Metal-free photocatalyzed cross coupling of aryl (heteroaryl) bromides with isonitriles

Article abstract of DOI:10.1016/j.tet.2017.10.074

A visible-light-catalyzed synthesis of 6-aryl substituted phenanthridines from aryl bromides and 2-isocyanobiphenyls at room temperature has been discovered. This metal-free cross-coupling reaction offers rapid and sustainable access to a series of struct

Full text of DOI:10.1016/j.tet.2017.10.074

Accepted Manuscript
Metal-free photocatalyzed cross coupling of aryl (heteroaryl) bromides with isonitriles
Xiangguang Li, Deqiang Liang, Wenzhong Huang, Huanli Sun, Lvsu Wang, Mengran
Ren, Baoling Wang, Yinhai Ma
PII:
S0040-4020(17)31120-1
10.1016/j.tet.2017.10.074
TET 29077
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 4 September 2017
Revised Date: 24 October 2017
Accepted Date: 30 October 2017
Please cite this article as: Li X, Liang D, Huang W, Sun H, Wang L, Ren M, Wang B, Ma Y, Metal-free
photocatalyzed cross coupling of aryl (heteroaryl) bromides with isonitriles, Tetrahedron (2017), doi:
10.1016/j.tet.2017.10.074.
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Graphical Abstract
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Metal-free photocatalyzed cross coupling of
aryl (heteroaryl) bromides with isonitriles
Leave this area blank for abstract info.
Xiangguang Li a,b, , Deqiang Liang a,b, Wenzhong Huang a,b, Huanli Sun a, Lvsu Wang a, Mengran Ren a,
Baoling Wang a,b and Yinhai Ma a
a Department of Chemical Science & Technology, Kunming University, Kunming 650214, China
bYunnan Engineering Technology Research Center for Plastic Films, Kunming University, Kunming 650214,
China
CO2Et
Me
Me
Et
N
HCl
O
N
H
Et
Ar Br
+
N
Ar
NC
Ar = aryl, heteroaryl
metal-free
room temperature

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Metal-free photocatalyzed cross coupling of aryl (heteroaryl) bromides with
isonitriles
Xiangguang Li a,b, , Deqiang Liang a,b, Wenzhong Huang a,b, Huanli Sun a, Lvsu Wang a, Mengran Ren a,
Baoling Wang a,b and Yinhai Ma a
aDepartment of Chemical Science & Technology, Kunming University, Kunming 650214, China
bYunnan Engineering Technology Research Center for Plastic Films, Kunming University, Kunming 650214, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A visible-light-catalyzed synthesis of 6-aryl substituted phenanthridines from aryl bromides and
2-isocyanobiphenyls at room temperature has been discovered. This metal-free cross-coupling
reaction offers rapid and sustainable access to a series of structurally complex and diverse
phenanthridines. The usage of inexpensive Rhodamine 6G as the catalyst with easy operation
makes this protocol very practical.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
6-Aryl substituted phenathridines
Metal-free reaction
Aryl bromides
Isonitriles
Visible light photocatalysis
1. Introduction
aryl substituted phenanthridines.
Visible-light is non-polluting, infinitely available and easy to
handle. Since the milestone made by Macmillan and Yoon in
2008, the use of visible light as a driving force for chemical
reactions has attracted a lot of scientific and technological
interest.6 Photoredox catalysis employing visible light has
recently emerged as a valuable platform for the design of unique
one-electron-transfer pathways that allow the invention of
valuable new chemical reactions.7 However, most of the
previously reported studies are based on the use of transition
metal (usually ruthenium and iridium) polypyridyl complexes.
Although there are many advantages related to the use of
ruthenium and iridium polypyridyl complexes in visible-light
photocatalysis, their exorbitant price and related environmental
pollution limited their further application in industrial processes.
Organic dyes, which are inexpensive and easily available, have
been used as a viable alternative in photoredox catalysis.8
Rhodamine 6G (Rh-6G) is a widely applied organic dye. Rh-6G
is converted to the corresponding excited radical anion [Rh-
6G•−]* upon irradiation with blue light (455 nm) in the presence
Nitrogen heterocycles are among the most important structural
classes of chemical substances, which are particularly widespread
prevalence in natural products, biologically active structures and
medicinally relevant compounds.1 Phenanthridines represent an
important class of nitrogen-containing heterocycles, which are
the basic constituents of numerous natural products, biologically
active alkaloids, functional materials and pharmaceuticals.2
Given the fact that the construction of 6-substituted
phenanthridines is
a successful strategy to improve its
performance, many C6-diversified phenanthridines, especially 6-
aryl substituted derivatives featuring good biological activities
have been documented over the last several years.3 Consequently,
the development of synthetic methods used for the preparation of
6-aryl substituted phenanthridines has received a lot of attention.4
Among the numerous methods that have been developed,
isonitrile insertion has emerged as a powerful strategy for their
preparation.5 In this field, aryl radicals easily add to the carbon
atom of isonitrile to form animidoyl radical intermediate, which
is able to undergo subsequent cyclization to eventually afford 6-
aryl substituted phenanthridines. In this context, numerous aryl
radical precursors have been reported, such as boronic acids,4g
hydrazines4e and aryl sulfonyl chlorides.4f Though, it is still
necessary to develop more aryl radical precursors to realize
isonitrile insertion via a radical process used for synthesis of 6-
———
of DIPEA (N,N-diisopropylethylamine) under
a nitrogen
atmosphere and has a reduction potential of ca. -2.4 V vs SCE,
which is sufficient to activate an aryl halide.9 The initial aryl
halide radical anion may cleave into a halide anion and an aryl
radical, which can further react with different coupling partners,
such as arenes,9 heteroarenes,10 alkenes,9 alkynes11 and trialkyl
Corresponding author. Tel.: +86-871-6509-8482; e-mail: lixiangguang@iccas.ac.cn.

2
Tetrahedron
ACCEPTED MANUSCRIPT
phosphites.12 We presumed that aryl isonitriles might serve as
4
PhCF3 as solvent
trace
good coupling partners to trap aryl radicals which can be easily
generated from aryl halides. Herein, we disclose our preliminary
results on the visible-light-promoted transformation of aryl
bromides and 2-isocyanobiphenyls towards the synthesis of 6-
aryl substituted phenanthridines.
5
with triethylamine (2.5 equiv) as base 39
6 c
with NaHCO3 (2.5 equiv) as base
in the absence of DIPEA
Ir(ppy)3 (10 mol%) as PC
Eosin Y (10 mol%) as PC
Rose Bengal (10 mol%) as PC
without PC
6
7
none
13
8
The significance of the present finding is threefold: 1) Simple
and readily available Rh-6G emerges as an efficient catalyst,
rather than a transition-metal catalyst, which is often expensive
with noble metal, and is intractable to be completely removed
from the products, especially in the synthesis of pharmaceutical
compounds, 2) visible-light is employed as a safe, renewable and
inexpensive source of chemical energy to facilitate the
construction of 6-aryl substituted phenanthridines and 3) readily
accessible aryl (heteroaryl) bromides are used as starting
materials.
9
trace
trace
0
10
11
12
13 d
in the absence of visible-light
none
0
62
a
Reaction conditions: 1a (0.3 mmol), 2a (0.35mmol), Rh-6G (10 mol%),
solvent (2.0 mL), DIPEA (0.75 mmol), in Ar atmosphere, room temperature,
d
5 W blue LED light for 20 h. b Isolated yield. c GC analysis. 1a (6.0 mmol),
2a (7.0 mmol), solvent (10 mL), DIPEA (15.0 mmol) for 48h. PC =
photocatalyst.
Having optimized the reaction conditions, we examined the
scope of the reaction of bromobenzene 2a with different 2-
isocyanobiphenyls 1 to define the scope of this transformation.
The isocyanides bearing either an electron-rich or an electron-
deficient substituent on the isocyano-bearing phenyl ring was
compatible under the standard conditions, leading to the desired
product 3ab-3ac in 60% and 68% yields, respectively (Table 2,
entries 1-2). Notably, the poly-substituted isocyanide 1d gave the
desired product 3ad with a good yield (Table 2, entry 3).
Interestingly, the introduction of heterocycles into this system
made this methodology more useful for the preparation of
pharmaceuticals and materials (Table 2, entry 4). Subsequently, a
series of functional groups on the non-isocyano bearing aromatic
ring were also evaluated, and good results were obtained. For
example, Cl and MeO groups provided the desired products with
good yields (Table 2, entries 5-6). It was found that the reactions
of 2-(2-isocyanophenyl)naphthalene 1h with bromobenzene 2a
proceeded well and gave the desired product 3ah in 58% yield. In
addition, when employing 2-isocyanobiphenyl derivative 1i as
the substrate, the reaction afforded the two regioisomers 3ia and
3ja in the ratio of 1 : 1.7 (Table 2, entry 8). Apart from 2-
isocyanobiphenyls, ethyl 2-isocyano-3-phenylbut-2-enoate 1k
smoothly reacted with 2a and gave the corresponding product
3ak in 77% yield (Table 2, entry 9).
Schem 1 Synthesis of 6-aryl substituted phenanthridines via cyclization of 2-
isocyanobiphenyls with aryl halides
2. Results and discussion
First,
visible-light
photoredox
cyclization
of
2-
isocyanobiphenyl 1a with bromobenzene 2a was selected as the
model to optimize conditions. Various solvents, photocatalysts,
and bases were examined at room temperature. Dimethyl
sulfoxide (DMSO) was found to be a good solvent for the
photoreaction (Table 1, entries1-4). It was found that DIPEA was
superior to other bases (Table 1, entries 1, 5-7). By screening
photocatalysts, we found that Rh-6G was the best photocatalyst
for this cascade cyclization process (Table 1, entries 1, 8-10).
The control experiment showed that the reaction could not
proceed in the absence of a photocatalyst and visible light (Table
1, entries 11-12). Gratifyingly, a 1.07 g (6.0 mmol) scale reaction
of 2-isocyanobiphenyl 1a was successfully performed with
bromobenzene 2a, providing the desired product 3aa in 62%
yield (Table 1, entry 13). In these reaction, biphenyls were
always formed in 5-15% yields.
Table 2
Scope of 2-isocyanobiphenyls 1 a
Entry
1
Substrates 1
Products 3
Yield b (%)
60
Table 1
Optimization of the reaction conditions a
2
3
68
71
Entry Variation from the "standard
reaction conditions"
Yield b (%)
1
2
3
none
79
57
32
MeCN as solvent
DMF as solvent

3
ACCEPTED MANUSCRIPT
4
5
6
7
64
2
49
56
67
3
51
4
52
58
66
58
5
6
7
8
9
63
77
3ai+3aj, (ratio 1:1.7)
N
F
a Reaction conditions: 1 (0.3 mmol), 2a (0.35mmol), Rh-6G (10 mol%),
DMSO (2.0 mL), DIPEA (0.75 mmol), in Ar atmosphere, room temperature,
5 W blue LED light for 20 h. b Isolated yields.
3ga
Br
The substrate scope was further investigated by reacting 2-
isocyanobiphenyl 1a with different aryl bromides 2. It is noted
that the broad availability of substituted aryl bromides 2 rendered
us access to various substituted 6-aryl substituted
phenanthridines. Notably, aryl bromides with electron-rich
substituents (like Me and MeO) on the aromatic rings could
proceed smoothly. The substituents at the ortho-, meta-, or para-
position have no distinct influence on the reaction. For example,
substrates 2c-2e with a Me group were transformed into products
3ca, 3da and 3ea in 49%, 56% and 52% yields, respectively
(Table 3, entries 2-4). Electron-deficient aryl bromides were
demonstrated to be well-tolerated under our standard conditions
(Table 3, entries 5-6). In addition, aryl bromide with a naphthyl
group also participated in this cyclization, affording the product 3ha
in 73 % yield (Table 3, entry 7). Heteroaromatic molecules
bearing heteroaryl-heteroaryl bonds are an important class of
building blocks found in a variety of areas. The visible-light-
induced cyclization process allowed the synthesis of 6-heteroaryl
substituted phenanthridines 3ia-3ka in moderate to good yields
(Table 3, entries 8-10).
73
70
2h
8
9
61
54
10
Table 3
Scope of aryl bromides 2 a
a Reaction conditions: 1a (0.3 mmol), 2 (0.35 mmol), Rh-6G (10 mol%),
DMSO (2.0 mL), DIPEA (0.75 mmol), in Ar atmosphere, room temperature,
5 W blue LED light for 20 h. b Isolated yields.
On the basis of these observations and previous studies,9-12
a
Entry
1
Substrates 2
Products 3
Yield b (%)
plausible mechanism was proposed as shown in Scheme 2. Under
the visible-light irradiation, Rh-6G was converted to the excited
[Rh-6G]*. A single electron transfer between [Rh-6G]* and
DIPEA afforded a radical anion/radical cation pair: [Rh-6G•−]
and [DIPEA•+]. Continuous irradiation of the radical anion [Rh-
6G•−] with blue light triggers a single electron transfer from the
excited [Rh-6G•−]* to bromobenzene 2a producing the transient
[Ph-Br•−] radical anion and regenerating Rh-6G completing the
50

4
Tetrahedron
catalytic cycle. Thereafter, [Ph-Br•−] radical anion undergoes
resulting residue was purified by silica gel column
ACCEPTED MANUSCRIPT
fragmentation to release a phenyl radical (Ph•), which reacts with
2-isocyanobiphenyl 1a to form the imidoyl radical A.
Subsequently, the intermediate A cyclizes to generate the
cyclohexadienyl radical B. Oxidation of radical B affords species
C. Then the desired phenanthridine 3aa is delivered after
deprotonation.
chromatography (hexane/ethyl acetate) to afford the substituted
phenanthridines 3.
6-Phenylphenanthridine (3aa).5b Yield: 79%, 60.5 mg; H
1
NMR (400 MHz, CDCl3) δ: 8.70 (d, J = 8.4 Hz, 1H), 8.63 (d, J =
8.0 Hz, 1H), 8.30-8.27 (m, 1H), 8.13 (d, J = 8.0 Hz, 1H), 7.89-
7.84 (m, 1H), 7.81-7.68 (m, 4H), 7.64-7.52 (m, 4H); 13C NMR
(100 MHz, CDCl3) δ: 161.1, 143.7, 139.8, 133.3, 130.5, 130.4,
129.6, 128.9, 128.7, 128.6, 128.3, 127.0, 126.7, 125.0, 123.2,
122.0, 121.6; LRMS (EI 70 ev) m/z (%): 255 (M+, 100); HRMS
m/z (ESI) calcd for C19H14N (M+H)+ 256.1126, found 256.1123.
2-Methyl-6-phenylphenanthridine (3ab).4e Yield: 60%, 48.5
mg; 1H NMR (400 MHz, CDCl3) δ: 8.66 (d, J = 8.0 Hz, 1H), 8.34
(s, 1H), 8.11, (d, J = 8.0 Hz, 1H), 8.04 (d, J = 8.4 Hz, 1H), 7.79-
7.75 (m, 1H), 7.70-7.67 (m, 2H), 7.53-7.44 (m, 5H), 2.49 (s, 3H);
13C NMR (100 MHz, CDCl3) δ: 160.7, 142.1, 139.6, 136.4,
133.1, 130.5, 130.1, 129.8, 129.5, 128.7, 128.4, 128.3, 126.8,
125.2, 123.2, 122.1, 121.2, 21.6; LRMS (EI 70 ev) m/z (%): 269
(M+, 100); HRMS m/z (ESI) calcd for C20H16N (M+H)+
270.1283, found 270.1285.
+
SET
H
H
N
Ph
N
Ph
DIPEA
[DIPEA]
[Rh-6G]
B
C
- H+
[Rh-6G]*
SET
3aa
*
Rh-6G
Ph
Rh-6G
2a
Br
C
N
Ph
1a
A
Scheme 2 Plausible mechanism for synthesis of 3aa
2-Chloro-6-phenylphenanthridine (3ac).4f Yield: 68%, 59.1
mg; 1H NMR (400 MHz, CDCl3) δ: 8.63 (d, J = 8.4 Hz, 1H), 8.56
(d, J = 3.6 Hz, 1H), 8.15 (d, J = 8.4 Hz, 1H), 8.08 (d, J = 8.4 Hz,
1H), 7.90-7.87 (m, 1H), 7.71-7.61 (m, 4H), 7.57-7.50 (m, 3H);
13C NMR (100 MHz, CDCl3) δ: 161.2, 142.0, 139.3, 133.1,
132.4, 131.7, 131.2, 129.8, 129.4, 129.1, 129.0, 128.6, 127.9,
125.3, 124.8, 122.4, 122.0; LRMS (EI 70 ev) m/z (%): 289 (M+,
100); HRMS m/z (ESI) calcd for C19H13ClN (M+H)+ 290.0737,
found 290.0742.
2,4-Dimethyl-6-phenylphenanthridine (3ad).4f Yield: 71%,
60.4 mg; 1H NMR (400 MHz, CDCl3) δ: 8.67 (d, J = 8.4 Hz, 1H),
8.22 (s, 1H), 8.13 (dd, J = 8.0 Hz, J = 1.2 Hz, 1H), 7.79-7.75 (m,
3H), 7.56-7.46 (m, 4H), 7.41 (s, 1H); 2.81 (s, 3H), 2.73 (s, 3H);
13C NMR (100 MHz, CDCl3) δ: 158.6, 140.7, 140.0, 137.2,
136.1, 133.5, 131.2, 130.0, 129.9, 128.4, 128.3, 128.2, 126.5,
124.7, 123.4, 122.2, 119.1, 22.3, 18.4; LRMS (EI 70 ev) m/z (%):
283 (M+, 100); HRMS m/z (ESI) calcd for C21H18N (M+H)+
284.1439, found 284.1437.
3. Conclusion
In conclusion, we have developed a novel metal-free approach
to 6-aryl substituted phenanthridines that involves the
functionalization of C(sp2)-Br and C(sp2)-H bonds. The mild
reaction conditions are compatible with many functional groups
and the scope of 2-isocyanobiphenyls and aryl bromides is broad
providing various 6-aryl substituted phenanthridines with good
yields. Simple and commercially available Rh-6G is employed as
the photoredox catalysts. All of these features as well as its
metal-free conditions make this method highly efficient and
practical. Further investigations of the mechanism of the reaction
and its application are ongoing in our laboratory.
4. Experimental section
4.1 General materials and methods
5-Phenyldibenzo[b,h][1,5]naphthyridine (3ae).4f Yield: 64%,
58.8 mg; 1H NMR (400 MHz, CDCl3) δ: 9.49 (d, J = 7.6 Hz, 1H),
8.98 (s, 1H), 8.39 (d, J = 8.8 Hz, 1H), 8.12 (dd, J = 3.2 Hz, J =
2.0 Hz, 2H), 7.99-7.96 (m, 1H), 7.87-7.74 (m, 4H), 7.64-7.52 (m,
4H); 13C NMR (100 MHz, CDCl3) δ: 163.1, 148.2, 143.0, 139.4,
136.5, 136.1, 134.2, 131.4, 130.3, 129.8, 129.7, 129.7, 129.3,
128.8, 128.7, 128.6, 128.5, 127.4, 126.5, 124.6; LRMS (EI 70 ev)
m/z (%): 306 (M+, 100); HRMS m/z (ESI) calcd for C22H15N2
(M+H)+ 307.1235, found 307.1229.
8-Methoxy-6-phenylphenanthridine (3af).4e Yield: 67%,
57.4 mg; 1H NMR (400 MHz, CDCl3) δ: 8.59 (d, J = 8.4 Hz, 1H),
8.51-8.47 (m, 1H), 8.17 (dd, J = 7.6 Hz, J = 1.2 Hz, 1H), 7.74-
7.67 (m, 2H), 7.63-7.58 (m, 2H), 7.55-7.48 (m, 3H), 7.44-7.40
(m, 2H), 3.87 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 159.7,
158.3, 143.1, 139.2, 130.3, 130.0, 129.3, 128.4, 128.0, 127.8,
127.1, 124.1, 121.5, 121.1, 116.1, 114.5, 110.0, 56.1; LRMS (EI
70 ev) m/z (%): 285 (M+, 100); HRMS m/z (ESI) calcd for
C20H16NO (M+H)+ 286.1232, found 286.1231.
Reagents were obtained commercially and used as received.
Solvents were purified and dried by standard methods. Substrates
1 were prepared according the literature methods.4g 1H NMR
spectra were recorded on 400 MHz in CDCl3, and 13C NMR
spectra were recorded on 100 MHz in CDCl3 using
tetramethylsilane (TMS) as an internal standard. Chemical shift
values (δ) are given in ppm. Coupling constants (J) were
measured in Hz. GC-MS analyses were performed on a
SHIMADZU QP2010. High Resolution mass spectrometer
(HRMS) spectra were recorded on a Bruker micrOTOF-Q II
analyzer. 200-300 mesh silica gel was used for column
chromatography.
4.2 General procedure for synthesis of 6-aryl (heteroaryl)
substituted phenanthridines 3
To a Schlenk tube were added 2-isocyanobiphenyls 1 (0.3
mmol), aryl bromides 2 (0.35 mmol), DMSO (2.0 mL), Rh-6G
(0.03 mmol), DIPEA (0.75 mmol), Then the tube was charged
with argon, and was stirred at room temperature with the
irradiation of a 5 W blue LED for about 20-24 h. After the
reaction was finished, the reaction mixture was diluted in 40 mL
ethyl acetate, washed with a saturated solution of brine (8 mL), a
solution of 1 mol/L HCl (10 mL), a saturated solution of brine (8
mL), saturated NaHCO3 (10 mL), a saturated solution of brine (8
mL), dried (Na2SO4) and concentrated in vacuum, and the
8-Chloro-6-phenylphenanthridine (3ag).4e Yield: 51%, 44.3
mg; 1H NMR (400 MHz, CDCl3) δ: 8.61 (d, J = 8.0 Hz, 1H), 8.53
(d, J = 7.6 Hz, 1H), 8.19 (d, J = 8.0 Hz, 1H), 8.00 (d, J = 2.8 Hz,
1H), 7.79-7.74 (m, 2H), 7.70-7.63 (m, 3H), 7.58-7.50 (m, 3H);
13C NMR (100 MHz, CDCl3) δ: 159.3, 143.1, 139.2, 133.0,
131.6, 131.2, 130.2, 129.5, 129.2, 128.9, 128.4, 127.7, 127.0,

5
126.1, 124.3, 123.0, 121.8; LRMS (EI 70 ev) m/z (%): 289 (M+,
90); HRMS m/z (ESI) calcd for C19H13ClN (M+H)+ 290.0737,
found 290.0744.
1H), 7.62-7.58 (m, 1H), 7.55 (s, 1H), 7.49-7.41 (m, 2H), 7.31
ACCEPTED MANUSCRIPT
(d, J = 6.8 Hz, 1H), 2.39 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
162.1, 143.3, 139.5, 138.1, 133.3, 130.6, 130.1, 129.9, 129.3,
129.0, 128.7, 128.1, 127.1, 126.8, 126.4, 125.3, 123.6, 121.9,
121.7, 21.7; LRMS (EI 70 ev) m/z (%): 269 (M+, 100); HRMS
m/z (ESI) calcd for C20H16N (M+H)+ 270.1283, found 270.1277.
5-Phenylbenzo[i]phenanthridine (3ah).4f Yield: 58%, 53.1
mg; 1H NMR (400 MHz, CDCl3) δ: 8.67-8.63 (m, 2H), 8.31 (d, J
= 8.4 Hz, 1H), 8.20 (d, J = 8.8 Hz, 1H), 7.94 (d, J = 8.0 Hz, 1H),
7.80-7.76 (m, 2H), 7.72-7.69 (m, 1H), 7.62-7.59 (m, 2H), 7.51-
7.46 (m, 4H), 7.23-7.19 (m, 1H); 13C NMR (100 MHz, CDCl3) δ:
159.7, 144.2, 143.6, 134.4, 133.2, 132.6, 130.4, 129.7, 129.3,
129.1, 129.0, 128.6, 128.5, 128.2, 127.0, 126.5, 126.1, 123.7,
122.4, 121.5, 120.2; LRMS (EI 70 ev) m/z (%): 305 (M+, 100);
HRMS m/z (ESI) calcd for C23H16N (M+H)+ 306.1283, found
306.1279
9-Chloro-6-phenylphenanthridine (3ai).4f Yield: 23%, 20.0
mg; 1H NMR (400 MHz, CDCl3) δ: 8.61 (s, 1H), 8.52 (d, J = 8.4
Hz, 1H), 8.22 (d, J = 8.0 Hz, 1H), 8.04 (d, J = 8.8 Hz, 1H), 7.80
(t, J = 7.6 Hz, 1H), 7.70-7.67 (m, 3H), 7.55-7.50 (m, 4H); 13C
NMR (100 MHz, CDCl3) δ: 160.6, 144.0, 139.4, 137.1, 134.5,
130.6, 130.1, 129.4, 129.0, 128.8, 128.4, 127.6, 127.2, 123.5,
122.7, 122.0, 121.8; LRMS (EI 70 ev) m/z (%): 289 (M+, 100);
HRMS m/z (ESI) calcd for C19H13ClN (M+H)+ 290.0737, found
290.0739.
7-Chloro-6-phenylphenanthridine (3aj).4f Yield: 40%, 34.8
mg; 1H NMR (400 MHz, CDCl3) δ: 8.67 (d, J = 8.0 Hz, 1H), 8.58
(dd, J = 8.4 Hz, J = 1.2 Hz, 1H), 8.24 (d, J = 8.0 Hz, 1H), 8.07
(dd, J = 8.0 Hz, J = 1.2 Hz, 1H), 7.82-7.78 (m, 1H), 7.70-7.64
(m, 4H), 7.59-7.54 (m, 3H); 13C NMR (100 MHz, CDCl3) δ:
160.9, 143.6, 139.0, 136.1, 133.7, 131.4, 130.2, 129.9, 129.1,
128.6, 128.3, 127.4, 127.1, 125.6, 123.4, 122.5, 122.0; LRMS (EI
70 ev) m/z (%): 289 (M+, 90); HRMS m/z (ESI) calcd for
C19H13ClN (M+H)+ 290.0737, found 290.0740.
Ethyl 4-methyl-1-phenylisoquinoline-3-carboxylate (3ak).4c
Yield: 77%, 67.3 mg; 1H NMR (400 MHz, CDCl3) δ: 8.18 (d, J =
8.4 Hz, 1H), 8.12 (d, J = 8.4 Hz, 1H), 7.81-7.67 (m, 1H), 7.70-
7.67 (m, 2H), 7.60-7.57 (m, 1H), 7.53-7.46 (m, 3H), 4.52 (q, J =
7.2 Hz, 2H), 2.83 (s, 3H), 1.44 (t, J = 7.2 Hz, 3H); 13C NMR (100
MHz, CDCl3) δ: 167.9, 158.8, 142.0, 139.1, 136.6, 130.4, 130.1,
128.6, 128.3, 128.1, 127.8, 126.9, 124.3, 61.4, 14.3, 14.2; LRMS
(EI 70 ev) m/z (%): 291 (M+, 100); HRMS m/z (ESI) calcd for
C19H18NO2 (M+H)+ 292.1338, found 292.1336.
6-(o-Tolyl)phenanthridine (3ea).4e Yield: 52%, 42.0 mg; H
1
NMR (400 MHz, CDCl3) δ: 8.70 (d, J = 8.0 Hz, 1H), 8.63 (dd, J
= 8.4 Hz, J = 1.2 Hz, 1H), 8.22 (d, J = 7.6 Hz, 1H), 7.85-7.81 (m,
1H), 7.77-7.72 (m, 1H), 7.69-7.64 (m, 2H), 7.60-7.55 (m, 1H),
7.41-7.34 (m, 4H), 2.31 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
162.3, 143.7, 138.9, 136.6, 133.1, 130.8, 130.2, 129.8, 129.2,
128.7, 128.3, 128.0, 127.2, 127.1, 126.3, 125.5, 123.8, 122.3,
122.0, 21.1; LRMS (EI 70 ev) m/z (%): 269 (M+, 100); HRMS
m/z (ESI) calcd for C20H16N (M+H)+ 270.1283, found 270.1281.
6-(4-Chlorophenyl)phenanthridine (3fa).5b Yield: 58%, 50.4
mg; 1H NMR (400 MHz, CDCl3) δ: 8.71 (d, J = 8.0 Hz, 1H), 8.60
(d, J = 8.4 Hz, 1H), 8.21 (d, J = 8.0 Hz, 1H), 8.09 (d, J = 7.6 Hz,
1H), 7.88-7.81 (m, 1H), 7.75-7.68 (m, 4H), 7.62 (dd, J = 8.0 Hz,
J = 1.2 Hz, 1H), 7.49 (d, J = 8.0 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ: 161.2, 143.6, 138.1, 135.2, 133.4, 131.1, 130.5, 130.1,
129.2, 128.4, 128.0, 127.3, 126.6, 125.1, 123.4, 122.2, 122.0;
LRMS (EI 70 ev) m/z (%): 289 (M+, 100); HRMS m/z (ESI)
calcd for C19H13ClN (M+H)+ 290.0737, found 290.0740.
6-(4-Fluorophenyl)phenanthridine (3ga).4e Yield: 66%, 54.1
mg; H NMR (400 MHz, CDCl3) δ: 8.73 (d, J = 8.4 Hz, 1H),
1
8.71-8.67 (m, 1H), 8.26 (dd, J = 8.0 Hz, J = 1.2 Hz, 1H), 8.10 (d,
J = 7.2 Hz, 1H), 7.91-7.86 (m, 1H), 7.82-7.68 (m, 4H), 7.64-7.60
(m, 1H), 7.37-7.30 (m, 2H); 13C NMR (100 MHz, CDCl3) δ:
164.3 (d, J = 245.7 Hz), 160.1, 143.3, 135.2 (d, J = 3.4 Hz),
133.3, 131.4 (d, J = 8.2 Hz), 130.6, 130.0, 128.8, 128.5, 127.2,
127.0, 125.4, 123.5, 122.3, 122.0, 116.2 (d, J = 22.3 Hz); LRMS
(EI 70 ev) m/z (%): 273 (M+, 100); HRMS m/z (ESI) calcd for
C19H13FN (M+H)+ 274.1032, found 274.1031.
6-(Naphthalen-3-yl)phenanthridine (3ha).4b Yield: 73%,
66.8 mg; 1H NMR (400 MHz, CDCl3) δ: 8.72 (d, J = 8.0 Hz, 1H),
8.64 (d, J = 8.0 Hz, 1H), 8.28 (d, J = 8.0 Hz, 1H), 8.23 (s, 1H),
8.16 (d, J = 8.4 Hz, 1H), 8.08 (d, J = 8.8 Hz, 1H), 7.97-7.94 (m,
2H), 7.87-7.84 (m, 2H), 7.82 (d, J = 7.6 Hz, 1H), 7.72 (t, J = 6.2
Hz, 1H), 7.63-7.54 (m, 3H); 13C NMR (100 MHz, CDCl3) δ:
161.1, 143.8, 137.2, 133.5, 133.3, 133.2, 130.7, 130.4, 129.2,
128.9, 128.8, 128.4, 128.0, 127.7, 127.3, 127.1, 126.9, 126.6,
126.4, 125.3, 123.7, 122.3, 122.0; LRMS (EI 70 ev) m/z (%): 305
(M+, 100); HRMS m/z (ESI) calcd for C23H16N (M+H)+
306.1283, found 306.1280.
6-(Pyridin-3-yl)phenanthridine (3ia).13 Yield: 70%, 53.8 mg;
1H NMR (400 MHz, CDCl3) δ: 9.02 (d, J = 1.6 Hz, 1H), 8.81 (dd,
J = 5.6 Hz, J = 1.6 Hz, 1H), 8.74 (d, J = 8.0 Hz, 1H), 8.65 (d, J =
8.0 Hz, 1H), 8.26 (dd, J = 8.0 Hz, J = 1.6 Hz, 1H), 8.13-8.10 (m,
1H), 8.07 (d, J = 8.0 Hz, 1H), 7.93-7.90 (m, 1H), 7.82-7.78 (m,
1H), 7.75-7.72 (m, 1H), 7.68-7.64 (m, 1H), 7.55 (dd, J = 6.8 Hz,
J = 4.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ: 157.7, 150.5,
149.7, 143.6, 137.1, 135.4, 133.3, 130.6, 130.1, 129.0, 127.9,
127.3, 127.1, 124.8, 123.5, 123.2, 122.4, 121.9; LRMS (EI 70 ev)
m/z (%): 256 (M+, 100); HRMS m/z (ESI) calcd for C18H13N2
(M+H)+ 257.1079, found 257.1084.
6-(4-Methoxyphenyl)phenanthridine (3ba).4e Yield: 50%,
42.8 mg; 1H NMR (400 MHz, CDCl3) δ: 8.70 (d, J = 8.4 Hz, 1H),
8.59 (d, J = 7.2 Hz, 1H), 8.27-8.22 (m, 1H), 8.13 (d, J = 8.0 Hz,
1H), 7.85-7.80 (m, 1H), 7.75-7.56 (m, 5H), 7.08 (d, J = 8.8 Hz,
2H), 3.89 (s, 3H); 13C NMR (100 MHz, CDCl3) δ: 160.3, 160.0,
143.1, 133.4, 132.2, 131.0, 130.4, 130.1, 129.0, 128.6, 127.1,
126.6, 125.4, 123.3, 122.1, 121.8, 113.6, 55.2; LRMS (EI 70 ev)
m/z (%): 285 (M+, 100); HRMS m/z (ESI) calcd for C20H16NO
(M+H)+ 286.1232, found 286.1226.
1
6-(p-Tolyl)phenanthridine (3ca).4e Yield: 49%, 39.6 mg; H
NMR (400 MHz, CDCl3) δ: 8.67 (d, J = 8.4 Hz, 1H), 8.59-8.57
(m, 1H), 8.23 (dd, J = 8.0 Hz, J = 0.8 Hz, 1H), 8.12 (dd, J = 8.4
Hz, J = 0.8 Hz, 1H), 7.82-7.80 (m, 1H), 7.76-7.59 (m, 5H), 7.39-
7.35 (m, 2H), 2.46 (s, 3H); 13C NMR (100 MHz, CDCl3) δ:
161.4, 143.4, 138.1, 136.5, 133.0, 130.4, 130.1, 129.6, 129.1,
129.0, 128.9, 128.8, 127.2, 126.5, 123.4, 122.1, 121.6, 21.4;
LRMS (EI 70 ev) m/z (%): 269 (M+, 100); HRMS m/z (ESI)
calcd for C20H16N (M+H)+ 270.1283, found 270.1287.
6-(Thiophen-2-yl)phenanthridine (3ja).13 Yield: 61%, 47.8
mg; H NMR (400 MHz, CDCl3) δ: 8.70 (d, J = 8.4 Hz, 1H),
1
8.60-8.55 (m, 2H), 8.19 (d, J = 8.0 Hz, 1H), 7.86-7.81 (m, 1H),
7.74-7.63 (m, 4H), 7.55 (d, J = 4.8 Hz, 1H), 7.25-7.21 (m, 1H);
13C NMR (100 MHz, CDCl3) δ: 154.6, 143.4, 142.3, 133.2,
130.7, 130.2, 129.1, 128.8, 128.0, 127.8, 127.4, 127.1, 126.8,
124.7, 123.5, 122.2, 121.8; LRMS (EI 70 ev) m/z (%): 261 (M+,
6-(m-Tolyl)phenanthridine (3da).4e Yield: 56%, 45.2 mg; 1H
NMR (400 MHz, CDCl3) δ: 8.71 (d, J = 8.4 Hz, 1H), 8.58 (d, J =
8.0 Hz, 1H), 8.21 (dd, J = 7.6 Hz, J = 1.2 Hz, 1H), 8.09 (d, J =
8.4 Hz, 1H), 7.86-7.82 (m, 1H), 7.77-7.73 (m, 1H), 7.70-7.65 (m,

6
Tetrahedron
ACCEPTED MANUSCRIPT
100); HRMS m/z (ESI) calcd for C17H12NS (M+H)+ 262.0690,
Zhang, P.; Mao, Z.-W.; Zhou, L. Green Chem. 2014, 16, 2418-
2421; (f) Gu, L.; Jin, C.; Liu, J.; Ding, H.; Fan, B. Chem.
found 262.0694.
Commun. 2014, 50, 4643-4645; (g) Tobisu, M.; Koh, K.;
Furukawa, T.; Chatani, N. Angew. Chem. Int. Ed. 2012, 51,
11363-11366; (h) Shou, W.-G.; Yang, Y.-Y.; Wang, Y.-G. J.
Org.Chem. 2006, 71, 9241-9243.
(a) Zhang, B.; Studer, A. Chem. Soc. Rev. 2015, 44, 3505-3521;
(b) Singh, K.; Singh, A. K.; Singh, D.; Singh, R.; Sharma, S. Catal.
Sci. Technol. 2016, 6, 3723-3726; (c) Lei, J.; Huang, J.; Zhu, Q.
Org. Biomol. Chem. 2016, 14, 2593-2602; (d) Liu, J.; Fan, C.;
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Yang, H.; Cheng, J. Chem. Commun. 2014, 50, 9179-9181.
6-(Furan-2-yl)phenanthridine (3ka).13 Yield: 54%, 39.7 mg;
1H NMR (400 MHz, CDCl3) δ: 8.80 (d, J = 8.0 Hz, 1H), 8.65 (d,
J = 8.0 Hz, 1H), 8.54 (d, J = 8.4 Hz, 1H), 8.31 (d, J = 7.6 Hz,
1H), 7.92-7.88 (m, 1H), 7.83-7.72 (m, 3H), 7.63-7.58 (m, 1H),
7.35 (d, J = 4.0 Hz, 1H), 6.71-6.69 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ: 149.4,144.5, 141.2, 138.1, 133.8, 131.0, 129.8, 129.1,
128.2, 127.8, 127.2, 124.0, 123.8, 122.3, 122.0, 112.0, 108.4;
LRMS (EI 70 ev) m/z (%): 245 (M+, 100); HRMS m/z (ESI)
calcd for C17H12NO (M+H)+ 246.0919, found 246.0921.
5.
6. For selected reviews on visible-light photoredox catalysis, see: (a)
Liu, Q.; Wu, L.-Z. Natl. Sci. Rev. 2017, 4, 359-380; (b) Chen, J.-
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Acknowledgement
We are grateful for the financial support from the National
Natural Science Foundation of China (21502077), the National
College Students Innovation Project (201500393002), the
Applied Basic Research Programs of Yunnan Science and
Technology Department (2015FD088), the General Projects of
Yunnan Education Department (2015Y396), the Research
Foundation for Introduced Talents (YJL14010), the Scientific
Research Funds (XJL14013) of Kunming University, the Project
of Applied Talents Cultivation Innovation in Kunming
University: the Construction of Innovation Practice Base of
Chemistry and Chemical Engineering Students (HHCX201501,
HXHG1706), and the Innovation Team Project of Kunming
University (2015CXTD03 ).
7. For recent reviews: For recent selected examples for visible-light
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Supporting Information Available: Characterization data of 3
including the 1H and 13C NMR data.
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