Palladium-Catalyzed Benzofulvenation of o-Arylanilines through C?H Bond Activation by Using Two Diarylacetylenes as an Implicit Benzofulvene

Article abstract of DOI:10.1002/adsc.201801352

We report the first example of Pd(II)-catalyzed highly step- and atom-economical benzofulvenation through free amine-directed ortho C?H bond activation of o-arylanilines. This paper presents a novel, simple, and efficient approach for the synthesis of benzofulvene derivatives from o-arylaniline substrates through C?H bond activation with two diarylacetylenes as an implicit benzofulvene unit. The reactivity of synthesized benzofulvenes toward oxidation was investigated, and they were shown to transform into phenanthridines, oxabenzofulvenes, and fluorescent polycyclics. (Figure presented.).

Full text of DOI:10.1002/adsc.201801352

Title: Palladium-Catalyzed Benzofulvenation of <i>o</i>-Arylanilines
through C–H Bond Activation by Using Two Diarylacetylenes as
an Implicit Benzofulvene
Authors: Selvam Raju, Huan-Chang Hsiao, Selvakumar Thirupathi,
Pei-Ling Chen, and Shih-Ching Chuang
This manuscript has been accepted after peer review and appears as an
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To be cited as: Adv. Synth. Catal. 10.1002/adsc.201801352
Link to VoR: http://dx.doi.org/10.1002/adsc.201801352

10.1002/adsc.201801352
Advanced Synthesis & Catalysis
COMMUNICATION
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Palladium-Catalyzed Benzofulvenation of o-Arylanilines
through C–H Bond Activation by Using Two Diarylacetylenes
as an Implicit Benzofulvene
Selvam Raju,a Huan-Chang Hsiao,a Selvakumar Thirupathi,a Pei-Ling Chen,b and Shih-
Ching Chuanga,*
a
Department of Applied Chemistry, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu, Taiwan 30010
E-mail: jscchuang@faculty.nctu.edu.tw
Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30013
b
Received: ((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
through the intramolecular coupling of alkynes,
followed by palladium-catalyzed arylation.[13]
Abstract: We report the first example of Pd(II)-catalyzed
highly step- and atom-economical benzofulvenation
through free amine–directed ortho C−H bond activation
of o-arylanilines. This paper presents a novel, simple, and
efficient approach for the synthesis of benzofulvene
derivatives from o-arylaniline substrates through C–H
bond activation with two diarylacetylenes as an implicit
benzofulvene unit. The reactivity of synthesized
benzofulvenes toward oxidation was investigated, and
they were shown to transform into phenanthridines,
oxabenzofulvenes, and fluorescent polycyclics.
In another context, since Murai et al. developed the
first efficient method of metal-catalyzed alkylation by
using ketone as the directing group (DG) through C–
H bond activation,[14] transition-metal-catalyzed C–H
bond activation has emerged as a powerful tool for
selective C–H functionalization.[15] Transition metals,
such as rhodium,[16] iridium,[17] cobalt,[18] and
palladium,[19] have been used to catalyze
cycloaddition of acetylenes with 2-alkenyl anilines,
phenols, N-substituted anilines, and aryl iodides,
respectively, mainly yielding substituted indolines,
chromenones, and an extended aromatic π-system.
Keywords: benzofulvene; C–H bond activation;
diphenylacetylene; o-arylaniline; palladium
Furthermore,
iminoquinone,[20]
carbonyl,[21]
sulfonyl,[22] alkyl,[23] and aryl-masked[24] amino
groups have been identified as favorable groups for
directing C–H bond cleavage at the ortho or 2′-
position of o-phenylanilines and enabling transition-
metal-catalyzed insertion of activated olefins,
Benzofulvenes are benzo derivatives of fulvenes and
aromatic hydrocarbons consisting of an exocyclic
double bond.[1] Because of their unique molecular
properties, benzofulvenes have extensive applications
in the fields of material science[2] and
pharmaceutical,[3] polymer,[4] and ligand[5] chemistry.
Numerous methodologies have been developed for
the synthesis of fulvene skeletons, which are based on
the Schmittel cyclization of enyne-allene,[6]
Schreiner–Pascal diradical cyclization of enediynes,[7]
silver and Brønsted acid-catalyzed Nazarov
cyclization of diaryl α-hydroxyallenes,[8] transition-
metal-catalyzed cyclization of aromatic ketones with
internal alkynes,[9] gold(I)- and dual-gold(I)-catalyzed
intramolecular cyclization of arene–diyne,[10] and Pd-
catalyzed cycloisomerization of aromatic 1,5-
enynes.[11] In addition, Hua et al. reported the Pd(II)-
diaryliodonium
intramolecular cyclization to yield phenanthridines,
substituted triphenylenes, phenanthridinones,
fullerobenzoazepines, and carbazoles, respectively.
salts,
CO,[60]
fullerene,
or
catalyzed
cyclodimerization
reaction
of
diarylacetylenes to obtain benzofulvene derivatives
through alkyne-directed ortho C−H palladation,
followed by insertion of another diarylacetylene and
cyclization.[12] Furthermore, benzofulvenes can be
synthesized
using
1,2-bis(arylethynyl)benzenes
1
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
Scheme
1.
Transition-metal-catalyzed
C2'−H
(TFE) and hexafluoroisopropanol (HFIP), and no
appreciable amounts of product were produced (entry
7). The solvent DCM outperformed others probably
because of its lower boiling point and aprotic
property. DCM is capable of making a pseudo
gaseous state under high pressure and temperature
conditions, which results in faster second alkyne
insertion. We noted that phenanthridine 4a was
formed in a favorable yield when DMF, DMAc, o-
DCB, and CB were used. Replacement of Cu(OAc)2
functionalization of o-arylanilines.
To our knowledge, using a free amino directing group
(DG)[25] is one of the most straightforward
approaches of C–H bond activation, especially from
an industrial perspective.[26] Moreover, amino groups
can be converted for use in other processes by using
the Sandmeyer reaction.[27] In this context, Miura
reported
the
Ru-catalyzed
amine-directed
.
with another oxidizing agent—such as CuSO4 5H2O,
alkenylation of o-arylanilines with internal alkynes
(Scheme 1a).[28] Subsequently, Luan demonstrated the
palladium-catalyzed [5+2] oxidative annulation of o-
Cu(BF4)2, AgOAc, PhI(OAc)2, or O2—resulted in
chemical transformations becoming productless
(entry 8). However, after the substitution of
Cu(OAc)2 by CuOAc as an oxidant, an appreciable
amount of the corresponding product 3a was obtained
(entry 9). Use of different palladium catalysts, such
as PdCl2, PdCl2(PPh3)2, PdCl2(CH3CN)2, and
Pd(PPh3)4, did not result in superior product
formation to using Pd(OAc)2 for ortho-
benzofulvenation (entries 10−13).
arylanilines
dibenzo[b,d]azepines (Scheme 1b).[29] We developed
an efficient palladium-catalyzed [2+2+2]
cycloaddition of N-substituted o-arylanilines with
diarylacetylenes to obtain multisubstituted
with
alkynes
to
obtain
naphthalenes.[30] Here, we perceive that C2'-
benzofulvenation is possible if the alkenyl-palladium
intermediate resulting from the first alkynyl insertion
can undergo second alkynyl insertion and cyclization.
This approach may result in benzofulvenation
through C–H bond activation with two
diarylacetylenes acting as an implicit benzofulvene
unit (Scheme 1c). This method would be
synthetically valuable because the benzofulvene
moiety has not previously been identified as a
transmetallization reagent for functionalization. The
benzofulvenated o-arylanilines can be transformed
into fluorescent diarylazulenes and phenanthridines,
with forthcoming applications in the materials
science and pharmaceutical fields, respectively.
Table 1. Optimization of the reaction conditions[a]
Entry
Deviations from standard conditions
3a/4a
Yield
(%)[b]
1
2
3
4
5
6
7
8
No deviation
100:0
51:49
100:0
47:53
71:29
100:0
-
85
DMFinstead of DCM
DMAc instead of DCM
o-DCB instead of DCM
CB instead of DCM
DCE instead of DCM
35
18
This work was originally undertaken in our recent
study on the palladium(II)-catalyzed [2+2+2]
annulation of N-([1,1'-biphenyl]-2-yl)acetamides with
alkynes through C–H bond activation.[30] After an
extensive survey of reaction parameters, we
summarized the crucial optimization conditions
(Table 1). We first investigated the reaction of 2'-
methylbiphenyl-2-amine (1a) and diphenylacetylene
(2a) as model substrates in the presence of Pd(OAc)2
as the catalyst (10 mol%), Cu(OAc)2 as the oxidant
(1.5 equiv.), and dichloromethane (DCM, 2 mL) as
the solvent in a pressure-affordable sealed tube,
which resulted in the unusual ortho-benzofulvenation
product 3a in a favorable yield (85%) at 100 °C
(Table 1, entry 1). Next, the role of each component
32
45
56
Solvent = TFE or HFIP
trace
ND[e]
.
Oxidant
=
CuSO4 5H2O, Cu(BF4)2,
-
AgOAc, PhI(OAc)2 or O2
9
CuOAc instead of Cu(OAc)2
100:0
100:0
100:0
100:0
100:0
100:0
100:0
100:0
-
61
10
11
12
13
14
15
16
17
PdCl2 instead of Pd(OAc)2
55
PdCl2(PPh3)2 instead of Pd(OAc)2
PdCl2(CH3CN)2 instead of Pd(OAc)2
Pd(PPh3)4 instead of Pd(OAc)2
Cu(OAc)2 1.0 equiv. instead of 1.5 equiv
O2 flushed for 5 minutes instead of air
N2 flushed for 5 minutes instead of air
condition A[c] or condition B[d]
54
60
was
investigated
through
parameter-tuning
experiments. When DCM was replaced with other
polar solvents, such as N,N-dimethylformamide
(DMF) and N,N-dimethylacetamide (DMAc), or
chlorinated solvents, such as ortho-dichlorobenzene
(o-DCB) and chlorobenzene (CB), benzofulvene 3a
was obtained in low yields in addition to a side
product, phenylphenanthridine 4a, in various yields
(entries 2–5). When 1,2-dichloroethane (DCE) was
used as the solvent, the desired product was obtained
in a 56% yield and with favorable selectivity (entry 6).
This reaction was performed with various fluorinated
alcoholic solvents, such as 2,2,2-trifluoroethanol
39
77
62
66
ND[e]
[a]Reaction conditions: 1 (0.30 mmol), 2 (0.72 mmol), Cu(OAc)2 (0.45
mmol), and 10 mol% palladium catalyst under air atmosphere in a sealed
tube unless otherwise stated. [b]Yields were measured using 1H NMR
[c]
spectroscopy with mesitylene as the internal standard.
Condition A:
2
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
The reaction was completed using Pd(OAc)2 (10 mol%), LiBr (0.4 mmol),
pivalic acid (0.6 mmol), and NaOPiv (0.4 mmol) in DMAc (2 mL) at
80 °C for 30 h. [d] Condition B: The reaction was completed using PdCl2
(15 mol%), AgOTf (1.0 equiv.), and o-chloranil (1.0 equiv.) in DMAc (2
mL) at 60 °C for 24 h. [e]ND denotes not detected.
diphenylacetylene (2c), it produced 3d in a yield of
62%, a slightly lower yield compared with that
obtained with 1a. Furthermore, substrates containing
electron-withdrawing groups (EWG), such as para-
chloro (2d) and para-bromo (2e), substituted
diarylethynes and 1a afforded products 3e and 3f in
moderate yields (50%–52%). The reactions
performed with unsymmetrical alkynes such as 1-
phenyl-1-propyne (2f) and 1-phenyl-1-butyne (2g)
formed regioselective products 3g and 3h,
respectively, in yields of 51%–62%. Similarly, 2-
(naphthalen-1-yl)aniline (1i) treated with 1-phenyl-1-
butyne (2g) under standard conditions produced 49%
of 3i. The regiochemistry of the benzofulvenation
reaction with asymmetric alkynes was verified
through the single-crystal structure of 3h.[32]
Reducing the amount of Cu(OAc)2 (1 equiv.) as an
oxidant reduced the formation of the desired product
(entry 14). Furthermore, the presence of excessive
oxygen and nitrogen appeared detrimental to the
chemical process (entries 15 and 16). Excessive
oxygen may deactivate palladium catalysts, whereas
the absence of sufficient oxygen prevents oxidation
of Cu(I) to Cu(II) in the catalytic cycle. Notably, both
condition A (that of Hua) for the synthesis of
benzofulvene and condition B[31] (that of Itami) for
the synthesis of pentalenes from diarylacetylenes
were ineffective (entry 17).
Table 3. Substrate scope of 2-arylanilines[a]
Table 2. Substrate scope of alkynes[a]
[a]All reactions were performed using 1 (0.30 mmol), 2 (0.72 mmol),
Pd(OAc)2 (0.03 mmol), Cu(OAc)2 (0.45 mmol), and DCM (2 mL) in a
sealed tube at 100 °C under air for 24 h.
The reaction scope of ortho-benzofulvenation was
examined under optimized conditions with other
substituted alkynes (2b-2g) containing electron-rich
or electron-deficient aromatic groups and alkyl
substituents, as shown in Table 2. The symmetrically
substituted 1,2-diarylethynes bearing electron-
donating groups (EDG) on the para position of the
aryl rings, such as methyl (2b) and methoxy (2c)
groups, afforded products 3b and 3c in favorable
yields (72%–74%). When 2-(naphthalen-1-yl)aniline
(1i) was treated with para-methoxy-substituted
[a]All reactions were performed using 1 (0.30 mmol), 2a (0.72 mmol),
Pd(OAc)2 (0.03 mmol), Cu(OAc)2 (0.45 mmol), and DCM (2 mL) in a
sealed tube at 100 °C under air for 24 h. [b]The reaction was performed
using 2a (1.44 mmol), Pd(OAc)2 (0.06 mmol), Cu(OAc)2 (0.9 mmol), and
DCM (4 mL) at 100 °C under air for 24 h. [c]The reaction was performed
3
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
using 3p' (0.10 mmol), 2a (0.24 mmol), Pd(OAc)2 (0.01 mmol),
product 3aa'' resulted in an unsatisfactory yield.
Furthermore, 2'-methyl-[1,1'-biphenyl]-2-amine (1a)
was treated with benzofulvene 5 under optimized
standard conditions, but the desired product 3a was
not obtained (Scheme 2b). This indicated that
benzofulvene was not formed first in this reaction.
Furthermore, benzofulvene 5 was not observed due to
the dimerization of diphenylacetylenes under the
standard conditions (Scheme 2c). Treatment of 3a
under standard conditions obtained a trace amount of
secondary product 4a with nearly full recovery of 3a
(Scheme 2d). Unfortunately, the reaction involving
ortho-vinylaniline (1v) did not result in a selective
benzofulvenation product under the optimized
conditions, and the product decomposed quickly upon
isolation (Scheme 2e). Free-amine DG-assisted C−H
bond activation was investigated using a deuterium-
labelling experiment. The intermolecular kinetic
isotope effect study revealed kH/kD values of 1.69 and
1.87 for formation of 3aa and 3aa', respectively, in a
10 min reaction. This indicated that C−H bond
activation was probably the rate-determining step
(Scheme 2f). These experimental results indicated
that the benzofulvenation proceeded through amine-
directed C−H bond activation followed by two
respective alkyne insertions to obtain benzofulvenes.
Cu(OAc)2 (0.15 mmol), and DCM (2 mL) at 100 °C under air for 24 h.
Next, the substrate scope was surveyed using a
number
of
o-arylanilines
(1b−1r)
for
benzofulvenation (Table 3). We discovered that
substrate 1, which bears an EDG (4-methyl) or EWG
(4-trifluoromethoxy or 4-chloro) on the upper aryl
ring, reacted smoothly with diphenylacetylenes to
deliver the corresponding benzofulvenation products
(3a'-3c', 50%–85%). The substrates with an EDG (5-
methyl) or EWG (5-fluoro) substitution in the upper
ring of o-arylanilines reacted with 2a to produce the
desired products 3d' and 3e' in yields of 78% and
68%, respectively. Similarly, substrates bearing EDG
and EWG groups such as dimethyl and difluoro
moieties on the lower ring resulted in the desired
products 3f' and 3g' in good yields (72%–82%). The
2-naphthyl anilines reacted with 2a and produced the
benzofulvene product 3h' in a high yield (81%).
However, the reaction involving a substrate bearing
an EDG (4-methyl) on the upper aryl ring afforded
the corresponding product 3i' in a 65% yield.
Furthermore, the substrates bearing EWGs such as 4-
trifluoromethoxy, 4-fluoro, 4-chloro, and 5-fluoro in
the upper aryl ring reacted with 2a to yield the
desired products 3j'–m' (52%–75%). The substrate
with a 2-naphthyl moiety possessing a tetraphenyl
substitution group produced the desired product 3n'
in a 71% yield. This methodology could be extended
not only to the benzofulvenation of substrates with a
dibenzo[b,d]furan moiety (3o': 88% yield) but also to
substrates with o,o'-diphenyl and o,o'-ortho tolyl
substitutions on the aniline ring, yielding the desired
products 3p' and 3q' in 41% and 39% yields,
respectively. The attempt to perform direct bis-
benzofulvenation was not straightforward in this one-
pot
reaction.
However,
isolated
mono-
benzofulvenation compound 3p' could be treated
with 2a to obtain the bis-benzofulvenation product
3r' in a yield of 26% under standard conditions. The
lower yields obtained in the first and second
benzofulvenation were mainly due to the steric effect
exerted by the aryl moiety in the 6 position. This
steric effect reduced the tendency of second alkyne
insertion. Finally, poor yields were also obtained
using the substrates with EWGs in the upper aryl ring,
such as those with 4-trifluoromethyl and 4-cyano,
which reacted with 2a to yield 3s' and 3t' in yields of
47% and 15%, respectively.
We conducted a series of experiments to analyze the
reaction mechanism (Scheme 2). Treatment of o-
phenylaniline (1s) with alkyne 2a (4.8 equiv)
afforded the products 3aa, 3aa', and 3aa'' in a
33:42:25 ratio (Scheme 2a). The phenanthridine
moiety in 3aa and 3aa' was likely formed due to
oxidation of the exocyclic double bond in
benzofulvene by oxidants and then condensation with
amines. Thus, formation of the bis-benzofulvene
Scheme 2. Control experiments.
4
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
A plausible reaction mechanism based on these
results and transition-metal-catalyzed C–H bond
activation/oxidative cycloaddition reaction is
proposed (Scheme 3). Initially, an ortho C–H bond is
activated on the 2-aryl moiety of 1 by Pd(II) to yield
treated 3a with p-benzoquinone (p-BQ), AcOH,
and Cu(OAc)2 in CB. Unexpectedly, the
exocyclic double bond of the benzofulvene
moiety was oxidized and condensed with amine
to afford phenylphenanthridine 4a in a 72% yield.
Furthermore, we attempted to synthesize
iptycenes through the treatment of compound 3h'
with p-BQ, AcOH, and Cu(OAc)2 in o-DCB at
140 °C.[33] However, the exocyclic double bond
was oxidized and condensed with amine to give
phenanthridine 7 in a 68% yield. Notably, a by-
product indenone 6 was isolated in a 57% yield.
When 3a was treated with m-CPBA, however, 3a
was converted into the endocyclic epoxidation
products 8a and 8b in yields of 52% and 30%,
respectively.
six-membered
palladacycle
intermediate
I.
Subsequently, alkyne 2a undergoes coordination and
migratory insertion to yield the eight-membered
palladacycle intermediate III through intermediate II.
The intermediate III propagates the second
coordination and insertion of the alkyne through
intermediate IV to yield V. The reaction does not
proceed through intermediate IVB formed via IVA or
VIB to produce the previously observed
multisubstituted naphthalenes VIII under developed
conditions.[30] Instead, it proceeds via a six-membered
palladacycle through C–H bond activation to obtain
the ortho-benzofulvene product 3 through reductive
elimination and generated Pd(0). To continue the
catalytic cycle, Pd(0) is reoxidized into Pd(II) by
Cu(II). In the presence of oxygen, 3 undergoes
oxidation to give VII; subsequent condensation
yields the phenylphenanthridine product 4a. In our
experiments, we did not observe Miura's alkenylation
product IX due to absence of a proton source.28
Luan's dibenzo[b,d]azepines X, which are formed
through reductive elimination from III, were also not
formed under our conditions. Why the reaction
proceeded along a different pathway under our
conditions remains unclear, but it is likely that under
our conditions performed in dichloromethane (b.p.
39.6 °C at 760 mmHg) at 100 °C in a pressure-
affordable tube, the second alkyne insertion occurred
more quickly to give V instead of undergoing
reductive elimination to give X.
Conditions: A) 3a (0.1 mmol), p-BQ (1.2 equiv.), AcOH (1.5 equiv.),
Cu(OAc)2 (0.2 equiv.), CB (2 mL), 120 °C, 24 h, air. B) 3h' (0.1 mmol),
Cu(OAc)2 (2 equiv.), p-BQ (1.2 equiv.), AcOH (1.5 equiv.), o-DCB (2
mL), 140 °C, 24 h, air. C) 3a (0.1 mmol), m-CPBA (0.4 mmol), DCM (2
mL), room temperature, 24 h, air. D) 3a (0.1 mmol), TfOH (20 equiv.),
DCM (4 mL), room temperature, 4 h, air.
Scheme 4. Synthetic transformations of benzofulvene 3.
This indicated that the endocyclic alkene of
benzofulvene was more reactive than the exocyclic
alkene moiety toward epoxidation. Furthermore,
when 3a was treated with equimolar amount of m-
CPBA (1.1 equiv), the amine group was first oxidized
to a nitroso group (8c, see in SI). This result
confirmed that the amine moiety was more reactive
than the endocyclic double bond. Finally, another
synthetic transformation was illustrated by treating 3a
with TfOH in DCM at room temperature. This
reaction
produced
stereoselective
polycyclic
compound 9 with a 5- and 7-membered fused azulene
core structure in a 64% yield (refer to the SI for a
proposed mechanism). The unusual structure 9
exhibited fluorescent emission at 396 nm with
quantum yields of 39% in a chloroform solution
(Figure S1 and S2 in the SI). These ortho-
benzofulvenation and oxidation products were
1
unambiguously identified using H nuclear magnetic
resonance (NMR) and 13C NMR spectroscopy and
single-crystal X-ray diffraction analysis.[32]
Scheme 3. Proposed catalytic cycle for benzofulvenation.
To demonstrate the synthetic utility of this
benzofulvenation methodology (Scheme 4), we
In conclusion, we demonstrated unprecedented free
amine–directed
sequential
Pd-catalyzed
5
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
benzofulvenation by using two diarylacetylenes as an
implicit benzofulvene moiety. The benzofulvenation
exhibited robustness because it did not require the
exclusion of air and demonstrated a new mode of
reactivity between diarylacetylenes and o-
phenylanilines. The endocyclic alkene moiety of
benzofulvenes was more reactive than the exocyclic
moiety toward epoxidation. The new benzofulvenes
can be further transformed into fluorescent
polycyclics, which have applications in material
science.
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[8]
[9]
[10]
Experimental Section
[11]
[12]
[13]
(Z)-2'-((2,3-diphenyl-1H-inden-1-
ylidene)(phenyl)methyl)-6'-methyl-[1,1'-biphenyl]-2-
amine derivatives (3)
An oven-dried 35-mL pressure-affordable tube equipped
with a stirring bar was charged with Pd(OAc)2 (10 mol %),
Cu(OAc)2 (0.45 mmol), o-arylanilines (0.30 mmol), and
diarylacetylenes (0.72 mmol) in distilled DCM (2.0 mL)
under atmospheric conditions. The pressure tube was then
closed using a screw cap, and the reaction mixture was
heated for 24 h at 100 °C with constant stirring. Upon
cooling to room temperature, the reaction mixture was
diluted with 10 mL of ethyl acetate, after which filtration
was performed through a thin pad of Celite. The filtrate
was concentrated in a vacuum, and the residue was then
purified using flash chromatography (hexanes:ethyl acetate
= 10:1) to afford product 3.
[14]
[15]
a) T. G. Saint-Denis, R. Y. Zhu, G. Chen, Q. F.
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Acknowledgements
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We thank the Ministry of Science and Technology of Taiwan for
supporting this research financially (MOST104-2113-M-009-
014-MY3
and
MOST105-2628-M-009-002-MY3).
This
manuscript was edited by Wallace Academic Editing.
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7
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10.1002/adsc.201801352
Advanced Synthesis & Catalysis
COMMUNICATION
Palladium-Catalyzed Benzofulvenation of o-
Arylanilines through C–H Bond Activation by
Using Two Diarylacetylenes as an Implicit
Benzofulvene
Adv. Synth. Catal. Year, Volume, Page – Page
S. Raju,a H.-C. Hsiao,a S. Thirupathi,a P.-L. Chen,b
and S.-C. Chuanga,*
8
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