Structural Elucidation of Sumanene and Generation of its Benzylic Anions

Transcription

1 Structural Elucidation of Sumanene and Generation of its Benzylic Anions idehiro Sakurai, Taro Daiko, iroyuki Sakane, Toru Amaya, and Toshikazu irao Department of Applied Chemistry, Graduate School of Engineering, Osaka University Yamada-oka, Suita, Osaka , Japan Supporting Information General. Melting points were determined on a Yanagimoto Micromelting Point Apparatus and were uncorrected. 1 (600 Mz) and 13 C (150 Mz) NMR spectra were measured on a Varian INOVA 600 spectrometer. CDCl 3 and TF-d 8 were used as a solvent and residual solvent peak (δ=7.26 for CDCl 3, 3.58 for TF-d 8 ; 13 C, 77.0 ppm for CDCl 3, 67.4 ppm for TF-d 8 ) were used as an internal standard. Infrared spectra were recorded on JASCO FT/IR-480plus. Mass spectra were measured on a JEOL JMS-DX-303 spectrometer using either electron impact (EI) or chemical ionization (CI) modes. Elemental analyses were carried out at the Analytical Center, Graduate School of Engineering, Osaka University. Column chromatography was conducted on silica gel (Wakogel C-200) and preparative TLC was carried out using Wakogel B-5F. GPC was performed with Japan Analytical Industry LC-908 using chloroform as a solvent. All reagents and solvents were purchased from commercial sources and were further purified with the standard methods, if necessary. Sumanene (1): 1 A well-dried 200 ml three-necked round-bottomed flask equipped with a magnetic stirring bar, a rubber septum, and a reflux condenser was charged with syn-benzotris(norbornadiene) 2,3 (63 mg, 0.23 mmol) in toluene (100 ml). The flask was chilled to 0 C and purged with an atmospheric pressure of ethylene gas. To the solution was added Cl 2 (PCy 3 ) 2 Ru=CPh (18.9 mg, 10 mol%) and the mixture was stirred at room temperature for 24 h. The solution was passed through short silica gel column, then the solvent was evaporated in vacuo. Purification by PTLC (hexane/toluene = 5/1) then GPC gave hexahydrosumanene as a colorless solid (18.9 mg, 30% yield). Mp 180 C (dec.); IR (KBr) 3010, 2920, 2848, 1596 cm -1 ; 1 NMR (300 Mz, CDCl 3 ) δ = 0.96 (3, dt, J = 10.2 and 11.4 z), 2.79 (3, dt, J = 7.4 and 11.4 z), 3.81 (6, br dd, J = 7.4 and 10.2 z), 5.69 (6, s); 13 C NMR (75 z, CDCl 3 ) 40.4, 43.7, 129.3, ppm; RMS Found: m/z Calcd for C : M, A two-necked round-bottomed flask equipped with a magnetic stirring bar and a reflux condenser was charged with hexahydrosumanene (4.1 mg, mmol) in toluene (3 ml), then DDQ (20.2 mg, mmol) in toluene (1.5 ml). The mixture was heated to reflux for 3 h. S1

2 After evaporation of the solvent, the crude product was purified by PTLC (hexane) to give sumanene (1) as a colorless solid (2.8 mg, 70% yield). Mp >290 C (sealed capillary under argon); IR (KBr) 2950, 2923, 1558 cm -1 ; 1 NMR (300 Mz, CDCl 3 ) δ = 3.42 (6, d, J = 19.5 z), 4.71 (6, d, J = 19.5 z), 7.01 (6, s); 13 C NMR (75 z, CDCl 3 ) 41.8, 123.2, 148.6, ppm; Found: C 95.22,. 4.77%, Calcd for C : C 95.42,. 4.58%; RMS Found: m/z Calcd for C : M, References 1) Sakurai,.; Daiko, T.; irao, T. Science, 2003, 301, ) Durr, R.; De Lucchi, O.; Cossu, S.; Lucchini, V. Chem. Commun. 1996, ) Borsato, G.; De Lucchi, O.; Cossu, S.; Groppo, L.; Lucchini, V.; Zambon, A. J. Org. Chem. 2002, 67, X-ray crystallography of sumanene (1): All measurements for 1 was made on a Rigaku RAXIS-RAPID imaging plate diffractometer with graphite-monochromated Mo Kα radiation. The structure of 1 was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically. The atoms were placed in idealized positions and allowed to ride with the C atoms to which each was bonded. Crystallographic details are given in the attached CIF file. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC for 1. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: (internat.) / ; deposit@ccdc.cam.ac.uk]. Generation of the anions 2-4, and the preparation of 5: All operations of the anion generation except NMR measurement were carried out under dry nitrogen. Sumanene (1, 4.6 mg, 1.7 x 10-2 mmol) was charged in an NMR tube (treated with 10% aqueous N 3, and dried completely before use) attached with a resealable J-Young valve. TF-d 8 (0.6 ml, dried on Na/benzophenone) was introduced via syringe. After the tube was chilled to below 80 C using liq. nitrogen/silica gel bath, t-buli (12.0 µl, 1.7 x 10-2 mmol, 1 equiv, 1.47 M in pentane) was added via syringe. The tube was shaken for several minutes at the same temperature. t-buli (8.4 µl, 1.2 x 10-2 mmol, 0.7 equiv, 1.47 M in pentane) was further added at below -80 C, and the tube was shaken for a few minutes at the same temperature. The temperature was allowed to warm to room temperature. 1 - and 13 C-NMR measurement revealed the generation of the monoanion 2. The same procedure was repeated to measure the dianion 3 and trianion 4. 1 equiv of t-buli (12.0 µl, 1.7 x 10-2 mmol) allowed the generation of dianion 3 from monoanion 2, and S2

3 further addition of 1 equiv of t-buli (12.0 µl, 1.7 x 10-2 mmol) generated trianion 4 from dianion 3. NMR data in TF-d 8. 1: 1 -NMR (600 Mz, the residual TF was used as reference, δ 3.58) δ = 7.09 (6, s, c), 4.67 (3, d, J = 18.6 z, b), 3.39 (3, d, J = 18.6 z, a); 13 C-NMR (150 Mz, TF-d 8 was used as reference, δ 67.4) 149.9, 149.6, (C), 42.1 (D) ppm. D B A C 1 2: 1 -NMR δ = 6.79 (2, d, J = 7.8 z, c), 6.75 (2, d, J = 7.8 z, b), 6.74 (2, s, f), 5.88(1, s, a), 4.48 (2, d, J = 18.6 z, d), 3.01 (2, d, J = 18.6 z, e); 13 C-NMR (C), (I), (B), (G), (D), (A), (F), (J), (E), 92.7 (K), 42.1 () ppm. K a D b A E B 2 C G F c 3: 1 -NMR δ = 6.78 (2, s, a), 6.61 (2, d, J = 7.8 z, d), 6.35 (2, d, J = 7.8 z, c), 5.38 (2, s, b), 3.91 (1, d, J = 18.6 z, e), 2.31 (1, d, J = 18.6 z, f); 13 C-NMR (C), (G), c I J (), (D), (A), (B), (E), (I), (F), 84.9 (J), 41.6 (K) ppm. d e b f a Li + f 3 e D K C B A I a E F G J d b c 2Li + 4: 1 -NMR δ = 6.30 (6, s, b), 5.26 (3, s, a); 13 C-NMR (A or B), (A or B), (C), 89.0 (D) ppm. S3

4 3Li + a D A B b C 4 Me 3 SiCl (8.9 µl, 7.0 x 10-2 mmol, 4 equiv) was added via syringe to the solution of trianion 4 at below -80 C. The tube was shaken for a few minutes at the same temperature. The temperature was allowed to warm to room temperature. 1 - and 13 C-NMR measurement indicated the exclusive formation of tris(trimethylsilyl)sumanene (5) as a sole stereoisomer. NMR data in TF-d 8. 5: 1 -NMR δ = 6.99 (6, s), 3.47 (3, s), 0.33 (27, s); 13 C-NMR 152.7, 149.5, 122.6, 52.5, -2.6 ppm. The reaction mixture was evaporated in vacuo. The residue was filtered through a short pad of silica gel. The crude product was purified by GPC to give 5. Isolated yield: quantitative (8.3 mg). 5: IR(KBr) 3037, 2959, 2917, 2849, 1738, 1446, 1398, 1261, 1245, 1076, 1054, 952, 840 cm -1 ; 1 -NMR (CDCl 3 ) δ = 6.99 (6, s, b), 3.43 (3, s, a), * 0.34 (27, s, c); 13 C-NMR (CDCl 3 ) 151.7, 148.6, (C), 52.0 (D), -2.7 (-SiMe 3 ) ppm; RMS Found: m/z Calcd for C Si 3 : M, *1 -NMR chemical shifts of methine proton of 9-TMSfluorene (model compound for 5) and methylene protons of fluorene were 3.87 and 3.91 ppm, respectively. This result shows that the shielding effect of silyl group should be small in this case. Judging from ring current effect, the benzylic protons were assigned to endo-protons as described in reference 18 in the manuscript SiMe 3 Me 3 Si c D B A C b a SiMe 3 5 Theoretical Calculations: The calculations were carried out using the Gaussian 98 program. The optimized structure of 1 (B3LYP/6-31G**) S4

5 Center Atomic Atomic Coordinates (Angstroms) Number Number Type X Y Z S5

6 The predicted chemical shifts of protons of 1 (GIAO/6-31G**//B3LYP/6-31G**) 13 C NMR ppm (B) D B A C ppm 4.58 ppm 7.19 ppm ppm ppm ppm (A) (C) (D) S6

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