Rapid Access to Hydroxyfluoranthenes via a Domino Suzuki-Miyaura/Intramolecular Diels-Alder/Ring-Opening Reactions Sequence.

In this work, we developed an efficient method for the rapid construction of fluoranthene skeleton to access a variety of substituted hydroxyfluoranthenes. The 1-iodo-8-alkynylnaphthalene derivatives, which serve as substrates for the key fluoranthene-forming step, were prepared via selective monoalkynylative Sonogashira reactions of 1,8-diiodonaphthalene. The domino reaction sequence which involves a sequential Suzuki-Miyaura coupling, an intramolecular Diels-Alder reaction, and an aromatization-driven ring-opening isomerization has been shown to give substituted hydroxyfluoranthenes in up to 92% yield. This work demonstrates the utility of designing new domino reactions for rapid access to substituted polycyclic aromatic hydrocarbons (PAHs).

Polycyclic aromatic hydrocarbons (PAHs) represent an important class of organic molecules that attracted significant attention from the synthetic community due to their diverse applications.[1] In particular, fluoranthenes constitute a widely encountered subclass of polycylic aromatic hydrocarbons, most members of which are fluorescent.[2] The optoelectronic properties of substituted fluoranthenes have culminated in a broad range of applications including design of fluorescent probes,[3] yellow and blue organic light emitting diodes (OLEDs, Figure , compounds 1 and 2),[4,5] thin film organic field-effect transistors (OFETs, compound 3),[6] and new materials for organic photovoltaic cells.[7] Moreover, benzo[j]fluoranthenes comprise the structural skeleton of many highly oxygenated, biologically active fungal natural products including truncatone C (4)[8] and daldinone B (5, Figure ).[9,10]

Figure 1

Important fluoranthene analogues.

Catalytic methods using transition metal complexes,[11] Lewis acids,[12] or Brønsted acids[13] are among the most commonly applied transformations for the synthesis and derivatization of fluoranthenes. Cycloaddition and cyclization reactions have also been utilized for the construction of the fluoranthene skeleton from simpler building blocks.[3,4,14−16] For instance, inverse electron-demand Diels–Alder reactions of cyclopentadienone 6 with alkynes at high temperatures (200–220 °C) were shown to provide multisubstituted fluoranthenes (7) in an effective manner (Scheme a).[5,17] In a study reported by Lu, Wang and co-workers in 2011, the I2-mediated cyclization of dialkynylnaphthalenes (e.g., compound 8) resulted in the formation of iodofluoranthenes (Scheme b).[18] Compared to aryl-substituted fluoranthenes, direct access to hydroxyfluoranthenes has been rather underdeveloped. In a rare example of such a transformation, alkenyl ketone substrates 10 were reported to give complex hydroxyfluoranthenes 11 via an anionic-radical reaction cascade promoted by KHMDS (Scheme c).[19] Against this background, with the goal of discovering a direct method to access hydroxyfluoranthenes without the requirement of protection/deprotection steps, we designed the reaction sequence shown in Scheme d. According to this design, 1-iodo-8-alkynylnaphthalenes (12), which were planned to be prepared by a selective monoalkynylation of 1,8-diiodonaphthalene, would be subjected to a Suzuki–Miyaura coupling with 2-furylboronic acid under Pd catalysis. In the coupling products 13, furan and alkyne moieties are perfectly aligned in space for an intramolecular Diels–Alder reaction[20] to give cycloadducts 14, which were expected to undergo a ring opening reaction to release the ring strain and gain aromaticity to ultimately form hydroxyfluoranthenes 15. Moreover, we hypothesized that these three steps could proceed under the same reaction conditions resulting in a domino reaction sequence,[21] which would give directly the targeted hydroxyfluoranthene products. It is important to note that this hypothesis was based on the assumption that the reaction conditions for the initial Suzuki–Miyaura coupling would be suitable for the subsequent intramolecular Diels–Alder and ring-opening reactions.

Scheme 1

Synthesis of Fluoranthenes by Cycloaddition and Cyclization Reactions

In order to test our hypothesis, we first prepared alkynone 12a to be used in the designed domino reaction sequence (Scheme ). For this purpose, 1,8-diiodonaphthalene (16) was subjected to a Sonogashira cross-coupling with propargylic alcohol 17a to afford the monoalkynylation product 18a in 71% yield. It should be noted that, in the Sonogashira reactions carried out in the present work, the use of an excess amount of 1,8-diiodonaphthalene (4 equiv) was found to be crucial to minimize the formation of dialkynylation products. Pleasingly, an unreacted excess of 1,8-diiodonaphthalene (16) was isolated with 75% recovery at the end of its Sonogashira reaction with alkyne 17a. Oxidation of alcohol 18a proceeded efficiently with MnO2 giving the ketone product 12a in 91% yield. In the key domino reaction step, we were delighted to obtain hydroxyfluoranthene product 15a in an excellent yield of 92% upon the reaction of alkynone 12a with 2-furylboronic acid (19) in the presence of Pd(PPh3)4 (Scheme ). We reckon that the initial Suzuki–Miyaura cross-coupling would form 13a, which would be both electronically and geometrically well-suited for an intramolecular Diels–Alder reaction to give pentacyclic intermediate 14a. Finally, the spontaneous aromatization-driven ring-opening isomerization of 14a would result in the formation of hydroxyfluoranthene 15a. This three-step sequence takes place under the same reaction conditions in a domino fashion obviating the need for the isolation of intermediates 13a and 14a.

Scheme 2

Synthesis of Hydroxyfluoranthene 15a

With the validation of our hypothesis on the designed domino reaction sequence for fluoranthene synthesis, we next decided to investigate the scope of this methodology. To this end, we first synthesized 1-iodo-8-alkynylnaphthalene derivatives 12 which would serve as the precursors for the key domino reaction (Table ). The aryl-substituted alkynones 12b-g were prepared by an efficient two-step sequence. Initially, the highly selective monoalkynylative Sonogashira coupling reactions between 1,8-diiodonaphthalene (16) and propargylic alcohols 17 afforded monoiodoalkynol products in 70–85% isolated yields along with minimal formation of dialkynylation products (Table , entries 1–6). It is worth noting that this optimized protocol works successfully with both electron-rich and electron-deficient aryl groups as well as heteroaromatic substituents such as thiophene and furan. Among the methods tested for the oxidation of alkynols 18 to alkynones 12, PCC (pyridinium chlorochromate)[22] and Parikh-Doering oxidation[23] methods worked with moderate reaction yields.[24] On the other hand, both DMP (Dess-Martin periodinane)[25] and MnO2 were found to be highly effective oxidants for this transformation with MnO2 providing slightly higher yields. Overall, the oxidation of alkynols 18b-g to alkynones 12b-g were achieved in 53–90% yields (Table , entries 1–6). Finally, Me-substituted alkynone 12h and alkynyl amide 12i were synthesized in 53 and 82% yields, respectively, via the direct monoalkynylative Sonogashira coupling of 16 with the commercially available 3-butyn-2-one (20a) and propiolamide (20b) (Table , entries 7 and 8). It is important to note that electron-deficient Me-substituted alkyne 20a was observed to undergo decomposition when Et3N was used both as base and the reaction solvent in the Sonogashira coupling, possibly via an aza-Michael-type reaction pathway. This decomposition was circumvented with the use of the bulkier and less nucleophilic Hünig’s base (i-Pr2NEt) in the Sonogashira coupling along with DMSO as solvent.[26]

Table 1

Synthesis of Alkynones 12 as Precursors of the Domino Reaction Sequence for Fluoranthene Synthesis

Yields refer to isolated product yields after purification by column chromatography.

In this reaction, Dess-Martin periodinane (DMP) was used as the oxidant.

With the alkynes 12b–i in hand, we next focused on their reactivity in the key domino reaction sequence for the synthesis of targeted hydroxyfluoranthenes. When alkynones 12b and 12c bearing electron-rich phenyl rings were reacted with 2-furylboronic acid (19) under the coupling conditions, hydroxyfluoranthenes 15b and 15c were isolated in 73% and 90% yields, respectively (Scheme ). The domino reaction was observed to work successfully with electron-deficient aryl rings as well affording fluoranthene products 15d and 15e in good yields (69% and 52%, respectively). Afterward, we turned our attention to heteroaromatic alkynone substrates. We were pleased to see that the domino reaction of thienyl-substituted alkynone 12f gave the corresponding hydroxyfluoranthene 15f in excellent yield (91%). Gratifyingly, the furan ring present in 12g did not interfere in its reaction with 2-furylboronic acid (19), and the desired product 15g was isolated in 72% yield. The methyl-substituted alkynone 12h was also found to be a competent substrate in the domino sequence affording fluoranthene 15h, albeit in a lower yield (38%). Finally, the domino reaction sequence of the amide-containing substrate 12i led successfully to the formation of the desired product 15i in 53% isolated yield.

Scheme 3

Scope of the Fluoranthene Synthesis

The phenolic −OH groups of the fluoranthene products 15a–i were all observed to make intramolecular hydrogen bonds with their neighboring ketone or amide carbonyls as revealed by the corresponding signals between 7.99 and 10.53 ppm in their 1H NMR spectra.[27] In addition, the structure of amide-substituted fluoranthene product 15i was confirmed by single-crystal X-ray diffraction analysis (Figure a). The intramolecular hydrogen bond between the phenol −OH and the amide C=O is clearly observed in this structure with an O–H···O=C distance of 1.84 Å. Not surprisingly, the −CONH2 group is tilted with a dihedral angle of 35.6° with respect to the plane of the phenol ring, possibly to minimize the steric repulsion between the naphthalene C–H and amide −NH2 hydrogens. Interestingly, in addition to the intramolecular hydrogen bond with the −OH group, the amide oxygen participates in two additional intermolecular hydrogen bonds with the −NH hydrogens of two adjacent fluoranthenes with N–H···O=C distances of 2.10 and 2.21 Å (Figure b).

Figure 2

Crystal structure of fluoranthene 15i (a) showing 50% probability displacement ellipsoids and the atomic numbering; (b) showing the formation of O–H···O and N–H···O hydrogen bonds.

Finally, we sought to test the effectiveness of the intramolecular Diels–Alder reaction of alkynylnaphthalene substrates without electron-withdrawing groups. To this end, we first prepared aryl-substituted alkynes 12j and 12k to be used in the domino sequence (Scheme ). The monoalkynylative Sonogashira coupling between 16 and phenylacetylene proceeded smoothly under the optimized conditions to afford iodoalkyne 12j in 84% yield. When 12j was subjected to the standard domino sequence conditions, Suzuki–Miyaura coupling product 13j was obtained as the major product in 92% yield (Scheme ). This result is not surprising when the electron-rich nature of furan as a diene and the Ph-substituted alkyne as a dienophile in the structure of 13j is considered. However, when a pure sample of 13j was heated in mesitylene at 130 °C, fluoranthene 15j was observed to form in 55% yield. This observation clearly supports the intermediacy of 1-furyl-8-alkynylnaphthalenes en route to the formation of fluoranthenes in the developed domino reaction sequence. It should also be noted that the reaction between 12j and 19 with the use of Pd(PPh3)4 at 80 °C in EtOH/water gave Suzuki–Miyaura product 13j in 53% yield along with the fluoranthene product 15j (14% yield) with a reaction time of 50 h. Next, in order to see the effect of an electron-withdrawing group on the aryl ring, 4-nitrophenyl-substituted iodoalkyne 12k was prepared in 86% yield via the Sonogashira reaction of 16 with 1-ethynyl-4-nitrobenzene (21). The reaction of 12k with 2-furylboronic acid (19) gave hydroxyfluoranthene 15k in 25% yield, indicating a slight benefit of having an electron-withdrawing −NO2 group on the aryl ring in the intramolecular Diels–Alder reaction with furan.

Scheme 4

Intramolecular Diels–Alder Reactions of Aryl-Substituted Alkynes

In summary, we have developed a new strategy to rapidly access substituted hydroxyfluoranthenes via a carefully designed domino reaction sequence. The first step of the newly developed method involves a selective monoalkynylative Sonogashira cross-coupling of 1,8-diiodonaphthalene that leads to the formation of a variety of 1-iodo-8-alkynylnaphthalenes. The propargylic alcohol derivatives 18a–g were oxidized to the corresponding ketones in high yields (53–91%). The key domino reaction sequence starting from iodoalkynes 12 and 2-furylboronic acid with the use of Pd(PPh3)4 (5 mol %) afforded hydroxyfluoranthene products 15 effectively in up to 92% yield. This domino sequence consists of a Suzuki–Miyaura coupling, an intramolecular Diels–Alder reaction, and an aromatization-driven ring-opening isomerization, which all occur under the same reaction conditions. It is important to note that this method obviates the need to have protection/deprotection steps on the −OH group, as it provides directly the hydroxyfluoranthene products at the end of the domino sequence. Studies to discover novel domino reactions to enable access to other types of polycyclic aromatic hydrocarbons are currently underway in our laboratory.

Experimental Section

General Information

All reactions except the oxidation reactions of alcohols 18 with MnO2 were performed using oven-dried glassware under an inert atmosphere of nitrogen. Aluminum-backed plates precoated with silica gel (Silicycle, 60 Å, F254) were used for reaction monitoring by thin-layer chromatography (TLC). UV light (254 and 366 nm) and KMnO4 staining solution were used for TLC visualization. Flash column chromatography was carried out using Silicycle 40–63 μm (200–400 mesh) flash silica gel. NMR spectra were recorded on a Bruker spectrometer at 400 MHz for 1H NMR spectra and 100 MHz for 13C{1H} spectra, and calibrated from an internal standard (TMS, 0 ppm) or residual solvent signals (chloroform at 7.26 ppm for 1H NMR spectra; chloroform at 77.16 ppm for 13C NMR spectra). For 19F{1H}-NMR experiments, trifluoroacetic acid (CF3CO2H) was used as external reference (−76.55 ppm). 1H NMR data are reported as follows: chemical shift (parts per million, ppm), integration, multiplicity (s = singlet, d = doublet, t = triplet, dd = doublet of doublets, m = multiplet, br = broad, app = apparent), coupling constant (Hz). Infrared (FTIR) spectra were recorded using a Bruker Alpha-Platinum-ATR spectrometer, and only selected peaks are reported. HRMS (high resolution mass spectrometry) analyses were performed on Agilent Technologies 6224 TOF LC/MS at the UNAM-National Nanotechnology Research Center and Institute of Materials Science and Nanotechnology, Bilkent University, and on Agilent Technologies 6530 QTOF-LC/MS at DAYTAM-East Anatolia High Technology Application and Research Center, Atatürk University. Single-crystal XRD analysis was performed at the Scientific and Technological Research Application and Research Center, Sinop University, Turkey. Melting points are uncorrected. Anhydrous CH2Cl2, THF, and 1,4-dioxane were purchased from Acros Organics (AcroSeal). 1,8-Diaminonaphthalene was recrystallized from n-heptane prior to use. 2-Furylboronic (furan-2-boronic) acid was purchased from Acros Organics and used as received. Furan-2-boronic acid pinacol ester was prepared following a reported procedure.[28] Unless stated otherwise, all commercially available reagents were used without further purification.

General Procedure A for the Sonogashira Reaction Between Alkynes and 1,8-Diiodonaphthalene (16)

To a solution of alkyne (1.0 equiv) and 1,8-diiodonaphthalene (16, 4 equiv) in Et3N or THF/Et3N, Pd(PPh3)2Cl2 (7 mol %) and CuI (14 mol %) were added at 23 °C under N2. The resulting reaction mixture was stirred at 23 °C until TLC showed full consumption of the alkyne. Usually, a color change from yellow to orange was observed. Et3N was removed under reduced pressure. The remaining residue was dissolved in a sufficient amount of EtOAc or CH2Cl2 and washed once with H2O. The organic phase was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash column chromatography. The use of 2 equiv of 1,8-diiodonaphthalene was observed to afford the desired monoalkynylation product in considerably lower yield.

3-(8-Iodonaphthalen-1-yl)-1-phenylprop-2-yn-1-ol (18a)

Product 18a was prepared using 1,8-diiodonaphthalene (16, 1.15 g, 3.02 mmol), alkyne 17a (100 mg, 0.76 mmol), Pd(PPh3)2Cl2 (37.2 mg, 0.053 mmol), CuI (20.3 mg, 0.11 mmol), Et3N (6 mL) and THF (2 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:5) to afford pure 18a (208 mg, 71% yield) as an orange oil. After column chromatography unreacted 1,8-diiodonaphthalene (16, 858 mg, 75%) was recovered. R = 0.31 (EtOAc/hexanes = 1:5). 1H NMR (400 MHz; CDCl3) δ: 8.26 (1H, dd, J = 7.4, 1.3 Hz), 7.86 (1H, dd, J = 7.2, 1.4 Hz), 7.82 (1H, dd, J = 4.3, 1.2 Hz), 7.80 (1H, dd, J = 4.5, 1.3 Hz), 7.70–7.66 (2H, m), 7.45–7.33 (4H, m), 7.09 (1H, dd, J = 8.0, 7.5 Hz), 5.81 (1H, d, J = 5.3 Hz), 2.46 (1H, d, J = 5.8 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 142.9, 140.2, 136.5, 135.0, 132.1, 130.9, 130.3, 128.8, 128.5, 127.3, 127.2, 125.5, 122.0, 100.0, 92.9, 86.4, 66.1. FTIR νmax (ATR, film)/cm–1 3371, 2918, 2850, 1553, 1493, 1453, 1362, 1196, 1047, 1036, 1002, 947, 817, 758, 717, 698. HRMS (ESI+) calcd for C19H13INaO [M + Na]+, 406.9903; found, 406.9896.

3-(8-Iodonaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-yn-1-ol (18b)

Product 18b was prepared using 1,8-diiodonaphthalene (16, 291 mg, 0.76 mmol), alkyne 17b (31 mg, 0.19 mmol), Pd(PPh3)2Cl2 (9.4 mg, 0.013 mmol), CuI (5.1 mg, 0.026 mmol), and Et3N (6 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:5) to afford pure 18b (57 mg, 72% yield) as a reddish orange oil. After column chromatography unreacted 1,8-diiodonaphthalene (16, 209 mg, 72%) was recovered. R = 0.40 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 8.24 (1H, dd, J = 7.4, 1.2 Hz), 7.84 (1H, dd, J = 7.3, 1.4 Hz), 7.82–7.75 (2H, m), 7.60 (2H, app d, J = 8.6 Hz), 7.38 (1H, dd, J = 8.2, 7.3 Hz), 7.07 (1H, dd, J = 8.0, 7.5 Hz), 6.93 (2H, d, J = 8.8 Hz), 5.76 (1H, s), 3.81 (3H, s), 2.65 (1H, br s). 13C{1H} NMR (100 MHz; CDCl3) δ: 159.8, 142.8, 136.4, 134.9, 132.6, 130.8, 130.2, 128.6, 128.4, 127.2, 125.4, 122.1, 114.1, 100.3, 92.9, 86.04, 65.6, 55.5. FTIR νmax (ATR, film)/cm–1 3399 (br), 1610, 1510, 1362, 1303, 1248, 1172, 1034. HRMS (ESI+) calcd for C20H15IO2 [M]+, 414.0111; found, 414.0116.

1-(Benzo[d][1,3]dioxol-5-yl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-ol (18c)

Product 18c was prepared using 1,8-diiodonaphthalene (16, 345 mg, 0.92 mmol), alkyne 17c (40 mg, 0.23 mmol), Pd(PPh3)2Cl2 (11.2 mg, 0.016 mmol), CuI (6.05 mg, 0.032 mmol), and Et3N (6 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:4 → 1:2) to afford pure 18c (68 mg, 70% yield) as a reddish yellow oil. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 275 mg, 80%) was recovered. R = 0.48 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.25 (1H, dd, J = 7.4, 1.3 Hz), 7.84 (1H, dd, J = 7.2, 1.4 Hz), 7.81–7.76 (2H, m), 7.38 (1H, dd, J = 8.2, 7.3 Hz), 7.19 (1H, d, J = 1.7 Hz), 7.13 (1H, dd, J = 8.0, 1.7 Hz), 7.07 (1H, dd, J = 8.0, 7.5 Hz), 6.82 (1H, d, J = 8.0 Hz), 5.97 (2H, s), 5.70 (1H, s). 2.63 (1H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 148.0, 147.7, 142.8, 136.4, 134.9, 134.4, 132.0, 130.9, 130.3, 127.2, 125.5, 121.9, 120.8, 108.3, 107.9, 101.3, 100.0, 92.9, 86.2, 65.9. FTIR νmax (ATR, film)/cm–1 3396, 2961, 2922, 1553, 1501, 1486, 1442, 1362, 1246, 1093, 1038, 936. HRMS (ESI+) calcd for C20H13INaO3 [M + Na]+, 450.9802; found, 450.9796.

1-(4-Chlorophenyl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-ol (18d)

Product 18d was prepared using 1,8-diiodonaphthalene (16, 273 mg, 0.72 mmol), alkyne 17d (30 mg, 0.18 mmol), Pd(PPh3)2Cl2 (8.8 mg, 0.013 mmol), CuI (5.0 mg, 0.026 mmol), and Et3N (5 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9) to afford pure 18d (53 mg, 71% yield) as a brown solid. After column chromatography unreacted 1,8-diiodonaphthalene (16, 210 mg, 77%) was recovered. Mp: 109.3–109.6 °C (CHCl3). R = 0.42 (EtOAc/hexanes = 1:4). 1H NMR (400 MHz; CDCl3) δ: 8.25 (1H, dd, J = 7.4, 1.2 Hz), 7.84–7.78 (3H, m), 7.61–7.58 (2H, m), 7.41–7.35 (3H, m), 7.08 (1H, t, J = 7.8 Hz), 5.78 (1H, s), 2.72 (1H, br s). 13C{1H} NMR (100 MHz; CDCl3) δ: 142.9, 138.7, 136.5, 134.9, 134.2, 132.0, 131.1, 130.3, 128.8, 128.5, 127.3, 125.5, 121.7, 99.5, 92.8, 86.6, 65.3. FTIR νmax (ATR, film)/cm–1 3365 (br), 1553, 1489, 1405, 1362, 1197, 1089, 1048, 1036, 1014. HRMS (ESI+) calcd for C19H1235ClINaO [M + Na]+, 440.9514; found, 440.9520.

3-(8-Iodonaphthalen-1-yl)-1-(4-(trifluoromethyl)phenyl)prop-2-yn-1-ol (18e)

Product 18e was prepared using 1,8-diiodonaphthalene (16, 214 mg, 0.56 mmol), alkyne 17e (28.2 mg, 0.14 mmol), Pd(PPh3)2Cl2 (6.9 mg, 0.0099 mmol), CuI (3.8 mg, 0.019 mmol), and Et3N (5 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:3) to afford pure 18e (54.3 mg, 85% yield) as an orange solid. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 151 mg, 71%) was recovered. Mp: 126–127 °C (CHCl3). R = 0.48 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 8.27 (1H, d, J = 7.4 Hz), 7.85–7.82 (3H, m), 7.80 (2H, d, J = 8.2 Hz), 7.68 (2H, d, J = 8.2 Hz), 7.42 (1H, t, J = 7.7 Hz), 7.11 (1H, t, J = 7.8 Hz), 5.86 (1H, d, J = 4.9 Hz), 2.64 (1H, d, J = 5.5 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 144.0, 142.9, 136.6, 135.0, 132.1, 131.3, 130.5, 129.6, 128.6, 127.39, 127.36, 125.7 (q, 3JC–F = 3.9 Hz), 125.5, 124.6, 122.9, 121.6, 99.1, 92.8, 86.9, 65.4. (Since the aromatic region is crowded, two quartet signals with 13C–19F couplings could not be identified with certainty). FTIR νmax (ATR, film)/cm–1 3267, 1408, 1323, 1159, 1107, 1067, 1047, 1034, 1014, 972, 967. HRMS (ESI+) calcd for C20H12F3INaO [M + Na]+, 474.9777; found, 474.9783.

3-(8-Iodonaphthalen-1-yl)-1-(thiophen-2-yl)prop-2-yn-1-ol (18f)

Product 18f was prepared using 1,8-diiodonaphthalene (16, 308 mg, 0.81 mmol), alkyne 17f (28 mg, 0.20 mmol), Pd(PPh3)2Cl2 (10.0 mg, 0.014 mmol), CuI (5.4 mg, 0.028 mmol), and Et3N (6 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:5) to afford pure 18f (64.5 mg, 82% yield) as a reddish orange oil. After column chromatography unreacted 1,8-diiodonaphthalene (16, 223 mg, 72%) was recovered. R = 0.44 (EtOAc/hexanes = 1:5). 1H NMR (400 MHz; CDCl3) δ: 8.25 (1H, dd, J = 7.4, 1.3 Hz), 7.87 (1H, dd, J = 7.2, 1.4 Hz), 7.81–7.79 (2H, m), 7.40 (1H, dd, J = 8.1, 7.3 Hz), 7.33 (1H, dd, J = 5.1, 1.3 Hz), 7.31 (1H, dt, J = 3.5, 1.0 Hz), 7.08 (1H, t, J = 7.8 Hz), 7.01 (1H, dd, J = 5.0, 3.6 Hz), 6.02 (1H, d, J = 6.5 Hz), 2.77 (1H, d, J = 6.5 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 144.3, 142.8, 136.6, 134.9, 132.1, 131.1, 130.3, 127.3, 126.9, 126.1, 125.9, 125.5, 121.7, 99.3, 92.9, 85.8, 61.8. FTIR νmax (ATR, film)/cm–1 3367, 1553, 1363, 1227, 1199, 1047, 1034, 997, 939. HRMS (ESI+) calcd for C17H11INaOS [M + Na]+, 412.9467; found, 412.9469.

1-(Furan-2-yl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-ol (18g)

Product 18g was prepared using 1,8-diiodonaphthalene (16, 377 mg, 1.0 mmol), alkyne 18g (30 mg, 0.25 mmol), Pd(PPh3)2Cl2 (12.3 mg, 0.018 mmol), CuI (6.7 mg, 0.035 mmol), and Et3N (6 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:7→ 1:5) to afford pure 18g (66 mg, 71% yield) as a red oil. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 292 mg, 78%) was recovered. R = 0.37 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 8.25 (1H, dd, J = 7.4, 1.3 Hz), 7.86 (1H, dd, 7.2, 1.4 Hz), 7.81–7.76 (2H, m), 7.46 (1H, dd, J = 1.8, 0.8 Hz), 7.39 (1H, dd, J = 8.1, 7.3 Hz), 7.07 (1H, dd, J = 8.0, 7.5 Hz), 6.59 (1H, d, J = 3.3 Hz), 6.39 (1H, dd, J = 3.3, 1.9 Hz), 5.81 (1H, s), 2.73 (1H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 152.7, 143.1, 142.8, 136.6, 134.9, 132.2, 131.1, 130.3, 127.2, 125.4, 121.7, 110.6, 108.3, 97.7, 92.9, 85.5, 59.7. FTIR νmax (ATR, film)/cm–1 3385, 2363, 1553, 1495, 1362, 1143, 1047, 1005. HRMS (ESI+) calcd for C17H11INaO2 [M + Na]+, 396.9696; found, 396.9697.

4-(8-Iodonaphthalen-1-yl)but-3-yn-2-one (12h)

Product 12h was prepared using 1,8-diiodonaphthalene (16, 288 mg, 0.76 mmol), 3-butyn-2-one (20a, 13 mg, 15 μL, 0.19 mmol), Pd(PPh3)2Cl2 (9.1 mg, 0.013 mmol), CuI (5.1 mg, 0.027 mmol) DMSO (3 mL), and i-Pr2NEt (0.1 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19 → 1:9) to afford pure 12h (32.4 mg, 53% yield) as an orange oil. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 223 mg, 77%) was recovered. R = 0.53 (EtOAc/hexanes = 1:5). 1H NMR (400 MHz; CDCl3) δ: 8.31 (1H, dd, J = 7.4, 1.2 Hz), 7.98 (1H, dd, J = 7.3, 1.3 Hz), 7.91 (1H, dd, J = 8.2, 1.3 Hz), 7.86 (1H, dd, J = 8.2, 1.0 Hz), 7.45 (1H, dd, J = 8.1, 7.4 Hz), 7.15 (1H, t, J = 7.6 Hz), 2.51 (3H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 184.7, 143.3, 139.1, 135.0, 133.2, 132.7, 130.5, 127.7, 125.6, 119.7, 99.9, 92.7, 90.1, 31.9. FTIR νmax (ATR, film)/cm–1 2168, 1654, 1364, 1353, 1276, 1192, 1159, 1071, 970, 816, 757. HRMS (ESI+) calcd for C14H10IO [M + H]+, 320.9771; found, 320.9771.

3-(8-Iodonaphthalen-1-yl)propiolamide (12i)

Product 12i was prepared using 1,8-diiodonaphthalene (16, 440 mg, 1.16 mmol), propiolamide (20b, 20 mg, 0.29 mmol), Pd(PPh3)2Cl2 (14.2 mg, 0.020 mmol), CuI (7.7 mg, 0.041 mmol), DMSO (4 mL), and Et3N (1 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:2 → 1:1→ 2:1) to afford pure 12i (76.4 mg, 82% yield) as a pale brown solid. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 343 mg, 78%) was recovered. R = 0.27 (EtOAc/hexanes = 1:1); 0.43 (EtOAc/hexanes = 2:1). 1H NMR (400 MHz; CDCl3) δ: 8.30 (1H, dd, J = 7.4, 1.2 Hz), 7.98 (1H, dd, J = 7.3, 1.4 Hz), 7.90 (1H, dd, J = 8.2, 1.3 Hz), 7.86 (1H, dd, J = 8.1, 1.1 Hz), 7.45 (1H, dd, J = 8.2, 7.3 Hz), 7.15 (1H, t, J = 7.8 Hz), 5.96 (2H, br s). 13C{1H} NMR (100 MHz; CDCl3) δ: 155.1, 144.2, 143.2, 138.5, 135.0, 132.8, 130.6, 127.7, 125.6, 119.6, 93.9, 92.7, 85.6. FTIR νmax (ATR, film)/cm–1 3454, 3352, 3194, 2925, 1650, 1598, 1440, 1396, 1280, 816. HRMS (ESI+) calcd for C13H8INNaO [M + Na]+, 343.9543; found, 343.9534.

1-Iodo-8-(phenylethynyl)naphthalene (12j)

Product 12j was prepared using 1,8-diiodonaphthalene (16, 149 mg, 0.39 mmol), phenylacetylene (10.0 mg, 10.8 μL, 0.098 mmol), Pd(PPh3)2Cl2 (4.8 mg, 0.0069 mmol), CuI (2.6 mg, 0.014 mmol), and Et3N (4 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; hexanes) to afford pure 12j (29.2 mg, 84% yield) as a yellow oil. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 110 mg, 74%) was recovered. R = 0.43 (EtOAc/hexanes = 1:49). 1H NMR (400 MHz; CDCl3) δ: 8.31 (1H, dd, J = 7.3, 1.3 Hz), 7.93 (1H, dd, J = 7.2, 1.4 Hz), 7.84 (1H, dd, J = 8.2, 1.1 Hz), 7.81 (1H, dd, J = 8.2, 1.3 Hz), 7.68–7.65 (2H, m), 7.45 (1H, dd, J = 8.0, 7.4 Hz), 7.42–7.36 (3H, m), 7.11 (1H, t, J = 7.8 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 142.8, 136.1, 135.0, 132.0, 131.0, 130.5, 130.3, 128.6, 128.5, 127.2, 125.6, 124.2, 123.0, 101.0, 93.1, 89.4. FTIR νmax (ATR, film)/cm–1 3054, 2923, 2851, 1597, 1551, 1489, 1441. HRMS (APCI+) Calcd for C18H12I [M + H]+, 354.9978; found, 354.9973.

1-Iodo-8-((4-nitrophenyl)ethynyl)naphthalene (12k)

Product 12k was prepared using 1,8-diiodonaphthalene (16, 517 mg, 1.36 mmol), 1-ethynyl-4-nitrobenzene (50.0 mg, 0.34 mmol), Pd(PPh3)2Cl2 (16.7 mg, 0.024 mmol), CuI (9.1 mg, 0.048 mmol), and Et3N (6 mL) according to General Procedure A. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19) to afford pure 12k (116 mg, 86% yield) as a bright yellow solid. After column chromatography, unreacted 1,8-diiodonaphthalene (16, 391 mg, 76%) was recovered. Mp: 163.3–165.0 °C. R = 0.35 (EtOAc/hexanes = 1:5). 1H NMR (400 MHz; CDCl3) δ: 8.32 (1H, dd, J = 7.4, 1.2 Hz), 8.25 (2H, d, J = 8.9 Hz), 7.96 (1H, dd, J = 7.2, 1.3 Hz), 7.87 (2H, d, J = 8.2 Hz), 7.78 (2H, d, J = 8.9 Hz), 7.48 (1H, t, J = 7.7 Hz), 7.15 (1H, t, J = 7.8 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 147.2, 143.1, 136.8, 135.1, 132.1, 131.7, 131.5, 130.9, 130.5, 127.6, 125.6, 123.9, 121.8, 98.9, 94.7, 92.8. FTIR νmax (ATR, film)/cm–1 2185, 1592, 1506, 1347, 1339, 1311. HRMS (ESI+) calcd for C18H10INNaO2 [M + Na]+, 421.9648; found, 421.9647.

General Procedure B for the Oxidation of Propargyl Alcohols with MnO2

To a solution of propargyl alcohol in acetone (0.025 M), MnO2 (20 equiv) was added at 23 °C. The reaction mixture was stirred at this temperature until TLC indicated full consumption of alcohol which occurred within 1–2 h. The reaction mixture was then diluted with CH2Cl2 and filtered. SiO2 was added to the resulting solution, the solvent was removed under reduced pressure, and the obtained solid was loaded directly to the column. Purification by flash column chromatography on SiO2 afforded the desired ketone product.

3-(8-Iodonaphthalen-1-yl)-1-phenylprop-2-yn-1-one (12a)

Product 12a was obtained from alcohol 18a (530 mg, 1.38 mmol) using MnO2 (2.82 g, 27.6 mmol) and acetone (30 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:7 → 1:6 → 1:5 → 1:4) to afford pure 12a (527 mg, 91% yield) as an orange oil. R = 0.23 (EtOAc/hexanes = 1:19). 1H NMR (400 MHz; CDCl3) δ: 8.32 (3H, app d, J = 7.4 Hz), 8.10 (1H, dd, J = 7.2, 1.3 Hz), 7.94 (1H, dd, J = 8.2, 0.9 Hz), 7.89 (1H, dd, J = 8.1, 0.8 Hz), 7.64 (1H, tt, J = 7.4, 1.3 Hz), 7.57–7.48 (3H, m), 7.18 (1H, dd, J = 8.0, 7.5 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 178.1, 143.3, 138.6, 137.1, 135.1, 134.2, 133.0, 132.8, 130.4, 130.0 128.8, 127.8, 125.6, 120.3, 99.2, 93.1, 92.5. FTIR νmax (ATR, film)/cm–1 2174, 1632, 1597, 1578, 1449, 1363, 1339, 1313, 1286, 1226, 1170, 1046, 979, 817, 756, 698. HRMS (ESI+) calcd for C19H12IO [M + H]+, 382.9927; found, 382.9927.

3-(8-Iodonaphthalen-1-yl)-1-(4-methoxyphenyl)prop-2-yn-1-one (12b)

Product 12b was obtained from alcohol 18b (15 mg, 0.036 mmol) using MnO2 (74 mg, 0.72 mmol) and acetone (1.5 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:5 → 1:4) to afford pure 12b (12.4 mg, 83% yield) as an orange oil. R = 0.53 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 8.31–8.27 (3H, m), 8.06 (1H, dd, J = 7.3, 1.4 Hz), 7.91 (1H, dd, J = 8.2, 1.1 Hz), 7.86 (1H, dd, J = 8.2, 1.2 Hz), 7.48 (1H, dd, J = 8.1, 7.3 Hz), 7.15 (1H, dd, J = 8.1, 7.4 Hz), 6.99 (2H, app d, J = 9.0 Hz), 3.90 (3H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 176.6, 164.5, 143.0, 138.3, 134.9, 132.6, 132.5, 132.2, 130.4, 130.2, 127.6, 125.4, 120.3, 113.9, 99.1, 93.0, 91.6, 55.6. FTIR νmax (ATR, film)/cm–1 2174, 1627, 1596, 1572, 1508, 1290, 1258, 1235, 1162, 1028. HRMS (ESI+) calcd for C20H14IO2 [M + H]+, 413.0033; found, 413.0041.

1-(Benzo[d][1,3]dioxol-5-yl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-one (12c)

Compound 12c was obtained from alcohol 18c (22 mg, 0.051 mmol) using MnO2 (102 mg, 1.0 mmol) and acetone (1.5 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:3) to afford pure 12c (17.3 mg, 79% yield) as a yellow oil. R = 0.66 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.30 (1H, dd, J = 7.4, 1.3 Hz), 8.06 (1H, dd, J = 7.3, 1.4 Hz), 8.01 (1H, dd, J = 8.2, 1.7 Hz), 7.93 (1H, dd, J = 8.3, 1.2 Hz), 7.87 (1H, dd, J = 8.2, 1.1 Hz), 7.69 (1H, d, J = 1.7 Hz), 7.49 (1H, dd, J = 8.1, 7.3 Hz), 7.16 (1H, dd, J = 8.0, 7.5 Hz), 6.92 (1H, d, J = 8.2 Hz), 6.08 (2H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 176.2, 153.0, 143.2, 138.4, 135.1, 132.9, 132.7, 132.4, 130.4, 128.7, 127.8, 127.7, 125.6, 120.4, 108.7, 108.2, 102.2, 99.1, 93.1, 91.8. FTIR νmax (ATR, film)/cm–1 2175, 1625, 1598, 1502, 1486, 1444, 1362, 1289, 1262, 1250, 1037. HRMS (ESI+) calcd for C20H11INaO3 [M + Na]+, 448.9645; found, 448.9652.

1-(4-Chlorophenyl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-one (12d)

To a solution of propargyl alcohol 18d (25 mg, 0.06 mmol) in CH2Cl2 (1.5 mL), Dess-Martin periodinane (27.9 mg, 0.066 mmol) was added at 0 °C. The orange reaction mixture was stirred for 15 min at 0 °C and then warmed to 23 °C. The color of the reaction became cloudy yellow over time. The reaction mixture was stirred at 23 °C until TLC indicated full consumption of 18d which occurred in 1 h. The reaction mixture was diluted with CH2Cl2 and filtered. The organic phase was washed with saturated aqueous solution of NaHCO3. The aqueous phase was extracted three times with DCM. The combined organic layer was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:4) to afford pure 12d (20 mg, 80% yield) as a bright orange solid. R = 0.36 (EtOAc/hexanes = 1:9). 1H NMR (400 MHz; CDCl3) δ: 8.31 (1H, dd, J = 7.4, 1.2 Hz), 8.27–8.23 (2H, m), 8.08 (1H, dd, J = 7.2, 1.4 Hz), 7.95 (1H, dd, J = 8.2, 1.3 Hz), 7.88 (1H, dd, J = 8.2, 1.1 Hz), 7.52–7.48 (3H, m), 7.18 (1H, t, J = 7.8 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 176.7, 143.3, 141.8, 140.8, 138.7, 135.5, 135.1, 133.2, 131.3, 130.4, 129.2, 127.8, 125.6, 120.0, 98.8, 93.03, 93.01. FTIR νmax (ATR, film)/cm–1 2175, 1634, 1586, 1363, 1339, 1287, 1224, 1167, 1090, 981. HRMS (ESI+) calcd for C19H1035ClINaO [M + Na]+, 438.9357; found, 438.9358.

3-(8-Iodonaphthalen-1-yl)-1-(4-(trifluoromethyl)phenyl)prop-2-yn-1-one (12e)

Product 12e was obtained from alcohol 18e (22.0 mg, 0.049 mmol) using MnO2 (100 mg, 0.98 mmol) and acetone (2.0 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:7 → 1:5) to afford pure 12e (13.7 mg, 63% yield) as a bright orange solid. R = 0.53 (EtOAc/hexanes = 1:5). 1H NMR (400 MHz; CDCl3) δ: 8.42 (2H, d, J = 8.1 Hz), 8.32 (1H, dd, J = 7.4, 1.2 Hz), 8.10 (1H, dd, J = 7.3, 1.4 Hz), 7.97 (1H, dd, J = 8.2, 1.4 Hz), 7.90 (1H, dd, J = 8.1, 1.2 Hz), 7.80 (2H, d, J = 8.1 Hz), 7.52 (1H, t, J = 7.7 Hz), 7.19 (1H, t, J = 7.8 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 176.8, 143.4, 140.3, 138.9, 135.5, 135.1, 133.6, 133.4, 132.8, 131.9, 131.8, 130.5, 130.2, 130.0, 127.9, 126.1, 125.9 (q, 3JC–F = 3.6 Hz), 125.6, 123.7 (q, 1JC–F = 273 Hz), 119.8, 98.8, 93.9, 93.0. (since the aromatic region is crowded, one quartet signal with 13C–19F coupling could not be identified with certainty). FTIR νmax (ATR, film)/cm–1 2173, 1639, 1323, 1310, 1288, 1224, 1170, 1128, 1047, 1016, 982. HRMS (ESI+) calcd for C20H10F3INaO [M + Na]+, 472.9621; found, 472.9623.

3-(8-Iodonaphthalen-1-yl)-1-(thiophen-2-yl)prop-2-yn-1-one (12f)

Compound 12f was obtained from alcohol 18f (20 mg, 0.051 mmol) using MnO2 (105 mg, 1.025 mmol) and acetone (2 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9) to afford pure 12f (10.5 mg, 53% yield) as a bright orange-yellow oil. R = 0.41 (EtOAc/hexanes = 1:7). 1H NMR (400 MHz; CDCl3) δ: 8.30 (1H, d, J = 7.3 Hz), 8.16 (1H, dd, J = 3.8, 1.2 Hz), 8.05 (1H, dd, J = 7.2, 0.9 Hz), 7.92 (1H, dd, J = 8.2, 1.3 Hz), 7.87 (1H, dd, J = 8.1, 1.1 Hz), 7.73 (1H, dd, J = 5.0, 1.2 Hz), 7.48 (1H, t, J = 7.7 Hz), 7.21–7.14 (2H, m). 13C{1H} NMR (100 MHz; CDCl3) δ: 169.9, 145.1, 143.2, 138.7, 135.5, 135.2, 135.0, 133.0, 132.7, 130.4, 128.5, 127.8, 125.6, 120.0, 98.6, 93.1, 91.1. FTIR νmax (ATR, film)/cm–1 2178, 1610, 1514, 1410, 1363, 1301, 1231, 1051, 949. HRMS (ESI+) calcd for C17H10IOS [M + H]+, 388.9492; found, 388.9495.

1-(Furan-2-yl)-3-(8-iodonaphthalen-1-yl)prop-2-yn-1-one (12g)

Product 12g was obtained from alcohol 18g (19.5 mg, 0.052 mmol) using MnO2 (106 mg, 1.04 mmol) and acetone (2.0 mL) according to General Procedure B. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:7 → 1:5) to afford pure 12g (17.4 mg, 90% yield) as a dark red oil. R = 0.42 (EtOAc/hexanes = 1:4). 1H NMR (400 MHz; CDCl3) δ: 8.31 (1H, dd, J = 7.4, 1.2 Hz), 8.06 (1H, dd, J = 7.3, 1.4 Hz), 7.94 (1H, dd, J = 8.2, 1.3 Hz), 7.88 (1H, dd, J = 8.2, 1.1 Hz), 7.71 (1H, dd, J = 1.6, 0.7 Hz), 7.58 (1H, dd, J = 3.6, 0.6 Hz), 7.49 (1H, d, J = 8.0, 7.4 Hz), 7.17 (1H, t, J = 7.7 Hz), 6.62 (1H, dd, J = 3.6, 1.7 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 164.8, 153.4, 148.1, 143.2, 138.9, 135.1, 133.1, 132.8, 130.4, 127.8, 125.6, 121.5, 120.0, 112.8, 98.4, 93.0, 91.2. FTIR νmax (ATR, film)/cm–1 2365, 2179, 1624, 1461, 1393, 1306, 985. HRMS (ESI+) calcd for C17H9INaO2 [M + Na]+, 394.9539; found, 394.9526.

General Procedure C for the Syntheses of Fluoranthenes

In a 25 mL, round-bottomed flask, a 1-iodo-8-alkynylnaphthalene derivative (1.0 equiv) was dissolved in 1.0 mL of 1,4-dioxane at 23 °C under N2. To this solution 2-furylboronic acid (19, 2.0 equiv), K3PO4 (3.0 equiv), and Pd(PPh3)4 (5 mol %) were added. Afterward, 1.0 mL of 1,4-dioxane and 1.0 mL of H2O were added along the walls of the flask. The resulting reaction mixture was heated to 100 °C in an oil bath and stirred under reflux for 3–6 h. The reaction mixture was cooled to 23 °C and quenched with H2O (5 mL). The aqueous phase was extracted with EtOAc (3 × 10 mL). The combined organic phase was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash column chromatography on SiO2.

(8-Hydroxyfluoranthen-7-yl)(phenyl)methanone (15a)

Fluoranthene product 15a was synthesized using alkyne 12a (18.5 mg, 0.048 mmol), 2-furylboronic acid (19, 10.8 mg, 0.096 mmol), K3PO4 (30.8 mg, 0.145 mmol), and Pd(PPh3)4 (2.8 mg, 0.0024 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19 → 1:9 → 1:4) to afford pure 15a (14.4 mg, 92% yield) as a yellow-green amorphous solid. R = 0.52 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.83 (1H, s), 7.98 (3 H, app t, J = 7.0 Hz), 7.88 (1H, d, J = 7.0 Hz), 7.76 (1H, d, J = 8.2 Hz), 7.69 (1H, d, J = 8.1 Hz), 7.63–7.54 (2H, m), 7.39 (2H, t, J = 7.8 Hz), 7.17 (1H, t, J = 7.7 Hz), 7.09 (1H, d, J = 8.6 Hz), 6.78 (1H, d, J = 7.2 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 199.3, 158.0, 139.4, 138.3, 135.9, 135.7, 134.1, 132.54, 132.52, 130.7, 129.9, 129.0, 128.0, 127.7, 127.5, 126.4, 126.3, 126.1, 125.7, 119.5, 116.5. FTIR νmax (ATR, film)/cm–1 3359, 1653, 1581, 1449, 1440, 1395, 1316, 1286, 1226, 815, 773. HRMS (ESI−) calcd for C23H13O2 [M – H]−, 321.0921; found, 321.0917.

(8-Hydroxyfluoranthen-7-yl)(4-methoxyphenyl)methanone (15b)

Fluoranthene product 15b was synthesized using alkyne 12b (28.5 mg, 0.070 mmol), 2-furylboronic acid (19, 15.5 mg, 0.14 mmol), K3PO4 (44 mg, 0.21 mmol), and Pd(PPh3)4 (4.0 mg, 0.0035 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:1) to afford pure 15b (17.8 mg, 73% yield) as a brown oil. R = 0.37 (EtOAc/hexanes = 1:2); 0.71 (EtOAc/hexanes = 1:1). 1H NMR (400 MHz; CDCl3) δ: 8.47 (1H, s), 7.97–7.93 (3H, m), 7.87 (1H, d, J = 6.9 Hz), 7.75 (1H, d, J = 8.2 Hz), 7.70 (1H, d, J = 8.1 Hz), 7.60 (1H, dd, J = 8.0, 7.0 Hz), 7.24 (1H, t, J = 7.7 Hz), 7.06 (1H, d, J = 8.2 Hz), 6.92 (1H, d, J = 7.2 Hz), 6.85 (2H, d, J = 8.9 Hz), 3.83 (3H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 197.3, 164.6, 157.3, 139.1, 136.0, 135.7, 133.1, 132.6, 132.4, 130.9, 128.0, 127.8, 127.3, 126.2, 125.9, 125.7, 120.1, 119.4, 116.3, 114.3, 114.1, 55.7. FTIR νmax (ATR, film)/cm–1 3317 (br), 1643, 1594, 1439, 1262, 1159. HRMS (ESI−) calcd for C24H15O3 [M – H]−, 351.1027; found, 351.1028.

Benzo[d][1,3]dioxol-5-yl(8-hydroxyfluoranthen-7-yl)methanone (15c)

Fluoranthene product 15c was synthesized using alkyne 12c (24.0 mg, 0.056 mmol), 2-furylboronic acid (19, 12.6 mg, 0.113 mmol), K3PO4 (36 mg, 0.17 mmol), and Pd(PPh3)4 (3.3 mg, 0.0028 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:4 → 1:3 → 1:2) to afford pure 15c (18.6 mg, 90% yield) as a yellow-brown oil.

In another experiment, the reaction between alkyne 12c (16.0 mg, 0.038 mmol) and furan-2-boronic acid pinacol ester (14.6 mg, 0.075 mmol) in the presence of K3PO4 (24.2 mg, 0.114 mmol) and Pd(PPh3)4 (2.2 mg, 0.0019 mmol) following General Procedure C afforded pure hydroxyfluoranthene 15c (12.4 mg) in 89% yield. R = 0.36 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.17 (1H, br s), 7.92 (1H, d, J = 8.3 Hz), 7.87 (1H, d, J = 6.8 Hz), 7.76 (1H, d, J = 8.2 Hz), 7.73 (1H, d, J = 8.1 Hz), 7.60 (1H, dd, J = 8.2, 6.9 Hz), 7.53 (2H, m), 7.30 (1H, dd, J = 8.1, 7.2 Hz), 7.04 (2H, t, J = 7.3 Hz), 6.70 (1H, d, J = 8.2 Hz), 6.05 (2H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 196.8, 156.8, 152.9, 148.6, 139.0, 136.0, 135.7, 132.64, 132.59, 132.5, 129.9, 128.3, 128.0, 127.8, 127.4, 126.3, 125.6, 125.5, 120.4, 119.5, 116.2, 109.4, 108.4, 102.2. FTIR νmax (ATR, film)/cm–1 3327, 1648, 1599, 1583, 1503, 1485, 1441, 1396, 1288, 1263, 1247, 1096, 1038, 815, 773. HRMS (ESI+) calcd for C24H15O4 [M + H]+, 367.0965; found, 367.0963.

(4-Chlorophenyl)(8-hydroxyfluoranthen-7-yl)methanone (15d)

Fluoranthene product 15d was synthesized using alkyne 12d (20 mg, 0.048 mmol), 2-furylboronic acid (19, 10.7 mg, 0.096 mmol), K3PO4 (30.6 mg, 0.144 mmol), and Pd(PPh3)4 (2.8 mg, 0.0024 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:9 → 1:5) to afford pure 15d (11.8 mg, 69% yield) as a brown oil. R = 0.53 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.53 (1H, s), 7.97 (1H, d, J = 8.3 Hz), 7.92–7.87 (3H, m), 7.77 (1H, d, J = 8.2 Hz), 7.73 (1H, d, J = 8.1 Hz), 7.61 (1H, dd, J = 8.2, 6.9 Hz), 7.38–7.35 (2H, m), 7.25 (1H, dd, J = 8.1, 7.2 Hz), 7.07 (1H, d, J = 8.3 Hz), 6.86 (1H, d, J = 7.2 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 197.7, 157.6, 140.6, 139.2, 136.5, 135.8, 135.4, 132.64, 132.55, 132.0, 131.9, 129.9, 129.4, 128.1, 127.73, 127.67, 126.5, 126.3, 125.9, 119.7, 116.5. FTIR νmax (ATR, film)/cm–1 3361 (br), 1654, 1584, 1439, 1398, 1310, 1286, 1226, 1091. HRMS (ESI-) calcd for C23H1235ClO2 [M – H]−: 355.0531; found, 355.0532; calcd for C23H1237ClO2 [M – H]−, 357.0502, found 357.0502.

(8-Hydroxyfluoranthen-7-yl)(4-(trifluoromethyl)phenyl)methanone (15e)

Fluoranthene product 15e was synthesized using alkyne 12e (13.0 mg, 0.029 mmol), 2-furylboronic acid (19, 6.5 mg, 0.058 mmol), K3PO4 (18.5 mg, 0.087 mmol), and Pd(PPh3)4 (1.7 mg, 0.0015 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:5) to afford pure 15e (5.9 mg, 52% yield) as a yellow oil. R = 0.49 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.62 (1H, br s), 8.07 (2H, d, J = 8.2 Hz), 8.02 (1H, br d, J = 7.9 Hz), 7.90 (1H, d, J = 6.8 Hz), 7.78 (1H, d, J = 8.0 Hz), 7.73 (1H, d, J = 8.1 Hz), 7.67–7.61 (3H, m), 7.20 (1H, app t, J = 7.7 Hz), 7.10 (1H, br d, J = 7.2 Hz), 6.78 (1H, d, J = 7.2 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 197.9, 157.9, 141.0, 140.1, 140.0, 139.3, 135.7, 135.5, 135.3, 135.0, 132.8, 132.5, 130.9, 130.8, 129.9, 128.2, 127.8, 127.6, 126.7, 126.6, 126.0 (q, 3JC–F = 3.7 Hz), 125.8, 119.8, 119.0, 116.6. (Since the aromatic region is crowded, two quartet signals with 13C–19F couplings could not be identified with certainty). 19F{1H} NMR (376 MHz; CDCl3) δ: −62.0. FTIR νmax (ATR, film)/cm–1 3380 (br), 2922, 2852, 1582, 1440, 1324, 1285, 1172, 1132, 1110. HRMS (ESI−) calcd for: C24H12F3O2 [M – H]−, 389.0795; found, 389.0794.

(8-Hydroxyfluoranthen-7-yl)(thiophen-2-yl)methanone (15f)

Fluoranthene product 15f was synthesized using alkyne 12f (17.0 mg, 0.044 mmol), 2-furylboronic acid (19, 9.9 mg, 0.088 mmol), K3PO4 (28 mg, 0.13 mmol), and Pd(PPh3)4 (2.5 mg, 0.0022 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:5 → 1:3) to afford pure 15f (13.1 mg, 91% yield) as a dark yellow solid. R = 0.48 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 7.99 (1H, br s), 7.94 (1H, d, J = 8.1 Hz), 7.87 (1H, d, J = 6.9 Hz), 7.76 (3H, m), 7.61 (2H, m), 7.32 (1H, dd, J = 8.1, 7.2 Hz), 7.14 (1H, d, J = 7.1 Hz), 7.05 (1H, d, J = 8.1 Hz), 6.95 (1H, dd, J = 4.8, 3.9 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 190.1, 156.4, 144.0, 138.9, 137.4, 136.0, 135.9, 135.7, 132.8, 132.6, 130.0, 128.7, 128.1, 127.8, 127.5, 126.4, 125.8, 125.5, 120.4, 119.6, 116.2. FTIR νmax (ATR, film)/cm–1 3332 (br), 1625, 1582, 1509, 1453, 1439, 1408, 1396, 1379, 1354, 1309, 1288, 1228, 1210, 1055, 1039, 904. HRMS (ESI−) calcd for C21H11O2S [M – H]−, 327.0485; found, 327.0486.

Furan-2-yl(8-hydroxyfluoranthen-7-yl)methanone (15g)

Fluoranthene product 15g was synthesized using alkyne 12g (16.0 mg, 0.043 mmol), 2-furylboronic acid (19, 9.6 mg, 0.086 mmol), K3PO4 (27.4 mg, 0.13 mmol), and Pd(PPh3)4 (2.5 mg, 0.0022 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:4 → 1:3 → 1:2) to afford pure 15g (9.7 mg, 72% yield) as a bright yellow solid. R = 0.43 (EtOAc/hexanes = 1:2). 1H NMR (400 MHz; CDCl3) δ: 8.49 (1H, br s), 7.96 (1H, d, J = 8.3 Hz), 7.87 (1H, d, J = 6.9 Hz), 7.79 (1H, d, J = 8.2 Hz), 7.77 (1H, d, J = 8.2 Hz), 7.62 (1H, dd, J = 8.2, 6.9 Hz), 7.54 (1H, s), 7.39–7.30 (2H, m), 7.05 (1H, d, J = 8.3 Hz), 6.95 (1H, d, J = 7.1 Hz), 6.54 (1H, dd, J = 3.6, 1.6 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 184.9, 157.6, 147.8, 139.4, 136.1, 136.0, 132.7, 132.5, 130.0, 128.1, 127.9, 127.5, 126.5, 126.3, 125.0, 121.9, 119.6, 116.2, 114.5, 113.3, 112.7. FTIR νmax (ATR, film)/cm–1 3305, 1636, 1584, 1459, 1439, 1395, 1314, 1281, 1054, 1023, 817, 772. HRMS (ESI+) Calcd for C21H13O3 [M + H]+, 313.0860; found, 313.0855.

1-(8-Hydroxyfluoranthen-7-yl)ethan-1-one (15h)

Fluoranthene product 15h was synthesized using alkyne 12h (20.5 mg, 0.063 mmol), 2-furylboronic acid (19, 14.0 mg, 0.125 mmol), K3PO4 (40.1 mg, 0.189 mmol), and Pd(PPh3)4 (3.6 mg, 0.0032 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:5) to afford pure 15h (6.4 mg, 38% yield) as an orange solid. R = 0.36 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 9.71 (1H, br s), 7.97 (1H, d, J = 7.2 Hz), 7.91 (2H, dd, J = 8.1, 7.2 Hz), 7.86 (1H, d, J = 6.9 Hz), 7.82 (1H, d, J = 8.2 Hz), 7.63 (2H, ddd, J = 8.2, 7.1, 2.4 Hz), 6.99 (1H, d, J = 8.3 Hz), 2.91 (3H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 206.1, 157.7, 138.8, 135.9, 135.7, 132.7, 132.5, 130.1, 128.3, 127.9, 126.8, 126.5, 125.5, 121.0, 119.7, 116.6, 31.1. FTIR νmax (ATR, film)/cm–1 3321, 1685, 1580, 1438, 1396, 1285, 1223, 814, 772. HRMS (ESI−) calcd for C18H12O2 [M]−, 260.0843; found, 260.0859.

8-Hydroxyfluoranthene-7-carboxamide (15i)

Fluoranthene product 15i was synthesized using alkyne 12i (30.0 mg, 0.093 mmol), 2-furylboronic acid (19, 20.9 mg, 0.187 mmol), K3PO4 (59.2 mg, 0.28 mmol), and Pd(PPh3)4 (5.4 mg, 0.0047 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:2 → 1:1) to afford pure 15i (13.0 mg, 53% yield) as a light yellow solid. Mp: 201.5–203.0 °C. R = 0.61 (EtOAc only). 1H NMR (400 MHz; CDCl3) δ: 10.53 (1H, br s), 8.45 (1H, d, J = 7.2 Hz), 7.91 (1H, d, J = 8.3 Hz), 7.90 (1H, d, J = 8.2 Hz), 7.85 (1H, d, J = 6.9 Hz), 7.81 (1H, d, J = 6.9 Hz), 7.63 (2H, m), 7.02 (1H, d, J = 8.4 Hz), 6.48 (2H, br s). 13C{1H} NMR (100 MHz; CDCl3) δ: 171.8, 159.6, 137.0, 136.0, 135.6, 132.6, 132.5, 130.3, 128.5, 128.4, 127.8, 126.4, 126.2, 124.8, 119.6, 116.9, 113.2. FTIR νmax (ATR, film)/cm–1 3454, 3352, 3194, 1650, 1598, 1440, 1396, 1280, 1228, 816, 773. HRMS (ESI+) calcd for C17H12NO2 [M + H]+, 262.0863; found, 262.0863.

2-(8-(Phenylethynyl)naphthalen-1-yl)furan (13j)

Compound 13j was synthesized using 12j (33.4 mg, 0.094 mmol), 2-furylboronic acid (19, 21.1 mg, 0.184 mmol), K3PO4 (60.1 mg, 0.282 mmol), and Pd(PPh3)4 (5.5 mg, 0.0047 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19 → 1:9 → 1:7) to afford pure 13j (25.7 mg, 92% yield) as an orange oil. Rf = 0.54 (EtOAc/hexanes = 1:19). 1H NMR (400 MHz; CDCl3) δ: 8.05–7.72 (4H, m), 7.56 (1H, dd, J = 6.9, 1.0 Hz), 7.51–7.45 (3H, m), 7.34 (2H, dd, J = 6.9, 2.0 Hz), 7.30–7.26 (2H, m), 6.56 (1H, d, J = 3.3 Hz), 6.45 (1H, dd, J = 3.0, 1.9 Hz). 13C{1H} NMR (100 MHz; CDCl3) δ: 154.7, 142.3, 135.0, 134.6, 132.0, 131.9, 131.2, 130.4, 129.4, 129.2, 128.0, 127.8, 125.6, 125.4, 124.1, 120.7, 111.9, 109.0, 95.0, 88.8. FTIR νmax (ATR, film)/cm–1: 3055, 2924, 1597, 1568, 1508, 1489, 1442, 1426, 1219, 1207, 1076, 1029, 953, 914, 886, 806, 755. HRMS (APCI+) calcd, C22H15O [M + H]+ 295.1117; found, 295.1106.

7-Phenylfluoranthen-8-ol (15j)

Compound 13j (7.8 mg, 0.026 mmol) was dissolved in mesitylene (0.9 mL) in a 10 mL round-bottomed flask. The resulting yellow solution was heated at 130 °C in an oil bath for 43 h. Then the reaction mixture was allowed to cool down to 23 °C and quenched with H2O. The aqueous phase was extracted four times with CH2Cl2. The combined organic layer was dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19 → 1:9) to afford pure 15j (4.3 mg, 55% yield) as an orange-yellow solid. Rf = 0.41 (EtOAc/hexanes = 1:4). 1H NMR (400 MHz; CDCl3) δ: 7.87 (1H, d, J = 6.9 Hz), 7.83 (1H, d, J = 8.1 Hz), 7.75 (1H, d, J = 8.1 Hz), 7.73 (1H, d, J = 8.0 Hz), 7.67–7.55 (6H, m), 7.30 (1H, t, J = 7.6 Hz), 7.03 (1H, d, J = 8.2 Hz), 6.74 (1H, d, J = 7.1 Hz), 4.98 (1H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 153.1, 138.8, 136.73, 136.71, 134.4, 133.0, 132.6, 130.4, 130.1, 130.0, 129.2, 128.1, 127.8, 126.9, 125.8, 124.9, 122.7, 122.1, 119.1, 114.2. FTIR νmax (ATR, film)/cm–1: 3508, 3432, 3058, 2923, 1603, 1443, 1267, 1207, 1198, 1173, 816, 774, 712. HRMS (APCI−) calcd: C22H13O– [M – H]−, 293.0972; found, 293.0977.

7-(4-Nitrophenyl)fluoranthen-8-ol (15k)

Fluoranthene product 15k was synthesized using alkyne 12k (16.3 mg, 0.041 mmol), 2-furylboronic acid (19, 9.2 mg, 0.0.082 mmol), K3PO4 (26.0 mg, 0.123 mmol), and Pd(PPh3)4 (2.4 mg, 0.0020 mmol) according to General Procedure C. The crude product was purified by flash column chromatography (SiO2; EtOAc/hexanes = 1:19 → 1:9) to afford pure 15k (3.5 mg, 25% yield) as an orange solid. R = 0.26 (EtOAc/hexanes = 1:3). 1H NMR (400 MHz; CDCl3) δ: 8.49 (2H, d, J = 8.7 Hz), 7.90 (1H, d, J = 6.9 Hz), 7.86 (1H, d, J = 8.2 Hz), 7.81–7.74 (4H, m), 7.63 (1H, dd, J = 8.2, 6.9 Hz), 7.33 (1H, dd, J = 8.1, 7.2 Hz), 6.99 (1H, d, J = 8.1 Hz), 6.75 (1H, d, J = 7.1 Hz), 4.84 (1H, s). 13C{1H} NMR (100 MHz; CDCl3) δ: 152.4, 148.2, 142.6, 138.6, 136.2, 136.0, 133.2, 132.9, 131.7, 130.1, 128.2, 127.8, 127.5, 126.2, 124.8, 123.2, 122.71, 122.68, 119.5, 114.7. FTIR νmax (ATR, film)/cm–1 3463, 2924, 1600, 1516, 1478, 1391, 1334, 1080, 853. HRMS (ESI−) Calcd for C22H12NO3 [M – H]−, 338.0823; found, 338.0821.

Crystallization of Fluoranthene 15i for Single-Crystal X-ray Analysis

Compound 15i (6 mg) was dissolved in CH2Cl2 (1.0 mL) in a 2 mL vial. This vial was placed in a 20 mL scintillation vial containing pentane (3 mL), and the outer vial was sealed with a screw cap. Crystals were obtained within 1 week at room temperature.