Palladium-catalyzed formation of highly substituted naphthalenes from arene and alkyne hydrocarbons

Article abstract of DOI:10.1002/chem.200800538

Several highly substituted naphthalenes 3 have been synthesized in a one-pot reaction by treatment of arenes 1 with alkynes 2 in the presence of palladium acetate and silver acetate. In this Pd-catalyzed protocol, an arene provides a benzo source for the construction of a naphthalene core through twofold aryl C - H bond activation. Reaction of triphenylphosphine with diphenylethyne (2 a) under the catalysis of Pd^IV complexes produced 1,2,3,4-tetraphenylnaphthalene (3ba) in 62% yield. Here, triphenylphosphine undergoes one aryl C - P bond cleavage and one aryl C - H bond activation to serve as a benzo moiety. Crystal structures of cycloadducts 3ea, 3ga, and 3ac have been analyzed. The twisted naphthalenes arise not only from the overcrowded substituents but also from the contribution of the CH₃-π interaction.

Full text of DOI:10.1002/chem.200800538

FULL PAPER
DOI: 10.1002/chem.200800538
Palladium-Catalyzed Formation ofHighly Substituted Naphthalenes rfom
Arene and Alkyne Hydrocarbons
Yao-Ting Wu,* Ke-Hsin Huang, Chien-Chueh Shin, and Tsun-Cheng Wu[a]
À
Abstract: Several highly substituted
naphthalenes 3 have been synthesized
in a one-pot reaction by treatment of
arenes 1 with alkynes 2 in the presence
of palladium acetate and silver acetate.
In this Pd-catalyzed protocol, an arene
provides a benzo source for the con-
with diphenylethyne (2a) under the
catalysis of PdIV complexes produced
1,2,3,4-tetraphenylnaphthalene (3ba) in
62% yield. Here, triphenylphosphine
undergoes one aryl C P bond cleavage
À
and one aryl C H bond activation to
serve as a benzo moiety. Crystal struc-
tures of cycloadducts 3ea, 3ga, and 3ac
have been analyzed. The twisted naph-
thalenes arise not only from the over-
crowded substituents but also from the
contribution of the CH3–p interaction.
À
Keywords: alkynes · C P cleavage ·
À
C H activation · crystal engineer-
struction of
a
naphthalene core
ing · cyclization · naphthalene ·
À
through twofold aryl C H bond activa-
tion. Reaction of triphenylphosphine
palladium
Introduction
similar manner, hydroarylation reactions have been applied
in the synthesis of coumarins and their derivatives from aryl
alkynoates[9,11] or phenols and alkynoates.[3b,12]
À
À
Catalytic activation of aryl C H bonds with subsequent C
C bond formation is one of the most attractive endeavors
for synthetic chemists, because such processes provide par-
ticularly efficient tools for the construction of valuable and
versatile intermediates.[1] This concept offers several advan-
These previously reported methods mainly concern the
À
monoarylation of alkynes by cleavage of one C H bond on
an arene unit, that is, one aryl moiety is attached. Recently,
we observed that naphthalenes can be formed under palladi-
um catalysis from one arene and two molecules of an
alkyne. This is the first example, to the best of our knowl-
edge, in which an arene provides a benzo unit to furnish a
[2]
tages:simplicity, cleanliness, and atom economy. Fujiwara
et al. reported that Pd- and Pt-catalyzed trans-hydroaryl-
ACHTREUNGations of alkynes in trifluoroacetic acid selectively form cis-
arylalkenes.[3] In contrast, in the presence of a trialkylborane
and a dinuclear palladium complex, cis-hydroarylations of
alkynes can be achieved by following the protocol of Tsuka-
da et al.[4] Under the catalysis of metal trifluoromethanesul-
naphthalene core by twofold aryl C H activation on the
À
same arene. Therefore, we optimized the reaction conditions
and tested various arenes to develop a new and simple
method for the preparation of highly substituted naphtha-
lenes.[13]
fonates [MACHTREUNG
(OTf)n] (M=In, Sc, Zr),[5] and AuI[6a,b,7] or AuIII[7]
complexes, hydroarylation of terminal arylethynes generates
1,1-diarylalkenes. However, AuIII-catalyzed hydroarylation
of terminal electron-deficient alkynes (e.g., alkynoates)
under solvent-free conditions produces cis-1,2-disubstituted
alkenes.[7] Intramolecular hydroarylation of alkynes can also
be catalyzed by RuII,[9] PtII,[9,10] or AuI[6a,c,10] complexes. In a
Results and Discussion
Limited systematic studies of the reaction conditions for the
synthesis of 5,8-dimethyl-1,2,3,4-tetraphenylnaphthalene
(3aa) from p-xylene (1a) and diphenylacetylene (2a)
showed that AgOAc and Pd
reaction (Table 1). Two equivalents of AgOAc (relative to
alkyne 2a) had to be used for best results. Pd(OAc)2 and K2-
[PdCl6] both turned out to be efficient catalysts, but the
former is better than the latter (compare entries 10 and 13
in Table 1). Other palladium complexes, such as [Pd(PPh3)4]
and [PdCl2A(PPh3)2], did not provide the desired co-cycliza-
ACHTREU(NG OAc)2 played key roles in this
[a] Prof. Y.-T. Wu, K.-H. Huang, C.-C. Shin, T.-C. Wu
Department of Chemistry, National Cheng Kung University
No. 1 Ta-Hsueh Rd., 70101 Tainan (Taiwan)
Fax :( +886)6-274-0552
AHCTREUNG
AHCTREUNG
E-mail:ytwuchem@mail.ncku.edu.tw
ACHTREUNG
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
CTHREUNG
Chem. Eur. J. 2008, 14, 6697 – 6703
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6697

Table 1. Optimization of reaction conditions for the preparation of 5,8-
dimethyl-1,2,3,4-tetraphenylnaphthalene (3aa) from p-xylene (1a) and
diphenylacetylene (2a).
go co-cyclizations with alkyne 2a. Anisole (1p) and 1,2-di-
methoxybenzene (1q) generated the corresponding products
in very low yields (less than 10%) under a nitrogen atmos-
phere (A conditions), but the yields could be improved
when the reactions were carried out under air (B condi-
tions). Dimethylanisoles gave better results than anisole and
1,2-dimethoxybenzene. Bulky substituents (especially iPr
and tBu) in 1,3- and 1,4-disubstituted benzenes led to lower
yields than methyl groups. Mono- and 1,2-disubstituted ben-
zenes each yielded two regioisomeric co-cyclization prod-
ucts. Toluene, o-xylene, and anisole generated regioisomers
in ratios close to 1:1 (entries 3, 11, and 16 in Table 2). How-
ever, the reaction of o-xylene with bis(4-tert-butylphenyl)-
Entry Catalyst (mol%)[a]
Solvent
Additives (equiv) Yield [%]
1
2
3
4
5
6
7
8
Pd
Pd
A
C
p-xylene AgOAc (2)
p-xylene AgOAc (0.4)
(PPh3)2] (20) p-xylene AgOAc (1)
24
16
G
trace[b]
0[c]
G
p-xylene AgOAc (1)
p-xylene AgOAc (1)
Pd
Pd
Pd
Pd
Pd
Pd
Pd
Pd
0[c]
35
30
MeCN
DMF
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (1)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AgOAc (2)
AHCTREeUNG thyne (2b) produced 3kb-a and 3kb-b in an 87:13 ratio
(entry 30 in Table 2). Bicyclic arenes, such as, indane (1n)
and 1,2,3,4-tetrahydronaphthalene (1o), have also been uti-
lized in this reaction, and the former provided a higher yield
and regioselectivity than the latter. Remarkably, 5,6-dialkyl-
1,2,3,4-tetraarylnaphthalenes were obtained as the major
products from 1,2-dialkylbenzenes, whereas 1,2-dimethoxy-
benzene (1q) formed 6,7-dimethoxy-1,2,3,4-tetraphenyl-
naphthalene (3qa-b) as the almost exclusive cycloadduct.
Apparently, diarylethynes, such as 1,2-diphenylethyne
(2a), 1,2-di(4-alkylphenyl)ethynes, and 1,2-di(4-fluorophen-
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
52[d]
29[d,e]
55[d]
60[d]
56[d,f]
30[d]
9
10
11
12
13
K2ACHTREUNG
[a] The amounts of catalysts and additives, and the chemical yields are
relative to the amount of alkyne. [b] 32% yield (relative to PPh3 from
[PdCl2ACHTREUNG(PPh3)2]) of 1,2,3,4-tetraphenylnaphthalene (3ba) was isolated.
[c] Most of 2a was recovered. [d] The alkyne was added to the reaction
mixture within 10 h with a syringe pump. [e] 37% of the alkyne was re-
covered. [f] The reaction was carried out under air for 16 h instead of
under a N2 atmosphere.
AHCTREyUNG l)ethyne (2d), are most suitable for these co-cyclizations. 4-
Octyne (2g) and 3,3-dimethyl-1-phenyl-1-propyne (2h) did
not yield the correspondingly substituted naphthalenes from
p-xylene, and dimethyl acetylenedicarboxylate (2 f) fur-
nished tetraester 3af in very low yield. Reaction of p-xylene
with an asymmetric alkyne, such as, methyl phenylpropiolate
(2i), produced naphthalene derivatives 3ai and 3’ai in 23
and 13% yields, respectively. Traces of regioisomer 3’’ai can
also be detected.
Highly substituted naphthalenes have been found to have
twisted naphthalene cores that accommodate the steric re-
pulsion. The usual twist angle for octasubstituted naphtha-
lenes is approximately 20–308.[16] X-ray quality crystals of 5-
n-butyl-8-methyl-1,2,3,4-tetraphenylnaphthalene (3ea), 5,8-
diisopropyl-1,2,3,4-tetraphenylnaphthalene (3ga) and 5,8-di-
tion product 3aa. When the reaction was carried out in
either acetonitrile or N,N-dimethylformamide, 3aa was ob-
tained with higher purity relative to that obtained in p-
xylene. Although the alkyne 2a was completely consumed
under these conditions, the yields were still low.[14] Fortu-
nately, slow addition of 2a to the reaction mixture (within
10 h) increased the yield from 35 to 52% (compare entries 6
and 8 in Table 1). Under the optimized reaction conditions
(PdACHTREUNG(OAc)2 (7.5 mol%) and AgOAc (2 equiv) in acetonitrile
at 1108C), 3aa could be obtained in 60% yield (entry 11 in
Table 1). In addition, the reaction time could be decreased
from 36 to 16 h when the reaction was carried out under air,
instead of under a nitrogen atmosphere.
methyl-1,2,3,4-tetraACHTRE(UNG 4-tolyl)naphthalene (3ac) were grown
Reactions of various benzene derivatives 1 with internal
alkynes 2 were examined. Benzene and toluene furnished
3ba and 3ca, respectively, in low yields and unsatisfying pu-
rities (entries 2 and 3 in Table 2). Although dialkylbenzenes
provided clean products in higher yields than benzene and
toluene, trimethylbenzenes generated the cycloadducts ex-
clusively in similar yields (Table 2). In contrast to p-xylene
(1a) and 1,2,4-trimethylbenzene (1l), the electron-deficient
2-chloro-p-xylene (1r) showed lower reactivity in this co-
cyclization reaction (entries 1, 12 and 18 in Table 2). Bromo-
substituted xylenes are not suitable starting materials in this
protocol. 2-Bromo-1,4-dimethylbenzene (1s) produced the
debrominated cycloadduct 3aa in 64% yield (entry 19 in
Table 2).[15] 2-Bromo-1,3-dimethylbenzene (1w) did form the
bromo-substituted product 3wa, but the conversion and
from CH2Cl2/MeOH. Compound 3ea easily formed a large
crystal in contrast to the other naphthalenes described in
this article. According to crystallographic analyses, com-
pounds 3ea, 3ga, and 3ac display naphthalene cores with
overall twist angles of 23.9, 22.3, and 20.78, respectively
(Table 3).[17,18] The contribution of the end-to-end twist from
the tetraarylbenzo ring for 3ea (13.18) is slightly larger than
that for 3ga (10.78) and 3ac (11.28). In addition, compounds
3ea and 3ac show intermolecular interactions and two naph-
thalene molecules form a pair through two CH3–p interac-
tions (Figure 1). Examples of CH3–p interactions, such as
those in calix[4]arene·toluene complexes, have been previ-
ously reported.[19] The methyl carbon atom in the central
naphthalene core of 3ea and 3ac lies approximately 3.58
and 3.73 Š, respectively, from the tetraarylbenzo plane, de-
pending on the conformation of the methyl group; therefore
the intermolecular distance of one methyl hydrogen atom to
yield were low (entry 23 in Table 2). Hetero
ACHTREaUNG tom-substituted
arenes, such as aniline, pyrrole, and pyridine, did not under-
6698
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Chem. Eur. J. 2008, 14, 6697 – 6703

Palladium-Catalyzed Synthesis of Napthalenes
FULL PAPER
Table 2. Preparation of naphthalene derivatives 3 from arenes 1 and internal alkynes 2.
Entry
Arene
R1
R2
R3
R4
Alkyne
R5
Conditions
Product
Yield [%][a]
Procedure
1
2
3
1a
1b
1c
Me
H
Me
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
H
2a
2a
2a
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
A
A
A
3aa
3ba
3ca-a
3ca-b
3da
3ea
3 f
3ga
3ha
3ia
3ja
3ka-a
3ka-b
3la
3ma
3na-a
3na-b
3oa-a
3oa-b
3pa-a
3pa-b
3qa-a
3qa-b
3ra
3 sa
3ta
3ua
3va
3wa
3ab
3ac
3ad
3ae
3af
3ag
3kb-a
3kb-b
60
17
GP1
GP1
ꢀ
ꢀ
15[b]
GP1
H
4
5
6
7
8
9
10
11
1d
1e
1 f
1g
1h
1i
Et
Et
Me
Me
iPr
Me
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
2a
2a
2a
2a
2a
2a
2a
A
A
A
A
A/B
A
A
35[c]
27[c]
37
GP1
GP1
GP1
GP1
GP1
GP1
GP1
nBu
iPr
iPr
tBu
Me
iPr
Me
H
a
17[c]
6
H
H
H
Me
iPr
H
Me
H
43(35[c]
31
)
1j
Me
Me
Me
Me
À
1k
2a
A
51[d]
GP1
12
13
14
1l
1m
1n
Me
Me
À
2a
2a
2a
A
A
A
50
52
GP1
GP1
Me
H
ꢀ
ꢀ
ꢀ
ꢀ
(CH2)3
55[e]
28[f]
40[g]
GP1
GP1
GP1
GP1
À
À
H
(CH2)3
À
À
(CH2)4
15
16
17
1o
1p
1q
G
H
2a
2a
2a
A
B
B
À
A
À
H
(CH2)4
OMe
H
OMe
H
H
H
OMe
OMe
OMe
Cl
Br
Me
H
OMe
Br
H
H
H
H
H
H
Me
Me
H
H
OMe
H
H
16[h]
16
18
19
20
21
22
23
24
25
26
27
28
29
30
1r
1 s
1t
Me
Me
OMe
OMe
Me
Me
Me
Me
Me
Me
Me
Me
Me
H
Me
Me
Me
Me
H
2a
2a
2a
2a
2a
2a
2b
2c
2d
2e
2 f
2g
2b
B
B
B
B
B
B
A
A
A
A
A
A
A
GP1
GP1
GP1
GP1
GP1
GP1
GP2
GP2
GP1
GP2
GP1
GP1
1 (+64[i])
H
47
48
1u
1v
1w
1a
1a
1a
1a
1a
1a
1k
Me
Me
Me
H
H
H
H
H
H
H
52
H
Ph
16[j]
38
Me
Me
Me
Me
Me
Me
H
4-tBu-Ph
4-tol
4-F-Ph
4-OMe-Ph
CO2Me
nPr
4-tBu-Ph
4-tBu-Ph
47
62
14
10[k]
[l]
–
ꢀ
48[m]
GP2
Me
H
[a] The amounts of catalysts, additives and chemical yields are relative to alkyne 2. Alkyne was added to the reaction mixture within 10 h from a syringe
1
pump. The ratios of regioisomers were according to the H NMR spectra. [b] 3ca-a/3ca-b 56:44. [c] 10 mol% PdCAHTRE(UGN OAc)2 was used. [d] 3ka-a/3ka-b 64:36.
[e] 3na-a/3na-b > 95:5. [f] 3oa-a/3oa-b 75:25. [g] 3pa-a/3pa-b 45:55. [h] 3qa-a/3qa-b <5:95. [i] Additionally, 64% of 3aa was isolated. [j] 40% of 2a
was recovered. [k] Including 2% of hexamethyl benzenehexacarboxlate. [l] A complex mixture. [m] 3kb-a/3kb-b 87:13.
the tetraphenylbenzo plane in 3ea should be between 2.52
and 2.97 Š,[20] which is in the range of the standard mean
value for an interaction of the CH3–arene type.[21] The
degree of twisting of the tetraarylbenzo ring relates to the
strength of the CH3–p interaction, and it makes 3ea more
twisted than the other two examples. Besides the main con-
tribution from the steric repulsion, van der Waals attraction
is also a factor that leads to naphthalene core distortion
from the preferred geometry.
9, and this would be followed by the insertion of another
molecule of 2a to afford the arylbutadienylpalladium inter-
mediate 8. In a side reaction, aryl-1,2-diphenylethylene 10
could be formed by protonlysis/depalladation due to the
presence of acetic acid,[1c,3] but 10 was not observed as a by-
product. Intramolecular electrophilic palladation of 8 would
lead to palladabenzocycloheptatriene 4, which subsequently
would undergo reductive elimination to yield naphthalene
3aa. An alternative formation of the key intermediate 8
The formation of naphthalene 3aa most probably starts
with an electrophilic palladation of p-xylene (1a) to yield
the arylpalladium acetate 7 (route A in Scheme 1).[1c,22] syn-
could start with the reaction of PdACHTRE(UNG OAc)2 with two mole-
cules of alkyne 2a to give 1-palladacyclopentadiene 5 (route
B in Scheme 1).[23,24] Palladacycle 5 can produce hexasubsti-
tuted benzene 6 by insertion of another alkyne 2a, and re-
ductive elimination. However, because p-xylene (1a) is ap-
À
Addition of the Ar Pd bond in 7 to the triple bond of di-
phenylacetylene (2a) would yield the vinylpalladium species
Chem. Eur. J. 2008, 14, 6697 – 6703
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6699

Y.-T. Wu et al.
Table 3. Crystal data for compounds 3ea, 3ga, and 3ac.
plied in large excess with respect to alkyne 2a in this reac-
tion,[25] the 1-palladacyclopentadiene 5 has a better chance
to react with 1a and yields 4 or 8. The palladium(0) species
produced in the reduction/elimination is eventually reoxi-
3ea
3ga
3ac
formula
T [K]
C39H36
296(2)
C40H36
273(2)
C40H36
296(2)
crystal system
space group
a [Š]
b [Š]
c [Š]
triclinic
P1
monoclinic
P21/n
15.3046(4)
11.7211(3)
16.5363(6)
90
95.1640(10)
90
2954.35(13)
4
monoclinic
P21/n
12.2147(10)
10.8707(9)
24.577(2)
90
103.471(3)
90
3173.6(5)
4
dized by the additional silver acetate to generate PdACHTREUNG(OAc)2.
In addition, a control experiment suggested that route B is
more reasonable. When a reaction was carried out in the ab-
sence of p-xylene, 1,2,3,4-tetraphenyltriphenylene (11) was
isolated in 8% yield.[26] Compound 11 should be formed
from hexaphenylbenzene (6)[27] by cyclodehydrogenation.[28]
A small amount of 1,2,3,4-tetraphenylnaphthalene (3ba)
was obtained upon treatment of 1a with the alkyne 2a in
8.2578(18)
14.048(3)
14.451(3)
64.265(4)
86.469(4)
74.429(4)
1451.8(5)
2
a [8]
b [8]
g [8]
V [Š3]
Z
crystal size [mm3]
R-factor [%]
0.40”0.15”0.10 0.30”0.20”0.10 0.25”0.10”0.08
4.00
the presence of [PdCl
3ba in this reaction could only have been formed from 2a
and the triphenylphosphine in [PdCl2A(PPh3)2], the possibility
2ACHTERU(NG PPh3)2] (entry 3 in Table 1). Since
5.99
–
6.03
3.73
distance of sp3-C–p 3.58
interaction [Š]
CTHREUNG
of preparing 3ba directly from PPh3 was studied
end-to-end twist [8]:
overall naphthalene 23.9
tetraarylbenzo ring 13.1
(Scheme 2).[29–31] A limited survey of the reaction conditions
22.3
10.7
20.7
11.2
Scheme 2. Preparation of 1,2,3,4-tetraphenylnaphthalene (3ba) from tri-
phenylphosphine and diphenylacetylene (2a).
showed that the combinations of AgNO3, Cu
ACHTREU(NG OAc)2·H2O,
and Pd(OAc)2 gave 3ba in 43% yield. Finally, when PPh3
AHCTREUNG
and 2a were added slowly to the mentioned catalytic system
with a syringe pump, a satisfying result (58% yield) was ach-
ieved. The plausible reasons might be:
À
1) Pd
A
bonds.[32]
Figure 1. Intermolecular CH3–p interactions of 5-n-butyl-8-methyl-
1,2,3,4-tetraphenylnaphthalene (3ea).
2) Less triphenylphosphine oxide is formed.[33,34]
Interestingly,
Na2ACHTREUNG[PdCl6]·
4H2O provided 3ba in up to
62% yield, whereas [Pd(PPh3)4]
ACHTREUNG
did not afford the desired prod-
uct. Although the mechanism
of this reaction is not clear,
[AgACHTRE(UGN PPh3)n]NO3 (n=1 or 2)
could be an intermediate be-
cause AgNO3 has a superior re-
activity towards PPh3.[35] In our
catalytic system, heating [Ag-
AHCTRE(UNG PPh3)2]NO3 with alkyne 2a fur-
nished 3ba in 48% yield (based
on PPh3).[36] In addition, this is
the first example of a phenyl
group in PPh3 that serves as a
benzo moiety for the construc-
Scheme 1. Proposed mechanism for the formation of 3aa from alkyne 2a and p-xylene 1a.
6700
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Chem. Eur. J. 2008, 14, 6697 – 6703

Palladium-Catalyzed Synthesis of Napthalenes
FULL PAPER
À
(15); elemental analysis calcd (%) for C36H28 (460.6):C 93.87, H 6.13;
found:C 93.65, H 6.03; HRMS (EI) m/z:calcd for C 36H28:460.2191;
found:460.2192 [ M]+.
tion of a naphthalene core by one aryl C P bond cleavage
À
and one aryl C H bond activation.
Variation 2 (GP2): For an alkyne 2 (i.e., 2b, 2c, and 2d)with poor solu-
bility in CH3CN—5,8-dimethyl-1,2,3,4-tetraACHTREU(NG 4-tolyl)naphthalene (3ac):A
solution of alkyne 2c (311 mg, 1.51 mmol) in p-xylene (2 mL) was added
over 10 h with a syringe pump to a vigorously stirred suspension of
Conclusion
AgOAc (500 mg, 3.00 mmol) and PdACTHRE(UNG OAc)2 (25.6 mg, 0.11 mmol) in
A new and simple method for the preparation of oligosub-
stituted naphthalene derivatives in a one-pot operation from
internal alkynes and an arene or one molecule of triphenyl-
phosphine has been developed. Although the yields ob-
tained with these two protocols are not excellent, the sim-
plicity of the method provides a major advantage. Further
studies of photophysical properties of oligoaryl-substituted
naphthalenes 3,[37] and exploration of mechanistic and syn-
thetic aspects in the construction of complex aromatic com-
pounds are in progress.
CH3CN (2 mL) at 1108C under nitrogen. The mixture was kept at the
same temperature for an additional 26 h. After cooling to room tempera-
ture, filtration over Celite and concentration of the filtrate, the residue
was subjected to chromatography on SiO2 (hexane/CH2Cl2 from 10:1 to
6:1) to afford 3ac (182 mg, 47% (based on 2c)) as a pale yellow solid.
Colorless crystals were obtained by crystallization from CH2Cl2/MeOH.
M.p. 226–2278C; 1H NMR (300 MHz, CDCl3): d=1.83 (s, 6H), 2.07 (s,
6H), 2.24 (s, 6H), 6.52–6.61 (m, 8H), 6.85–6.93 (m, 8H), 7.04 ppm (s,
2H); 13C NMR (75.5 MHz, CDCl3, plus DEPT): d=21.0 (+), 21.2 (+),
25.1 (+), 126.9 (+), 127.5 (+), 129.4 (+), 131.1 (+), 131.6 (+), 133.2
(Cquat), 133.8 (Cquat), 134.0 (Cquat), 135.2 (Cquat), 137.9 (Cquat), 138.0 (Cquat),
139.5 (Cquat), 140.3 ppm (Cquat); MS (EI, 70 eV): m/z (%):516 (100) [ M]+
, 501 (25), 486 (10); elemental analysis calcd (%) for C40H36 (516.7):C
92.98, H 7.02; found:C 92.72, H 7.02.
Experimental Section
General information: 1H and 13C NMR spectra:Bruker 300 (300 and 75.5
MHz). MS:Bruker Daltonics Apex II30. X-ray crystal structure determi-
nation:The data were collected on a Stoe-Siemens-AED diffractometer.
Melting points were determined with a Büchi melting point apparatus
B545 and are uncorrected. Elemental analysis:Laboratory for elemental
analyses at National Cheng Kung University. Spectroscopic and analytical
data for new compounds, which are not mentioned in Experimental Sec-
tion, are presented as the Supporting Information.
Acknowledgements
This work was supported by the National Science Council of Taiwan
(NSC 96-2113M-006-008-MY2). We also thank Prof. S.-L. Wang and Ms.
C.-Y. Chen (National Tsing-Hua University, Taiwan) for the X-ray struc-
ture analyses. The authors are indebted to Prof. A. de Meijere (Univer-
sity of Gçttingen, Germany) for his useful suggestions and concerning
the final manuscript.
Preparation of1,2,3,4-Tetraphenylnaphthalene (3ba) rfom PPh
and
3
alkyne 2a:A solution of 2a (326 mg, 1.83 mmol) and PPh3 (160 mg,
0.61 mmol) in CH3CN (2.5 mL) was added over 10 h with a syringe pump
to a vigorously stirred mixture of AgNO3 (324 mg, 1.91 mmol), Cu-
ACHTREUNG(OAc)2·H2O (381 mg, 1.91 mmol), Na2PdCl6·4H2O (33.4 mg, 76.0 mmol),
pyridine (181 mg, 2.29 mmol), PPh3 (40.0 mg, 0.15 mmol) , and alkyne 2a
(82.0 mg, 0.46 mmol) in CH3CN (2 mL) at 1108C under nitrogen. The
suspension was kept at the same temperature for an additional 26 h.
After the reaction mixture had been cooled to room temperature, it was
filtered over Celite and the filtrate was concentrated. The residue was
subjected to chromatography on SiO2 (hexane/CH2Cl2 7:1 to 3:1) to
afford 3ba (205 mg, 62% (based on PPh3)) as a pale yellow solid. In ad-
dition, 133 mg of 2a was recovered. Colorless crystals could be obtained
by crystallization from CH2Cl2/MeOH. M.p. 203–2048C; the 1H NMR
spectrum was identical to that reported in the literature.[38]
À
[1] Reviews, see:a) Handbook of C H Transformations (Ed.:G.
Dyker), Wiley-VCH, Weinheim, 2005; b) C. Nevado, A. M. Echavar-
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1997, 97, 2879; e) F. Kakiuchi, S. Murai in Activation of Unreactive
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591.
General procedures for preparation of naphthalenes from an arene 1 and
an alkyne 2:
[2] B. M. Trost, Angew. Chem. 1995, 107, 285; Angew. Chem, Int. Ed.
Engl. 1995, 34, 259.
Variation 1 (GP1): For an alkyne 2 (i.e. 2a, 2d, 2 f, 2g and 2i)with good
solubility in CH3CN—5,7-dimethyl-1,2,3,4-tetraphenylnaphthalene (3ia):
A solution of alkyne 2a (270 mg, 1.51 mmol) in CH3CN (2 mL) was
added over 10 h with a syringe pump to a vigorously stirred suspension
[3] a) C. Jia, D. Piao, J. Oyamada, W. Lu, T. Kitamura, Y. Fujiwara, Sci-
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[5] T. Tsuchimoto, T. Maeda, E. Shirakawa, Y. Kawakami, Chem.
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[6] a) A. S. K. Hashmi, M. C. Blanco, E. Kurpejovic, W. Frey, J. W. Bats,
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[10] C. Nevado, A. M. Echavarren, Chem. Eur. J. 2005, 11, 3155.
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7516.
of AgOAc (500 mg, 3.00 mmol) and PdACHTRE(UNG OAc)2 (25.6 mg, 0.11 mmol) in
m-xylene (3i) (2 mL) at 1108C under nitrogen. The mixture was kept at
the same temperature for an additional 26 h. After the reaction mixture
had been cooled to room temperature, it was filtered over Celite and the
filtrate was concentrated. The residue was subjected to chromatography
on SiO2 (hexane/CH2Cl2 10:1 to 6:1) to afford 3ia (149 mg, 43% (based
on 2a)) as a pale yellow solid. Colorless crystals were obtained by crys-
tallization from CH2Cl2/MeOH. M.p. 254–2558C; 1H NMR (300 MHz,
CDCl3): d=1.92 (s, 3H), 2.31 (s, 3H), 6.71–6.83 (m, 10H), 7.05–7.30 ppm
(m, 12H); 13C NMR (75.5 MHz, CDCl3, plus DEPT): d=21.4 (+), 25.1
(+), 124.9 (+), 125.1 (+), 125.2 (+), 126.1 (+), 126.2”2 (+), 126.4 (+),
126.7 (+), 127.4 (+), 129.1 (Cquat), 131.1 (+), 131.3 (+), 131.4 (+), 131.6
(+), 132.7 (+), 133.6 (Cquat), 134.9 (Cquat), 135.6 (Cquat), 137.9 (Cquat),
138.4 (Cquat), 138.5 (Cquat), 139.5 (Cquat), 140.4 (Cquat), 140.8”2 (Cquat),
143.0 ppm (Cquat); MS (70 eV): m/z (%):460 (100) [ M]+, 194 (17), 176
Chem. Eur. J. 2008, 14, 6697 – 6703
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6701

Y.-T. Wu et al.
[12] a) B. M. Trost, F. D. Toste, J. Am. Chem. Soc. 1996, 118, 6305;
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[13] Although several synthetic routes to highly substituted naphthalenes
[22] a) M. Tani, S. Sakaguchi, Y. Ishii, J. Org. Chem. 2004, 69, 1221; b) C.
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thesis 1973, 524.
À
have been reported, none of them involve direct aryl C H bond ac-
tivations. For reactions of alkynes with triphenylchromium through
a benzochromacyclopentadiene intermediate, see:a) G. M. White-
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lics 1995, 14, 2091; for Pd-catalyzed reactions of aryl iodides and al-
kynes, see:d) S. Kawasaki, T. Satoh, M. Miura, M. Nomura, J. Org.
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tions of o-diiodobenzene and zirconacyclopentadienes, see:h) X.
Zhou, Z. Li, H. Wang, M. Kitamura, K.-i. Kanno, K. Nakajima, T.
Takahashi, J. Org. Chem. 2004, 69, 4559; i) T. Takahashi, Y. Li, P.
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Chem. Soc. 2002, 124, 576; j) T. Takahashi, R. Hara, Y. Nishihara,
M. Kotora, J. Am. Chem. Soc. 1996, 118, 5154; for the reaction of di-
[23] Several PdII catalysts have been found to produce hexasubstituted
benzenes, such as 6, by the [2+2+2] cyclotrimerzation of internal al-
kynes 2, with a palladacyclopentadiene of type 5 as a key intermedi-
ate, see:a) Y.-S. Fu, S. J. Yu, Angew. Chem. 2001, 113, 451; Angew.
Chem. Int. Ed. 2001, 40, 437; b) A. K. Jhingan, W. F. Maier, J. Org.
Chem. 1987, 52, 1161; c) K. Ogura, T. Aizawa, K. Uchiyama, H.
Iida, Bull. Chem. Soc. Jpn. 1983, 56, 953; it has been confirmed that
a PdII, not a Pd0, species is the reactive form for a [2+2+2] cycload-
dition, see:d) T. Yokota, Y. Sakurai, S. Sakaguchi, Y. Ishii, Tetrahe-
dron Lett. 1997, 38, 3923.
[24] An organopalladium(IV) intermediate similar to complex 5 has
been detected, see:a) R. van Belzen, H. Hoffmann, C. J. Elsevier,
Angew. Chem. 1997, 109, 1833; Angew. Chem. Int. Ed. Engl. 1997,
36, 1743; reviews for organopalladium(IV) complexes in organic
synthesis, see:b) C. J. Elsevier in Handbook of Organopalladium
Chemistry for Organic Synthesis (Eds.:E. Negishi, A. de Meijere),
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83.
phenylethyne and benzoyl chloride in the presence of [IrClACHTRE(UNG cod)]2
(cod=1,5-cyclooctadiene), see:k) T. Yasukawa, T. Satoh, M. Miura,
M. Nomura, J. Am. Chem. Soc. 2002, 124, 12680; for Pd-catalyzed
co-cyclizations of benzyne with alkynes, see:l) D. PeÇa, D. PØrez, E.
Guitiµn, L. Castedo, J. Org. Chem. 2000, 65, 6944; m) E. Yoshikawa,
K. V. Radhakrishnan, Y. Yamamoto, J. Am. Chem. Soc. 2000, 122,
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Angew. Chem. 1998, 110, 2804; Angew. Chem. Int. Ed. 1998, 37,
2659.
[25] p-Xylene (2 mL; 16.2 mmol) is used in large excess with respect to
2a (1.5 mmol) in these reactions.
[26] Compound 11 has been previously characterized as a twisted mole-
cule, see:R. A. Pascal, Jr., D. van Engen, B. Kahr, W. D. McMillan,
J. Org. Chem. 1988, 53, 1687.
[14] Acetoxystilbene and/or its hydrolysis product deoxybenzoin were
obtained in some cases. The former compound should be formed
from 1,2-diphenylethyne (2a) by the hydroacetoxylation. For exam-
ples of metal-catalyzed/mediated hydroacetoxylation of alkynes, see:
a) N. Menashe, Y. Shvo, J. Org. Chem. 1993, 58, 7434; b) S. Uemura,
H. Miyoshi, M. Okano, J. Chem. Soc. Perkin Trans. 1 1980, 1098.
[15] A monitored experiment indicated that naphthalene 3aa was not
generated from 3 sa by Pd-catalyzed debromination.
[16] a) See ref. [13h] and references therein. For a recent review, see:
b) R. A. Pascal, Jr., Chem. Rev. 2006, 106, 4809.
[17] The end-to-end twist of compound 3ea (23.98) is very close to that
of perchloronaphthalene (248), see:F. H. Herbstein, Acta Crystal-
logr. Sect. B 1979, 35, 1661.
[18] CCDC-668637 (3ea), 648605 (3ga), and 671871 (3ac) contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[19] p-tert-Butylcalix[4]arene/toluene:a) G. D. Andreetti, R. Ungaro and
A. Pochini, J. Chem. Soc. Chem. Commun. 1979, 1005; p-1,1,3,3-tet-
ramethylbutylcalix[4]-arene/toluene:b) G. D. Andreetti, A. Pochini
and R. Ungaro, J. Chem. Soc. Perkin Trans. 2 1983, 1773. p-tert-bu-
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li, A. Arduini, E. Ghidini, A. Pochini and R. Ungaro, J. Incl.
Phenom. 1987, 5, 123.
[27] Traces of hexamethyl benzenehexacarboxylate were also isolated
(entry 28 in Table 2).
[28] In the presence of Lewis acids, hexaarylbenzenes undergo oxidative
intramolecular cyclodehydrogenation to form hexa-peri-hexabenzo-
coronenes. For reviews, see:a) M. D. Watson, A. Fechtenkçtter, K.
Müllen, Chem. Rev. 2001, 101, 1267; b) J. Wu, W. Pisula, K. Müllen,
Chem. Rev. 2007, 107, 718.
[29] According to the Aldrich catalogue (USA, 2007–2008), triphenyl-
phosphine (USD 35.1/mol) (USD=US dollars)is less expensive than
iodobenzene (USD 49.8/mol) and o-diiodobenzene (USD 4719/
mol). The last two compounds have been used for the preparation
of 3ba, see ref. [13].
À
[30] For metal-mediated or -catalyzed C P bond cleavage of organo-
phosphorus species, see:a) V. V. Grushin, Organometallics 2000, 19,
1888; b) X.-M. Zhang, A. J. Fry, F. G. Bordwell, J. Org. Chem. 1996,
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[20] X-ray crystallography tends to underestimate the conformation of
[31] For Pd0-catalyzed reactions of quaternary phosphonium halides with
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À
the methyl group. If the methyl C H bond length and the bond
angle aCCH is assumed to be 1.07 Š and 109.58, respectively, then
the distance of methyl hydrogen atom to the tetraphenylbenzo
plane is approximately between 2.52 and 2.97 Š.
[21] The standard mean value of the distance for the CH3–planar arene
interaction is 2.75Æ0.1 Š, see:a) O. Takahashi, Y. Kohno, S. Iwasa-
ki, K. Saito, M. Iwaoka, S. Tomoda, Y. Umezawa, S. Tsuboyama, M.
Nishio, Bull. Chem. Soc. Jpn. 2001, 74, 2421. The standard mean
value of the distance for the sp3-CH–fullerene interaction is 2.87Æ
0.13 Š, see:b) H. Suezawa, T. Yoshida, S. Ishihara, Y. Umezawa, M.
Nishio, CrystEngComm, 2003, 5, 514; for a review of a crystallo-
[32] K. Kikukawa, T. Matsuda, J. Organomet. Chem. 1982, 235, 243.
(OAc)2 with an excess of PPh3 can generate Pd0 spe-
[33] Reaction of PdACHTREUNG
cies and triphenylphosphine oxide, see:C. Amatore, E. Carre, A.
Jutand, M. A. MꢂBarki, Organometallics 1995, 14, 1818.
[34] Triphenylphosphine oxide cannot generate 3ba.
6702
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Chem. Eur. J. 2008, 14, 6697 – 6703

Palladium-Catalyzed Synthesis of Napthalenes
FULL PAPER
[35] Reaction of PPh3 with AgNO3 in CH3CN at room temperature gave
[37] A preliminary study indicated that naphthalene 3ia displays aggre-
gation-induced emission (M. Y. Kuo, Y. T. Wu unpublished results).
[38] T. Kitamura, M. Yamane, K. Inoue, M. Todaka, N. Fukatsu, Z.
Meng, Y. Fujiwara, J. Am. Chem. Soc. 1999, 121, 11674.
a mixture of [AgACHTREUNG(PPh3)2]NO3 and [AgCAHTRE(UGN PPh3)NO3] within 10 min in
> 90% yield.
[36] Reaction of [Ag
ACHTREUNG
Cu(OAc)2·H2O (2 equiv), Na CHTREUNG
N
(1.2 equiv), and pyridine (2.4 equiv) in CH3CN at 1108C for 36 h
gave 3ba in 48% yield (based on PPh3; 96% yield based on [Ag-
A
Received:March 24, 2008
can also be isolated.
Published online:June 12, 2008
Chem. Eur. J. 2008, 14, 6697 – 6703
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6703