Dichloro[(2-dimethylamino)propyldiphenylphosphine]palladium(II) (PdCl2(alaphos)): An efficient catalyst for cross-coupling of aryl triflates with alkynyl grignard reagents

Article abstract of DOI:10.1021/jo981191f

Dichloro[(2-dimethylamino)propyldiphenylphosphine]palladium (PdCl₂(alaphos)) was found to be much more effective as catalyst than other palladium complexes for cross-coupling of aryl triflates with alkynyl Grignard reagents. Reaction of bromoaryl triflates with alkynyl Grignard reagents in the presence of PdCl₂(alaphos) catalyst gave high yields of alkynyl arene bromides, which were formed by selective replacement of triflate by alkynyl group.

Full text of DOI:10.1021/jo981191f

8922
J . Org. Chem. 1998, 63, 8922-8925
Dich lor o[(2-d im eth yla m in o)p r op yld ip h en ylp h osp h in e]p a lla d iu m (II)
(P d Cl2(a la p h os)): An Efficien t Ca ta lyst for Cr oss-Cou p lin g of Ar yl
Tr ifla tes w ith Alk yn yl Gr ign a r d Rea gen ts1
Takashi Kamikawa and Tamio Hayashi*
Department of Chemistry, Faculty of Science, Kyoto University, Sakyo, Kyoto 606-01, J apan
Received J une 18, 1998
Dichloro[(2-dimethylamino)propyldiphenylphosphine]palladium (PdCl2(alaphos)) was found to be
much more effective as catalyst than other palladium complexes for cross-coupling of aryl triflates
with alkynyl Grignard reagents. Reaction of bromoaryl triflates with alkynyl Grignard reagents
in the presence of PdCl2(alaphos) catalyst gave high yields of alkynyl arene bromides, which were
formed by selective replacement of triflate by alkynyl group.
In tr od u ction
selective replacement of triflate by alkynyl groups oc-
curred in the reaction of arenes containing both the
bromide and triflate groups with alkynyl Grignard
reagents catalyzed by PdCl2(alaphos) to give alkynyl
arene bromides in high yields.
Alkynyl arenes are very useful materials for π-conju-
gated polymers, liquid crystals, and so on.2 For the
carbon-carbon bond formation between aryl and alkynyl
groups, the Sonogashira reaction3 has been often used.4
Although alkynylmetal reagents of magnesium,5 zinc,6
and tin7 have been also conveniently used for the
preparation of alkynylarenes from aryl bromides and
iodides, few reports have appeared, to our knowledge, on
the successful alkynylation of aryl triflates, which are
readily available from the corresponding phenols, with
alkynyl Grignard reagents.8,9 During our studies on the
enantioposition-selective cross-coupling of aryl triflates
with the Grignard reagents,10,11 it was found that pal-
ladium complexes coordinated with â-(dimethylamino)-
alkyldiphenylphosphines are highly catalytically active
as well as enantioselective. Here we wish to report that
PdCl2(alaphos),12 where alaphos stands for (2-dimethyl-
amino)propyldiphenylphosphine, is a unique catalyst
which efficiently catalyzes the cross-coupling of aryl
triflates with alkynyl Grignard reagents forming alky-
nylarenes in high yields. It is also described that the
Resu lts a n d Discu ssion
Effects of phosphine ligands on the catalytic activity
were examined for the palladium-catalyzed cross-cou-
pling of 2-phenylphenyl triflate (1) with phenylethynyl-
magnesium bromide (Scheme 1), which was generated
by the reaction of phenylethyne with ethylmagnesium
bromide. The cross-coupling was carried out with 2 equiv
of the Grignard reagent in the presence of 1 equiv of LiBr
and 5 mol % of palladium catalyst at 30 °C. The results
are summarized in Table 1. It was found that PdCl2-
(alaphos) is by far the most effective of the palladium
and nickel catalysts examined, giving a 93% yield of
2-phenylethynylbiphenyl (2a ) in the reaction carried out
for 6 h (entry 1). The second best catalyst was PdCl2-
(PPh3)2, but the reaction was much slower, 30% of 2a
being formed after 24 h (entry 2). PdCl2(dppp), which is
one of the most active catalytsts for the cross-coupling
of aryl triflates with the aryl Grignard reagents,1 is not
effective at all for the present cross-coupling with the
alkynyl Grignard reagent (entry 3). PdCl2(dppf) and
NiCl2(PPh3)2 were much less catalytically active than
PdCl2(alaphos) for the alkynylation (entries 4 and 5). The
reaction with triphenylsilylethynylmagnesium bromide
also proceeded efficiently to give 2-(triphenylsilylethynyl)-
biphenyl (2b) in 99% yield (entry 6).
(1) Part of this paper appeared previously: Kamikawa, T.; Hayashi,
T. Synlett 1997, 163.
(2) For examples, see the following. (a) Haley, M. M.; Bell, M. L.;
English, J . J .; J ohnson, C. A.; Weakley, T. J . R. J . Am. Chem. Soc.
1997, 119, 2956. (b) Ley, K. D.; Whittle, E.; Bartberger, M. D.; Schanze,
K. S. J . Am. Chem. Soc. 1997, 119, 3423. (c) Manna, J .; Whiteford, J .
A.; Stang, P. J .; Muddiman, D. C.; Smith, R. D. J . Am. Chem. Soc.
1996, 118, 8731.
(3) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975,
4467.
(4) For reviews, see the following. (a) Tsuji, J . Palladium Reagents
and Catalysts; Wiley: New York, 1995. (b) Heck, R. F. Palladium
Reagents in Organic Synthesis; Academic Press: New York, 1985.
(5) Rossi, R.; Capita, A.; Lezzi, A. Tetrahedron 1984, 40, 2773.
(6) Yoneda, N.; Matsuoka, S.; Miyaura, N.; Fukuhara, T.; Suzuki,
A. Bull. Chem. Soc. J pn. 1990, 63, 2124.
(7) Sakamoto, T.; Yasuhara, A.; Kondo, Y.; Yamanaka, H. Synlett
1992, 746.
(8) For palladium-catalyzed cross-coupling of aryl triflates with
alkynyltin, see: Echavarren, A. M.; Stille, J . K. J . Am. Chem. Soc.
1987, 109, 5478.
It would be very useful if aromatic compounds bearing
both bromide and triflate underwent the selective re-
placement of either bromide or triflate by an alkynyl
group. Unfortunately, there have been no examples of
the chemoselective alkynylation of bromoaryl triflates by
palladium-catalyzed cross-coupling type reactions,8,13
probably because of the difficulty in controlling the
reactivity of the bromide and triflate groups at the
oxidative addition to a palladium(0) species.14,15 In the
(9) For nickel-catalyzed cross-coupling of alkynyl Grignard reagents
with alkenyl carbamates, see: Madoc, D.; Pujol, S.; Henryon, V.;
Ferezou, J . P. Synlett 1995, 435.
(10) Hayashi, T.; Niizuma, S.; Kamikawa, T.; Suzuki, N.; Uozumi,
Y. J . Am. Chem. Soc. 1995, 117, 9101.
(11) Kamikawa, T.; Uozumi, Y.; Hayashi, T. Tetrahedron Lett. 1996,
37, 3161.
(12) Hayashi, T.; Konishi, M.; Fukushima, M.; Kanehira, K.; Hioki,
T.; Kumada, M. J . Org. Chem. 1983, 48, 2195.
(13) Selective alkenylation or carbonylation has been reported in
the palladium-catalyzed reactions of 4-bromophenyl triflate: (a) Cacchi,
S.; Ciattini, P. G.; Morera, E.; Ortar, G. Tetrahedron Lett. 1986, 27,
3931. (b) Oh-e, T.; Miyaura, N.; Suzuki, A. Synlett 1990, 221. (c) Saa´,
J . M.; Martorell, G. J . Org. Chem. 1993, 58, 1963.
10.1021/jo981191f CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/04/1998

Aryl Triflate-Alkynyl Grignard Cross-Coupling
J . Org. Chem., Vol. 63, No. 24, 1998 8923
Sch em e 1
Sch em e 3
Ta ble 1. Effects of P h osp h in e Liga n d s on th e
Cr oss-Cou p lin g of Ar yl Tr ifla te 1 w ith th e Alk yn yl
Gr ign a r d Rea gen tsa
entry
catalystb
Grignard
time (h) yield (%) of 2c
1
2
3
4
5
6
PdCl2(alaphos) PhCtCMgBr
6
24
6
24
6
93 (2a )
30 (2a )
0 (2a )
3 (2a )
0 (2a )
PdCl2(PPh3)2
PdCl2(dppp)
PdCl2(dppf)
NiCl2(PPh3)2
PhCtCMgBr
PhCtCMgBr
PhCtCMgBr
PhCtCMgBr
PdCl2(alaphos) Ph3SiCtCMgBr
10
99 (2b)
a
The cross-coupling was carried out with 2 equiv of Grignard
reagent in the presence of 1 equiv of LiBr and 5 mol % of palladium
b
catalyst in ether/toluene (3:1) at 30 °C. The ligands, alaphos,
dppp, and dppf stand for (2-dimethylamino)propyldiphenyl-
phosphine, 1,3-bis(diphenylphosphino)propane, and 1,1′-bis(diphe-
nylphosphino)ferrocene, respectively. c Isolated yield by silica gel
chromatography.
Ta ble 3. Cr oss-Cou p lin g of Br om oa r yl Tr ifla tes w ith
Alk yn yl Gr ign a r d Rea gen tsa
present alkynylation of 4-bromophenyl triflate (3) with
phenylethynylmagnesium bromide catalyzed by PdCl2-
(alaphos), it was found that the triflate group is selec-
tively replaced by the alkynyl group (Scheme 2). Thus,
the reaction of 3 with 2 equiv of phenyethynylmagnesium
bromide in the presence of 1 equiv of lithium bromide
and 5 mol % of PdCl2(alaphos) at 20 °C for 3 h gave a
96% yield of 1-bromo-4-(phenylethynyl)benzene (4a ) to-
gether with a small amount (2%) of 1,4-di(phenylethy-
nyl)benzene (6a ) (entry 1 in Table 2). None of 1-phenyl-
ethynyl-4-trifluoromethanesulfonyloxybenzene (5a), which
would be formed by the alkynylation of bromide, was
R in
entry triflate RCtCMgBr (°C) (h)
temp time yield (%)b of yield (%)b
alkynec
of diyne
1
2
3
4
5
6
7
8
9
3
3
3
7
7
8
8
9
9
Et3Si
n-C5H11
t-Bu
Ph
Et3Si
Ph
Et3Si
Ph
Et3Si
Ph
20
30
30
20
30
20
20
20
20
40
40
1
12
20
4
4
1
1
12
4
4
6
99 (4c)
92 (4d )
90 (4e)
2 (6c)
5 (6d )
8 (6e)
2 (12a )
3 (12c)
0
2 (14c)
2 (16a )
5 (16c)
0
92 (11a )
91 (11c)
99 (13a )
93 (13c)
95 (15a )
92 (15c)
94 (17a )
90 (17c)
10
11
10
10
Et3Si
5 (18c)
a
Sch em e 2
The reaction was carried out with 2 equiv of Grignard reagent
in the presence of 1 equiv of LiBr and 5 mol % of palladium catalyst
in ether/toluene (3:1). In no cases were starting materials or
b
alkynylarene triflates detected. Isolated yield by silica gel chro-
matography. c Monoalkynylation product at triflate.
detected at all. In the absence of lithium bromide, the
alkynylation was slower but the selectivity in forming
4a was kept high (entry 2), indicating that lithium
bromide is not responsible for the high triflate selectiv-
ity.16 Under the standard Sonogashira conditions,3,4
preferential substitution of bromide was observed, though
the selectivity was lower (entry 3).
Ta ble 2. P a lla d iu m -Ca ta lyzed Cr oss-Cou p lin g of
4-Br om op h en yl Tr ifla te (3) w ith
In the presence of PdCl2(alaphos) as catalyst, 4-bro-
mophenyl triflate (3) underwent the selective replace-
ment of the triflate group by several alkynyl Grignard
reagents to give the corresponding monoalkynylation
products 4 in high yields together with a minor amount
of dialkynylation products 6 (entries 1-3 in Table 3). The
selective substitution of triflate with an alkynyl group
was also successful in the reaction of benzene and
(P h en yleth yn yl)m a gn esiu m Br om id e or P h en yleth yn e
yield (%)a
of
time recovd
entry
1b
catalyst
reagent (equiv) (h) (%)a
3
4a 5a 6a
PdCl2(alaphos) PhCtCMgBr (2)
3
3
40
0
5
10
96
92
8
0
0
73
2
2
8
2b,c PdCl2(alaphos) PhCtCMgBr (2)
3d
PdCl2(PPh3)2
PhCtCH (2)
a
Isolated yield by silica gel chromatography. b The reaction was
carried out in the presence of 1 equiv of LiBr and 5 mol % of
palladium catalyst in ether/toluene (3:1) at 20 °C. c The reaction
in the absence of LiBr. The reaction was carried out in the
presence of 10 mol % of CuI and 10 mol % of palladium catalyst
in THF/Et3N (4:1).
(14) J utand, A.; Mosleh, A. Organometallics 1995, 14, 1810.
(15) Kamikawa, T.; Hayashi, T. Tetrahedron Lett. 1997, 38, 7087.
(16) Amatore, C.; J utand, A.; Suarez, A. J . Am. Chem. Soc. 1993,
115, 9531.
d

8924 J . Org. Chem., Vol. 63, No. 24, 1998
Kamikawa and Hayashi
Son oga sh ir a Rea ction of Br om op h en yl Tr ifla te (3)
w ith P h en yla cetylen e Ca ta lyzed by P d Cl2(P P h 3)2. To a
mixture of bromophenyl triflate (3) (60.4 mg, 0.20 mmol),
PdCl2(PPh3)2 (14 mg, 0.020 mmol), copper(I) iodide (3.8 mg,
0.020 mmol), and 0.25 mL of triethylamine in 1 mL of THF
was added phenylacetylene (32 µL, 0.29 mmol), and the
mixture was stirred at 40 °C for 12 h. The mixture was
quenched with 10% hydrochloric acid and extracted with 100
mL of ethyl acetate. The organic layer was washed with brine
(2 × 20 mL), dried over magnesium sulfate, and concentrated
under reduced pressure. The residue was purified by silica
gel column chromatography to give 47.6 mg (73% yield) of
4-trifluoromethanesulfonyloxy(phenylethynyl)benzene (5a ), 4.1
mg (8% yield) of 4-phenylethynylbromobenzene (4a ), and 4.4
mg (8% yield) of 1,4-di(phenylethynyl)benzene (6a ).
Sch em e 4
naphthalene derivatives bearing both triflate and bro-
mide (7-10). The triflate selectivities are all high, with
monoalkynylation products at triflate, namely, alkynyl-
arene bromides, being obtained in over 90% isolated
yields. Monoalkynylation products resulting from re-
placement of bromide were not observed in any case.
The monoalkynylation product, 1-bromo-4-(triethylsi-
lylethynyl)benzene (4c), obtained selectively by the reac-
tion of 3 with the triethylsilylethynyl Grignard reagent
in the presence of PdCl2(alaphos), was converted into
terminal acetylene 19 by desilylation with tetrabutylam-
monium fluoride, and it was submitted to the second
cross-coupling. The alkynyl Grignard reagent generated
from 19 was allowed to react with 4-iodophenyl triflate
by use of PdCl2(alaphos) as a catalyst. Selective substi-
tution of iodide took place to give 1-(4-bromophenyl)-2-
[(4-trifluoromethanesulfonyloxy)phenyl]ethyne (20) with
high selectivity. These results indicate that the order of
reactivity of the leaving groups on an aromatic ring is
iodide > triflate > bromide in the Grignard cross-coupling
catalyzed PdCl2(alaphos). The present selective alkynyl-
ation method provides an efficient route to various types
of conjugated aromatic compounds substituted with alky-
nyl groups.
Gr ign a r d Cr oss-Cou p lin g of Br om oa r yl Tr ifla tes w ith
Alkyn yl Gr ign ar d Reagen ts Catalyzed by P dCl2(alaph os).
Grignard cross-goupling of bromoaryl triflates with alkynyl
Grignard reagents catalyzed by PdCl2(alaphos) was carried out
in a manner similar to that of aryl triflate 1 shown above. The
results are summarized in Tables 2 and 3.
Spectral and analytical data for the alkynylation products
are shown below. 2-P h en yleth yn ylbip h en yl (2a ):17 1H NMR
(CDCl3, 270 MHz) δ 7.25-7.49 (m, 11 H), 7.63-7.68 (m, 3H).
2-Tr ip h en ylsilyleth yn ylbip h en yl (2b): 1H NMR (CDCl3,
500 MHz) δ 7.28-7.42 (m, 17 H), 7.53 (dd, J ) 1.5, 7.8 Hz,
6H), 7.71 (d, J ) 7.3 Hz, 1 H); 13C NMR (CDCl3, 125 MHz) δ
92.10, 109.09, 121.17, 126.92, 127.40, 127.86, 129.15, 129.35,
129.45, 129.74, 133.52, 133.70, 135.53, 135.96, 140.26, 144.74.
Anal. Calcd for C32H24Si: C, 88.03; H, 5.54. Found: C, 87.83;
H, 5.57. 4-P h en yleth yn ylbr om oben zen e (4a ):18 1H NMR
(CDCl3, 500 MHz) δ 7.35 (s, 7H), 7.39 (d, J ) 7.9 Hz, 2H),
7.48 (d, J ) 7.9 Hz, 2H), 7.52 (s, 2H). 4-Tr iflu or om eth a n e-
su lfon yloxy(p h en yleth yn yl)ben zen e (5a ): mp 55 °C; 1H
NMR (CDCl3, 500 MHz) δ 7.27-7.61 (m, 9H); 13C NMR (CDCl3,
125 MHz) δ 87.30, 91.27, 118.73 (q, J ) 318.8 Hz), 121.47,
122.52, 124.01, 128.44, 128.79, 131.67, 133.37, 148.89; EI-MS
m/z, 326 (M+, 27), 193 (100). Anal. Calcd for C15H9O3F3S: C,
55.22; H, 2.78. Found: C, 55.52; H, 2.77. 1,4-Di(p h en yl-
eth yn yl)ben zen e (6a ):19 1H NMR (CDCl3, 500 MHz) δ 7.34-
7.36 (m, 6H), 7.50-7.54 (m, 8H). 4-(Tr ieth ylsilyleth yn yl)-
br om oben zen e (4c): 1H NMR (CDCl3, 500 MHz) δ 0.67 (q, J
) 7.9 Hz, 6H), 1.04 (t, J ) 7.9 Hz, 9H), 7.32 (d, J ) 8.8 Hz,
2H), 7.42 (d, J ) 8.8 Hz, 2H); 13C NMR (CDCl3, 125 MHz) δ
4.38, 7.46, 93.76, 104.86, 123.25, 131.79; EI-MS m/z, 296 (M+
+ 2, 11), 294 (M+, 11), 209 (100). Anal. Calcd for C14H19BrSi:
C, 56.94; H, 6.49. Found: C, 57.11; H, 6.60. 1,4-Bis-
(tr ieth ylsilyleth yn yl)ben zen e (6c): mp 36-38 °C; 1H NMR
(CDCl3, 500 MHz) δ 0.67 (q, J ) 8.3 Hz, 12H), 1.04 (t, J ) 8.3
Hz, 18H), 7.38 (s, 4H); 13C NMR (CDCl3, 125 MHz) δ 4.38, 7.46,
93.76, 105.86, 123.25, 131.79; EI-MS m/z, 354 (M+, 25), 325
(100). Anal. Calcd for C22H34Si2: C, 74.50; H, 9.66. Found:
C, 74.25; H, 9.92. 4-Hep tyn ylbr om oben zen e (4d ): 1H NMR
(CDCl3, 500 MHz) δ 0.92 (t, J ) 7.0 Hz, 3H), 1.37 (sextet, J )
7.0 Hz, 2H), 1.43 (tt, J ) 7.0, 7.5 Hz, 2H), 1.60 (quint, J ) 7.0
Hz, 2H), 2.40 (t, J ) 7.5 Hz, 2H), 7.29 (s, 4H); 13C NMR (CDCl3,
125 MHz) δ 13.97, 19.40, 22.21, 28.33, 31.11, 79.55, 91.78,
121.50, 123.10, 131.39, 133.01; EI-MS m/z, 252 (M+ + 2, 26),
250 (M+, 26), 116 (100). Anal. Calcd for C13H15Br: C, 62.17;
H, 6.02. Found: C, 62.38; H, 6.07. 1,4-Dih ep tyn ylben zen e
(6d ): 1H NMR (CDCl3, 500 MHz) δ 0.92 (t, J ) 7.0 Hz, 6H),
1.37 (sextet, J ) 7.0 Hz, 4H), 1.43 (tt, J ) 7.0, 7.5 Hz, 4H),
1.60 (quint, J ) 7.0 Hz, 4H), 2.38 (t, J ) 7.5 Hz, 4H), 7.24 (d,
J ) 8.5 Hz, 2H), 7.40 (d, J ) 8.5 Hz, 2H); 13C NMR (CDCl3,
125 MHz) δ 13.97, 19.43, 22.21, 28.41, 31.11, 80.36, 91.92,
123.17, 131.31; EI-MS m/z, 266 (M+, 85), 141 (100). Anal.
Calcd for C20H26: C, 90.16; H, 9.84. Found: C, 90.33; H, 9.93.
4-(ter t-Bu tyleth yn yl)br om oben zen e (4e): 1H NMR (CDCl3,
500 MHz) δ 1.30 (s, 9H), 7.23 (d, J ) 8.3 Hz, 2H), 7.39 (d, J )
Exp er im en ta l Section
Ma ter ia ls. PPh3, dppf, and dppp from Aldrich Chemical
Co., Inc., were commercially available. Palladium complex
PdCl2(alaphos) was prepared according to the reported proce-
dures.12 Aryl triflates were prepared by triflation of phenols
with triflluoromethanesulfonic anhydride and pyridine. Ether
and toluene were distilled from sodium benzophenone ketyl
under nitrogen.
Syn t h esis of Alk yn ylm a gn esiu m Br om id e. Typ ica l
P r oced u r e. To a solution of phenylacetylene (510 mg, 4.99
mmol) in 1.4 mL of toluene was added ethylmagnesium
bromide (2.7 mL, 2 M ether solution, 5.5 mmol). The mixture
was heated at 50 °C for 30 min. Other alkynylmagnesium
bromides were prepared in a similar manner.
Gr ign a r d Cr oss-Cou p lin g of Ar yl Tr ifla tes (1) w ith
Alkyn yl Gr ign ar d Reagen ts Catalyzed by P dCl2(alaph os).
Typ ica l P r oced u r e. To a mixture of triflate 1 (60.4 mg, 0.2
mmol), dichloro[(2-dimethylamino)propyldiphenylphosphine]-
palladium (PdCl2(alaphos)) (4.4 mg, 0.01 mmol), and lithium
bromide (17.2 mg, 0.2 mmol) in 100 µL of ether was added
(phenylethynyl)magnesium bromide (290 µL, 1.4 M, 0.4 mmol)
in ether/toulene (2/1) at room temperature, and the mixture
was stirred at 30 °C until 1 was not detected by silica gel TLC
(hexane/benzene ) 3/1). The reaction mixture was quenched
with water and extracted with 100 mL of ether. Combined
ether extracts were washed with brine (2 × 20 mL), dried over
magnesium sulfate, and concentrated under reduced pressure.
The residue was purified by preparative TLC (silica gel,
hexane/benzene ) 3/1) to give 44.6 mg (93% yield) of 2-phe-
nylethynylbiphenyl (2a ). The reaction conditions and results
are summarized in Table 1.
(17) Bookham, J . L.; Smithies, D. M.; Wright, A.; Thornton-Pett,
M.; McFarlane, W. J . Chem. Soc., Dalton Trans. 1998, 811.
(18) Hellwinkel, D.; Fritsch, H. Chem. Ber. 1989, 122, 2315.
(19) Nakatsuji, S.; Matsuda, K.; Uesugi, Y.; Nakashima, K.; Ak-
iyama, S.; Fabin, W. J . Chem. Soc., Perkin Trans. 1 1992, 755.

Aryl Triflate-Alkynyl Grignard Cross-Coupling
J . Org. Chem., Vol. 63, No. 24, 1998 8925
8.3 Hz, 2H); 13C NMR (CDCl3, 125 MHz) δ 27.95, 30.92, 78.07,
404 (M+, 31), 117 (100). Anal. Calcd for C26H36Si2: C, 77.16;
H, 8.97. Found: C, 76.90; H, 9.09. 1-Br om o-2-(p h en yleth y-
n yl)n a p h th a len e (17a ): 1H NMR (CDCl3, 500 MHz) δ 7.18-
7.35 (m, 6H), 7.58 (m, 5H); 13C NMR (CDCl3, 125 MHz) δ 89.36,
90.35, 120.69, 121.16, 123.08, 127.07, 128.41, 128.46, 129.35,
129.51, 129.86, 129.99, 131.24, 131.44, 131.61, 133.73; EI-MS
99.71, 121.42, 123.07, 131.29, 133.02; EI-MS m/z, 238 (M+
+
2, 30), 236 (M+, 32), 142 (100). Anal. Calcd for C12H13Br: C,
60.78; H, 5.53. Found: C, 60.57; H, 5.53. 1,4-Di(ter t-
Bu tyleth yn yl)ben zen e (6e): 1H NMR (CDCl3, 500 MHz) δ
1.30 (s, 18H), 7.28 (s, 4H); 13C NMR (CDCl3, 125 MHz) δ 27.97,
30.98, 78.90, 99.81, 123.05, 131.28; EI-MS m/z, 238 (M+, 55),
223 (100). Anal. Calcd for C18H22: C, 90.70; H, 9.30. Found:
C, 90.70; H, 9.53. 2-(P h en yleth yn yl)br om oben zen e (11a ):
m/z, 306 (M+ + 2, 98), 304 (M+, 100). Anal. Calcd for C18H11
-
Br: C, 70.38; H, 3.61. Found: C, 70.17; H, 3.38. 1-Br om o-
2-(tr ieth ylsilyleth yn yl)n a p h th a len e (17c): 1H NMR (500
MHz, CDCl3) δ 0.74 (q, J ) 8.0 Hz, 6H), 1.09 (t, J ) 8.0 Hz,
9H), 7.51 (t, J ) 8.3 Hz, 1H), 7.52 (t, J ) 8.3 Hz, 1H), 7.59 (t,
J ) 8.3 Hz, 1H), 7.71 (d, J ) 8.3 Hz, 1H), 7.78 (d, J ) 7.9 Hz,
1H), 8.29 (d, J ) 8.3 Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ
4.43, 7.56, 98.21, 105.40, 123.50, 126.71, 127.12, 127.29,
127.80, 127.90, 128.13, 129.35, 132.17, 133.67; EI-MS m/z, 346
20
1H NMR (CDCl3, 500 MHz) δ 7.38-7.63 (m, 6H), 7.77 (d, J
) 7.8 Hz, 1H), 7.81 (d, J ) 7.8 Hz, 1H), 8.32 (d, J ) 7.8 Hz,
1H). 1,2-Di(p h en ylet h yn yl)b en zen e (12a ):21 1H NMR
(CDCl3, 500 MHz) δ 7.35-7.37 (m, 7H), 7.51-7.54 (m, 7H).
2-(Tr ieth ylsilyleth yn yl)br om oben zen e (11c): 1H NMR
(CDCl3, 500 MHz) δ 0.70 (q, J ) 8.0 Hz, 6H), 1.07 (t, J ) 8.0
Hz, 9H), 7.15 (t, J ) 8.0 Hz, 1H), 7.24 (t, J ) 8.0 Hz, 1H), 7.50
(d, J ) 8.0 Hz, 1H), 7.57 (d, J ) 8.0 Hz, 1H); 13C NMR (CDCl3,
125 MHz) δ 4.38, 7.50, 97.26, 104.11, 125.46, 125.74, 126.82,
129.43, 132.33, 133.73; EI-MS m/z, 296 (M+ + 2, 6), 294 (M+,
5), 267 (100). Anal. Calcd for C14H19BrSi: C, 56.94; H, 6.49.
Found: C, 56.93; H, 6.42. 1,2-Bis(tr ieth ylsilyleth yn yl)-
ben zen e (12c): 1H NMR (500 MHz, CDCl3) δ 0.69 (q, J ) 8.0
Hz, 12H), 1.06 (t, J ) 8.0 Hz, 18H), 7.23 (dd, J ) 2.5, 6.5 Hz,
2H), 7.47 (dd, J ) 2.5, 6.5 Hz, 2H); 13C NMR (CDCl3, 125 MHz)
δ 4.43, 7.56, 95.86, 104.59, 125.75, 127.88, 132.89; EI-MS m/z,
354 (M+, 28), 297 (100). Anal. Calcd for C22H34Si2: C, 74.50;
H, 9.66. Found: C, 74.44; H, 9.91. 3-(P h en yleth yn yl)-
br om oben zen e (13a ):22 1H NMR (CDCl3, 270 MHz) δ 7.02-
7.53 (m, 8H), 7.69 (s, 1H). 3-(Tr ieth ylsilyleth yn yl)br o-
m oben zen e (13c): 1H NMR (CDCl3, 500 MHz) δ 0.67 (q, J )
7.8 Hz, 6H), 1.04 (t, J ) 7.8 Hz, 9H), 7.16 (t, J ) 7.9 Hz, 1H),
7.39 (d, J ) 7.9 Hz, 1H), 7.44 (d, J ) 7.9 Hz, 1H), 7.61 (s, 1H);
13C NMR (CDCl3, 125 MHz) δ 4.35, 7.45, 93.42, 104.54, 122.00,
(M+ + 2, 27), 344 (M+, 26), 179 (100). Anal. Calcd for C18
21BrSi: C, 62.60; H, 6.13. Found: C, 62.37; H, 6.09. 1,2-
-
H
Bis(t r iet h ylsilylet h yn yl)n a p h t h a len e (18c): 1H NMR
(CDCl3, 500 MHz) δ 0.72 (q, J ) 8.0 Hz, 6H), 0.78 (q, J ) 8.0
Hz, 6H), 1.09 (t, J ) 8.0 Hz, 9H), 1.13 (t, J ) 8.0 Hz, 9H), 7.50
(t, J ) 8.5 Hz, 1H), 7.51 (d, J ) 8.5 Hz, 1H), 7.57 (t, J ) 8.5
Hz, 1H), 7.70 (d, J ) 8.5 Hz, 1H), 7.78 (d, J ) 8.0 Hz, 1H),
8.37 (d, J ) 8.0 Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ 4.48,
4.56, 7.63, 7.71, 97.09, 102.23, 102.50, 105.60, 123.74, 124.39,
126.59, 126.87, 127.32, 128.06, 129.07, 132.40, 133.42; EI-MS
m/z, 404 (M+, 100). Anal. Calcd for C26H36Si2: C, 77.16; H,
8.97. Found: C, 76.93; H, 9.12.
4-Eth yn ylbr om oben zen e (19). To a solution of 4-(trieth-
ylsilylethynyl)bromobenzene (5c) (200 mg, 0.738 mmol) in 2
mL of THF was added aqueous tetrabutylammonium fluoride
(0.5 mL) at room temperature. The reaction mixture was
stirred for 30 min and then concentrated under reduced
pressure and extracted with 100 mL of ether. The organic
layer was washed with water (2 × 50 mL), dried over
magnesium sulfate, and concentrated under reduced pressure.
The residue was purified by silica gel column chromatography
(hexane/ethyl acetate ) 10/1) to give 75 mg (quantitative yield)
of 19:23 1H NMR (CDCl3, 500 MHz) δ 3.12 (s, 1H), 7.35 (d, J )
7.9 Hz, 2H), 7.46 (d, J ) 7.9 Hz, 2H).
125.33, 129.59, 130.53, 131.51, 134.74; EI-MS m/z, 296 (M+
+
2, 5), 294 (M+, 5), 129 (100). Anal. Calcd for C14H19BrSi: C,
56.94; H, 6.49. Found: C, 57.17; H, 6.60. 1,3-Bis(tr ieth yl-
silyleth yn yl)ben zen e (14c): 1H NMR (CDCl3, 500 MHz) δ
0.67 (q, J ) 7.8 Hz, 12H), 1.04 (t, J ) 7.8 Hz, 18H), 7.23 (t, J
) 8.0 Hz, 1H), 7.39 (dd, J ) 1.5, 8.0 Hz, 2H), 7.57 (t, J ) 1.5
Hz, 1H); 13C NMR (CDCl3, 125 MHz) δ 4.38, 7.48, 92.36,
105.35, 123.53, 128.13, 131.85, 135.40; EI-MS m/z, 354 (M+,
11), 325 (100). Anal. Calcd for C22H34Si2: C, 74.50; H, 9.66.
Found: C, 74.51; H, 9.80. 2-Br om o-6-(p h en yleth yn yl)-
1
n a p h th a len e (15a ): mp 131-133 °C; H NMR (CDCl3, 270
1-(4-Br om oph en yl)-2-[(4-tr iflu or om eth an esu lfon yloxy)-
p h en yl]eth yn e (20). To a solution of 19 (36.2 mg, 0.20 mmol)
in 100 mL of ether and 100 mL of toluene was added
ethylmagnesium bromide (1.6 M, 130 mL, 0.21 mmol) at room
temperature, and the mixture was stirred at 50 °C for 30 min.
To a mixture of 4-iodophenyl triflate (41 mg, 0.12 mmol),
lithium bromide (10 mg, 0.12 mmol), and PdCl2(alaphos) (2.4
mg, 0.006 mmol) was added the Grignard reagent. The
mixture was stirred at 30 °C for 2 h, quenched with water,
dried over magnesium sulfate, and concentrated under reduced
pressure. The residue was purified by silica gel column
chromatography (hexane/ethyl acetate ) 10/1) to give 44.3 mg
(91% yield) of 20: mp 152-153 °C; 1H NMR (CDCl3, 500 MHz)
δ 7.27 (d, J ) 8.8 Hz, 2H), 7.39 (d, J ) 8.8 Hz, 2H), 7.50 (d, J
) 8.8 Hz, 2H), 7.59 (d, J ) 8.8 Hz, 2H); 13C NMR (CDCl3, 125
MHz) δ 88.39, 90.15, 118.73 (q, J ) 321.3 Hz), 121.57, 123.13,
123.66, 130.47, 131.75, 133.07, 133.40, 149.06; EI-MS m/z 406
MHz) δ 7.34-7.37 (m, 2H), 7.54-7.57 (m, 3H), 7.69 (d, J )
8.5 Hz, 1H), 7.72 (t, J ) 8.5 Hz, 1H), 8.00 (d, J ) 9.5 Hz, 1H);
13C NMR (CDCl3, 125 MHz) δ 89.36, 90.35, 120.68, 121.12,
123.07, 127.06, 128.39, 128.44, 129.31, 129.48, 129.84, 129.96,
131.23, 131.41, 131.65, 133.70; EI-MS m/z, 308 (M+ + 2, 100),
306 (M+, 99). Anal. Calcd for C18H11Br: C, 70.38; H, 3.61.
Found: C, 70.09; H, 3.39. 2,6-Di(p h en yleth yn yl)n a p h th a -
len e (16a ): mp 200-201 °C; 1H NMR (CDCl3, 500 MHz) δ
7.34-7.40 (m, 6H), 7.52-7.61 (m, 6H), 7.79 (d, J ) 8.5 Hz,
2H), 8.03 (s, 2H); 13C NMR (CDCl3, 125 MHz) δ 89.63, 90.47,
121.44, 123.17, 127.83, 128.41, 129.17, 131.19, 131.69, 131.72,
132.38. Anal. Calcd for C26H16: C, 95.09; H, 4.91. Found:
C, 94.69; H, 4.94. 2-Br om o-6-(tr ieth ylsilyleth yn yl)n a p h -
th a len e (15c): 1H NMR (CDCl3, 500 MHz) δ 0.71 (q, J ) 8.0
Hz, 6H), 1.07 (t, J ) 8.0 Hz, 8H), 7.53 (d, J ) 8.5 Hz, 1H),
7.55 (d, J ) 8.5 Hz, 1H), 7.65 (d, J ) 8.5 Hz, 1H), 7.67 (d, J )
8.5 Hz, 1H), 7.96 (s, 1H), 7.97 (s, 1H); 13C NMR (CDCl3, 125
MHz) δ 4.43, 7.50, 92.86, 106.19, 120.71, 121.16, 126.87,
129.28, 129.81, 129.92, 131.28, 131.79, 133.57; EI-MS m/z, 346
(M+ + 2, 20), 404 (M+, 21), 271 (100). Anal. Calcd for C24
17O3BrF3S: C, 44.46; H, 1.99. Found: C, 44.42; H, 1.91.
-
H
(M+ + 2, 27), 344 (M+, 26), 259 (100). Anal. Calcd for C18
-
H
21BrSi: C, 62.60; H, 6.13. Found: C, 62.47; H, 6.10. 2,6-
Bis(t r iet h ylsilylet h yn yl)n a p h t h a len e (16c): 1H NMR
(CDCl3, 500 MHz) δ 0.71 (q, J ) 7.5 Hz, 12H), 1.07 (t, J ) 7.5
Hz, 8H), 7.50 (d, J ) 8.5 Hz, 2H), 7.70 (d, J ) 8.5 Hz, 2H),
7.94 (s, 2H); 13C NMR (CDCl3, 125 MHz) δ 4.45, 7.51, 92.91,
106.44, 121.45, 127.62, 129.41, 131.70, 132.28; EI-MS m/z
Ack n ow led gm en t. This work was supported by the
Research for the Future Program, the J apan Society for
the Promotion of Science, and a Grant-in-Aid for Sci-
entific Research, the Ministry of Education, J apan.
J O981191F
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