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Synlett 2006(18): 2914-2920  
DOI: 10.1055/s-2006-951497
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of a Benzoannelated Spheriphane (Globular Cyclophane) on the Way to Potential Precursors of C60-Fullerene

Jens Nierle, Dietmar Kuck*
Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany
e-Mail: dietmar.kuck@uni-bielefeld.de;
Further Information

Publication History

Received 18 April 2006
Publication Date:
25 October 2006 (online)

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Abstract

A viable route to the novel globular cyclophane 2, a C48H36-spheriphane, is presented as a result of our research aimed at the synthesis of the hypothetical deciphenyl 3, a C60H36-spheri­phane, which has been envisaged as a potential precursor to C60-fullerene. Several syntheses of the key intermediate of the route to 2, viz. septiphenyl 13 (C48H42), a sterically crowded 1,3,5-tris(ortho-biphenylyl)benzene derivative, are described. These include threefold Heck coupling and related threefold Pd(0)-catalyzed C-C cross-coupling reactions, as well as threefold benzoannelation involving tetrachlorothiophene-S,S-dioxide and PET-induced dehalogenation of highly chlorinated septiphenyl derivatives.

Key words

Heck reaction - cross-coupling reactions - benzoannulation - dehalogenation - photochemistry - cyclophanes - biaryl hydrocarbons

    References and Notes

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15

Kuck, D. Chem. Rev. 2006, 106, in press.

23

1,3,5-Tris[2-(3,5-dimethylphenyl)ethen-1-yl)benzene ( 6).
A mixture of 1,3,5-tribromobenzene (4, 4.72 g, 15.0 mmol), 3,5-dimethylstyrene (5, [22] 7.92 g, 60.0 mmol), Pd(OAc)2 [134.7 mg, 0.60 mmol (1%)], PPh3 (314.7 mg, 1.20 mmol) and Et3N (40 mL) was stirred under argon and heated to reflux for 72 h. After this period, the solvent was removed under reduced pressure and the residue was extracted with warm n-hexane, yielding the crude product as a yellow solid. Recrystallization from PE gave compound 6 as a colorless solid (3.08 g, 44%); mp 240 °C. 1H NMR (300 MHz, CDCl3): δ = 7.52 (s, 3 H), 7.18 (s, 6 H), 7.13 (s, 6 H), 6.93 (s, 3 H), 2.35 (s, 18 H). 13C NMR (75 MHz, CDCl3): δ = 138.20 (q), 138.16 (q), 137.22 (q), 129.55 (t), 129.43 (t), 128.07 (t), 124.54 (t), 123.76 (t), 21.33 (p). MS (EI, 70 eV): m/z (%) = 468 (100) [M+•], 241 (6), 119 (9).

25

1,3,5-Tris[6-(3,5-dimethylphenyl)-2,3,4,5-tetrachloro-cyclohexa-2,4-dien-1-yl]benzene ( 8).
A mixture of tristilbene 6 (750 mg, 1.6 mmol), tetrachlorothiophene-(S,S)-dioxide (7, 1230 mg, 4.8 mmol) and xylenes (3.1 mL) was heated to 150 °C for 46 h. The product mixture was impregnated on silica gel and then subjected to gravity chromatography with CHCl3-n-hexane (1:4) giving compound 8 as yellowish crystals (990 mg, 59%); mp 164 °C. 1H NMR (300 MHz, CDCl3): δ = 7.15 (s, 3 H), 7.00 (s, 3 H), 6.86 (s, 6 H), 3.89 (mc, 6 H), 2.35 (s, 18 H). 13C NMR (75 MHz, CDCl3): δ = 141.80 (q), 141.64 (q), 139.10 (q), 138.61 (q), 131.16 (q), 131.00 (q), 130.19 (t), 129.97 (t), 125.97 (t), 125.39 (t), 125.24 (t), 124.65 (t), 56.49 (q), 56.42 (q), 56.27 (q), 55.95 (q), 21.45 (p). MS (EI, 70 eV): m/z (%) = 1038 (4) [M+•], 1001 (14), 1003 (14), 965 (6), 321 (40), 284 (14), 248 (14), 213 (8), 179 (5), 153 (100), 119 (45).

30

1,3,5-Tris[2-(3,5-dimethylphenyl)ethinyl]benzene ( 11).
A solution of 5 (1.57 g, 5.00 mmol) in Et3N (40 mL) was stirred under argon while bis(triphenylphosphane)palla-dium(II) chloride [67 mg, 0.1 mmol (0.5%)], CuI (8.3 mg, 0.13 mmol) and 3,5-dimethylethinylbenzene (10, [29] 2.64 g, 20 mmol) were added. The mixture was stirred at 60 °C for 42 h. The solid components of the mixture were filtered off by suction and extracted with hot n-hexane. The crude product thus obtained was recrystallized from CHCl3-PE (bp 30-40 °C; 1:2) to give compound 11 as a colorless solid (1.43 g, 62%); mp 160 °C. 1H NMR (300 MHz, CDCl3): δ = 7.59 (s, 3 H), 7.16 (s, 6 H), 6.96 (s, 3 H), 2.35 (s, 18 H). 13C NMR (75 MHz, CDCl3): δ = 137.95 (q), 133.86 (t), 130.53 (t), 129.41 (t), 124.19 (q), 122.51 (q), 90.88 (q), 87.31 (q), 21.11 (p). MS (EI, 70 eV): m/z (%) = 462 (100) [M+•], 231 (8), 128 (7).

31

1,3,5-Tris[3′,5′-dimethyl-3,4,5,6-tetrachlorobiphenyl-2-yl]benzene ( 12).
A mixture of tritolane 11 (0.9 g, 1.95 mmol), sulfone 7 (1.52 g, 6.0 mmol) and xylenes (3.5 mL) was heated to 150 °C for 48 h. The product mixture was impregnated on silica gel and then subjected to flash chromatography using silica gel and CHCl3-n-hexane (1:19). The crude product obtained was recrystallized from CH2Cl2-MeOH (1:3) giving compound 12 as yellowish crystals (906 mg, 45%); mp 321 °C. 1H NMR (300 MHz, CDCl3): δ = 6.84 (s, 2 H), 6.80 (s, 1 H), 6.66 (s, 1 H), 6.57 (s, 2 H), 6.48 (s, 2 H), 6.44 (s, 2 H), 6.29 (s, 2 H), 2.18 (s, 6 H), 2.17 (s, 6 H), 2.14 (s, 6 H). 13C NMR (75 MHz, CDCl3): δ = 141.53 (q), 140.92 (q), 140.06 (q), 139.34 (q), 137.77 (q), 137.48 (q), 137.26 (q), 136.98 (q), 132.92 (q), 132.74 (q), 132.56 (q), 132.47 (q), 132.32 (q), 132.23 (q), 132.12 (q), 131.67 (q), 130.92 (t), 130.46 (t), 129.76 (t), 129.43 (t), 127.74 (t), 127.24 (t), 126.48 (t), 21.36 (p), 21.30 (p), 21.25 (p). MS (EI, 70 eV): m/z (%) = 1032 (100) [M+•], 331 (9), 105 (12).

33

Mass spectrometry and NMR spectroscopy revealed unequivocally that the central rings of the three terphenyl units of 8 and 12 were fully reduced to cyclohexane-1,2-diyl spacers. The molecular ions expel up to three C4H6 neutrals (presumably butadiene, 54 u), reflecting the presence of up to three 1,2-diphenylcyclohexane units.

38

Nierle, J.; Kuck, D., to be published.

39

1,3,5-Tris[3′,5′-dimethylbiphenyl-2-yl]benzene (Septiphenyl 13).(A) By PET-Induced Dechlorination of Dodecachloro-septiphenyl 12.
A solution prepared from septiphenyl 12 (1.00 g, 0.96 mmol), anthracene (1.14 g, 6.40 mmol) and a mixture of MeCN (380 mL), DMF (120 mL) and Et3N (380 mL) was irradiated in a falling-film photoreactor (lamp: TQ 718/Z2, 700 W) for 15 h. After the reaction was completed, the solvent was removed under reduced pressure, the residue was redissolved in CHCl3 and the solution obtained was washed four times with H2O (100 mL each). The combined organic layers were dried over Na2SO4 and the solvent was removed. The components of the residue were separated by flash chromatography using silica gel and n-hexane-CHCl3 (4:1). The early-diluting fractions consisted of anthracene (330 mg, 29%), the later-diluting ones contained the product 13 which, after recrystallization from CHCl3-EtOH (1:2) gave a yield of 180 mg (30%); mp 128 °C. 1H NMR (500 MHz, CDCl3): δ = 7.32 (d, 3 J = 7.5 Hz, 3 H), 7.28 (t, 3 J = 7.5 Hz, 3 H), 7.21 (dt, 3 J = 8.8 Hz, 4 J = 1.3 Hz, 3 H), 6.90 (s, 3 H), 6.82 (s, 3 H), 6.74 (s, 6 H), 6.69 (d, 3 J = 7.6 Hz, 3 H), 2.22 (s, 18 H). 13C NMR (125 MHz, CDCl3): δ = 141.78 (q), 140.56 (q), 140.03 (q), 139.77 (q), 137.36 (q), 130.49 (t), 130.40 (t), 129.71 (t), 128.06 (t), 127.79 (t), 127.03 (t), 126.96 (t), 21.34 (p). MS (EI, 70 eV): m/z (%) = 618 (100) [M+•], 309 (7), 193 (15), 178 (7). UV (n-hexane, 1.1·10-5 mol l-1): λ (log ε) = 260 (4.53), 239 (4.71), 218 (4.85) nm. Accurate mass (EI-MS): m/z calcd for C48H42: 618.3287; found: 618.3282.
(B) By PET-Induced Dechlorination of the Nonachloro-septiphenyls 9.
A solution prepared from the mixture of 1,3,5-tris[trichloro-3′,5′-dimethylbiphenyl-2-yl]benzenes 9 (269 mg, 0.29 mmol)), 9,10-dimethylanthracene (398 mg, 1.93 mmol) and a mixture of MeCN (130 mL), DMF (40 mL) and Et3N (130 mL) was irradiated for 6 h in the photoreactor mentioned above for 12. Work-up including flash chromatography (silica gel, n-C6H14-CHCl3, 4:1) yielded septiphenyl 13 (110 mg, 68%) after recrystallization from EtOH- CHCl3 (2:1). The spectroscopic data were found to be identical with those given above.
(C) By Pd(0)-Catalyzed Arylation of Triiodoquater-phenyl 15. A mixture of quaterphenyl 15 (1.34 g, 2.0 mmol), 3,5-dimethylphenylboronic acid(16) [47] (4.06 g, 27.1 mmol, 4.5 equiv), KOH (8.2 g, 146.2 mmol), bis(dibenzylidene-acetone)palladium (117.4 mg, 0.2 mmol) and triphenyl-phosphane (1.15 g, 4.4 mmol) was added nitrobenzene (100 mL) and, under vigorous stirring, H2O (12 mL). The mixture was stirred under a stream of argon for 30 min and then heated to 100 °C for 4.5 d. After cooling to ambient temperature, the mixture was washed with aq KOH (20%). The solvent was removed under reduced pressure and the mixture was subjected to flash chromatography with silica gel and n-hexane-CHCl3 (4:1). The crude product obtained was recrystallized from EtOH-CHCl3 (2:1) giving septiphenyl 13 as colorless crystals (1.2 g, 97%). The physical and spectroscopic properties were found to be identical with those given above. A similar reaction of 15 (2.24 g, 3.3 mmol), 16 (2.95 g, 19.7 mmol, 2 equiv), KOH (13.5 g, 241 mmol), Pd(dba)2 (194.0 mg, 0.4 mmol) and PPh3 (1.9 g, 7.3 mmol) in PhNO2 (165 mL) and H2O (50 mL) gave pure septiphenyl 13 in still excellent isolated yield (1.8 g, 90%).

40

1,3,5-Tris(2-iodophenyl)benzene ( 15).
A solution of 2-iodoacetophenone (14, [42] 3.8 g, 15.5 mmol) in anhyd EtOH (15 mL) was stirred at ambient temperature while SiCl4 (3.7 mL, 31.0 mmol) was added dropwise. After stirring for additional 20 h, the mixture was poured on H2O (30 mL) and the mixture was extracted with CH2Cl2. The combined organic layers were dried over Na2SO4 and the solvent was removed. The crude product was redissolved in CHCl3 (3 mL) and crystallized by addition of EtOH (ca. 9 mL) giving quaterphenyl 15 (1.94 g, 55%) as a yellow solid; mp 169 °C. 1H NMR (250 MHz, CDCl3): δ = 7.96 (dd, 3 J = 7.9 Hz, 4 J = 0.9 Hz, 3 H), 7.41 (mc, 6 H), 7.32 (s, 3 H), 7.02 (dt, 3 J = 8.5 Hz, 4 J = 1.8 Hz, 3 H). 13C NMR (62 MHz, CDCl3): δ = 146.12 (q), 143.53 (q), 139.51 (t), 133.22 (t), 129.29 (t), 128.94 (t), 128.11 (t), 98.61 (q). MS (EI, 70 eV): m/z (%) = 684 (100) [M+•], 558 (4), 430 (11), 302 (56), 150 (24). UV (n-hexane, 10-5 mol l-1): λ (log ε) = 253 (4.73), 250 (4.44), 223 (4.70) nm. Accurate mass (EI-MS): m/z calcd for C24H15I3: 683.8311; found: 683.8308.

48

The corresponding reaction of 1,3,5-tri(2-bromo-phenyl)benzene with 16 under the same conditions proved to be non-productive.

49

Molecular mechanics calculations suggest that the most stable conformers of the septiphenyls 12 and 13 are not C 3-symmetrical; rather, two meta-xylyl groups reside above the plane of the central benzene ring and one below.

50

1,3,5-Tris-[3′,5′-bis-(bromomethyl)biphenyl-2-yl]benzene 17.Procedure A.
A solution of septiphenyl 13 (1.32 g, 2.1 mmol) in CCl4 (25 mL) was heated to reflux while NBS was added in six portions (470.0 mg, 2.6 mmol each) together with benzoyl peroxide (a few mg) at intervals of 60 min. Heating to reflux was continued for a total of 44 h. The mixture was allowed to cool to ambient temperature, the succinimide precipitated was filtered off and the solvent was removed. The crude product obtained in this manner was used without further purification. The yellowish solid (2.3 g, ca. 99%) contained a mixture of differently brominated species. 1H NMR (500 MHz, CDCl3): δ = 7.30 (mc, 14 H), 7.04 (mc, 5 H), 6.77 (mc, 5 H), 4.34 (mc, 12 H). 13C NMR (125 MHz, CDCl3): δ = 143.15 (q), 139.86 (q), 139.76 (q), 138.89 (q), 137.84 (q), 130.65 (t), 130.00 (t), 127.93 (t), 127.47 (t), 127.10 (t). MS (EI, 70 eV): m/z (%) = 1098/1096/1094/1092/1090/1088 (2/9/29/24/18/7) [M+•], 1012 (22), 934 (7), 851 (7), 771 (11), 689 (19), 609 (25), 345 (11), 243 (39), 165 (16), 80 (100).
Procedure B.
A solution of septiphenyl 13 (620 mg, 1.0 mmol) in CCl4 (10 mL) was heated to reflux and irradiated by use of a photo-lamp (500 W), while a solution of bromine (1 M, 7.2 ml, 7.2 mmol) in CCl4 was added dropwise within 30 min. After additional 30 min, work-up furnished a yellowish solid (917.0 mg, 84%), which exhibited similar properties as that described above and was used without further purification.

52

Tribenzospheriphane 2.A. By Reductive Coupling of 1,3,5-Tris[3′,5′-bis(bromomethyl)biphenyl-2-yl]benzene ( 17).
A solution of phenyllithium in cyclohexane-Et2O (70:30, 1.8 M, 13.3 mL, 24.0 mmol) was diluted with Et2O (100 mL) was stirred and heated to reflux in a dilution principle apparatus, while a solution of hexabromoseptiphenyl 17 (1.19 g, 1.10 mmol) in a mixture of anhyd Et2O and THF (1:1, 150 mL) was added dropwise during 8 h. After this period, the mixture was allowed to cool to ambient temperature and hydrolyzed by addition of H2O (5 mL). The solvent was removed by distillation and the residue was redissolved in CHCl3. The solution was washed with H2O, dried over Na2SO4 and the solvent was removed. The residue was subjected to gravity column chromatography using silica gel and n-hexane-CHCl3 (1:1), giving a mixture of the product, 2, and biphenyl. The two components were separated by filtration of their solution in n-hexane through silica gel; biphenyl eluted very fast whereas elution with CHCl3 furnished spheriphane 2 as a colorless solid (35 mg, 6%); mp >360 °C. IR (KBr): 3132, 3028, 2935, 2854, 1739, 1730, 1714, 1702, 1597, 1489, 1442, 1409, 1373, 1239, 1160, 1114, 1044, 982, 883, 823, 760, 702, 675 cm-1. 1H NMR (500 MHz, CDCl3): δ = 7.27 (mc, 6 H), 7.21 (mc, 3 H), 7.12 (mc, 3 H), 6.73 (s, 3 H), 6.64 (s, 3 H), 6.52 (s, 6 H), 2.99 (mc, 12 H). 13C NMR (125 MHz, CDCl3): δ = 142.19 (q), 141.79 (q), 141.26 (q), 139.90 (q), 138.41 (q), 129.38 (t), 128.86 (t), 128.09 (t), 127.19 (t), 126.89 (t), 126.30 (t), 126.16 (t), 33.06 (s). MS (EI, 70 eV): m/z (%) = 612 (100) [M+•], 306 (5). UV (n-hexane, 10-5 mol l-1): λ (log ε) = 261 (4.22), 220 (4.82), 216 (4.85) nm. Accurate mass (EI-MS): m/z calcd for C48H36: 612.2817; found: 612.2835.