Rhodium-catalyzed dimerization of diaryl acetylenes in the presence of grignard reagents: Synthesis of 1,2,3-triphenyl naphthalene derivatives

Article abstract of DOI:10.1080/00397911.2011.580444

An efficient Rh-catalyzed dimerization of diaryl acetylenes was achieved in the presence of Wilkinson catalyst, AgF2, and 1.5 equivalent of PhMgBr in toluene, providing the 1,2,3-triaryl naphthalene derivatives in moderate to good yields. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.

Full text of DOI:10.1080/00397911.2011.580444

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Rhodium-Catalyzed Dimerization of
Diaryl Acetylenes in the Presence of
Grignard Reagents: Synthesis of 1,2,3-
Triphenyl Naphthalene Derivatives
Pengcheng Qian a , Fan Chen a & Changduo Pan b
a College of Chemistry and Materials Engineering, Wenzhou
University, Wenzhou, China
b Wenzhou Institute of Industry and Science, Wenzhou, China
Version of record first published: 17 Aug 2012.
To cite this article: Pengcheng Qian, Fan Chen & Changduo Pan (2012): Rhodium-Catalyzed
Dimerization of Diaryl Acetylenes in the Presence of Grignard Reagents: Synthesis of 1,2,3-
Triphenyl Naphthalene Derivatives, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 42:21, 3242-3250
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Synthetic Communications1, 42: 3242–3250, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.580444
RHODIUM-CATALYZED DIMERIZATION OF DIARYL
ACETYLENES IN THE PRESENCE OF GRIGNARD
REAGENTS: SYNTHESIS OF 1,2,3-TRIPHENYL
NAPHTHALENE DERIVATIVES
Pengcheng Qian,1 Fan Chen,1 and Changduo Pan2
1College of Chemistry and Materials Engineering, Wenzhou University,
Wenzhou, China
2Wenzhou Institute of Industry and Science, Wenzhou, China
GRAPHICAL ABSTRACT
Abstract An efficient Rh-catalyzed dimerization of diaryl acetylenes was achieved in the
presence of Wilkinson catalyst, AgF2, and 1.5 equivalent of PhMgBr in toluene, providing
the 1,2,3-triaryl naphthalene derivatives in moderate to good yields.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Synthetic Communications to view the free supplemental file.
Keywords Diaryl acetylenes; dimerization; Grignard reagents; rhodium-catalyzed;
1,2,3-triaryl naphthalene
INTRODUCTION
In the past few years, much attention has been paid to rhodium catalysts in the
formation of carbon–carbon bonds because the construction of carbon–carbon
bonds is a central theme of research in organic synthesis.[1] Selective synthesis of sub-
stituted polycyclic aromatic hydrocarbons has become more important because of
increasing application as conjugated functional materials.[2]
In recent years, the rhodium-catalyzed hydroarylation of alkynes has
received much attention.[3] Recently, Zhang et al. developed a phosphine-free
Received November 21, 2010.
Address correspondence to Fan Chen, College of Chemistry and Materials Engineering, Wenzhou
University, Wenzhou 325027, China. E-mail: fanchen@wzu.edu.cn or Changduo Pan, Wenzhou Institute
of Industry and Science, Wenzhou 325000, China. E-mail: changduo@yahoo.cn
3242

1,2,3-TRIPHENYL NAPHTHALENE DERIVATIVES
3243
rhodium-catalyzed hydroarylation of alkynes with arylboronic acids, providing the
triaryl ethenes in good to excellent yields.[4] Subsequently, Lin et al. reported rho-
dium–copper–TBAF-catalyzed hydroarylation of symmetrical and asymmetrical
alkynes with aryl trimethoxysilanes.[5] Based on the aforementioned works, we envi-
sioned the possibility of using cheap and abundant Grignard reagents with alkynes
to access hydroarylation products (Scheme 1).
Initial studies of the reaction conditions were conducted by using the reaction of
PhMgBr (0.3 mmol) with diphenyl acetylene 1a (0.2 mmol) in the presence of Wilkin-
son catalyst (5 mol%) in toluene (3 mL) as the model reaction. To our surprise, it was
not the arylmagnesiation of diphenylacetylene but the dimerization that occurred,
and the dimerization product 1,2,3-triphenyl naphthalene 2a was formed in 20% yield
(Scheme 1). The structure of compounds 2a was identified by 1H NMR and 13C NMR
and unambiguously confirmed by single-crystal X-ray diffraction analysis (Figure 1).
Particularly, only some limited methods existed for the preparation of 1,2,3-tri-
phenyl naphthalene. In 1928, Schlenk and Bergmann first reported the synthesis of
1,2,3-triphenyl naphthalene.[6] Subsequently, Bergmann et al. described a modified
methodology to access 1,2,3-triphenyl naphthalene.[7] Recently, Goettmann et al.
Thomas described mesoporous graphitic carbon nitride as a versatile, metal-free
catalyst for the cyclolization of alkynes, producing the 1,2,3-triphenyl naphthalene
in quantitative yield.[8] However, among the aforementioned studies, only diphenyl
acetylene was reported as the substrate, and the reaction of the derivatives of
diphenyl acetylene was not studied. In 1998, Huang et al. reported
a
rhodium-catalyzed cyclodimerization of arylalkynes for the synthesis of naphthalene
derivatives in the presence of HCl.[9] However, the reaction was conducted under
strong acidic conditions. Recently, Sakabe et al. developed an efficient rhodium=
phosphine=amine ꢀ HBr catalyst system for highly selective cross-cyclodimerization
as well as homodimerization of diarylacetylenes, leading to the multisubstituted
naphthalenes (T ¼ 160 ꢁC).[10] Herein, we report a Rh-catalyzed dimerization reac-
tion of diaryl acetylene in the presence of Grignard reagent and an additive, provid-
ing 1,2,3-triaryl naphthalene derivatives in moderate to excellent yields. This
methodology would be a complemental method to that of Huang et al.
Encouraged by these results, we tested some other parameters such as rhodium
source, oxidant, and additive in the reaction, as shown in Table 1. During the screen-
ing process, the Wilkinson catalyst was the best. Rh(CO)2(acac), Rh(cod)(acac), and
Scheme 1. Rhodium-catalyzed reaction of alkynes with ArMgBr.

3244
P. QIAN, F. CHEN, AND C. PAN
Figure 1. ORTEP diagram of the single-crystal X-ray structure of compound 2a.
[Rh(cod)2Cl]2 were totally ineffective in the procedure (Table 1, entries 3–5).
Pd(OAc)2, PdCl2, and Ni(dppe)Cl2 inhibited the reaction (Table 1, entries 6–8).
The oxidant was also crucial in this transformation. For example, the yields would
increase to 55%, 62%, and 85% in the presence of CuO, CuF2, and CuCl2, respect-
ively (Table 1, entries 9, 12, and 11). However, the addition of CuCN gave only a
trace of product. Among the oxidants screened, Cu(OTf)2 and AgF2 were the best,
and the yields would dramatically increased to 92% in both cases (Table 1, entries 13
and 14). Finally, we tested some other additives in the reaction. Surprisingly, only
Grignard reagent was the proper one in the procedure, and other bases were totally
ineffective in the reaction.
With the optimized conditions in hand, we then explored the scope of the
dimerization reaction, as shown in Table 2. All the substrates ran smoothly in the pro-
cedure and produced the products in moderate to excellent yields. Both the electronic
effect and hindrance on the substrates somewhat influenced the reaction. For example,
2c and 2d were obtained in only 63% and 45% yields, respectively (Table 2, entries 3
and 4). Having demonstrated the utility of dimerization reaction conditions on a num-
ber of symmetrical 4,40-disubstituted aryl alkynes, we chose to test the generality of the
addition to 3,30-disubstituent aryl alkynes. As expected, the reaction proceeded
smoothly, providing the products in good yields, whereas the regioselectivity was
poor. For example, 72% of 2f and 91% of 2 g were isolated with 5:4 and 3:2 regioselec-
tivity, respectively (Table 2, entries 6 and 7). It was noteworthy that 1e
[R ¼ 4-(1,3-dioxolanyl)] was not compatible under Huang et al.’s procedure.[9] How-
ever, it ran smoothly under our procedure, albeit the yield was poor (Table 2, entry 5).
The rhodium-catalyzed dimerization reaction of d10-diphenyl acetylene 1a0 was
conducted. After the completion of the reaction, D2O was added to quench the

1,2,3-TRIPHENYL NAPHTHALENE DERIVATIVES
3245
Table 1. Screening for the optimum conditionsa
Entry
Catalyst
Additive
Oxidant
no
no
Yield (%)b
1
2
RhCl(PPh3)3
RhCl3 ꢀ 3H2O
[Rh(cod)2Cl]2
Rh(CO)2(acac)
Rh(cod)(acac)
PdCl2
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
PhMgBr
4-TolMgBr
n-BuMgCl
n-BuLi
20
11
3
no
no
<5
<5
<5
<5
<5
<5
55
4
5
no
no
6
7
Pd(OAc)2
no
no
8
NiCl2(dppe)2
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
RhCl(PPh3)3
9
CuO
CuCN
CuCl2
CuF2
Cu(OTf)2
AgF2
AgF2
AgF2
AgF2
AgF2
AgF2
10
11
12
13
14
15
16
17
18
19
<5
82
65
92
92
91
<5
<5
<5
<5
NaH
t-BuOK
aAll reactions were run with diphenyl acetylene (0.2 mmol), PhMgBr (0.6 mL of 0.5 M in THF,
0.3 mmol) or additive (0.3 mmol), catalyst (5 mol %), and oxidant (0.2 mmol) in dry toluene (3 mL) under
N2, 110 ꢁC, 12 h.
bIsolated yield.
reaction, and 2a0 was isolated in 86% yield (Scheme 2). This result clearly showed
that the H atom attached in the naphthalene was not derived from the exterior of
the reaction system during the workup. Next, d8-toluene was subjected to the stan-
dard reaction conditions. The 4-H of product 2a0 did not come from d8-toluene as
1
determined by H NMR. However, the mechanism in detail is still unclear.
In conclusion, we have developed an efficient rhodium-catalyzed dimerization
of diaryl acetylene that was achieved in the presence of 1.5 equivalent of PhMgBr
and 1 equivalent of AgF2, providing the 1,2,3-triaryl naphthalene derivatives
in moderate to good yields. This mechanism study is currently ongoing in our
laboratory.
EXPERIMENTAL
Chemicals were either purchased or purified by standard techniques without
special instructions. 1H NMR and 13C NMR spectra were measured on a
300-MHz spectrometer (1H 300 MHz, 13C 75 MHz), using CDCl3 as the solvent with

3246
P. QIAN, F. CHEN, AND C. PAN
Table 2. Dimerization of diaryl acetylenesa
Yield
(%)b
Entry
Substrate 1
Product 2
1
92
2
80c
3
63
4
45
5
31
(Continued )

1,2,3-TRIPHENYL NAPHTHALENE DERIVATIVES
3247
Table 2. Continued
Yield
(%)b
Entry
Substrate 1
Product 2
6
72 (5:4)d
7
91 (3:2)d
aReaction conditions: diaryl acetylene (0.2 mmol), PhMgBr (0.6 mL of 0.5 M in THF,
0.3 mmol),Rh(PPh3)3Cl (5 mol%), and AgF2 (0.2 mmol) in dry toluene (3 mL) under N2, 110 ꢁC, 12 h.
bIsolated yield.
c4-TolMgBr (0.4 mL of 1.0 M in THF) was employed.
dThe rations of the two isomers (in parentheses) were determined by 1H NMR.
tetramethylsilane (TMS) as the internal standard at room temperature. Chemical
shifts (d) are given in parts per million (ppm) relative to TMS, and the coupling
constants (J) are given in hertz (Hz).
General Procedure
Under N2, a reaction tube was charged with diaryl alkynes (0.2 mmol), phenyl-
magnesium bromide (ca. 0.3 mmol), or p-tolylmagnesium bromide (ca. 0.4 mmol),
RhCl(PPh3)3 (9.3 mg, 5 mol%), AgF2(0.2 mmol), and dry toluene (3 mL). The mix-
ture was heated under N2 at 110 ꢁC for 12 h and then cooled to room temperature.
The mixture was concentrated in vacuum, and the residue was purified by flash col-
umn chromatography on silica gel to give the product.
Scheme 2. Labeling study.

3248
P. QIAN, F. CHEN, AND C. PAN
Characterization Data of All Products
1,2,3-Triphenylnaphthalene (2a)[8] 1H NMR (CDCl3, 300 MHz):
.
d
7.95–7.94 (m, 2H), 7.93–7.52 (m, 2H), 7.49–7.40 (m, 1H), 7.25–7.14 (m, 10H),
6.95–6.92 (m, 3H), 6.87–6.84 (m, 2H). 13C NMR (CDCl3, 75 MHz): d 142.0,
140.0, 139.9, 139.4, 132.7, 131.5, 131.2, 130.0, 128.7, 127.9, 127.5, 126.9, 126.9,
126.4, 126.2, 126.1, 126.1, 125.6.
7-Methyl-1,2,3-trip-tolylnaphthalene (2b)[9] 1H NMR (CDCl3, 300 MHz):
.
d 7.83–7.78 (m, 2H), 7.32–7.30 (m, 2H), 7.06–6.95 (m, 8H), 6.74–6.73 (m, 4H), 2.39
(s, 3H), 2.33 (s, 3H), 2.28 (s, 3H), 2.16 (s, 3H). 13C NMR (CDCl3, 75 MHz): d 139.6,
139.2, 138.4, 137.5, 136.8. 135.7, 135.7, 134.9, 132.5, 131.5, 131.3, 131.1, 130.1, 128.6,
128.4, 128.3, 127.9, 127.7, 125.9, 22.2, 21.5, 21.3.
7-Methoxy-1,2,3-tris(4-methoxyphenyl)naphthalene (2c)[9] 1H NMR
.
(CDCl3, 300 MHz) d 7.82–7.79 (m, 2H), 7.17–7.14 (m, 1H), 7.07–7.03 (m, 4H),
6.89–6.88 (m, 1H), 6.81–6.70 (m, 6H), 6.52–6.50 (m, 2H), 3.80 (s, 3H), 3.77 (s,
3H), 3.70 (s, 3H), 3.68 (s, 3H). 13C NMR (CDCl3, 75 MHz) d 157.8, 157.6, 157.2,
138.5, 137.5, 134.8, 133.4, 132.8, 132.5, 132.1, 132.0, 131.0, 129.3, 128.3, 128.2,
118.3, 113.1, 113.0, 112.4, 105.5, 55.1, 55.1, 54.9.
1,2,3-Tris(3,5-dimethylphenyl)-6,8-dimethylnaphthalene (2d). 1H NMR
(CDCl3, 300 MHz): d 7.76 (s, 1H), 7.54 (s, 1H), 7.06 (s, 1H), 6.78–6.70 (m, 6H),
6.47 (s, 1H), 6.41 (s, 2H), 2.46 (s, 3H), 2.16 (s, 6H), 2.15 (s, 6H), 1.93 (s, 6H), 1.54
(s, 3H). 13C NMR (CDCl3, 75 MHz): d 142.5, 142.0, 140.1, 139.3, 136.3, 135.8,
135.5, 135.0,134.7, 32.3, 129.6, 129.6, 128.5, 127.9, 127.5, 127.2, 126.4, 126.3, 29.7,
24.8, 21.1, 21.1, 20.9. IR (KBr, cmꢂ1): 3016, 2920, 2854, 1646, 1600, 909. MS
(EI): m=z 468 (M)þ. Anal. calcd. for C36H36: C, 92.26; H, 7.74. Found: C, 92.12;
H, 7.49.
2,2’,2’’-(4,4’,4’’-(7-(1,3-Dioxolan-2-yl)naphthalene-1,2,3-triyl)tris(benzene-
4,1-diyl)) tris(1,3-dioxolane) (2e). 1H NMR (CDCl3, 300 MHz): d 7.97–7.89 (m,
2H), 7.66–7.59 (m, 2H), 7.37–7.30 (m, 4H), 7.18–7.13 (m, 4H), 7.05 (d, J ¼ 8.1 Hz,
2H), 6.86 (d, J ¼ 7.5 Hz, 2H), 5.87 (s, 1H), 5.75 (s, 1H), 5.75 (s, 1H), 5.64 (s, 1H),
4.17–3.94 (m, 16H). 13C NMR (CDCl3, 75 MHz): d 142.7, 140.5, 139.9, 139.9,
139.2, 137.8, 136.0, 135.5, 133.2, 132.1, 132.0, 131.4, 131.2, 130.0, 129.0, 128.6,
128.5, 125.8, 125.3, 123.9, 104.2, 103.7, 103.6, 103.5, 65.4, 65.2, 65.2, 64.9. IR
(KBr, cmꢂ1): 2920, 2852, 1698, 1649, 1514, 1460, 1081, 912. MS (EI): m=z 644
(M)þ, Anal. calcd. for C40H36O8: C, 74.52; H, 5.63. Found: C, 74.72; H, 5.38.
8-Methyl-1,2,3-trim-tolylnaphthalene and 6-methyl-1,2,3-trim-tolyl-
naphthalene (2f). 1H NMR (CDCl3, 300 MHz): See the Supporting Information,
available online.
8-Methoxy-1,2,3-tris(3-methoxyphenyl)naphthalene and 6-methoxy-1,
2,3-tris(3-methoxyphenyl)naphthalene (2g). 1H NMR (CDCl3, 300 MHz) See
the Supporting Information, available online.

1,2,3-TRIPHENYL NAPHTHALENE DERIVATIVES
3249
ACKNOWLEDGMENTS
We thank the Key Project of Chinese Ministry of Education (No. 209054) and
Major Technology Program of Zhejiang Province (2008C11062-1) for financial
support.
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