Palladium-catalyzed three-component cyclization of 2-bromocyclohex-1-enecarboxylic acids with carbon monoxide and arylhydrazines leading to 2-anilinohydroisoindoline-1,3-diones

Article abstract of DOI:10.1002/aoc.3274

2-Bromocyclohex-1-enecarboxylic acids are carbonylatively cyclized with arylhydrazines or their hydrochlorides in tetrahydrofuran at 120 °C under carbon monoxide pressure in the presence of a catalytic amount of PdCl₂ and 1,3-bis(diphenylphosph

Full text of DOI:10.1002/aoc.3274

Full Paper
Received: 17 October 2014
Revised: 3 December 2014
Accepted: 13 December 2014
Published online in Wiley Online Library: 3 February 2015
(wileyonlinelibrary.com) DOI 10.1002/aoc.3274
Palladium-catalyzed three-component
cyclization of 2-bromocyclohex-1-enecarboxylic
acids with carbon monoxide and arylhydrazines
leading to 2-anilinohydroisoindoline-1,3-diones
Il Chul Yoon and Chan Sik Cho*
2-Bromocyclohex-1-enecarboxylic acids are carbonylatively cyclized with arylhydrazines or their hydrochlorides in tetrahydrofu-
ran at 120 °C under carbon monoxide pressure in the presence of a catalytic amount of PdCl2 and 1,3-bis(diphenylphosphino)
propane along with Et3N to give 2-anilinohydroisoindoline-1,3-diones. Copyright © 2015 John Wiley & Sons, Ltd.
Keywords: 2-bromocyclohex-1-enecarboxylic acids; carbonylation and cyclization; arylhydrazines; 2-anilinohydroisoindoline-1,3-diones;
palladium catalyst
phenylhydrazine (2a), leading to 2-(phenylamino)-4,5,6,7-tetrahydro-
2H-isoindole-1,3-dione (3a) under various conditions such as
Introduction
It is known that 2-anilinoisoindoline-1,3-diones and their hydro
analogues exhibit biological activities such as anticancer[1] and
herbicidal activities (Scheme 1).[2] 2-(Phenylamino)isoindoline-1,
3-dione is also used as a precursor for the preparation of anti-
inflammatory products.[3] Such scaffolds are generally synthesized
by the reaction of the corresponding phthalic and maleic
anhydrides with arylhydrazines.[4,5] As part of our continuing
studies directed towards transition metal-catalyzed cyclization
reactions of β-bromo-α,β-unsaturated aldehydes and their
derivatives, we have identified several new methods for the
synthesis of various carbonyl group-containing heterocycles via
palladium-catalyzed carbonylative cyclization (carbonylation
followed by cyclization) under carbon monoxide pressure.[6–19]
β-Bromo-α,β-unsaturated aldehydes and their derivatives are
readily prepared from α-methylene group-containing ketones by
bromination under Vilsmeier–Haack conditions[20,21] and subse-
quent transformation, and the products can serve as valuable
building blocks for the construction of various cyclic
compounds.[22–38] Among such carbonlative cyclization reactions,
we recently have shown that β-bromo-α,β-unsaturated carboxylic
acids can be carbonylatively cyclized with 2,2-dimethylhydrazine
under carbon monoxide pressure in the presence of a palladium
catalyst to give 1-(dimethylamino)-1H-pyrrole-2,5-diones.[39] The
present work arose during the course of the application of this
protocol to the reaction with arylhydrazines. This report describes
a facile method for the synthesis of 2-anilinohydroisoindoline-1,
3-diones by palladium-catalyzed carbonylative cyclization of
2-bromocyclohex-1-enecarboxylic acids with arylhydrazines or
arylhydrazine hydrochlorides under carbon monoxide pressure.
molar ratio of 2a to 1a, ligand, solvent, reaction temperature
and time, and CO pressure. Treatment of 1a with an equimolar
amount of 2a under CO (10 atm) in THF at 120 °C for 3 h in
the presence of a catalytic amount of PdCl2 and 1,3-bis
(diphenylphosphino)propane (dppp) along with Et3N affords 3a
in 23% isolated yield with several unidentifiable products (entry 1).
The carbonylative endo-cyclized product 4 is not produced at all
regardless of an effort to isolate such a scaffold from the
reaction mixture. The yield of 3a is considerably affected by the
molar ratio of 2a to 1a. A ratio of [2a]/[1a] = 3 is desirable from
an atom economy point of view, not shown in Table 1, since a
higher molar ratio ([2a]/[1a] = 4–5) results in rather lower yield
of 3a (47–51% yields; entries 1–3). Prolonging the reaction time
gives no improvement in the yield of 3a (entry 4). No significant
change of the yield of 3a is observed with dilution of the reaction
mixture (entry 5). Either lower reaction temperature or CO
pressure results in a decreased yield of 3a (entries 6 and 7). The
reaction also proceeds in the presence of various other phospho-
rus ligands, such as PPh3, 1,2-bis(diphenylphosphino)ethane
(dppe), 1,4-bis(diphenylphosphino)butane (dppb) or 1,1′-bis
(diphenylphosphino)ferrocene (dppf), under the employed
conditions, but the yields of 3a are generally lower than that
obtained in the presence of dppp (entries 8–11). As a result, after
further tuning with several solvents and catalyst amount (entries
12–15), the best result in terms of both product yield and
complete conversion of 1a is obtained using the standard set of
reaction conditions shown in entry 3 of Table 1.
*
Correspondence to: Chan Sik Cho, Department of Applied Chemistry, Kyungpook
National University, Daegu 702–701, South Korea. E-mail: cscho@knu.ac.kr
Results and Discussion
Table 1 gives several results for the attempted carbonylative
cyclization of 2-bromocyclohex-1-enecarboxylic acid (1a) with
Department of Applied Chemistry, Kyungpook National University, Daegu
702-701, South Korea
Appl. Organometal. Chem. 2015, 29, 226–230
Copyright © 2015 John Wiley & Sons, Ltd.

Palladium-catalyzed three-component cyclization
of 2b–d. With meta-methyl-substituted 2c, the product yield is
generally lower than that when ortho-methyl-substituted 2b and
para-methyl-substituted 2d are used. With 2e having an electron-
donating methoxy substituent, the product yield is lower than
when 2f having an electron-withdrawing Cl substituent is used
under condition B. 2-Bromocyclohex-1-enecarboxylic acids having
methyl and phenyl substituents on the cyclohexane ring, 1b and
1c, were also carbonylatively cyclized with 2a under the employed
condition A to give 5-methyl- and 5-phenyl-2-(phenylamino)-
4,5,6,7-tetrahydro-1H-isoindole-1,3(2H)-diones (3 g and 3 h) in 46
and 31% yields, respectively. From the reaction of 1b with 2a, 3 g
is formed in similar yields under both conditions A and B. To
test for the effect of the position of bromide and carboxy
groups on 2-bromocyclohex-1-enecarboxylic acids, 1d and 1e
were employed. The carbonylative cyclization readily takes
place with both 1d and 1e irrespective of their position. However,
2-(4-tolylamino)-1H-benzo[e]isoindole-1,3(2H)-dione (3i) is produced
by dehydrogenation of the initially formed 2-(4-tolylamino)-4,
5-dihydro-1H-benzo[e]isoindole-1,3(2H)-dione under the employed
conditions. The mass spectrum of 3i shows peaks at m/z = 302
(M+, 100% intensity) and 303 (M+ + 1, 23% intensity). Similar
dehydrogenation was observed in our recent work on the
coupling and cyclization of β-bromo-α,β-unsaturated amides with
formamide.[37]
Scheme 1. Biologically active compounds.
With the optimum reaction conditions in hand, various 2-
bromocyclohex-1-enecarboxylic acids 1 were subjected to reaction
with arylhydrazines (or arylhydrazine hydrochlorides) 2 to investi-
gate the scope of the reaction. Several representative results are
summarized in Table 2.[40] In view of the availability of the
arylhydrazine counterpart, it is desirable to use arylhydrazine
hydrochloride since most commercially available arylhydrazines
are sold as their hydrochloride salts. Similar treatment of 1a with
phenylhydrazine hydrochloride (condition B, 2a) for 20 h under
the employed conditions affords 3a in 46% isolated yield. Lower re-
action rate and yield are observed with arylhydrazine hydrochlo-
rides 2. 2-Bromocyclohex-1-enecarboxylic acid (1a) is readily
carbonylatively cyclized with an array of arylhydrazine hydrochlo-
rides (2b–f) to give the corresponding 2-anilinohydroisoindoline-
1,3-diones (3b–f) in the range 37–55% isolated yields and the
product yield varies with the position and electronic nature of the
substituent on 2. Judging from the reaction of 1a with 2b–d having
electron-donating methyl substituent, the product yield has
relevance to the position of the substituent on the aromatic ring
Product 3b was chosen for structural identification and
confirmed from its IR, mass, 1H NMR and 13C NMR spectra. The IR
spectrum exhibits a characteristic absorption at 1724 cmꢀ1
attributed to the carbonyl group of 3b. The high-resolution mass
spectrum displays a peak at m/z = 256.1209 (M+). The 1H NMR and
Table 1. Optimization of conditions for the reaction of 1a with 2aa
Entry
[2a]/[1a]
Ligand
Solvent
THF
Yield (%)
1
1
2
3
3
3
3
3
3
3
3
3
3
3
3
3
dppp
dppp
dppp
dppp
dppp
dppp
dppp
PPh3
23
53
57
52
50
45
49
45
15
41
47
31
13
2
2
THF
3
THF
4b
5c
6d
7e
8
THF
THF
THF
THF
THF
9
dppe
dppb
dppf
THF
10
11
12
13
14
15f
THF
THF
dppp
dppp
dppp
dppp
Dioxane
MeCN
DMF
THF
25
aReaction conditions: 1a (0.5 mmol), PdCl2 (0.025 mmol), ligand (bidentate ligands: 0.03 mmol; PPh3: 0.05 mmol), Et3N (2 mmol),
solvent (10 ml), CO (10 atm), 120 °C, 3 h, unless otherwise stated.
bFor 8 h.
cTHF (20 ml).
dAt 60 °C.
eUnder CO (5 atm).
fPdCl2 (0.01 mmol).
Appl. Organometal. Chem. 2015, 29, 226–230
Copyright © 2015 John Wiley & Sons, Ltd.
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I. C. Yoon and C. S. Cho
Table 2. Palladium-catalyzed synthesis of 2-(arylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-diones 3 from β-bromo-α,
β-unsaturated ketones 1 and arylhydrazines (or arylhydrazine hydrochlorides) 2a
1
2
Conditionb
Product
Yield (%)
R1
R2
R3
R4
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1a
1a
1a
1a
1a
1a
1a
1b
1b
1c
1d
1e
2a
2a
2b
2c
2d
2e
2f
A
B
B
B
B
B
B
A
B
A
B
B
3a
3a
3b
3c
57
46
46
37
48
41
55
46
44
31
40
43
H
H
H
H
H
H
H
H
3d
3e
3f
H
H
H
H
H
Me
Me
Ph
H
2a
2a
2a
2d
2d
3 g
3 g
3 h
3ic
3ic
H
H
H
Benzofused
Benzofused
H
H
aReaction conditions: 1 (0.5 mmol), 2 (1.5 mmol), PdCl2 (0.025 mmol), dppp (0.03 mmol), THF (10 ml), CO (10 atm), 120 °C.
bCondition A: arylhydrazine, Et3N (2 mmol), for 3 h; condition B: arylhydrazine hydrochloride, Et3N (3.5 mmol), for 20 h.
c2-(4-Methylphenylamino)-2H-benzo[e]isoindole-1,3-dione.
13C NMR spectra of 3b show characteristic signals with appropriate
chemical shifts detailed with the spectroscopic data in the
Experimental section.
As to the reaction pathway, although it is not yet fully
understood, this seems to proceed via an initial formation of
hydrazide 5 by the condensation between 1a and 2a (Scheme 2).
Oxidative addition of a carbon–bromide bond of 5 to palladium
(0) produces a vinyl intermediate 6, where carbon monoxide
coordination to palladium and then vinyl migration from palladium
to the carbon of carbon monoxide occur to give an acylpalladium(II)
intermediate (7). This is followed by cyclization due to extrusion of
HBr by Et3N to produce palladacycle 8, which can reductively
eliminate to afford 3a. Alternatively, it appears that 3a is also pro-
duced by the displacement of initially formed maleic anhydride 9
by phenylhydrazine 2a.[19] We confirmed in a separate experiment
that maleic anhydride 9 reacted with 2a in THF at 120 °C for 3 h to
give the product 3a in 70% yield.[4,5,41]
Conclusions
In summary, we have demonstrated that 2-bromocyclohex-1-
enecarboxylic acids, which are readily prepared from cyclohexanones
in two steps, can be carbonylatively cyclized with arylhydrazines
or their hydrochlorides to give 2-anilinohydroisoindoline-1,
3-diones in the presence of PdCl2 and dppp along with Et3N.
The present reaction provides a promising route for the synthesis
of valuable heterocycles from readily available ketones. Further
study of synthetic applications to heterocycles starting from
ketones is currently under way.
Experimental
1H NMR and 13C NMR (400 and 100 MHz) spectra were recorded
with a Bruker Avance Digital 400 spectrometer using tetra-
methylsilane as an internal standard. Melting points were deter-
mined with a Stanford Research Inc. MPA100 automated melting
point apparatus. High-resolution mass spectrometry (HRMS) was
performed with a Jeol JMS-700 spectrometer at the Korea Basic
Scheme 2. Proposed catalytic cycle.
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Copyright © 2015 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2015, 29, 226–230

Palladium-catalyzed three-component cyclization
Science Center, Daegu, Korea. The isolation of pure products was
carried out via thin-layer (silica gel 60 GF254, Merck) chromatogra-
phy. The starting 2-bromocyclohex-1-enecarboxylic acids were
prepared via two steps from the corresponding cyclohexanones
according to literature procedures.[20,21,40] Commercially available
organic and inorganic compounds were used without further
purification.
2-(4-Methyphenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3d)
Semisolid. IR (ATR): 1721 (C¼O) cmꢀ1. H NMR (400 MHz, CDCl3,
1
Typical Procedure for Palladium-Catalyzed Carbonylative
Cyclization of 2-Bromocyclohex-1-enecarboxylic Acids with
Arylhydrazines (or their Hydrochlorides)
δ, ppm): 1.78–1.81 (m, 4H, –(CH2)2–), 2.25 (s, 3H, CH3), 2.36–2.39
(m, 4H, allylic 2CH2), 5.89 (s, 1H, NH), 6.66–6.69 (m, 2H, H6),
7.02 (d, JHH = 8.0Hz, 2H, H7). 13C NMR (100MHz, CDCl3, δ,
ppm): 20.23 (C9), 20.76 (C2), 21.33 (C3), 114.32 (C6), 129.89
(C7), 131.62 (C8), 140.57 (C5), 143.92 (C4), 169.31 (C1), assign-
ments to C2, C3 and C9 are interchangeable, assignments to
C4 and C5 are interchangeable. HRMS (EI). Anal. Calcd for
C15H16N2O2 (M+): 256.1212. Found: 256.1209. Anal. Calcd for
C15H16N2O2 (%): C, 70.29; H, 6.29; N, 10.93. Found (%): C, 70.13; H,
6.22; N, 10.91.
To a 50 ml stainless steel autoclave were added 2-bromocyclohex-
1-enecarboxylic acid (1a; 0.103 g, 0.5 mmol), phenylhydrazine (2a;
0.162 g, 1.5mmol), PdCl2 (0.004 g, 0.025 mmol), dppp (0.012 g,
0.03 mmol), Et3N (0.202 g, 2.0mmol) and THF (10 ml). After the
system was flushed and then pressurized with CO to 10atm, the
reaction mixture was heated to react at 120 °C for 3 h. The reaction
mixture was filtered through a short silica gel column (ethyl acetate)
to eliminate inorganic salts. Removal of the solvent left a crude
mixture, which was separated by thin-layer chromatography
(silica gel, ethyl acetate–hexane= 1:2) to give 2-(phenylamino)-
4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3a; 0.069 g, 57%). Except
for known 3a,[39] all new products prepared using the procedure
outlined above were characterized spectroscopically as shown
below.
2-(4-Methoxyphenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3e)
Solid; m.p. 93–94 °C. IR (ATR): 1709 (C¼O) cmꢀ1. 1H NMR (400 MHz,
CDCl3, δ, ppm): 1.79–1.82 (m, 4H, –(CH2)2–), 2.39–2.42 (m, 4H, allylic
2CH2), 3.81 (s, 3H, CH3), 6.94–6.98 (m, 2H, H6), 7.20–7.24 (m, 2H, H7),
NH signal was not observed. 13C NMR (100 MHz, CDCl3, δ, ppm):
20.28 (C2), 21.48 (C3), 55.58 (C9), 114.46 (C6), 124.62 (C5), 127.68
(C7), 141.76 (C4), 158.88 (C8), 170.39 (C1). Anal. Calcd for
C15H16N2O3 (%): C, 66.16; H, 5.92; N, 10.29. Found (%): C, 65.97; H,
5.88; N, 10.27.
2-(2-Methyphenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3b)
Semisolid. IR (ATR): 1724 (C¼O) cmꢀ1. 1H NMR (400 MHz, CDCl3, δ,
ppm): 1.79–1.82 (m, 4H, –(CH2)2–), 2.30 (s, 3H, CH3), 2.37–2.40 (m,
4H, allylic 2CH2), 5.85 (s, 1H, NH), 6.52 (d, JHH = 7.8Hz, 1H, H10),
6.83–6.87 (m, 1H, H8), 7.05–7.09 (m, 2H, H7 and H9). 13C NMR
(100 MHz, CDCl3, δ, ppm): 17.10 (C11), 20.20 (C3), 21.27 (C2),
112.12 (C10), 121.69 (C6), 123.16 (C8), 127.09 (C9), 130.83 (C7),
140.56 (C4), 144.06 (C5), 169.21 (C1), assignments to C6–C8 are in-
terchangeable. HRMS (EI). Anal. Calcd for C15H16N2O2 (M+):
256.1212. Found: 256.1209. Anal. Calcd for C15H16N2O2 (%): C,
70.29; H, 6.29; N, 10.93. Found (%): C, 70.10; H, 6.18; N, 10.98.
Cl
8
7
O
2
4
1
N
6
3
5
N
H
O
2-(4-Chlorophenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3f)
Solid; m.p. 138–140 °C. IR (ATR): 1736 (C¼O) cmꢀ1
.
1H NMR
(400MHz, CDCl3, δ, ppm): 1.80–1.83 (m, 4H, –(CH2)2–), 2.38–2.41
(m, 4H, allylic 2CH2), 5.94 (s, 1H, NH), 6.67–6.71 (m, 2H, H6), 7.16–
7.24 (m, 2H, H7). 13C NMR (100 MHz, CDCl3, δ, ppm): 20.31 (C3),
21.30 (C2), 115.22 (C6), 127.06 (C8), 129.43 (C7), 140.82 (C5),
144.89 (C4), 169.07 (C1), assignments to C4 and C5 are interchange-
able. Anal. Calcd for C14H13ClN2O2 (%): C, 60.77; H, 4.74; N, 10.12.
Found (%): C, 60.58; H, 4.66; N, 10.15.
2-(3-Methyphenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3c)
1
Semisolid. IR (ATR): 1724 (C¼O) cmꢀ1. H NMR (400MHz, CDCl3,
δ, ppm): 1.72–1.75 (m, 4H, –(CH2)2–), 2.20 (s, 3H, CH3), 2.30–2.36
(m, 4H, allylic 2CH2), 5.26 (br s, 1H), 6.46–6.49 (m, 2H, H6 and
H8), 6.66–6.68 (m, 1H, H10), 7.00–7.04 (m, 1H, H9). 13C NMR
(100 MHz, CDCl3, δ, ppm): 20.25 (C11), 21.32 (C3), 21.69 (C2),
111.05 (C10), 114.55 (C6), 123.03 (C8), 129.24 (C9), 139.36 (C7),
140.59 (C4), 146.24 (C5), 169.28 (C1), assignments to C2, C3
and C11 are interchangeable, assignments to C6 and C10 are
interchangeable. HRMS (EI). Anal. Calcd for C15H16N2O2 (M+):
256.1212. Found: 256.1210. Anal. Calcd for C15H16N2O2 (%): C,
70.29; H, 6.29; N, 10.93. Found (%): C, 70.17; H, 6.25; N, 10.94.
5-Methyl-2-(phenylamino)-4,5,6,7-tetrahydro-2H-isoindole-1,3-dione (3 g)
1
Semisolid. IR (ATR): 1721 (C¼O) cmꢀ1. H NMR (400 MHz, CDCl3,
δ, ppm): 1.67–1.72 (m, 4H, CH3 and CH), 1.80–1.85 (m, 2H, CH2),
Appl. Organometal. Chem. 2015, 29, 226–230
Copyright © 2015 John Wiley & Sons, Ltd.
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I. C. Yoon and C. S. Cho
2.56–2.59 (m, 4H, allylic 2CH2), 6.03 (s, 1H, NH), 6.72–6.75 (m, 2H,
H12), 6.90–6.94 (m, 1H, H14) 7.18–7.23 (m, 2H, H13). 13C NMR
(100 MHz, CDCl3, δ, ppm): 25.04 (C10), 26.63 (C6 and C7), 30.26
(C4 and C5), 113.87 (C12), 122.07 (C14), 129.36 (C13), 141.58
(C8 and C9), 146.13 (C11), 170.14 (C1 and C3). HRMS (EI). Anal.
Calcd for C15H16N2O2 (M+): 256.1212. Found: 256.1210. Anal.
Calcd for C15H16N2O2 (%): C, 70.29; H, 6.29; N, 10.93. Found
(%): C, 70.00; H, 6.18; N, 10.97.
Acknowledgements
This research was supported by Basic Science Research Program
through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(2010–0007563).
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1
Semisolid. IR (ATR): 1728 (C¼O) cmꢀ1. H NMR (400MHz, CDCl3,
δ, ppm): 1.82–1.92 (m, 1H, CH2/2), 2.16–2.21 (m, 1H, CH2/2), 2.40–
2.52 (m, 2H, allylic CH2), 2.60–2.67 (m, 1H, allylic CH2/2), 2.75–2.81
(m, 1H, allylic CH2/2), 2.90–2.97 (m, 1H, CH), 6.04 (s, 1H, NH),
6.75–6.78 (m, 2H, H15), 6.91–6.95 (m, 1H, H17), 7.20–7.28 (m, 5H,
H11, H13, H16), 7.33–7.37 (m, 2H, H12), assignments to H11, H12
and H16 are interchangeable. 13C NMR (100MHz, CDCl3, δ, ppm):
21.03 (C7), 27.87 (C6), 28.96 (C5), 39.33 (C4), 113.91 (C15), 122.15
(C17), 126.90 (C13), 127.04 (C11), 128.94 (C12), 129.44 (C16),
140.36 (C8 and C9), 144.37 (C10), 146.20 (C14), 168.89 (C1), 168.92
(C3), assignments to C1 and C3 are interchangeable, assignments
to C11–C13 are interchangeable. HRMS (EI). Anal. Calcd for
C20H18N2O2 (M+): 318.1368. Found: 318.1369. Anal. Calcd for
C20H18N2O2 (%): C, 75.45; H, 5.70; N, 8.80. Found (%): C, 75.27; H,
5.58; N, 8.84.
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4132.
2-(4-Methyphenylamino)-2H-benzo[e]isoindole-1,3-dione (3i)
Solid; m.p. 166–168 °C. IR (ATR): 1724 (C¼O) cmꢀ1
.
1H NMR
(400 MHz, CDCl3, δ, ppm): 2.25 (s, 3H, CH3), 6.18 (s, 1H, NH), 6.79–
6.83 (m, 2H, H15), 7.04 (d, JHH = 8.1 Hz, 2H, H16), 7.67–7.76 (m, 2H,
H7 and H8), 7.91 (d, JHH = 8.3Hz, 1H, H6), 7.97 (d, JHH = 8.1Hz, 1H,
H5), 8.23 (d, JHH = 8.1Hz, 1H, H4), 8.91–8.94 (m, 1H, H9). 13C NMR
(100 MHz, CDCl3, δ, ppm): 20.81 (C18), 114.63 (C15), 118.92 (C9),
125.27 (C4), 125.49 (C16), 128.22 (C7), 129.01 (C12), 129.33 (C6),
129.38 (C17), 130.05 (C5 and C8), 132.00 (C13), 135.82 (C11),
137.02 (C10), 143.83 (C14), 167.38 (C1), 168.08 (C3), assignments
to C1 and C3 are interchangeable, assignments to C10 and C11
are interchangeable, assignments to C4–C8, C12, C16 and C17 are
interchangeable. HRMS (EI). Anal. Calcd for C19H14N2O2 (M+):
302.1055. Found: 302.1053. Anal. Calcd for C19H14N2O2 (%): C,
75.48; H, 4.67; N, 9.27. Found (%): C, 75.30; H, 4.59; N, 9.31.
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Appl. Organometal. Chem. 2015, 29, 226–230