Efficient Synthesis of Arylated Carbazole from Cyclopentadienyliron

Article pubs.acs.org/IECR

Efficient Synthesis of Arylated Carbazole from Cyclopentadienyliron Complexes Yu Chen,‡ Dandan Han,‡ Tao Wang,*,†,‡ and Xiuyan Li§ †

State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, 100029, People’s Republic of China ‡ College of Science, Beijing University of Chemical Technology, Beijing, 100029, People’s Republic of China § College of Materials Science and Engineering, Beijing Institute of Fashion Technology, Beijing, 100029, People’s Republic of China S Supporting Information *

ABSTRACT: Arylated carbazoles are valuable intermediates in the preparation of organic functional materials. The present work addresses an improved process for the preparation of arylated carbazoles. This process involves a nucleophilic substitution between the cyclopentadienyliron complexes of chloroarenes and carbazole or hydroxyl carbazole, followed by photolysis of cyclopentadienyliron complexes of arylated carbazoles (Fc-carbazole). The described process combines two steps in good yields and is cost-effective, and thus, it is a practical route of preparation of arylated carbazoles. The purification strategy of arylated carbazoles was subjected to crystallization instead of column chromatography, which is very good for their industrial applications. The arylated carbazoles products were determined by Fourier transform infrared (FT-IR), liquid chromatography mass spectroscopy (LC-MS), and NMR.

1. INTRODUCTION Carbazoles are a distinguished class of aromatic heterocyclic compounds. Carbazole derivatives are known as alkaloids from plants, and many of them show antioxidative and biological properties, such as antitumor, psychotropic, anti-inflammatory, antihistaminic, and antibiotic activities.1−7 Carbazole derivatives are widely used as organic materials due to their photorefractive, photoconductive, hole-transporting, and light-emitting properties.8−11 Some polycarbazole derivatives have been widely used in polymer, solar cells, and organic light-emitting diodes as green, red, and white emitters.12−14 Carbazolecontaining ligands are effective anion receptors.15,16 Some benzocarbazoles have been utilized as molecular platforms for luminescent, hole-transporting, and host materials in organic light-emitting devices.17,18 The molecular and optical properties of carbazoles can be engineered by structural modifications on the C−2, −3, −6, −7, and −9 positions.19 Arylated carbazoles upon which a phenyl or a naphthyl group is attached have excellent thermal stability and good electrooptical properties.20 Therefore, extensive studies have been carried out to develop a better synthetic method for these types of compounds. Transition metal-catalyzed arylation of carbazole with aryl halides is one of the most efficient and powerful methods for the synthesis of N-arylazole derivatives.21−25 However, from an ecological perspective, the current methods present several limitations because the transformations often use expensive transition metal catalysts, such as palladium, rhodium, nickel, and cobalt complexes. Buchwald and his cowokers26−28 initiated the use of inexpensive copper catalysts bearing various ligands as an efficient method for the N-arylation of nitrogen-containing heterocycles with aryl halides. However, the ligands are complicated and difficult to synthesize. Thus, screening out inexpensive and environmental © 2013 American Chemical Society

methods for the arylation reaction of carbazole remains a great challenge. Nucleophilic substitution of arene complexes to a metal moiety with a variety of different nucleophiles have been reported by Abd-El-Aziz and other researchers.29−36 These metal moieties include tricarbonylchromium, tricarbonylmanganese, and cyclopentadienyliron. Due to the reactivity and relatively simple synthetic methods associated with the cationic cyclopentadienyliron complexes of arene, a large number of functionalized aromatic and biologically active compounds have been prepared using this methodology.34−47 Many arylsubstituted compounds have been synthesized by the nucleophilic substitution of organo-iron complexes followed by photochemical liberation of free arenes.41−47 In this study, carbazole (1) and 4-hydroxyl carbazole (2) were used as raw materials for nucleophilic substitution with cyclopentadienyl chlorobenzene iron hexafluorophosphate and cyclopentadienyl 2, 4-dichlorobenzene iron hexafluorophosphate, respectively. Four substituted arylated carbazole derivatives were obtained from the rapid and efficient photolysis of cationic cyclopentadienyliron complexes of arylated carbazole (Fc-carbazole) with high yields. Based on the 1H NMR spectra, the demetalation process of Fc-carbazole and demetalation activities among different Fc-carbazoles were demonstrated. Received: Revised: Accepted: Published: 3646

January 7, 2013 February 2, 2013 February 7, 2013 February 26, 2013 dx.doi.org/10.1021/ie4000773 | Ind. Eng. Chem. Res. 2013, 52, 3646−3652

Industrial & Engineering Chemistry Research

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2. EXPERIMENTAL SECTION 2.1. Materials and Instruments. Anhydrous aluminum chloride, aluminum powder, ferrocene, carbazole, hydroxyl carbazole, and potassium hexafluorophosphate are commercially available and were used without further purification. All the solvents in this experiment were of reagent-grade quality and were freshly distilled before use. (η6-Chlorobenzene) (η5cyclopentadienyl) iron hexafluorophosphate (3) and (η6Dichlorobenzene) (η5-cyclopentadienyl) iron hexafluorophosphate (4) were prepared through the ligand exchange reactions according to the reference procedures.37 1 H NMR and 13C NMR spectra were recorded at 400 MHz on a Bruker AV400 NMR spectrometer. MS spectra were obtained on a Waters Micromass CQ Detector. Fourier transform infrared (FT-IR) spectra were recorded on a Nicolet 5700 instrument (Thermo Electron Corporation, Waltham, MA). The melting points of the compounds were determined using an XT-4 microscopic melting point apparatus. 2.2. Synthesis of Cationic Cyclopentadienyliron Complexes. 2.2.1. Synthesis of (η6-(N-phenyl carbazole) (η5-cyclopentadienyl) Iron Hexafluorophosphate (5). The compounds 3 (3.78 g, 10.0 mmol), 1 (2.09 g, 12.5 mmol), and K2CO3 (2.76 g, 20.0 mmol) were stirred in 30 mL of N,Ndimethylformamide (DMF) in a 100 mL round-bottom flask under a nitrogen atmosphere at 60 °C for 6 h. Reactions were monitored by thin layer chromatography (TLC) using 0.25 mm aluminum-backed silica gel plates. After 3 was reacted thoroughly, the reaction mixture was transferred into a 15% (v/v) HCl solution, and a granular precipitate was formed. The obtained filtrate was washed with acetone, resulting in dissolution of the product. This solution was then concentrated by evaporating acetone and treated with sufficient KPF6 in water to allow the complete precipitation of 5 as a granular solid. The solid was recrystallized from DMF/methyl tertiary butyl ether (1:5). The desired cationic cyclopentadienyliron complex precipitated as an orange granular solid, and the product was recovered by filtration. The resulting products (fine orange powders) weighed 4.83 g with 95% yield. Mp = 198−199 °C. 1H NMR (400 MHz, DMSO) δppm: 8.33 (d, J = 7.7 Hz, 2H, carbazole-ArH), 8.08 (d, J = 8.4 Hz, 2H, carbazole-ArH), 7.62 (t, J = 7.5 Hz, 2H, carbazole-ArH), 7.46 (t, J = 7.4 Hz, 2H, carbazole-ArH), 7.08 (d, J = 6.5 Hz, 2H, complexed ArH), 6.68 (t, J = 6.3 Hz, 2H, complexed ArH), 6.51 (t, J = 6.1 Hz, 1H, complexed ArH), 5.27 (s, 5H, Cp). 13C NMR (101 MHz, DMSO) δppm: 139(2C), 127 (2C), 124 (2C), 122 (2C), 121 (2C), 111 (2C), 110(1C), 88(2C), 87(2C), 82 (1C), 77 (5C). FT-IR ν (cm−1): 3110 (C−H, aromatic), 1529, 1447, 1421 (CC), 1216 (C−N), 822 (−PF6−). ESI-MS m/z: 365 (cation+). 2.2.2. Synthesis of (η6-4-Phenoxy-9H-carbazole) (η5-Cyclopentadienyl) Iron Hexafluorophosphate (6). The compounds 3 (3.78 g, 10.0 mmol), 2 (1.83 g, 10 mmol), and K2CO3 (1.38 g, 10.0 mmol) were stirred in 30 mL of N, N-dimethylformamide (DMF) in a 100 mL round-bottom flask under a nitrogen atmosphere at 20 °C for 8 h. The monitoring method for the reaction and the purification process of the products are similar to the synthesis of 5. The fine yellow powder was obtained and weighed 4.79 g with 91% yield. Mp = 215−216 °C. 1H NMR (400 MHz, DMSO) δppm: 11.72 (s, 1H, N−H), 7.71 (d, J = 7.9 Hz, 1H, carbazole-ArH), 7.62 − 7.48 (m, 3H, carbazole-ArH), 7.41 (t, J = 7.6 Hz, 1H, carbazole-ArH), 7.16 (d, J = 6.6 Hz, 1H, carbazole-ArH), 7.10

(t, J = 7.5 Hz, 1H, carbazole-ArH), 6.42 (d, J = 6.5 Hz, 2H, complexed ArH), 6.35 (t, J = 6.2 Hz, 2H, complexed), 6.19 (t, J = 5.8 Hz, 1H, complexed), 5.18 (s, 5H, Cp). 13C NMR (101 MHz, DMSO) δppm: 147 (1C), 142 (1C), 139 (1C), 132 (1C), 126 (1C), 126 (1C), 122 (1C), 119 (1C), 119 (1C), 114 (1C), 111 (1C), 110 (1C), 109 (1C), 87 (2C), 85 (2C), 77 (5C), 76 (1C). FT-IR ν (cm−1): 3451 (N−H), 3087 (C−H, aromatic), 1618, 1525, 1456(CC), 1252 (C−N), 827 (−PF6−). ESI-MS m/z: (cation+) 381. 2.2.3. Synthesis of (η6-1,4-Bis((9H-carbazol-4-yl)oxy)benzene) (η5-Cyclopentadienyl) Iron Hexafluorophosphate (7). The compounds 4 (2.07 g, 5.0 mmol), 2 (1.83 g, 10 mmol), and K2CO3 (1.38 g, 10 mmol) were stirred in 30 mL of DMF in a 100 mL round-bottom flask under a nitrogen atmosphere at 20 °C for 6 h. The monitoring method for the reaction and the purification process of the products are similar to the synthesis of 5. The fine yellow powder was obtained and weighed 3.07 g with 87% yield. Mp = 185−186 °C. 1H NMR (400 MHz, acetone) δppm: 10.77 (s, 2H, N−H), 7.83 (d, J = 7.7 Hz, 2H, carbazole-ArH), 7.57 (dd, J = 22.4, 8.8 Hz, 6H, carbazole-ArH), 7.45 (t, J = 7.4 Hz, 2H, carbazole-ArH), 7.16 (t, J = 6.7 Hz, 4H, carbazoleArH), 6.55 (s, 4H, complexed ArH), 5.41 (s, 5H, Cp). 13C NMR (101 MHz, acetone) δppm: 149 (2C), 143 (2C), 140 (2C), 132 (2C), 128 (2C), 127 (2C), 123 (2C), 121 (2C), 120 (2C), 115 (2C), 112 (2C), 111 (2C), 110 (2C), 79 (2C), 76 (2C), 66 (5C). FT-IR: ν (cm−1):3438 (N−H), 3086 (C−H, aromatic), 1611, 1470, 1455 (CC), 1219(C−N), 830 (-PF6−). ESI-MS m/z: 562 (cation+). 2.2.4. Synthesis of (η6-1,4-Di(9H-carbazol-9-yl) Benzene) (η5-Cyclopentadienyl) Iron Hexafluorophosphate (8). The compounds 4 (2.07 g, 5.0 mmol), 1 (2.09 g, 12.5 mmol), and K2CO3 (2.76 g, 20.0 mmol) were stirred in 30 mL of N, Ndimethylformamide (DMF) in a 100 mL round-bottom flask under a nitrogen atmosphere at 60 °C for 4 h. The monitoring method for the reaction and the purification process of the products are similar to the synthesis of 5. The fine yellow powder was obtained and weighed 3.04 g with 90% yield. Mp = 204−205 °C. 1H NMR (400 MHz, DMSO) δppm: 8.36 (d, J = 6.5 Hz, 8H, carbazole-ArH), 7.70 (t, J = 7.4 Hz, 4H, carbazole-ArH), 7.51 (t, J = 7.2 Hz, 4H, carbazole-ArH), 7.38 (s, 4H, complexed ArH), 5.36 (s, 5H, Cp). 13C NMR (101 MHz, DMSO) δppm: 139 (4C), 128 (4C), 125 (4C), 123 (4C), 121 (4C), 112 (4C), 109 (4C), 81 (2C), 78 (5C). FT-IR ν (cm−1): 3063 (C−H, aromatic), 1502, 1488, 1434 (C C), 1330 (C−N), 827 (−PF6−). ESI-MS m/z: (cation+) 530. 2.3. Demetalations. Experiments were carried out in a Pyrex beaker with a working volume of 100 mL. As shown in Figure 1, the reaction beaker was placed in a dark apparatus equipped with a 75 W halogen lamp (λmax > 370 nm). The distance between the solution surface and the lamps that were parallel to the photoreactor axis was 0.05 m. The light intensity was recorded by a UV light radiometer (Photoelectric Instrument Factory, Beijing Normal University, China). All experiments were conducted in a simple and feasible aqueous− organic biphase system. Each of the cationic cyclopentadienyliron complexes was dissolved in 50 mL of dichloromethane (CH2Cl2) and irradiated at room temperature. (I = 40 mW/ cm2). Addition of 10 mL of distilled water into the reaction beaker efficiently prevented the volatilization of the solvent. Reactions were monitored by TLC every 10 min until the fluorescence spot of cationic cyclopentadienyliron complexes disappeared. The solvent was washed by water three times, and 3647

dx.doi.org/10.1021/ie4000773 | Ind. Eng. Chem. Res. 2013, 52, 3646−3652


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2.3.4. Synthesis of 1,4-Di(9H-carbazol-9-yl) Benzene (12). A white solid (87%), the product was crystallized from acetone/petroleum ether (10:1 v/v). Literature Mp of 12 is 319−321 °C.49 1H NMR (400 MHz, CDCl3) δppm: 8.20 (d, J = 7.7 Hz, 4H, carbazole-ArH), 7.83 (s, 4H, phenyl ArH), 7.58 (d, J = 8.2 Hz, 4H, carbazole-ArH), 7.49 (t, J = 7.1 Hz, 4H, carbazole-ArH), 7.35 (t, J = 7.4 Hz, 4H, carbazole-ArH). 13 CNMR (101 MHz, CDCl3) δppm: 141 (4C), 137 (2C), 128 (4C), 126 (4C), 124 (4C), 120 (8C), 110 (4C). FT-IR ν (cm−1): 3054 (C−H, aromatic), 1595, 1515, 1447 (C C), 1228 (C−N). ESI-MS m/z: 409 (cation+).

3. RESULT AND DISCUSSION 3.1. Nucleophilic Substitution. Chloroarene iron complexes react with carbazole (1) and 4-hydroxyl carbazole (2) under very mild conditions (Scheme 1).

Figure 1. Schematic of the photoreactor for the photolysis of cationic cyclopentadienyliron complexes.

Scheme 1. Synthesis and Photolysis of Fc-carbazoles the organic phase was concentrated using rotary evaporation. The residue was crystallized from acetone/petroleum ether at a certain proportion. The expected liberated arenes were recovered by filtration. The corresponding yields and spectral data for these obtained arenes are presented below. 2.3.1. Synthesis of N-Phenyl Carbazole (9). A white solid (79%), the product was crystallized from acetone/petroleum ether (1:10 v/v). Literature Mp of 9 is 89−90 °C.48 1H NMR (400 MHz, DMSO) δppm: 8.25 (d, J = 7.7 Hz, 2H, carbazoleArH), 7.68 (t, J = 7.7 Hz, 2H, carbazole-ArH), 7.61 (d, J = 7.5 Hz, 2H, carbazole-ArH), 7.54 (t, J = 7.3 Hz, 1H, phenyl ArH), 7.48 − 7.40 (t, 2H, phenyl ArH), 7.38 (d, J = 8.0 Hz, 2H, phenyl-ArH), 7.30 (t, J = 7.3 Hz, 2H, carbazole-ArH). 13C NMR (101 MHz, DMSO) δppm: 140 (2C), 137 (1C), 130 (2C), 128 (2C), 127 (2C), 126 (2C), 128 (2C), 120 (2C), 120 (2C), 120(1C). FT-IR ν (cm−1): 3061 (C−H, aromatic), 1596, 1499, 1450 (CC), 1233 (C−N). ESI-MS m/z: 245(cation+) . 2.3.2. Synthesis of 4-Phenoxy-9H-carbazole (10). A pale yellow solid (78%), the product was crystallized from acetone/ petroleum ether (1:10 v/v). Mp = 142−143 °C. 1H NMR (400 MHz, acetone) δppm: 10.52 (s, 1H, N−H), 8.04 (d, J = 7.9 Hz, 1H, carbazole-ArH), 7.52 (d, J = 8.1 Hz, 1H, carbazole-ArH), 7.45−7.29 (m, 5H, carbazole-ArH), 7.18−7.06 (m, 4H, phenyl ArH), 6.69 (d, J = 7.0 Hz, 1H, phenyl ArH). 13C NMR (101 MHz, acetone) δppm: 158 (1C), 153 (1C), 143 (1C), 141 (1C), 131 (1C), 127 (1C), 126 (1C), 124 (1C), 124 (1C), 122 (1C), 120 (1C), 119 (1C), 116 (1C), 112 (1C), 111 (1C), 109 (1C), 108 (1C), 107 (1C). FT-IR ν (cm−1): 3424 (N−H), 3154 (C− H, aromatic), 1601, 1509, 1466, 1403 (CC), 1242 (C− N). ESI-MS m/z: 261 (cation+). 2.3.3. Synthesis of 1,4-Bis((9H-carbazol-4-yl)oxy) Benzene (11). A pale yellow solid (82%), the product was crystallized from acetone/petroleum ether (1:10 v/v). Mp = 130−131 °C; 1 H NMR (400 MHz, acetone) δppm: 10.53 (s, 2H, N−H), 8.15 (d, J = 7.9 Hz, 2H, carbazole-ArH), 7.55 (d, J = 8.1 Hz, 2H, carbazole-ArH), 7.44 − 7.29 (m, 6H, carbazole-ArH), 7.22 (s, 4H, phenyl-ArH), 7.18 (t, J = 7.5 Hz, 2H, carbazole-ArH), 6.70 (d, J = 7.5 Hz, 2H, carbazole-ArH). 13C NMR (101 MHz, acetone) δppm: 154 (2C), 153 (2C), 143 (4C), 141 (2C), 127 (2C), 126 (2C), 124 (2C), 121 (2C), 120 (2C), 111 (4C), 108 (2C), 107 (4C). FT-IR ν (cm−1): 3395 (N−H), 3093 (C−H, aromatic), 1576, 1482, 1454, 1440 (CC), 1217 (C−N). ESI-MS m/z: 442 (cation+).

As a nucleophile, 2 shows higher reactivity with the chlorobenzene iron complexes than 1. Compound 2 reacts with 3 and 4 at room temperature. It completely reacts with 3 at a molar ratio of 1:1 within 6 to 8 h, and the produced 6 shows a high yield of around 91% with no N-substituted byproducts. 1 requires a higher temperature to react and needs to be slightly in excess to attack chlorobenzene iron complexes efficiently. When the reaction temperature reaches 60 °C, the expected nucleophilic substitution product 5 is obtained, with a yield of 95%. Therefore, a suitably low temperature is very important for the 2 reaction system avoid side N-substituted reactions. Compound 4 is more active and could be completely reacted with 2 and 1 within a shorter period of time compared with 3. The reaction conditions and results of SNAr are shown in Table 1. The four cyclopentadienyliron complexes of arylated carbazoles (Fc-carbazoles) were conveniently purified by recrystallization. Our recrystallization of the Fc-carbazoles was processed in DMF/methyl tertiary butyl ether. The DMF/ methyl tertiary butyl ether system is not as volatile as the dichloromethane/diethyl ether system reported in a previous paper.46 Compounds 1 and 2 show good solubility in methyl tertiary butyl ether, so the unreacted 1 and 2 could be wholly removed by recrystallization. 3648



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Table 1. Reaction Conditions and Results of SNAr for the Preparation of Fc-carbazoles arene iron complex

1 (eq)

5 6 7 8

1.25

2 (eq) 1 2.5

2.5

3 (eq)

4 (eq)

K2CO3 (eq)

temp. (°C)

time (h)

conv. (%)

1 1

2 1 2 2

60 20 20 60

6 8 6 4

95 91 87 90

1 1

3.2. Photolysis of Fc-carbazoles. One of the most important steps in the synthetic strategy is the liberation of the desired arene ligands from cyclopentadienyliron complexes. Photolysis is an efficient route for the decomplexation of some cyclopentadienyliron arene complexes.47,50,51 In this paper, this technique was used to liberate the arylated carbazoles. The samples were irradiated in dichloromethane using a halogen lamp as a source of irradiation. Pure arylated carbazoles were successfully obtained, as determined by IR, LC-MS (liquid chromatography mass spectroscopy), and NMR. Figure 2

Figure 3. 1H NMR spectra of 5 under the different irradiation times.

The 1H NMR spectra of 6, 7, and 8 with increased irradiation time are provided in the Supporting Information. The 1H NMR results show that all four iron complexes could liberate arylsubstituted carbazoles and ferrocene as products. Some precipitates are also observed in the solution, which may be iron(II) salts formed by ferrous ions and hexafluorophosphate. Therefore, Fc-carbazoles follow the photolysis process, as shown in Scheme 2. This process is consistent with previous literature.52,53 Scheme 2. Photolysis of Fc-carbazole

Figure 2. 1H NMR spectra of the arylated carbazoles.

shows the 1H NMR spectra of the purified products. The samples show peaks at 6.0 ppm to 8.3 ppm, characterizing the Ar−H bond of the carbazolyl arenes. Different from 9 and 12, 10 and 11 show the characteristic peak of the exposed N−H at 10.5 ppm. 1 H NMR spectroscopy was also used to observe the demetalation process of the four carbazolyl organoiron complexes. The Fc-carbazoles were dissolved in dimethyl sulfoxide-d6 at a concentration of 2 × 10−2 mol/L. The samples were irradiated under a halogen lamp (I = 40 mW/cm2) and subjected to 1H NMR spectroscopy at intervals. Figure 3 shows the change in the 1H NMR spectra of 5 with increased irradiation time. The characteristic peak of cyclopentadiene at 5.25 ppm gradually disappeared under irradiation, demonstrating the occurrence of decomplexation from cationic cyclopentadienyliron complexes. Changes in the region from 6 ppm to 11 ppm indicate that the Ar−H peaks of the liberated aryl-substituted carbazoles gradually substitute those of Fccarbazole. Based on the 1H NMR spectra, these newly generated aryl-substituted carbazoles show no changes under irradiation, which demonstrates their good photostability. The formation of ferrocene may be observed from the 1H NMR spectra, with a new peak appearing at 4.17 ppm due to the complexation of liberated cyclopentadiene and ferrous ions.

3.3. Photodemetalation Rate. Based on the 1H NMR spectra in Figure 3 and Figures S1−S3 (Supporting Information), the photodemetalation rates of Fc-carbazoles were investigated by calculating the characteristic peak area changes in cyclopentadienyl (Cp) at about 5.20 ppm with respect to irradiation time. The calculated results are shown in Figure 4. The Fc-carbazoles, 5, 6, 7, and 8, exhibit rapid photodemetalation. The demetalations of 5 and 8 occur faster than those of 6 and 7 under the same conditions. Using the same method for calculating the characteristic peak area changes in cyclopentadienyl (Cp) in the 1H NMR spectra, the relationship between the completed demetalation time and the concentrations of the Fc-carbazoles was investigated, and the results are shown in Figure 5. The demetalation time linearly increases with the concentrations of the Fc-carbazoles. The photodemetalation rate order of 5, 6, 7, and 8 is consistent with that shown in Figure 4. The order of photodemetalation rate of Fc-carbazoles is 8 > 5 > 7 > 6. The N-phenyl-substituted Fc-carbazoles show more rapid photodemetalation than O-phenyl-substituted Fc-carbazoles. Double-substituted Fc-carbazoles photodemetallate more rapidly than monosubstituted Fc-carbazoles, which may be due to the wider absorption wavelength of the double-substituted 3649



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carbazole) with high yields. Our methodology is easy, economical, and avoids the use of transition metal catalysts for the preparation of arylated carbazoles. Based on the 1H NMR spectra, the demetalation process of Fc-carbazole and the activities of demetalation among different Fc-carbazoles were demonstrated. Overall, the N-phenyl-substituted carbazolyl cyclopentadienyliron complexes 5 and 8 show faster photodemetalation rates than the phenoxyl-substituted carbazolyl cyclopentadienyliron complexes 6 and 7. Considering their industrial applications, arylated carbazoles were subjected to crystallization as a purification strategy instead of column chromatography.

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Figure 4. Photodemetalation conversions of Fc-carbazoles with the irradiation time.

ASSOCIATED CONTENT

* Supporting Information S

Figures S1−S4 as described in the text. This information is available free of charge via the Internet at http://pubs.acs.org/.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: 0086 013691179175. Fax: 0086-010-64445350. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors wish to thank for financial support of national natural science foundation of China (Project Grant No. 21176016).

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Figure 5. Completed demetalation time changes of Fc-carbazole with different concentrations.

REFERENCES

(1) Czerwonka, R.; Reddy, K. R.; Baum, E.; Knölker, H. J. First enantioselective total synthesis of neocarazostatin B, determination of its absolute configuration and transformation into carquinostatin A. Chem. Commun. 2006, 711−713. (2) Nagappan, T.; Ramasamy, P.; Wahid, M. E.; Segaran, T. C.; Vairappan, C. S. Biological activity of carbazole alkaloids and essential oil of Murraya koenigii against antibiotic resistant microbes and cancer cell lines. Molecules 2011, 16, 9651−9664. (3) Chakraborty, D. P.; Shyamali, R. Carbazole alkaloids IV. Prog. Chem. Org. Nat. Prod. 2003, 85, 128−230. (4) Schmidt, A. W.; Reddy, K. R.; Knölker, H. J. Occurrence, biogenesis, and synthesis of biologically active carbazole alkaloids. Chem. Rev. 2012, 112, 3193−3328. (5) Knölker, H. J.; Reddy, K. R. Isolation and synthesis of biologically active carbazole alkaloids. Chem. Rev. 2002, 102, 4303−4427. (6) Choi, T. A.; Czerwonka, R.; Fröhner, W.; Krahl, M. P.; Reddy, K. R.; Franzblau, S. G.; Knölker, H. J. Synthesis and activity of carbazole derivatives against mycobacterium tuberculosis. ChemMedChem 2006, 1, 812−815. (7) Forke, R.; Krahl, M. P.; Krause, T.; Schlechtingen, G.; Knölker, H. J. Transition metals in organic synthesis, part 82. First total synthesis of methyl 6-methoxycarbazole-3-carboxylate, glycomaurrol, the anti-TB active micromeline, and the furo[2,3-c] carbazole alkaloid eustifoline-D. Synlett 2007, 2, 268−272. (8) Kim, S. H.; Cho, L.; Sim, M. K.; Park, S.; Park, S. Y. Highly efficient deep-blue emitting organic light emitting diode based on the multifunctional fluorescent molecule comprising covalently bonded carbazole and anthracene moieties. J. Mater. Chem. 2011, 21, 9139− 9148. (9) Grazulevicius, J. V.; Strohriegl, P.; Pielichowski, J.; Pielichowski, K. Carbazole-containing polymers: Synthesis, properties, and applications. Prog. Polym. Sci. 2003, 28, 1297−1353. (10) Shin-ichiro, K.; Hiroto, N.; Atsushi, K.; Toshitada, Y.; Seiji, T.; Yosuke, N. Bicarbazoles: Systematic structure-property investigations

carbazolyl iron complexes compared with their corresponding monosubstituted iron complexes. This wider absorption wavelength helps the double-substituted complexes make full use of light. The UV−vis spectra of Fc-carbazoles are shown in Figure S4 (Supporting Information). 3.4. Separation of Aryl-Substituted Carbazoles. In a previously reported method,42 the separation of the products from demetalations was carried out by column chromatography, which is not suitable for large-scale production. Thus, determining a simple method to separate the products from demetalations is important. After demetalations of cationic cyclopentadienyliron complexes of arylated carbazole were completed, aryl-substituted carbazoles, ferrocene, and iron(II) salts were produced. The iron(II) salts could be separated by filtration as precipitates and then washed with water. The aryl-substituted carbazoles and ferrocene left in the organic solution were concentrated by evaporating the solvent. Aryl-substituted carbazoles and ferrocene could be separated by crystallization with a certain proportion of acetone/petroleum ether because of their different solubilities. The aryl-substituted carbazoles were finally obtained by filtration. This purification strategy is much easier to perform than column chromatography. The obtained ferrocene is part of the iron recovery source and could be reused.

4. CONCLUSION Aryl-substituted carbazoles, including 9, 10, 11, and 12, were prepared by the rapid and efficient photolysis of cationic cyclopentadienyliron complexes of arylated carbazole (Fc3650



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on a series of conjugated carbazole dimers. J. Org. Chem. 2012, 77, 9120−9133. (11) Jiang, W.; Duan, L.; Qiao, J.; Dong, G. F.; Zhang, D. Q.; Wang, L. D.; Qiu, Y. Novel carbazole/pyridine-based host material for solution-processed blue phosphorescent organic light-emitting devices. Dyes Pigments 2012, 92, 891−896. (12) Frau, A. F.; Pernites, R. B.; Advincula, R. C. A conjugated polymer network approach to anticorrosion coatings: poly(vinylcarbazole) electrodeposition. Ind. Eng. Chem. Res. 2010, 49, 9789−9797. (13) Lee, R. H.; Liu, L. W. Electroluminescence and photovoltaic properties of light-emitting devices and solar cells comprising 2-pyran4-ylidene-malononitrile conjugated polymers. Dyes Pigments 2010, 84, 190−202. (14) Romeroa, D. H.; Schaer, M.; Lecler, M.; Ades, D.; Siove, A.; Zuppiroli, L. The role of carbazole in organiclight-emitting devices. Synth. Met. 1996, 80, 271−277. (15) Hemraj, J.; Jae-min, S.; Kyu-Sung, J. Indoles and related heterocycles. Top. Heterocycl. Chem. 2010, 24177−24204. (16) Chmielewski, M. J.; Charon, M.; Jurczak, J. 1,8-Diamino-3,6dichlorocarbazole: A promising building block for anion receptors. Org. Lett. 2004, 6, 3501−3504. (17) Tsuchimoto, T.; Matsubayashi, H.; Kaneko, M.; Nagase, Y.; Miyamura, T.; Shirakawa, E. Indium-catalyzed annulation of 2-aryland 2-heteroarylindoles with propargyl ethers: Concise synthesis and photophysical properties of diverse aryl- and heteroaryl-annulated[a]carbazoles. J. Am. Chem. Soc. 2008, 130, 15823−15835. (18) Tsvelikhovsky, D.; Buch-wald, S. L. Concise palladium-catalyzed synthesis of dibenzodiazepines and structural analogues. J. Am. Chem. Soc. 2011, 133, 14228−14231. (19) Adhikari, R. M.; Neckers, D. C.; Shah, B. K. Photophysical study of blue, green, and orange-red light-emitting carbazoles. J. Org. Chem. 2009, 74, 3341−3349. (20) Fu, H. Y.; Wu, H. R.; Hou, X. Y.; Xiao, F.; Shao, B. X. N-Aryl carbazole derivatives for non-doped red OLEDs. Synth. Met. 2006, 156, 809−814. (21) Knölker, H. J. Transition metal complexes in organic synthesis, Part 70. Synthesis of biologically active carbazole alkaloids using organometallic chemistry. Curr. Org. Synth. 2004, 1, 309−331. (22) Joyeeta, R.; Amit, K. J.; Dipakranjan, M. Recent trends in the synthesis of carbazoles: An update. Tetrahedron 2012, 68, 6099−6121. (23) Boerger, C.; Knölker, H. J. Transition metals in organic synthesis. Part 101: Convergent total synthesis of 1,6-dioxygenated carbazole alkaloids. Tetrahedron 2012, 68, 6727−6736. (24) Knölker, H. J. Synthesis of biologically active carbazole alkaloids using selective transition-metal-catalyzed coupling reactions. Chem. Lett. 2009, 38, 8−13. (25) Börger, C.; Kataeva, O.; Knölker, H. J. Novel approach to biscarbazole alkaloidsvia Ullmann coupling-synthesis of murrastifolineA and bismurrayafoline-A. Org. Biomol. Chem. 2012, 10, 7269−7233. (26) Antilla, J. C.; Klapars, A.; Buchwald, S. L. The copper-catalyzed N-arylation of lndoles. J. Am. Chem. Soc. 2002, 124, 11684−11688. (27) Li, E.; Xu, X. B.; Li, H. F.; Zhang, H. M.; Xu, X. L.; Yuan, X. Y.; Li, Y. Z. Copper-catalyzed synthesis of five-membered heterocycles via double C−N bond formation: An efficient synthesis of pyrroles, dihydropyrroles, and carbazoles. Tetrahedron 2009, 65, 8961−8968. (28) Babu, S. G.; Karvembu, R. CuO nanoparticles: a simple, effective, ligand free, and reusable heterogeneous catalyst for Narylation of benzimidazole. Ind. Eng. Chem. Res. 2011, 50, 9594−9600. (29) Cambie, R. C.; Janssen, S. J.; Rutledge, P. S.; Woodgate, P. D. Towards the synthesis of amino[b,e][1,4]dioxin derivatives via cationic ruthenium complexes. J. Organomet. Chem. 1996, 507, 1−21. (30) Pearson, A. J.; Park, J. G.; Zhu, P. Y. Studies on selective nucleophilic substitution reactions of [(cyclopentadienyl)(1,3dichlorobenzene)M]+PF6− complexes (M = iron, ruthenium). J. Org. Chem. 1992, 57, 3583−3589. (31) Sutherland, R. G.; Abd-El-Aziz, A. S.; Piorko, A.; Gill, U. S.; Lee, C. C. A novel approach to synthesis of the cinnoline ring system via

organoiron(cyclopentadienyl) complexes. J. Heterocycl. Chem. 1988, 25, 1107−1110. (32) Lee, C. C.; Abd-El-Aziz, A. S.; Chowdhury, R. L.; Gill, U. S.; Piorko, A.; Sutherland, R. G. Studies on nucleophilic substitution reactions with η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate. J. Organomet. Chem. 1986, 315, 79−92. (33) Lee, C. C.; Zhang, C. H.; Abd-El-Aziz, A. S.; Piórko, A.; Sutherland, R. G. Studies on some mono- and di-substitution reactions with cyclopentadienyliron complexes of o-, m-, and p-dichlorobenzenes. J. Organomet. Chem. 1989, 364, 217−229. (34) Sutherland, R. G.; Chowdhury, R. L.; Piorko, A.; Lee, C. C. Functionalization of aromatic and heterocyclic systems. Regioselective introduction of 2-oxoalkyl chain or cyano functions via organoiron complexes. J. Org. Chem. 1987, 52, 4618−4620. (35) Abd-El-Aziz, A. S.; Okasha, R. M.; Todd, E. K.; Afifi, T. H.; Shipman, P. O.; Copping, K.; Michelle, D. Synthesis of iron-containing polymers with azo dyes in the backbones or side chains. Macromol. Symp. 2004, 209, 185−193. (36) Abd-El-Aziz, A. S.; Lei, Y.; De Denus, C. R. Aliphatic diols in the synthesis of bis(cyclopentadienyliron) arene complexes. Polyhedron 1995, 14, 1585−1591. (37) Abd-El-Aziz, A. S.; Schriemer, D. C. The synthesis of new di(cyclopentadienyliron) complexes of polyaromatic ethers. Inorg. Chim. Acta 1992, 202, 123−125. (38) Abd-el-Aziz, A. S.; Piorko, A.; Lee, C. C.; Sutherland, R. G. Studies on some selective and competitive substitution reactions of cyclopentadienyliron complexed chloronitrobenzenes with amines as nucleophiles. Can. J. Chem. 1989, 67, 1618−1623. (39) Abd-El-Aziz, A. S.; Todd, E. K.; Okasha, R. M.; Shipman, P. O.; Wood, T. E. Macromolecules containing redox-active neutral and cationic iron complexes. Macromolecules 2005, 38, 9411−9419. (40) Abd-El-Aziz, A. S.; Pereira, N. M.; Winram, D. J.; Sidhu, P.; Knölker, S. Synthesis and polymerization of a four-arm star with pendent cyclopentadienyliron moieties. J. Inorg. Organomet. Polym. 2007, 17, 275−281. (41) Abd-El-Aziz, A. S.; Lee, C. C.; Piorko, A.; Sutherland, R. G. Arylation of diethyl malonate via nucleophilic substitution reactions with cyclopentadienyliron complexes of chloroarenes. Synth. Commun. 1988, 18, 291−300. (42) Piórko, A.; Abd-El-Aziz, A. S.; Lee, C. C.; Sutherland, R. G. Arylation of diethyl alkylmalonates: Synthetic route to diethyl alkyl (substituted aryl) malonates with the aid of temporary arene complexation by the cyclopentadienyliron moiety. J. Chem. Soc., Perkin Trans. I 1989, 3, 469. (43) Abd-El-Aziz, A. S.; de Denus, C. R. Synthesis of isomeric ethyl tolylcyanoacetates using organo-iron complexes. Synth. Commun. 1992, 22, 581−591. (44) Pearson, A. J.; Park, J. G.; Yang, S. H.; Chuang, Y. H. A mild procedure for the selective formation of aryl ethers and triaryl diethers using arene-M-Cp cations (M = Fe, Ru; Cp = η5-cyclopentadienyl). J. Chem. Soc., Chem. Commun. 1989, 1363−1364. (45) Abd-El-Aziz, A. S.; Lee, C. C.; Piorko, A.; Sutherland, R. G. Studies on nucleophilic substitution reactions with cyclopentadienyliron complexes of some chloroarenes and nitroarenes and syntheses of substituted arenes by demetallation of the substitution products. J. Organomet. Chem. 1988, 348, 95−107. (46) Abd-El-Aziz, A. S.; de Denus, C. R. A convenient synthesis of some arylated phenylsulfonylacetonitriles and ethyl cyanoacetates using organo-iron complexes. J. Chem. Soc. Perkin Trans. 1 1993, 293− 298. (47) Abd-El-Aziz, A. S.; Tesfalidet, S.; de Denus, C. R.; Lezynska, K. A novel approach to the synthesis of some 2-arylalkanoic acid esters. Synth. Commun. 1993, 23, 1415−1426. (48) Steinhoff, G. W.; Henry, M. C. Reaction of benzyne with nitrosobenzene. A new route to the carbazole ring system. J. Org. Chem. 1964, 29, 2808−2809. (49) Gilman, H.; Honeycutt, J. B. NotesSome aromatic and heterocyclic derivatives of carbazole. J. Org. Chem. 1957, 22, 226−227. 3651



Article

(50) Abd-El-Aziz, A. S.; Lee, C. C.; Piorko, A.; Sutherland, R. G. Arylation of diethyl malonate via nucleophilic substitution reactions with cyclopentadienyliron complexes of chloroarenes. Synth. Commun. 1988, 18, 291−300. (51) Hamon, J. R.; Saillard, J. Y.; Le Beuze, A.; McGlinchy, M. G.; Astruc, D. Organometallic electron reservoirs. 7. One-step multiple formation of carbon-carbon bonds in CpFe+ (arene) sandwiches and unusual C6Et6 geometry in the X-ray crystal structure of CpFe+ (.eta.6-C6Et6) PF6−. J. Am. Chem. Soc. 1982, 104, 7549−7555. (52) Catilaz-Simonin, L.; Fouassier, J. P. Investigation of a system capable of photoinitiating radical polymerizations in thick pigmented media. J. Appl. Polym. Sci. 2001, 79, 1911−1923. (53) Karatsu, T.; Shibuki, Y.; Miyagawa, N.; Takahara, S.; Kitamura, A.; Yamaoka, T. Mechanistic investigations of the photosensitized reactions of iron arene complexes. J. Photochem. Photobiol. A: Chem. 1997, 107, 83−91.

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Efficient Synthesis of Arylated Carbazole from Cyclopentadienyliron

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