Modular Synthesis of Carbazole-Based Conjugated Molecules

Article Cite This: J. Org. Chem. 2017, 82, 11182-11191

pubs.acs.org/joc

Modular Synthesis of Carbazole-Based Conjugated Molecules through a One-Pot Annulation/Dehydrogenation Sequence Shanping Chen, Liren Wang, Jing Zhang, Zhaoran Hao, Huawen Huang,* and Guo-Jun Deng* Key Laboratory for Green Organic Synthesis and Application of Hunan Province, Key Laboratory of Environmentally Friendly Chemistry and Application of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan 411105, China S Supporting Information *

ABSTRACT: An efficient one-pot indole-to-carbazole strategy with cyclohexanones as the aryl source is described. This cascade carbazole formation is enabled by the NH4I-catalyzed annulation of indoles, cyclohexanones, and alkenes and subsequent dehydrogenative aromatization. The present work provides a modular synthesis of arylcarbazoles, benzocarbazoles, and naphthocarbazoles with excellent regioselectivity and broad functional group tolerance. More than 40 benzo-fused carbazoles were synthesized, and the UV−vis absorption and photoluminescent spectra of some products were measured to study their photophysical properties.

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INTRODUCTION Carbazole and its derivatives are important nitrogen-containing heterocycles since many of them show important biological activities in pharmaceuticals.1 Some benzo and naphthocarbazole analogues have been explored as potential anticancer agents and show promising profiles for intracyclin dependent kinase selectivity (Figure 1, compounds A and B).2 Moreover,

Dehydrogenative aromatization represents an efficient tool for the direct construction of aromatic compounds.8 Among the nonaromatic precursors, cyclohexanones provide facile entries to a broad range of aromatic functionalized molecules including phenols,9 anilines,10 biarenes,11 benzoheterocycles,8,12 and among others. In our recent indole-to-carbazole transformation,13 aliphatic ketones especially cyclic ketones featured a very low reactivity for the carbazole formation, which was thereafter attributed to the invalidity of oxygen set as the oxidant. While a higher pressure oxygen features a higher oxidative reactivity, special equipment to handle it is required and, more importantly, it may cause safe issue especially in a large-scale synthesis. Within our own program on indole-templated synthesis, herein, we report a catalytic annulation/dehydrogenation sequence for the one-pot synthesis of carbazole-based conjugated molecules from easily available indoles, alkenes, and ketones. In this cascade reaction, NH4I found high catalytic activity for the three-component annulation and DDQ was chosen as the oxidant for the dehydrogenative aromatization. The present protocol provides a modular synthesis of polysubstituted carbazoles, benzocarbazoles, and naphthocarbazoles with a broad range of functional groups tolerated (Scheme 1).

Figure 1. Valuable carbazole-containing molecules.

the studies on photophysical properties of carbazole-based conjugated molecules have received a great deal of attention in materials science.3 For example, carbazole-based molecules such as polymers C have found applications as organic lightemitting materials due to the wide band gap and high luminescent efficiency, and benzo[2,3-c]carbazoles D have been used in novel functional organic light-emitting diodes (OLEDs).3i,j Accordingly, numerous synthetic methods to construct functionalized carbazoles were reported, including classic Fischer−Borsche synthesis,4 transition-metal-catalyzed cyclization,5 and indole-templated carbazole formation.6 However, many of them rely on prefunctionalization of the precursors and multistep procedure.7 Thus, it is still desirable to develop a facile synthesis of carbazole-based conjugated molecules from simple and readily available chemicals. © 2017 American Chemical Society

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RESULTS AND DISCUSSION We commenced our studies by exploring the reaction conditions of the three-component annulation of indole 1a, cyclohexanone 2a, and n-butyl acrylate 3a (Table 1). Hence, we observed the expected three-component assembly with iodine catalysts such as elemental I2, KI, ICl, and NIS, which afforded Received: September 12, 2017 Published: September 28, 2017 11182

DOI: 10.1021/acs.joc.7b02305 J. Org. Chem. 2017, 82, 11182−11191

Article

The Journal of Organic Chemistry

Scheme 2. Substrate Scope of the Benzocarbazole Synthesisg

Scheme 1. Modular Synthesis of Carbazoles and Fused Carbazoles

Table 1. Screening the Reaction Conditionsa

entry

catalyst

solvent

T (°C)

yield (%)b

1 2 3 4 5 6 7 8 9 10 11 12 13 14

I2 KI ICl NIS NH4I (Me)4NI NH4I NH4I NH4I NH4I NH4I NH4I NH4I NH4I

toluene toluene toluene toluene toluene toluene ethylbenzene chlorobenzene PhCF3 1,4-dioxane anisole NMP toluene toluene

150 150 150 150 150 150 150 150 150 150 150 150 160 140

24 34 15 23 93 (76)c 0 80 84 57 61 76 37 78 81

a

a

Yield from 5 mmol scale reaction. bRegioselectivity of 5:1 was observed. c Ethyl acrylate (4.0 equiv). d Combined with the decarboxylated product (7f). eAcrylic acid was used. fAcrylonitrile (4.0 equiv). gEWG = electron-withdrawing group. E = CO2n-Bu.

the annulation product 4a as the major product with excellent levels of regioselectivity combined with recovered starting materials (entries 1−4). The catalytic annulation proved most effective with a catalytic system comprising NH4I in toluene as the solvent, which enabled the annulation with 93% yield of 4a and accordingly gave the dehydrogenated product benzocarbazole 5a in good yield by DDQ treatment (entry 5). Catalytic amounts of (Me)4NI did not work at all on the transformation (entry 6), which indicated in turn the NH4I catalyst probably played an acid role. However, the use of normal Brønsted acids and Lewis acids was found to have a much lower efficiency, and instead a mess system was generally resulted in. Then besides toluene, a series of solvents were screened, and among them, those with a low polarity generated the annulation product in moderate to good yield, while high polar NMP afforded 4a in 37% yield (entries 7−12). Other reaction temperatures were found to be inferior (entries 13, 14). With the optimized reaction conditions in hand, the generality of the one-pot annulation/dehydrogenation reaction cascade was investigated (Scheme 2). Generally, moderate to

good yields were obtained when a number of substituted indoles, cyclohexanones, and electron-withdrawing alkenes were subjected to the two-step sequence. The remarkable efficacy of our benzocarbazole synthesis was reflected by the tolerance of a broad range of functional groups attached to the cyclohexanones and indoles. For example, indoles bearing allyl (6b), halo (6g−h, 6k−m), and ester (6i) functionalities were readily compatible with the one-pot reaction, which provided potential access to a broader range of carbazole-based molecules. Furthermore, arylcyclohexanones worked smoothly to give arylsubstituted benzocarbazoles (5g−h), which thereby directly extended the π-conjugated system of the product. With respect to the scope of alkenes, several acrylates were employed and successfully transformed into benzocarbazoles 7. Specifically, an excessive amount of ethyl acrylate was necessary to get a satisfactory yield (7a). While tert-butyl acrylate afforded the desired product in 61% yield combined with a certain amount of the decarboxylated product (7e), acrylic acid generated the decarboxylated product 7f in a modest yield. Other electronwithdrawing alkenes such as acrylonitrile (7g) and dimethyl fumarate (7h) were also accommodated in the one-pot reaction system. Remarkably, the gram-scale reactions were found to be effective (5a, 6m). In coordination with our previous carbazole synthesis by aerobic dehydrogenation, the present one-pot protocol also

Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol, 2.0 equiv), 3a (0.4 mmol, 2.0 equiv), catalyst (0.02 mmol, 10 mol %), solvent (0.5 mL, sealed tube), 24 h. bThe yields of 4a were determined by GC analysis using dodecane as the internal standard. cThe yield in parentheses refers to the yield of 5a by the one-pot treatment of DDQ (0.9 mmol, 4.5 equiv) at 50 °C for 24 h.

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Article

The Journal of Organic Chemistry provides alternative access to 4-arylcarbazoles (Scheme 3). Generally, this two-step sequence tolerated a number of

Scheme 4. One-Pot Formation of Naphthocarbazoles

Scheme 3. One-Pot Formation of Arylcarbazoles

compounds (Figure 2a,c). As compared to compound 5a, a slight bathochromic shift of the emission peak was shown in the π-conjugated extension system of compounds 5g and 10, while a blue-shift was shown in the benzo system of compound 9a due to its poor planarity (Figure 2b). In neat film, the emission spectra of all compounds were broadened and red-shifted, and compound 9c shows a strong aggregation emission at a lower energy (Figure 2d). Notably, the powder of compound 5a, 9a, and 9c can emit different colors obviously under UV light (Figure 2e). The photophysical data for these carbazoles are summarized in Table 2. These results above indicate that these carbazole-based conjugated compounds may have an application on organic light-emitting diodes (OLEDs), especially on high-efficiency blue OLEDs.14

substituted acetophenones bearing functional groups such as methoxy, nitro, nitrile, sulfone, chloro, and bromo. Among them, substrates with electron-withdrawing groups afforded higher yields of the target products, and 4-methoxylacetophenone generated the product 8b in 49% yield. Notably, 2acetothiophene also smoothly underwent the desired annulation/dehydrogenation with indole 1a and acrylate 3a, affording the thienylcarbazole 8k in a modest yield. The robust nature of the sequential catalytic annulation and mild dehydrogenation was further reflected by the successful three-component annulation of indoles, alkenes, and βtetralones, which generated naphthocarbazoles 9 with the πconjugated system further extended (Scheme 4). These reactions afforded functionalized naphtho[1,2-c]carbazole 9a− h in moderate yields with the synthetically useful halo and pharmacologically significant methoxy group tolerated. Then, the synthetic utility of our one-pot three-component reaction was shown by the late-stage modification of bromosubstituted benzocarbazole 6m (Scheme 5). For example, Pd(0)-catalyzed Suzuki−Miyaura coupling and Sonogashira coupling afforded benzocarbazoles 10 and 11, respectively, with the π-conjugated system of the molecules further extended (Scheme 5a,b). Moreover, carboxylic acid 12 was readily generated in a good yield under normal hydrolysis conditions (Scheme 5c). Accordingly, we noted that all of our products are fluorescent under ultraviolet light. In order to have a brief insight into their photophysical properties and a glance at the impact of decoration on the molecular skeleton, the UV−vis absorption and photoluminescence spectra of compound 5a, 5g, 9a, 9b, 9c, and 10 were preliminary investigated. As shown in Figure 2, all of these selected compounds show similar absorption profiles, except for a bathochromic shift of the π−π* transitions band around 300 nm with an increasing conjugation length in those

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CONCLUSION In summary, we have developed a modular synthesis of carbazole-based conjugated compounds through a one-pot three-component reaction cascade. Easily available indoles, ketones, and alkenes were employed as the starting materials. This protocol afforded arylcarbazoles, benzocarbazoles, and naphthocarbazoles by the catalytic annulation and subsequent oxidative aromatization. The products were generated in moderate to good yields with excellent regioselectivity and broad functional group tolerance. The studies on the photophysical properties indicated that the resultant carbazole-based conjugated compounds have potential applications on the materials of high-performance organic light-emitting diodes (OLEDs).

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EXPERIMENTAL SECTION

General Information. All reactions were carried out under the standard conditions unless otherwise noted. Column chromatography was performed using silica gel (200−300 mesh). 1H NMR and 13C NMR spectra were recorded on a 400 MHz NMR spectrometer, and the chemical shifts were referenced to signals at 7.26 and 77.0 ppm, respectively. Generally, chloroform was used as the solvent with TMS as the internal standard. GC−MS data were obtained using electron 11184


Article

The Journal of Organic Chemistry Scheme 5. Diversification of the Resultant Benzocarbazole 6ma

Reaction conditions: (a) 6m (0.2 mmol), PhB(OH)2 (1.2 equiv), Pd(PPh3)4 (40 mol %), K2CO3 (1.2 equiv), DMF (0.1 M), H2O (0.8 M), 80 °C, Ar, 12 h; (b) 6m (0.1 mmol), phenylacetylene (2.0 equiv), Pd(PPh3)2Cl2 (5 mol %), CuI (10 mol %), PPh3 (30 mol %), DMF (0.25 M), triethylamine (0.5 M), 160 °C, Ar, 12 h; (c) 6m (0.5 mmol), NaOH (3 N), EtOH (0.04 M), reflux, 24 h. a

Figure 2. Photophysical studies. (a)(c) UV−vis absorption spectra in a DCM solution. (b)(d) Photoluminescence spectra in a DCM solution (solid line) and in film (dotted line) at 298 K. (e) Fluorescent compounds under UV light (365 nm). correction. The UV−vis absorption and photoluminescent spectra were obtained from a dichloromethane (DCM) solution and recorded with a Varian Cray 50 UV−vis spectrophotometer and PTI Q40 luminescence spectrometer, respectively. All reagents were obtained from commercial suppliers and used without further purification. General Procedure for Benzocarbazoles Synthesis (5−7). Ammonium iodide (2.9 mg, 0.02 mmol) was added to a 20 mL ovendried reaction vessel. To the reaction vessel were added 1-methyl-1Hindole (25.0 μL, 0.2 mmol), cyclohexanone (41.6 μL, 0.4 mmol), butyl acrylate (57.4 μL, 0.4 mmol), and toluene (0.5 mL) by a syringe. The reaction vessel was stirred at 150 °C for 24 h. After cooling the mixture to room temperature, DDQ (204.3 mg, 0.9 mmol) and toluene (0.1 mL) were added to the reaction vessel. The reaction vessel was stirred at 50 °C for 24 h. After cooling to room temperature, the mixture was purified by column chromatography on aluminum oxide (neutral) (petroleum ether/EtOAc = 50:1) to yield the desired product 5a as a white solid (50.3 mg, 76% yield), mp 104−106 °C. Rf = 0.48 (petroleum ether/EtOAc = 50:1). Ammonium iodide (5.8 mg, 0.04 mmol) was used, and the temperature was 160 °C when synthesizing arylcarbazoles 8. The procedure for naphthocarbazoles is the same with the synthesis of

Table 2. Photophysical Data for Carbazoles 5a, 5g, 9a, 9b, 9c, and 10 photoluminescence carbazole

excitation (λ/nm)

5a 5g 9a 9b 9c 10

334 340 346 354 348 344

a

absorption (λmax/nm) 271, 260, 287, 285, 290, 252,

295, 292, 294, 298, 324, 281,

334, 306, 320, 326, 348, 344

381 390 346 354 401

solutiona (λmax/nm)

filmb (λmax/nm)

447 453 438 437 443, 505 452

462 471 454 447, 470 498, 518 464

a Measured in a DCM solution at ambient temperature. bMeasured in a poly(methyl methacrylate) film at ambient temperature.

ionization. HRMS was carried out on a high-resolution mass spectrometer (ESI, LCMS-IT-TOF). The structure of known compounds was further corroborated by comparing their 1H NMR, 13 C NMR, and MS data with those in literature. Melting points were measured with a BÜ CHI B-545 melting point instrument without 11185


Article


Butyl 7-Methyl-3-phenyl-7H-benzo[c]carbazole-6-carboxylate (5g). White solid (63.5 mg, 78% yield), mp 100−102 °C. Rf = 0.43 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 8.88 (d, J = 8.7 Hz, 1H), 8.62 (d, J = 8.0 Hz, 1H), 8.35 (s, 1H), 8.24 (s, 1H), 8.03 (d, J = 8.8 Hz, 1H), 7.78 (d, J = 7.6 Hz, 2H), 7.62−7.50 (m, 4H), 7.43−7.40 (m, 2H), 4.50 (t, J = 6.8 Hz, 2H), 3.99 (s, 3H), 1.91−1.84 (m, 2H), 1.59−1.53 (m, 2H), 1.04 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.9, 141.4, 140.8, 136.1, 135.6, 130.3, 130.2, 128.9, 128.1, 127.8, 127.7, 127.2, 124.9, 123.5, 122.9, 122.0, 120.3, 118.4, 117.2, 109.8, 65.5, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C28H26NO2 [M + H]+, 408.1958; found, 408.1961. Butyl 3-(4-Methoxyphenyl)-7-methyl-7H-benzo[c]carbazole-6carboxylate (5h). Yellow solid (63.8 mg, 73% yield), mp 121−123 °C. Rf = 0.33 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 8.78 (d, J = 8.8 Hz, 1H), 8.55 (d, J = 8.0 Hz, 1H), 8.28 (s, 1H), 8.12 (s, 1H), 7.92 (d, J = 8.8 Hz, 1H), 7.66 (d, J = 8.8 Hz, 2H), 7.55−7.49 (m, 2H), 7.38 (t, J = 7.2 Hz, 1H), 7.01 (d, J = 8.8 Hz, 2H), 4.48 (t, J = 6.6 Hz, 2H), 3.93 (s, 3H), 3.84 (s, 3H), 1.89−1.82 (m, 2H), 1.59−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 159.1, 141.3, 135.6, 135.4, 133.3, 130.2, 129.8, 128.1, 127.9, 127.8, 126.8, 124.8, 123.4, 122.9, 121.9, 120.2, 118.2, 117.1, 114.3, 109.7, 65.5, 55.3, 33.3, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C29H28NO3 [M + H]+, 438.2064; found, 438.2064. 6-Butyl 3-Ethyl-7-methyl-7H-benzo[c]carbazole-3,6-dicarboxylate (5i). Light yellow solid (54.8 mg, 68% yield), mp 105−107 °C. Rf = 0.37 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.82 (d, J = 8.8 Hz, 1H), 8.78 (s, 1H), 8.59 (d, J = 8.0 Hz, 1H), 8.36 (s, 1H), 8.34 (d, J = 8.8 Hz, 1H), 7.63−7.55 (m, 2H), 7.44 (t, J = 7.4 Hz, 1H), 4.52−4.45 (m, 4H), 3.99 (s, 3H), 1.91−1.84 (m, 2H), 1.61−1.52 (m, 2H), 1.48 (t, J = 7.0 Hz, 3H), 1.04 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 166.7, 141.4, 141.4, 136.6, 133.3, 132.8, 131.1, 128.2, 126.5, 125.2, 123.0, 122.9, 122.0, 120.8, 118.8, 117.2, 110.0, 65.7, 61.0, 33.4, 30.8, 19.3, 14.4, 13.8. HRMS (m/z): calcd for C25H26NO4 [M + H]+, 404.1856; found, 404.1860. Butyl 4,7-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (5j) and Butyl 2,7-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (5j′). White solid mixture (43.5 mg, 63% yield, 5i/5j′ = 5:1), mp 105− 107 °C. Rf = 0.45 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.72 (d, J = 8.4 Hz, 0.2 H), 8.60 (d, J = 8.0 Hz, 1.2H), 8.58 (s, 1H), 8.47 (s, 0.2H), 8.25 (s, 1H), 7.91 (d, J = 8.4 Hz, 1H), 7.66−7.64 (m, 0.2H), 7.59−7.51 (m, 2.4H), 7.43−7.39 (m, 1.2H), 7.34−7.30 (m, 1.2H), 4.52−4.46 (m, 2.4H), 3.97−3.96 (m, 3.6H), 2.82 (s, 0.2H), 2.67 (s, 3H), 1.89−1.82 (m, 2.4H), 1.59−1.51 (m, 2.4H), 1.04−1.00 (m, 3.6H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.0, 141.3, 138.9, 136.3, 135.8, 131.5, 130.1, 129.8, 128.4, 126.1, 125.6, 124.8, 124.6, 123.1, 122.4, 122.1, 121.9, 121.4, 120.2, 120.1, 117.0, 116.7, 109.7, 65.4, 33.4, 30.8, 22.5, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1802. Butyl 7-Ethyl-7H-benzo[c]carbazole-6-carboxylate (6a). Light yellow solid (51.1 mg, 74% yield), mp 48−50 °C. Rf = 0.38 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.83 (d, J = 8.4 Hz, 1H), 8.62 (d, J = 8.0 Hz, 1H), 8.22 (s, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.74 (t, J = 7.6 Hz, 1H), 7.61 (d, J = 8.4 Hz, 1H), 7.54−7.46 (m, 2H), 7.40 (t, J = 7.4 Hz, 1H), 4.59 (q, J = 7.2 Hz, 2H), 4.49 (t, J = 6.8 Hz, 2H), 1.90−1.83 (m, 2H), 1.59−1.50 (m, 2H), 1.40 (t, J = 7.0 Hz, 3H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.4, 140.2, 133.9, 131.2, 129.8, 129.7, 128.5, 127.4, 124.7, 123.4, 123.4, 123.0, 122.1, 120.3, 118.5, 117.5, 109.9, 65.6, 40.0, 30.8, 19.3, 14.2, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1802. Butyl 7-Allyl-7H-benzo[c]carbazole-6-carboxylate (6b). Colorless liquid (45.0 mg, 63% yield). Rf = 0.39 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.85 (d, J = 8.8 Hz, 1H), 8.63 (d, J = 8.0 Hz, 1H), 8.27 (s, 1H), 8.03 (d, J = 8.4 Hz, 1H), 7.76 (t, J = 7.6 Hz, 1H), 7.60 (d, J = 8.4 Hz, 1H), 7.54−7.48 (m, 2H), 7.42 (t, J = 7.6 Hz, 1H), 5.99−5.89 (m, 1H), 5.22 (d, J = 4.8 Hz, 2H), 5.12 (d, J = 10.4 Hz, 1H), 4.93 (d, J = 17.2 Hz, 1H), 4.45 (t, J = 6.8 Hz, 2H), 1.88−1.81 (m, 2H), 1.60−1.49 (m, 2H), 1.02 (t, J = 7.2 Hz, 3H).

benzocarbazoles, while a different amount of DDQ was used in the dehydrogenation step, as was arylcarbazoles 8. Butyl 7-Methyl-7-H-benzo[c]carbazole-6-carboxylate (5a). White solid (50.3 mg, 76% yield), mp 104−106 °C. Rf = 0.48 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.83 (d, J = 8.4 Hz, 1H), 8.61 (d, J = 8.0 Hz, 1H), 8.29 (s, 1H), 8.04 (d, J = 8.0 Hz, 1H), 7.77 (t, J = 7.8 Hz, 1H), 7.61 (d, J = 8.4 Hz, 1H), 7.57−7.48 (m, 2H), 7.42 (t, J = 7.4 Hz, 1H), 4.50 (t, J = 6.8 Hz, 2H), 3.99 (s, 3H), 1.90−1.83 (m, 2H), 1.60−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 168.0, 141.3, 135.4, 131.1, 130.0, 129.9, 128.6, 127.4, 124.7, 123.4, 123.0, 122.9, 122.0, 120.2, 118.0, 117.2, 109.8, 65.5, 33.3, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H22NO2 [M + H]+, 332.1645; found, 332.1646. Butyl 3,7-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (5b). White solid (49.0 mg, 71% yield), mp 95−97 °C. Rf = 0.49 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.72 (d, J = 8.4 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.22 (s, 1H), 7.81 (s, 1H), 7.61−7.58 (m, 2H), 7.53 (t, J = 8.0 Hz, 1H), 7.40 (t, J = 7.4 Hz, 1H), 4.49 (t, J = 6.8 Hz, 2H), 3.97 (s, 3H), 2.57 (s, 3H), 1.89− 1.82 (m, 2H), 1.59−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 141.4, 135.2, 132.9, 130.8, 129.6, 129.3, 129.0, 127.8, 124.7, 123.0, 122.9, 122.0, 120.1, 117.9, 117.3, 109.7, 65.4, 33.3, 30.8, 21.4, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1804. Butyl 3-Ethyl-7-methyl-7H-benzo[c]carbazole-6-carboxylate (5c). White solid (54.9 mg, 68% yield), mp 54−56 °C. Rf = 0.52 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.74 (d, J = 8.8 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.24 (s, 1H), 7.82 (s, 1H), 7.64− 7.51 (m, 3H), 7.39 (t, J = 7.6 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.97 (s, 3H), 2.87 (q, J = 7.6 Hz, 2H), 1.89−1.82 (m, 2H), 1.58−1.50 (m, 2H), 1.37 (t, J = 7.6 Hz, 3H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 141.3, 139.2, 135.2, 129.8, 129.5, 127.8, 127.7, 124.7, 123.0, 123.0, 121.9, 120.1, 117.9, 117.3, 109.7, 65.4, 33.3, 30.8, 28.8, 19.3, 15.6, 13.8. HRMS m/z: calcd for C24H26NO2 [M + H]+, 360.1958; found, 360.1957. Butyl 7-Methyl-3-propyl-7H-benzo[c]carbazole-6-carboxylate (5d). Colorless liquid (52.2 mg, 70% yield). Rf = 0.49 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.74 (d, J = 8.4 Hz, 1H), 8.59 (d, J = 8.0 Hz, 1H), 8.25 (s, 1H), 7.81 (s, 1H), 7.63− 7.52 (m, 3H), 7.40 (t, J = 7.6 Hz, 1H), 4.49 (t, J = 6.8 Hz, 2H), 3.98 (s, 3H), 2.81 (t, J = 7.6 Hz, 2H), 1.90−1.73 (m, 4H), 1.59−1.50 (m, 2H), 1.05−0.99 (m, 6H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 141.3, 137.7, 135.2, 130.2, 129.8, 129.5, 128.5, 127.7, 124.7, 123.0, 122.9, 121.9, 120.1, 117.8, 117.2, 109.7, 65.4, 37.9, 33.4, 30.8, 24.5, 19.3, 13.9, 13.8. HRMS (m/z): calcd for C25H28NO2 [M + H]+, 374.2115; found, 374.2121. Butyl 3-(tert-Butyl)-7-methyl-7H-benzo[c]carbazole-6-carboxylate (5e). White solid (57.3 mg, 74% yield), mp 106−108 °C. Rf = 0.51 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.77 (d, J = 8.8 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.29 (s, 1H), 7.97 (s, 1H), 7.86 (d, J = 8.8 Hz, 1H), 7.60−7.51 (m, 2H), 7.40 (t, J = 7.4 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.98 (s, 3H), 1.90−1.83 (m, 2H), 1.60−1.52 (m, 2H), 1.47 (s, 9H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 146.0, 141.4, 135.4, 130.3, 129.3, 127.5, 127.4, 125.0, 124.6, 123.0, 122.8, 121.9, 120.1, 117.8, 117.1, 109.7, 65.4, 34.7, 33.4, 31.3, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C26H30NO2 [M + H]+, 388.2271; found, 388.2271. Butyl 7-Methyl-3-(tert-pentyl)-7H-benzo[c]carbazole-6-carboxylate (5f). Light yellow solid (58.5 mg, 73% yield), mp 81−83 °C. Rf = 0.47 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.76 (d, J = 8.8 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.29 (s, 1H), 7.91 (s, 1H), 7.79 (d, J = 8.8 Hz, 1H), 7.59−7.50 (m, 2H), 7.39 (t, J = 7.4 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.97 (s, 3H), 1.90−1.76 (m, 4H), 1.58−1.50 (m, 2H), 1.43 (s, 6H), 1.03 (t, J = 7.4 Hz, 3H), 0.71 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 144.3, 141.4, 135.3, 130.3, 129.2, 127.8, 127.4, 126.2, 124.6, 123.0, 122.8, 121.9, 120.1, 117.7, 117.1, 109.7, 65.4, 37.9, 36.7, 33.4, 30.8, 28.5, 19.3, 13.8, 9.2. HRMS (m/z): calcd for C27H32NO2 [M + H]+, 402.2428; found, 402.2430. 11186


Article

The Journal of Organic Chemistry C{1H} NMR (100 MHz, CDCl3): δ 168.1, 140.9, 134.4, 133.4, 131.2, 130.1, 129.9, 128.7, 127.5, 124.8, 123.6, 123.3, 123.0, 122.0, 120.5, 118.6, 117.7, 116.7, 110.3, 65.6, 47.6, 30.7, 19.3, 13.8. HRMS (m/z): calcd for C24H23NO2 [M + H]+, 358. 1729; found, 358. 1729. Butyl 7-Benzyl-7H-benzo[c]carbazole-6-carboxylate (6c). White solid (52.1 mg, 64% yield), mp 113−115 °C. Rf = 0.56 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 8.88 (d, J = 8.4 Hz, 1H), 8.67 (d, J = 8.0 Hz, 1H), 8.17 (s, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.77 (t, J = 7.6 Hz, 1H), 7.56−7.41 (m, 4H), 7.16−7.16 (m, 3H), 6.90−6.88 (m, 2H), 5.86 (s, 2H), 4.15 (t, J = 6.6 Hz, 2H), 1.56−1.49 (m, 2H), 1.38−1.29 (m, 2H), 0.91 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.0, 141.2, 137.4, 134.3, 131.1, 130.0, 129.8, 128.6, 128.5, 127.5, 127.1, 126.2, 124.9, 123.6, 123.2, 123.1, 122.1, 120.6, 118.9, 117.8, 110.3, 65.5, 48.5, 30.4, 19.1, 13.7. HRMS (m/z): calcd for C28H26NO2 [M + H]+, 408.1958; found, 408.1964. Butyl 7H-Benzo[c]carbazole-6-carboxylate (6d). Light yellow solid (27.6 mg, 44% yield), mp 149−151 °C. Rf = 0.34 (petroleum ether/ EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 10.34 (s, 1H), 8.79 (d, J = 8.4 Hz, 1H), 8.61 (s, 1H), 8.56 (d, J = 80 Hz, 1H), 8.09 (d, J = 8.0 Hz, 1H), 7.79 (t, J = 7.7 Hz, 1H), 7.65 (d, J = 8.0 Hz, 1H), 7.50 (t, J = 7.6 Hz, 2H), 7.40 (t, J = 7.8 Hz, 1H), 4.50 (t, J = 6.6 Hz, 2H), 1.93−1.86 (m, 2H), 1.63−1.54 (m, 2H), 1.05 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.4, 138.5, 136.1, 132.2, 130.8, 130.4, 129.3, 127.8, 124.8, 123.4, 123.1, 123.1, 122.0, 120.3, 116.5, 113.8, 111.6, 65.1, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C21H20NO2 [M + H]+, 318.1489; found, 318.1481. Butyl 7,8-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (6e). Light yellow solid (42.8 mg, 62% yield), mp 109−111 °C. Rf = 0.55 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.80 (d, J = 8.4 Hz, 1H), 8.44 (d, J = 7.6 Hz, 1H), 8.33 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.75 (t, J = 7.8 Hz, 1H), 7.48 (t, J = 7.6 Hz, 1H), 7.31−7.25 (m, 2H), 4.49 (t, J = 6.8 Hz, 2H), 4.03 (s, 3H), 2.89 (s, 3H), 1.90−1.83 (m, 2H), 1.59−150 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.0, 138.2, 131.1, 130.5, 130.1, 128.7, 128.1, 127.9, 124.6, 123.5, 123.0, 121.9, 120.8, 119.9, 117.9, 117.9, 65.4, 37.7, 30.8, 20.7, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1806. Butyl 7,9-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (6f). White solid (41.4 mg, 60% yield), mp 110−112 °C. Rf = 0.46 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.78 (d, J = 8.4 Hz, 1H), 8.45 (d, J = 8.0 Hz, 1H), 8.24 (s, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.73 (t, J = 7.6 Hz, 1H), 7.47 (t, J = 7.6 Hz, 1H), 7.37 (s, 1H), 7.22 (d, J = 8.0 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.94 (s, 3H), 2.61 (s, 3H), 1.89−1.82 (m, 2H), 1.59−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 141.8, 135.4, 135.0, 131.0, 129.8, 129.4, 128.4, 127.5, 123.3, 123.1, 121.9, 121.6, 120.8, 118.0, 117.4, 109.9, 65.5, 33.2, 30.8, 22.2, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1804. Butyl 9-Fluoro-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6g). White solid (49.5 mg, 71% yield), mp 87−89 °C. Rf = 0.50 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.74 (d, J = 8.4 Hz, 1H), 8.52−8.48 (m, 1H), 8.26 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.50 (t, J = 7.6 Hz, 1H), 7.26 (s, 1H), 7.14 (t, J = 8.2 Hz, 1H), 4.49 (t, J = 6.6 Hz, 2H), 3.93 (s, 3H), 1.90−1.83 (m, 2H), 1.58−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.8, 158.0 (d, J = 233.9 Hz), 137.8, 136.5, 131.1, 130.8, 130.0, 129.0, 127.4, 123.6, 123.1, 122.6, 118.1, 116.8, 112.7 (d, J = 25.5 Hz), 110.4 (d, J = 9.4 Hz), 107.5 (d, J = 24.6 Hz), 65.6, 33.6, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H21FNO2 [M + H]+, 350.1551; found, 350.1554. Butyl 9-Chloro-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6h). White solid (46.7 mg, 64% yield), mp 88−90 °C. Rf = 0.39 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.68 (d, J = 8.0 Hz, 1H), 8.44−8.41 (m, 1H), 8.27 (s, 1H), 8.01 (d, J = 8.0 Hz, 1H), 7.74 (t, J = 7.6 Hz, 1H), 7.53 (s, 1H), 7.49 (t, J = 7.6 Hz, 1H), 7.33 (d, J = 8.8 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.91 (s, 3H), 1.90−1.82 (m, 2H), 1.59−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.7, 141.9, 135.9, 130.8, 130.6, 130.4, 130.0, 128.8, 127.6, 123.8, 122.8, 122.7, 121.5, 120.7, 13

118.0, 116.9, 109.9, 65.6, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H21ClNO2 [M + H]+, 366.1255; found, 366.1254. 6-Butyl 9-Methyl-7-methyl-7H-benzo[c]carbazole-6,9-dicarboxylate (6i). White solid (31.1 mg, 40% yield), mp 129−131 °C. Rf = 0.22 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.76 (d, J = 8.4 Hz, 1H), 8.56 (d, J = 8.4 Hz, 1H), 8.30 (s, 1H), 8.29 (s, 1H), 8.07−8.01 (m, 2H), 7.77 (t, J = 7.4 Hz, 1H), 7.51 (t, J = 7.4 Hz, 1H), 4.50 (t, J = 6.6 Hz, 2H), 4.01 (s, 3H), 4.01 (s, 3H), 1.90− 1.83 (m, 2H), 1.60−1.51 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.7, 167.6, 140.6, 137.1, 131.6, 131.2, 130.0, 129.1, 127.5, 126.4, 125.9, 123.9, 122.9, 121.5, 121.2, 118.1, 116.7, 111.7, 65.6, 52.2, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C24H24NO4 [M + H]+, 390.1700; found, 390.1702. Butyl 7,10-Dimethyl-7H-benzo[c]carbazole-6-carboxylate (6j). White solid (42.1 mg, 61% yield), mp 118−120 °C. Rf = 0.45 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.82 (d, J = 8.4 Hz, 1H), 8.39 (s, 1H), 8.26 (s, 1H), 8.02 (d, J = 8.4 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.49−7.46 (m, 2H), 7.36 (d, J = 8.4 Hz, 1H), 4.48 (t, J = 6.8 Hz, 2H), 3.95 (s, 3H), 2.64 (s, 3H), 1.89− 1.82 (m, 2H), 1.59−1.50 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.1, 139.7, 135.6, 131.3, 129.9, 129.8, 129.5, 128.5, 127.4, 126.2, 123.3, 123.2, 123.0, 121.9, 118.0, 117.0, 109.5, 65.5, 33.3, 30.8, 21.7, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO2 [M + H]+, 346.1802; found, 346.1803. Butyl 10-Fluoro-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6k). White solid (48.2 mg, 69% yield), mp 109−111 °C. Rf = 0.40 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.67 (d, J = 8.4 Hz, 1H), 8.30 (s, 1H), 8.24 (d, J = 8.0 Hz, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.78 (t, J = 7.6 Hz, 1H), 7.52−7.49 (m, 2H), 7.31−7.29 (m, 1H), 4.49 (t, J = 6.6 Hz, 2H), 3.97 (s, 3H), 1.90−1.83 (m, 2H), 1.60−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 161.3 (d, J = 240.7 Hz), 142.1 (d, J = 11.7 Hz), 136.0, 130.7, 130.0, 129.7, 128.8, 127.6, 123.7, 122.9 (d, J = 10.2 Hz), 122.8, 119.5, 118.0, 117.1, 108.6 (d, J = 23.9 Hz), 96.5 (d, J = 26.2 Hz), 65.6, 33.6, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H21FNO2 [M + H]+, 350.1551; found, 350.1553. Butyl 10-Chloro-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6l). White solid (51.1 mg, 70% yield), mp 106−108 °C. Rf = 0.41 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.63−8.61 (m, 1H), 8.47 (s, 1H), 8.25 (s, 1H), 7.99 (d, J = 8.0 Hz, 1H), 7.74 (t, J = 8.2 Hz, 1H), 7.50−7.44 (m, 3H), 4.48 (t, J = 6.8 Hz, 2H), 3.90 (s, 3H), 1.90−1.83 (m, 2H), 1.59−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.7, 139.6, 136.1, 130.9, 130.8, 130.0, 128.9, 127.5, 125.7, 124.8, 123.8, 123.7, 122.7, 121.4, 118.0, 116.4, 110.7, 65.6, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H21ClNO2 [M + H]+, 366.1255; found, 366.1255. Butyl 10-Bromo-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6m). White solid (60.5 mg, 74% yield), mp 108−110 °C. Rf = 0.40 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.71−8.69 (m, 2H), 8.30 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.78 (t, J = 7.6 Hz, 1H), 7.61 (d, J = 8.8 Hz, 1H), 7.50 (t, J = 7.4 Hz, 1H), 7.46 (d, J = 8.8 Hz, 1H), 4.49 (t, J = 6.8 Hz, 2H), 3.95 (s, 3H), 1.90−1.83 (m, 2H), 1.60−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 139.8, 135.8, 130.8, 129.9, 128.9, 127.4, 127.3, 124.4, 123.7, 122.7, 117.9, 116.2, 113.2, 111.0, 65.6, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C22H21BrNO2 [M + H]+, 410.0750; found, 410.0751. Butyl 10-Methoxy-7-methyl-7H-benzo[c]carbazole-6-carboxylate (6n). White solid (45.5 mg, 63% yield), mp 105−107 °C. Rf = 0.38 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 8.73 (d, J = 8.4 Hz, 1H), 8.26 (s, 1H), 8.05−8.02 (m, 2H), 7.76 (t, J = 7.6 Hz, 1H), 7.51−7.46 (m, 2H), 7.21−7.19 (m, 1H), 4.49 (t, J = 6.8 Hz, 2H), 4.03 (s, 3H), 3.95 (s, 3H), 1.90−1.82 (m, 2H), 1.59−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.0, 154.4, 136.6, 136.0, 131.3, 130.1, 130.0, 128.6, 127.3, 125.4, 123.3, 122.7, 118.1, 116.9, 113.9, 110.4, 105.2, 65.5, 56.3, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C23H24NO3 [M + H]+, 362.1751; found, 362.1754. Ethyl 7-Methyl-7H-benzo[c]carbazole-6-carboxylate (7a). White solid (42.0 mg, 71% yield), mp 126−128 °C. Rf = 0.27 (petroleum 11187


Article

The Journal of Organic Chemistry ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 8.80 (d, J = 8.4 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.28 (s, 1H), 8.02 (d, J = 8.0 Hz, 1H), 7.74 (t, J = 7.0 Hz, 1H), 7.58−7.46 (m, 3H), 7.40 (t, J = 8.0 Hz, 1H), 4.54 (q, J = 7.1 Hz, 2H), 3.96 (s, 3H), 1.50 (t, J = 7.0 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.9, 141.3, 135.5, 131.2, 130.1, 129.9, 128.6, 127.5, 124.8, 123.4, 123.0, 122.0, 120.3, 118.0, 117.2, 109.8, 61.6, 33.3, 14.4. HRMS (m/z): calcd for C20H18NO2 [M + H]+, 304.1332; found, 304.1335. Hexyl 7-Methyl-7H-benzo[c]carbazole-6-carboxylate (7b). White solid (43.8 mg, 61% yield), mp 103−105 °C. Rf = 0.33 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.81 (d, J = 8.4 Hz, 1H), 8.59 (d, J = 8.0 Hz, 1H), 8.28 (s, 1H), 8.02 (d, J = 8.1 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.59−7.46 (m, 3H), 7.40 (t, J = 7.4 Hz, 1H), 4.47 (t, J = 6.8 Hz, 2H), 3.97 (s, 3H), 1.90−1.83 (m, 2H), 1.54− 1.47 (m, 2H), 1.42−1.34 (m, 4H), 0.92 (t, J = 7.0 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.0, 141.3, 135.5, 131.2, 130.1, 129.9, 128.6, 127.5, 124.8, 123.4, 123.0, 123.0, 122.0, 120.2, 118.0, 117.2, 109.8, 65.8, 33.3, 31.5, 28.7, 25.7, 22.6, 14.0. HRMS (m/z): calcd for C24H26NO2 [M + H]+, 360.1958; found, 360.1961. Benzyl 7-Methyl-7H-benzo[c]carbazole-6-carboxylate (7c). White solid (48.2 mg, 66% yield), mp 106−108 °C. Rf = 0.23 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.81 (d, J = 8.4 Hz, 1H), 8.59 (d, J = 8.0 Hz, 1H), 8.32 (s, 1H), 8.01 (d, J = 8.4 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.57−7.51 (m, 4H), 7.49−7.36 (m, 5H), 5.53 (s, 2H), 3.89 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 141.3, 135.6, 135.5, 131.3, 130.3, 130.0, 128.8, 128.7, 128.5, 128.5, 127.4, 124.8, 123.5, 123.0, 123.0, 122.0, 120.3, 117.6, 117.3, 109.8, 67.3, 33.4. HRMS (m/z): calcd for C25H20NO2 [M + H]+, 366.1489; found, 366.1491. Cyclohexyl 7-Methyl-7H-benzo[c]carbazole-6-carboxylate (7d). Light yellow solid (44.3 mg, 62% yield), mp 140−142 °C. Rf = 0.37 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.81 (d, J = 8.4 Hz, 1H), 8.60 (d, J = 8.0 Hz, 1H), 8.25 (s, 1H), 8.03 (d, J = 8.1 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.60−7.46 (m, 3H), 7.40 (t, J = 7.4 Hz, 1H), 5.21−5.15 (m, 1H), 3.98 (s, 3H), 2.16−2.11 (m, 2H), 1.91−1.83 (m, 2H), 1.73−1.61 (m, 3H), 1.54−1.45 (m, 2H), 1.40−1.31 (m, 1H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.5, 141.3, 135.4, 131.1, 129.9, 128.5, 127.5, 124.7, 123.4, 123.0, 122.0, 120.2, 118.6, 117.2, 109.7, 74.3, 33.4, 31.8, 25.4, 24.0. HRMS (m/z): calcd for C24H24NO2 [M + H]+, 358.1802; found, 358.1804. tert-Butyl 7-Methyl-7H-benzo[c]carbazole-6-carboxylate (7e). White solid (16.6 mg, 36% yield, mp 118−120 °C). Rf = 0.40 (7e, petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.82 (d, J = 8.4 Hz, 1H), 8.61 (d, J = 8.0 Hz, 1H), 8.18 (s, 1H), 8.03 (d, J = 8.4 Hz, 1H), 7.75 (t, J = 7.0 Hz, 1H), 7.59−7.47 (m, 3H), 7.41 (t, J = 7.4 Hz, 1H), 4.01 (s, 3H), 1.73 (s, 9H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.5, 141.2, 135.4, 131.0, 129.8, 129.4, 128.4, 127.6, 124.7, 123.4, 123.1, 123.0, 122.0, 120.2, 119.9, 117.1, 109.7, 82.2, 33.3, 28.3. HRMS (m/z): calcd for C22H22NO2 [M + H]+, 332.1645; found, 332.1647. 7-Methyl-7H-benzo[c]carbazole (7f).7f CAS: 29103-83-1. White solid (22.2 mg, 48% yield), mp 118−120 °C. Rf = 0.48 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.79 (d, J = 8.4 Hz, 1H), 8.59 (d, J = 8.0 Hz, 1H), 8.01 (d, J = 7.6 Hz, 1H), 7.90 (d, J = 8.8 Hz, 1H), 7.70 (t, J = 7.6 Hz, 1H), 7.64 (d, J = 8.8 Hz, 1H), 7.56−7.44 (m, 3H), 7.39 (t, J = 7.3 Hz, 1H), 3.97 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 139.9, 138.4, 129.9, 129.2, 128.8, 127.2, 126.8, 124.0, 123.4, 123.1, 122.7, 122.0, 119.7, 114.8, 110.5, 109.1, 29.3. 7-Methyl-7H-benzo[c]carbazole-6-carbonitrile (7g). Light yellow solid (25.6 mg, 50% yield), mp 173−175 °C. Rf = 0.58 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.77 (d, J = 8.8 Hz, 1H), 8.56 (d, J = 8.0 Hz, 1H), 8.25 (s, 1H), 7.98 (d, J = 8.0 Hz, 1H), 7.80 (t, J = 7.8 Hz, 1H), 7.59 (d, J = 4.0 Hz, 2H), 7.53 (t, J = 7.6 Hz, 1H), 7.46−7.41 (m, 1H), 4.32 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 140.5, 135.1, 134.8, 131.5, 129.9, 129.6, 127.3, 125.5, 124.1, 123.2, 122.3, 122.2, 120.8, 118.6, 117.0, 109.6, 95.3, 30.8. HRMS (m/ z): calcd for C18H13N2 [M + H]+, 257.1073; found, 257.1072. Dimethyl 7-Methyl-7H-benzo[c]carbazole-5,6-dicarboxylate (7h). Yellow solid (31.9 mg, 46% yield), mp 162−164 °C. Rf = 0.38

(petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.84 (d, J = 8.4 Hz, 1H), 8.58 (d, J = 8.0 Hz, 1H), 8.23 (d, J = 8.4 Hz, 1H), 7.75 (t, J = 7.6 Hz, 1H), 7.55−7.51 (m, 3H), 7.41−7.37 (m, 1H), 4.05 (s, 3H), 4.05 (s, 3H), 3.87 (s, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.7, 168.3, 141.6, 133.2, 130.3, 128.7, 128.3, 126.8, 125.7, 124.6, 124.4, 123.4, 122.5, 122.3, 120.6, 118.7, 118.2, 109.7, 52.9, 52.8, 31.8. HRMS (m/z): calcd for C21H18NO4 [M + H]+, 348.1230; found, 348.1232. Butyl 4-([1,1′-Biphenyl]-4-yl)-9-methyl-9H-carbazole-1-carboxylate (8a).13c White solid (69.3 mg, 80% yield), mp 125−127 °C. Rf = 0.43 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.91 (d, J = 8.0 Hz, 1H), 7.78−7.72 (m, 4H), 7.65 (d, J = 8.4 Hz, 2H), 7.51−7.44 (m, 5H), 7.39 (t, J = 7.4 Hz, 1H), 7.14 (d, J = 8.0 Hz, 1H), 7.02−6.98 (m, 1H), 4.45 (t, J = 6.8 Hz, 2H), 3.92 (s, 3H), 1.87−1.80 (m, 2H), 1.58−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.9, 142.7, 140.9, 140.7, 140.6, 139.6, 129.4, 128.9, 127.9, 127.5, 127.2, 127.1, 127.1, 126.2, 122.6, 122.3, 122.1, 120.1, 119.4, 114.6, 109.1, 65.2, 33.6, 30.8, 19.3, 13.8. Butyl 4-(4-Methoxyphenyl)-9-methyl-9H-carbazole-1-carboxylate (8b).13c Colorless liquid (37.9 mg, 49% yield). Rf = 0.46 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.87 (d, J = 7.6 Hz, 1H), 7.49 (d, J = 8.8 Hz, 2H), 7.44−7.42 (m, 3H), 7.08−7.05 (m, 3H), 7.03−6.99 (m, 1H), 4.44 (t, J = 6.8 Hz, 2H), 3.92 (s, 3H), 3.91 (s, 3H), 1.87−1.79 (m, 2H), 1.58−1.49 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 159.4, 142.7, 141.2, 139.6, 132.9, 130.1, 127.9, 126.1, 122.7, 122.2, 122.2, 120.2, 119.3, 114.2, 113.9, 109.1, 65.1, 55.3, 33.6, 30.8, 19.3, 13.8. Butyl 9-Methyl-4-(4-nitrophenyl)-9H-carbazole-1-carboxylate (8c).13c Yellow liquid (60.3 mg, 75% yield). Rf = 0.49 (petroleum ether/EtOAc = 10:1). 1H NMR (400 MHz, CDCl3): δ 8.38 (d, J = 8.8 Hz, 2H), 7.89 (d, J = 7.6 Hz, 1H), 7.73 (d, J = 8.8 Hz, 2H), 7.47 (d, J = 3.6 Hz, 2H), 7.25 (d, J = 8.0 Hz, 1H), 7.06 (d, J = 7.6 Hz, 1H), 7.04−7.00 (m, 1H), 4.46 (t, J = 6.6 Hz, 2H), 3.92 (s, 3H), 1.88−1.81 (m, 2H), 1.59−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 147.6, 147.4, 142.7, 139.3, 138.3, 130.0, 127.7, 126.7, 123.8, 122.1, 121.7, 121.4, 119.7, 119.7, 115.8, 109.5, 65.4, 33.5, 30.8, 19.3, 13.8. Butyl 4-(4-Cyanophenyl)-9-methyl-9H-carbazole-1-carboxylate (8d).13c White solid (58.8 mg, 77% yield), mp 105−107 °C. Rf = 0.50 (petroleum ether/EtOAc = 5:1). 1H NMR (400 MHz, CDCl3): δ 7.88 (d, J = 7.6 Hz, 1H), 7.81 (d, J = 8.4 Hz, 2H), 7.67 (d, J = 8.4 Hz, 2H), 7.46 (d, J = 4.0 Hz, 2H), 7.23 (d, J = 7.6 Hz, 1H), 7.04−7.00 (m, 2H), 4.46 (t, J = 6.8 Hz, 2H), 3.91 (s, 3H), 1.87−1.80 (m, 2H), 1.54− 1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 145.4, 142.7, 139.3, 138.7, 132.3, 129.8, 127.7, 126.6, 122.1, 121.7, 121.4, 119.7, 119.6, 118.8, 115.6, 111.8, 109.4, 65.3, 33.5, 30.8, 19.3, 13.7. Butyl 9-Methyl-4-(4-(methylsulfonyl)phenyl)-9H-carbazole-1-carboxylate (8e).13c Pale yellow liquid (70.5 mg, 81% yield). Rf = 0.30 (petroleum ether/EtOAc = 5:1). 1H NMR (400 MHz, CDCl3): δ 8.11 (d, J = 8.4 Hz, 2H), 7.89 (d, J = 7.6 Hz, 1H), 7.79 (d, J = 8.4 Hz, 2H), 7.47 (d, J = 3.6 Hz, 2H), 7.26 (d, J = 8.0 Hz, 1H), 7.07−7.00 (m, 2H), 4.46 (t, J = 6.8 Hz, 2H), 3.92 (s, 3H), 3.19 (s, 3H), 1.88−1.81 (m, 2H), 1.58−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.6, 146.4, 142.7, 140.0, 139.3, 138.6, 130.1, 127.7, 127.6, 126.6, 122.2, 121.8, 121.4, 119.8, 119.7, 115.6, 109.4, 65.3, 44.6, 33.5, 30.8, 19.3, 13.7. Butyl 4-(4-Chlorophenyl)-9-methyl-9H-carbazole-1-carboxylate (8f).13c Colorless liquid (54.7 mg, 70% yield). Rf = 0.41 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.87 (d, J = 7.6 Hz, 1H), 7.52−7.48 (m, 4H), 7.45 (d, J = 3.6 Hz, 2H), 7.35 (d, J = 8.0 Hz, 1H), 7.06−7.00 (m, 2H), 4.45 (t, J = 6.8 Hz, 2H), 3.91 (s, 3H), 1.87−1.80 (m, 2H), 1.58−1.49 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.7, 139.8, 139.4, 139.0, 133.9, 130.3, 128.8, 127.8, 126.3, 122.5, 122.0, 121.8, 120.0, 119.5, 114.8, 109.2, 65.2, 33.5, 30.8, 19.3, 13.8. Butyl 4-(4-Bromophenyl)-9-methyl-9H-carbazole-1-carboxylate (8g).13c Colorless liquid (63.5 mg, 73% yield). Rf = 0.42 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.87 (d, J = 11188


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0.30 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 8.99 (s, 1H), 8.74 (d, J = 8.8 Hz, 1H), 8.55 (d, J = 8.0 Hz, 1H), 8.49 (d, J = 8.8 Hz, 1H), 8.01 (s, 1H), 7.82 (d, J = 8.8 Hz, 1H), 7.72 (d, J = 8.8 Hz, 1H), 7.56 (d, J = 4.0 Hz, 2H), 7.42−7.38 (m, 1H), 4.54 (t, J = 7.0 Hz, 2H), 3.95 (s, 3H), 1.95−1.87 (m, 2H), 1.63−1.54 (m, 2H), 1.06 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.0, 141.9, 136.6, 131.7, 130.7, 130.1, 130.0, 129.8, 128.4, 125.4, 124.3, 123.7, 123.4, 122.7, 122.3, 122.3, 120.3, 119.4, 119.0, 116.7, 109.8, 65.6, 33.4, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C26H23BrNO2 [M + H]+, 460.0907; found, 460.0908. Butyl 10-Fluoro-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9d). Yellow solid (35.1 mg, 44% yield), mp 107−109 °C. Rf = 0.35 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 9.11 (s, 1H), 8.66 (d, J = 8.4 Hz, 1H), 8.57 (d, J = 8.8 Hz, 1H), 8.21 (d, J = 10.0 Hz, 1H), 7.98 (d, J = 8.8 Hz, 1H), 7.92 (d, J = 7.6 Hz, 1H), 7.69 (t, J = 7.6 Hz, 1H), 7.58 (t, J = 7.4 Hz, 1H), 7.44−7.41 (m, 1H), 7.29−7.24 m, 1H), 4.53 (t, J = 6.8 Hz, 2H), 3.92 (s, 3H), 1.95− 1.87 (m, 2H), 1.64−1.54 (m, 2H), 1.06 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 157.8 (d, J = 233.9 Hz), 138.3, 137.5, 131.1, 130.4, 130.1, 130.0, 128.8, 127.2, 125.7, 124.7, 122.9 (d, J = 9.6 Hz), 122.6, 122.4, 121.6, 118.4, 116.4, 113.0 (d, J = 25.3 Hz), 110.1 (d, J = 9.3 Hz), 107.9 (d, J = 24.8 Hz), 65.5, 33.6, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C26H23FNO2 [M + H]+, 400.1707; found, 400.1712. Butyl 10-Chloro-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9e). Yellow solid (34.0 mg, 41% yield), mp 156−158 °C. Rf = 0.36 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 9.11 (s, 1H), 8.66 (d, J = 8.4 Hz, 1H), 8.59 (d, J = 9.2 Hz, 1H), 8.51 (s, 1H), 7.99 (d, J = 9.2 Hz, 1H), 7.94 (d, J = 7.6 Hz, 1H), 7.70 (t, J = 7.2 Hz, 1H), 7.59 (t, J = 7.4 Hz, 1H), 7.47−7.40 (m, 2H), 4.54 (t, J = 6.8 Hz, 2H), 3.92 (s, 3H), 1.95−1.89 (m, 2H), 1.64−1.55 (m, 2H), 1.07 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 140.2, 137.1, 131.1, 130.5, 130.1, 130.1, 128.8, 127.3, 125.8, 125.6, 125.2, 124.8, 123.8, 122.9, 122.4, 121.8, 121.7, 118.0, 116.4, 110.5, 65.6, 33.6, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C26H23ClNO2 [M + H]+, 416.1412; found, 416.1411. Butyl 10-Bromo-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9f). Yellow solid (36.7 mg, 40% yield), mp 176−178 °C. Rf = 0.37 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 9.05 (s, 1H), 8.63−8.59 (m, 2H), 8.53−8.50 (m, 1H), 7.96−7.90 (m, 2H), 7.68 (t, J = 7.6 Hz, 1H), 7.60−7.53 (m, 2H), 7.32−7.29 (m, 1H), 4.53 (t, J = 6.8 Hz, 2H), 3.87 (s, 3H), 1.95−1.88 (m, 2H), 1.64−1.55 (m, 2H), 1.07 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 140.4, 136.9, 131.0, 130.4, 130.1, 130.0, 128.8, 127.8, 127.2, 125.8, 124.8, 124.7, 124.3, 122.8, 122.4, 121.7, 117.8, 116.2, 113.1, 110.9, 65.6, 33.5, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C26H23BrNO2 [M + H]+, 460.0907; found, 460.0906. Butyl 10-Fluoro-3-methoxy-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9g). Yellow solid (38.6 mg, 45% yield), mp 157−159 °C. Rf = 0.33 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 9.00 (s, 1H), 8.45−8.41 (m, 1H), 8.23− 8.19 (m, 1H), 7.98 (s, 1H), 7.94−7.90 (m, 1H), 7.85−7.82 (m, 1H), 7.44−7.41 (m, 1H), 7.28−7.21 (m, 2H), 4.53 (t, J = 6.8 Hz, 2H), 4.04 (s, 3H), 3.92 (s, 3H), 1.94−1.87 (m, 2H), 1.65−1.56 (m, 2H), 1.06 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 158.9, 157.8 (d, J = 233.7 Hz), 138.2, 137.5, 132.6, 130.6, 130.2, 129.7, 125.2, 124.9, 123.0 (d, J = 9.5 Hz), 122.0, 119.2, 118.4, 116.0, 115.9, 112.9 (d, J = 25.7 Hz), 110.1 (d, J = 8.9 Hz), 107.9 (d, J = 24.8 Hz), 103.6, 65.5, 55.4, 33.6, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C27H25FNO3 [M + H]+, 430.1813; found, 430.1813. Butyl 10-Bromo-3-methoxy-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9h). Yellow solid (39.1 mg, 40% yield), mp 182−184 °C. Rf = 0.32 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 8.97 (s, 1H), 8.62 (s, 1H), 8.40 (d, J = 8.8 Hz, 1H), 7.95 (s, 1H), 7.90 (d, J = 8.8 Hz, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.56 (d, J = 8.8 Hz, 1H), 7.34 (d, J = 8.4 Hz, 1H), 7.22 (d, J = 8.8 Hz, 1H), 4.54 (t, J = 6.6 Hz, 2H), 4.04 (s, 3H), 3.90 (s, 3H), 1.95− 1.88 (m, 2H), 1.66−1.58 (m, 2H), 1.07 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 159.0, 140.4, 137.0, 132.5, 130.5, 130.2, 129.8, 127.7, 125.3, 125.0, 124.8, 124.5, 122.3, 119.3, 117.8,

8.7 Hz, 1H), 7.66 (d, J = 8.4 Hz, 2H), 7.45−7.43 (m, 4H), 7.36 (d, J = 8.0 Hz, 1H), 7.05−7.00 (m, 2H), 4.45 (t, J = 6.6 Hz, 2H), 3.91 (s, 3H), 1.87−1.80 (m, 2H), 1.58−1.48 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.7, 139.8, 139.5, 139.4, 131.7, 130.7, 127.8, 126.4, 122.4, 122.1, 122.0, 121.8, 119.9, 119.5, 114.9, 109.2, 65.2, 33.5, 30.8, 19.3, 13.8. Butyl 4-(3-Bromophenyl)-9-methyl-9H-carbazole-1-carboxylate (8h).13c Colorless liquid (66.1 mg, 76% yield). Rf = 0.41 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.87 (d, J = 7.6 Hz, 1H), 7.72 (s, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.51−7.32 (m, 5H), 7.07−7.01 (m, 2H), 4.45 (t, J = 6.8 Hz, 2H), 3.91 (s, 3H), 1.87− 1.80 (m, 2H), 1.58−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.7, 142.6, 139.4, 139.4, 131.9, 131.0, 130.0, 127.8, 127.7, 126.4, 122.5, 122.4, 122.0, 121.7, 119.9, 119.6, 115.0, 109.2, 65.2, 33.5, 30.8, 19.3, 13.8. Butyl 4-(2-Chlorophenyl)-9-methyl-9H-carbazole-1-carboxylate (8i).13c Colorless liquid (32.1 mg, 41% yield). Rf = 0.36 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.92 (d, J = 7.6 Hz, 1H), 7.60 (d, J = 7.6 Hz, 1H), 7.49−7.41 (m, 5H), 7.09 (d, J = 8.0 Hz, 1H), 7.01−6.97 (m, 1H), 6.93 (d, J = 8.0 Hz, 1H), 4.45 (t, J = 6.8 Hz, 2H), 3.93 (s, 3H), 1.87−1.80 (m, 2H), 1.58−1.50 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.6, 139.2, 139.2, 137.8, 133.4, 130.9, 129.7, 129.4, 127.7, 127.0, 126.3, 123.2, 122.0, 121.6, 119.8, 119.7, 115.1, 109.1, 65.2, 33.5, 30.8, 19.3, 13.8. Butyl 9-Methyl-4-(naphthalen-2-yl)-9H-carbazole-1-carboxylate (8j).13c Colorless liquid (57.0 mg, 70% yield). Rf = 0.38 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 8.04 (s, 1H), 8.00−7.88 (m, 4H), 7.70 (d, J = 8.4 Hz, 1H), 7.58−7.53 (m, 2H), 7.45−7.40 (m, 2H), 7.33 (d, J = 8.0 Hz, 1H), 7.18 (d, J = 8.0 Hz, 1H), 6.93−6.89 (m, 1H), 4.46 (t, J = 6.6 Hz, 2H), 3.93 (s, 3H), 1.88−1.80 (m, 2H), 1.59−1.49 (m, 2H), 1.02 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.9, 142.8, 141.2, 139.6, 138.1, 133.4, 132.9, 128.2, 128.0, 127.9, 127.8, 127.6, 127.4, 126.4, 126.2, 126.2, 122.7, 122.3, 122.1, 120.4, 119.4, 114.6, 109.1, 65.2, 33.6, 30.9, 19.3, 13.8. Butyl 9-Methyl-4-(thiophen-2-yl)-9H-carbazole-1-carboxylate (8k).13c Yellow solid (29.0 mg, 40% yield), mp 85−87 °C. Rf = 0.46 (petroleum ether/EtOAc = 100:1). 1H NMR (400 MHz, CDCl3): δ 7.84 (d, J = 7.8 Hz, 1H), 7.59 (d, J = 8.0 Hz, 1H), 7.51−7.44 (m, 3H), 7.32−7.31 (m, 1H), 7.24−7.20 (m, 2H), 7.09−7.05 (m, 1H), 4.44 (t, J = 6.6 Hz, 2H), 3.90 (s, 3H), 1.87−1.79 (m, 2H), 1.56−1.48 (m, 2H), 1.01 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 142.7, 141.2, 139.4, 133.4, 127.5, 127.3, 127.0, 126.5, 126.1, 123.6, 122.2, 121.9, 121.4, 119.5, 115.3, 109.2, 65.2, 33.5, 30.8, 19.3, 13.8. Butyl 7-Methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9a). Yellow solid (40.4 mg, 53% yield), mp 145−147 °C. Rf = 0.24 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 9.14 (s, 1H), 8.79 (d, J = 9.2 Hz, 1H), 8.71 (d, J = 8.4 Hz, 1H), 8.62 (d, J = 8.0 Hz, 1H), 7.99 (d, J = 8.8 Hz, 1H), 7.92 (d, J = 8.0 Hz, 1H), 7.69 (t, J = 7.4 Hz, 1H), 7.60−7.52 (m, 3H), 7.42−7.38 (m, 1H), 4.53 (t, J = 6.8 Hz, 2H), 3.96 (s, 3H), 1.94−1.87 (m, 2H), 1.63−1.53 (m, 2H), 1.05 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.2, 142.0, 136.7, 131.3, 130.5, 130.3, 129.8, 128.7, 127.2, 125.6, 125.3, 124.1, 123.0, 122.8, 122.5, 122.3, 122.2, 120.2, 119.0, 116.3, 109.7, 65.5, 33.5, 30.9, 19.4, 13.8. HRMS (m/z): calcd for C26H24NO2 [M + H]+, 382.1802; found, 382.1804. Butyl 3-Methoxy-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9b). Yellow solid (41.1 mg, 50% yield), mp 142−144 °C. Rf = 0.32 (petroleum ether/EtOAc = 20:1). 1H NMR (400 MHz, CDCl3): δ 9.05 (s, 1H), 8.67−8.62 (m, 2H), 8.05 (s, 1H), 7.94 (d, J = 9.2 Hz, 1H), 7.84 (d, J = 8.8 Hz, 1H), 7.58−7.53 (m, 2H), 7.43−7.39 (m, 1H), 7.25−7.21 (m, 1H), 4.54 (t, J = 6.6 Hz, 2H), 4.05 (s, 3H), 3.98 (s, 3H), 1.93−1.86 (m, 2H), 1.64−1.55 (m, 2H), 1.05 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 168.2, 158.9, 141.9, 136.8, 132.7, 130.8, 130.2, 129.5, 125.3, 125.2, 124.3, 123.1, 122.4, 122.2, 120.2, 119.8, 118.9, 115.9, 109.7, 103.7, 65.4, 55.4, 33.5, 30.8, 19.4, 13.8. HRMS (m/z): calcd for C27H26NO3 [M + H]+, 412.1907; found, 412.1908. Butyl 2-Bromo-7-methyl-7H-naphtho[1,2-c]carbazole-6-carboxylate (9c). Yellow solid (37.6 mg, 41% yield), mp 136−138 °C. Rf = 11189



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116.1, 115.9, 113.1, 110.9, 103.6, 65.5, 55.4, 33.6, 30.9, 19.5, 13.8. HRMS (m/z): calcd for C27H25BrNO3 [M + H]+, 490.1012; found, 490.1010. Butyl 7-Methyl-10-phenyl-7H-benzo[c]carbazole-6-carboxylate (10). Yellow solid (58.6 mg, 72% yield), mp 130−132 °C. Rf = 0.42 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.85 (d, J = 8.4 Hz, 1H), 8.75 (s, 1H), 8.28 (s, 1H), 8.02 (d, J = 8.0 Hz, 1H), 7.79−7.74 (m, 4H), 7.61 (d, J = 8.4 Hz, 1H), 7.54−7.47 (m, 3H), 7.38 (t, J = 7.4 Hz, 1H), 4.49 (t, J = 6.8 Hz, 2H), 3.98 (s, 3H), 1.90−1.83 (m, 2H), 1.59−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13 C{1H} NMR (100 MHz, CDCl3): δ 167.9, 142.3, 140.8, 135.9, 133.8, 131.2, 130.3, 130.0, 128.8, 128.7, 127.6, 127.5, 126.6, 124.5, 123.5, 123.5, 123.0, 120.6, 118.1, 117.3, 110.0, 65.5, 33.4, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C28H26NO2 [M + H]+, 408.1958; found, 408.1961. Butyl 7-Methyl-10-(phenylethynyl)-7H-benzo[c]carbazole-6-carboxylate (11). Yellow solid (30.2 mg, 70% yield), mp 163−165 °C. Rf = 0.20 (petroleum ether/EtOAc = 50:1). 1H NMR (400 MHz, CDCl3): δ 8.83−8.79 (m, 2H), 8.29 (s, 1H), 8.03 (d, J = 8.0 Hz, 1H), 7.79 (t, J = 7.8 Hz, 1H), 7.71 (d, J = 8.4 Hz, 1H), 7.64 (d, J = 6.8 Hz, 2H), 7.56−7.50 (m, 2H), 7.41−7.33 (m, 3H), 4.49 (t, J = 6.8 Hz, 2H), 3.98 (s, 3H), 1.90−1.83 (m, 2H), 1.58−1.50 (m, 2H), 1.03 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (100 MHz, CDCl3): δ 167.8, 140.9, 136.0, 131.5, 131.0, 130.6, 129.9, 128.9, 128.4, 128.3, 127.9, 127.7, 125.6, 123.8, 123.8, 123.1, 122.9, 118.0, 116.9, 114.8, 109.8, 90.8, 87.9, 65.6, 33.5, 30.8, 19.3, 13.8. HRMS (m/z): calcd for C30H26NO2 [M + H]+, 432.1958; found, 432.1957. 10-Bromo-7-methyl-7H-benzo[c]carbazole-6-carboxylic acid (12). Yellow solid (137.7 mg, 78%), mp 261−263 °C. 1H NMR (400 MHz, DMSO): δ 8.81−8.79 (m, 2H), 8.35 (s, 1H), 8.18 (d, J = 7.6 Hz, 1H), 7.82−7.75 (m, 2H), 7.66 (d, J = 8.4 Hz, 1H), 7.55 (t, J = 7.6 Hz, 1H), 3.96 (s, 3H). 13C{1H} NMR (100 MHz, DMSO): δ 168.7, 139.5, 135.3, 129.9, 129.7, 129.7, 129.1, 127.3, 127.2, 123.9, 123.7, 123.7, 122.8, 119.7, 115.0, 112.8, 112.4, 33.0. HRMS (m/z): calcd for C18H13BrNO2 [M + H]+, 354.0124; found, 354.0131.

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ASSOCIATED CONTENT

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b02305. 1

H NMR and 13C NMR spectra for all products (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Fax: (+86)-731-58292251. *E-mail: [email protected]. ORCID

Huawen Huang: 0000-0001-7079-1299 Guo-Jun Deng: 0000-0003-2759-0314 Notes

The authors declare no competing financial interest.

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REFERENCES

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ACKNOWLEDGMENTS

We are grateful for the financial support from the National Natural Science Foundation of China (21572194, 21602187, and 21372187), the Collaborative Innovation Center of New Chemical Technologies for Environmental Benignity and Efficient Resource Utilization, the Hunan Provincial Innovative Foundation for Postgraduates (CX2016B260), the Scientific Research Fund of Hunan Provincial Education Department (16B251), and the Hunan Provincial Natural Science Foundation of China (2017JJ3299). 11190


Article

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Modular Synthesis of Carbazole-Based Conjugated Molecules

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