Synlett 2007(7): 1051-1054  
DOI: 10.1055/s-2007-977425
LETTER
© Georg Thieme Verlag Stuttgart · New York

Nitration of Fullerene Derivatives under Mild Conditions

Frédéric Oswald, Pilar de la Cruz, Fernando Langa*
Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, 45071 Toledo, Spain
Fax: +34(902) 204130; e-Mail: Fernando.Lpuente@uclm.es;
Further Information

Publication History

Received 20 December 2006
Publication Date:
13 April 2007 (online)

Abstract

A new family of N-(2,4-dinitrophenyl)-2-pyrazolino[60]fullerene derivatives has been synthesized by electrophilic nitration using nitronium triflate. As evidenced by CV and OSWV experiments, these species show enhanced electron-accepting ­properties (up to 90 mV) with respect to C60.

    References and Notes

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13

Compound 2b: A solution of p-nitrophenylhydrazine (1.0 g, 6.5 mmol), 3,5,5-trimethylhexanal (0.82 g, 6.5 mmol) and two drops of AcOH in EtOH (50 mL) was heated under reflux for 2 h. The solid was filtered off and recrystallized in EtOH to give 2b as a red solid (1.47 g, 82%); mp 82.3-82.7 °C. 1H NMR (200 MHz, CDCl3): δ = 8.13 (d, J = 9.2 Hz, 2 H), 7.90 (s, 1 H), 7.19 (t, 1 H), 6.99 (d, J = 9.2 Hz, 2 H), 2.10-2.40 (m, 2 H), 1.85 (m, 1 H), 1.32 (dd, J 1 = 3.4 Hz, J 2 = 14.0 Hz, 1 H), 1.13 (dd, J 1 = 6.2 Hz, J 2 = 14.0 Hz, 1 H), 1.01 (d, J = 6.6 Hz, 3 H), 0.91 (s, 9 H). 13C NMR (50 MHz, CDCl3): δ = 150.3, 145.3, 144.5, 140.4, 139.7, 126.4, 126.3, 112.0, 111.3, 50.8, 50.6, 41.6, 35.7, 31.3, 31.3, 30.1, 28.2, 27.7, 23.0, 22.8. FT-IR (ATR): 3289, 2941, 1617, 1511, 1335, 1266 cm-1. Anal. Calcd for C15H23N3O2: C, 64.95; H, 8.36; N. 15.15. Found: C, 64.43; H, 8.13; N, 15.21.
Compound 3b: To a solution of hydrazone 2b (115 mg, 0.41 mmol) in anhyd CHCl3 (10 mL) was added, under an Ar atmosphere, NBS (148 mg, 0.82 mmol). The mixture was kept under agitation during 2 h at r.t. The solvent was removed and an anhyd toluene (250 mL) solution of C60 (300 mg) and Et3N in excess were then added. The reaction was kept under agitation at r.t. for 1.75 h. The toluene was then evaporated under vacuum. The remaining solid was purified by column chromatography (silica gel; toluene-hexane, 2:1) to give 3b in 41% yield. 1H NMR (200 MHz, CDCl3): δ = 8.30 (d, J = 9.6 Hz, 2 H), 8.16 (d, J = 9.6 Hz, 2 H), 3.15 (dd, J 1 = 5.9 Hz, J 2 = 16.0 Hz, 1 H), 2.99 (dd, J 1 = 8.0 Hz, J 2 = 16.0 Hz, 1 H), 2.53 (m, 1 H), 1.65 (dd, J 1 = 4.2 Hz, J 2 = 14.6 Hz, 1 H), 1.37 (dd, J 1 = 6.6 Hz, J 2 = 14.7 Hz, 1 H), 1.33 (d, J = 6.5 Hz, 3 H), 0.99 (s, 9 H). 13C NMR (50 MHz, CDCl3): δ = 150.47, 149.15, 147.94, 147.39, 146.75, 146.67, 146.56, 146.39, 146.34, 146.16, 145.76, 145.61, 145.53, 145.47, 145.34, 144.89, 144.64, 144.35, 143.74, 143.46, 143.20, 143.11, 142.64, 142.60, 142.50, 142.29, 141.82, 141.22, 141.14, 139.52, 139.44, 137.25, 136.24, 136.13, 129.28, 128.47, 125.76, 125.54, 118.58, 88.84, 84.28, 51.56, 39.37, 31.53, 31.21, 30.50, 29.96, 28.64, 23.34. FT-IR (KBr): 2941, 1597, 1535, 1335, 530 cm-1. MALDI-TOF: m/z calcd for C75H21N3O2: 995.98; found: 995.9.

17

Experimental Procedure: To an anhyd CH2Cl2 solution of the corresponding fullerene derivative 2 (1 equiv) in CH2Cl2, tetramethylammonium nitrate (2 equiv) was added under Ar. The solution was cooled to the desired temperature and triflic anhydride (2 equiv) was added. NO2OTf was formed in situ and the solution was kept at this temperature until the complete disappearance of the starting material (the reaction progression was followed by TLC). The reaction was then quenched by adding a Na2CO3 solution (pH 8). The organic layer was separated, dried and evaporated. The remaining solid was purified by column chromatography affording the desired compounds 1a-d.
Compound 1a: reaction temperature: -5 °C for 4 h. Column chromatography (silica gel; toluene-hexane, 1:2); yield: 90%. 1H NMR (500 MHz, CDCl3): δ = 8.80 (d, J = 2.5 Hz, 1 H), 8.45 (dd, J 1 = 2.5 Hz, J 2 = 9.0 Hz, 1 H), 8.40 (sd, J = 9.0 Hz, 1 H), 2.79 (s, 3 H).13C NMR (125 MHz, CDCl3): δ = 149.36, 147.79, 147.21, 146.38, 146.32, 146.08, 145.96, 145.34, 145.49, 145.29, 145.28, 145.24, 144.41, 144.23, 144.09, 143.97, 143.21, 143.07, 143.04, 142.95, 142.93, 142.84, 142.40, 142.24, 142.18, 142.05, 142.02, 141.06, 139.81, 137.31, 136.55, 127.10, 126.28, 122.22, 88.90, 83.39, 15.03. FT-IR (KBr): 2917, 2357, 1601, 1527, 1331, 526 cm-1. UV-Vis: λ (log ε) = 255.0 (6.1), 320.0 (5.6) nm. MALDI-TOF: m/z calcd for C68H6N4O4: 942.94; found: 942.0.
Compound 1b: reaction temperature: -5 °C for 5 h. Column chromatography (silica gel; toluene-hexane, 1:2); yield: 85%. 1H NMR (500 MHz, CDCl3): δ = 8.78 (d, J = 2.4 Hz, 1 H), 8.44 (dd, J 1 = 2.5 Hz, J 2 = 9.0 Hz, 1 H), 8.40 (sd, J = 9.0 Hz, 1 H), 3.11 (dd, J 1 = 4.6 Hz, J 2 = 16.5 Hz, 1 H), 2.95 (dd, J 1 = 8.8 Hz, J 2 = 16.5 Hz, 1 H), 2.45 (m, 1 H), 1.54 (dd, J 1 = 4.5 Hz, J 2 = 14.0 Hz, 1 H), 1.33 (dd, J 1 = 6.2 Hz, J 2 = 14.0 Hz, 1 H), 1.27 (d, J = 6.6 Hz, 3 H), 0.99 (s, 9 H). 13C NMR (125 MHz, CDCl3): δ = 151.63, 147.77, 147.20, 146.37, 146.36, 146.31, 146.31, 146.07, 146.06, 146.05, 145.96, 145.95, 145.55, 145.53, 145.51, 145.46, 145.43, 145.42, 145.32, 145.29, 145.28, 145.26, 145.25, 144.40, 144.29, 144.24, 144.10, 144.09, 144.06, 143.21, 143.01, 142.97, 142.85, 142.83, 142.75, 142.42, 142.40, 142.26, 142.24, 142.19, 142.16, 142.12, 142.10, 142.01, 142.00, 140.95, 140.90, 139.84, 139.79, 137.31, 136.45, 136.26, 126.99, 126.00, 122.19, 88.84, 83.84, 51.39, 39.25, 31.26, 30.04, 28.07, 22.98. FT-IR (KBr): 2941, 2337, 1597, 1540, 1335, 526 cm-1. UV-Vis: λ (log ε) = 255.0 (6.2), 320.0 (5.7) nm. MALDI-TOF: m/z calcd for C75H20N4O4: 1040.98; found: 1040.1.
Compound 1c: reaction temperature: r.t. for 2 h. Column chromatography (silica gel; toluene-hexane, 2:1); yield: 65%. 1H NMR (500 MHz, CDCl3): δ = 8.87 (d, J = 2.5 Hz, 1 H), 8.52 (dd, J 1 = 2.5 Hz, J 2 = 9.0 Hz, 1 H), 8.49 (sd, J = 9.0 Hz, 1 H), 8.38 (d, J = 9.0 Hz, 2 H), 8.36 (d, J = 9.0 Hz, 2 H). 13C NMR (125 MHz, CDCl3): δ = 148.61, 147.79, 147.32, 147.13, 146.46, 146.42, 146.14, 146.08, 145.60, 145.56, 145.38, 145.33, 145.16, 144.69, 144.33, 144.16, 144.15, 144.08, 143.95, 143.28, 143.07, 142.99, 142.94, 142.49, 142.32, 142.26, 142.08, 141.99, 141.95, 140.64, 140.12, 137.38, 137.21, 136.90, 129.73, 127.32, 127.13, 124.24, 122.20, 91.39, 81.42. FT-IR (KBr): 2357, 1597, 1535, 1335, 526. UV-Vis: λ (log ε) = 245.5 (6.3), 321.5 (5.9) nm. MALDI-TOF: m/z calcd for C73H7N5O6: 1049.87; found: 1050.2.
Compound 1d: reaction temperature: r.t. for 3 h. Column chromatography (silica gel; toluene-hexane, 1:2); yield: 47%. 1H NMR (500 MHz, CDCl3): δ = 8.88 (d, J = 2.5 Hz, 1 H), 8.67 (br s, 2 H), 8.53 (dd, J 1 = 2.5 Hz, J 2 = 9.0 Hz, 1 H), 8.48 (sd, J = 9.0 Hz, 1 H), 8.00 (br s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 148.07, 147.58, 146.72, 146.68, 146.40, 146.35, 145.97, 145.79, 145.66, 145.59, 145.12, 144.59, 144.41, 144.16, 144.13, 143.54, 143.33, 143.25, 143.18, 142.73, 142.58, 142.53, 142.31, 142.25, 140.89, 140.40, 137.64, 137.29, 133.46, 132.90, 132.63, 128.93, 127.57, 124.26, 123.99, 122.43, 122.11, 91.81, 81.44. FT-IR (KBr): 2921, 2332, 1597, 1531, 1331, 1274, 1135, 526 cm-1. UV-Vis: λ (log ε) = 254.5 (6.1), 319.0 (5.7) nm. MALDI-TOF: m/z calcd for C75H6F6N4O4: 1140.86; found: 1141.2.