Extended Study of Visible-Light-Induced Photocatalytic [4 + 2] Benzannulation: Synthesis of Polycyclic (Hetero)Aromatics

Article abstract of DOI:10.1021/acs.joc.7b00413

Herein we report an extended study of [4 + 2] benzannulation reactions of 2-(hetero)aryl-substituted anilines with alkynes by visible light photocatalysis. The method requires the use of ^tBuONO as a diazotizing agent and 0.3 mol % of fac-Ir(ppy)₃ as a photocatalyst at room temperature. The reaction proceeded in a chemo- and regioselective manner with high functional group tolerance under mild conditions allowing the preparation of a wide variety of polycyclic (hetero)aromatic compounds, including phenanthrenes, in moderate to high yields. This procedure is amenable to gram-scale synthesis of 9-phenylphenanthrene.

Full text of DOI:10.1021/acs.joc.7b00413

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Article
Extended Study of Visible Light-Induced Photocatalytic [4 +
2] Benzannulation: Synthesis of Polycyclic (Hetero)Aromatics
Tanmay Chatterjee, Da Seul Lee, and Eun Jin Cho
J. Org. Chem., Just Accepted Manuscript • Publication Date (Web): 23 Mar 2017
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Extended Study of Visible LightꢀInduced Photocatalytic
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[4 + 2] Benzannulation: Synthesis of Polycyclic (Hetero)Aromatics
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Tanmay Chatterjee, Da Seul Lee, and Eun Jin Cho*
Department of Chemistry, ChungꢀAng University
84 Heukseokꢀro, Dongjakꢀgu, Seoul 06974, Republic of Korea.
*Eꢀmail: ejcho@cau.ac.kr
Abstract: Herein we report an extended study of [4 + 2] benzannulation reactions of 2ꢀ
(hetero)arylꢀsubstituted anilines with alkynes by visible light photocatalysis. The method
t
requires the use of BuONO as a diazotizing agent and 0.3 mol% of facꢀIr(ppy)3 as a
photocatalyst at room temperature. The reaction proceeded in a chemoꢀ and regioselective
manner with high functional group tolerance under mild conditions allowing the preparation of a
wide variety of polycyclic (hetero)aromatic compounds, including phenanthrenes, in moderate to
high yields. This procedure is amenable to gramꢀscale synthesis of 9ꢀphenylphenanthrene.
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INTRODUCTION
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Polycyclic aromatic and heteroaromatic compounds have received considerable attention
because of their various biological and electronic properties and have been used as important
structural motifs in many applications.1 In particular, they have been applied to various
electronic devices such as organic lightꢀemitting diodes (OLEDs) and organic fieldꢀeffect
transistors (OFETs).2 In addition, polycyclic (hetero)aromatic systems constitute the core
structures of many biologically active natural products, pharmaceuticals, and agrochemicals
(Figure 1).1a,3
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Figure 1. Examples of polycyclic (hetero)aromatic compounds and their applications.
Owing to their significant importance, numerous synthetic approaches to polycyclic
(hetero)aromatics were reported so far.4 Among them, the intermolecular [4 + 2] benzannulation
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between a functionalized biaryl derivative and an alkyne has received much attention as a simple
and straightforward method for the construction of polycyclic aromatic units such as
phenanthrene units. In particular, the [4 + 2] benzannulation reaction of 2ꢀfunctionalized 1,1′ꢀ
biaryls with alkynes through the activation of the C2′ꢀH bond is perhaps one of the most atomꢀ
economical routes to phenanthrene derivatives requiring only one preꢀfunctionalization of
substrates (Scheme 1). In 1987, the Heck group first disclosed the Pdꢀcatalyzed [4 + 2]
benzannulation reaction of 2ꢀiodobiphenyl with diphenylacetylene for the synthesis of 9,10ꢀ
diphenylphenanthrene by using Pd(OAc)2, PPh3, and Et3N at 100 °C.5 In 1997, Larock et al.
showed that the reaction could be further improved in terms of both yield and substrate scope by
using NaOAc as base.6 In 2010, the Glorius group developed a Pdꢀcatalyzed decarboxylative
reaction between 2ꢀarylbenzoic acids and alkynes to afford phenanthrenes in the presence of a
base and Ag2CO3 as an oxidant at 140 °C.7 An ironꢀcatalyzed reaction between 2ꢀbiaryl
magnesium bromides and alkynes in the presence of 4,4′ꢀdiꢀtertꢀbutylꢀ2,2′ꢀbipyridyl as a ligand
and 1,2ꢀdichloroisobutane as an oxidant at room temperature was reported by Nakamura et al.8
The Miura group developed an iridiumꢀcatalyzed coupling of 2ꢀarylbenzoyl chlorides with
alkynes in the presence of P(tꢀBu)3 as a ligand at 160 °C to afford phenanthrenes.9 Recently, the
same group reported rhodiumꢀcatalyzed oxidative benzannulation of (2ꢀarylphenyl)boronic acids
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with alkynes for the synthesis of phenanthrenes by using [Cp*RhCl2]2 and Cu(OAc)2 at 100 C
under aerobic atmosphere.10 In addition, Studer et al. reported the construction of the
phenanthrene ring via baseꢀpromoted homolytic aromatic substitution of 2ꢀaminobiaryls with
alkynes in the presence of isoamyl nitrite as a diazotizing agent and substoichiometric amounts
of tetrabutylammonium iodide (Bu4NI) as a radical initiator at 70 °C.11 Recently, the Cai group
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developed a similar method using BuONO as a nitrite source and substoichiometric amounts of
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ascorbic acid as the radical initiator at room temperature.12 Despite these significant advances,
these methods often suffer from harsh reaction conditions such as the use of strong bases,
substoichiometric amounts of reagents, and high temperatures.
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Scheme 1. Previous Work on Phenanthrene Synthesis by [4 + 2] Benzannulation of 2ꢀ
Functionalized 1,1′ꢀBiaryls with Alkynes
In another arena, visible light photocatalysis has recently attracted the renewed interest of
synthetic chemists, owing to its environmental benignity and mechanistic versatility in a large
number of synthetically important reactions.13 In 2012, the Zhou group nicely developed a
visible lightꢀinduced reaction of biaryldiazonium salts with alkynes using eosin Y as a
photosensitizer [Scheme 2(a)].14 However, the reaction suffered from a limited substrate scope
due to the difficulties in preparing the starting biaryldiazonium tetrafluoroborate salts containing
functional groups such as Nꢀheterocycles.15 Moreover, the process involved the portion wise
addition of the diazonium salt (in six batches; 0.05 mmol per hour). Recently, we have overcome
the limitation by utilizing oneꢀpot amine diazotization protocol16 and reported a visible lightꢀ
induced [4 + 2] benzannulation between 2ꢀheteroarylꢀsubstituted anilines and heteroarylalkynes
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in the presence of BuONO as diazotizing agent and a cyclometalated Ir(III) complex, facꢀ
Ir(ppy)3 as the photocatalyst to synthesize a new class of heteroarylꢀsubstituted tricyclic
heteroaromatic compounds, which are potential materials for many applications [Scheme 2(b)].17
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Notably, the in situ generation of diazonium salt intermediates16 from easily available amino
substrates followed by radical cycloaddition with alkynes could be considered as an efficient and
practical strategy for the synthesis of polycyclic heteroaromatic compounds. Herein, we present a
detailed and extended study of the chemoꢀ and regioselective [4 + 2] benzannulation reaction of
2ꢀ(hetero)arylꢀsubstituted anilines with alkynes by visible light photocatalysis for the preparation
of a variety of substituted triꢀ and tetracyclic (hetero)aromatic compounds [Scheme 2(c)].
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Scheme 2. Visible Lightꢀinduced [4 + 2] Benzannulation for the Synthesis of Polycyclic
(Hetero)Aromatics Including Phenanthrenes
In particular, we focused our attention on the synthesis of phenanthrene derivatives
because, although their synthetic methods have been widely investigated, more efficient and
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practical alternatives are highly desirable. On the other hand, our strategy using in situ generated
diazonium intermediates in the presence of the cyclometalated Ir(III) complex facꢀIr(ppy)3 as the
photocatalyst has a wide substrate scope with a simple and practical protocol.
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RESULTS AND DISCUSSIONS
In order to optimize the reaction conditions, we started our investigation using 2ꢀaminobiphenyl
(1a) and phenylacetylene (2a) as model substrates for the synthesis of representative 9ꢀphenyl
phenanthrene (3aa) (Table 1). The reaction in the presence of 2.0 equiv of tBuONO and 1 mol%
of facꢀIr(ppy)3 in MeCN (1.0 M) under blue LEDs (7 W) at room temperature produced the
desired phenanthrene 3aa in 78% yield along with deaminated compound 4a as a side product
(Table 1, entry 1). Control experiments confirmed that the reaction requires visible light
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irradiation, a photocatalyst, and BuONO (Table 1, entries 2ꢀ4). Next, several Ruꢀ and Irꢀbased
complexes were screened as photocatalysts, but no improvement was observed (entries 5ꢀ8).
Eosin Y, used in the work by Zhou,14 was also found to be less efficient than facꢀIr(ppy)3 in this
transformation (entry 9). Studies of the reagent stoichiometry revealed that the amount of
tBuONO and the catalyst loading could be decreased to 1.5 equiv (entries 1, 10, and 11) and 0.3
mol% (entries 1, 12, and 13), respectively, without any loss in yield. Changing the nitrite source
to isoamyl nitrite did not improve the yield of the reaction (entry 14). Notably, the choice of
solvent was critical for success: among the examined solvents, including DCM, THF, DMF, and
DMSO, only MeCN gave good results (entries 12 and 15ꢀ18). Moreover, base additives had a
negative effect on the reaction; in particular, tertiary amine DBU completely inhibited the
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reaction probably by quenching of BuONO (entries 19ꢀ21). Finally, the use of 1.5 equiv of
alkyne at 1.0 M reaction concentration was found to be optimal (entries 12 and 22ꢀ26).
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Table 1. Optimization of Reaction Conditions for Phenanthrene Synthesisa
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nitrite source
photocatalyst
NH2
+
+
solvent
blue LEDs (7 W)
rt,10 h
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1a
2a
3aa
4a
Yield (%)b
photocatalyst
(mol%)
nitrite source
(equiv)
solvent
entry
variations
(concentration)
3aa
4a
--
tBuONO (2)
tBuONO (2)
tBuONO (2)
1
2
fac-Ir(ppy)3 (1.0)
fac-Ir(ppy)3 (1.0)
--
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
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20
17
--
10
6
no light
--
3
5
--
--
4
fac-Ir(ppy)3 (1.0)
Ru(bpy)3Cl2 (1.0)
Ru(phen)3Cl2 (1.0)
--
--
--
--
--
--
--
tBuONO (2)
tBuONO (2)
tBuONO (2)
tBuONO (2)
tBuONO (2)
tBuONO (3.0)
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[Ir(dtb-bpy)(ppy)2]PF6 (1.0)
fac-Ir(dFppy)3 (1.0)
eosin Y (1.0)
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10
fac-Ir(ppy)3 (1.0)
--
--
--
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
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12
13
14
15
fac-Ir(ppy)3 (1.0)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.1)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
DCM (1.0 M)
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78
68
65
26
10
10
14
15
61
--
--
--
isoamyl nitrite (1.5)
tBuONO (1.5)
tBuONO (1.5)
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20
21
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24
25
26
THF (1.0 M)
DMF (1.0 M)
DMSO (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
16
trace
trace
48
74
53
--
--
--
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
tBuONO (1.5)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
fac-Ir(ppy)3 (0.3)
K2CO3 (2 equiv)
K3PO4 (2 equiv)
15
7
20
DBU (2 equiv)
trace
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8
--
20
28
11
20
10
MeCN (0.5 M)
MeCN (0.25 M)
--
--
57
MeCN (2.0 M)
MeCN (1.0 M)
MeCN (1.0 M)
72
1.2 equiv 2a
3.0 equiv 2a
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78
aReaction conditions: 1a (0.1 mmol) and 2a (0.15 mmol) were used unless otherwise stated;
bYields were determined by gas chromatography using dodecane as an internal standard.
With the optimized conditions in hand, the substrate scope of the [4 + 2] benzannulation
reaction for the synthesis of phenanthrene derivatives was examined (Table 2). First, the reaction
of 1a with various terminal and internal alkynes was investigated (entries 1ꢀ10).
Phenylacetylenes substituted with electronꢀdonating (Me and OMe) or ꢀwithdrawing (F and CF3)
groups reacted smoothly to afford the corresponding 9ꢀaryl phenanthrene derivatives (3abꢀ3ae)
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in moderate to high yields (entries 2ꢀ5). Notably, the reactivity of unsubstituted and electronꢀrich
phenylacetylenes (2aꢀ2c) was higher in this system than in the system using eosin Y as the
photocatalyst reported by Zhou et al.14 The reactions with esterꢀsubstituted alkynes, namely
methyl propiolate (2f) and diethyl butꢀ2ꢀynedioate (2g), also proceeded to give methyl
phenanthreneꢀ9ꢀcarboxylate (3af) and diethyl phenanthreneꢀ9,10ꢀdicarboxylate (3ag),
respectively (entries 6 and 7). Another internal alkyne, namely ethyl 3ꢀphenylpropiolate (2h),
was also applicable to this reaction to generate the desired 9,10ꢀdisubstituted phenantherene 3ah,
albeit in relatively low yield (entry 8). Heteroaryl alkynes 3ꢀethynylthiophene (2i) and 2ꢀ
ethynylpyridine (2j) reacted smoothly with 1a to form the corresponding 9ꢀheteroarylꢀsubstituted
phenantherenes (3ai and 3aj) in moderate yields (entries 9 and 10). Unfortunately,
diphenylacetylene and aliphatic alkyne 1ꢀhexyne did not successfully undergo the [4 + 2]
benzannulation with 1a under the optimized conditions, probably because of the relative
instability of the corresponding vinyl radical formed after the addition of 2ꢀbiphenyl radical to
the corresponding alkyne.
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Next, the scope of the reaction with respect to the 2ꢀaminobiaryl substrates was examined
using phenylacetylene (2a) as a coupling partner (Table 2, entries 11ꢀ17). The electronic nature
and position of substituents did not significantly affect the efficiency of the transformation, and
2ꢀaminobiaryls bearing electronꢀdonating or ꢀwithdrawing substituents smoothly underwent
benzannulation (entries 11 and 12). Moreover, the reaction of 3'ꢀchloroꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine
(1d) produced a mixture of regioisomers 3da and 3da′ in 55% overall yield, with 3da as the
major isomer (3da:3da′ = 61:39) (entry 13). Diversely substituted biarylamines were also
subjected to the reaction with 2a under the optimized conditions, providing the corresponding
phenanthrene derivatives (3eaꢀ3ha) in 51ꢀ70% yield (entries 14ꢀ17). In general, the
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corresponding deaminated products 4 were also obtained as the side products, and the numbers in
parentheses indicate the yield of 4 in Table 2.
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Table 2. Substrate Scope of 2ꢀBiarylamines and Alkynesa
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aReaction conditions: amine 1 (0.5 mmol), alkyne 2 (0.75 mmol), BuONO (0.75 mmol), facꢀ
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Ir(ppy)3 (0.015 mmol) and MeCN (0.5 mL); byield of isolated phenanthrenes 3 is shown with the
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yield of corresponding deaminated side products 4 in parenthesis; ratio of regioisomers
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(3da:3da′ = 61:39) was determined by 1H NMR analysis of the crude reaction mixture.
Interestingly, the reactions using diynes as alkyne coupling partners proceeded with high
chemoselectivity under the optimized conditions (Scheme 3). The reaction of 1a with 1,4ꢀ
diphenylbutaꢀ1,3ꢀdiyne (5) provided the monobenzannulated product, 9ꢀphenylꢀ10ꢀ
(phenylethynyl)phenanthrene (6). In the reaction of 1a with 1,4ꢀdiethynylbenzene (7), only one
alkyne moiety participated in the reaction to give selectively 8 in 70% yield along with biphenyl
4a as the side product. Notably, only monoannulated products 6 and 8 were obtained even when
excess amount of 1a (1.5 equiv) was used.
Scheme 3. Chemoselective [4 + 2] Benzannulation with Diynesa,b
aReaction conditions: 1a (0.5 mmol), diyne (0.75 mmol), tBuONO (0.75 mmol), facꢀIr(ppy)3
(0.015 mmol) and MeCN (0.5 mL); byield of isolated products are shown.
Under the standard conditions, 2ꢀpolyarylꢀsubstituted anilines showed different
reactivities with 2a depending on the electron density of the polyaromatic moiety. Whereas 2ꢀ
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naphthylꢀsubstituted aniline 9 produced [4 + 2] benzannulated product 10, albeit in low yield,
phenanthreneꢀ and pyreneꢀsubstituted anilines (13 and 16) produced only cyclopentaꢀfused
polycyclic aromatic hydrocarbons (14 and 17) by intramolecular aromatic substitution along with
the formation of small amount of corresponding deaminated side products (Scheme 4).18
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Scheme 4. Different Reactivity of 2ꢀPolyarylꢀsubstituted Anilinesa,b
aReaction conditions: 2ꢀbiarylamine (0.1 mmol), 2a (0.15 mmol), tBuONO (0.15 mmol), facꢀ
b
Ir(ppy)3 (0.003 mmol) and MeCN (0.1 mL); yields were determined by gas chromatography
using dodecane as an internal standard.
To test the practicality of the method, we performed a gramꢀscale (10 mmol scale)
reaction between 1a and 2a under the standard conditions (Scheme 5). In the event, 3aa was
produced in a yield similar to that reported for the 0.5 mmol scale reaction (Table 2, entry 1),
demonstrating the feasibility of scaling up the process.
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Scheme 5. Scaleꢀup Experimenta,b
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aReaction conditions: 1a (10 mmol), 2a (15 mmol), tBuONO (15 mmol), facꢀIr(ppy) (0.3 mmol)
and MeCN (10 mL); bisolated yield of 3aa is shown.
As discussed in the introduction, this oneꢀpot protocol based on the in situ generation of
diazonium salts would allow for an expanded substrate scope. Generally, the isolation of
diazonium salts from amines containing Nꢀheterocycles under aqueous acidic conditions is a
challenging task because of the formation of Nꢀhydrochloride salts.15 By this oneꢀpot
t
diazotizationꢀ[4 + 2] benzannulation protocol using BuONO, 2ꢀheteroarylꢀsubstituted anilines
19 were successfully reacted with arylꢀsubstituted alkynes 2 (Table 3). In these reactions, 2ꢀ30%
of corresponding deaminated products 21 were obtained as the side products. 2ꢀ(Pyridinꢀ3ꢀ
yl)aniline (19a) reacted smoothly with phenylacetylene 2a affording a mixture of two
regioisomers (20aa:20aa′ = 72:28) in 77% overall yield (Table 3, entry 1). Phenylacetylenes
bearing electronꢀdonating or ꢀwithdrawing groups (2c and 2d) also participated in the [4 + 2]
benzannulation reaction with 19a to give the corresponding products in high yields (Table 3,
entries 2 and 3). In all cases, the regioisomers could be easily separated by silica gel column
chromatography. Notably, the reactions of 2ꢀ(furanꢀ3ꢀyl)aniline (19b) with phenylacetylenes 2a,
2c, and 2d were highly regioselective producing only 20ba, 20bc, and 20bd, respectively, in 54ꢀ
71% yield (Table 3, entries 4ꢀ6). This high regioselectivity could be explained by the higher
stability of the heterocyclic radical (S4) formed upon radical cyclization at the 2ꢀposition of the
furan moiety as compared to that of the species (S5) arising from the radical cyclization at the 4ꢀ
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position (see Scheme S1 in the SI). 2ꢀ(Benzo[b]thiophenꢀ2ꢀyl)aniline (19c) also participated in
the [4 + 2] benzannulation reaction with 2a producing the tetracyclic heteroaromatic compound
20ca (Table 3, entry 7), which is the core structure of an organic dye for solar cells (Figure 1).2a
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Table 3. Substrate Scope of 2ꢀHeteroarylꢀsubstituted Anilines and Alkynesa
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aReaction scale: amine 19 (0.5 mmol), alkyne 2 (0.75 mmol), tBuONO (0.75 mmol), facꢀIr(ppy)3
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b
(0.015 mmol) and MeCN (0.5 mL); yield of isolated polycyclic heteroaromatics 20 is shown
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c
with the yield of corresponding deaminated side products 21 in parenthesis; ratio of
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regioisomers was determined by 1H NMR analysis of the crude mixture.
A plausible reaction mechanism for the [4 + 2] benzannulation is shown in Scheme 6
t
with 1a and 2a as the model substrates. In situ diazotization of 1a by BuONO produces the
corresponding diazonium salt 22, which is reduced to biphenyl radical 23 by singleꢀelectron
transfer from the excited species, [IrIV(ppy)2(ppy)•−]*, formed from facꢀIr(ppy)3 under visible
light irradiation, with subsequent release of [IrIV(ppy)3]+. Addition of 23 to 2a generates the
corresponding vinyl radical 24, which undergoes intramolecular cyclization to form 25.
Photocatalytic oxidation of 25 by [IrIV(ppy)3]+ followed by deprotonation gives the final product
3aa along with the regeneration of the photocatalyst. The biphenyl side product probably results
from Hꢀatom abstraction by 23 from one of the many hydrogen donors present in the medium.
Scheme 6. Proposed Reaction Mechanism
NH2
4a
1a
tBuONO
(b)
H2O
2a
N2
N2OtBu
(a)
22
23
24
[IrIV(ppy)2(ppy)]*
[IrIV(ppy)3]+
hv
IrIII(ppy)3
25
+
OtBu
tBuOH
3aa
26
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In conclusion, we have expanded the scope of the [4 + 2] benzannulation of biarylamines
with alkynes under mild visible light photocatalytic conditions. The process requires only
tBuONO as the diazotization reagent and 0.3 mol% of facꢀIr(ppy)3 as the photocatalyst. This
oneꢀpot diazotization protocol overcomes the problems of synthesizing Nꢀcontaining polycyclic
heteroaromatic compounds. The reaction was found to be highly chemoꢀ and regioselective, and
could be applied to the synthesis of a variety of polycyclic (hetero)aromatic compounds,
obtained in moderate to high yields. Moreover, the reaction is amenable to gramꢀscale
operations.
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EXPERIMENTAL SECTION
General information. Acetonitrile was purchased from SigmaꢀAldrich chemical company in
SureꢀSeal bottles and degassed by repeated sonication under light vacuum and replenishing the
atmosphere with argon. facꢀIr(ppy)3 was purchased from SigmaꢀAldrich company. All other
reagents required for the synthesis of the amino starting substrates and polycyclic
(hetero)aromatic compounds were purchased from SigmaꢀAldrich, Alfa Aesar, Acros Organics,
or CombiꢀBlocks companies. Flash column chromatography was performed using Merck silica
gel 60 (70ꢀ230 mesh).
General analytical information. The synthesized amino substrates and polycyclic
1
(hetero)aromatic compounds were characterized by H, 13C NMR, and FTꢀIR spectroscopy.
1
NMR spectra were recorded on a Bruker 600 MHz instrument (600 MHz for H NMR and 151
1
MHz for 13C NMR). Copies of H and 13C NMR spectra can be found at the end of the
Supporting Information. 1H NMR experiments are reported in units, parts per million (ppm), and
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were measured relative to residual chloroform (7.26 ppm) in the deuterated solvent. C NMR
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spectra are reported in ppm relative to deuterochloroform (77.23 ppm), and all were obtained
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with H decoupling. Coupling constants were reported in Hz. FTꢀIR spectra were recorded on a
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Nicolet iS 10 ThermoFisher FTꢀIR spectrometer. Reactions were monitored by GCꢀMS using the
Agilent GC 7890B/5977A inert MSD with TripleꢀAxis Detector. 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 quadrupole.
General Experimental Procedure for the Synthesis of 2ꢀAminobiaryls (1bꢀ1h). A
Representative Experimental Procedure for the Synthesis of 5ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀ
amine (1b).
An ovenꢀdried 100 mL round bottom flask equipped with a magnetic stir bar was charged with
Pd(PPh3)4 (116 mg, 2 mol%) in toluene:ethanol:H2O (5:2:1; 58 mL in total). The 2ꢀbromoꢀ4ꢀ
methylaniline (0.6 mL, 5 mmol, 1 equiv), K2CO3 (2.76 g, 4 equiv), and phenylboronic acid (915
mg, 1.5 equiv) were added to it. The round bottom flask connected with a reflux condenser was
placed in the oil bath which was preheated at 100 °C and stirred for 16 h. The progress of the
reaction was monitored by TLC and gas chromatography. After completion, the reaction mixture
was diluted with dichloromethane (50 mL) and washed with brine (3 x 20 mL). Then, the organic
layers were combined, dried over anhydrous MgSO4, and concentrated in rotary evaporator. The
desired product 1b (817 mg, 89%) was purified by silica gel flash column chromatography using
hexane/EtOAc as the eluent.
5ꢀMethylꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1b):14 1H NMR (600 MHz, CDCl3) δ 7.51 – 7.45 (m, 4H),
7.37 (tt, J = 6.9, 1.7 Hz, 1H), 7.01 (d, J = 7.9 Hz, 1H), 6.99 (s, 1H) 6.72 (d, J = 7.9 Hz, 1H), 3.66
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(bs, 2H), 2.32 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 141.0, 139.7, 131.0, 129.1, 129.0, 128.8,
127.8, 127.7, 127.1, 115.8, 20.5; IR (neat): νmax = 3447, 3364, 3019, 2919, 1619, 1505, 1295,
814, 702 cmꢀ1; Rf 0.51 (hex/EtOAc, 4/1).
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5ꢀFluoroꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1c):19 1H NMR (600 MHz, CDCl3) δ 7.49 – 7.43 (m, 4H),
7.38 (tt, J = 6.7, 6.5 Hz, 1H), 6.90 – 6.86 (m, 2H), 6.70 (dd, J = 9.5, 4.8 Hz, 1H), 3.64 (bs, 2H);
13C NMR (151 MHz, CDCl3) δ 156.3 (d, J = 236.4 Hz), 139.6, 138.6, 128.9, 128.9, 128.7 (d, J
= 7.1 Hz), 127.6, 116.6 (d, J = 22.4 Hz), 116.4 (d, J = 7.7 Hz), 114.9 (d, J = 22.2 Hz); IR (neat):
νmax = 3454, 3369, 3057, 1600, 1504, 1270, 1178, 702 cmꢀ1; Rf 0.41 (hex/EtOAc, 4/1).
3'ꢀChloroꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1d):20 1H NMR (600 MHz, CDCl3) δ 7.50 (s, 1H), 7.39 –
7.35 (m, 2H), 7.30 (dd, J = 7.2, 7.2 Hz, 1H), 7.18 (dd, J = 7.7, 7.4 Hz, 1H), 7.10 (d, J = 7.7 Hz,
13
1H), 6.83 (dd, J = 7.8, 7.4 Hz, 1H), 6.77 (d, J = 7.8 Hz, 1H), 3.74 (bs, 2H); C NMR (151
MHz, CDCl3) δ 143.4, 141.4, 134.7, 130.4, 130.1, 129.2, 129.0, 127.3, 127.3, 126.2, 118.8,
115.8; IR (neat): νmax = 3461, 3374, 3060, 1614, 1468, 1294, 745 cmꢀ1; Rf 0.51 (hex/EtOAc,
4/1).
4'ꢀ(tertꢀButyl)ꢀ5ꢀfluoroꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1e):21 1H NMR (600 MHz, CDCl3) δ 7.47 (d,
J = 8.2 Hz, 2H), 7.37 (d, J = 8.2 Hz, 2H), 6.89 – 6.83 (m, 2H), 6.69 (dd, J = 8.6, 4.9 Hz, 1H),
13
3.63 (bs, 2H), 1.36 (s, 9H); C NMR (151 MHz, CDCl3) δ 156.3 (d, J = 236.4 Hz), 150.5,
139.7, 135.5, 128.7 (d, J = 7.1 Hz), 128.5, 125.8, 116.6 (d, J = 22.3 Hz), 116.3 (d, J = 7.7 Hz),
114.6 (d, J = 22.2 Hz), 34.6, 31.3; IR (neat): νmax = 3369, 2962, 1611, 1494, 1268, 1177, 840
cmꢀ1; Rf 0.49 (hex/EtOAc, 4/1).
Methyl 6ꢀaminoꢀ4'ꢀchloroꢀ[1,1'ꢀbiphenyl]ꢀ3ꢀcarboxylate (1f):22 1H NMR (600 MHz, CDCl3)
δ 7.83 (dd, J = 8.5, 2.0 Hz, 1H), 7.78 (d, J = 1.9 Hz, 1H), 7.41 (d, J = 8.4 Hz, 2H), 7.36 (d, J =
8.4 Hz, 2H), 6.72 (d, J = 8.4 Hz, 1H), 4.19 (bs, 2H), 3.85 (s, 3H); 13C NMR (151 MHz, CDCl3)
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δ 167.1, 148.0, 136.8, 133.6, 132.3, 130.8, 130.4, 129.2, 125.1, 119.8, 114.6, 51.7; IR (neat):
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ν
max = 3480, 3365, 3220, 2949, 1694, 1615, 1293, 1235, 835, 770, 739 cmꢀ1; Rf 0.27 (hex/EtOAc,
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4/1).
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4'ꢀ(tertꢀButyl)ꢀ5ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1g):11 1H NMR (600 MHz, CDCl3) δ 7.53
(d, J = 8.5 Hz, 2H), 7.46 (d, J = 8.5 Hz, 2H), 7.04 (s, 1H), 7.03 (d, J = 7.7 Hz, 1H), 6.74 (d, J =
13
7.7 Hz, 1H), 3.69 (bs, 2H), 2.35 (s, 3H), 1.44 (s, 9H); C NMR (151 MHz, CDCl3) δ 149.9,
141.2, 136.7, 131.1, 128.8, 128.8, 127.8, 127.7, 125.7, 115.8, 34.6, 31.5, 20.5; IR (neat): νmax
3445, 3362, 2960, 1617, 1498, 1268, 811, 729 cmꢀ1; Rf 0.57 (hex/EtOAc, 4/1).
=
4'ꢀChloroꢀ5ꢀmethylꢀ[1,1'ꢀbiphenyl]ꢀ2ꢀamine (1h):14 1H NMR (600 MHz, CDCl3) δ 7.72 (m,
4H), 7.32 (d, J = 8.1 Hz, 1H), 7.26 (s, 1H), 6.99 (d, J = 8.1 Hz, 1H), 3.90 (bs, 2H), 2.63 (s, 3H);
13C NMR (151 MHz, CDCl3) δ 141.1, 138.2, 133.0, 130.9, 130.6, 129.5, 129.0, 128.0, 126.4,
116.1, 20.5; IR (neat): νmax = 3445, 3363, 3014, 2918, 1618, 1482, 1089, 812 cmꢀ1; Rf 0.51
(hex/EtOAc, 4/1).
General Experimental Procedure for the Synthesis of Polycyclic (Hetero)Aromatics (3, 6, 8
and 20). A Representative Experimental Procedure for the Synthesis of 9ꢀ
phenylphenanthrene (3aa).
An ovenꢀdried tube equipped with a magnetic stir bar was charged with 1a (85 mg, 0.5 mmol,
1.0 equiv), 2a (77 mg, 0.75 mmol, 1.5 equiv), facꢀIr(ppy)3 (1 mg, 0.3 mol%), and MeCN (1.0 M,
0.5 mL). Next, tBuONO (77 mg, 0.75 mmol, 1.5 equiv) was added, and the tube was sealed with
a silicone septum screw cap and irradiated by blue LEDs (7 W) at room temperature. The
reaction progress was monitored by TLC and gas chromatography. After completion of the
reaction, the mixture was diluted with DCM and filtered. The filtrate was concentrated by rotary
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evaporator to give a residue that was subjected to flash column chromatography (SiO2,
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hexane/ethyl acetate) to afford pure 9ꢀphenylphenanthrene 3aa (99 mg, 78%).
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9ꢀPhenylphenanthrene (3aa):14 1H NMR (600 MHz, CDCl3) δ 8.80 (d, J = 8.3 Hz, 1H), 8.74
(d, J = 8.2 Hz, 1H), 7.94 (d, J = 8.3 Hz, 1H), 7.92 (d, J = 7.9 Hz, 1H), 7.71 (s, 1H), 7.69 (dd, J =
6.9, 6.9 Hz, 1H), 7.68 (d, J = 6.9 Hz, 1H) 7.64 (dd, J = 7.9, 6.9 Hz, 1H), 7.59 – 7.52 (m, 5H),
7.48 (tt, J = 7.3, 7.2 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 141.0, 139.0, 131.8, 131.4, 130.8,
130.3, 130.2, 128.9, 128.5, 127.7, 127.6, 127.1, 127.1, 126.8, 126.71, 126.65, 123.1, 122.7; IR
(neat): νmax = 3057, 3021, 1594, 1491, 1451, 725, 701 cmꢀ1; Rf 0.59 (hex/EtOAc, 8/1).
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9ꢀ(pꢀTolyl)phenanthrene (3ab):14 1H NMR (600 MHz, CDCl3) δ 8.85 (dd, J = 8.3 Hz, 1H),
8.79 (dd, J = 8.1 Hz, 1H), 8.07 (d, J = 8.3 Hz, 1H), 7.97 (d, J = 7.4 Hz, 1H), 7.78 (s, 1H), 7.76 –
7.71 (m, 2H), 7.69 (dd, J = 7.4, 6.8 Hz, 1H), 7.62 (dd, J = 8.1, 6.8 Hz, 1H), 7.55 (d, J = 7.7 Hz,
2H), 7.42 (d, J = 7.7 Hz, 2H), 2.56 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 138.9, 138.0, 137.2,
131.8, 131.5, 130.8, 130.13, 130.09, 129.2, 128.8, 127.6, 127.2, 127.0, 126.7, 126.63, 126.58,
123.1, 122.7, 21.5; IR (neat): νmax = 3020, 2918, 1509, 1492, 906, 819, 723 cmꢀ1; Rf 0.49
(hex/EtOAc, 8/1).
9ꢀ(4ꢀMethoxyphenyl)phenanthrene (3ac):14 1H NMR (600 MHz, CDCl3) δ 8.79 (d, J = 8.2
Hz, 1H), 8.73 (d, J = 8.2 Hz, 1H), 7.97 (d, J = 8.3 Hz, 1H), 7.90 (d, J = 7.7 Hz, 1H), 7.70 – 7.65
(m, 3H), 7.62 (dd, J = 8.0, 7.7 Hz, 1H), 7.56 (dd, J = 8.2, 8.0 Hz, 1H), 7.49 (d, J = 8.6 Hz, 2H),
7.07 (d, J = 8.6 Hz, 2H), 3.92 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 159.3, 138.6, 133.4,
131.9, 131.6, 131.3, 130.9, 130.1, 128.8, 127.66, 127.65, 127.2, 127.0, 126.7, 126.6, 123.1,
122.7, 114.0, 55.6; IR (neat): νmax = 3060, 2954, 2834, 1608, 1507, 1240, 1176, 1032, 725 cmꢀ1;
Rf 0.46 (hex/EtOAc, 8/1).
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9ꢀ(4ꢀFluorophenyl)phenanthrene (3ad):14 1H NMR (600 MHz, CDCl3) δ 8.80 (d, J = 8.3 Hz,
1H), 8.74 (d, J = 8.3 Hz, 1H), 7.90 (dd, J = 8.3, 7.9 Hz, 2H), 7.71 – 7.68 (m, 2H), 7.68 (s, 1H),
7.64 (dd, J = 7.9, 7.6 Hz, 1H), 7.57 (dd, J = 7.1, 6.9 Hz, 1H), 7.52 (dd, J = 8.5, 8.1 Hz, 2H), 7.23
(dd, J = 8.7, 8.1 Hz, 2H); 13C NMR (151 MHz, CDCl3) δ 162.5 (d, J = 246.5 Hz), 137.9, 136.9
(d, J = 3.4 Hz), 131.8 (d, J = 7.9 Hz), 131.7, 131.3, 130.8, 130.2, 128.8, 127.9, 127.1, 126.91,
126.88, 126.8, 126.7, 123.2, 122.8, 115.4 (d, J = 21.3 Hz); IR (neat): νmax = 3062, 2926, 1605,
1505, 1219, 834, 726 cmꢀ1; Rf 0.49 (hex/EtOAc, 8/1).
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9ꢀ(2ꢀ(Trifluoromethyl)phenyl)phenanthrene (3ae):23 1H NMR (600 MHz, CDCl3) δ 8.78 (d, J
= 8.3 Hz, 1H), 8.75 (d, J = 8.3 Hz, 1H), 7.89 (dd, J = 8.6, 8.3 Hz, 2H), 7.71 (dd, J = 8.0, 7.2 Hz,
1H), 7.68 – 7.62 (m, 4H), 7.59 (dd, J = 7.7, 7.7 Hz, 1H), 7.50 (dd, J = 7.7, 7.5 Hz, 1H), 7.43 (d, J
13
= 7.5 Hz, 1H), 7.39 (d, J = 8.2 Hz, 1H); C NMR (151 MHz, CDCl3) δ 139.5, 135.6, 133.0,
132.0, 131.4, 131.2, 130.43, 130.40, 130.2 (q, J = 30.2 Hz, 1H), 129.0, 128.07, 128.05, 128.0,
127.3, 127.1, 126.70, 126.65, 126.4 (q, J = 5.2 Hz, 1H), 124.3 (q, J = 274.5 Hz, 1H), 122.9,
122.8; IR (neat): νmax = 3063, 1599, 1314, 1174, 1126, 767, 747 cmꢀ1; Rf 0.51 (hex/EtOAc, 8/1)
Methyl phenanthreneꢀ9ꢀcarboxylate (3af):14 1H NMR (600 MHz, CDCl3) δ 8.96 (d, J = 9.7
Hz, 1H), 8.72 (d, J = 9.1 Hz, 1H), 8.67 (d, J = 8.3 Hz, 1H), 8.48 (s, 1H), 7.95 (d, J = 7.9 Hz, 1H),
7.74 (dd, J = 8.3, 8.0 Hz, 1H), 7.72 – 7.68 (m, 2H), 7.63 (dd, J = 8.0, 7.9 Hz, 1H), 4.06 (s, 3H);
13C NMR (151 MHz, CDCl3) δ 168.2, 132.6, 132.3, 130.8, 130.2, 130.1, 129.2, 129.1, 127.6,
127.2, 127.1, 126.8, 126.3, 123.0, 122.8, 52.4; IR (neat): νmax = 3060, 2948, 1712, 1528, 1445,
1252, 1210, 1026, 742 cmꢀ1; Rf 0.36 (hex/EtOAc, 8/1).
Diethyl phenanthreneꢀ9,10ꢀdicarboxylate (3ag):14 1H NMR (600 MHz, CDCl3) δ 8.72 (d, J =
8.3 Hz, 2H), 8.17 (d, J = 8.2 Hz, 2H), 7.75 (dd, J = 8.3, 8.1 Hz, 2H), 7.7 (dd, J = 8.2, 8.1 Hz,
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2H), 4.52 (q, J = 7.2 Hz, 4H), 1.46 (t, J = 7.2 Hz, 6H); C NMR (151 MHz, CDCl3) δ 168.1,
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131.2, 130.1, 128.5, 127.8, 127.4, 127.0, 123.1, 62.2, 14.4; IR (neat): νmax = 2983, 1728, 1448,
1251, 1195, 1024, 761, 727 cmꢀ1; Rf 0.41 (hex/EtOAc, 4/1).
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Ethyl 10ꢀphenylphenanthreneꢀ9ꢀcarboxylate (3ah):14 1H NMR (600 MHz, CDCl3) δ 8.77 (d,
J = 8.6 Hz, 2H), 7.93 (d, J = 8.0 Hz, 1H), 7.73ꢀ7.68 (m, 2H), 7.67ꢀ7.62 (m, 2H), 7.54 – 7.43 (m,
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6H), 4.11 (q, J = 7.1 Hz, 2H), 0.97 (t, J = 7.1 Hz, 3H); C NMR (151 MHz, CDCl3) δ 169.2,
138.1, 136.4, 130.8, 130.64, 130.60, 130.3, 129.9, 128.0, 127.9, 127.78, 127.76, 127.41, 127.39,
127.0, 126.8, 125.9, 122.8, 122.6, 61.1, 13.7; IR (neat): νmax = 2924, 1724, 1379, 1223, 1033,
760 cmꢀ1; Rf 0.38 (hex/EtOAc, 8/1).
9ꢀThienylphenanthrene (3ai): yellow solid; m. p. 57ꢀ58 °C; 1H NMR (600 MHz, CDCl3) δ
8.78 (d, J = 8.3 Hz, 1H), 8.72 (d, J = 8.4 Hz, 1H), 8.07 (d, J = 8.1 Hz, 1H), 7.89 (d, J = 7.8 Hz,
1H), 7.77 (s, 1H), 7.71 – 7.66 (m, 2H), 7.62 (dd, J = 7.8, 7.7 Hz, 1H), 7.58 (dd, J =8.1, 7.9 Hz,
1H), 7.50 (dd, J = 4.8, 3.0 Hz, 1H), 7.47 (dd, J = 3.0, 1.2 Hz, 1H), 7.36 (dd, J = 4.8, 1.2 Hz, 1H);
13C NMR (151 MHz, CDCl3) δ 141.4, 133.8, 131.8, 131.4, 130.8, 130.2, 129.9, 128.8, 127.8,
127.1, 126.89, 126.85, 126.8, 126.7, 125.6, 123.9, 123.1, 122.8; IR (neat): νmax = 3075, 2925,
1598, 1492, 1449, 723, 661 cmꢀ1; HRMS m/z (EI) calc. for C18H12S [M+] 260.0660, found
260.0657; Rf 0.49 (hex/EtOAc, 8/1).
2ꢀ(Phenanthrenꢀ9ꢀyl)pyridine (3aj):14 1H NMR (600 MHz, CDCl3) δ 8.83 (d, J = 4.9 Hz, 1H),
8.79 (d, J = 8.3 Hz, 1H), 8.73 (d, J = 8.3 Hz, 1H), 8.08 (d, J = 8.1 Hz, 1H), 7.93 (d, J = 7.4 Hz,
1H), 7.88 – 7.83 (m, 2H), 7.72 – 7.60 (m, 4H), 7.58 (dd, J = 7.7, 7.4 Hz, 1H), 7.37 (dd, J = 7.1,
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4.9 Hz, 1H); C NMR (151 MHz, CDCl3) δ 159.6, 149.8, 137.4, 136.7, 131.6, 131.0, 130.7,
130.5, 129.2, 128.7, 127.3, 127.0, 126.9, 126.8, 126.7, 125.3, 123.2, 122.8, 122.4; IR (neat):
νmax = 3057, 2925, 1585, 1470, 1429, 745, 725 cmꢀ1; Rf 0.31 (hex/EtOAc, 4/1).
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3ꢀMethylꢀ9ꢀphenylphenanthrene (3ba):11 1H NMR (600 MHz, CDCl3) δ 8.80 (d, J = 8.3 Hz,
1H), 8.55 (s, 1H), 7.96 (d, J = 8.2 Hz, 1H), 7.82 (d, J = 8.0 Hz, 1H), 7.69 (s, 1H), 7.67 (d, J = 8.2
Hz, 1H), 7.59 (d, J = 7.9 Hz, 2H), 7.57 – 7.52 (m, 3H), 7.49 (dd, J = 8.8, 7.9 Hz, 2H), 2.68 (s,
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3H); C NMR (151 MHz, CDCl3) δ 141.0, 137.8, 136.3, 131.3, 130.4, 130.1, 130.0, 129.5,
128.6, 128.5, 128.3, 127.4, 127.3, 126.9, 126.4, 126.2, 122.9, 122.3, 22.2; IR (neat): νmax
3054, 3021, 2920, 1735, 1598, 1448, 893, 748, 709 cmꢀ1; Rf 0.51 (hex/EtOAc, 4/1).
=
3ꢀFluoroꢀ9ꢀphenylphenanthrene (3ca):12 1H NMR (600 MHz, CDCl3) δ 8.64 (d, J = 8.4 Hz,
1H), 8.33 (dd, J = 11.0, 2.4 Hz, 1H), 7.92 (d, J = 8.0 Hz, 1H), 7.88 (dd, J = 8.8, 8.6 Hz, 1H), 7.69
– 7.66 (m, 2H), 7.57 (d, J = 8.0 Hz, 1H), 7.56 – 7.49 (m, 4H), 7.47 (t, J = 6.7 Hz, 1H), 7.38 (ddd,
J = 11.0, 8.6, 2.4 Hz, 1H); 13C NMR (151 MHz, CDCl3) δ 161.6 (d, J = 245.6 Hz), 140.6, 138.1,
131.43 (d, J = 8.4 Hz), 131.35, 130.7 (d, J = 8.9 Hz), 130.04, 130.01, 128.4, 128.3, 127.4, 127.1,
127.0, 126.8, 126.5, 123.1, 115.9 (d, J = 24.0 Hz), 107.7 (d, J = 22.3 Hz); IR (neat): νmax
3056, 2927, 1738, 1597, 1500, 771, 710 cmꢀ1; Rf 0.62 (hex/EtOAc, 8/1).
=
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2ꢀ(tertꢀButyl)ꢀ6ꢀfluoroꢀ10ꢀphenylphenanthrene (3ea): offꢀwhite solid; m. p. 120ꢀ121 °C; H
NMR (600 MHz, CDCl3) δ 8.57 (d, J = 8.7 Hz, 1H), 8.30 (d, J = 11.0 Hz, 1H), 7.96 (s, 1H),
7.86 (dd, J = 8.6, 8.4 Hz, 1H), 7.76 (d, J = 8.7 Hz, 1H), 7.65 (s, 1H), 7.57 (d, J = 7.0 Hz, 2H),
7.54 (dd, J = 7.5, 7.0 Hz, 2H), 7.48 (t, J = 7.5 Hz, 1H), 7.34 (dd, J = 8.6, 8.4 Hz, 1H), 1.36 (s,
9H); 13C NMR (151 MHz, CDCl3) δ 161.6 (d, J = 245.3 Hz), 150.0, 140.7, 138.2, 131.3 (d, J =
8.4 Hz), 131.1, 130.6 (d, J = 8.9 Hz), 130.0, 128.3, 128.0, 127.9, 127.4, 126.8, 124.7, 122.9,
122.7, 115.5 (d, J = 23.9 Hz), 107.4 (d, J = 22.3 Hz), 35.0, 31.3; IR (neat): νmax = 3057, 2962,
1595, 1492, 1181, 701 cmꢀ1; HRMS m/z (EI) calc. for C24H21F [M+] 328.1627, found 328.1628;
Rf 0.68 (hex/EtOAc, 8/1).
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Methyl 7ꢀchloroꢀ9ꢀphenylphenanthreneꢀ3ꢀcarboxylate (3fa): pale green solid; m. p. 171ꢀ172 °
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C; H NMR (600 MHz, CDCl3) δ 9.39 (s, 1H), 8.79 (d, J = 8.9 Hz, 1H), 8.23 (d, J = 8.3 Hz,
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1H), 7.92 (d, J = 8.3 Hz, 1H), 7.89 (d, J = 2.2 Hz, 1H), 7.73 (s, 1H), 7.67 (dd, J = 8.9, 2.2 Hz,
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1H), 7.58 – 7.47 (m, 5H), 4.04 (s, 3H); C NMR (151 MHz, CDCl3) δ 167.2, 140.4, 139.6,
134.2, 133.2, 132.4, 129.8, 129.3, 128.94, 128.86, 128.6, 128.2, 128.1, 128.0, 127.6, 127.0,
126.2, 125.0, 124.8, 52.4; IR (neat): νmax = 3025, 2950, 1715, 1436, 1271, 906, 699 cmꢀ1;
HRMS m/z (EI) calc. for C22H15ClO2 [M+] 346.0761, found 346.0758; Rf 0.35 (hex/EtOAc,
8/1).
2ꢀ(tertꢀButyl)ꢀ6ꢀmethylꢀ10ꢀphenylphenanthrene (3ga):11 1H NMR (600 MHz, CDCl3) δ 8.69
(d, J = 8.7 Hz, 1H), 8.48 (s, 1H), 7.94 (d, J = 2.0 Hz, 1H), 7.78 (d, J = 8.0 Hz, 1H), 7.73 (dd, J =
8.7, 2.0 Hz, 1H), 7.64 (s, 1H), 7.58 (d, J = 8.0 Hz, 2H), 7.52 (dd, J = 8.0, 7.4 Hz, 2H), 7.45 (t, J =
7.4 Hz, 1H), 7.42 (d, J = 8.0 Hz, 1H), 2.65 (s, 3H), 1.35 (s, 9H); 13C NMR (151 MHz, CDCl3) δ
149.1, 141.1, 137.9, 136.1, 130.9, 130.0, 129.9, 129.3, 128.4, 128.20, 128.16, 128.15, 127.4,
127.2, 124.4, 122.61, 122.59, 122.1, 34.9, 31.3, 22.2; IR (neat): νmax = 3053, 2961, 1739, 1617,
1597, 1371, 897, 701 cmꢀ1; Rf 0.68 (hex/EtOAc, 8/1).
2ꢀChloroꢀ6ꢀmethylꢀ10ꢀphenylphenanthrene (3ha):11 1H NMR (600 MHz, CDCl3) δ 8.68 (d, J
= 8.9 Hz, 1H), 8.44 (s, 1H), 7.88 (d, J = 1.9 Hz, 1H), 7.79 (d, J = 8.2 Hz, 1H), 7.68 (s, 1H), 7.59
(dd, J = 8.9, 1.9 Hz, 1H), 7.53 (m, 4H), 7.48 (dd, J = 5.76, 2.0 Hz, 1H), 7.46 (d, J = 8.2 Hz, 1H)
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2.65 (s, 3H); C NMR (151 MHz, CDCl3) δ 140.2, 136.9, 136.8, 132.5, 132.4, 130.0, 129.6,
129.4, 128.9, 128.7, 128.6, 128.53, 128.48, 127.5, 126.7, 125.9, 124.5, 122.2, 22.2; IR (neat):
νmax = 3055, 2920, 1734, 1597, 1492, 895, 820, 701 cmꢀ1; Rf 0.62 (hex/EtOAc, 8/1).
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9ꢀPhenylꢀ10ꢀ(phenylethynyl)phenanthrene (6):14 1H NMR (600 MHz, CDCl3) δ 8.78 – 8.73
(m, 2H), 8.65 (d, J = 9.4 Hz, 1H), 7.76 – 7.72 (m, 2H), 7.67 (m, 2H), 7.59 – 7.55 (m, 2H), 7.55 –
7.49 (m, 4H), 7.30 – 7.27 (m, 3H), 7.27 – 7.23 (m, 2H); 13C NMR (151 MHz, CDCl3) δ 143.2,
140.0, 131.63, 131.59, 130.94, 130.89, 130.4, 129.9, 128.5, 128.4, 128.3, 128.0, 127.7, 127.6,
127.5, 127.4, 127.3, 127.0, 123.7, 122.9, 122.8, 119.3, 98.4, 88.0; IR (neat): νmax = 3061, 1597,
1490, 1449, 754, 724, 690 cmꢀ1; Rf 0.51 (hex/EtOAc, 8/1).
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9ꢀ(4ꢀEthynylphenyl)phenanthrene (8): paleꢀgreen oil; 1H NMR (600 MHz, CDCl3) δ 8.79 (d,
J = 8.1 Hz, 1H), 8.73 (d, J = 8.3 Hz, 1H), 7.91 (d, J = 7.6 Hz, 1H), 7.89 (d, J = 8.2 Hz, 1H), 7.71
– 7.68 (m, 3H), 7.67 (d, J = 8.0 Hz, 2H), 7.64 (dd, J = 7.6, 7.2 Hz, 1H), 7.56 (dd, J = 8.1, 7.2 Hz,
1H), 7.53 (d, J = 8.0 Hz, 2H), 3.18 (s, 1H); 13C NMR (151 MHz, CDCl3) δ 141.6, 138.1, 132.3,
131.6, 130.94, 130.85, 130.3, 128.9, 127.78, 127.77, 127.1, 127.0, 126.9, 126.83, 126.80, 123.2,
122.8, 121.4, 83.8, 77.9; HRMS m/z (EI) calc. for C22H14 [M+] 278.1096, found 278.1095; IR
(neat): νmax = 3288, 3061, 2924, 2106, 1504, 838, 749, 733 cmꢀ1; Rf 0.54 (hex/EtOAc, 8/1).
5ꢀPhenylbenzo[f]quinoline (20aa):24 1H NMR (600 MHz, CDCl3) δ 9.04 – 8.99 (m, 2H), 8.64
(d, J = 8.0 Hz, 1H), 8.02 (s, 1H), 7.97 (d, J = 7.5 Hz, 1H), 7.79 (d, J = 7.7 Hz, 2H), 7.71 (dd, J =
7.5, 6.8 Hz, 1H), 7.68 (dd, J = 7.1, 6.8 Hz, 1H), 7.59 – 7.54 (m, 3H), 7.48 (dd, J = 7.4, 7.4 Hz,
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1H); C NMR (151 MHz, CDCl3) δ 149.6, 146.9, 139.9, 139.5, 131.6, 131.3, 130.9, 130.8,
129.7, 129.0, 128.2, 127.7, 127.6, 127.1, 126.0, 122.6, 121.3; IR (neat): νmax = 3056, 1740,
1599, 1442, 1239, 750, 702 cmꢀ1; Rf 0.68 (hex/EtOAc, 2/1).
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5ꢀPhenylbenzo[h]isoquinoline (20aa′): brown oil; H NMR (600 MHz, CDCl3) δ 10.13 (s,
1H), 8.84 (d, J = 8.1 Hz, 1H), 8.66 (d, J = 5.7 Hz, 1H), 7.94 (d, J = 7.9 Hz, 1H), 7.90 (s, 1H),
7.78 – 7.74 (m, 2H), 7.69 (dd, J = 8.1, 7.0 Hz, 1H), 7.54 (m, 4H), 7.49 (dd, J = 6.0, 2.6 Hz, 1H);
13C NMR (151 MHz, CDCl3) δ 147.3, 145.5, 139.3, 137.3, 135.3, 131.93, 131.86, 130.1,
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129.23, 129.16, 128.8, 128.1, 128.0, 127.9, 125.5, 122.0, 119.6; IR (neat): νmax = 3057, 2925,
1717, 1600, 1443, 1238, 750, 702 cmꢀ1; HRMS m/z (EI) calc. for C19H13N [M+] 255.1048,
found 255.1047; Rf 0.38 (hex/EtOAc, 1/1).
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MHz, CDCl3) δ 9.03 (d, J = 8.3 Hz, 1H), 9.00 (d, J = 4.3 Hz, 1H), 8.65 (d, J = 7.9 Hz, 1H), 7.99
(s, 1H), 7.95 (d, J = 7.4 Hz, 1H), 7.71 (d, J = 8.5 Hz, 2H), 7.70 – 7.65 (m, 2H), 7.58 (dd, J = 8.3,
4.3 Hz, 1H), 7.07 (d, J = 8.5 Hz, 2H), 3.90 (s, 3H); 13C NMR (151 MHz, CDCl3) δ 159.3, 149.6,
147.1, 139.1, 132.3, 131.9, 131.8, 131.0, 130.9, 129.6, 128.9, 127.7, 127.0, 126.1, 122.6, 121.3,
113.8, 55.6; IR (neat): νmax = 2925, 1508, 1245, 1034, 831, 751 cmꢀ1; HRMS m/z (EI) calc. for
C20H15NO [M+] 285.1154, found 285.1152; Rf 0.68 (hex/EtOAc, 2/1).
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(600 MHz, CDCl3) δ 10.11 (s, 1H), 8.82 (d, J = 8.2 Hz, 1H), 8.66 (d, J = 5.6 Hz, 1H), 7.92 (d, J
= 7.8 Hz, 1H), 7.86 (s, 1H), 7.77 (d, J = 5.6 Hz, 1H), 7.73 (dd, J = 8.2, 7.1 Hz, 1H), 7.67 (dd, J =
7.8, 7.1 Hz, 1H), 7.45 (d, J = 8.6 Hz, 2H), 7.07 (d, J = 8.6 Hz, 2H), 3.91 (s, 3H); 13C NMR (151
MHz, CDCl3) δ 159.6, 147.2, 145.3, 136.9, 135.6, 132.0, 131.71, 131.70, 131.5, 131.2, 129.1,
129.0, 127.9, 125.5, 122.0, 119.6, 114.2, 55.6; IR (neat): νmax = 3037, 2925, 1609, 1512, 1246,
1032, 834, 751 cmꢀ1; HRMS m/z (EI) calc. for C20H15NO [M+] 285.1154, found 285.1152; Rf
0.32 (hex/EtOAc, 1/1).
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5ꢀ(4ꢀFluorophenyl)benzo[f]quinoline (20ad): yellow solid; m. p. 162ꢀ163 °C; H NMR (600
MHz, CDCl3) δ 9.03 (d, J = 8.4 Hz, 1H), 8.99 (d, J = 4.3 Hz, 1H), 8.66 (d, J = 8.1 Hz, 1H), 7.98
(s, 1H), 7.96 (d, J = 7.7 Hz, 1H), 7.75 – 7.70 (m, 3H), 7.69 (dd, J = 7.9, 7.7 Hz, 1H), 7.59 (dd, J
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= 8.4, 4.3 Hz, 1H), 7.21 (dd, J = 8.8, 8.5 Hz, 2H); 13C NMR (151 MHz, CDCl3) δ 162.7 (d, J =
246.5 Hz), 149.6, 146.8, 138.4, 135.8 (d, J = 3.3 Hz), 132.4 (d, J = 7.9 Hz), 131.6, 131.3, 131.1,
129.7, 129.0, 127.8, 127.3, 126.1, 122.7, 121.4, 115.1 (d, J = 21.4 Hz); IR (neat): νmax = 3062,
2925, 1590, 1508, 1222, 834, 749 cmꢀ1; HRMS m/z (EI) calc. for C19H12FN [M+] 273.0954,
found 273.0950; Rf 0.58 (hex/EtOAc, 2/1).
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CDCl3) δ 10.11 (s, 1H), 8.82 (d, J = 8.3 Hz, 1H), 8.67 (d, J = 5.6 Hz, 1H), 7.93 (d, J = 7.5 Hz,
1H), 7.86 (s, 1H), 7.75 (dd, J = 7.5, 7.0 Hz, 1H), 7.70 – 7.67 (m, 2H), 7.49 (dd, J = 8.8, 8.7 Hz,
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2H), 7.23 (dd, J = 8.7, 8.2 Hz, 2H); C NMR (151 MHz, CDCl3) δ 162.8 (d, J = 247.6 Hz),
147.3, 145.5, 136.2, 135.3, 135.2 (d, J = 3.4 Hz), 132.0, 131.8, 131.7 (d, J = 8.0 Hz), 129.2,
129.16, 128.17, 128.0, 125.4, 122.0, 119.4, 115.8 (d, J = 21.5 Hz); HRMS m/z (EI) calc. for
C19H12FN [M+] 273.0954, found 273.0950; Rf 0.28 (hex/EtOAc, 1/1).
4ꢀPhenylnaphtho[2,1ꢀb]furan (20ba): yellow sticky solid; 1H NMR (600 MHz, CDCl3) δ 8.16
(d, J = 8.2 Hz, 1H), 8.00 (d, J = 8.2 Hz, 1H), 7.96 (d, J = 7.8 Hz, 2H), 7.87 (s, 1H), 7.84 (d, J =
2.0 Hz, 1H), 7.59 (dd, J = 8.2, 8.0 Hz, 1H), 7.55 (dd, J = 7.8, 7.5 Hz, 2H), 7.52 (dd, J = 8.2, 8.0
Hz, 1H), 7.45 (dd, J = 7.5, 7.5 Hz, 1H), 7.34 (d, J = 2.0 Hz, 1H); 13C NMR (151 MHz, CDCl3)δ
150.7, 144.5, 136.7, 131.1, 129.04, 129.02, 128.9, 128.2, 127.5, 126.9, 126.4, 125.1, 124.3,
123.7, 123.5, 106.0; IR (neat): νmax = 3062, 2925, 1590, 1508, 1222, 834, 749 cmꢀ1; HRMS m/z
(EI) calc. for C18H12O [M+] 244.0888, found 244.0891; Rf 0.51 (hex/EtOAc, 4/1).
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4ꢀ(4ꢀMethoxyphenyl)naphtho[2,1ꢀb]furan (20bc): brown sticky solid; H NMR (600 MHz,
CDCl3) δ 8.16 (d, J = 8.1 Hz, 1H), 7.99 (d, J = 8.1 Hz, 1H), 7.94 (d, J = 8.8 Hz, 2H), 7.84 – 7.83
(m, 2H), 7.59 (dd, J = 8.1, 8.1 Hz, 1H), 7.52 (dd, J = 8.1, 8.1 Hz, 1H), 7.34 (d, J = 2.0 Hz, 1H),
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7.10 (d, J = 8.8 Hz, 2H), 3.91 (s, 3H); C NMR (151 MHz, CDCl3) δ 159.7, 150.7, 144.4,
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131.1, 130.1, 129.1, 128.9, 127.2, 126.5, 126.1, 125.0, 123.6, 123.5, 123.4, 114.3, 106.0, 55.6;
IR (neat): νmax = 2925, 2851, 1609, 1510, 1250, 1033, 831, 751 cmꢀ1; HRMS m/z (EI) calc. for
C19H14O2 [M+] 274.0994, found 274.0991; Rf 0.69 (hex/EtOAc, 4/1).
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4ꢀ(4ꢀFluorophenyl)naphtho[2,1ꢀb]furan (20bd): white sticky solid; H NMR (600 MHz,
CDCl3) δ 8.15 (d, J = 8.0 Hz, 1H), 7.99 (d, J = 8.0 Hz, 1H), 7.93 (dd, J = 8.6, 8.5 Hz, 2H), 7.83
(d, J = 1.8 Hz, 1H), 7.81 (s, 1H), 7.60 (dd, J = 8.0, 7.2 Hz, 1H), 7.52 (dd, J = 8.0, 7.2 Hz, 1H),
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7.34 (d, J = 1.8 Hz, 1H), 7.23 (dd, J = 8.6, 8.5 Hz, 2H); C NMR (151 MHz, CDCl3) δ 162.9
(d, J = 247.7 Hz), 150.5, 144.6, 132.7 (d, J = 3.3 Hz), 131.0, 130.6 (d, J = 8.0 Hz), 129.0, 127.4,
126.5, 125.8, 125.2, 124.1, 123.7, 123.5, 115.8 (d, J = 21.4 Hz), 106.1; IR (neat): νmax = 3056,
2924, 2850, 1508, 1233, 833, 749 cmꢀ1; HRMS m/z (EI) calc. for C18H11FO [M+] 262.0794,
found 262.0796; Rf 0.66 (hex/EtOAc, 4/1).
6ꢀPhenylbenzo[b]naphtho[2,1ꢀd]thiophene (20ca):2a 1H NMR (600 MHz, CDCl3) δ 8.20 (d, J
= 8.2 Hz, 1H), 7.94 (dd, J = 9.4, 8.2 Hz, 2H), 7.67 (s, 1H), 7.63 (dd, J = 7.7, 7.3 Hz, 1H), 7.59
(dd, J = 7.6, 7.2 Hz, 1H), 7.56 – 7.51 (m, 5H), 7.36 (dd, J = 8.2, 8.2 Hz, 1H), 7.15 – 7.09 (m,
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2H); C NMR (151 MHz, CDCl3) δ 141.5, 139.4, 138.4, 137.6, 136.9, 132.7, 131.6, 130.9,
129.6, 128.8, 128.4, 128.0, 127.04, 126.95, 126.8, 125.8, 125.0, 124.5, 124.1, 122.9; IR (neat):
νmax = 3055, 2921, 2849, 1492, 1431, 1248, 1029, 755 cmꢀ1; Rf 0.69 (hex/EtOAc, 4/1).
ASSOCIATED CONTENT
Supporting Information
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The Supporting Information is available free of charge on the ACS Publications website at DOI:
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1H and C NMR spectra for all 2ꢀaminobiaryls (1bꢀ1h), phenanthrene derivatives (3, 6 and 8)
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and polycyclic heteroaromatic compounds (20).
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AUTHOR INFORMATION
Corresponding Author
*Eꢀmail: ejcho@cau.ac.kr
Notes
The authors declare no competing financial interest.
ACKNOWLEDGEMENTS
This work was supported by the National Research Foundation of Korea (NRFꢀ
2014R1A1A1A05003274, NRFꢀ2014ꢀ011165, and NRFꢀ2012M3A7B4049657).
REFERENCES
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J. E. Angew. Chem. Int. Ed. 2008, 47, 452. (c) Wang, C.; Dong, H.; Hu, W.; Liu, Y.; Zhu, D.
Chem. Rev. 2012, 112, 2208.
(2) (a) Ferrara, G.; Jin, T.; Akhtaruzzaman, M.; Islam, A.; Han, L.; Jiang, H.; Yamamoto, Y.
Tetrahedron Lett. 2012, 53, 1946. (b) Li, J.; Hu, G.; Wang, N.; Hu, T.; Wen, Q.; Lu, P.; Wang, Y.
J. Org. Chem. 2013, 78, 3001. (c) Park, B.ꢀW.; Kwak, Y.ꢀH.; Lee, S.ꢀY.; Cho, S.ꢀJ. U.S. Pat.
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