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Article Cite This: ACS Omega 2018, 3, 8865−8873
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In Situ-Generated Niobium-Catalyzed Synthesis of 3‑Pyrroline Derivatives via Ring-Closing Metathesis Reactions Maito Fuji, Jintaro Chiwata, Makoto Ozaki, Shunsuke Aratani, and Yasushi Obora* Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials, and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
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S Supporting Information *
ABSTRACT: An active in situ-generated Nb complex was used as a catalyst in the ring-closing metathesis reaction of N,N-diallyl-p-toluenesulfonamide to afford the corresponding 3-pyrroline derivative. The Nb complex was formed from NbCl 5 , trimethylsilyl chloride, Zn, and PhCHCl 2 in tetrahydrofuran. The Nb complex displayed high catalytic activity toward ring-closing metathesis reactions.
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INTRODUCTION Olefin metathesis reactions are useful in organic syntheses. Ring-closing metathesis (RCM), in particular, is a powerful tool for the synthesis of numerous ring systems, including heterocyclic, polycyclic, medium-membered ring, and macrocyclic compounds from diolefins.1 RCM has, therefore, been used in the synthesis of a wide-range of materials, such as drugs, functional materials, and natural products.2 Generally, metathesis reactions are catalyzed by carbene complexes, such as the Schrock Mo-carbene complex (a)3a and the Grubbs Rucarbene complexes (b and c)3 (Scheme 1). Research efforts with the aim of generating new and improved metathesis catalysts remain a significant interest. Likewise, studies of metathesis reactions catalyzed by early transition metals have been reported.4a Schrock reported a high oxidation state Ta and Nb-alkylidene complex (d) in the 1970s.4
The Mashima group reported the development of metathesis catalysts based on Ta and Nb. The precatalysts e and f have been reported to show catalytic activity toward ring-opening metathesis polymerization (ROMP) of norbornene.5a−e Nakayama et al. reported a system, in which an (aryloxy)tantalum or (aryloxy)niobium complex, in the presence of a trialkylaluminum co-catalyst, demonstrated catalytic activity in ROMP.5 Galletti reported the ROMP reaction of norbornene catalyzed by niobium(V) N,N-dialkylcarbamates in the presence of methylaluminoxane.5h Recently, Veige et al. and Nomura et al. reported ROMP reactions catalyzed by a Nbdineophyl complex with a [CF3-ONO]3 trianionic pincer-type ligand5i and the (imido)niobium-alkylidene complex Nb(CHSiMe3)(2,6-Me2C6H3N)[OC(CF3)3](PMe3)2,5j respectively. Bruno et al. used a niobium-imido complex as a catalyst for imine metathesis.5k However, synthesis of these catalysts requires multiple steps, including a thermally unstable step. Niobium-catalyzed RCM reactions have been less studied, and no examples have been reported. RCM reactions catalyzed by the Tebbe reagent or Petasis reagent, which are titanium-based methylenation reagents, have been reported.6a,b Takai reported the olefination of a carbonyl group using a titanium−zinc system, i.e., the Takai− Lombardo reaction (Scheme 2).6 This complex has also been employed as a precatalyst in RCM.6g However, elucidation of the structure of the active species is required. Niobium has multiple oxidation states, and numerous niobium complexes have been reported. Niobium catalysts have therefore received increasing attention in organic syntheses.7 Our recent studies have demonstrated that niobium displays a high affinity for unsaturated bonds, such as olefin and alkyne bonds. In particular, low-valent niobium
Scheme 1. Various Carbene Complexes and Carbene Precursors
Received: July 13, 2018 Accepted: July 30, 2018 Published: August 9, 2018 © 2018 American Chemical Society
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Table 1. Optimization of Reaction Conditionsa
Scheme 2. Olefination of Carbonyl Groups Using a Titanium-Based Complex
exhibits high catalytic activity toward cycloaddition reactions of alkynes with alkenes or nitriles.7d−i High-valent niobium possesses strong Lewis acidity.7j−l In this study, Nb-based active species were generated in situ from niobium pentachloride. These materials catalyzed the RCM reactions of diallylic compounds quantitatively to yield various ring products. Additionally, the reactions proceeded via a one-step process.
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RESULTS AND DISCUSSION The RCM of N,N-diallyl-p-toluenesulfonamide was initially investigated as a model substrate to optimize the reaction conditions (Table 1). When a mixture of niobium pentachloride, 8 trimethylsilyl chloride (TMSCl), Zn, benzyl dichloride, and N,N-diallyl-p-toluenesulfonamide in tetrahydrofuran (THF) was heated at 60 °C for 2 h, the desired RCM product 1-(p-toluenesulfonyl)-3-pyrroline was isolated in 94% yield (Table 1, entry 1). The metathesis reaction also proceeded efficiently in the presence of NbCl4(THF)2 or NbCl3(DME) catalyst precursor (Table 1, entries 3 and 4). It was possible to reduce the amount of Zn when NbCl3(DME) was used (Table 1, entry 5). When substituting NbCl5 for Nb(OEt)5 catalyst, the RCM product yield was slightly lower, i.e., 91% (Table 1, entry 6). However, in the case of NbF5, the RCM product yield decreased significantly (Table 1, entry 7). Alternative metal chlorides, including TaCl5, TiCl4, and FeCl3, were also investigated; however, the desired RCM products were not obtained (Table 1, entries 8−10). The reaction did not proceed in the absence of a catalyst precursor (Table 1, entry 11). These results demonstrate that this catalytic transformation is specific for niobium-based catalysts. The reaction in the absence of TMSCl failed (Table 1, entry 12). In situ activation of zinc dust using TMSCl in THF has reported only a limited number of reactions,9 such as the Reformatsky reaction.9g Herein, the influence of solvents is also presented. When substituting THF for MeTHF, the desired RCM product was obtained, but in a lower yield, i.e., 60% (Table 1, entry 13). However, the use of dioxane afforded only trace quantities of the desired product (Table 1, entry 14). Tetrahydropyran (THP), toluene, and 1,2-dichloroethane (DCE) are not suitable solvents, even in the presence of NbCl4(THF)2 (Table 1, entries 15−18). Notably, the replacement of Zn with Mn or Mg led to considerably decreased yields, which is attributed to a failure to form the organometallic compound and reduction of NbCl5 (Table 1, entries 19 and 20). The investigations herein also examined the effects of reaction temperature. The reaction proceeded quantitatively at 40 °C and at room temperature (Table 1, entries 21 and 22). Furthermore, the reaction progress was examined at 60 °C to determine reproducibility.
entry
catalyst precursor
additive
conv. (%)b
yield (%)b
1 2c 3 4 5d 6 7 8 9 10 11 12e 13f 14g 15h 16i 17j 18j 19k 20l 21m 22n 23 24
NbCl5 NbCl5 NbCl4(THF)2 NbCl3(DME) NbCl3(DME) Nb(OEt)5 NbF5 TaCl5 TiCl4 FeCl3 none NbCl5 NbCl5 NbCl5 NbCl5 NbCl5 NbCl5 NbCl4(THF)2 NbCl5 NbCl5 NbCl5 NbCl5 NbCl5 NbCl5
PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCHCl2 PhCH2Cl PhCCl3
>99 >99 >99 >99 >99 91 14 9 nr nr nr nr 75 1 nr nr nr nr 53 56 >99 >99 nr nr
>99 (94) >99 >99 >99 >99 91 5 nd nd nd nd nd 60 trace nd nd nd nd 50 4 >99 >99 nd nd
a
Reaction conditions: 1a (1 mmol), catalyst (0.1 mmol), trimethylsilyl chloride (TMSCl, 0.5 mmol), Zn (1.5 mmol), additive (0.5 mmol), and THF (3 mL) at 60 °C for 2 h. bConversions and yields were determined by gas chromatography (GC); the number in parentheses shows the isolated yield. cNbCl5 (5 mol %) was used. dZn (1.0 mmol) was used. eIn the absence of TMSCl. fSubstituting 2MeTHF for THF. gSubstituting dioxane for THF. hSubstituting tetrahydropyran (THP) for THF. iSubstituting toulene for THF. j Substituting 1,2-dichloroethane (DCE) for THF. kSubstituting Mn for Zn. lSubstituting Mg for Zn. mReaction temperature 40 °C. nAt room temperature (ca. 22 °C).
When employing PhCH2Cl as a carbene precursor as a substitute to PhCHCl2, the reaction afforded 1,2-diphenylethane as a byproduct, with the desired RCM product not observed (Table 1, entry 23). Additionally, the use of PhCCl3 led to the formation of α,α′-dichlorostilbene and not the desired RCM product (Table 1, entry 24). When subjected to the model reaction conditions, stilbene formed as a dimer because of organozinc compound or a possible carbene complex formation during the reaction (vide infra, Scheme 6). When TMSCl, Zn, THF, and PhCHCl2 were reacted at 60 °C for 2 h, stilbene was obtained in 66% yield (Scheme 3), demonstrating that the organozinc compound dimerized yielding stilbene.9c Substrate effect and limitations were examined using a variety of dienes under optimized conditions (Table 2). First, the steric effects were investigated using N-allyl-N-(2methylallyl)-p-toluenesulfonamide (1b), N,N-di(2-methylallyl)-p-toluenesulfonamide (1c), and N-allyl-N-(3-methyl-28866
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not react (Table 2, entries 2−4). Additionally, 1e and 1f, differing in their carbon chain length, led to the corresponding six- or seven-membered ring, respectively, in moderate yields (Table 2, entries 5 and 6). Aniline derivatives were also examined. N,N-Diallylaniline (1g) reacted efficiently to give 2g in excellent yield. A small amount of the aromatized product, pyrrole 2g′, was also obtained. The reactions of the electron-rich anilines, N,Ndiallyl-4-methylaniline (1h) and N,N-diallyl-4-methoxyaniline (1i), gave the corresponding products in high yields. Conversely, N,N-diallyl-4-trifluoroaniline (1j) was suitable, forming the corresponding product in excellent yield with high selectivity (Table 2, entries 7−10). Benzyloxycarbonyl-protected diallylamine 1k was not suitable for this system. It is considered that the oxygen site inhibited the reaction (Table 2, entry 11). Furthermore, the malonate-based substrate 1l afforded a moderate amount of 2l (Table 2, entry 12). The catalytic system in the cross-metathesis reaction having two different terminal olefins was also examined (Scheme 4). 1-Dodecene (3a) (1 mmol) was reacted with vinylcyclohexane (3b) (10 mmol) to yield (22%) 1-cyclohexyl-1-dodecene (5ab) along with trace amounts of 11-docosene and dicyclohexylethene. The olefination reaction of ketone 4 was also examined (Scheme 5). As a result, (cyclohexylidenemethyl)benzene (5c) was obtained in 20% yield. However, the product (5c) was not obtained in the absence of NbCl5, suggesting the formation of Nb-benzylidene species during the catalytic cycle. Although it is not possible to elucidate the detailed reaction mechanism, a possible reaction path for this transformation is shown in Scheme 6. First, a low-valent niobium species is generated by reduction of niobium chloride with Zn. The formation of an organozinc compound results from the reaction of PhCH2Cl2 with Zn and is activated by TMSCl. The low-valent Nb reacts with the organozinc compound to yield the Nb-based active species, and stilbene forms via dimerization of the organozinc compound. The formation of Ru-carbene complexes by using PhCHCl2 was reported,10 which suggests the formation of Nb-alkylidene analogues in our catalytic system. However, all of the attempts to isolate and characterize the Nb-alkylidene species were unsuccessful. The subsequent carbene RCM reaction proceeds according to the general metathesis mechanism (Scheme 7).1j The Nbbased active species A reacts with an olefin via B to give C, which reacts with another olefin via niobacycle D to yield the product, with regeneration of the active catalytic species A.
Scheme 3. Generation of Stilbene in the Absence of NbCl5 and Trimethylsilyl Chloride
Table 2. Substrate Effect on Ring-Closing Metathesis (RCM) Reactionsa
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CONCLUSIONS In summary, we have developed an in situ-generated Nb complex catalyst for the quantitative preparation of 3-pyrroline derivatives via the RCM reaction of N,N-diallyl-p-toluenesulfonamides. A series of RCM reactions with Nb as the catalyst was studied, and the desired products were obtained quantitatively. This study is one of only a few studies in this area, and the results will provide a platform for the development of other Nb-catalyzed metathesis reactions.
a Reaction conditions: diene (1 mmol), NbCl5 (0.1 mmol), TMSCl (0.5 mmol), Zn (1.5 mmol), PhCHCl2 (0.5 mmol), and THF (3 mL) at 60 °C for 2 h. Isolated yields. bNo reaction. c40 °C for 6 h. d Selectivity determined by 1H NMR or 19F NMR.
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butenyl)-p-toluenesulfonamide (1d). When one side of the diene possessed bulky constituents, i.e., 1b and 1d, the corresponding pyrroline derivatives were obtained quantitatively. However, diene 1c, in which both sides are bulky, did
EXPERIMENTAL SECTION General. GC analysis was performed with a flame ionization detector using a 0.22 mm × 25 m capillary column
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Scheme 4. Cross-Metathesis Study
Scheme 5. Olefination of Cyclohexanone Using the Present System
Scheme 7. Plausible Mechanism for the RCM Reaction
(BP-5). 1H and 13C NMR were measured at 400 and 100 MHz, respectively, in CDCl3 with Me4Si as the internal standard. Compounds 1a,11 1b,11 1c,12 1d,13 1e,11 1f,12 1g,14 1h,14 1i,14 1j,16 1k,12 2a,11 2b,11 2e,11 2f,12 2g,15 2g′,14 2h,18 2h′,14 2i,19 2i′,14 2j,20 2j′,17 and 2l12 are known compounds, which have previously been reported. Other compounds, including 1l, 3a, 3b, and NbCl5 (Wako, 95% purity), were purchased and used without purification. Purification of Zinc (Wako, Powder, 75−150 μm). Zn (5 g) was added to 10% HCl aq (20 mL) and stirred for 5 min. Thereafter, the mixture was filtered and washed with H2O (10 mL) and acetone (10 mL). The solid was dried under vacuum for 1 day.
Procedure for the Preparation of 2a (Entry 1, Table 1). A mixture comprising THF (1.5 mL), Zn (98 mg, 1.5 mmol), and TMSCl (54 mg, 0.5 mmol) was stirred for 10 min at room temperature under an Ar atmosphere. Thereafter,
Scheme 6. Plausible Mechanism for the Formation of Nb-Based Active Species
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MHz; CDCl3) δ: 19.9 (CH3), 21.4 (CH3), 53.0 (CH2), 114.4 (CH2), 127.1 (CH), 129.4 (CH), 137.3 (C), 140.0 (C), 143.0 (C); GC-MS (EI) m/z (relative intensity) 279 (10) [M+], 155 (72), 124 (33), 108 (21), 91 (100). 1d:13 The procedure followed that of 1b except that 1bromo-3-methyl-2-butene was used instead of 1-bromo-2propene to afford 1d (2.9 mmol, 98%) as a yellow oil; 1H NMR (400 MHz; CDCl3) δ: 1.58 (s, 3H), 1.65 (d, J = 0.9 Hz, 3H), 2.42 (s, 3H), 3.78 (t, J = 5.8 Hz, 4H), 4.96−5.00 (m, 1H), 5.11 (t, J = 1.4 Hz, 1H), 5.14 (ddd, J = 7.9, 1.4, 0.7 Hz, 1H), 5.60−5.70 (m, 1H), 7.28 (d, J = 7.9 Hz, 2H), 7.69 (d, J = 8.4 Hz, 2H); 13C NMR (400 MHz; CDCl3) δ: 17.8 (CH3), 21.5 (CH3), 25.7 (CH3), 44.5 (CH2), 49.3 (CH2), 118.3 (CH2), 118.9 (CH), 127.2 (CH), 129.6 (CH), 133.3 (CH), 136.8 (C), 137.7 (C), 143.0 (C); GC-MS (EI) m/z (relative intensity) 279 (1) [M+], 155 (42), 124 (95), 68 (69), 41 (100). 1e:11 The procedure was the same as for the preparation of 1b except that 1-bromo-3-butene substituted 1-bromo-2propene to afford 1e (2.8 mmol, 93%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 2.27 (q, J = 7.3 Hz, 2H), 2.42 (s, 3H), 3.18 (t, J = 7.8 Hz, 2H), 3.81 (d, J = 6.4 Hz, 2H), 5.00− 5.20 (m, 4H), 5.59−5.75 (m, 2H), 7.30 (d, J = 8.2 Hz, 2H), 7.70 (d, J = 8.2 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 21.5 (CH3), 32.9 (CH2), 46.7 (CH2), 50.7 (CH2), 117.0 (CH2), 118.8 (CH2), 127.1 (CH), 129.7 (CH), 133.2 (CH), 134.7 (CH), 137.1 (C), 143.2 (C); GC-MS (EI) m/z (relative intensity) 265 (1) [M+], 224 (92), 155 (78), 91 (100), 68 (33). 1f:12 The procedure was the same as for the preparation of 1c except that 1-bromo-3-butene was used instead of 1-bromo2-methyl-2-propene to afford 1f (2.7 mmol, 90%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 2.30 (q, J = 7.4 Hz, 4H), 2.42 (s, 3H), 3.19 (t, J = 7.7 Hz, 4H), 5.02−5.08 (m, 4H), 5.67−5.77 (m, 2H), 7.30 (d, J = 8.2 Hz, 2H), 7.70 (d, J = 8.2 Hz, 2H); 13C NMR (400 MHz; CDCl3) δ: 21.5 (CH3), 33.2 (CH2), 47.7 (CH2), 117.1 (CH2), 127.1 (CH), 129.6 (CH), 134.6 (CH), 136.9 (C), 143.1 (C); GC-MS (EI) m/z (relative intensity) 279 (1) [M+], 238 (44), 184 (46), 155 (66), 91 (100). 1g:14 The product was prepared as follows: allylbromide (10 mmol) was added to a solution composed of aniline (3 mmol) and Cs2CO3 (3.5 mmol) in EtOH/H2O (12 mL, 4:1), and the mixture was stirred under reflux conditions (ca. 80 °C) for 2 days. After the reaction, diethyl ether (50 mL) was added to the mixture, and the organic layer was washed with brine and concentrated under reduced pressure. Purification by silica gel chromatography (n-hexane/EtOAc = 4:1) gave 1g (2.8 mmol, 93%) as a pale yellow oil; 1H NMR (400 MHz; CDCl3) δ: 3.82 (d, J = 4.9 Hz, 4H), 5.09−5.12 (m, 4H), 5.75−5.81 (m, 2H), 6.63 (t, J = 7.9 Hz, 3H), 7.14 (t, J = 7.9 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 52.6 (CH2), 112.3 (CH), 115.8 (CH2), 116.3 (CH), 129.0 (CH), 134.0 (CH), 148.6 (C); GC-MS (EI) m/z (relative intensity) 173 (79) [M+], 146 (100), 130 (56), 104 (76), 77 (80). 1h:14 The procedure followed that of 1g except that pmethylaniline was used instead of aniline to afford 1h (2.7 mmol, 90%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 2.23 (s, 3H), 3.88 (d, J = 5.0 Hz, 4H), 5.12−5.19 (m, 4H), 5.82−5.87 (m, 2H), 6.62 (d, J = 8.6 Hz, 2H), 7.01 (d, J = 8.2 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 20.2 (CH3), 52.9 (CH2), 112.6 (CH), 115.9 (CH2), 125.5 (C), 129.6 (CH),
PhCHCl2 (81 mg, 0.5 mmol) was added to the mixture and stirred for 10 min at 60 °C. At this time, a color change of the reaction mixture to grayish brown was observed. NbCl5 (27 mg, 0.1 mmol) in THF (1.5 mL) was added to the solution and stirred for 5 min, which resulted in the reaction mixture turning color from dark violet to dark brown. Finally, the substrate N,N-diallyl-p-toluenesulfonamide (1a, 251 mg, 1 mmol) was added to the solution and stirred for 2 h at 60 °C. The RCM product (2a) was isolated by column chromatography (silica gel (50 cc) neutralized by NEt3 (3 mL)/nhexane/EtOAc = 100:0−4:1) in 94% yield (211 mg) as a white solid (mp 124−125 °C). 1a:11 The product was prepared as follows: a mixture comprising N,N-diallylamine (27.5 mmol), TsCl (25 mmol), CH2Cl2 (100 mL), and triethylamine (40 mmol) was stirred for 16 h at room temperature. After the reaction, diethyl ether (100 mL) was added to the mixture, and the organic layer was washed with brine and concentrated under reduced pressure. Purification by silica gel chromatography (n-hexane/EtOAc = 8:1) gave 1a (22.9 mmol, 92%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ 2.43 (s, 3H), 3.80 (d, J = 6.4 Hz, 4H), 5.12−5.16 (m, 4H), 5.56−5.66 (m, 2H), 7.30 (d, J = 5.5 Hz, 2H), 7.71 (d, J = 5.3 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ 21.5 (CH3), 49.3 (CH2), 119.0 (CH2), 127.2 (CH), 129.7 (CH), 132.7 (CH), 137.4 (C), 143.2 (C); GC-MS (EI) m/z (relative intensity) 251 (7) [M+], 155 (49), 96 (58), 91 (100), 65 (27), 41 (51). 1b:11 The product was prepared as follows: TsCl (12 mmol) in CH2Cl2 (20 mL) was added to a solution of N-allylamine (12.5 mmol) and triethylamine (12.5 mmol) in CH2Cl2 (20 mL) at 0 °C. The mixture was stirred at room temperature for 16 h. After the reaction, diethyl ether (50 mL) was added to the mixture, and the organic layer was washed with brine and concentrated under reduced pressure to afford N-allyl-ptoluenesulfonamide (11 mmol, 91%) as a white solid. Thereafter, a mixture composed of N-allyl-p-toluenesulfonamide (3 mmol), 1-bromo-2-methyl-2-propene (5 mmol), and Cs2CO3 (9 mmol) in CH3CN (35 mL) was stirred at 80 °C for 16 h. Thereafter, diethyl ether (50 mL) was added to the reaction mixture, and the organic layer was washed with brine and concentrated under reduced pressure. Purification by silica gel chromatography (n-hexane/EtOAc = 8:1) yielded 1b (2.6 mmol, 87%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 1.69 (s, 3H), 2.42 (s, 3H), 3.70 (s, 2H), 3.77 (d, J = 6.7 Hz, 2H), 4.85 (brs, 1H), 4.91 (brs, 1H), 5.06−5.08 (m, 1H), 5.10−5.11 (m, 1H), 5.47−5.57 (m, 1H), 7.29 (d, J = 7.9 Hz, 2H), 7.71 (d, J = 8.3 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 19.8 (CH3), 21.5 (CH3), 49.4 (CH2), 52.8 (CH2), 114.5 (CH2), 119.2 (CH2), 127.2 (CH), 129.6 (CH), 132.3 (CH), 137.4 (C), 140.1 (C), 143.2 (C); GC-MS (EI) m/z (relative intensity) 265 (9) [M+], 155 (77), 110 (33), 91 (100), 68 (27). 1c:12 The product was prepared as follows: a mixture comprising p-toluenesulfonamide (3 mmol), 1-bromo-2methyl-2-propene (9 mmol), and Cs2CO3 (9 mmol) in dimethylformamide (10 mL) was stirred at 50 °C for 24 h. Thereafter, diethyl ether (50 mL) was added to the mixture, and the organic layer was washed with brine and concentrated under reduced pressure. Purification by silica gel chromatography (n-hexane/EtOAc = 8:1) yielded 1c (2.9 mmol, 96%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 1.61 (s, 6H), 2.41 (s, 3H), 3.70 (s, 4H), 4.78 (brs, 2H), 4.86 (brs, 2H), 7.28 (d, J = 7.9 Hz, 2H), 7.71 (d, J = 8.1 Hz, 2H); 13C NMR (100 8869
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3H), 3.27 (t, J = 5.2 Hz, 4H), 5.75 (brs, 2H), 7.30 (d, J = 8.2 Hz, 2H), 7.67 (d, J = 8.2 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 21.5 (CH3), 29.9 (CH2), 48.3 (CH2), 116.1 (CH), 127.1 (CH), 129.7 (CH), 130.3 (CH), 136.2 (C), 143.1 (C); GC-MS (EI) m/z (relative intensity) 251 (13) [M+], 155 (7), 96 (27), 91 (26), 77 (2), 41 (100). 2g,15 2g′:14 yield 96% (96:4) (139 mg), white solid (mp 90−91 °C) (lit. 2g:13 101−102 °C, 2g′:12 56−60 °C) 1 H NMR (400 MHz; CDCl3) δ: 4.08 (s, 4H), 5.93 (brs, 2H), 6.52 (d, J = 8.6 Hz, 2H), 6.68 (t, J = 7.3 Hz, 1H), 7.24 (t, J = 8.7 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 54.4 (CH2), 111.1 (CH), 115.5 (CH), 126.4 (CH), 129.3 (CH), 147.0 (C); GC-MS (EI) m/z (relative intensity) 145 (100) [M+], 127 (8), 104 (63), 91 (9), 77 (50). 1 H NMR (400 MHz; CDCl3) δ: 6.34 (t, J = 2.2 Hz, 2H), 7.07 (t, J = 2.2 Hz, 2H), 7.10 (s, 1H), 7.2−7.5 (m, 4H); 13C NMR (100 MHz; CDCl3) δ: 110.4 (CH), 119.3 (CH), 120.5 (CH), 125.6 (CH), 129.5 (CH), 137.3 (C); GC-MS (EI) m/z (relative intensity) 143 (100) [M+], 115 (57), 104 (4), 77 (14). 2h,18 2h′:14 yield 75% (84:16) (119 mg), white solid (mp 88−90 °C) (lit. 2h:18 92−93 °C, 2h′:14 82.5−83.3 °C) 1 H NMR (400 MHz; CDCl3) δ: 2.24 (s, 3H), 4.04 (s, 4H), 5.89 (s, 2H), 6.43 (d, J = 8.2 Hz, 2H), 7.04 (d, J = 8.3 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 20.2 (CH3), 54.5 (CH2), 111.1 (CH), 124.4 (C), 126.4 (CH), 129.7 (CH), 145.0 (C); GC-MS (EI) m/z (relative intensity) 159 (100) [M+], 143 (31), 118 (76), 91 (48), 77 (5). 1 H NMR (400 MHz; CDCl3) δ: 2.33 (s, 3H), 6.31 (s, 2H), 7.03 (s, 2H), 7.17 (d, J = 8.0 Hz, 2H), 7.24 (d, J = 8.1 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 20.8 (CH3), 110.0 (CH), 119.2 (CH), 120.4 (CH), 130.0 (CH), 135.2 (C), 138.4 (C); GC-MS (EI) m/z (relative intensity) 157 (100) [M+], 129 (26), 115 (21), 77 (5), 65 (10). 2i,19 2i′:14 yield 76% (82:18) (133 mg), white solid (mp 107−108 °C) (lit. 2i′:14 110−111 °C) 1 H NMR (400 MHz; CDCl3) δ: 3.74 (s, 3H), 4.05 (s, 4H), 5.91 (s, 2H), 6.47 (d, J = 8.7 Hz, 2H), 6.85 (d, J = 8.7 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 54.8 (CH3), 55.9 (CH2), 111.7 (CH), 115.1 (CH), 126.5 (CH), 142.1 (C), 150.7 (C); GC-MS (EI) m/z (relative intensity) 175 (100) [M+], 134 (62), 160 (35), 130 (17), 77 (18). 1 H NMR (400 MHz; CDCl3) δ: 3.80 (s, 3H), 6.31 (s, 2H), 6.92 (d, J = 8.6 Hz, 2H), 6.98 (s, 2H), 7.28 (d, J = 8.6 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 55.4 (CH3), 109.8 (CH), 114.5 (CH), 119.6 (CH), 122.0 (CH), 134.4 (C), 157.6 (C); GC-MS (EI) m/z (relative intensity) 173 (88) [M+], 158 (100), 130 (43), 103 (16), 77 (12). 2j,20 2j′:17 yield 90% (97:3) (192 mg), white solid (mp 114−115 °C) (lit. 2j′:17 112−114 °C) 1 H NMR (400 MHz; CDCl3) δ: 4.10 (s, 4H), 5.93 (t, J = 4.2 Hz, 2H), 6.49 (d, J = 8.6 Hz, 2H), 7.45 (d, J = 8.7 Hz, 2H); 13 C NMR (100 MHz; CDCl3) δ: 54.3 (CH2), 110.5 (CH), 117.0 (q, 2JC−F = 32.6 Hz, C), 125.3 (q, 1JC−F = 270 Hz, CF3), 126.1 (CH), 126.5 (q, 3JC−F = 3.8 Hz, CH), 148.9 (C); GCMS (EI) m/z (relative intensity) 213 (100) [M+], 194 (9), 172 (79), 145 (54), 115 (10). GC-MS (EI) m/z (relative intensity) 211 (100) [M+], 192 (6), 164 (7), 145 (13), 115 (59). 2l:12 yield 65% (138 mg), yellow oil; 1H NMR (400 MHz; CDCl3) δ: 1.25 (t, J = 7.1 Hz, 7H), 3.01 (s, 4H), 4.20 (dd, J = 7.1, 3.6 Hz, 4H), 5.58−5.63 (m, 2H); 13C NMR (100 MHz; CDCl3) δ: 14.0 (CH3), 40.8 (CH2), 58.8 (C), 61.5 (CH2),
134.2 (CH), 146.6 (C); GC-MS (EI) m/z (relative intensity) 187 (100) [M+], 160 (90), 144 (36), 118 (75), 91 (76). 1i:14 The procedure followed that of 1g except that pmethoxyaniline was used instead of aniline to afford 1i (2.7 mmol, 90%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 3.74 (s, 3H), 3.85 (d, J = 5.0 Hz, 4H), 5.12−5.20 (m, 4H), 5.80−5.89 (m, 2H), 6.68 (d, J = 9.1 Hz, 2H), 6.80 (d, J = 9.1 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 53.6 (CH2), 55.8 (CH3), 114.4 (CH), 114.6 (CH), 116.1 (CH2), 134.5 (CH), 143.5 (C), 151.5 (C); GC-MS (EI) m/z (relative intensity) 203 (100) [M+], 176 (41), 135 (55), 91 (9), 77 (16). 1j:16 The procedure followed the preparation of 1g except that p-trifluoromethylaniline substituted aniline to afford 1j (2.0 mmol, 67%) as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 3.94 (d, J = 4.7 Hz, 4H), 5.14−5.17 (m, 4H), 5.80− 5.83 (m, 2H), 6.67 (d, J = 8.9 Hz, 2H), 7.40 (d, J = 8.9 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 52.7 (CH2), 111.3 (CH), 116.3 (CH2), 117.7 (q, 2JC−F = 32.7 Hz, C), 125.2 (q, 1 JC−F = 269 Hz, CF3), 126.4 (q, 3JC−F = 4.0 Hz, CH) 132.9 (CH), 150.8 (C); GC-MS (EI) m/z (relative intensity) 241 (84) [M+], 214 (79), 172 (36), 145 (51), 41 (100). 1k:12 The product was prepared as follows: a solution of CbzCl (6.0 mmol) in DCE (10 mL) was added dropwise to a mixture comprising diallylamine (5.8 mmol) and triethylamine (6 mmol) in DCM (10 mL) and stirred for 20 min at room temperature. Thereafter, diethyl ether (50 mL) was added to the mixture, and the organic layer was washed with brine and concentrated under reduced pressure. Purification by silica gel chromatography (n-hexane/EtOAc = 3:1) yielded 1k (5.6 mmol, 97%) as a yellow oil; 1H NMR (400 MHz; CDCl3) δ: 3.88 (d, J = 12.6 Hz, 4H), 5.10−5.13 (m, 6H), 5.76 (brs, 2H), 7.34−7.35 (m, 5H); 13C NMR (100 MHz; CDCl3) δ: 48.8 (CH2), 49.1 (CH2), 67.1 (CH2), 116.9 (CH2), 117.1 (CH2), 127.7 (CH), 127.9 (CH), 128.4 (CH), 133.5 (C), 136.8 (CH), 155.9 (C); GC-MS (EI) m/z (relative intensity) 231(1) [M+], 140 (15), 114 (13), 91 (100), 65 (11). 2a:11 yield 94% (211 mg), white solid (mp 124−125 °C) (lit.11 123.2−126.5 °C); 1H NMR (400 MHz; CDCl3) δ 2.43 (s, 3H), 4.12 (s, 4H), 5.65 (s, 2H), 7.32 (d, J = 8 Hz, 2H), 7.72 (d, J = 8 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ 21.5 (CH3), 54.8 (CH2), 125.5 (CH), 127.4 (CH), 129.8 (CH), 134.3 (C), 143.4 (C); GC-MS (EI) m/z (relative intensity) 223 (20) [M+], 155 (30), 91 (87), 77 (2), 68 (100), 63 (5). 2b:11 yield 95% (225 mg), white solid (mp 98−99 °C) (lit.11 100.8−101.8 °C); 1H NMR (400 MHz; CDCl3) δ: 1.64 (s, 3H), 2.41 (s, 3H), 3.96 (s, 4H), 4.06 (s, 4H), 5.24−5.25 (m, 1H), 7.33 (d, J = 8.3 Hz, 2H), 7.72 (d, J = 8.3 Hz, 2H); 13 C NMR (100 MHz; CDCl3) δ: 14.0 (CH3), 21.5 (CH3), 55.1 (CH2), 57.7 (CH2), 119.1 (CH), 127.4 (CH), 129.8 (CH), 134.0 (C), 135.0 (C), 143.4 (C); GC-MS (EI) m/z (relative intensity) 237 (11) [M+], 222 (19), 91 (64), 82 (100), 65 (19). 2e:11 yield 40% (95 mg) white solid (mp 94−95 °C) (lit.11 99.7−102.2 °C); 1H NMR (400 MHz; CDCl3) δ: 2.21 (s, 2H), 2.43 (s, 3H), 3.17 (t, J = 5.6 Hz, 2H), 3.57 (s, 2H), 5.61 (d, J = 9.5 Hz, 2H), 5.75 (d, J = 9.6 Hz, 2H), 7.32 (d, J = 7.7 Hz, 2H), 7.68 (d, J = 7.7 Hz, 2H); 13C NMR (100 MHz; CDCl3) δ: 21.6 (CH3), 25.1 (CH2), 42.7 (CH2), 44.8 (CH2), 122.8 (CH), 125.0 (CH), 127.6 (CH), 129.6 (CH), 133.3 (C), 143.5 (C); GC-MS (EI) m/z (relative intensity) 237 (60) [M+], 155 (31), 91 (70), 82 (100), 55 (50). 2f:12 yield 69% (173 mg), white solid (mp 60−63 °C); 1H NMR (400 MHz; CDCl3) δ: 2.32 (d, J = 4.5 Hz, 4H), 2.42 (s, 8870
DOI: 10.1021/acsomega.8b01642 ACS Omega 2018, 3, 8865−8873
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(d) Gradillas, A.; Pérez-Castells, J. Macrocyclization by Ring-Closing Metathesis in the Total Synthesis of Natural Products: Reaction Conditions and Limitations. Angew. Chem., Int. Ed. 2006, 45, 6086− 6101. (e) van Otterlo, W. A. L.; de Koning, C. B. Metathesis in the Synthesis of Aromatic Compounds. Chem. Rev. 2009, 109, 3743− 3782. (f) Grubbs, R. H.; Miller, S. J.; Fu, G. C. Ring-Closing Metathesis and Related Processes in Organic Synthesis. Acc. Chem. Res. 1995, 28, 446−452. (g) Higman, C. S.; Lummiss, J. A. M.; Fogg, D. E. Olefin Metathesis at the Dawn of Implementation in Pharmaceutical and Specialty-Chemicals Manufacturing. Angew. Chem., Int. Ed. 2016, 55, 3552−3565. (h) Synthesis of Heterocycles by Metathesis Reactions. In Topics in Heterocyclic Chemistry; Prunet, J., Ed.; Springer: Switzerland, 2017; Vol. 47. (i) Herndon, J. W. The chemistry of the carbon-transition metal double and triple bond: Annual survey covering the year 2015. Coord. Chem. Rev. 2016, 329, 53−162. (j) Chauvin, Y. Olefin Metathesis: The Early Days (Nobel Lecture). Angew. Chem., Int. Ed. 2006, 45, 3740−3747. (k) Grubbs, R. H. Olefin-Metathesis Catalysts for the Preparation of Molecules and Materials (Nobel Lecture). Angew. Chem., Int. Ed. 2006, 45, 3760− 3765. (l) Schrock, R. R. Multiple Metal−Carbon Bonds for Catalytic Metathesis Reactions (Nobel Lecture). Angew. Chem., Int. Ed. 2006, 45, 3748−3759. (2) (a) Hřebabecký, H.; Procházková, E.; Š ála, M.; Plačková, P.; Tloušt’ová, E.; Barauskas, O.; Lee, Y.-J.; Tian, Y.; Mackman, R.; Nencka, R. Synthesis and biological evaluation of conformationally restricted adenine bicycloribonucleosides. Org. Biomol. Chem. 2015, 13, 9300−9313. (b) Kongkathip, B.; Akkarasamiyo, S.; Kongkathip, N. A new and efficient asymmetric synthesis of oseltamivir phosphate (Tamiflu) from D-glucose. Tetrahedron 2015, 71, 2393−2399. (c) Lampa, A.; Alogheli, H.; Ehrenberg, A. E.; Åkerblom, E.; Svensson, R.; Artursson, P.; Danielson, U. H.; Karlén, A.; Sandström, A. Vinylated linear P2 pyrimidinyloxyphenylglycine based inhibitors of the HCV NS3/4A protease and corresponding macrocycles. Bioorg. Med. Chem. 2014, 22, 6595−6615. (d) Donohoe, T. J.; Jones, C. R.; Kornahrens, A. F.; Barbosa, L. C. A.; Walport, L. J.; Tatton, M. R.; O’Hagan, M.; Rathi, A. H.; Baker, D. B. Total Synthesis of the Antitumor Antibiotic (±)-Streptonigrin: First-and Second-Generation Routes for de Novo Pyridine Formation Using Ring-Closing Metathesis. J. Org. Chem. 2013, 78, 12338−12350. (e) Zhang, W.; Chen, Y.; Liang, Q.; Li, H.; Jin, H.; Zhang, L.; Meng, X.; Li, Z. Design, Synthesis, and Antibacterial Activities of Conformationally Constrained Kanamycin A Derivatives. J. Org. Chem. 2013, 78, 400−409. (f) Angulo-Pachón, C. A.; Díaz-Oltra, S.; Murga, J.; Carda, M.; Marco, J. A. Stereoselective Synthesis and Structural Correction of the Naturally Occurring Lactone Stagonolide G. Org. Lett. 2010, 12, 5752−5755. (g) Clive, D. L. J.; Yu, M.; Sannigrahi, M. Synthesis of Optically Pure (+)-Puraquinonic Acid and Assignment of Absolute Configuration to Natural (-)-Puraquinonic Acid. Use of Radical Cyclization for Asymmetric Generation of a Quaternary Center. J. Org. Chem. 2004, 69, 4116−4125. (h) Jo, H.; Choi, M.; Viji, M.; Lee, Y. H.; Kwak, Y.-S.; Lee, K.; Choi, N. S.; Lee, Y.-J.; Lee, H.; Hong, J. T.; Lee, M. K.; Jung, J.-K. Concise Synthesis of Broussonone A. Molecules 2015, 20, 15966−15975. (3) (a) Schrock, R. R.; Murdzek, J. S.; Bazan, G. C.; Robbins, J.; DiMare, M.; O’Regan, M. Synthesis of Molybdenum Imido Alkylidene Complexes and Some Reactions Involving Acyclic Olefins. J. Am. Chem. Soc. 1990, 112, 3875−3886. (b) Gessler, S.; Randl, S.; Blechert, S. Synthesis and metathesis reactions of a phosphine-free dihydroimidazole carbine ruthenium complex. Tetrahedron Lett. 2000, 41, 9973−9976. (c) Wakamatsu, H.; Blechert, S. A Highly Active and Air-Stable Ruthenium Complex for Olefin Metathesis. Angew. Chem., Int. Ed. 2002, 41, 794−796. (d) Wakamatsu, H.; Blechert, S. A New Highly Efficient Ruthenium Metathesis Catalyst. Angew. Chem., Int. Ed. 2002, 41, 2403−2405. (e) Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J., Jr.; Hoveyda, A. H. A Recyclable Ru-Based Metathesis Catalyst. J. Am. Chem. Soc. 1999, 121, 791−799. (f) Garber, S. B.; Kingsbury, J. S.; Gray, B. L.; Hoveyda, A. H. Efficient and Recyclable Monomeric and Dendritic Ru-Based Metathesis Catalysts. J. Am. Chem. Soc. 2000, 122, 8168−8179.
127.8 (CH), 172.2 (C); GC-MS (EI) m/z (relative intensity) 212 (19) [M+], 79 (51), 66 (80), 55 (9), 29 (100). 5ab: A mixture composed of THF (1.5 mL), Zn (196 mg, 3.0 mmol), and TMSCl (108 mg, 1.0 mmol) was stirred for 10 min at room temperature under an Ar atmosphere. Thereafter, PhCHCl2 (162 mg, 1.0 mmol) was added to the mixture and stirred for 10 min at 60 °C. The mixture turned color slightly to grayish brown. NbCl5 (54 mg, 0.2 mmol) in THF (1.5 mL) was added to the solution and stirred for 5 min resulting in the mixture turning color from dark violet to dark brown. Finally, 1-dodecene (3a, 168 mg, 1 mmol) and the substrate vinylcyclohexane (3b, 1102 mg, 10 mmol) were added to the solution and stirred for 2 h at 60 °C. The yield of the metathesis product (5ab, 22%) was estimated from the peak areas based on an internal standard technique using GC and tridecane as the internal standard. The cross-metathesis product (5ab) was isolated (9% yield, 24 mg) by column chromatography (silica gel (25 cc)/n-hexane/EtOAc = 100:0− 4:1) and Kugel-Rohr distillation (pot temperature 100−110 °C), as a colorless oil; 1H NMR (400 MHz; CDCl3) δ: 0.88 (t, J = 6.8 Hz, 3H), 1.32−1.02 (m, 21H), 1.72−1.61 (m, 5H), 1.97−1.93 (m, 3H), 5.35−5.33 (m, 2H); 13C NMR (100 MHz; CDCl3) δ: 14.1 (CH3), 22.7 (CH2), 26.1 (CH2), 26.2 (CH2), 29.1 (CH2), 29.4 (CH2), 29.5 (CH2), 29.64 (CH2), 29.65 (2CH2), 29.70 (CH2), 31.9 (CH2), 32.7 (CH2), 33.3 (2CH2), 40.7 (CH), 127.7 (CH), 136.4 (CH); IR (neat, cm−1) 2924, 1449, 967; GC-MS (EI) m/z (relative intensity) 250 (16) [M+], 109 (43), 96 (100), 81 (82), 67 (65); HRMS (EI) m/z calcd for C18H34 [M]+ 250.2661, found 250.2662.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsomega.8b01642. NMR characterization data of compunds (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Yasushi Obora: 0000-0003-3702-9969 Author Contributions
The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported partly by JSPS KAKENHI Grant Number 16K05784. High-resolution mass spectra were performed at Global Facility Center, Hokkaido University.
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REFERENCES
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DOI: 10.1021/acsomega.8b01642 ACS Omega 2018, 3, 8865−8873
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DOI: 10.1021/acsomega.8b01642 ACS Omega 2018, 3, 8865−8873
