Iridium-catalyzed reaction of aroyl chlorides with internal alkynes to produce substituted naphthalenes and anthracenes

Article abstract of DOI:10.1021/ja0280269

Benzoyl chlorides efficiently react with 2 equiv of dialkylacetylenes as well as diphenylacetylene in the presence of an iridium catalyst accompanied by decarbonylation to produce 1,2,3,4-tetrasubstituted naphthalenes in good yields. Use of 2-naphthoyl ch

Full text of DOI:10.1021/ja0280269

Published on Web 10/05/2002
Iridium-Catalyzed Reaction of Aroyl Chlorides with Internal Alkynes to
Produce Substituted Naphthalenes and Anthracenes
Toshiya Yasukawa, Tetsuya Satoh, Masahiro Miura,* and Masakatsu Nomura
Department of Applied Chemistry, Faculty of Engineering, Osaka UniVersity, Suita, Osaka 565-0871, Japan
Received August 6, 2002
Selective synthesis of substituted polycyclic aromatic hydro-
carbons has become increasingly important, because they have been
finding increasing application as π-conjugated functional materi-
Scheme 1
Scheme 2
1,2
als. Among modern potential strategies to prepare condensed
aromatics is the metal-promoted or -catalyzed homologation, such
as benzene to naphthalene and the latter to anthracene, of a given
3-6
aromatic substrate with two alkyne molecules (Scheme 1). Using
dialkylacetylenes may produce the corresponding homologated
aromatics having substantial solubilities. Recently, Takahashi et al.
have described an effective copper-promoted method for the
coupling of 1,2-dihalobenzenes and 1,2,4,5-tetrahalobenzenes with
zirconacyclopentadienes prepared using dialkylacetylenes to produce
polyalkylated naphthalenes and anthracenes.3 The palladium-
catalyzed 1:2 coupling of aryl halides with alkynes is a method for
Scheme 1 using more readily available monofunctionalized aromatic
a,b
Table 1. Iridium-Catalyzed Reaction of Benzoyl Chloride (1a) with
4
-Octyne (2a)a
6
a
substrates. In this case, acetylenedicarboxylates and diphenyl-
acetylene6b can be employed to afford the corresponding naphtha-
lenes with moderate yields, but use of dialkylacetylenes gives
6b
nonfused 1:3 coupling products as the major ones.
Meanwhile, we previously demonstrated that benzoyl chlorides
react with dialkylacetylenes in the presence of a rhodium catalyst
to give 2,3-disubstituted indenones as the predominant products
entry
L
time (h)
% yield of 3ab
1
2
PPh3
PPh3
P(t-Bu)3
P(t-Bu)3
18
24
15
25
19
71
46
98
87
c
along with small amounts of 1,2,3,4-tetrasubstituted naphthalenes
3
4
7
d
(
Scheme 2). We now report our new findings that the naphthalenes
can be produced exclusively by the reaction using iridium in place
of rhodium. This is the first efficient example of transition-metal-
catalyzed aromatic homologation using aliphatic alkynes and
appears to provide a simple, straightforward method for preparing
polyalkyl-substituted condensed aromatics.
5
99 (93)
a
Reaction conditions: 1a (1 mmol), 2a (3 mmol), [IrCl(cod)]2 (0.01
mmol), L (0.04 mmol), in refluxing o-xylene. b GLC yield based on amount
c
of 1a used. Value in parentheses indicates isolated yield. Na2CO3 (2 mmol)
was added. d CaCO3 (2 mmol) was added.
When benzoyl chloride (1a) (1 mmol) was treated with 4-octyne
(
(
2a) (3 mmol) in the presence of [IrCl(cod)]
0.04 mmol) in refluxing o-xylene for 18 h, 1,2,3,4-tetrapropyl-
2
(0.01 mmol) and PPh
3
3). Treatment of 1a with 1-octyne, however, gave a complex
mixture.
naphthalene (3a) was formed in 71% yield (entry 1 in Table 1). In
A plausible mechanism for the reaction of aroyl chloride 1 with
alkyne 2 is illustrated in Scheme 4, in which neutral ligands are
omitted. Oxidative addition of 1 to chloroiridium(I) species
generates aroyliridium(III) A, which undergoes decarbonylation to
7
contrast to the indenone synthesis using rhodium, addition of
8
Na
2
CO
3
as base retarded the reaction (entry 2). Use of a bulky
ligand, P(t-Bu)
3
9
, was found to afford an almost quantitative yield
10
of 3a (entry 3). It was somewhat surprising that the reaction also
give aryliridium(III) B. Insertion of 2 then gives vinyliridium C.
proceeded efficiently in the absence of any phosphine ligand (entry
The subsequent ortho-iridation affords five-membered iridacycle
D. Further insertion of 2 and reductive elimination affords products
3-6, regenerating chloroiridium(I). It should be noted that in the
5). However, this phosphine-free protocol was not always effective
as described below.
Table 2 summarizes the results for the reactions of various 4- or
7
corresponding rhodium catalysis, CO coordinated to the metal
2
-substituted benzoyl chlorides 1a-h with dialkylacetylenes 2a-c
and diphenylacetylene 2d using [IrCl(cod)] in the presence or
absence of P(t-Bu) . In each reaction, the corresponding naphthalene
participates in the reaction to give indenones. In contrast, in the
present reaction, the second alkyne insertion should be faster than
that of CO. This represents a remarkable difference of catalytic
nature between the metals.
2
3
could be obtained, while the yields were affected by existence of
the ligand and identity of the substituents. It is worth noting that
the relatively labile C-halogen bonds were tolerable under the
conditions. The reaction of 2-thenoyl chloride (7) in place of 1
with 2a also proceeded smoothly to give benzothiophene 8 (Scheme
To confirm the reaction sequence, an aryliridium(III) complex,
4-t-BuC
of 1c with Vaska’s complex according to the literature method.
t-Bu-B (0.02 mmol) could efficiently catalyze the reaction of 1c
1 mmol) with 2a (3 mmol) for 20 h to afford 3c in 92% yield.
t-Bu-B was also treated with 1 equiv of 2a in CDCl in a sealed
6 4 2 3 2
H -IrCl (CO)(PPh ) (t-Bu-B), was prepared by the reaction
1
0
(
*
To whom correspondence should be addressed. E-mail: miura@
chem.eng.osaka-u.ac.jp.
3
1
2680 J. AM. CHEM. SOC. 2002, 124, 12680-12681
9
10.1021/ja0280269 CCC: $22.00 © 2002 American Chemical Society

C O MMU N I C A T I O N S
Table 2. Preparation of Naphthalenes by the Reaction of Aroyl
Chlorides with Internal Alkynes
Table 3. Reaction of 2-Naphthoyl Chlorides with Internal Alkynesa
a
entry
chloride 1, X, Y
alkyne 2, R
time (h)
product, % yieldb
chloride
9, X
alkyne
2, R
total
yield (%)
b
product ratioc
1
2
1b, Me, H
1b, Me, H
1c, t-Bu, H
1d, OMe, H
1e, H, OMe
1f, Cl, H
1f, Cl, H
1g, Br, H
1h, I, H
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2b, n-Bu
2c, i-pentyl
2d, Ph
25
25
16
25
25
25
25
18
16
16
16
25
3b, 91 (97)
3b, (68)
3c, 96
3d, 50
3e, 35
3f, 67 (70)
3f, (56)
3g, 69
3h, 63
4, 79
entry
L
c
1
2
3
9a, H
9a, H
9a, H
9a, H
9a, H
2a, n-Pr
2a, n-Pr
2a, n-Pr
2a, n-Pr
2c, i-pentyl
70
73
67
83
93
80
10:13 ) 74:26
10:13 ) 70:30
10:13 ) 90:10
10:13 ) 96:4
11:14 ) 98:2
12:15 ) 97:3
3
4
5
P(t-Bu)3
PPh3
PPh3
PPh3
PPh3
d
d
4
6
7
d
5
c
d
6
9b, OMe 2a, n-Pr
8
9
a
Reaction conditions: 9 (1 mmol), 2 (3 mmol), [IrCl(cod)]2 (0.01 mmol),
10
11
12
1a, H, H
1a, H, H
1a, H, H
b
L (0.04 mmol), in refluxing o-xylene. Isolated yield based on amount of
5, 80
6, 70
used. c Determined by GLC or H NMR. PPh3 (0.06 mmol) was used.
1
d
9
a
Reaction conditions: 1 (1 mmol), 2 (3 mmol), [IrCl(cod)]2 (0.01 mmol),
Acknowledgment. This work was supported by a Grant-in-Aid
b
P(t-Bu)3 (0.04 mmol), in refluxing o-xylene. Isolated yield based on
amount of 1 used. Value in parentheses indicates GLC yield. Without
ligand. CaCO3 (2 mmol) was added.
c
from the Ministry of Education, Culture, Sports, Science, and
Technology, Japan, and the Frontier Research Center of Osaka
University. We thank Ms. Y. Miyaji for the measurement of NMR
spectra.
d
Scheme 3
Scheme 4
Supporting Information Available: Standard experimental pro-
cedure and characterization data for new compounds (PDF). This
material is available free of charge via the Internet at http://pubs.acs.org.
References
(
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(
tube at 150 °C. 1H and 31P NMR of the solution indicated that
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3
Castedo, L. Angew. Chem., Int. Ed. 1998, 37, 2659. (b) Pe n˜ a, D.; P e´ rez,
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0
7280.
relatively faster than the first one. In an alternative sequence, B
may undergo successive insertion of two molecules of 2 and the
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iridacycle. Participation of this route cannot be excluded. Anyway,
the efficacy of cyclization seems to be due to the smooth ortho-
iridation and the lack of â-elimination to produce arylallenes.4
We also attempted to control the direction of homologation using
(
(
5) X ) CrPh , Y ) H: (a) Whitesides, G. M.; Ehmann, W. J. J. Am. Chem.
2
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(
8) The reaction of 1a (3 mmol) with 2a (2 mmol) using [IrCl(cod)]
2
(0.02
3
(2 mmol) for 24 h also gave 3a
mmol), PPh (0.04 mmol), and Na CO
3
2
2-naphthoyl chlorides 9 (Table 3). The reaction of 2-naphthoyl
(52% based on 2a), with no indenone being detected. In contrast, the
indenone (25%) was formed along with 3a (6%) under the conditions
chloride (9a) with 2a proceeded without any phosphine ligand to
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employed for entry 2 in Table 1 using [RhCl(cod)]
(cod)]2.
2
in place of [IrCl-
(
9) We reported that the catalyst system is also effective for the cross-coupling
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total yield being 70%. Addition of P(t-Bu)
reaction. Fortunately, it was found that use of PPh
3
only little affected the
(0.06 mmol)
3
improved both the yield and the selectivity of 10 up to 83 and 96%,
respectively. Anthracene 10 could be purified easily due to its good
solubility. The catalyst system was also applicable to the reactions
of 9a with 2c and 6-methoxy-2-naphthoyl chloride (9b) with 2a to
produce tetraalkylanthracenes 11 and 12 with high yields and
selectivities.
In summary, we have developed a new, useful method for
aromatic homologation with two aliphatic alkyne molecules using
an iridium catalyst, giving condensed aromatics with substantial
solubilities. The reaction proceeds efficiently without causing
(
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(
31
3 3 2 3
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(-11.7 ppm) and the trichloride (-17.7 ppm) were detected after the
treatment. It is known that Vaska’s complex reacts with polychlorinated
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S. D. J. Chem. Soc., Dalton Trans. 1985, 2113. (b) Al-Najjar, I. M. Inorg.
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(
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â-elimination4 and excessive insertion of alkyne. The tolerance
c
6b
12
of C-halogen bonds under the iridium catalysis enables various
catalytic derivatizations of the products.13
JA0280269
J. AM. CHEM. SOC.
9
VOL. 124, NO. 43, 2002 12681