Separation of Five Linearly Aligned Carbons into Two-Carbon and

Apr 6, 2016 - Five carbons linearly aligned in a dihydroindene titanium complex were separated into a two-carbon group and a three-carbon group on ...
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Separation of Five Linearly Aligned Carbons into Two-Carbon and Three-Carbon Groups on Titanium Zhiyi Song,† Yi-Fang Hsieh,† Kiyohiko Nakajima,‡ Ken-ichiro Kanno,† and Tamotsu Takahashi*,† †

Institute for Catalysis, Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo 001-0021, Japan Department of Chemistry, Aichi University of Education, Igaya, Kariya, Aichi 448-8542, Japan

‡

S Supporting Information *

ABSTRACT: Five carbons linearly aligned in a dihydroindene titanium complex were separated into a two-carbon group and a three-carbon group on titanium when the complex was treated with 2-aminopyridine. The protonolysis product, dihydroindene with two alkyl groups at both bridge-head positions, was obtained in high yield.

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ligand were cyclic in the products.12,13 We also found that the five cyclic carbons in complex 3 were cleaved on titanium and transformed to five linear carbons in dihydroindene complex 2 by a metathesis mechanism. Titanium-dihydroindene derivatives using a bicyclic titanacyclopentadiene similar to 2 have been reported in a pioneering work by Rosenthal and his group,14−16 and the five linearly aligned carbons in 1 originating from the Cp ligand of titanacyclopentadiene 3 have been confirmed by 13C labeling experiments by our group.17−21 However, a still mysterious step remaining is the separation of the five linearly arranged carbons in 2 into a two-carbon group and a three-carbon group. In this paper we report that the five linearly aligned carbons in 2 were separated into a two-carbon group and a three-carbon group on titanium (Scheme 1).

INTRODUCTION The carbon−carbon bond cleavage reaction is a challenge in organic chemistry. Observation of the carbon−carbon bond cleavage step on a transition metal is important and useful to understand the transformation.1−10 We have reported the carbon−carbon bond cleavage reaction of a Cp ligand on titanacyclopentadiene 1 into a two-carbon group and a three-carbon group.11 The two-carbon group was converted to a benzene derivative and the three-carbon group was converted to a pyridine derivative on titanium as shown in eq 1. Monitoring the reaction by NMR revealed the formation

Scheme 1. Separation of Five Linearly Arranged Carbons in 2 into a Two-Carbon Group and a Three-Carbon Group (This Work) of an intermediate 2, where the five carbons originating from the Cp ligand were linearly arranged in the dihydroindenyltitanium complex 2. We have investigated and found that a Cp ligand of titanacyclopentadienes coupled with the diene moiety of 1 to form dihydroindene derivative 3 where the five carbons are cyclic, as shown in eq 2. Although complex 3 was not directly

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RESULTS AND DISCUSSION During our further investigation we found that the five linearly arranged carbons in complex 2a were separated into a twocarbon group and a three-carbon group.18 Compound 4a was detected, when 1 was treated with TiCl4 and azobenzene, chlorodihydroindenes and indene derivatives were obtained, respectively, where the five carbons originated from the Cp © 2016 American Chemical Society

Received: February 10, 2016 Published: April 6, 2016 1092

DOI: 10.1021/acs.organomet.6b00112 Organometallics 2016, 35, 1092−1097

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Organometallics obtained in 90% yield when complex 2a was treated with 2aminopyridine at 60 °C for 6 h (Scheme 2). Scheme 2. Reaction of 2a with 2-Aminopyridine

These five carbons were monitored by a 13C labeling experiment (Scheme 3). Addition of aminopyridine to the Scheme 3. Reaction of 2a-13C with 2-Aminopyridine

titanium-dihydroindene derivative 2a separated the five linear carbons into a two-carbon group and a three-carbon group in the product 4 as shown in Scheme 3. The separation of five carbons in the dihydroindene 2 was verified by a 13C labeling experiment of the dihydroindene derivative. On the other hand, as a control, complex 2a-13C was protonated with carboxylic acid to give 5a-13C in 56% yield. 13 C NMR of 4a-13C showed two sp3 quaternary carbons at its bridge-head positions. This is in contrast to 5a-13C, which had only one sp3 quaternary carbon at its bridge-head positions. It also revealed that 5a-13C had four olefinic CH carbons, while 5a-13C had three such carbons. 13 C NMR spectra of 5a-13C and 4a-13C are shown in Figure 1. In the NMR spectrum of 5a-13C, five carbons at 41.8, 43.5, 122.7, 131.5, and 138.5 ppm were 13C labeled. These carbons were assigned to the allyl moiety of a five-membered ring, one of the bridgehead carbons, and one carbon of a six-membered ring. These five carbons were linearly aligned. The lower spectrum in Figure 1 is for 4a-13C. The five 13C-labeled carbons were observed at 42.1, 126.8, 127.2, 127.8, and 136.6 ppm. These signals were assigned to the allyl moiety on the fivemembered ring and two carbons on the six-membered ring. This indicated that the five linear carbons in 2a were separated in 4a as two carbons in the six-membered ring and three carbons in the five-membered ring, as shown in Scheme 3. In addition, the product 4b (R = Pr) was converted to compound 6 by Diels−Alder reaction with tetracyanoethylene (TCNE) (Scheme 4). The X-ray structure of 6 clearly showed a dihydroindene adduct with TCNE with Pr substituents at both of the bridge-head carbons as expected (Figure 2). The other two Pr groups were located at the six-membered-ring moiety. When complex 2a was hydrolyzed to 5a and subsequently heated together with aminopyridine, compound 4a was not formed. Compound 4a was not produced from 5a in the reaction mixture. This result indicated that the indene moiety on 2a had rearranged on titanium before hydrolysis. In order to make clear this point, deuteration experiments were carried out as shown in Scheme 5. Treatment of 2a with deuterated 2aminopyridine and then with HCl gave 4a-D in 87% NMR

Figure 1. 13C NMR spectra of 5a-13C (upper) and 4a-13C (lower).

Scheme 4. Diels−Alder Reaction of 4b with TCNE

Figure 2. X-ray structure of adduct 6.

Scheme 5. Deuterated Experiments

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Organometallics yield. The D incorporation at the allyl moiety of the fivemembered ring was 86%. In contrast, the reaction of nondeuterated 2-aminopyridine and then with DCl did not give any deuterated 4a. This means that after the transformation on titanium the titanium−carbon bond was quenched with a proton of the NH group of 2-aminopyridine and dihydroindene 4a was formed in the reaction. Table 1 summarizes the reaction of titanium dihydroindene derivatives with aminopyridine derivatives. Reagents with a NC-NH2 moiety similar to 2,6-diaminopyridine, 5-chloro-2-

aminopyridine, or 2-aminobenzothiazole gave product 4a in 62−95% yields. This reaction requires NH groups for protonolysis at the end of the reaction as discussed above. When dimethylaminopyridine was used, the reaction did not proceed at all. A low yield of 11% given by Nmethylaminopyridine was due to the poor coordination to the titanium metal center. Aminopyridine has two roles. One is coordination to titanium to induce the transformation of the dihydroindenyl moiety to give a more stable structure of the titanium complex. The other is protonolysis of the complex to remove the rearranged dihydroindene moiety. Furthermore, the relation of the two nitrogen atoms was important. For example, 4-amino-, 2-aminomethyl-, or 2aminoethyl-pyridine derivatives did not give 4a under the same conditions. However, the two roles could be separated. For example, a mixture of bipyridine and aniline afforded a high yield of 4a′ (a double-bond positional isomer of 4a) from 2a. Under the typical conditions, dihydroindene titanium complex 2b was treated with aminopyridine to give 4b in a comparable high yield of 98%. In addition, tricyclic complex 2c was converted to the corresponding product 4c in 38% isolated yield. This low yield was probably due to the rigid structure of the tricyclic skeleton. The structure of 4c was determined by NMR and HRMS and further confirmed by X-ray analysis after reaction with TCNE (Scheme 6, Figure 3). In the tricyclic structure of 4c, one Et was on the six-membered ring and the other was on the bridge-head carbon.

Table 1. Reactions of Titanium-Dihydroindenyl Complexes with Aminopyridine Derivativesa,b

Scheme 6. Diels−Alder Reaction of 4c with TCNE

Figure 3. X-ray structure of the TCNE adduct of 4c.

Furthermore, when methyl-substituted complex 2d was employed, compound 4d was obtained in 63% isolated yield under the conditions used here. Recently we have proposed a reaction mechanism via a metathesis process for the conversion of titanium complex 3, where the five carbons are cyclic, to complex 2, where the five carbons are linear.13 Complex 3 has a titanacyclobutane moiety. Therefore, titanium carbene and an olefin are formed and rearrange to complex 2, as shown in Scheme 7. The transformation reported here can be explained by the same mechanism via metathesis. Complex 2 also has a titanacyclobutane moiety. This is again converted to titanium

a

Conditions: complexes 2 reacted with 2 equiv of aminopyridines in THF at 60 °C for 6 h. The reaction with bipyridine and aniline was carried out at 60 °C for 8 h. bYields: NMR yield. Isolated yields are given in parentheses. 1094

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Organometallics

Cp2TiCl2 (298 mg, 1.2 mmol) in THF (5 mL) was cooled to −78 °C. n-BuLi (1.59 M solution in hexane, 1.5 mL, 2.4 mmol) was added dropwise to this solution. After stirring for 1 h at −78 °C, 3-hexyne (0.23 mL, 2.0 mmol) was added and the mixture was stirred for 3 h at −10 °C. The color of the reaction mixture turned to dark green to form the corresponding titanacyclopentadiene 1a. Heating the solution at 60 °C for 6 h afforded dihydroindenyltitanium complex 2a. This solution of complex 2a was treated with 2.2 equiv of 2-aminopyridine (216 mg, 2.2 mmol) at 60 °C for 6 h. After cooling to room temperature, hexane (10 mL) and water (10 mL) were added to the mixture directly. The separated water phase was extracted with hexane (10 mL) three times. The combined organic phase was washed with water, aqueous saturated NaHCO3 solution, and brine and dried over anhydrous sodium sulfate. After removal of the solvent in vacuo, the residue was purified by column chromatography on silica gel with hexane as an eluent to afford the title compound 4a (198 mg, 86% isolated yield, 90% NMR yield) as a colorless oil. 4a: 1H NMR (C6D6, Me4Si): 0.92 (t, J = 7.5 Hz, 3H), 0.93 (t, J = 7.5 Hz, 3H), 1.00 (t, J = 7.5 Hz, 3H), 1.01 (t, J = 7.5 Hz, 3H), 1.33−1.63 (m, 4H), 1.72−1.87 (m, 1H), 1.91−2.06 (m, 1H), 2.06−2.25 (m, 3H), 2.46 (dd, J = 15.6 Hz, 3.0 Hz, 1H), 5.44 (dd, J = 5.9 Hz, 3.0 Hz, 1H), 5.66−5.72 (m, 1H), 5.71 (d, J = 9.5 Hz, 1H), 5.77 (d, J = 9.5 Hz, 1H). 13C NMR (C6D6, Me4Si): 9.0 (CH3), 9.8 (CH3), 13.9 (CH3), 16.0 (CH3), 21.8 (CH2), 25.7 (CH2), 26.5 (CH2), 27.0 (CH2), 42.1 (CH2), 51.9 (C), 56.1 (C), 126.8 (CH), 127.2 (CH), 127.8 (CH), 132.5 (C), 135.9 (C), 136.6 (CH). HRMS: [M]+ calcd for C17H26 230.2035, found 230.2024. 3a,6,7,7a-Tetrapropyl-3a,7a-dihydro-1H-indene (4b). Compound 4b was obtained as a colorless oil (257 mg, 90% isolated yield, 98% NMR yield). 4b: 1H NMR (C6D6, Me4Si): 0.84−0.98 (m, 12H), 1.20−1.67 (m, 12H), 1.73−1.86 (m, 1H), 1.93−2.06 (m, 1H), 2.07− 2.26 (m, 3H), 2.48 (dd, J = 15.8 Hz, 3.0 Hz, 1H), 5.46 (dd, J = 5.8 Hz, 3.0 Hz, 1H), 5.67−5.72 (m, 1H), 5.72 (d, J = 9.9 Hz, 1H), 5.80 (d, J = 9.9 Hz, 1H). 13C NMR (C6D6, Me4Si): 14.5 (CH3), 15.1 (CH3), 15.4 (CH3), 15.5 (CH3), 18.0 (CH2), 18.4 (CH2), 22.7 (CH2), 25.1 (CH2), 32.1 (CH2), 34.9 (CH2), 36.9 (CH2), 37.4 (CH2), 42.2 (CH2), 52.0 (C), 56.0 (C), 127.0 (CH), 127.5 (CH), 127.6 (CH), 130.8 (C), 136.0 (C), 137.0 (CH). HRMS: [M]+ calcd for C21H34 286.2661, found 286.2644. 3a,6-Diethyl-1,3a,7,8,9,10-hexahydrocyclopenta[d]naphthalene (4c). Compound 4c was obtained as a colorless oil (87 mg, 38% isolated yield). 4c: 1H NMR (C6D6, Me4Si): 0.94 (t, J = 7.5 Hz, 3H), 0.96 (t, J = 7.5 Hz, 3H), 1.13−1.73 (m, 7H), 1.73−1.90 (m, 1H), 1.92−2.14 (m, 3H), 2.25−2.36 (m, 1H), 2.45−2.67 (m, 2H), 5.24 (d, J = 9.5 Hz, 1H), 5.49 (ddd, J = 5.9 Hz, 2.7 Hz, 1.0 Hz, 1H), 5.79 (d, J = 9.5 Hz, 1H), 5.75−5.83 (m, 1H). 13C NMR (C6D6, Me4Si): 8.6 (CH3), 13.9 (CH3), 32.6 (CH2), 25.5(CH2), 27.1 (CH2*2), 28.0 (CH2), 31.0(CH2), 46.0 (CH2), 48.5 (C), 53.8 (C), 125.5 (CH), 127.3 (C), 127.8 (CH), 131.0 (CH), 136.1 (C), 138.0 (CH). HRMS: [M]+ calcd for C17H24 228.1878, found 228.1875. Reaction of Dihydroindenyltitanium Complex 2a-13C with 2Aminopyridine. 13C-Enriched titanacyclopentadiene was prepared by our reported method.11 The reaction of dihydroindenyltitanium complex 2a-13C with 2-aminopyridine was carried out in the same way as above-described. 1H and 13C NMR spectra showed the formation of dihydroindene 4a-13C in 80% yield. 4a-13C: 13C NMR (inverse gate, C6D6, Me4Si): 9.0 (CH3), 9.8 (CH3), 13.9 (CH3), 16.0 (CH3), 21.8 (CH2), 25.7 (CH2), 26.5 (CH2), 27.0 (CH2), 42.1 (CH2), 51.9 (C), 56.1 (C), 126.8 (CH), 127.2 (CH), 127.8 (CH), 132.5 (C), 135.9 (C), 136.6 (CH). (Underlined peaks were characterized by 13Cenriched carbons when using 13C-enriched Cp2TiCl2.) Reaction of Dihydroindenyltitanium Complex 2a with Dideuterated 2- Aminopyridine to form 1-2H-3a,6,7,7a-Tetraethyl-3a,7adihydro-1H-indene (4a-D). [The deuterated aminopyridine was synthesized by a reported method.26 2-Aminopyridine was dissolved in an excess of deuterated water (10-fold) for 2 h before removing the solvent by rotary evaporator. This process was repeated three times.] A THF solution of dihydroindenyltitanium complex 2a was treated with 2.2 equiv of deuterated 2-aminopyridine (216 mg, 2.2 mmol) at 60 °C for 6 h. The same workup as above afforded compound 4a-D

Scheme 7. Reaction Mechanism from 3 to 2 via a Metathesis Mechanism

carbene and an olefin from 2.22−25 As shown in Scheme 8, the complex similarly converted to complex 10. Scheme 8. Possible Mechanism for the Formation of 4 from 2 via a Metathesis Process

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CONCLUSIONS Treatment of a dihydroindenyl titanium complex with 2aminopyridine rearranged the structure of the dihydroindene moiety to give a dihydroindene compound. A 13C labeling experiment indicated that five carbons linearly aligned in a dihydroindene titanium complex were separated into a twocarbon group and a three-carbon group in the dihydroindene compound. This transformation could be explained by a ringopening metathesis of a titanacyclobutane moiety. Aminopyridine was considered to have two roles. One is coordinating to titanium. This leads to the rearrangement of the titanium complex. The other is protonolysis of the titanium complex.

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EXPERIMENTAL SECTION

General Information. All reactions involving organometallic compounds were carried out with standard Schlenk techniques under nitrogen. Tetrahydrofuran (THF) was distilled and dried over sodium and benzophenone under a nitrogen atmosphere. All of the reagents were commercially available and used as received unless otherwise mentioned. GC analyses were performed on a Shimadzu GC-14B equipped with a flame ionization detector using a Shimadzu capillary column (CBPI-M25-025). The GC yields were determined using n-decane as internal standard. 1H and 13C NMR spectra were recorded for CDCl3 or C6D6 solution on a JEOL JNM-AL300 NMR spectrometer. Tetramethylsilane was used as the reference for 1H and 13 C NMR. The NMR yields were determined using dichloromethane as an internal standard. Representative Procedure for Reaction of Dihydroindenyltitanium Complexes 2 with 2-Aminopyridine. Formation of 3a,6,7,7a-Tetraethyl-3a,7a-dihydro-1H-indene (4a). A solution of 1095

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Organometallics (188 mg, 81% isolated yield, 87% NMR yield) as a colorless oil. 4a-D: D incorporation: 86%. 1H NMR (C6D6, Me4Si): 0.93 (t, J = 7.5 Hz, 3H), 0.94 (t, J = 7.5 Hz, 3H), 1.00 (t, J = 7.5 Hz, 3H), 1.01 (t, J = 7.5 Hz, 3H), 1.30−1.64 (m, 4H), 1.72−1.88 (m, 1H), 1.91−2.05 (m, 1H), 2.06−2.26 (m, 3H), 5.45 (dd, J = 5.9 Hz, 3.0 Hz, 1H), 5.69 (dd, J = 5.9 Hz, 1.7 Hz, 1H), 5.72 (d, J = 9.7 Hz, 1H), 5.78 (d, J = 9.7 Hz, 1H). 13 C NMR (C6D6, Me4Si): 9.0 (CH3), 9.8 (CH3), 13.9 (CH3), 16.0 (CH3), 21.8 (CH2), 25.7 (CH2), 26.5 (CH2), 27.0 (CH2), 41.7 (t, 1 JC‑D = 21 Hz), 51.9 (C), 56.1 (C), 126.8 (CH), 127.2 (CH), 127.8 (CH), 132.5 (C), 135.9 (C), 136.6 (CH). HRMS: [M]+ calcd for C17H252H 231.2097, found 231.2087. Reaction of Dihydroindene 4b with Tetracyanoethylene to Form 3a,7,7a,8-Tetrapropyl-3a,4,7,7a-tetrahydro-1H-4,7-ethanoindene5,5,6,6,-tetracarbonitrile (6). A 10 mL toluene solution of dihydroindene 4b (286 mg, 1.0 mmol) was added with tetracyanoethylene (320 mg, 2.5 mmol). The solution was heated at 110 °C for 24 h in air. After cooling to room temperature, the mixture was concentrated. The residue was purified by silica gel chromatography (hexane/ethyl acetate = 3:1 as eluent) to afford the corresponding tetracyanoethylene adduct 6 (290 mg, 70% isolated yield, 82% NMR yield). Light pink crystals were obtained from a hexane solution by a simple evaporation. 6: 1H NMR (CDCl3, Me4Si): 0.57 (t, J = 7.0 Hz, 3H), 0.62−0.99 (m, 16H), 1.02−1.34 (m, 4H), 1.40−1.56 (m, 1H), 1.66−1.87 (m, 1H), 1.93−2.24 (m, 5H), 3.04 (d, J = 7.2 Hz, 1H), 3.31 (dt, J = 19.2 Hz, 2.0 Hz, 1H), 5.56−5.83 (m, 2H). 13C NMR (CDCl3, Me4Si): 13.6 (CH3), 14.9 (CH3), 15.1 (CH3), 15.5 (CH3), 18.8 (CH2), 19.7 (CH2), 19.8 (CH2), 20.1 (CH2), 34.9 (CH2), 35.6 (CH2), 37.0 (CH2), 38.9 (CH2), 39.3 (CH2), 44.1 (C), 44.6 (CH), 45.9 (C), 54.4 (C), 55.3 (C), 59.5 (C), 113.1 (C), 113.6 (C), 114.1 (C), 114.3 (C), 124.7 (CH), 134.1 (CH), 134.2 (CH), 149.5 (C). HRMS: [M + H]+ calcd for C27H35N4 415.2862, found 415.2855. Reaction of Dihydroindene 4c with Tetracyanoethylene to form 3a,6-Diethyl-3,3a,7,8,9,10-hexahydrocyclopenta[d]naphthaleneTCNE Adduct. This tetracyanoethylene adduct (180 mg, 51% isolated yield, 62% NMR yield) was obtained by a similar procedure to that described for compound 10. Colorless crystals were obtained from the hexane solution. Adduct: 1H NMR (C6D6, Me4Si): 0.75 (t, J = 7.3 Hz, 3H), 0.81 (t, J = 7.3 Hz, 3H), 1.07−1.54 (m, 7H), 1.69 (dt, J = 17.6 Hz, 1.8 Hz, 1H), 1.77−2.28 (m, 6H), 2.72 (d, J = 7.2 Hz, 1H), 4.98 (dt, J = 6.1 Hz, 2.2 Hz, 1H), 5.04 (dt, J = 5.9 Hz, 2.4 Hz, 1H), 5.60 (dt, J = 7.2 Hz, 2.2 Hz, 1H). 13C NMR (C6D6, Me4Si): 9.9 (CH3), 10.2 (CH3), 19.0 (CH2), 20.6 (CH2), 25.1 (CH2), 26.5 (CH2), 27.8 (CH2), 28.2 (CH2), 41.2 (CH), 43.8 (C), 44.3 (C), 48.5 (CH2) 48.8 (C), 51.8 (C), 56.2 (C), 112.8 (C), 112.9 (C), 113.5 (C), 114.6 (C), 126.7 (CH), 129.5 (CH), 134.2 (CH), 147.4 (C). HRMS: [M+] calcd for C23H24N4 356.2001, found 356.1991. Reaction of Dihydroindenyltitanium Complex 2d with 2Aminopyridine to Form 4d,6,7,7a-Tetraethyl-2-methyl-3a,7a-dihydro-1H-indene (4d). A solution of (MeCp)2TiCl2 (346 mg, 1.2 mmol) in THF (5 mL) was cooled to −78 °C, and n-BuLi (1.69 M in hexane, 2.4 mmol) was added dropwise to the solution. After stirring for 1 h at −78 °C, 3-hexyne (0.23 mL, 2.0 mmol) was added, and stirring at −10 °C for 3 h formed bis(methylcyclopentadienyl)titanacyclopentadiene 1d. Complex 1d was treated at 50 °C for 12 h to give the corresponding dihydroindenyltitanium complex 2d. This solution of dihydroindenyltitanium complex 2d was treated with 2.2 equiv of 2aminopyridine (216 mg, 2.2 mmol) at 60 °C for 6 h. The same workup as for 4a afforded the title compound 4d (152.9 mg, 63% isolated yield) as a colorless oil. 4d: 1H NMR (CDCl3, Me4Si): 0.73 (t, J = 7.5 Hz, 3H), 0.91 (t, J = 7.5 Hz, 3H), 0.95 (t, J = 7.5 Hz, 3H), 1.01 (t, J = 7.5 Hz, 3H), 1.21−1.61 (m, 5H), 1.65−1.74 (m, 3H), 1.79− 1.96 (m, 1H), 1.97−2.26 (m, 4H), 5.18−5.23 (m, 1H), 5.63 (d, J = 9.7 Hz, 1H), 5.74 (d, J = 10 Hz, 1H). 13C NMR (CDCl3, Me4Si): 8.6 (CH3), 9.3 (CH3), 14.0 (CH3), 15.8 (CH3), 16.7 (CH3), 21.8 (CH2), 24.4 (CH2), 25.4 (CH2), 25.6 (CH2), 48.2 (CH2), 48.6 (C), 57.5 (C), 125.5 (CH), 130.5 (C), 131.7 (CH), 131.8 (CH), 134.0 (C), 139.9 (CH). HRMS: (EI+) calcd for C18H28 244.2191, found 244.2193. Representative Procedure for Reaction of Dihydroindenyltitanium Complexes 2a with Bipyridyl and Aniline: Formation of 3a,4,5,7a-Tetraethyl-3a,7a-dihydro-1H-indene (4a′). The solution of

titanacyclopentadiene 1a, prepared from Cp2TiCl2 (298 mg, 1.2 mmol) and 3-hexyne (0.23 mL, 2.0 mmol), was heated at 60 °C for 6 h to afford the dihydroindenyltitanium complex 2a. Premixed bipyridine and aniline were added into the mixture of dihydroindenyltitanium complex 2a, and the solution was stirred at 60 °C for 8 h. The same workup as that for 4a afforded the title compound (206 mg, 90% isolated yield, 98% GC yield) as a colorless oil. 4a′: 1H NMR (CDCl3, Me4Si): 0.75 (t, J = 7.5 Hz, 3H), 0.92 (t, J = 7.5 Hz, 3H), 0.98 (t, J = 7.5 Hz, 3H), 1.02 (t, J = 7.5 Hz, 3H), 1.17−1.66 (m, 4H), 1.84− 1.99 (m, 1H), 2.01−2.22 (m, 4H), 2.34 (dd, J = 15.4 Hz, 3.3 Hz, 1H), 5.62−5.69 (m, 2H), 5.77−5.83 (m, 2H). 13C NMR (CDCl3, Me4Si): 8.5 (CH3), 9.3 (CH3), 14.0 (CH3), 16.0 (CH3), 21.7 (CH2), 24.4 (CH2), 24.7 (CH2), 25.3 (CH2), 43.9 (CH2), 48.5 (C), 57.4 (C), 125.5 (CH), 130.4 (CH), 131.0 (C), 131.6 (CH), 133.4 (C), 138.5 (CH). HRMS: [M]+ calcd for C17H26 230.2035, found 230.2034.

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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/acs.organomet.6b00112. Spectral data for all new compounds; X-ray analysis data for 6 and TCNE adducts of 4c (PDF) Crystallographic data (CIF) Crystallographic data (CIF) Crystallographic data (CIF) Crystallographic data (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) (a) Takahashi, T.; Kanno, K. Metallocene in Regio- and Steroselective Synthesis. In Topics in Organometallic Chemistry; Takahashi, T., Ed.; Springer: Berlin, 2005; Vol. 8, p 217. (b) Takahashi, T.; Ishikawa, M.; Huo, S. J. Am. Chem. Soc. 2002, 124, 388−389. (c) Takahashi, T.; Tsai, F.-Y.; Kotora, M. J. Am. Chem. Soc. 2000, 122, 4994−4995. (d) Takahashi, T.; Xi, Z.; Obora, Y.; Suzuki, N. J. Am. Chem. Soc. 1995, 117, 2665−2666. (e) Takahashi, T.; Kitamura, M.; Shen, B.; Nakajima, K. J. Am. Chem. Soc. 2000, 122, 12876−12877. (2) (a) Murakami, M.; Ito, Y. In Activation of Unreactive Bonds and Organic Synthesis; Murai, S., Ed.; Springer: Berlin, 1999; pp 97−129. (b) Crabtree, R. H. Chem. Rev. 1985, 85, 245−269. (c) Chen, F.; Wang, T.; Jiao, N. Chem. Rev. 2014, 114, 8613−8661. (d) Zhao, J.; Zhang, S.; Zhang, W.; Xi, Z. Coord. Chem. Rev. 2014, 270−271, 2−13. (e) Liu, R.; Zhou, X. J. Organomet. Chem. 2007, 692, 4424−4435. (3) Rybtchinski, B.; Milstein, D. Angew. Chem., Int. Ed. 1999, 38, 870−883. (4) Gunay, A.; Jones, W. D. J. Am. Chem. Soc. 2007, 129, 8729−8735. (5) Takemori, T.; Inagaki, A.; Suzuki, H. J. Am. Chem. Soc. 2001, 123, 1762−1763. (6) Takahashi, T.; Xi, Z.; Fischer, R.; Huo, S.; Xi, C.; Nakajima, K. J. Am. Chem. Soc. 1997, 119, 4561−4562. (7) Takahashi, T.; Fujimori, T.; Seki, T.; Saburi, T.; Uchida, Y.; Rousset, C. J.; Negishi, E. J. Chem. Soc., Chem. Commun. 1990, 182. (8) Crowe, W. E.; Vu, A. T. J. Am. Chem. Soc. 1996, 118, 5508−5509. (9) Dzwinniel, T. L.; Etkin, N.; Stryker, J. M. J. Am. Chem. Soc. 1999, 121, 10640−10641. (10) Dzwinniel, T. L.; Stryker, J. M. J. Am. Chem. Soc. 2004, 126, 9184. (11) (a) Xi, Z.; Sato, K.; Gao, Y.; Lu, J.; Takahashi, T. J. Am. Chem. Soc. 2003, 125, 9568−9569. (b) Suresh, C. H.; Koga, N. Organometallics 2006, 25, 1924−1931. 1096

DOI: 10.1021/acs.organomet.6b00112 Organometallics 2016, 35, 1092−1097

Article

Organometallics (12) Takahashi, T.; Song, Z.; Sato, K.; Kuzuba, Y.; Nakajima, K.; Kanno, K. J. Am. Chem. Soc. 2007, 129, 11678−11679. (13) Takahashi, T.; Song, Z.; Hsieh, Y.-F.; Nakajima, K.; Kanno, K. J. Am. Chem. Soc. 2008, 130, 15236−15237. (14) Tillack, A.; Baumann, W.; Lefeber, O. C.; Spannenberg, A.; Kempe, R.; Rosenthal, U. J. Organomet. Chem. 1996, 520, 187−193. (15) Rosenthal, U.; Lefeber, C.; Arndt, P.; Tillack, A.; Baumann, W.; Kempe, R.; Burlakov, V. V. J. Organomet. Chem. 1995, 503, 221−223. (16) Arndt, P.; Lefeber, C.; Kempe, R.; Tillack, A.; Rosenthal, U. Chem. Ber. 1996, 129, 1281−1285. (17) Takahashi, T.; Kuzuba, Y.; Kong, F.; Nakajima, K.; Xi, Z. J. Am. Chem. Soc. 2005, 127, 17188−17189. (18) Titanacyclopentadienes 3 were prepared according to the following literature: Sato, K.; Nishihara, Y.; Huo, S.; Xi, Z.; Takahashi, T. J. Organomet. Chem. 2001, 633, 18−26. (19) Ren, S.; Igarashi, E.; Nakajima, K.; Kanno, K.; Takahashi, T. J. Am. Chem. Soc. 2009, 131, 7492−7493. (20) Song, Z.; Hsieh, Y.-F.; Nakajima, K.; Kanno, K.; Takahashi, T. Organometallics 2011, 30, 844−851. (21) Mizukami, Y.; Li, H.; Nakajima, K.; Song, Z.; Takahashi, T. Angew. Chem., Int. Ed. 2014, 53, 8899−8903. (22) Schrock, R. R. Acc. Chem. Res. 1979, 12, 98−104. (23) Casey, C. P.; Polichnowski, S. W.; Shusterman, A. J.; Jones, C. R. J. Am. Chem. Soc. 1979, 101, 7282−7292. (24) Rubin, M. B. J. Am. Chem. Soc. 1981, 103, 7791−7792. (25) Tsuji, T.; Ishitobi, H.; Tanida, H. Bull. Chem. Soc. Jpn. 1971, 44, 2447−2453. (26) Samoylova, E.; Smith, V. R.; Ritze, H.-H.; Radloff, W.; Kabelac, M.; Schultz, T. J. Am. Chem. Soc. 2006, 128, 15652−15656.

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