Annulative Ï-Extension of Aromatics and Hetero-Aromatics involving

Note Cite This: J. Org. Chem. 2017, 82, 13583−13593

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Synthetic Utility of Arylmethylsulfones: Annulative π‑Extension of Aromatics and Hetero-aromatics Involving Pd(0)-Catalyzed Heck Coupling Reactions Elumalai Sankar, Potharaju Raju, Jayachandran Karunakaran, and Arasambattu K. Mohanakrishnan* Department of Organic Chemistry, School of Chemistry, University of Madras Guindy Campus, Chennai 600 025, Tamil Nadu, India S Supporting Information *

ABSTRACT: A straightforward and general method for the synthesis of annulated thiophene, dibenzothiophene, and carbazoles analogues has been achieved involving alkylation of 2-bromo-1-(phenylsulfonylmethyl)arene/heteroarene with arylmethyl bromides/heteroarylmethyl bromides using tBuOK as a base in DMF, followed by Pd(0)-mediated intramolecular Heck coupling in the presence of K2CO3 in DMF at 80−140 °C. The attractive feature of this protocol is that a wide variety of π-conjugated heterocycles could be readily accessed by an appropriate choice of arylmethylsulfones and benzylic bromides.

S

ulfones display a diverse range of behavior and possess unique features that make them a highly valuable precursor for various types of synthetic transformation.1 The ability of sulfone to stabilize an adjacent carbanion has been well recognized and exploited in organic synthesis.2 For the first time, Trost and Ghadiri outlined the displacement ability of sulfone by a carbon nucleophile in the presence of AlCl3.3 Recently, the sulfone unit has been explored as a leaving group in different types of arylation as well as cross-coupling reactions.4 Synthesis of polycyclic aromatic heterocycles involving annulative π-extension5 has played a major role in accessing required materials for optical applications. In particular, polycyclic aromatic compounds have received significant interest as versatile and high performance active components in optical devices.6 The various types of synthetic protocols available for accessing phenanthrenes and its heterocyclic counter parts are outlined (Figure 1). The earliest method available for phenanthrene involves photocyclization of 1,2diarylethylenes.7 Tojo and co-workers employed this methodology for the synthesis of a wide variety of phenanthrenoids and their hetero-analogues involving photocyclization of stilbenes containing a tosyl group under oxidative condition or in the presence of base.8 Using photocyclization of tosyl stilbene as a key step, synthesis of analogues antitumor agent CC-1065 was also achieved.9 An intramolecular radical cyclization of cis-2iodostilbenes provided a rapid and predictable method for phenanthrenes in high yields.10 Syntheses of phenanthrene and their analogues are also achieved involving Pd-mediated intramolecular Heck coupling reactions of 1,2-diarylethanes, followed by dehydrogentation.11 Elongated polycyclic arenes, dinaphthoanthracenes with different carboxylic substitution patterns, were realized through Pd-mediated two-fold cyclization of 1,2-diarylethylene analogues.12 The elongated heteroarenes (fused dibenzothiophene/carbazole) are also available © 2017 American Chemical Society

Figure 1. Summary of synthetic protocols for phenanthrene analogues.

by an alternative methodology involving intramolecular cyclization of sulfinyl units.13 Multifold intramolecular Heck coupling of complex 1,2-diarylethanes containing a bromine group at one of the aryl units led to the formation of fullerenes and their precursors.14 Ray and co-workers reported a wide variety of phenanthrene and chrysene derivatives involving Pdmediated intramolecular Heck arylation of 1-hydroxy-1,2diarylethanes, followed by acid catalyzed dehydration.15 Yadav and co-workers reported the assembly of phenanthrenes and Received: July 20, 2017 Published: November 14, 2017 13583

DOI: 10.1021/acs.joc.7b01813 J. Org. Chem. 2017, 82, 13583−13593

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The Journal of Organic Chemistry

mediated coupling, followed by elimination, was also found to be successful in the presence of Cs2CO3 at 140 °C in o-DCB as well as xylenes (Table 1, entries 4 and 5). However, the use of Cs2CO3 in DMF at 140 °C was found to be detrimental (Table 1, entry 6). To our delight, the use of K2CO3 in DMF at 140 °C for 2 h furnished dithienobenzene 4a in the highest yield (Table 1, entry 7). The conditions such as K2CO3 in acetonitrile at 80 °C as well as t-BuOK in DMF at 140 °C led to the formation of 4a in negligible yields (Table 1, entries 8 and 9). To extend the scope of this Pd(OAc)2/PPh3-mediated domino reaction protocol, alkylation of sulfone 1 was performed with various benzyl bromides 2b−j using t-BuOK as a base in DMF at 0−10 °C to furnish respective aryl- as well as heteroaryl-methylated sulfones 3b−j. As expected, Pd(0)mediated intramolecular Heck coupling of the sulfones 3b−j using K2CO3 in DMF at 80−140 °C afforded annulated thiophenes 4b−j in 30−75% yields (Table 2). The Pd(0)-mediated domino reaction of arylmethylated sulfones 3b−e furnished the respective carbo-annulated thiophenes 4b−e in 60−70% yields. Among the isomeric naphthylmethylated sulfones 3c and 3d, the Pd-mediated coupling preference at the 1-position of naphthalene led to the formation of phenanthro[4,3-b]thiophene 4d in a relatively better yield than phenanthro[1,2-b]thiophene 4c. Due to the similar reasons, indolylmethylated sulfones 2g and 2h also afforded respective heterocycles 4g and 4h in better yields than benzo[b]thiophenyl counterpart 2f. The phenanthrenylmethylated sulfone 2i gave corresponding annulated heterocycle 4i in 62% yield. Finally, the bis-alkylation of 2-bromo-3-phenylsulfonylmethylthiophene 1 with 1,4-bis(bromomethyl)benzene 2j, followed by Pd(OAc)2/PPh3-mediated cyclization in the presence of K2CO3 in DMF at 80−140 °C, afforded dithienoanthracene 4j in 30% yield. It should be noted that the Pd(0)-mediated domino reaction of sulfones 3b−j was initially performed at moderate temperature (80 °C), followed by elevated temperature (140 °C) to avoid the elimination of the phenylsulfonyl unit prior to cyclization. Under identical conditions, the alkylation of 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 with arylmethyl/ heteroarylmethyl bromides using t-BuOK/DMF, followed by Pd(OAc)2/PPh3-mediated intramolecular Heck coupling of resulting sulfone 6a−f in the presence of K2CO3 in DMF at 80−140 °C, furnished annulated dibenzothiophenes 7a−f in 62−72% yields (Table 3). As observed earlier, the Pd(0)mediated domino reaction proceeded in relatively better yields with heteroarylmethylated sulfones 6c−f than arylmethylated sulfones 6a and 6b. In the case of naphthylated sulfone 6a, the Pd(0)-mediated cyclization led to the formation of an inseparable mixture of annulation products 7a and 7a′ in a 5:1 ratio (based on 1H NMR). Next, heteroaryl methylation of 2-bromophenylmethylsulfone 825 using t-BuOK as a base in DMF at 0−10 °C, followed by Pd(OAc)2/PPh3-mediated intramolecular Heck coupling of resulting sulfones, afforded corresponding annulated compounds 9a−d in 36−65% yields (Scheme 2). However, it should be noted that the alkylation of phenylmethylsulfone 8 with 1-bromomethylnaphthalene 2c, followed by Pd(0)-mediated domino reaction using K2CO3 in DMF at 140 °C, failed to produce chrysene; only a nonaromatized sulfone 9a′ was obtained in 36% yield. Under the established conditions, heteroaryl methylation of veratrylmethylsulfone 10 with 3-bromomethylthiophene 2a/3-

polycyclic heteroarenes involving Pd-mediated cyclization of corresponding 1,2-disubstituted-1,2-diaryl(heteroaryl)ethylenes.16 Oxidative cyclizations of 1,2-diarylethylenes employing FeCl3,17 MoCl5,18 MnO2,19 DDQ,20 and other oxidizing agents21 are also known. In a further continuation of our interest in annulated heterocycles,22 we report herein our results of one-pot synthesis of hetero-analogues of phenanthrenes involving Pd-mediated cyclization of easily accessible 1-phenylsulfonyl-1,2-diaryl(heteroaryl)ethanes. The reaction of 2-bromo-1-(phenylsulfonylmethyl)thiophene 1 with 3-bromomethylthiophene 2a23 using t-BuOK in DMF at 0−10 °C, followed by workup, furnished 2-bromo-3-(1(phenylsulfonyl)-2-(thiophen-3-yl)ethyl)thiophene 3a in 85% yield. It should be noted that the alkylation of 1 with 2a was studied at room temperature using different solvents (THF, DMF, DMSO) and bases (K2CO3, NaH, t-BuOK) to afford the alkylated sulfone 3a in 20−55% yields. Purposely, the alkylation was performed at low temperature to minimize the elimination of the phenylsulfonyl unit. As expected, a subsequent Pd(0)mediated intramolecular Heck coupling of alkylated sulfone 3a using K2CO3 as a base in DMF at 80 °C underwent concurrent elimination of phenylsulfinic acid to furnish dithienobenzene 4a24 in 70% yield (Scheme 1). Scheme 1. Domino Reaction of 2-Bromo-3(phenylsulfonylmethyl)thiophene 1 with 3Bromomethylthiophene 2a

To enhance the yield of dithienobenzene 4a, the Pd(OAc)2/ PPh3-mediated domino reaction of alkylated sulfone 3a was explored using different conditions (Table 1). The transformation of alkylated sulfone 3a into dithienobenzene 4a was found to proceed in moderate yields in the presence of K2CO3/ Cs2CO3 at 100−110 °C (Table 1, entries 1−3). The Pd(0)Table 1. Condition Optimization for Heterocycle 4a entry

solvent

conditionsa

yield (%)b

1 2 3 4 5 6 7 8 9

toluene 1,4-dioxane 1,4-dioxane o-DCB xylenes DMF DMF CH3CN DMF

K2CO3/110 °C, 12 h K2CO3/100 °C, 10 h Cs2CO3/110 °C,10 h Cs2CO3/140 °C,12 h Cs2CO3/140 °C,10 h Cs2CO3/140 °C, 6 h K2CO3/140 oC, 2 h K2CO3/80 °C, 8 h t-BuOK/140 °C, 8 h

42 58c 55 35 50 15c 75 5d 10c

a Domino reaction of sulfone 3a (1 equiv) using Pd(OAc)2 (10 mol %), PPh3 (20 mol %), and base (2.0 equiv) at 80−140 °C. bIsolated yield of 4a by column chromatography. cA major portion of dithiophenylstilbene was detected by 1H NMR. dA major portion of starting material 3a was recovered.

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The Journal of Organic Chemistry Table 2. Synthesis of Annulated Thiophenes 4b−j

Table 3. Synthesis of Annulated Dibenzothiophene Analogues 7a−f

a

Isolated yield of annulated heterocycles 7a−f from respective alkylated sulfones 6a−f. bObtained as a 5:1 (1H NMR) mixture of 7a and 7a′.

a Isolated yield of annulated heterocycles 4b−j from respective alkylated sulfones 3b−j.

As expected, the indolylmethylations of 1-bromo-2-phenylsulfonylmethylnaphthalene 1225 with 2-bromomethylindole 2g/3-bromomethylindole 2h, followed by Pd(0)-mediated domino reaction using K2CO3 in DMF at 140 °C, afforded the corresponding naphtho[c]carbazole 13 and naphtho[a]carbazole 14 in 64% and 51% yields, respectively (Scheme 3). The structure of the representative 1-phenylsulfonyl-1,2diheteroarylethane 6e and naphtho[a]annulated carbazole 14 were confirmed through single crystal X-ray analyses (see the SI).26 Next, the reaction of 2-indolylmethylsulfone 1527 with 2bromomethylindole 16 using K2CO3 as a base in DMF afforded indolylmethylated sulfone 17 in 78% yield. As expected, an intramolecular cyclization of compound 17 using Pd(OAc)2/ PPh3 in the presence of K2CO3 in DMF at 110 °C for 4 h led to the formation of indolocarbazole 18 in 78% yield (Scheme 4).

bromomethylbenzo[b]thiophene 2f, followed by Pd(OAc)2/ PPh3-mediated intramolecular Heck coupling using K2CO3 in DMF at 140 °C, led to the formation of an inseparable mixture of annulated heterocycles 11a + 11b (∼2:3 confirmed by 1H NMR) and 11c + 11d (∼2:3 confirmed by 1H NMR). The formation of annulated heterocycles 11b and 11d containing a bromine atom can be realized through Pd-mediated veratrylation at thiophene and benzo[b]thiophene 2-positions, respectively. However, indolylmethylation of veratrylmethylsulfone 10 with isomeric 2-/3-bromomethylindoles 2g/2h, followed by Pd(0)-catalyzed domino reaction, furnished the respective benzo[c]carbazole 11e and benzo[a]carbazole 11f as exclusive products. 13585


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tion of a sulfonyl stabilized carbanion, followed by an intramolecular Heck coupling reaction as a key step. The methodology was found to be useful for procuring biologically important indolocarbazoles as well. Annulative π-extension of a wide variety of aromatic as well as heteroaromatic systems was achieved in a facile manner involving Pd(0)-mediated cyclization of easily accessible 1-phenylsulfonyl-1,2-diaryl(heteroaryl)ethanes, followed by aromatization via elimination of phenylsulfinic acid. In most of the cases, the Pd(0)-catalyzed domino reactions were found to proceed in better yields with electron rich heteroaromatic systems. By the appropriate choice of base and temperature control, the Pd(0)-catalyzed domino reaction can be fine-tuned to access a wide variety of annulated heterocycles. The structures of the representative 1-phenylsulfonyl-1,2-diaryl(heteroaryl)ethane and annulated heteroarenes were confirmed through single crystal X-ray analyses. For the first time, a wide variety of annulated heteroarenes could be easily achieved by exploiting the synthetic utility of sulfonyl stabilized carbanion.

Scheme 2. Domino Reaction of Benzylmethylsulfone 8 and Veratrylmethylsulfone 10

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EXPERIMENTAL SECTION

General Methods. All melting points were uncorrected. Solvents were dried by standard procedures. All the experiments carried out under the nitrogen atmosphere unless otherwise stated. The progression of the reaction was monitored by TLC using a hexanes/ ethyl acetate (EA) mixture. Column chromatography was carried out on Silica gel (230−400 mesh, Merck) by increasing polarity. 1H, 13C spectra were recorded in CDCl3 using TMS as an internal standard on a Bruker 300, 400, and 500 MHz spectrometer at room temperature. Chemical shift values were quoted in parts per million (ppm), and coupling constants were quoted in hertz (Hz). HRMS were recorded on a JEOL GC Mate II (EI) and Xevo G2S QTof. 2-Bromo-3-methythiophene. To a solution of 3-methylthiophene (2 g, 20.4 mmol) in DMF (10 mL) was added finely powdered NBS (3.81 g, 21.4 mmol). Then, the reaction mixture was wrapped with a black cover (to exclude light) and stirred at room temperature for 24 h. It was then poured into water (50 mL), extracted with ethyl acetate (2 × 30 mL), and dried (Na2SO4). Removal of solvent under vacuo furnished 2-bromo-3-methylthiophene as a colorless liquid (4.5 g). The crude product was used as such for the next step. 2-Bromo-3-(bromomethyl)thiophene. To a solution of crude 2bromo-3-methylthiophene (3.4 g, 19.2 mmol) in dry carbon tetrachloride (60 mL) were added AIBN (0.05 g) and finely powdered NBS (3.76 g, 21.1 mmol). The reaction mixture was refluxed for 0.5 h and cooled to room temperature. The floated succinimide was filtered off and washed with carbon tetrachloride (15 mL). The combined filtrate was concentrated in vacuo to afford 2-bromo-3-bromomethythiophene (4 g) as a colorless liquid. The crude product was used as such for the next step. 2-Bromo-3-(phenylsulfonylmethyl)thiophene (1). To a solution of 2-bromo-3-(bromomethyl)thiophene (4 g, 15.6 mmol) in DMF (40 mL) was added benzenesulfinic acid sodium salt (2.82 g, 17.2 mmol). Then, the reaction mixture was stirred at room temperature for 6 h. After completion of the reaction, it was poured into crushed ice (200 g). The solid obtained was filtered and dried. The crude product was crystallized from methanol to furnish 2-bromo3-(phenylsulfonylmethyl)thiophene 1 as a colorless solid (3.92 g, 80%); mp 78−80 °C; 1H NMR (300 MHz, CDCl3): δ 7.58−7.56 (m, 3H), 7.42−7.39 (m, 2H) 7.21 (d, J = 5.7 Hz, 1H) 6.98 (d, J = 5.7 Hz, 1H) 4.29 (s, 2H, CH2) ppm. 13C NMR (75 MHz, CDCl3): δ 137.6, 134.0, 129.2, 129.1, 128.6, 128.3, 126.4, 115.5, 56.4 ppm. DEPT-135 (75 MHz, CDCl3): δ 134.0, 129.2, 129.1, 128.6, 126.4, 56.4 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C11H10BrO2S2 316.9306; Found 316.9298. 2-Bromo-3-(1-(phenylsulfonyl)-2-(thiophen-3-yl)ethyl)thiophene (3a). To a solution of 2-bromo-3-(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) in DMF (20 mL) were added t-BuOK

Scheme 3. Domino Reaction of 1-Bromo-2phenylsulfonylmethylnaphthalene 12

Scheme 4. Synthesis of Indolocarbazoles 18, 19, and 22

After considerable experimentations, the intramolecular cyclization of compound 17 using Pd(OAc)2/PPh3 in the presence of K2CO3 as base in DMF at 140 °C in a sealed tube afforded parent indolocarbazole 19 in 75% yield. The isomeric 3indolylmethylsulfone 20, upon indolylmethylation with 2bromomethylindole 16 using K2CO3 in DMF, furnished the required precursor 21 of indolocarbazole. As expected, compound 21 upon reaction with Pd(OAc)2/PPh3 in a sealed tube underwent intramolecular coupling, followed by aromatization and cleavage of the phenylsulfonyl unit, to afford indolocarbazole 22 in 68% yield. In summary, we have developed an efficient and straightforward protocol for the syntheses of annulated thiophene, dibenzothiophene, and carbazole derivatives involving benzyla13586


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as a colorless solid (0.28 g, 60%); mp 146−148 °C; 1H NMR (300 MHz, CDCl3): δ 8.66 (d, J = 8.4 Hz, 1H), 8.57 (d, J = 8.7 Hz, 1H), 8.01 (d, J = 9.0 Hz, 1H), 7.95 (d, J = 8.7 Hz, 1H), 7.86 (d, J = 8.1 Hz, 1H), 7.81 (d, J = 9.0 Hz, 1H), 7.61 (d, J = 7.6 Hz, 1H), 7.55−7.44 (m, 3H) ppm. 13C NMR (75 MHz, CDCl3): δ 138.6, 138.0, 131.8, 130.9, 128.9, 127.8, 127.2, 127.0, 126.9, 126.2, 125.8, 124.9, 123.1, 122.9, 122.2, 119.8 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C16H11S 235.0581; Found 235.0599. Phenanthro[4,3-b]thiophene (4d). Alkylation of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 2bromomethylnaphthalene 2d (0.54 g, 2.43 mmol) using t-BuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-bromo-3-(2-(naphthalen-2-yl)-1-(phenylsulfonyl)ethyl)thiophene 3d as a colorless liquid (0.88 g, 87%). To a solution of alkylated sulfone 3d (0.88 g, 1.93 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.10 g, 0.38 mmol), and K2CO3 (0.53 g, 3.84 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for an additional 1 h. After completion of the reaction, the usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, 100% Hexane), furnished phenanthro[4,3-b]thiophene 4d as a colorless solid (0.32 g, 70%); mp 92−94 °C; 1H NMR (300 MHz, CDCl3): δ 9.18 (d, J = 7.4 Hz, 1H), 7.97−7.95 (m, 2H), 7.93−7.94 (m, 4H), 7.63 (d, J = 7.2 Hz, 1H), 7.60 (d, J = 9.0 Hz, 1H), 7.57 (m, 1H) ppm. 13C NMR (75 MHz, CDCl3): δ 139.3, 134.8, 132.8, 130.6, 129.4, 128.9, 127.7, 126.8, 126.6, 126.3, 126.2, 126.1, 126.0, 125.9, 124.5, 123.8 ppm. DEPT-135: δ 129.1, 127.9, 126.9, 126.8, 126.3, 126.3, 126.1, 126.0, 124.7, 123.0 ppm. HRMS (ESI-TOF) m/z: [M + H]+Calcd for C16H11S 235.0581; Found 235.0587. 6,9-Dimethoxynaphtho[1,2-b]thiophene (4e). Alkylation of 2bromo-3-(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 2-(bromomethyl)-1,4-dimethoxybenzene 2e (0.56 g, 2.43 mmol) using t-BuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-bromo-3-(2-(2,5-dimethoxyphenyl)-1-(phenylsulfonyl)ethyl)thiophene 3e as a colorless solid (0.91 g, 88%). To a solution of alkylated sulfone 3e (0.91 g, 1.94 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.10 g, 0.38 mmol), and K2CO3 (0.54 g, 3.88 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for an additional 5 h. After completion of the reaction, the usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:27), furnished 6,9-dimethoxynaphtho[1,2-b]thiophene 4e as a colorless solid (0.30 g, 64%); mp 118−120 °C; 1H NMR (300 MHz, CDCl3): δ 8.10 (d, J = 8.7 Hz, 1H), 7.62 (d, J = 9.0 Hz, 1H), 7.52 (d, J = 5.4 Hz, 1H), 7.42 (d, J = 5.4 Hz, 1H), 6.83 (d, J = 8.7 Hz, 1H), 6.74 (d, J = 8.4 Hz, 1H) 4.01 (s, 3H, OCH3), 3.92 (s, 3H, OCH3) ppm. 13C NMR (75 MHz, CDCl3): δ 149.0, 148.0, 136.8, 132.0, 126.5, 122.6, 122.4, 121.1, 121.1, 117.6, 104.0, 102.6, 55.0, 54.9 ppm. DEPT-135: δ 126.5, 122.4, 121.2, 117.6, 104.0, 102.6, 55.0, 54.9 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C14H12O2S 245.0636; Found 245.0615. Preparation of Compound (4f). Alkylation of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 3(bromomethyl)benzo[b]thiophene 2f (0.7 g, 2.43 mmol) using tBuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromothiophen-3-yl)-2-(phenylsulfonyl)ethylbenzo[b]thiophene 3f as a colorless solid (0.94 g, 92%). To a solution of alkylated sulfone 3f (0.94 g, 2.02 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.05 g, 0.20 mmol), PPh3 (0.10 g, 0.40 mmol), and K2CO3 (0.56 g, 4.04 mmol). The reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, 100% Hexane), furnished 4f as a colorless solid (0.32 g, 65%); mp 112−114 °C; 1H NMR (300 MHz, CDCl3): δ 8.11−8.08 (m, 1H), 8.03 (d, J = 8.4 Hz, 1H), 7.84−7.79 (m, 2H), 7.40 (m, 4H) ppm. 13C NMR (75 MHz, CDCl3): δ 138.9, 138.7, 136.3, 133.6, 133.2, 132.5, 126.4, 125.5,

(0.37 g 3.32 mmol) and 3-bromomethylthiophene 2a (0.43 g, 2.43 mmol). Then, the reaction mixture was stirred at room temperature for 15 min. After completion of the reaction, it was poured into crushed ice (100 g), extracted with ethyl acetate (3 × 20 mL), and dried (Na2SO4). Removal of solvent under vacuo furnished 2-bromo3-(1-(phenylsulfonyl)-2-(thiophen-3-yl)ethyl)thiophene 3a as a colorless liquid (0.86 g, 95%); 1H NMR (300 MHz, CDCl3): δ 7.71− 7.51(m, 3H), 7.51−7.33 (m, 2H), 7.33−7.21 (m, 2H), 6.73 (s, 1H), 6.73−6.63 (m, 2H), 4.52−4.49 (m, 1H), 3.80−3.75 (m, 1H), 3.39− 3.31 (m, 1H) ppm. 13C NMR (75 MHz, CDCl3): δ 137.2, 136.0, 133.9, 132.4, 128.9, 128.8, 127.8, 126.8, 126.5, 125.8, 122.3, 116.2, 65.7, 28.0 ppm. HRMS (ESI-TOF) m/z: [M − SO2Ph]+ Calcd for C10H8BrS2 270.9251; Found 270.9247. 3-(2-(2-Bromophenyl)-2-(phenylsulfonyl)ethyl)thiophene (3b). To a solution of 2-bromo-3-(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) in DMF (20 mL) were added t-BuOK (0.37 g, 3.32 mmol) and benzyl bromide 2b (0.42 g, 2.43 mmol). Then, the reaction mixture was stirred at room temperature for 15 min. The usual workup adopting the procedure similar to that of 3a furnished 2bromo-3-(2-phenyl-2-(phenylsulfonyl)ethyl)thiophene 3b as a colorless liquid (0.85 g, 95%); 1H NMR (300 MHz, CDCl3): δ 7.69 (d, J = 7.2 Hz, 2H), 7.61−7.56 (m, 1H), 7.47−7.42 (m, 3H), 7.22−7.20 (m, 1H), 7.06−7.01 (m, 3H), 6.94−6.93 (m, 1H), 6.89−6.86 (m, 1H), 4.57 (dd, J1 = 11.7 Hz, J2 = 3.0 Hz, 1H), 3.91−3.86 (m, 1H), 3.85− 3.32 (m, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ 137.3, 136.1, 133.8, 132.1, 128.8, 128.8, 128.7, 128.5, 128.5, 126.9, 126.9, 126.4, 116.1, 66.4, 33.3 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C18H16BrO2S2 406.9775; Found 406.9770. Preparation of Benzodithiophene (4a).24 To a solution of 2bromo-3-(1-(phenylsulfonyl)-2-(thiophen-3-yl)ethyl)thiophene 3a (0.82 g, 1.98 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.1 g, 0.39 mmol), and K2CO3 (0.55 g, 3.96 mmol). Then, the reaction mixture was refluxed for 2 h. After that, the reaction mixture was filtered through a Celite bed and washed with ethyl acetate (2 × 10 mL). The combined organic layer was washed with water (3 × 20 mL) and dried (Na2SO4). Removal of solvent, followed by column chromatographic purification (Silica gel, 100% Hexane), afforded benzodithiophene 4a as a pale yellow liquid (0.28 g, 75%); 1H NMR (400 MHz, DMSO-d6): δ 7.85 (m, 1H), 7.72 (d, J = 5.2 Hz, 1H), 7.57 (d, J = 5.2 Hz, 1H), ppm. 13C NMR (100 MHz, DMSO-d6): δ 137.0, 132.6, 125.3, 125.2, 120.6 ppm. HRMS (ESITOF) m/z: [M]+ Calcd for C10H6S2 189.9911; Found 189.9904. Naphtho[1,2-b]thiophene (4b). To a solution of crude 2-bromo3-(2-phenyl-1-(phenylsulfonyl)ethyl)thiophene 3b (0.83 g, 2.03 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.05 g, 0.20 mmol), PPh3 (0.10 g, 0.40 mmol), and K2CO3 (0.56 g, 4.06 mmol). Then, the reaction mixture was refluxed for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, 100% Hexane), afforded naphtho[1,2-b]thiophene 4b as a colorless liquid (0.25 g, 68%); 1H NMR (300 MHz, CDCl3): δ 8.22 (d, J = 8.1 Hz, 1H), 7.95 (d, J = 7.5 Hz, 1H), 7.85 (d, J = 8.7 Hz, 1H), 7.79 (d, J = 8.4 Hz, 1H), 7.69−7.64 (m, 1H), 7.62−7.60 (m, 1H), 7.58−7.54 (m, 1H), 7.53−7.51 (m, 1H) ppm. 13C NMR (75 MHz, CDCl3): δ 137.4, 130.9, 128.9, 128.8, 127.2, 126.7, 125.7, 125.4, 125.2, 125.1, 123.7, 122.1 ppm. HRMS (ESITOF) m/z: [M]+ Calcd for C12H8S 184.0347; Found 184.0330. Phenanthro[1,2-b]thiophene (4c). Alkylation of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 1bromomethylnaphthalene 2c (0.54 g, 2.43 mmol) using t-BuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-bromo-3-(2-(naphthalen-1-yl)-1-(phenylsulfonyl)ethyl)thiophene 3c as a colorless solid (0.92 g, 91%). To a solution of alkylated sulfone 3c (0.92 g, 2.01 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.05 g, 0.20 mmol), PPh3 (0.10 g, 0.40 mmol), and K2CO3 (0.56 g, 4.02 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for an additional 1 h. After completion of the reaction, the usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, 100% Hexane), furnished phenanthro[1,2-b]thiophene 4c 13587


Note

The Journal of Organic Chemistry 124.9, 124.8, 123.0, 121.7, 120.5, 118.1 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C14H8S2 240.0067; Found 240.0071. 6-(Phenylsulfonyl)-6H-thieno[3,2-c]carbazole (4g). Alkylation of 2-bromo-3-(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 2-bromomethyl-1-phenylsulfonylindole 2g (0.85 g, 2.43 mmol) using t-BuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-(2-(2-bromothiophen-3-yl)-2-(phenylsulfonyl)ethyl)1-(phenylsulfonyl)-1H-indole 3g as a colorless solid (1.16 g, 90%). To a solution of alkylated sulfone 3g (1.16 g, 1.97 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.10 g, 0.39 mmol), and K2CO3 (0.55 g, 3.94 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:27), furnished 6-(phenylsulfonyl)-6Hthieno[3,2-c]carbazole 4g as a colorless solid (0.50 g, 70%); mp 144− 146 °C; 1H NMR (300 MHz, CDCl3): δ 8.38 (d, J = 8.7 Hz, 2H), 7.56 (d, J = 7.2 Hz, 1H), 7.66 (d, J = 9.0 Hz, 1H), 7.81 (d, J = 7.8 Hz, 2H), 7.50−7.40 (m, 4H), 7.32 (t, J = 7.5 Hz, 1H), 7.19 (t, J = 7.2 Hz, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 135.9, 135.4, 134.6, 133.3, 131.4, 129.7, 126.6, 124.6, 124.0, 123.2, 122.8, 122.0, 121.6, 120.3, 118.9, 117.9, 112.8, 110.0 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H14NO2S2 364.0466; Found 364.0439. 3-(2-(2-Bromothiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1(phenylsulfonyl)-1H-indole (3h). To a solution of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) in DMF (20 mL) at 5−10 °C were added t-BuOK (0.37 g, 3.32 mmol) and 3bromomethylindole 2h (0.85 g, 2.43 mmol). Then, the reaction mixture was stirred at the same temperature for 15 min. The usual workup adopting the procedure similar to that of 3a furnished 3-(2-(2bromothiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)1H-indole 3h as a colorless solid (1.15 g, 89%); mp 160−162 °C; 1H NMR (300 MHz, CDCl3): δ 7.83 (d, J = 7.2 Hz, 1H), 7.57−7.43 (m, 5H), 7.43−7.35 (m, 4H), 7.32−7.28 (m, 2H), 7.25−7.13 (m, 4H), 6.98 (s, 1H), 4.57 (dd, J1 = 11.7 Hz, J2 = 3.0 Hz, 1H), 3.85−3.80 (m, 1H), 3.41−3.32 (m, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ 137.9, 137.0, 134.9, 134.0, 133.7, 132.3, 130.2, 129.2, 128.9, 128.8, 126.8, 126.6, 126.5, 125.0, 123.9, 123.4, 119.0, 117.3, 116.2, 133.8, 64.3, 23.3 ppm. HRMS (ESI-TOF) m/z: [M − C12H10O4S2]+ Calcd for C14H10BrNS 302.9717; Found 302.9694. [M − C12H10O4S2]2+ Calcd for C14H10BrNS 304.9697; Found 304.9691. 10-(Phenylsulfonyl)-10H-thieno[2,3-a]carbazole (4h). To a solution of 3-(2-(2-bromothiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1(phenylsulfonyl)-1H-indole 3h (0.96 g, 1.53 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.03 g, 0.15 mmol), PPh3 (0.08 g, 0.30 mmol), and K2CO3 (0.42 g, 3.06 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:27), furnished 10-(phenylsulfonyl)-10Hthieno[2,3-a]carbazole 4h as a colorless solid (0.46 g, 75%); mp 184− 186 °C; 1H NMR (300 MHz, CDCl3): δ 8.35 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 7.8 Hz, 1H), 7.77−7.75 (m, 2H), 7.56 (d, J = 7.8 Hz, 2H), 7.49−7.47 (m, 1H), 7.42−7.37 (m, 2H), 7.32−7.26 (m, 2H), 7.13− 7.07 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 141.5, 138.7, 137.1, 134.0, 133.6, 128.9, 127.9, 127.7, 127.3, 126.9, 126.8, 124.7, 124.4, 121.3, 119.5, 116.8, 116.3 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H14NO2S2 364.0466; Found: 364.0440. Triphenyleno[1,2-b]thiophene (4i). Alkylation of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (0.7 g, 2.21 mmol) with 9(chloromethyl)phenanthrene 2i (0.54 g, 2.43 mmol) using t-BuOK (0.37 g, 3.32 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-bromo-3-(2-(phenanthren-9-yl)-1-(phenylsulfonyl)ethyl)thiophene 3i as a colorless solid (1.04 g, 93%). To a solution of alkylated sulfone 3i (1.04 g, 2.04 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.05 g, 0.20 mmol), PPh3 (0.11 g, 0.40 mmol), and K2CO3 (0.56 g, 4.08 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for an additional 1 h. The usual workup adopting the procedure similar to that of 4a furnished triphenyleno[1,2-b]thiophene 4i by column chromatographic purifi-

cation (Silica gel, 100% Hexane) as a colorless solid (0.36 g, 62%); mp 124−126 °C; 1H NMR (300 MHz, CDCl3): δ 9.211 (d, J = 8.4 Hz, 1H), 8.70 (d, J = 8.4 Hz, 1H), 8.63−8.60 (m, 3H), 8.01 (d, J = 8.7 Hz, 1H), 7.79−7.74 (m, 1H), 7.70−7.65 (m, 1H), 7.62−7.58 (m, 3H), 7.51−7.50 (m, 1H) ppm. 13C NMR (75 MHz, CDCl3): δ 140.0, 135.6, 130.5, 130.3, 129.4, 129.4, 128.0, 127.4, 127.1, 127.1, 126.9, 126.6, 126.5, 126.3, 124.4, 124.0, 123.4, 123.3, 123.2, 120.5 ppm. DEPT-135: δ 127.4, 127.1, 127.1, 126.9, 126.6, 126.5, 124.4, 124.0, 123.4, 123.3, 123.2, 120.5 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C20H13S 285.0738; Found 285.0715. Preparation of Compound (4j). Alkylation of 2-bromo-3(phenylsulfonylmethyl)thiophene 1 (1.76 g, 5.57 mmol) with 1,4bis(bromomethyl)benzene 2j (0.7 g, 2.65 mmol) using t-BuOK (0.37 g, 3.31 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 1,4bis(2-(2-bromothiophen-3-yl)-2-(phenylsulfonyl)ethyl)benzene thiophene 3j as a colorless solid (1.52 g, 94%). To a solution of alkylated sulfone 3j (1.52 g, 2.06 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.05 g, 0.20 mmol), PPh3 (0.10 g, 0.38 mmol), and K2CO3 (0.42 g, 4.12 mmol). The reaction mixture was initially maintained at 80 °C for 6 h. It was then heated at 140 °C for 30 h. After completion of the reaction, the usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:49), furnished 4j as a yellow solid (0.18 g, 30%); mp 226−228 °C; 1H NMR (300 MHz, CDCl3): δ 8.73 (s, 2H), 7.91 (d, J = 8.7 Hz, 2H), 7.83 (d, J = 8.7 Hz, 2H), 7.56 (d, J = 5.4 Hz, 2H), 7.50 (d, J = 5.4 Hz, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 137.2, 136.8, 129.9, 127.2, 125.6, 125.4, 124.9, 122.6, 122.5 ppm. DEPT-135: δ 125.6, 125.4, 125.0, 122.6, 122.5 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C18H10S2 290.0224; Found 290.0222. 2-Bromo-3-methylbenzo[b]thiophene. To a solution of 3methylbenzo[b]thiophene (8 g, 54.0 mmol) in DMF (60 mL) was added finely powdered NBS (10.46 g, 59.5 mmol). Then, the reaction mixture was wrapped with a black cover (to exclude light) and stirred at room temperature for 24 h. It was then poured into water (50 mL), extracted with ethyl acetate (2 × 30 mL), and dried (Na2SO4). Removal of solvent under vacuo furnished 2-bromo-3-methylbenzo[b]thiophene (12.3 g) as a colorless liquid. The crude product was used as such for the next step. 2-Bromo-3-(bromomethyl)benzo[b]thiophene. To a solution of crude 2-bromo-3-methylbenzo[b]thiophene (5.21 g, 23.0 mmol) in dry carbon tetrachloride (60 mL) were added AIBN (0.05 g) and finely powdered NBS (4.50 g, 25.3 mmol). The reaction mixture was refluxed for 0.5 h. The floated succinimide was filtered off and washed with carbon tetrachloride (15 mL). The combined filtrate was concentrated in vacuo to afford 2-bromo-3-bromomethylbenzo[b]thiophene as a colorless liquid (6.2 g). The crude product was used as such for the next step. 2-Bromo-3-(phenylsulfonylmethyl)benzo[b]thiophene (5). To a solution of 2-bromo-3-(bromomethyl)benzo[b]thiophene (3.86 g, 12.6 mmol) in DMF (50 mL) was added benzenesulfinic acid sodium salt (2.66 g, 16.4 mmol). Then, the reaction mixture was stirred at room temperature for 6 h. The usual workup adopting the procedure similar to that of 1 furnished 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 as a colorless solid (3.70 g, 80%); mp 152−154 °C; 1H NMR (300 MHz, CDCl3): δ 7.76−7.75 (m, 1H), 7.73−7.65 (m, 1H), 7.63−7.60 (m, 2H), 7.56 (d, J = 8.7 Hz, 1H), 7.39−7.34 (m, 2H), 7.31−7.29 (m, 2H), 4.57 (s, 2H, CH2) ppm. 13C NMR (100 MHz, CDCl3): δ 139.3, 137.8, 137.5, 134.1, 129.2, 128.8, 125.3, 125.2, 123.4, 122.8, 121.6, 120.0, 55.6 ppm. HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C15H11BrNaO2S2 388.9282; Found 388.9275; M+Na]2+ Calcd for C15H11BrNaO2S2 390.9261; Found 390.9254. Benzo[b]phenanthro[3,4-d]thiophene (7a)28a and Anthra[2,1-d]benzo[b]thiophene (7a′).28b Alkylation of 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) with 2-bromomethylnaphthalene 2d (0.46 g, 2.10 mmol) using tBuOK (0.32 g, 2.87 mmol) in DMF (20 mL) at 5−10 °C, followed by workup adopting the procedure similar to that of 3a, furnished 2bromo-3-(2-(naphthalen-2-yl)-1-(phenylsulfonyl)ethyl)benzo[b]13588


Note


followed by column chromatographic purification (Silica gel, EtOAchexane 1:24), furnished 7d as a colorless solid (0.49 g, 70%); mp 184− 186 °C; 1H NMR (300 MHz, CDCl3): δ 8.40 (d, J = 9.0 Hz, 1H), 8.35 (d, J = 8.1 Hz, 1H), 8.14−8.07 (m, 2H), 7.96 (d, J = 7.5 Hz, 1H), 7.82−7.73 (m, 3H), 7.50−7.29 (m, 6H), 7.20 (d, J = 7.2 Hz, 1H) ppm. 13 C NMR (75 MHz, CDCl3): δ 139.1, 138.5, 137.8, 137.3, 135.0, 133.9, 132.4, 132.1, 129.1, 127.2, 126.5, 126.4, 125.6, 124.9, 124.4, 122.9, 121.6, 121.5, 120.6, 120.4, 115.2, 112.1 ppm. DEPT-135: δ 134.0, 129.1, 127.3, 126.5, 126.4, 124.9, 124.4, 122.9, 121.6, 121.5, 120.4, 115.2, 112.1 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H16NO2S2 414.0622; Found 414.0628. 3-(2-(2-Bromobenzo[b]thiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole (6e). To a solution of 2bromo-3-(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) in DMF (20 mL) at 5−10 °C were added t-BuOK (0.32 g, 2.87 mmol) and 3-bromomethylindole 2h (0.74 g, 2.10 mmol). Then, the reaction mixture was stirred at the same temperature for 15 min. After completion of the reaction, it was poured into crushed ice (100 g); the solid obtained was filtered and dried. The crude product was crystallized from methanol to furnish 3-(2-(2-bromobenzo[b]thiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole 6e as a colorless solid (1.12 g, 92%); mp184−186; 1H NMR (400 MHz, CDCl3): δ 8.85 (d, J = 8.4 Hz, 1H), 7.86 (d, J = 8.4 Hz, 1H), 7.70 (d, J = 8.0 Hz, 1H), 7.61−7.59 (m, 3H), 7.57−7.54 (m, 3H), 7.50−7.47 (m, 2H), 7.47−7.41 (m, 1H), 7.38−7.31 (m, 4H), 7.28− 7.24 (m, 1H), 7.19−7.15 (m, 1H), 6.96 (s, 1H), 5.04 (dd, J1 = 10.4 Hz, J2 = 4.4 Hz, 1H), 4.04−4.00 (m, 1H), 3.98−3.95 (m, 1H) ppm. 13C NMR (100 MHz, CDCl3): δ 139.4, 137.9, 137.4, 135.4, 134.9, 134.0, 133.7, 129.9, 129.2, 128.9, 128.6, 126.5, 125.3, 125.3, 125.0, 124.3,, 124.1, 123.4, 122.0, 121.2, 118.9, 117.5, 113.7, 66.9, 21.7 ppm. HRMS (ESI-TOF) m/z: [M − C12H10O4S2] +Calcd for C18H12BrNS 352.9874; Found 352.9824. [M − C12H10O4S2] +2 Calcd for C18H12BrNS 354.9853; Found 354.9845. Preparation of Compound (7e). To a solution of crude 3-(2-(2bromobenzo[b]thiophen-3-yl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole 6e (0.95 g, 1.50 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.03 g, 0.15 mmol), PPh3 (0.08 g, 0.30 mmol), and K2CO3 (0.41 g, 3.00 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAchexane 1:24), furnished 7e as a colorless solid (0.45 g, 72%); mp 182− 184 °C; 1H NMR (300 MHz, CDCl3): δ 8.34 (d, J = 8.1 Hz, 1H), 8.02−7.96 (m, 2H), 7.63 (d, J = 7.2 Hz, 1H), 7.53 (d, J = 7.8 Hz, 2H), 7.53 (d, J = 7.8 Hz, 2H), 7.41−7.34 (m, 3H), 7.29−7.23 (m, 1H), 7.21−7.14 (m, 1H), 7.04−7.02 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 140.3, 139.3, 136.8, 135.2, 134.1, 133.6, 128.8 (2C), 127.6, 127.4 (3C), 127.2, 126.9, 124.9, 124.5, 122.2, 121.4, 119.7, 118.8, 117.2, 116.4 ppm. DEPT-135: δ 133.6, 128.8, 127.4, 126.9, 125.0, 124.5, 122.3, 121.4, 119.7, 118.8, 117.2, 116.4 ppm. HRMS (ESITOF) m/z: [M + H]+ Calcd for C24H16NO2S2 414.0622; Found 414.0624. Preparation of Compound (7f). Alkylation of 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) with 2-(bromomethyl)benzo[b]thiophene 2k (0.48 g, 2.10 mmol) using t-BuOK (0.32 g, 2.87 mmol) in DMF (20 mL) at 5−10 °C, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(benzo[b]thiophen-2-yl)-1-(phenylsulfonyl)ethyl)-2bromobenzo[b]thiophene 6f as a colorless solid (0.84 g, 86%). To a solution of alkylated sulfone 6f (0.84 g, 1.63 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.16 mmol), PPh3 (0.08 g, 0.32 mmol), and K2CO3 (0.45 g, 3.33 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:49), furnished 7f as a colorless solid (0.31 g, 65%); mp 166−168 °C; 1H NMR (300 MHz, CDCl3): δ 8.50 (d, J = 7.5 Hz, 1H), 8.25 (d, J = 8.1 Hz, 2H), 8.02−7.94 (m, 3H), 7.66 (t, J = 7.5 Hz, 1H), 7.59−7.53 (m, 3H) ppm. 13C NMR (75 MHz, CDCl3): δ 139.8, 138.6, 138.5, 135.1, 134.9, 133.8, 133.0, 129.5, 126.4, 126.3, 124.8, 124.8, 124.0, 122.9, 122.8, 121.4, 120.0, 119.2 ppm. DEPT-135: δ 126.4, 126.3, 124.8, 124.8, 124.0, 122.9, 122.8, 121.4, 119.9, 119.2

thiophene 6a as a colorless solid (0.87 g, 90%). To a solution of alkylated sulfone 6a (0.87 g, 1.73 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.09 g, 0.35 mmol), and K2CO3 (0.48 g, 3.46 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for 5 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, 100% Hexane), furnished a mixture (5:1, based 1H NMR integration value) of benzo[b]phenanthro[3,4-d]thiophene 7a and anthra[2,1-d]benzo[b]thiophene 7a′ as a colorless solid (0.32 g, 65% two steps); mp 114−116 °C; 1H NMR (400 MHz, CDCl3): δ 9.31 (d, J = 8.4 Hz, 1H), 8.65 (s, 0.25H), 8.41 (s, 0.29H), 8.40 (d, J = 8.0 Hz, 1H), 8.30 (d, J = 9.2 Hz, 8.06− 8.04 (m, 0.34H), 8.03−8.02 (m, 0.81H), 8.01−7.99 (m, 3H), 7.94− 7.92 (m, 1H), 7.88−7.85 (m, 2H), 7.73−7.72 (m, 1H), 7.56−7.53 (m, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ 139.3, 135.0, 134.8, 133.0, 132.5, 130.0, 129.0, 128.0, 127.9, 127.4,, 126.9, 126.6, 126.4 (2C), 126.1, 126.0, 125.7, 124.8, 123.0, 122.6, 122.5, 122.3, 121.5, 120.2, 119.5 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for 7a + 7a′ C20H12S 284.0660; Found 284.0664. 1,4-Dimethoxybenzo[d]naphtho[1,2-b]thiophene (7b). Alkylation of 2-bromo-3-(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) with 2-(bromomethyl)-1,4-dimethoxybenzene 2e (0.49 g, 2.10 mmol) using t-BuOK (0.32 g, 2.87 mmol) in DMF (20 mL) at 5−10 °C, followed by workup adopting the procedure similar to that of 3a, furnished 2-bromo-3-(2-(2,5-dimethoxyphenyl)-1(phenylsulfonyl)ethyl)benzo[b]thiophene 6b as a colorless solid (0.90 g, 91%). To a solution of alkylated sulfone 6b (0.90 g, 1.75 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.09 g, 0.35 mmol), and K2CO3 (0.49 g, 3.50 mmol). The reaction mixture was initially maintained at 80 °C for 1 h. It was then heated at 140 °C for 5 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:24), furnished 1,4-dimethoxybenzo[d]naphtho[1,2-b]thiophene 7b as a colorless solid (0.31 g, 62%); mp 168−170 °C; 1H NMR (300 MHz, CDCl3): δ 8.34−8.27 (m, 3H), 8.03−8.01 (m, 1H), 7.54−7.49 (m, 2H), 6.94 (d, J = 8.4 Hz, 1H), 6.66 (d, J = 8.4 Hz, 1H), 4.14 (s, 3H, OCH3), 4.04 (s, 3H, OCH3) ppm. 13 C NMR (75 MHz, CDCl3): δ 150.1, 149.5, 141.0, 134.9, 133.6, 133.1, 125.9, 125.4, 124.0, 122.3, 121.3, 119.6, 118.9, 105.3, 104.1, 56.1, 56.0 ppm. DEPT-135: δ 125.9, 124.1, 122.3, 121.3, 119.6, 118.9, 105.3, 104.1, 56.1, 56.0 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C18H14O2S 294.0715; Found 294.0701. Preparation of Compound (7c).29 Alkylation of 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) with 3-(bromomethyl)benzo[b]thiophene 2f (0.48 g, 2.10 mmol) using tBuOK (0.32 g, 2.87 mmol) in DMF (20 mL) at 5−10 °C, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2(benzo[b]thiophen-3-yl)-1-(phenylsulfonyl)ethyl)-2-bromobenzo[b]thiophene 6c as a colorless solid (0.89 g, 91%). To a solution of alkylated sulfone 6c (0.89 g, 1.55 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.03 g, 0.15 mmol), PPh3 (0.08 g, 0.30 mmol), and K2CO3 (0.43 g, 3.10 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAchexane 1:49), furnished 7c as a colorless solid (0.34 g, 68%); mp 270− 272 °C; 1H NMR (500 MHz, CDCl3): δ 8.23−8.22 (m, 1H), 8.22− 8.21 (m, 3H), 7.93−7.92 (m, 1H), 7.92 (m,1H), 7.53−7.47 (m, 4H) ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C18H10S2 290.0224; Found 290.0211. Preparation of Compound (7d). Alkylation of 2-bromo-3(phenylsulfonylmethyl)benzo[b]thiophene 5 (0.7 g, 1.91 mmol) with 2-bromomethylindole 2g (0.74 g, 2.10 mmol) using t-BuOK (0.32 g, 2.87 mmol) in DMF (20 mL) at 5−10 °C, followed by workup adopting the procedure similar to that of 3a, furnished 2-(2(benzo[b]thiophen-3-yl)-1-(phenylsulfonyl)ethyl)-2-bromobenzo[b]thiophene 6d as a colorless solid (1.09 g, 90%). To a solution of alkylated sulfone 6d (1.09 g, 1.71 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.09 g, 0.34 mmol), and K2CO3 (0.47 g, 3.42 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, 13589


Note

The Journal of Organic Chemistry ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C18H11S2 291.0302; Found 291.0305. 6-(Phenylsulfonyl)-5,6-dihydrochrysene (9a′). Alkylation of 2bromo-3-(phenylsulfonylmethyl)benzene 8 (0.7 g, 2.25 mmol) with 1bromomethylnaphthalene 2c (0.54 g, 2.48 mmol) using t-BuOK (0.38 g, 3.38 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 1-(2(2-bromophenyl)-2-(phenylsulfonyl)ethyl)naphthalene as a colorless solid (0.91 g, 90%). To a solution of the alkylated sulfone (0.91 g, 1.82 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.18 mmol), PPh3 (0.09 g, 0.36 mmol), and K2CO3 (0.50 g, 3.64 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 12 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:12), furnished 6-(phenylsulfonyl)-5,6dihydrochrysene 9a′ as a colorless solid (0.29 g, 36% two steps); mp 192−194 °C; 1H NMR (300 MHz, CDCl3): δ 8.20 (d, J = 7.5 Hz, 1H), 8.03−8.7.97 (m, 2H), 7.89−7.86 (m, 2H), 7.80−7.78 (m, 2H), 7.67−7.59 (m, 1H), 7.57−7.52 (m, 2H), 7.43−7.37 (m, 1H), 7.21− 7.16 (m, 1H), 7.01−6.97 (m, 1H), 6.66 (d, J = 7.2 Hz, 1H), 6.28 (d, J = 7.5 Hz, 1H), 4.42 (dd, J1 = 11.3, J2 = 3.0 Hz, 1H), 4.24 (dd, J1 = 13.5, J2= 2.7 Hz, 1H), 2.93−2.89 (m, 1H) ppm. 13C NMR (75 MHz, CDCl3): δ 134.0, 133.9, 132.7, 132.3, 131.8, 131.5, 131.4, 129.5, 129.0, 128.7, 128.2, 128.0, 126.7, 126.5, 126.2, 125.9, 125.4, 125.0, 123.3, 64.0, 34.8 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H19O2S 371.1106; Found 371.1119. Benzo[d]naphtho[1,2-b]thiophene (9b). Alkylation of 2-bromo3-(phenylsulfonylmethyl)benzene 8 (0.7 g, 2.25 mmol) with 3(bromomethyl)benzo[b]thiophene 2f (0.56 g, 2.48 mmol) using tBuOK (0.38 g, 3.38 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromophenyl)-2-(phenylsulfonyl)ethyl)benzo[b]thiophene as a colorless solid (0.92 g, 90%). To a solution of the alkylated sulfone (0.92 g, 2.02 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.20 mmol), PPh3 (0.10 g, 0.40 mmol), and K2CO3 (0.56 g, 4.04 mmol). Then, the reaction mixture was heated at 80 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel; EtOAchexane 1:49), furnished benzo[d]naphtho[1,2-b]thiophene 9b as a colorless solid (0.34 g, 65% two steps); mp 180−82 °C; 1H NMR (300 MHz, CDCl3): δ 8.26−8.22 (m 2H), 8.18−8.15 (m, 1H), 8.02− 7.98 (m, 2H), 7.89 (d, J = 8.4 Hz, 1H), 7.67−7.59 (m, 2H), 7.56−7.49 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 139.1, 137.3, 136.6, 132.7, 132.4, 129.0, 128.9, 126.8, 126.3, 126.2, 125.5, 124.6, 124.5, 123.0, 121.6, 119.7 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C16H10S 234.0503; Found 234.0501. 7-(Phenylsulfonyl)-7H-benzo[c]carbazole (9c). Alkylation of 2bromo-3-(phenylsulfonylmethyl)benzene 8 (0.7 g, 2.25 mmol) with 2bromomethylindole 2g (0.86 g, 2.48 mmol) using t-BuOK (0.38 g, 3.38 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-(2(2-bromophenyl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole as a colorless solid (1.14 g, 88%). To a solution of the alkylated sulfone (1.14 g, 1.98 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.10 g, 0.38 mmol), and K2CO3 (0.55 g, 3.96 mmol). Then, the reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 3 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:19), furnished 7-(phenylsulfonyl)-7H-benzo[c]carbazole 9c as a colorless solid (0.45 g, 57% two steps); mp 160−162 °C; 1H NMR (300 MHz, CDCl3): δ 8.64 (d, J = 8.4 Hz, 1H), 8.53 (d, J = 9.3 Hz, 1H), 8.45− 8.39 (m, 2H), 7.95−7.87 (m, 2H), 7.73 (d, J = 7.8 Hz, 2H), 7.64−7.62 (m, 1H), 7.50−7.31 (m, 3H), 7.28 (d, J = 8.4 Hz, 1H), 7.23−7.18 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 138.1, 138.0, 136.6, 133.9, 131.1, 129.2, 129.1, 128.9, 128.7, 127.4, 127.2, 126.4, 126.3, 125.0, 124.4, 123.6, 122.2, 120.0, 115.4, 114.9 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C22H16NO2S 358.0902; Found 358.0906. 11-(Phenylsulfonyl)-11H-benzo[a]carbazole (9d). Alkylation of 2-bromo-3-(phenylsulfonylmethyl)benzene 8 (0.7 g, 2.25 mmol)

with 3-bromomethylindole 2h (0.86 g, 2.48 mmol) using t-BuOK (0.38 g, 3.38 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromophenyl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole as a colorless solid (1.0 g, 80%). To a solution of the alkylated sulfone (1.0 g, 1.72 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.09 g, 0.34 mmol), and K2CO3 (0.49 g, 3.54 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 3 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:24), furnished 11-(phenylsulfonyl)-11H-benzo[a]carbazole 9d as a colorless solid (0.43 g, 56% two steps); mp 140−142 °C; 1H NMR (300 MHz, CDCl3): δ 8.91 (d, J = 8.7 Hz, 1H), 8.24 (d, J = 8.1 Hz, 1H), 7.85 (d, J = 8.1 Hz, 1H), 7.73 (d, J = 8.4 Hz, 1H), 7.63 (d, J = 8.7 Hz, 1H), 7.59−7.55 (m, 2H), 7.47 (t, J = 7.2 Hz, 1H), 7.35 (t, J = 7.2 Hz, 1H), 7.24 (t, J = 7.2 Hz, 1H), 7.16−7.10 (m, 1H), 6.85−6.83 (m, 4H) ppm. 13C NMR (75 MHz, CDCl3): δ 141.7, 136.7, 134.1, 133.9, 133.3, 130.1, 128.3, 127.9, 127.8, 127.7, 127.0, 126.9, 126.7, 126.2, 126.2, 126.0, 125.8, 119.9, 119.4, 117.4 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C22H16NO2S 358.0902; Found 358.0911. 2-Bromo-4,5-dimethoxyphenyl)methanol. To a solution of 2bromo-4,5-dimethoxybenzaldehyde (3 g, 12.2 mmol) in THF (30 mL) at 0−10 °C was added NaBH4 (1.39 g, 36.7 mmol). Then, the reaction mixture was stirred at room temperature for 2 h. It was then poured into water (50 mL), extracted with DCM (3 × 30 mL), and dried (Na2SO4). Removal of solvent under vacuo furnished 2-bromo-4,5dimethoxyphenyl)methanol as a colorless liquid (3.5 g). The crude product was used as such for the next step. 1-Bromo-2-(bromomethyl)-4,5-dimethoxybenzene. To a solution of crude (2-bromo-4,5-dimethoxyphenyl)methanol (2.69 g, 10.89 mmol) in DCM (30 mL) at 0 °C was carefully added PBr3 (4.4 g, 16.33 mmol). Then, the reaction mixture was stirred 0 °C for 10 min. It was then poured into water (50 mL), extracted with DCM (3 × 30 mL), and dried (Na2SO4). Removal of solvent under vacuo furnished 1-bromo-2-(bromomethyl)-4,5-dimethoxybenzene as a colorless solid (3.5 g). The crude product was used as such for the next step. 1-Bromo-4,5-dimethoxy-2-(phenylsulfonylmethyl)benzene (10). To a solution of crude 1-bromo-2-(bromomethyl)-4,5-dimethoxybenzene (2.53 g, 8.16 mmol) in DMF (30 mL) was added benzenesulfinic acid sodium salt (1.73 g, 10.61 mmol). Then, the reaction mixture was stirred at room temperature for 6 h. The usual workup adopting the procedure similar to that of 1 furnished 1-bromo4,5-dimethoxy-2-(phenylsulfonylmethyl)benzene 10 as a colorless solid (2.21 g, 73%); mp 142−144 °C; 1H NMR (300 MHz, CDCl3): δ 7.68−7.61 (m, 3H), 7.49−7.44 (m, 2H), 6.92 (s, 1H), 6.88 (s, 1H), 4.50 (s, 2H, CH2), 3.85 (s, 3H, OCH3), 3.84 (s, 3H, OCH3) ppm. 13C NMR (100 MHz, CDCl3): δ 149.9, 148.3, 138.0, 133.9, 129.0, 129.0, 119.9, 116.4, 115.1, 114.4, 61.5, 56.1, 56.1 ppm. HRMS (ESI-TOF) m/z: [M + Na]+ Calcd for C15H15BrO4SNa 392.9772; Found 392.9765; [M + Na]2+ Calcd for C15H15BrO4SNa 394.9752; Found 394.9745. Preparation of 11a and 11b. Alkylation of 1-bromo-4,5dimethoxy-2-(phenylsulfonylmethyl)benzene 10 (0.7 g, 1.89 mmol) with 3-bromomethylthiophene 2a (0.37 g, 2.08 mmol) using t-BuOK (0.32 g, 2.83 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromophenyl)-2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole as a colorless solid (0.79 g, 90%). To a solution of the alkylated sulfone (0.79 g, 1.70 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.10 g, 0.37 mmol), and K2CO3 (0.47 g, 3.40 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:49), furnished a mixture of 11a and 11b as a brown liquid (0.28 g, 47% two steps); 1H NMR (300 MHz, CDCl3): δ 7.63 (d, J = 8.4 Hz, 1H), 7.52 (d, J = 8.7 Hz, 1H), 7.24−7.21 (m, 1.5H), 7.18−7.16 (m, 2H), 6.95 (s, 1H), 6.92−6.89 (m, 1H), 6.84 (s, 1H), 6.78−6.75 (m, 1H), 3.99 (s, 13590


Note

The Journal of Organic Chemistry 3H, OCH3), 3.94 (s, 3H, OCH3), 3.86 (s, 2H), 3.81 (s, 2H) ppm. 13C NMR (100 MHz, CDCl3): δ 149.8, 149.2, 149.0, 148.8, 140.3, 136.3, 136.3, 130.5, 128.5 126.1, 126.0, 125.2, 124.9, 124.3, 124.1, 123.9, 121.6, 121.2, 120.3, 119.6 111.3, 108.6, 107.9, 103.2, 56.1, 56.0, 56.0, 55.9 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for 11a C14H13O2S 245.0636; Found 245.0642. MS (ESI) m/z: for 11b C11H9BrOS [M − C3H2O]+ 267, [M − C3H2O]+2 269. Preparation of 11c and 11d. Alkylation of 1-bromo-4,5dimethoxy-2-(phenylsulfonylmethyl)benzene 10 (0.7 g, 1.89 mmol) with 3-(bromomethyl)benzo[b]thiophene 2f (0.47 g, 2.08 mmol) using t-BuOK (0.32 g, 2.83 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromo-4,5-dimethoxyphenyl)-2-(phenylsulfonyl)ethyl)benzo[b]thiophene as a colorless solid (0.86 g, 88%). To a solution of the alkylated sulfone (0.86 g, 1.66 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.16 mmol), PPh3 (0.08 g, 0.32 mmol), and K2CO3 (0.46 g, 3.32 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:32), furnished a mixture of 11c and 11d as a brown liquid (0.34 g, 48% two steps); 1H NMR (300 MHz, CDCl3): δ 8.07 (d, J = 7.2 Hz, 1H), 7.97−7.92 (m, 1H), 7.86−7.78 (m, 2H), 7.65−7.62 (m, 1H), 7.42 (s, 1H), 7.34−7.29 (m, 2H), 7.22 (s, 1H), 7.21−7.18 (m, 1H), 7.21−7.18 (m,1H), 7.14 (s, 1H), 7.06 (s, 1H), 7.02−6.99 (m, 1H), 6.79 (d, J = 8.4 Hz, 1H), 4.0 (s, 2H), 3.95 (s, 2H), 3.86 (s, 3H, OCH3), 3.83 (s, 3H, OCH3) ppm. MS (ESI) m/z for 11c C18H15O2S [M + H]+: 295. MS: m/z for 11d C18H13BrO2S [M+]: 371, [M+2]: 373. 2,3-Dimethoxy-7-(phenylsulfonyl)-7H-benzo[c]carbazole (11e). Alkylation of 1-bromo-4,5-dimethoxy-2-(phenylsulfonylmethyl)benzene 10 (1.0 g, 2.69 mmol) with 2-bromomethylindole 2g (1.03 g, 2.96 mmol) using t-BuOK (0.45 g, 4.03 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-(2-(2-bromo-4,5-dimethoxyphenyl)2-(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole as a colorless solid (1.58 g, 92%). To a solution of the alkylated sulfone (1.30 g, 2.03 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.20 mmol), PPh3 (0.10 g, 0.40 mmol), and K2CO3 (0.57 g, 4.08 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:19), furnished 2,3-dimethoxy-7-(phenylsulfonyl)-7H-benzo[c]carbazole 11e as a colorless solid (0.58 g, 68%); mp 160−162 °C; 1H NMR (300 MHz, CDCl3): δ 8.21 (d, J = 8.1 Hz, 1H), 7.73 (d, J = 7.75 Hz, 2H), 7.66−7.61 (m, 1H), 7.47−7.44 (m, 2H), 7.37−7.31 (m, 3H), 7.29−7.24 (m, 2H), 7.06 (s, 1H), 6.85 (s, 1H), 3.98 (s, 3H, OCH3), 3.91 (s, 3H, OCH3) ppm. 13C NMR (75 MHz, CDCl3): δ 150.0, 148.9, 139.6, 138.1, 137.5, 133.6, 131.0, 130.3, 129.0, 128.8, 126.7, 124.9, 124.2, 120.8, 119.6, 115.5, 115.3, 115.1, 109.4, 109.1, 56.3, 56.2 ppm. DEPT-135: δ 133.8, 130.9, 129.0, 126.7, 124.2, 120.8, 119.6, 115.5, 115.3, 109.4, 109.1, 56.3, 56.2 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H20NO4S 418.1113; Found 418.1115. 2,3-Dimethoxy-11-(phenylsulfonyl)-11H-benzo[a]carbazole (11f). Alkylation of 1-bromo-4,5-dimethoxy-2-(phenylsulfonylmethyl)benzene 10 (1.0 g, 2.69 mmol) with 3-bromomethylindole 2h (1.0 g, 2.69 mmol) using t-BuOK (1.0 g, 2.69 mmol) in DMF (20 mL) at 5− 10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(2-bromo-4,5-dimethoxyphenyl)-2(phenylsulfonyl)ethyl)-1-(phenylsulfonyl)-1H-indole as a colorless solid (1.51 g, 88%). To a solution of the alkylated sulfone (1.20 g, 1.88 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.19 mmol), PPh3 (0.10 g, 0.38 mmol), and K2CO3 (0.52 g, 3.78 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 2 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:19), furnished 2,3-dimethoxy11-(phenylsulfonyl)-11H-benzo[a]carbazole 11f as a colorless solid (0.57 g, 72%); mp 186−188 °C; 1H NMR (300 MHz, CDCl3): δ 8.37 (s, 1H), 8.25 (d, J = 8.1 Hz, 1H), 7.61 (d, J = 8.4 Hz, 1H), 7.56−7.50

(m, 2H), 7.38−7.33 m, 1H), 7.28−7.24 (m, 1H), 7.19−7.14 (m, 3H), 6.89−6.88 (m, 3H), 4.11 (s, 3H, OCH3), 3.99 (s, 3H, OCH3) ppm. 13 C NMR (75 MHz, CDCl3): δ 149.3, 149.2, 141.5, 136.1, 134.0, 133.2, 130.5, 130.0, 127.8, 126.8, 126.3, 126.0, 125.7, 121.9, 120.0, 119.1, 115.6, 107.0, 106.5, 56.2, 55.8 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C24H20NO4S 418.1113; Found 418.1126. 9-(Phenylsulfonyl)-9H-naphtho[2,1-c]carbazole (13). Alkylation of 1-bromo-2-(phenylsulfonylmethyl)naphthalene 12 (0.7 g, 1.89 mmol) with 2-bromomethylindole 2g (0.72 g, 2.07 mmol) using tBuOK (0.32 g, 2.83 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 2-(2-(1-bromonaphthalen-2-yl)-2-(phenylsulfonyl)ethyl)-1(phenylsulfonyl)-1H-indole as a colorless solid (1.12 g, 92%). To a solution of the alkylated sulfone (1.12 g, 1.77 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.17 mmol), PPh3 (0.09 g, 0.34 mmol), and K2CO3 (0.49 g, 3.54 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 6 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:24), furnished 9-(phenylsulfonyl)-9H-naphtho[2,1-c]carbazole 13 as a colorless solid (0.50 g, 64% two steps); mp 104−106 °C; 1H NMR (500 MHz, CDCl3): δ 8.94 (d, J = 8.0 Hz, 1H), 8.57 (d, J = 9.0 Hz, 1H), 8.52 (d, J = 8.0 Hz, 1H), 8.43 (d, J = 8.1 Hz, 1H), 7.87−7.84 (m, 2H), 7.77 (d, J = 7.5 Hz, 2H),7.73−7.68 (m, 2H), 7.55−7.53 (m, 1H), 7.48−7.43 (m, 2H), 7.35−7.34 (m, 1H), 7.27−7.22 (m, 3H) ppm. 13C NMR (125 MHz, CDCl3): δ 138.5, 137.8, 133.9, 133.1, 130.2, 130.0, 129.1, 128.3, 128.0, 127.7, 127.2, 126.9, 126.5, 126.3, 125.7, 124.5, 124.0, 123.1 123.0, 121.5, 117.4, 115.4, 115.0 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C26H18NO2S 408.1058; Found 408.1064. 13-(Phenylsulfonyl)-13H-naphtho[1,2-a]carbazole (14). Alkylation of 1-bromo-2-(phenylsulfonylmethyl)naphthalene 12 (0.7 g, 1.89 mmol) with 3-bromomethylindole 2h (0.72 g, 2.07 mm) using tBuOK (0.32 g, 2.83 mmol) in DMF (20 mL) at 5−10 °C for 15 min, followed by workup adopting the procedure similar to that of 3a, furnished 3-(2-(1-bromonaphthalen-2-yl)-2-(phenylsulfonyl)ethyl)-1(phenylsulfonyl)-1H-indole as a colorless solid (1.00 g, 82%). To a solution of the alkylated sulfone (1.0 g, 1.59 mmol) in DMF (15 mL) were added Pd(OAc)2 (0.04 g, 0.16 mmol), PPh3 (0.08 g, 0.32 mmol), and K2CO3 (0.44 g, 3.14 mmol). The reaction mixture was initially maintained at 80 °C for 2 h. It was then heated at 140 °C for 6 h. The usual workup adopting the procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:20), furnished 13-(phenylsulfonyl)-13H-naphtho[1,2-a]carbazole 14 as a colorless solid (0.48 g, 51% two steps); mp 78−80 °C; 1H NMR (300 MHz, CDCl3): δ 9.81 (d, J = 8.4 Hz, 1H), 8.25 (d, J = 8.1 Hz, 1H), 7.85−7.81 (m, 2H), 7.77−7.65 (m, 2H), 7.58 (d, J = 7.8 Hz, 2H), 7.57−7.53 (m, 2H), 7.40 (t, J = 7.6 Hz, 1H), 7.25 (t, J = 7.3 Hz, 1H), 7.12 (t, J = 7.3 Hz, 1H), 6.80 (t, J = 7.6 Hz, 2H), 6.54 (d, J = 7.8 Hz, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 142.1, 137.5, 133.1, 132.9, 132.7, 132.3, 130.9, 130.7, 130.4, 129.1, 128.2, 128.0, 127.6, 127.4, 127.1, 127.0, 127.1, 126.2, 126.2, 125.5, 120.4, 119.7, 117.7 ppm. DEPT-135: δ 133.1, 129.1, 128.2, 128.0, 127.6, 127.4, 127.1, 127.0, 126.3, 126.2, 125.5, 120.4, 119.7, 117.7 ppm. HRMS (ESI-TOF) m/z: [M + H]+ Calcd for C26H18NO2S 408.1058; Found 408.1049. 3-Bromo-1-(phenylsulfonyl)-2-(2-(phenylsulfonyl)-2-(1-(phenylsulfonyl)-1H-indol-2-yl)ethyl)-1H-indole (17). To a solution of sulfone 1527 (0.8 g, 1.94 mmol) and 2-bromomethylindole 16 (0.9 g, 2.14 mmol) in DMF (10 mL) was added K2CO3 (0.8 g, 5.83 mmol), and the reaction mixture was stirred at room temperature for 12 h. After completion of the reaction (monitored by TLC), it was then poured over crushed ice containing Conc. HCl (5 mL). The solid obtained was filtered, washed with water (2 × 20 mL), and dried. The crude product was recrystallized from methanol (5 mL) to afford indolylmethylated sulfone 17 as a colorless solid (1.15 g, 78%). 5,8-Bis(phenylsulfonyl)indolo[2,3-c]carbazole (18). To a solution of indolylmethylated sulfone 17 (200 mg, 0.26 mmol) in DMF (8 mL) were added Pd(OAc)2 (6 mg, 0.026 mmol), PPh3 (13 mg, 0.053 mmol), and K2CO3 (100 mg, 0.79 mmol), and the mixture was stirred at 110 °C for 4 h. After completion of the reaction (monitored by TLC), the usual workup adopting the procedure similar 13591


Note

The Journal of Organic Chemistry ORCID

to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:10), afforded 8-bis(phenylsulfonyl)indolo[2,3c]carbazole 18 as a colorless solid (110 mg, 78%); mp 200−202 °C; 1 H NMR (300 MHz, CDCl3): δ 8.54 (s, 2H), 8.49 (d, J = 7.8 Hz, 2H), 8.43 (d, J = 8.4 Hz, 2H), 7.70 (d, J = 8.1 Hz, 4H), 7.46 (t, J = 7.2 Hz, 2H), 7.42−7.31 (m, 4H), 7.23 (t, J = 7.5 Hz, 4H) ppm. 13C NMR (75 MHz, CDCl3): δ 138.9, 137.5, 136.0, 133.9, 129.0, 127.5, 126.4, 126.0, 124.0, 123.1, 120.9, 115.6, 114.4 ppm. DEPT-135 (75 MHz, CDCl3): δ 133.9, 129.0, 127.5, 126.4, 124.0, 123.1, 115.6, 114.4 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C30H20N2O4S2 536.0864; Found: 536.0836. 5,8-Dihydroindolo[2,3-c]carbazole (19). In a sealed tube containing a solution of indolylmethylated sulfone 17 (200 mg, 0.26 mmol) in DMF (8 mL) were added Pd(OAc)2 (6 mg, 0.026 mmol), PPh3 (13 mg, 0.053 mmol), and K2CO3 (100 mg, 0.79 mmol), and the mixture was stirred at 140 °C for 6 h. After completion of the reaction (monitored by TLC), following the workup procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:5), afforded 5,8-dihydroindolo[2,3-c]carbazole 19 as a colorless solid (50 mg, 75%); mp 280−282 °C; 1H NMR (300 MHz, CDCl3+DMSO-d6): δ 8.81 (s, 2H), 7.89 (d, J = 7.8 Hz, 2H), 6.57− 6.52 (m, 6H), 6.51−6.45 (m, 2H) ppm. 13C NMR (75 MHz, CDCl3 + DMSO-d6): δ 139.2, 134.3, 124.2, 122.6, 122.4, 118.1, 115.8, 110.6, 109.6 ppm. DEPT-135 (75 MHz, CDCl3): δ 119.3, 117.7, 113.2, 105.7, 104.8 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C18H12N2 256.1000; Found 256.0999. Indolo[3,2-a]carbazole (22). To a solution of sulfone 20 (0.8 g, 1.94 mmol) and 3-bromo-2-bromomethylindole 16 (0.9 g, 2.14 mmol) in DMF (10 mL) was added K2CO3 (0.8 g, 5.83 mmol), and the mixture was stirred at rt for 12 h. After completion of the reaction followed by workup procedure similar to that of 17, followed by crystallization from methanol, afforded indolylmethylated sulfone 21 as a colorless solid (1.18 g, 79%). In a sealed tube containing a solution of crude indolylmethylated sulfone 21 (200 mg, 0.26 mmol) in DMF (8 mL) were added Pd(OAc)2 (6 mg, 0.026 mmol), PPh3 (13 mg, 0.053 mmol), and K2CO3 (100 mg, 0.79 mmol). The reaction mixture was then stirred at 140 °C for 6 h. After completion of the reaction (monitored by TLC), following the workup procedure similar to that of 4a, followed by column chromatographic purification (Silica gel, EtOAc-hexane 1:5), afforded indolo[3,2-a]carbazole 22 as a colorless solid (46 mg, 68%); mp 278−280 °C; 1H NMR (300 MHz, CDCl3+DMSO-d6): δ 10.35 (bs, 1H), 9.95 (bs, 1H), 7.69 (d, J = 7.5 Hz, 1H), 7.14 (m, 2H), 6.74 (d, J = 7.8 Hz, 1H), 6.65 (d, J = 8.1 Hz, 1H), 6.48−6.29 (m, 5H) ppm. 13C NMR (75 MHz, CDCl3 + DMSOd6): δ 138.7, 138.1, 133.4, 123.2, 123.1, 122.5, 121.0, 120.5, 118.1, 117.9, 117.8, 117.2, 114.0, 110.3, 109.9, 106.1, 102.8 ppm. DEPT-135 (75 MHz, CDCl3 + DMSO-d6): δ 128.8, 128.1, 126.1, 123.7, 123.5, 123.4, 122.8, 115.9, 115.5, 108.4 ppm. HRMS (ESI-TOF) m/z: [M]+ Calcd for C18H12N2 256.1000; Found 256.0998.

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Arasambattu K. Mohanakrishnan: 0000-0002-3758-4578 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors graciously acknowledged the Council of Scientific and Industrial Research (CSIR) New Delhi [02(0214)/14/ EMR-II dt. 17/11/2014] for financial support. E.S and J.K. thank the Council of Scientific and Industrial Research (CSIR) New Delhi for fellowships. P.R. thanks the University Grants Commission (UGC) New Delhi for the fellowship. The authors thank the Department of Science and Technology Funds for the Improvement of Science and Technology (DSTFIST) New Delhi for NMR and HRMS facilities.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b01813. Copies of 1H and 13C NMR spectra for 1, 3a−3b, 3h, 4a−4j, 5, 6e, 7a−7f, 9a′−9d, 11a+11b/11c+11d (1H only), 11e−11f, 10, 13, 14, 18, 19, 22; X-ray crystallographic information for 6e and 14; and HRMS spectra for 4i, 4j, 7a, 7b, 7c, 14 (PDF) X-ray crystallographic information for 6e (CIF) X-ray crystallographic information for 14 (CIF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; mohan_67@hotmail. com. 13592


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