PDF herunterladen
Synlett 2010(12): 1811-1814  
DOI: 10.1055/s-0030-1258112
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A General Method for the Synthesis of 2,2-[60]Fullerenoalkanals: The Reaction of [60]Fullerene with 2-Bromoenol Silyl Ethers

Hiroshi Ito, Yusuke Kishi, Yohei Nishikawa, Tomonori Tada, Yasuhiro Ishida, Kazuhiko Saigo*,
Department of Chemistry and Biotechnology, Graduated School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
Fax: +81(887)572520; e-Mail: saigo.kazuhiko@kochi-tech.ac.jp;
Weitere Informationen

Publikationsverlauf

Received 22 February 2010
Publikationsdatum:
30. Juni 2010 (online)

   Lizenzen und Reprints Alle Artikel dieser Rubrik
Preview

Abstract

Five kinds of 2,2-[60]fullerenoalkanals were synthesized by the fluoride ion-mediated reaction of [60]fullerene with 2-bromoenol silyl ethers, which were easily prepared by 2-bromination of the corresponding enol silyl ethers. The reactivity differed significantly depending on the stability of the 2-bromoenol silyl ethers. High yield and selectivity were achieved for the reaction of 2-bromoenol trimethylsilyl ethers under mild conditions (KF/18-crown-6-ether). The reaction of stable 2-bromoenol tert-butyldimethylsilyl ethers, on the other hand, required the use of more reactive tetra­butylammonium fluoride as a fluoride ion source.

Key words

fullerenes - cyclopropanation - silyl enol ethers - aldehydes - bromine

1

Present address: School of Environmental Science and Technology, Koch University of Technology, Miyanokuchi, Tosayamada-cho, Kami-shi, Kochi 782-8502, Japan

10

General procedure for the synthesis 2-bromoenol trimethyl-silyl ethers 1a-e. Bromine (1.9 mL, 37 mmol) and triethyl-amine (7.7 mL, 55 mmol) were successively added dropwise to a solution of 1-trimethylsiloxy-1-alkene (37 mmol) in CH2Cl2 (28 mL) at -78 ˚C, and the mixture was stirred at r.t. for 3 h. Then, hexane (30 mL) was added to the mixture, and the resultant white precipitates were filtered off. The filtrate was washed with saturated NaHCO3 (100 mL), H2O (100 mL) and brine (100 mL), successively. The organic layer was dried over sodium sulfonate and filtered, and the solvent was removed under reduced pressure. The residue was purified by distillation under reduced pressure to afford the corresponding 2-BrESE (E/Z mixture) as a clear liquid.
2-Bromo-1-trimethylsiloxy-1-butene (1a): Ratio major/minor = 89:11 (determined by ¹H NMR). Bp 63-73 ˚C/15 mmHg. IR (neat): 2969, 2937, 2917, 2876, 2804, 1656, 1457, 1336, 1317, 1255, 1191, 1129, 1106, 1068, 1041, 942, 924, 867, 846, 754 cm-¹. ¹H NMR (300 MHz, CDCl3):
δ (major) = 6.47 (t, J = 0.6 Hz, 1 H), 2.5-2.4 (m, 2 H), 1.1-1.0 (m, 3 H), 0.3-0.2 (m, 9 H); δ (minor) = 6.15 (t, J = 0.6 Hz, 1 H), 2.5-2.4 (m, 2 H), 1.1-1.0 (m, 3 H), 0.3-0.2 (m, 9 H). ¹³C NMR (75 MHz, CDCl3): δ = 135.28, 111.51, 29.24, 14.38, -0.02. MS (EI): m/z (%) = 222 (100), 224 (100). 2-Bromo-1-trimethylsiloxy-1-dodecene (1b): Ratio major/minor = 92:8 (determined by ¹H NMR). Bp ˜124 ˚C/1 mmHg. IR (neat): 2956, 2925, 2854, 1730, 1657, 1465, 1254, 1195, 870, 848, 756 cm-¹. ¹H NMR (300 MHz, CDCl3): δ (major) = 6.44 (s, 1 H), 2.43 (t, J = 6.9 Hz, 2 H), 1.89 (br, 2 H), 1.26 (br, 16 H), 0.3-0.2 (m, 9 H); δ (minor) = 6.50 (s, 1 H), 2.43 (t, J = 6.9 Hz, 2 H), 1.89 (br, 2 H), 1.26 (br, 16 H), 0.3-0.2 (m, 9 H). ¹³C NMR (75 MHz, CDCl3):
δ = 135.84, 35.49, 32.25, 29.94, 29.88, 29.81, 29.67, 29.63, 28.68, 28.56, 23.03, 14.47, -0.02. MS (EI): m/z (%) = 334 (100), 336 (100).
2-Bromo-3-phenyl-1-trimethylsiloxy-1-propene (1c): Ratio major/minor = 89:11 (determined by ¹H NMR). Bp ˜112 ˚C/1.5 mmHg. IR (neat): 3029, 2958, 2900, 1731, 1659, 1603, 1495, 1454, 1419, 1333, 1254, 1210, 1172, 868, 849, 748, 698 cm-¹. ¹H NMR (300 MHz, CDCl3): δ (major) = 7.3-7.2 (m, 5 H), 6.59 (t, J = 0.9 Hz, 1 H), 3.64 (s, 2 H), 0.3-0.2 (m, 9 H); δ (minor) = 7.3-7.2 (m, 5 H), 6.64 (t, J = 0.9 Hz, 1 H), 3.80 (s, 2 H), 0.3-0.2 (m, 9 H). ¹³C NMR (75 Hz, CDCl3): δ = 138.31, 137.19, 128.62, 128.36, 126.63, 107.44, 41.49, -0.34. MS (EI): m/z (%) = 284 (100), 226 (100).
2-Bromo-2-phenyl-1-(trimethylsiloxy)ethene (1d): Ratio major/minor = 90:10 (determined by ¹H NMR). Bp ˜78 ˚C/1 mmHg. IR (neat): 3060, 3031, 2958, 1727, 1636, 1491, 1443, 1255, 1167, 935, 758, 694 cm-¹. ¹H NMR (300 MHz, CDCl3): δ (major) = 7.5-7.2 (m, 4 H), 6.96 (s, 1 H), 0.30 (s, 9 H); δ (minor) = 6.50, 7.5-7.2 (m, 4 H), 6.90 (s, 1 H), 0.24 (s, 9 H). ¹³C NMR (75 MHz, CDCl3): δ = 138.50, 129.25, 129.04, 128.32, 127.62, 127.37, -0.27. MS (EI): m/z (%) = 270 (100), 272 (100).
2-Bromo-1-trimethylsiloxyethene (1e): Bp ˜74 ˚C/52 mmHg. IR (neat): 3106, 3010, 2960, 2901, 1636, 1329, 1255, 1241, 1166, 1094, 878, 849, 757, 708, 655, 605 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 6.73 (d, J = 3.9 Hz, 1 H), 5.24 (d, J = 3.9 Hz, 1 H), 0.24 (s, 9 H). ¹³C NMR (75 MHz, CDCl3): δ = 141.41, 87.37, -0.43. MS (EI): m/z (%) = 194 (100), 196 (100)

11

The enol tert-butyldimethylsilyl ethers 4c′ and 4d′ were synthesized according to a method in the literature,¹6 and was purified by silica gel column chromatography.
1- tert -Butyldimethylsilyloxy-3-phenylpropene (4c′): IR(neat): 3029, 2955, 2929, 2858, 1655, 1255, 1115, 838 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 7.4-7.1 (m, 5 H), 6.30 (dt, J = 5.7, 1.5 Hz, 1 H), 4.67 (dt, J = 5.7, 7.2 Hz, 1 H), 3.45 (dd, J = 1.5, 7.2 Hz, 2 H), 0.94 (s, 9 H), 0.15 (s, 6 H). ¹³C NMR (75 MHz, CDCl3): δ = 141.97, 139.10, 128.32, 128.25, 125.58, 109.08, 29.92, 25.63, 18.26, -5.33. MS (EI): m/z = 248. 1- tert -Butyldimethylsilyloxy-2-phenylethene (4d′): Ratio major/minor = 52:48 (determined by ¹H NMR). IR (neat): 3030, 2955, 2930, 2885, 2858, 1645, 1471, 889, 838, 783, 692 cm-¹. ¹H NMR (300 MHz, CDCl3): δ (major) = 7.3-7.1 (m, 5 H), 7.00 (d, J = 12.3 Hz, 1 H), 6.03 (d, J = 12.3 Hz, 1 H), 0.96 (s, 9 H), 0.21 (s, 6 H); δ (minor) = 7.7-7.6 (m, 2 H), 7.3-7.1 (m, 3 H), 6.42 (d, J = 6.6 Hz, 1 H), 5.30 (d, J = 6.6 Hz, 1 H), 0.98 (s, 9 H), 0.22 (s, 6 H). ¹³C NMR (75 MHz, CDCl3): δ = 142.23, 140.51, 136.47, 136.19, 128.49, 128.18, 128.07, 125.73, 125.63, 125.12, 112.82, 108.84, 25.68, 25.62, 18.32, 18.21, -5.18, -5.38. MS (EI): m/z = 234

12

The 2-bromoenol tert-butyldimethylsilyl ethers 1c′ and 1d′ were synthesized in a similar manner to that used for the preparation of the 2-boromoenol trimethylsilyl ethers. The crude products were purified by column chromatography [SiO2; hexane-CH2Cl2, 10:0 to 8:2 (v/v)].
2-Bromo-1- tert -butyldimethylsilyloxy-3-phenylpropene (1c′): IR(neat): 3029, 2954, 2929, 2858, 1659, 1254, 1211, 1171, 838 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 7.4-7.2 (m, 5 H), 6.61 (s, 1 H), 3.64 (s, 2 H), 0.96 (s, 1 H), 0.19 (s, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = 138.38, 137.72, 128.63, 128.34, 126.61, 106.92, 441.42, 25.51, 18.27, -5.17. MS (EI): m/z (%) = 326 (100), 328 (100). 2-Bromo-1- tert -butyldimethylsilyloxy-2-phenylethene (1d′): Ratio major/minor = 65:35 (determined by ¹H NMR). Major isomer: IR (neat): 2954, 2929, 2858, 1635, 1261, 1168, 828 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 7.5-7.4 (m, 2 H), 7.4-7.2 (m, 3 H), 6.98 (s, 1 H), 0.99 (s, 1 H), 0.24 (s, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = 138.91, 137.11, 128.31, 127.53, 127.32, 106.74, 25.50, 18.26, -5.11. MS (EI): m/z (%) = 312(100), 314(100). Minor isomer: IR(neat): 2955, 2929, 2858, 1617, 1259, 1228, 1136, 827 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 7.8-7.7 (m, 2 H), 7.4-7.1 (m, 3 H), 6.91 (s, 1 H), 0.91 (s, 9 H), 0.19 (s, 6 H). ¹³C NMR (75 MHz, CDCl3): δ = 140.24, 135.50, 128.99, 127.74, 127.31, 106.93, 25.44, 18.07, -5.30. MS (EI): m/z (%) = 312 (100), 314 (100)

13

General procedure for the synthesis of 2,2-[60]fullereno-alkanals. The KF/18-crown-6 method: KF (5.8 mg, 0.10 mmol) and an 18-crown-6 solution in toluene (0.10 M, 0.20 mL, 0.020 mmol) were added to a solution of [60]fullerene (72 mg, 0.10 mmol) and 2-BrESE (0.10 mmol) in toluene (72 mL). After the mixture was stirred at r.t. for 72 h, the solvent was evaporated to dryness. The residue was purified by preparative thin layer chromatography (SiO2, CS2) to afford the corresponding 2,2-[60]fullerenoalkanal as a dark-brown solid.
The TBAF method: A TBAF solution (1 M in THF, 0.30 mL, 0.30 mmol) was added to a solution of [60]fullerene (72 mg, 0.10 mmol) and 2-BrESE (0.10 mmol) in toluene (72 mL). After the mixture was stirred at r.t. for 3 h, the solvent was evaporated to dryness. The residue was purified by column chromatography [SiO2; hexane-toluene, 9:1 to 2:1 (v/v)] to afford the corresponding 2,2-[60]fullerenoalkanal as a dark-brown solid.
2,2-[60]Fullerenobutanal (2a): See ref. 5.
2,2-[60]Fullerenododecanal (2b): IR (KBr): 2921, 2849, 1719, 1461, 1428, 1186, 578, 555, 526 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 10.57 (s, 1 H), 2.79 (t, J = 8.1 Hz, 2 H), 2.02-1.85 (m, 2 H), 1.66-1.18 (m, 14 H), 0.89 (t, J = 6.6 Hz, 3 H). ¹³C NMR [125 MHz, CDCl3/CS2, 1:1 (v/v)]: δ = 194.24, 146.84, 145.79, 145.26, 145.25, 145.23, 145.16, 145.13, 144.97, 144.70, 144.64, 144.62, 144.60, 144.40, 143.76, 143.69, 143.19, 143.08, 143.01, 142.94, 142.92, 142.91, 142.05, 141.98, 141.97, 141.57, 141.10, 141.04, 137.96, 137.83, 75.17, 50.23, 31.99, 30.05, 29.71, 29.69, 29.55, 29.46, 27.70, 25.87, 22.84, 14.23. MS (MALDI-TOF): m/z [M] ˙ + calcd for C72H22O: 902.17; found: 902.11.
2,2-[60]Fullereno-3-phenylpropanal (2c): IR (KBr): 2922, 2850, 1718, 1494, 1427, 1260, 1186, 1073, 1030, 732, 706, 576, 555, 526 cm-¹. ¹H NMR (300 MHz, CDCl3): δ = 10.55 (s, 1 H), 7.58 (d, J = 7.4 Hz, 2 H), 7.38 (dd, J = 7.4, 7.4 Hz, 2 H), 7.30 (d, J = 7.4 Hz, 1 H), 4.23 (s, 2 H). ¹³C NMR [125 MHz, CDCl3/CS2, 1:1 (v/v)]: δ = 193.83, 146.85, 145.61, 145.38, 145.35, 145.28, 145.27, 144.98, 144.82, 144.81, 144.80, 144.78, 144.76, 144.58, 143.88, 143.78, 143.20, 143.18, 143.06, 143.01, 142.17, 142.10, 142.07, 141.62, 141.24, 138.15, 138.12, 136.77, 129.40, 128.95, 127.25, 74.98, 50.15, 31.56; three peaks are overlapped. MS (MALDI-TOF): m/z [M] ˙ + calcd for C69H8O: 852.06; found: 851.80.
2,2-[60]Fullereno-2-phenylethanal (2d): See ref. 7.
2,2-[60]Fullerenoethanal (2e): See ref. 7.

14

[60]Fullerene derivatives having two or more alkanal moieties were obtained as by-products.

15

Br2 (0.40 M in CH2Cl2, 1.25 mL, 0.50 mmol) and Et3N (1.5 M in CH2Cl2, 0.50 mL, 0.75 mmol) were successively added dropwise to a solution of 1-trimethylsilyloxy-1-butene (4a; 72 mg, 0.50 mmol) in CH2Cl2 (7.5 mL) at -78 ˚C, and the mixture was stirred at r.t. for 3 h. A solution of [60]fullerene (0.10 mM in toluene, 72 mL), KF (29 mg, 0.50 mmol), and 18-crown-6 (26 mg, 0.10 mmol) were successively added to the mixture. After the mixture was stirred at r.t. for 42 h, the solvent was evaporated to dryness. The residue was purified by preparative thin layer chromatography (SiO2, CS2) to afford 2,2-[60]fullerenobutanal 1a (36 mg, 0.46 mmol, 46% yield) as a dark-brown solid