Visible-Light-Promoted Synthesis of Dibenzofuran Derivatives

Article abstract of DOI:10.1021/acs.joc.7b02796

Dibenzofurans are naturally occurring molecules that have received considerable attention for a variety of practical applications, such as in pharmaceuticals and electronic materials. Herein, an efficient and eco-friendly method for the synthesis of dibenzofuran derivatives via intramolecular C-O bond formation, which involves the in situ production of a diazonium salt, is described. The transformation requires a diazotizing agent and is promoted by the use of an organic photosensitizer under visible-light irradiation.

Full text of DOI:10.1021/acs.joc.7b02796

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Article
Visible-Light Promoted Synthesis of Dibenzofuran Derivatives
Ji Young Cho, Geum-bee Roh, and Eun Jin Cho
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b02796 • Publication Date (Web): 13 Dec 2017
Downloaded from http://pubs.acs.org on December 14, 2017
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Visible-Light Promoted Synthesis of Dibenzofuran Derivatives
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Ji Young Cho, Geumꢀbee Roh, and Eun Jin Cho*
Department of Chemistry, ChungꢀAng University
84 Heukseokꢀro, Dongjakꢀgu, Seoul 06974, Republic of Korea
*Eꢀmail: ejcho@cau.ac.kr
Abstract: Dibenzofurans are naturallyꢀoccurring molecules that have received considerable
attention for a variety of practical applications, such as in pharmaceuticals and electronic
materials. Herein, an efficient and ecoꢀfriendly method for the synthesis of dibenzofuran
derivatives via intramolecular CꢀO bond formation, which involves the in situ production of a
diazonium salt, is described. The transformation requires a diazotizing agent and is promoted
by the use of an organic photosensitizer under visibleꢀlight irradiation.
INTRODUCTION
Dibenzofuran structural motifs are widely found in natural products and are used in
pharmaceuticals, as well as in material sciences, owing to their unique properties, such as
weak biochemical stress response and high heat resistance.1, 2 Accordingly, a variety of
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functional molecules contain the dibenzofuran skeleton, such as biologically active
cotonefurans3, furobufen4, DB036825, fortuneanoside L6, and the photoelectronic materials
used in phosphorescent organic lightꢀemitting diodes (PhOLEDs)7 (Figure 1).
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Figure 1. Examples of functional molecules containing the dibenzofuran structural motif.
Due to their importance, several methodologies for the construction of dibenzofuran
derivatives have been developed based on numerous intermolecular and intramolecular
reactions. Approaches based on intramolecular ring closure through formation of CꢀC bonds
using functionalized diaryl ethers8 [Scheme 1(a)] and formation of CꢀO bonds using
functionalized biaryls9 have been extensively developed [Scheme 1(b)]. Intramolecular CꢀO
bond formation by CꢀH activation is particularly attractive in terms of efficiency as this
approach can furnish various kinds of dibenzofuran motifs from lessꢀfunctionalized starting
substrates.9d, 9e Nonetheless, despite the efficiency, these methods are often restricted in that
they require harsh reaction conditions and the use of transitionꢀmetal catalysts such as
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copper9c and palladium.9d, 9e Therefore, the search for synthetic methods employing mild
reaction conditions is ongoing.
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Scheme 1. Intramolecular synthesis of dibenzofuran derivatives
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Diazonium salts are easily prepared and handled and have been widely used as effective
substrates in a variety of organic transformations.10 Recently, we utilized diazonium salts
generated in situ from amino substrates using nitrite sources for the synthesis of various
heteroaromatic compounds.11 With the continued interest in the use of diazonium salts for the
synthesis of valuable polycyclic heteroaromatic compounds, we attempted to develop a
practical dibenzofuran synthetic method utilizing 2ꢀ(2′ꢀaminoaryl)phenol derivatives through
in situ diazotization of the amino group, followed by intramolecular CꢀO cyclization under
mild conditions.
RESULTS AND DISCUSSION
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Table 1. Optimization studies with 1aa
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b
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aReaction scale: 0.1 mmol; photosensitizer was used under 23 W CFL; yields were
1
d
determined by H NMR spectroscopy using 4ꢀchloroanisole as the internal standard.; 77%
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after 36 h.
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The investigation was initiated by using 2ꢀ(2′ꢀaminophenyl)phenol (1a) as the model
substrate with tertꢀbutyl nitrite (tBuONO) as a diazotizing agent in 2,2,2ꢀtrifluroroethanol
(TFE) to construct dibenzofuran (2a) (Table 1). As expected, the reaction did not proceed at
all in the absence of tBuONO (Table 1, entry 1) but provided 2a through in situ diazotization
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t
followed by simple nucleophilic substitution in the presence of BuONO, despite the
unsatisfactory yield (Table 1, entry 2). Increasing the reaction temperature to 60 °C did not
improve the efficiency of the process (Table 1, entry 3). To improve the efficiency of
intramolecular CꢀO bond formation, the introduction of visibleꢀlight photocatalysis was
proposed, where photocatalysis have recently emerged as a powerful synthetic tool owing to
their environmental benignity and mechanistic versatility in promoting a large number of
organic reactions [Scheme 1(c)].12 Notably, diazonium salts have been successfully utilized
in a variety of visibleꢀlight promoted photocatalytic reactions.10b, 11a, 11c, 11d First, the most
widely used photosensitizers [Ru(bpy)3]Cl2 and facꢀIr(ppy)3 (bpy = 2,2'ꢀbipyridine; ppy = 2ꢀ
phenlypyridine) were employed under visibleꢀlight irradiation using a compact fluorescent
lamp (CFL, 23W); however, no improvement of the reaction efficiency was achieved (Table
1, entries 4 and 5). Several types of organic photosensitizers were also explored, including
Eosin Y and triphenylpyrylium tetrafluoroborate (TPPT) derivatives (Table 1, entries 6−12).
Notably, the use of an organic photosensitizer can minimize the drawbacks associated with
transition metals, including toxicity and threshold values in pharmaceutical products.13 The
use of 2,4,6ꢀtris(4ꢀfluorophenyl)pyrylium tetrafluoroborate (T(pꢀF)PPT) successfully
increased the reaction efficiency to provide 2a in 64% yield (Table 1, entry 8), plausibly due
to the high oxidizing potential of its photoexcited state (E*[T(pꢀF)PPT*/T(pꢀF)PPT ꢀ]= +2.28
V vs. SCE)14 and good solubility in TFE. The reaction atmosphere did not affect the reactivity
in that the reactions under argon and oxygen provided similar yields of 2a. Changing the
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nitrite source and solvent system did not improve the reaction efficiency (Table 1, entries
13−22). After extensive screening of the stoichiometry of the reagents and reaction
concentration (Table 1, entries 23−30), the reaction of 1a provided the best result, furnishing
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t
2a in 80% yield with 1 mol% of T(pꢀF)PPT, 1.5 equiv. BuONO, and 0.02 M TFE (Table 1,
entry 29).
Using the optimized conditions, the scope of various 2ꢀ(2′ꢀaminoaryl)phenol substrates (1)
was then investigated (Table 2). One advantage of this approach is that regardless of the
substituent pattern on the two aryl rings (aniline or phenol rings) of the monoꢀsubstituted
substrate, the same product could be obtained in similar yields so that the moreꢀeasily
prepared substrate could be used. The reactions of substrates with the substituent located at
different positions generated the same dibenzofuran derivative (Table 2, entries 2 and 3, 1b
vs. 1c) with nearly equal efficiencies, confirming that the efficiency of the approach was not
significantly altered by the position of the aryl ring substituents.15 The reactions of substrates
containing substituents on both rings (1g and 1h) also proceeded to give the corresponding
dibenzofuran derivatives (Table 2, entries 7 and 8). Heteroatomꢀcontaining substrates also
worked well for the transformation. A pyridylꢀcontaining substrate, 2ꢀ(3ꢀaminopyridinꢀ2ꢀ
yl)phenol (1i) smoothly underwent C−O cyclization to produce the tricyclic product 2i in 60%
yield (Table 2, entry 9). The reaction also produced nitrodibenzofurans (1%−5%) as side
products, through overreaction with the nitro group present in the reaction medium. Notably,
the reaction conditions were amenable to gramꢀscale reaction, where the product 2a was
prepared on a 6 mmolꢀscale with yield similar to that of the 0.5 mmolꢀscale reaction (Table 2,
entry 1).
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Table 2. Substrate scope for synthesis of dibenzofuran derivativesa
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aReaction scale: 0.5 mmol; bIsolated yield (products are generally volatile2); c6.0 mmolꢀscale.
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Substrates containing electron donating substituents generally underwent CꢀO cyclization
smoothly to give the corresponding dibenzofuran derivatives in good yields, whereas
reactions of substrates with electron withdrawing substituents provided lower yields of the
desired dibenzofurans. Other substrates with various electron withdrawing substituents such
as ꢀF, ꢀCl, ꢀBr, ꢀCF3, ꢀOCF3, ꢀCN, and ꢀNO2 were explored, but reactions showed lower
reactivity, providing low to moderate yields of the dibenzofuran products (Scheme 2).16
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Scheme 2. Reactions with substrates containing electron withdrawing substituentsa,b
aReaction scale: 0.5 mmol; Isolated yield (products are generally volatile2); DMF (0.1 M)
b
c
was used as a solvent due to the insolubility of 1p in TFE; dReaction yields at 60 oC.
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Scheme 3. Proposed reaction mechanism
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A plausible mechanism for the intramolecular CꢀO cyclization with 1a is shown in Scheme
t
3. In situ diazotization of 1a by BuONO produces the corresponding diazonium salt I. The
desired product 2a can be synthesized simply by nucleophilic substitution through either II or
II' [pathway (a)]17 where the driving force for the process is the formation of stable nitrogen
gas, as well as the tricyclic heterocycle, dibenzofuran. However, the process is very slow and
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not sufficiently efficient to generate a high yield of 2a, as described above (see entry 2 of
Table 1). The use of T(pꢀF)PPT as a photosensitizer under visibleꢀlight irradiation was found
herein to increase the reaction efficiency, indicating the involvement of another
photocatalytic process. The photoexcited state of T(pꢀF)PPT has a sufficiently high oxidizing
potential (E*[T(pꢀF)PPT*/T(pꢀF)PPTꢀ]= +2.28 V vs. SCE)14 to oxidize the phenolate of the
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intermediate II (approximately E1/2
=
−
0.07 ~ +1.04 V vs. SCE)18 with highly positive
driving force through a singleꢀelectronꢀtransfer process under visibleꢀlight irradiation,
providing the oxyradical intermediate III [pathway (b)]. Moreover, in pathway (b), formation
of the aryl radical from the diazonium salt moiety can be facilitated by single electron
reduction from T(pꢀF)PPTꢀ, regenerating T(pꢀF)PPT in the photocatalytic cycle. Subsequent
intramolecular CꢀO cyclization to give the desired product 2a.
In conclusion, a visibleꢀlightꢀpromoted method was developed for the synthesis of
dibenzofuran derivatives under mild reaction conditions. Intramolecular CꢀO bond formation
through the diazonium intermediate formed in situ from 2ꢀ(2′ꢀaminoaryl)phenol could be
facilitated by visibleꢀlight photocatalysis utilizing T(pꢀF)PPT as the photosensitizer. The high
excited oxidizing potential of T(pꢀF)PPT accounts for formation of the oxyradical
intermediate, leading to efficient CꢀO bond formation. Moreover, the practicality of the
process was demonstrated by producing various functionalized dibenzofuran derivatives,
even on the gramꢀscale.
EXPERIMENTAL SECTION
General Information. All reagents and solvents including tBuONO and 2,2,2ꢀ
trifluoroethanol (TFE) were purchased from SigmaꢀAldrich, Alfa Aesar, TCI, and Combi
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Blocks chemical companies. Flash column chromatography was performed using Merck
silica gel 60 (70ꢀ230 mesh). The 2'ꢀamino[1,1'ꢀbiphenyl]ꢀ2ꢀol derivatives and dibenzofuran
1
products were characterized by H NMR, 13C NMR, and FTꢀIR spectroscopy. NMR spectra
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were recorded on a Bruker 600 MHz instrument (600 MHz for H NMR and 151 MHz for
13C NMR). Copies of H and 13C NMR spectra can be found at the end of the Supporting
1
1
Information. H NMR experiments are reported in units, parts per million (ppm), and were
measured relative to residual chloroform (7.26 ppm) or residual DMSO (2.50 ppm) in the
deuterated solvent. 13C NMR spectra are reported in ppm relative to deuterochloroform
1
(77.23 ppm) or deuterated DMSO (39.52 ppm), and all were obtained with H decoupling.
Coupling constants were reported in Hz. FTꢀIR spectra were recorded on a Tensor 27 Bruker
FTꢀIR spectrometer. Mass spectral data of all unknown compounds were obtained from the
Korea Basic Science Institute (Daegu) on a Jeol JMS 700 high resolution mass spectrometer.
The mass analyzer type used for HRMS measurements is EIꢀquadrupole. Melting points of
unknown solid compounds were recorded on a Stuart SMP30 apparatus.
Experimental Details
1. Preparation of triphenylpyrylium tetrafluoroborate(TPPT) derivatives
All of triphenylpyrylium tetrafluoroborate (TPPT) derivatives were synthesized following a
reported procedure.19
2. Preparation of 2'-amino[1,1'-biphenyl]-2-ol derivatives (1a-1p)
For the synthesis of 1a-1p, we followed a slightly modified synthetic procedure that was
reported by our group for the synthesis of 2,2′ꢀdiaminobiaryls11d, the Ritter group for the
synthesis of 2ꢀ(2ꢀpyridinyl)aniline20, and the Yoshikai group for [1,1'ꢀbiphenyl]ꢀ2ꢀol9d.
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An ovenꢀdried 250 mL round bottom flask equipped with a magnetic stir bar was charged
with 2ꢀiodoaniline (10 mmol, 2.23 g) and (2ꢀhydroxyphenyl)boronic acid (12 mmol, 1.71 g)
in ethylene glycol dimethyl ether (18 mL) mixed with distilled water (18 mL). 5 mol%
Pd(PPh3)4 (0.5 mmol, 0.60 g) and K2CO3 (40 mmol, 5.53 g) were added to it. The round
bottom flask connected with a reflux column was placed in the oil bath and heated for 16 h at
120 °C. The progress of the reaction was monitored by TLC and gas chromatography. The
flask was cooled to room temperature, the reaction mixture was diluted with
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dichloromethane, and the aqueous phase was extracted with dichloromethane. The combined
organic layers were dried over anhydrous MgSO4, and concentrated in vacuo. The residue
was purified by silica gel flash column chromatography using hexane and ethyl acetate as the
eluent to give the desired product 1a (1.44 g, 78%). Other substrates 1b–1q are synthesized
similarly to the synthesis of 1a by SuzukiꢀMiyaura coupling process using the corresponding
substituted 2ꢀhaloanilines and (2ꢀhydroxyphenyl)boronic acid (on 5 or 10 mmol scale).
3. A Representative Experimental Procedure for the Synthesis of Dibenzofuran
derivatives (2a-2p)
An ovenꢀdried 50 mL round bottom flask with a magnetic stir bar was charged with the 2ꢀ(2′ꢀ
aminoaryl)phenol derivative (1, 0.5 mmol) and T(pꢀF)PPT (0.005 mmol, 2.3 mg) in 2,2,2ꢀ
t
trifluoroethanol (TFE) (25 mL, 0.02 M). BuONO (1.5 mmol, 99 µL) was added to the
t
solution, considering the purity of BuONO (90% purity). The flask was then irradiated with
visibleꢀlight using a CFL (23 W) at room temperature. The reaction progress was monitored
by TLC. After completion of the reaction, the solvent was evaporated and the reaction
mixture was purified by flash column chromatography to give the corresponding
dibenzofuran product 2.
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Analytic Data for 2'-Amino[1,1'-biphenyl]-2-ol Derivatives
2'-amino-[1,1'-biphenyl]-2-ol (1a):21 beige solid (10 mmol scale: 1.57 g, 85%); mp
92−94 °C; 1H NMR (600 MHz, CDCl3) δ 7.31 – 7.28 (m, 2H), 7.24 – 7.20 (m, 2H), 7.03 (d,
J = 8.4 Hz, 1H), 7.01 (ddd, J = 7.7, 7.5, 1.3 Hz, 1H), 6.96 (ddd, J = 7.5, 7.4, 1.2 Hz, 1H), 6.85
(d, J = 7.6 Hz, 1H), 3.76 (bs, 2H); 13C NMR (151 MHz, CDCl3) δ 153.9, 142.0, 132.0, 131.3,
129.7, 129.2, 126.3, 126.2, 121.4, 121.2, 118.3, 117.4; IR (neat) νmax = 3380, 3308, 3060,
1613, 1479, 753 cmꢀ1; Rf 0.57 (hexane/EtOAc, 2/1)
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2'-amino-5'-methyl-[1,1'-biphenyl]-2-ol (1b): pale yellow solid (0.64 g, 64%); mp
104−106 °C; 1H NMR (600 MHz, CDCl3) δ 7.32 (dd, J = 7.4, 1.7 Hz, 1H), 7.31 (ddd, J =
8.0, 7.5, 1.7 Hz, 1H), 7.08 (d, J = 1.4 Hz, 1H), 7.06 (dd, J = 8.0, 2.1 Hz, 1H) 7.05 (dd, J = 8.0,
1.3 Hz, 1H), 7.03 (ddd, J = 7.5, 7,4, 1.3 Hz, 1H), 6.80 (d, J = 8.0 Hz, 1H), 3.71 (bs, 2H), 2.32
(s, 3H); 13C NMR (151 MHz, CDCl3) δ 154.0, 139.1, 132.5, 131.3, 130.8, 129.7, 129.5,
126.9, 126.7, 121.3, 118.5, 117.8, 20.8; HRMS m/z calc. for C13H13NO [M+] 199.0997,
found 199.0999; IR (neat) νmax = 3381, 3301, 3027, 2919, 1602, 1483, 754 cmꢀ1; Rf 0.44
(hexane/EtOAc, 2/1)
2'-amino-5-methyl-[1,1'-biphenyl]-2-ol (1c): light brown solid (0.53 g, 53%); mp 95−96 °C;
1H NMR (600 MHz, CDCl3) δ 7.22 (d, J = 7.5 Hz, 1H), 7.21 (dd, J = 8.0, 7.6 Hz, 1H), 7.10
(d, J = 7.9 Hz, 1H), 7.09 (s, 1H), 6.95 (dd, J = 7.6, 7.5 Hz, 1H), 6.93 (d, J = 8.0 Hz, 1H),
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6.83 (d, J = 7.9 Hz, 1H), 3.79 (bs, 2H), 2.32 (s, 3H); C NMR (151 MHz, CDCl3) δ 151.6,
142.0, 131.9, 131.6, 130.5, 130.2, 129.0, 126.3, 126.0, 121.0, 118.0, 117.3, 20.7; HRMS m/z
calc. for C13H13NO [M+] 199.0997, found 199.0998; IR (neat) νmax = 3381, 3310, 3026,
2920, 1614, 1491, 907, 818, 752 cmꢀ1; Rf 0.44 (hexane/EtOAc, 2/1)
2'-amino-4'-methoxy-[1,1'-biphenyl]-2-ol (1d):21 light brown solid (0.51 g, 47%); 1H NMR
(600 MHz, CDCl3) δ 7.25 – 7.20 (m, 2H), 7.08 (d, J = 8.4 Hz, 1H), 6.97 (d, J = 7.8 Hz, 1H)
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6.96 (dd, J = 7.5, 7.4 Hz, 1H), 6.47 (dd, J = 8.4, 2.5 Hz, 1H), 6.33 (d, J = 2.5 Hz, 1H), 3.74 (s,
3H); 13C NMR (151 MHz, CDCl3) δ 215.1, 160.5, 153.7, 143.6, 132.7, 131.3, 129.2, 125.9,
121.2, 118.2, 117.6, 106.4, 102.6, 55.4; IR (neat) νmax = 3378, 2936, 2835, 1605, 1480, 1203,
728 cmꢀ1; Rf 0.53 (hexane/EtOAc, 1/1)
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1-(6-amino-2'-hydroxy-[1,1'-biphenyl]-3-yl)ethan-1-one (1e): yellow solid (0.83 g, 73%);
1
mp 165−166 °C; H NMR (600 MHz, CDCl3) δ 7.85 (dd, J = 8.3, 2.0 Hz, 1H), 7.80 (d, J =
2.0 Hz, 1H), 7.33 (ddd, J = 8.4, 7.2, 1.5 Hz, 1H), 7.25 (dd, J = 7.5, 1.5 Hz, 1H), 7.04 (d, J =
8.3 Hz, 1H), 7.03 (dd, J = 7.2, 7.5 Hz, 1H), 6.82 (d, J = 8.4 Hz, 1H), 5.84 (bs, 1H), 4.27 (bs,
13
2H), 2.51 (s, 3H); C NMR (151 MHz, CDCl3) δ 196.8, 153.5, 148.4, 133.1, 131.3, 130.4,
130.2, 129.1, 124.5, 122.6, 121.6, 117.3, 115.5, 26.4; HRMS m/z calc. for C14H13NO2 [M+]
227.0946, found 227.0945; IR (neat) νmax = 3367, 1615, 1585, 1449, 1248, 729 cmꢀ1; Rf 0.42
(hexane/EtOAc, 1/1)
methyl 6-amino-2'-hydroxy-[1,1'-biphenyl]-3-carboxylate (1f):22 brown solid (0.46 g,
38%); 1H NMR (600 MHz, CDCl3) δ 7.82 (d, J = 1.7 Hz, 1H), 7.79 (dd, J = 8.4, 1.7 Hz, 1H),
7.24 (dd, J = 7.5, 7.0 Hz, 1H), 7.18 (d, J = 7.3 Hz, 1H), 6.99 – 6.94 (m, 2H), 6.70 (d, J = 8.4
Hz, 1H), 4.68 (bs, 3H), 3.80 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 167.3, 153.5, 148.3,
133.6, 131.3, 131.0, 129.8, 124.7, 123.2, 121.2, 120.5, 117.1, 115.4, 51.9; IR (neat) νmax
3380, 2951, 1692, 1616, 1436, 1245 cmꢀ1; Rf 0.59 (hexane/EtOAc, 1/1)
=
2'-amino-5-fluoro-5'-methyl-[1,1'-biphenyl]-2-ol (1g): beige solid (0.36 g, 33%); mp
1
92−94 °C; H NMR (600 MHz, CDCl3) δ 7.70 (bs, 1H), 7.08 (d, J = 2.9 Hz, 1H), 7.07 (s,
1H), 7.04 (dd, J = 9.2, 2.6 Hz, 1H), 7.02 – 6.95 (m, 1H), 6.81 (d, J = 8.5 Hz, 1H), 3.75 (bs,
2H), 2.32 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 157.4 (d, 1JCꢀF = 238.6 Hz), 150.1, 138.7,
132.4, 131.3, 130.0, 127.8 (d, 3JCꢀF = 7.6 Hz), 126.5, 119.7 (d, 3JCꢀF = 7.6 Hz), 118.2, 117.1 (d,
2
2JCꢀF = 22.7 Hz), 116.0 (d, JCꢀF = 22.7 Hz), 20.8; HRMS m/z calc. for C13H12FNO [M+]
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217.0903, found 217.0905; IR (neat) νmax = 3303, 1621, 1489, 1263, 1164 cmꢀ1; Rf 0.40
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(hexane/EtOAc, 2/1)
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2'-amino-5-fluoro-4'-methoxy-[1,1'-biphenyl]-2-ol (1h): offꢀwhite solid (0.24 g, 21%); H
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NMR (600 MHz, CDCl3) δ 7.13 (d, J = 8.5 Hz, 1H), 6.99 – 6.96 (m, 3H), 6.55 (dd, J = 8.5,
2.4 Hz, 1H), 6.42 (d, J = 2.4 Hz, 1H), 3.81 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 157.2 (d,
1JCꢀF = 238.6 Hz), 149.6 (d, 5JCꢀF = 2.1 Hz), 142.9, 132.5, 131.9 (d, 3JCꢀF = 10.6 Hz), 128.9 (d,
3JCꢀF = 12.6 Hz), 126.9 (d, 4JCꢀF = 7.8 Hz), 118.8 (d, 4JCꢀF = 8.4 Hz), 116.9 (d, 2JCꢀF = 22.8 Hz),
2
115.5 (d, JCꢀF = 22.8 Hz), 106.7, 102.9, 55.5; HRMS m/z calc. for C13H12FNO2 [M+]
233.0852, found 233.0854; IR (neat) νmax = 3312, 2935, 1616, 1482, 1263, 1168 cmꢀ1; Rf
0.50 (hexane/EtOAc, 1/1)
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2-(3-aminopyridin-2-yl)phenol (1i): yellow solid (0.47 g, 50%); mp 123−125 °C; H NMR
(600 MHz, CDCl3) δ 8.03 (dd, J = 4.6, 1.5 Hz, 1H), 7.88 (dd, J = 7.8, 1.6 Hz, 1H), 7.27 (ddd,
J = 7.7, 7.5, 1.6 Hz, 1H), 7.14 (dd, J = 8.1, 1.5 Hz, 1H), 7.09 – 7.06 (m, 2H), 6.92 (ddd, J =
7.8, 7.5 1.6 Hz, 1H), 4.08 (bs, 2H); 13C NMR (151 MHz, CDCl3) δ 157.5, 142.9, 140.8,
137.7, 130.4, 127.2, 125.1, 123.0, 120.9, 119.1, 118.5; HRMS m/z calc. for C11H10N2O [M+]
186.0793, found 186.0791; IR (neat) νmax = 3357, 3060, 1609, 1455, 1443, 757 cmꢀ1; Rf 0.41
(hexane/EtOAc, 2/1)
1
2'-amino-5'-fluoro-[1,1'-biphenyl]-2-ol (1j): brown viscous oil (0.60 g, 59%); H NMR
3
(600 MHz, CDCl3) δ 7.63 (bs, 1H), 7.33 (dd, J = 8.5 Hz, JHꢀF = 7.3 Hz, 1H), 7.29 (dd, J =
3
7.5, 1.7 Hz, 1H), 7.05 (d, JHꢀF = 8.1 Hz, 1H), 7.05 – 7.02 (m, 1H), 7.00 (dd, J = 9.3, 2.9 Hz,
1H), 6.95 (ddd, J = 8.1, 7.5, 2.9 Hz, 1H), 6.81 (dd, J = 8.5 Hz, 4JHꢀF = 4.9 Hz, 1H), 3.87 (bs,
2H); 13C NMR (151 MHz, CDCl3) δ 157.7 (d, 1JCꢀF = 238.6 Hz), 153.8, 137.5 (d, 4JCꢀF = 2.2
Hz), 131.2, 130.0, 129.0 (d, 3JCꢀF = 7.5 Hz), 125.8 (d, 4JCꢀF = 1.5 Hz), 121.4, 118.9 (d, 3JCꢀF
=
2
2
8.1 Hz), 118.8, 118.1 (d, JCꢀF = 22.7 Hz), 115.4 (d, JCꢀF = 22.5 Hz); HRMS m/z calc. for
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C12H10FNO [M+] 203.0746, found 203.0744; IR (neat) νmax = 3311, 1591, 1484, 1266, 1174,
903, 726 cmꢀ1; Rf 0.67 (hexane/EtOAc, 1/1)
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2'-amino-5'-chloro-[1,1'-biphenyl]-2-ol (1k): light brown solid (0.56 g, 51%); mp
102−103 °C; 1H NMR (600 MHz, CDCl3) δ 7.32 (ddd, J = 7.6, 7.5, 1.4 Hz 1H), 7.27 (dd, J
= 7.9, 1.4 Hz, 1H), 7.22 (d, J = 2.3 Hz, 1H), 7.18 (dd, J = 8.2, 2.3 Hz, 1H), 7.04 (d, J = 7.5
Hz, 1H), 7.03 (d, J = 8.2 Hz, 1H), 6.78 (dd, J = 7.9, 7.6 Hz, 1H), 4.68 (bs, 3H); 13C NMR
(151 MHz, CDCl3) δ 153.7, 140.8, 131.4, 131.2, 130.1, 128.9, 127.7, 125.6, 125.2, 121.5,
118.5, 118.4; HRMS m/z calc. for C12H10ClNO [M+] 219.0451, found 219.0453; IR (neat)
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ν
max = 3382, 3314, 3060, 1612, 1483, 754 cmꢀ1; Rf 0.69 (hexane/EtOAc, 1/1)
2'-amino-5'-(trifluoromethyl)-[1,1'-biphenyl]-2-ol (1l): yellow viscous oil (0.19 g, 15%);
1H NMR (600 MHz, CDCl3) δ 7.47 (dd, J = 8.0, 1.7 Hz, 1H), 7.46 (d, J = 1.6 Hz, 1H) 7.34
(ddd, J = 8.1, 7.1, 1.7 Hz, 1H), 7.26 (dd, J = 8.8, 1.6 Hz, 1H), 7.06 (ddd, J = 8.1, 8.0, 1.1,
Hz, 1H), 7.05 (dd, J = 7.1, 1.1 Hz, 1H), 6.89 (d, J = 8.8 Hz, 1H), 6.02 (bs, 1H), 4.03 (bs, 2H);
13C NMR (151 MHz, CDCl3) δ 153.6, 146.0, 131.3, 130.4, 129.1(q, 3JCꢀF = 3.0 Hz), 126.5 (q,
1
2
3JCꢀF = 3.0 Hz), 125.7 (q, JCꢀF = 271.8 Hz), 124.5, 124.2, 122.2 (q, JCꢀF = 33.2 Hz), 121.7,
117.8, 116.2; HRMS m/z calc. for C13H10F3NO [M+] 253.0714, found 253.0716; IR (neat)
νmax = 3386, 1625, 1488, 1335, 1111 cmꢀ1; Rf 0.41 (hexane/EtOAc, 2/1)
2'-amino-5'-(trifluoromethoxy)-[1,1'-biphenyl]-2-ol (1m): yellow viscous oil (1.08 g, 80%);
1H NMR (600 MHz, CDCl3) δ 7.34 (ddd, J = 7.8, 7.7, 1.3 Hz, 1H), 7.28 (dd, J = 7.8, 1.3 Hz,
1H), 7.14 (d, J = 1.9 Hz, 1H), 7.11 (d, J = 8.6 Hz, 1H), 7.06 – 7.04 (m, 2H), 6.85 (d, J = 8.6
3
Hz, 1H), 4.09 (bs, 3H); 13C NMR (151 MHz, CDCl3) δ 153.5, 142.8 (q, JCꢀF = 2.0 Hz),
1
140.6, 131.1, 130.1, 127.3, 124.9, 124.5, 121.8, 121.4, 120.6 (q, JCꢀF = 256.7 Hz), 118.3,
117.8; HRMS m/z calc. for C13H10F3NO2 [M+] 269.0664, found 269.0667; IR (neat) νmax
3327, 1622, 1485, 1251, 1214, 1164 cmꢀ1; Rf 0.41 (hexane/EtOAc, 2/1)
=
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6-amino-2'-hydroxy-[1,1'-biphenyl]-3-carbonitrile (1n): orange solid (0.81 g, 77%); mp
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7
1
128−129 °C; H NMR (600 MHz, CDCl3) δ 7.48 (dd, J = 8.3, 1.8 Hz, 1H), 7.46 (d, J = 1.8
8
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Hz, 1H), 7.34 (ddd, J = 8.1, 7.6, 1.4 Hz, 1H), 7.20 (dd, J = 7.5, 1.4 Hz, 1H), 7.04 (dd, J = 7.6,
7.5 Hz, 1H), 7.03 (d, J = 8.1 Hz, 1H), 6.83 (d, J = 8.3 Hz, 1H), 5.85 (bs, 1H), 4.24 (bs, 2H);
13C NMR (151 MHz, CDCl3) δ 153.3, 147.8, 135.9, 133.4, 131.2, 130.7, 123.8, 123.3, 121.8,
119.7, 117.4, 116.0, 102.0; HRMS m/z calc. for C13H10N2O [M+] 210.0793, found 210.0790;
IR (neat) νmax = 3373, 2219, 1620, 1497, 756 cmꢀ1; Rf 0.53 (hexane/EtOAc, 1/1)
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2'-amino-4'-nitro-[1,1'-biphenyl]-2-ol (1o): yellow solid (0.59 g, 51%); mp 147−149 °C; 1H
NMR (600 MHz, DMSO-d6) δ 9.74 (s, 1H), 7.61 (d, J = 1.2 Hz, 1H), 7.42 (dd, J = 8.2, 1.2
Hz, 1H), 7.24 (dd, J = 7.9, 7.4 Hz, 1H), 7.18 (d, J = 7.9 Hz, 1H), 7.12 (d, J = 7.4 Hz, 1H),
6.98 (d, J = 8.2 Hz, 1H), 6.90 (dd, J = 7.4, 7.4 Hz, 1H), 5.22 (bs, 2H); 13C NMR (151 MHz,
DMSO-d6) δ 154.3, 147.4, 147.1, 131.8, 130.8, 130.7, 129.4, 124.4, 119.5, 116.0, 110.4,
108.4; HRMS m/z calc. for C12H10N2O3 [M+] 230.0691, found 230.0693; IR (neat) νmax
3377, 3284, 2361, 1608, 1585, 1484, 1351 cmꢀ1; Rf 0.39 (hexane/EtOAc, 2/1)
=
2'-amino-3'-bromo-[1,1'-biphenyl]-2-ol (1p):23 light brown solid (0.26 g, 20%); mp
1
148−150 °C; H NMR (600 MHz, DMSO-d6) δ 9.66 (bs, 1H), 7.38 (dd, J = 7.8, 1.3 Hz,
1H), 7.22 (dd, J = 8.1, 7.3 Hz 1H), 7.08 (dd, J = 7.5, 1.3 Hz, 1H), 7.00 – 6.95 (m, 2H), 6.89
(dd, J = 7.3, 7.2 Hz, 1H), 6.60 (dd, J = 7.8, 7.5 Hz, 1H), 4.54 (bs, 2H); 13C NMR (151 MHz,
DMSO-d6) δ 154.3, 142.7, 131.3, 131.1, 130.3, 129.0, 126.2, 125.6, 119.5, 117.7, 115.8,
108.7; IR (neat) νmax = 3370, 3272, 1506, 1436, 1108, 1038, 637 cmꢀ1; Rf 0.48
(hexane/EtOAc, 4/1)
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2'-amino-5-fluoro-[1,1'-biphenyl]-2-ol (1q):24 brown viscous oil (0.38 g, 37%); H NMR
(600 MHz, CDCl3) δ 7.25 (dd, J = 7.8, 7.4 Hz, 1H), 7.23 (d, J = 7.6 Hz, 1H), 7.03 (dd, 3JHꢀ
4
= 9.1 Hz, J = 3.1 Hz, 1H), 7.01 – 6.98 (m, 2H), 6.96 (dd, J = 8.8 Hz, JHꢀF = 5.0 Hz, 1H),
F
6.85 (d, J = 7.8 Hz, 1H), 5.03 (bs, 3H); 13C NMR (151 MHz, CDCl3) 157.3 (d, 1JCꢀF = 238.6
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Hz), 149.8, 141.6, 131.7, 129.4, 127.6 (d, JCꢀF = 9.1 Hz), 125.9, 121.4, 119.4 (d, JCꢀF = 7.6
Hz), 117.8, 117.0 (d, 2JCꢀF = 22.7 Hz), 115.9 (d, 2JCꢀF = 22.7 Hz); IR (neat) νmax = 1482, 1261,
1175, 905, 722 cmꢀ1; Rf 0.43 (hexane/EtOAc, 2/1)
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Analytic Data for Dibenzofuran Products
dibenzo[b,d]furan (2a):8d white solid (0.5 mmol scale: 62 mg, 74%, 6 mmol scale: 0.77g,
76%); 1H NMR (600 MHz, CDCl3) δ 7.97 (d, J = 7.7 Hz, 2H), 7.59 (d, J = 8.2 Hz, 2H), 7.47
(dd, J = 8.2, 7.4 Hz, 2H), 7.36 (dd, J = 7.7, 7.4 Hz, 2H); 13C NMR (151 MHz, CDCl3) δ
156.4, 127.3, 124.4, 122.9, 120.7, 111.9; IR (neat) νmax = 3047, 1444, 1195, 723 cmꢀ1; Rf
0.57 (hexane)
2-methyldibenzo[b,d]furan (2b):9d, 8e white solid (59 mg, 65%); H NMR (600 MHz,
1
CDCl3) δ 7.95 (d, J = 7.7 Hz, 1H), 7.77 (s, 1H), 7.60 (d, J = 8.2 Hz, 1H), 7.50 (d, J = 8.2 Hz
1H), 7.48 (dd, J = 8.2, 7.6 Hz, 1H), 7.36 (dd, J = 7.7 ,7.6 Hz, 1H), 7.30 (d, J = 8.2 Hz, 1H),
2.55 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 156.7, 154.7, 132.3, 128.4, 127.1, 124.5, 124.4,
122.7, 120.8, 120.7, 111.8, 111.3, 21.5; IR (neat) νmax = 3044, 2921, 1481, 1447, 1192, 744
cmꢀ1; Rf 0.57 (hexane)
3-methoxydibenzo[b,d]furan (2d):9d, 9e white solid (84 mg, 85%); H NMR (600 MHz,
1
CDCl3) δ 7.87 (d, J = 7.7 Hz, 1H), 7.81 (d, J = 8.5 Hz, 1H), 7.54 (d, J = 7.8 Hz, 1H), 7.39 (dd,
J = 7.8, 7.6 Hz, 1H), 7.32 (dd, J = 7.7, 7.6 Hz, 1H), 7.11 (d, J = 2.0 Hz, 1H), 6.96 (dd, J = 8.5,
2.0 Hz, 1H), 3.91 (s, 3H); 13C NMR (151 MHz, CDCl3) 160.1, 157.7, 156.5, 125.9, 124.6,
122.9, 121.1, 112.0, 117.5, 111.5, 111.1, 96.7, 55.9; IR (neat) νmax = 2983, 1458, 1236, 1043,
750 cmꢀ1; Rf 0.60 (hexane/EtOAc, 8/1)
1-(dibenzo[b,d]furan-2-yl)ethan-1-one (2e):9e white solid (71 mg, 68%); H NMR (600
1
MHz, CDCl3) δ 8.56 (s, 1H), 8.08 (d, J = 8.4 Hz, 1H), 7.98 (d, J = 7.6 Hz, 1H), 7.58 (d, J =
8.0 Hz, 1H), 7.57 (d, J = 8.4 Hz, 1H), 7.49 (dd, J = 8.0, 7.4 Hz, 1H), 7.38 (dd, J = 7.6, 7.4 Hz,
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1H), 2.70 (s, 3H); C NMR (151 MHz, CDCl3) δ 197.5, 159.1, 157.1, 132.7, 128.2, 128.1,
124.8, 124.0, 123.6, 121.8, 121.2, 112.1, 111.8, 27.0; IR (neat) νmax = 3064, 2926, 1677,
1599, 1476 cmꢀ1; Rf 0.47 (hexane/EtOAc, 4/1)
methyl dibenzo[b,d]furan-2-carboxylate (2f):8d, 8g white solid (49 mg, 43%); 1H NMR (600
MHz, CDCl3) δ 8.67 (dd, J = 1.8, 0.5 Hz, 1H), 8.18 (dd, J = 8.6, 1.8 Hz, 1H), 7.99 (ddd, J =
7.7, 1.3, 0.6 Hz, 1H), 7.59 (ddd, J = 8.3, 0.9, 0.6 Hz, 1H), 7.58 (dd, J = 8.6, 0.5 Hz, 1H), 7.50
(ddd, J = 8.3, 7.4, 1.3 1H), 7.38 (ddd, J = 7.7, 7.4, 0.9 Hz, 1H), 3.98 (s, 3H); 13C NMR (151
MHz, CDCl3) δ 167.2, 159.1, 157.0, 129.1, 128.1, 125.2, 124.6, 123.9, 123.5, 123.1, 121.2,
112.1, 111.7, 52.4; IR (neat) νmax = 3066, 2951, 1718, 1603, 1435, 1249 cmꢀ1; Rf 0.58
(hexane/EtOAc, 6/1)
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2-fluoro-8-methyldibenzo[b,d]furan (2g): white solid (53 mg, 53%); mp 69−70 °C; H
NMR (600 MHz, CDCl3) δ 7.69 (s, 1H), 7.56 (dd, 3JHꢀF = 8.2 Hz, J = 2.6 Hz, 1H), 7.47 (dd,
J = 8.9 Hz, 4JHꢀF = 4.0 Hz, 1H), 7.44 (d, J = 8.3 Hz, 1H), 7.28 (d, J = 8.3 Hz, 1H), 7.15 (ddd,
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3JHꢀF = 9.0 Hz, J = 8.9, 2.6 Hz, 1H), 2.51 (s, 3H); C NMR (151 MHz, CDCl3) δ 159.1 (d,
3
1JCꢀF = 238.6 Hz), 155.8, 152.7, 132.5, 129.1, 125.3 (d, JCꢀF = 10.6 Hz), 124.2 (d, 4JCꢀF = 3.0
Hz), 121.0, 114.4 (d, 2JCꢀF = 25.7 Hz), 112.4 (d, 3JCꢀF = 10.6 Hz), 111.6, 106.7 (d, 2JCꢀF = 25.7
Hz), 21.5; HRMS m/z calc. for C13H9FO [M+] 200.0637, found 200.0635; IR (neat) νmax
2921, 1596, 1487, 1456, 1137, 810 cmꢀ1; Rf 0.40 (hexane)
=
2-fluoro-7-methoxydibenzo[b,d]furan (2h): light yellow solid (70 mg, 65%); mp 92−93 °C;
1H NMR (600 MHz, CDCl3) δ 7.75 (d, J = 8.5 Hz, 1H), 7.50 (dd, 3JH–F = 8.3 Hz, J = 2.6 Hz,
1H), 7.43 (dd, J = 8.9 Hz, 4JH–F = 4.1 Hz, 1H), 7.08 (d, J = 2.2 Hz, 1H), 7.07 (ddd, 3JH–F = 9.0
13
Hz, J = 8.9, 2.6 Hz, 1H), 6.94 (dd, J = 8.5, 2.2 Hz, 1H), 3.90 (s, 3H); C NMR (151 MHz,
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CDCl3) δ 160.2, 159.4 (d, JCꢀF = 239.1 Hz), 158.8, 152.5, 125.6 (d, JCꢀF = 10.3 Hz), 121.4,
117.3 (d, 4JCꢀF = 3.5 Hz), 113.0 (d, 2JCꢀF = 25.8 Hz), 112.1 (d, 3JCꢀF = 9.4 Hz), 111.5, 106.2 (d,
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2JCꢀF = 25.4 Hz), 96.7, 56.0; HRMS m/z calc. for C13H9FO2 [M+] 216.0587, found 216.0584;
IR (neat) νmax = 2965, 1637, 1501, 1275, 1147 cmꢀ1; Rf 0.60 (hexane/EtOAc, 6/1)
benzofuro[3,2-b]pyridine (2i): 25 yellow solid (51 mg, 60%); 1H NMR (600 MHz, CDCl3) δ
8.63 (d, J = 4.8 Hz, 1H), 8.24 (d, J = 7.6 Hz, 1H), 7.83 (d, J = 8.1 Hz, 1H), 7.60 (d, J = 8.3
Hz, 1H), 7.56 (dd, J = 8.1, 7.3 Hz, 1H), 7.44 (dd, J = 7.6, 7.3 Hz, 1H), 7.37 (dd, J = 8.3, 4.8
Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 157.6, 149.9, 145.4, 144.5, 129.4, 123.8, 123.5,
121.5, 121.4, 118.8, 112.3; IR (neat) νmax = 3061, 1631, 1593, 1449, 1401, 1189 cmꢀ1; Rf
0.45 (hexane/EtOAc, 2/1)
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2-fluorodibenzo[b,d]furan (2j):8e, 8g white solid (24 mg, 26%); H NMR (600 MHz, CDCl3)
δ 7.91 (d, J = 7.7 Hz, 1H), 7.61 (dd, 3JHꢀF = 8.6 Hz, J = 2.7 Hz, 1H), 7.57 (d, J = 8.7 Hz, 1H),
7.52 – 7.47 (m, 2H), 7.35 (dd, J = 7.7, 7.5 Hz, 1H), 7.17 (ddd, J = 8.7, 2.7 Hz, 3JHꢀF = 8.6 Hz,
1
1H); 13C NMR (151 MHz, CDCl3) δ 159.2 (d, JCꢀF = 238.6 Hz), 157.4, 152.4, 128.0, 125.3
(d, 3JCꢀF = 10.6 Hz), 124.2 (d, 4JCꢀF = 3.0 Hz), 123.0, 121.1, 114.6 (d, 2JCꢀF = 25.7 Hz), 112.5
(d, 3JCꢀF = 9.1 Hz), 112.1, 106.9 (d, 2JCꢀF = 25.7 Hz); IR (neat) νmax = 2926, 1599, 1478, 1447,
1162 cmꢀ1; Rf 0.57 (hexane)
1
2-chlorodibenzo[b,d]furan (2k):9d white solid (41 mg, 40%); H NMR (600 MHz, CDCl3)
δ 7.92 (d, J = 2.2 Hz, 1H), 7.91 (dd, J = 7.6, 1.1 Hz, 1H), 7.57 (dd, J = 8.3, 0.9 Hz, 1H), 7.50
(d, J = 8.7 Hz, 1H), 7.49 (ddd, J = 8.3, 7.3, 1.1 Hz, 1H) 7.41 (dd, J = 8.7, 2.2 Hz, 1H), 7.36
(ddd, J = 7.6, 7.3, 0.9 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 157.0, 154.7, 128.4, 128.1,
127.4, 125.9, 123.6, 123.2, 121.0, 120.7, 112.9, 112.1; IR (neat) νmax = 3063, 1624, 1440,
1199, 725 cmꢀ1; Rf 0.48 (hexane)
1
2-(trifluoromethyl)dibenzo[b,d]furan (2l):8g white solid (37 mg, 31%); H NMR (600
MHz, CDCl3) δ 8.23 (s, 1H), 7.98 (d, J = 7.7 Hz, 1H), 7.72 (d, J = 8.6 Hz, 1H), 7.64 (d, J =
8.6 Hz, 1H), 7.61 (d, J = 8.3 Hz, 1H), 7.53 (dd, J = 8.3, 7.2 Hz, 1H), 7.40 (dd, J = 7.7, 7.2 Hz,
2
1H); 13C NMR (151 MHz, CDCl3) δ 157.8, 157.1, 128.4, 125.6 (q, JCꢀF = 32.4 Hz), 124.8,
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124.8 (q, JCꢀF = 272.1 Hz), 124.4 (q, JCꢀF = 3.7 Hz), 123.6, 123.5, 121.2, 118.5 (q, JCꢀF
=
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4.0 Hz), 112.3 112.2; IR (neat) νmax = 2927, 1332, 1272, 1107, 731 cmꢀ1; Rf 0.50 (hexane)
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2-(trifluoromethoxy)dibenzo[b,d]furan (2m): white solid (55 mg, 44%); mp 59−60 °C; H
NMR (600 MHz, CDCl3) δ 7.94 (d, J = 7.7 Hz, 1H), 7.80 (s, 1H), 7.59 (d, J = 8.0 Hz, 1H),
7.56 (d, J = 8.7 Hz, 1H), 7.51 (dd, J = 8.0, 7.5 Hz, 1H), 7.38 (dd, J = 7.7, 7.5 Hz, 1H), 7.32 (d,
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J = 8.7 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 157.4, 154.4, 145.0 (q, JCꢀF = 1.8 Hz),
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128.3, 125.4, 123.9, 123.3, 121.1, 120.9 (q, JCꢀF = 256.8 Hz), 120.7, 113.8, 112.6, 112.2;
HRMS m/z calc. for C13H7F3O2 [M+] 252.0398, found 252.0399; IR (neat) νmax = 1590,
1477, 1447, 1258, 1160, 747 cmꢀ1; Rf 0.58 (hexane)
dibenzo[b,d]furan-2-carbonitrile (2n):9e offꢀwhite solid (25 mg, 26%); 1H NMR (600 MHz,
CDCl3) δ 8.28 (d, J = 1.7 Hz, 1H), 7.98 (d, J = 7.7 Hz, 1H), 7.75 (dd, J = 8.5, 1.7 Hz, 1H),
7.65 (d, J = 8.5 Hz, 1H), 7.63 (d, J = 8.3 Hz, 1H), 7.56 (dd, J = 8.3, 7.3 Hz, 1H), 7.43 (dd, J =
7.7, 7.3 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 158.2, 157.0, 131.1, 129.0, 125.6, 125.5,
124.0, 122.8, 121.3, 119.4, 113.1, 112.3, 106.8; IR (neat) νmax = 2225, 2699, 1474, 1448,
1247, 752 cmꢀ1; Rf 0.52 (hexane/EtOAc, 6/1)
1
3-nitrodibenzo[b,d]furan (2o): white solid (32 mg, 30%); mp 175−177 °C; H NMR (600
MHz, CDCl3) δ 8.44 (d, J = 1.9 Hz, 1H), 8.28 (dd, J = 8.5, 1.9 Hz, 1H), 8.05 (d, J = 7.8 Hz,
1H), 8.03 (d, J = 8.5 Hz, 1H), 7.65 (d, J = 8.3 Hz, 1H), 7.60 (dd, J = 8.3, 7.2 Hz, 1H), 7.44
(dd, J = 7.8, 7.2 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 158.5, 155.3, 147.0, 130.4, 124.0,
122.7, 122.0, 120.8, 112.5, 108.2; HRMS m/z calc. for C12H7NO3 [M+] 213.0426, found
213.0428; IR (neat) νmax = 2851, 1628, 1523, 1457, 1343 cmꢀ1; Rf 0.45 (hexane/EtOAc, 5/1)
4-bromodibenzo[b,d]furan (2p): 26 yellow solid (28 mg, 23%); 1H NMR (600 MHz, CDCl3)
δ 7.94 (d, J = 7.7 Hz, 1H), 7.89 (d, J = 7.6 Hz, 1H), 7.66 (d, J = 8.0 Hz, 1H), 7.62 (d, J = 7.9
Hz, 1H), 7.50 (dd, J = 8.0, 7.5 Hz, 1H), 7.38 (dd, J = 7.6, 7.5 Hz, 1H), 7.23 (dd, J = 7.9, 7.7
Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 156.3, 153.5, 130.3, 128.1, 125.9, 124.4, 124.2,
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123.5, 121.3, 119.9, 112.3, 104.7, 77.4; IR (neat) νmax = 1576, 1447, 1417, 1195, 650 cmꢀ1;
Rf 0.55 (hexane/EtOAc, 20/1)
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website.
1
13
NMR spectra for H NMR and C NMR spectra of 2'ꢀamino[1,1'ꢀbiphenyl]ꢀ2ꢀol derivatives
and dibenzofuran derivatives (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: ejcho@cau.ac.kr.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
This research was supported by the ChungꢀAng University Graduate Research Scholarship in
2017 for J. Y. Cho. We gratefully acknowledge the National Research Foundation of Korea
[NRFꢀ2012M3A7B4049657, NRFꢀ2014ꢀ011165, NRFꢀ2016K1A3A1A19945930, and NRFꢀ
2017R1A2B2004082].
REFERENCES
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(1) Kokubun, T.; Harborne, J. B.; Eagles, J.; Waterman, P. G., Phytochemistry 1995,
39, 1039.
7
8
9
(2) Collin, G.; Höke, H., Benzofurans. In Ullmann's Encyclopedia of Industrial
Chemistry, WileyꢀVCH Verlag GmbH & Co. KGaA2000; Vol. 5, pp 325.
(3) Chizzali, C.; Beerhues, L., Beilstein J. Org. Chem. 2012, 8, 613.
(4) Martel, R. R.; Rochefort, J. G.; Klicius, J.; Dobson, T. A., Can. J. Physiol. Pharmacol.
1974, 52, 669.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(5) Petrassi, H. M.; Johnson, S. M.; Purkey, H. E.; Chiang, K. P.; Walkup, T.; Jiang, X.;
Powers, E. T.; Kelly, J. W., J. Am. Chem. Soc. 2005, 127, 6662.
(6) Lin, R.ꢀD.; Chen, M.ꢀC.; Liu, Y.ꢀL.; Lin, Y.ꢀT.; Lu, M.ꢀK.; Hsu, F.ꢀL.; Lee, M.ꢀH., Int.
J. Mol. Sci. 2015, 16, 28598.
(7) Zhang, L.; Zhang, Y.ꢀX.; Hu, Y.; Shi, X.ꢀB.; Jiang, Z.ꢀQ.; Wang, Z.ꢀK.; Liao, L.ꢀS., ACS
Appl. Mater. Interfaces 2016, 8, 16186.
(8) (a) Henderson Jr, W. A.; Zweig, A., Tetrahedron Lett. 1969, 10, 625. (b) Ejlx, J.;
Murphy, D.; Sargent, M., Synth. Commun. 1972, 2, 427. (c) Wang, J.ꢀQ.; Harvey, R. G.,
Tetrahedron 2002, 58, 5927. (d) Liu, Z.; Larock, R. C., Org. Lett. 2004, 6, 3739. (e)
Wang, C.; Piel, I.; Glorius, F., J. Am. Chem. Soc. 2009, 131, 4194. (f) Du, Z.; Zhou, J.;
Si, C.; Ma, W., Synlett 2011, 2011, 3023. (g) Lockner, J. W.; Dixon, D. D.; Risgaard, R.;
Baran, P. S., Org. Lett. 2011, 13, 5628.
(9) (a) Maevskii, Y. V.; Migachev, G., Chem. Heterocycl. Compd. 1986, 22, 676. (b)
Yamato, T.; Hideshima, C.; Prakash, G. K. S.; Olah, G. A., J. Org. Chem. 1991, 56,
3192. (c) Liu, J.; Fitzgerald, A. E.; Mani, N. S., J. Org. Chem. 2008, 73, 2951. (d) Wei,
Y.; Yoshikai, N., Org. Lett. 2011, 13, 5504. (e) Xiao, B.; Gong, T.ꢀJ.; Liu, Z.ꢀJ.; Liu, J.ꢀ
H.; Luo, D.ꢀF.; Xu, J.; Liu, L., J. Am. Chem. Soc. 2011, 133, 9250. (f) Yang, W.; Zhou,
J.; Wang, B.; Ren, H., Chem. Eur. J. 2011, 17, 13665.
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6
(10) (a) Roglans, A.; PlaꢀQuintana, A.; MorenoꢀManas, M., Chem. Rev. 2006, 106, 4622. (b)
Hari, D. P.; König, B., Angew. Chem. Int. Ed. 2013, 52, 4734.
7
8
9
(11) (a) Chatterjee, T.; Choi, M. G.; Kim, J.; Chang, S. K.; Cho, E. J., Chem. Commun. 2016,
52, 4203. (b) Choi, Y.; Chatterjee, T.; Kim, J.; Kim, J. S.; Cho, E. J., Org. Biomol.
Chem. 2016, 14, 6804. (c) Chatterjee, T.; Lee, D. S.; Cho, E. J., J. Org. Chem. 2017, 82,
4369. (d) Chatterjee, T.; Roh, G. B.; Shoaib, M. A.; Suhl, C. H.; Kim, J. S.; Cho, C. G.;
Cho, E. J., Org. Lett. 2017, 19, 1906.
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(12) Some recent reviews on visible light photocatalysis, see: (a) Narayanam, J. M. R.;
Stephenson, C. R. J., Chem. Soc. Rev. 2011, 40, 102. (b) Prier, C. K.; Rankic, D. A.;
MacMillan, D. W. C., Chem. Rev. 2013, 113, 5322. (c) Schultz, D. M.; Yoon, T. P.,
Science 2014, 343, 1239176. (d) Cambié, D.; Bottecchia, C.; Straathof, N. J. W.; Hessel,
V.; Noël, T., Chem. Rev. 2016, 116, 10276. (e) Romero, N. A.; Nicewicz, D. A., Chem.
Rev. 2016, 116, 10075.
(13) Sun, C.ꢀL.; Shi, Z.ꢀJ., Chem. Rev. 2014, 114, 9219.
(14) Martiny, M.; Steckhan, E.; Esch, T., Chem. Ber. 1993, 126, 1671.
(15) The e ciency of reactions can depend on the substitution pattern of the biaryls, see:
Cho, S. H.; Yoon, J.; Chang, S., J. Am. Chem. Soc. 2011, 133, 5996.
(16) The diazonium salt intermediates remained after reaction.
(17) Ramanathan, M.; Liu, S.ꢀT., J. Org. Chem. 2015, 80, 5329.
(18) Li, C.; Hoffman, M. Z., J. Phys. Chem. B, 1999, 103, 6653.
(19) Ortgies, S.; Depken, C.; Breder, A., Org. Lett. 2016, 18, 2856.
(20) Lee, E.; Hooker, J. M.; Ritter, T., J. Am. Chem. Soc. 2012, 134, 17456.
(21) Kumar, A.; Sattar, M.; Verma, A.; Dara, A.; Kumar, S., RSC Adv. 2015, 5, 44728.
(22) Chauhan, J.; Wang, H.; Yap, J. L.; Sabato, P. E.; Hu, A.; Prochownik, E. V.;
Fletcher, S., ChemMedChem 2014, 9, 2274.
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(23) Gao, H.; Ess, D. H.; Yousufuddin, M.; Kürti, L., J. Am. Chem. Soc. 2013, 135,
7086.
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8
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(24) Liu, B.; Yin, M.; Gao, H.; Wu, W.; Jiang, H., J. Org. Chem. 2013, 78, 3009.
(25) Abramovitch, R. A.; Inbasekaran, M. N.; Kato, S.; Radzikowska, T. A.; Tomasik,
P., J. Org. Chem. 1983, 48, 690.
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(26) Unger, Y.; Meyer, D.; Molt, O.; Schildknecht, C.; Münster, I.; Wagenblast, G.;
Strassner, T., Angew. Chem. Int. Ed. 2010, 49, 10214.
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