H), 1.19 (s, 6H). 13C NMR (100 MHz, CDCl3): δ 135.25, 131.55, 128.09, 127.43, 123.98, 117.35, 96.87, 80.66, 47.69, 31.45, 28.86. HRMS (EI): calcd for C14H16 ([M]+), 184.1247; found, 184.1247. (3-Methylhex-5-en-1-yn-1-yl)benzene (6b). Colorless liquid, 61% yield. 1H NMR (400 MHz, CDCl3): δ 7.32− 7.15 (m, 5H), 5.91−5.80 (m, 1H), 5.07−4.99 (m, 2H), 2.69− 2.60 (m, 1H), 2.28−2.15 (m, 2H), 1.18 (d, J = 7.3 Hz, 3H). 13 C NMR (100 MHz, CDCl3): δ 135.99, 131.55, 128.12, 127.49, 123.92, 116.64, 94.00, 81.07, 41.11, 26.44, 20.48. HRMS (EI): calcd for C13H14 ([M]+), 170.1090; found, 170.1095. 18891

DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894

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Article

35.31, 33.28, 30.61. HRMS (EI): calcd for C11H14 ([M]+), 146.1090; found, 146.1087. 1-Methoxy-4-(pent-4-en-1-yl)benzene (8e). Colorless liquid, >99% yield. 1H NMR (300 MHz, CDCl3): δ 7.10 (d, J = 8.8 Hz, 2H), 6.83 (d, J = 8.8 Hz, 2H), 5.90−5.77 (m, 1H), 5.07−4.95 (m, 2H), 3.79 (s, 3H), 2.57 (t, J = 7.3 Hz, 2H), 2.13−2.05 (m, 2H), 1.75−1.64 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 158.28, 139.25, 135.10, 129.88, 115.20, 114.28, 55.79, 34.96, 33.81, 31.43. HRMS (APCI): calcd for C12H17O ([M + H]+), 177.1274; found, 177.1271. 1-Methyl-4-(pent-4-en-1-yl)benzene (8f). Colorless liquid, 82% yield. 1H NMR (300 MHz, CDCl3): δ 7.12−7.06 (m, 4H), 5.91−5.78 (m, 1H), 5.07−4.96 (m, 2H), 2.60 (t, J = 7.3 Hz, 2H), 2.32 (s, 3H), 2.14−2.07 (m, 2H), 1.76−1.66 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 139.96, 139.27, 135.67, 129.53, 128.91, 115.20, 35.45, 33.88, 31.32, 21.57. HRMS (EI): calcd for C12H16 ([M]+), 160.1247; found, 160.1229. 1-Chloro-4-(pent-4-en-1-yl)benzene (8g). Colorless liquid, 75% yield. 1H NMR (300 MHz, CDCl3): δ 7.25 (d, J = 8.4 Hz, 2H), 7.11 (d, J = 8.4 Hz, 2H), 5.90−5.76 (m, 1H), 5.07−4.97 (m, 2H), 2.60 (t, J = 7.7 Hz, 2H), 2.13−2.05 (m, 2H), 1.76− 1.65 (m, 2H). 13C NMR (75 MHz, CDCl3): δ 140.82, 138.32, 131.36, 129.76, 128.34, 114.88, 34.57, 33.10, 30.45. HRMS (EI): calcd for C11H13Cl ([M]+), 180.0700; found, 180.0693. (2-Methylpent-4-en-1-yl)benzene (9a) and Hex-5-en-3ylbenzene (3f). Colorless liquid, 9a/3f = 55/45, 47% total yield. 1H NMR (400 MHz, CDCl3): δ 7.22−7.05 (m), 5.78− 5.68 (m), 5.64−5.54 (m), 4.97−4.90 (m), 4.87−4.82 (m), 2.58 (dd, J = 13.6, 6.3 Hz), 2.47−2.39 (m), 2.33−2.26 (m), 2.07−2.01 (m), 1.88−1.42 (m), 0.79 (d, J = 6.8 Hz), 0.70 (t, J = 7.8 Hz). 13C NMR (75 MHz, CDCl3): δ 145.17, 141.30, 137.32, 137.22, 129.18, 128.17, 128.11, 127.75, 125.92, 125.67, 115.93, 115.65, 47.64, 43.08, 40.96, 40.91, 34.94, 28.78, 19.18, 12.01. (E)- and (Z)-(5-Chloropent-4-en-2-yl)benzene (10). Colorless liquid, E/Z = 69/31, 66% total yield. 1H NMR (400 MHz, CDCl3): δ 7.25−7.09 (m), 5.95−5.92 (m), 5.83 (d, J = 13.7 Hz), 5.76−5.69 (m), 5.58 (dd, J = 14.1, 7.3 Hz), 2.83−2.67 (m), 2.51−2.38 (m), 2.32−2.17 (m), 1.22 (d, J = 6.8 Hz), 1.18 (d, J = 6.8 Hz). 13C NMR (100 MHz, CDCl3): δ 146.35, 132.08, 130.04, 128.43, 128.38, 127.18, 126.91, 126.87, 126.22, 126.17, 118.82, 117.91, 39.64, 39.52, 39.16, 35.39, 21.70, 21.27. HRMS (EI): calcd for C11H13Cl ([M]+), 180.0700; found, 180.0703.

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Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We are grateful to Nissan Chemical Corporation for the financial support of this work. This research was conducted in part at the Katsura−Int’tech Center, Graduate School of Engineering, Kyoto University.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01627. Experimental details; chiral HPLC analysis of 3g; and H NMR and 13C NMR spectra for all products (PDF)

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REFERENCES

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*E-mail: [email protected]. Phone: +81-75-383-7055. Fax: +81-75-383-2504 (T.K.). ORCID

Yu Kimura: 0000-0001-5318-9255 Teruyuki Kondo: 0000-0003-1213-2337 18892

DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894

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DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894

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DOI: 10.1021/acsomega.8b01627 ACS Omega 2018, 3, 18885−18894