Pd(0)-Cu(I)-catalyzed cross-coupling of alkynylsilanes with triarylantimony(V) diacetates

Article abstract of DOI:10.1039/b007800j

The Pd(0)-Cu(1)-catlyzed cross-coupling of alkynylsilanes with triarylantimony(V) diacetates was studied. Direct carbonylative coupling of triarylantimony diacetates with alkynylsilanes was accomplished under atmospheric pressure of carbon monoxide. It wa

Full text of DOI:10.1039/b007800j

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Pd(0)–Cu(I)-catalyzed cross-coupling of alkynylsilanes with
triarylantimony(V) diacetates
Suk-Ku Kang,* Hyung-Chul Ryu and Young-Taek Hong
1
Department of Chemistry, Institute for Basic Sciences, Sungkyunkwan University,
Natural Science Campus, Suwon 440-746, Korea
Received (in Cambridge, UK) 26th September 2000, Accepted 9th February 2001
First published as an Advance Article on the web 14th March 2001
Treatment of alkynylsilanes with triarylantimony diacetates in the presence of Pd2(dba)3ؒCHCl3 (5 mol%) and
CuI (10 mol%) in CH3CN at 50 ЊC for 5 h afforded aryl-substituted alkynes in good yield. Alternatively, direct
carbonylative coupling of triarylantimony diacetates with alkynylsilanes was accomplished under atmospheric
pressure of carbon monoxide.
The palladium-catalyzed cross-coupling reaction of terminal
alkynes with aryl or vinyl halides in the presence of a Pd(0)–
Results and discussion
1
Pd(0)–Cu(I)-catalyzed cross-coupling of alkynylsilanes with
Cu() co-catalyst system, known as Sonogashira and Hagihara
coupling,1 has been widely utilized as a practical synthetic
method for carbon–carbon bond formation in organic syn-
thesis. In synthesis, for the introduction of appropriate func-
tionalities, a terminal alkyne moiety is often protected with a
trimethylsilyl group. Thus the direct coupling of alkynylsilanes
should be more accessible. There have only been a few reports
of such direct coupling reactions of alkynylsilanes with aryl
halides; in the presence of fluoride ion by Hiyama et al.2 or
under basic conditions by Rossi3 and Huang4 and their
co-workers. Recently Hiyama et al.5 reported a copper()-salt
mediated direct Pd(0)-cross coupling reaction of alkynylsilanes
with triflates in the presence of CuCl in DMF. Nagasaka et al.6
also reported the direct silver-promoted cross-coupling of alky-
nylsilanes with aryl iodides to form aryl-substituted alkynes.
Alternatively, in order to synthesize alkynyl ketones CuCl-
catalyzed reaction of alkynylsilanes and acyl halides by one-pot
desilylation–coupling was reported by Hosomi et al.7. We have
investigated the use of triarylantimony() diacetates8 in
palladium-catalyzed cross-coupling reactions; here we wish to
report the direct palladium-catalyzed cross-coupling and
carbonylative cross-coupling of alkynylsilanes with triaryl-
antimony diacetates to afford the aryl-substituted alkynes and
alkynyl ketones (Scheme 1).9
organoantimony(V) compounds
The results of the palladium–copper catalyzed cross-coupling
of alkynylsilanes with triarylantimony diacetates are summar-
ized in Scheme 3 and Table 1.
Scheme 3
The (phenylethynyl)trimethylsilane (1a) reacted with triphen-
ylantimony diacetate (2a) in the presence of Pd2(dba)3ؒCHCl3
(5 mol%) and CuI (10 mol%) in CH3CN at 50 ЊC for 5 h to
afford 1,2-diphenylacetylene (3a) in 81% yield (entry 1 in Table
1). No homocoupling reaction of alkynylsilanes12 was observed
using Ar3Sb(OAc)2. The addition of CuI is critical and
improved the yield. Of the catalysts (Pd2(dba)3ؒCHCl3, PdCl2,
(π-allyl)2Pd2Cl2, Pd2(dba)3, PdCl2(PhCN)2) tested, Pd2(dba)3ؒ
CHCl3 was the best choice. Among the solvents (DMF,
CH3CN, toluene and DME) tested, CH3CN was the most
suitable at 50 ЊC. Under the same conditions the reaction of 1a
with tri-p-tolylantimony diacetate (2b) gave 1-phenyl-2-p-tolyl-
acetylene (3b13a) in 80% yield (entry 2). For the aryl-substituted
silanes 1b and 1c, triphenylantimony diacetate (2a) was success-
fully coupled to give 3c12c and 3d13b under the same conditions
in 73 and 70% yields, respectively (entries 3 and 4). The acetyl-
substituted ethynylsilane 1d was treated with 2a and 2b to
provide 3e and 3f in 85 and 82% yields, respectively (entries 5
and 6). When the 1,2-bis(trimethylsilyl)ethyne (1e) was reacted
with 2a and 2b, the disubstituted acetylene 3a and 3g13c were
afforded in 80 and 77% yields, respectively (entries 7 and 8).
Finally for the 1,4-bis(trimethylsilanylethynyl)benzene (1f),
disubstituted product 3h13d was obtained using Pd2(dba)3ؒ
CHCl3 as a catalyst (entry 9). However, when PdCl2 was
employed as a catalyst, the mono-substituted product 3i13e was
afforded in 42% yield (entry 10).
Scheme 1
Triarylantimony() diacetates 2a10 and 2b11 were prepared by
reaction of triarylantimony() with PhI(OAc)2 by stirring in
CH2Cl2 at room temperature for 7 h (Scheme 2).
2
Pd(0)–Cu(I)-catalyzed carbonylative cross-coupling of
alkynylsilanes with organoantimony(V) compounds
This coupling was extended to carbonylative cross-coupling of
silanes with antimony() compounds. The results are summar-
ized in Scheme 4 and Table 2.
Scheme 2
736
J. Chem. Soc., Perkin Trans. 1, 2001, 736–739
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b007800j

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Table 1 Pd(0)–Cu()-catalyzed cross-coupling of alkynylsilanes with triarylantimony diacetates
Entry
Silanes
Triarylantimony diacetates
Product
Yieid (%)
1
Ph3Sb(OAc)2
2a
81
80
2
3
4
5
1a
(p-Tol)3Sb(OAc)2
2b
2a
2a
2a
73
70
85
6
1d
1e
2b
82
7
8
2a
2b
77
80
9
2a
2a
75
42
10
1f
In considering the plausible mechanism for carbonylative
cross-coupling, the palladium complex A is generated by
oxidative addition of the Ar–Sb bond of triarylantimony()
diacetate onto Pd(0) followed by carbonylation. Altern-
atively, the alkynyl group is transferred from alkynylsilane
to copper to form alkynylcopper B. The alkynyl group in
B migrates from copper to palladium to furnish intermediate
C which is subjected to reductive elimination to give the direct
coupled product, regenerating Pd(0) and Cu() as a catalyst
(Scheme 5).14
In conclusion triarylantimony() diacetates were prepared
conveniently and cross-coupling and carbonylative cross-
coupling of triarylantimony() derivatives with alkynylsilanes
were achieved in the presence of Pd2(dba)3ؒCHCl3 (5 mol%)
and CuI (10 mol%), at 50 ЊC at atmospheric pressure of carbon
monoxide for the carbonylative cross-coupling.
Scheme 4
(3,3-Dimethylbut-1-ynyl)trimethylsilane (1g) was treated
with triphenylantimony diacetate (2a) in the presence of
Pd2(dba)3ؒCHCl3 (5 mol%) and CuI (10 mol%) under atmos-
pheric pressure of carbon monoxide in CH3CN to give ynone
4e13f in 80% yield (entry 6 in Table 2). Under the same con-
ditions phenylethynylsilane (1a) reacted with 2a to afford benz-
oyl substituted alkynone 4a13g in 62% yield (entry 1). For the
substituted arylethynylsilanes 1b and 1c, the reactions with
triphenylantimony diacetate (2a) provided the carbonylated
coupled products 4b13h and 4c in 65 and 68% yields, respectively
(entries 2 and 3). The bis-silyl substituted 1e and 1f were readily
coupled with 2a to afford the mono carbonylated silanes 4a and
4d in 66 and 58% yields, respectively (entries 4 and 5). This
method was also applied to p-tolyl substituted antimony di-
acetate 2b. The alkynylsilanes 1g and 1b were subjected to
carbonylative cross-coupling to afford ynones 4f and 4g in 77
and 81% yields, respectively (entries 7 and 8). To the best of our
knowledge this is the first direct Pd(0)-catalyzed carbonylative
cross-coupling of alkynylsilanes without deprotection of a silyl
group.
Experimental
Typical procedure for the preparation of triarylantimony(V)
diacetate
A mixture of triarylantimony (2.0 mmol) and (diacetoxyiodo)-
benzene diacetate (2.2 mmol) in dichloromethane (20 mL) was
stirred at room temperature for 7 h. The solvent was concen-
trated under reduced pressure to a small volume. A mixture of
diethyl ether–pentane was added and the solution was kept
overnight at Ϫ15 ЊC. The solid was filtered and recrystallized
from a mixture of dichloromethane and pentane.
J. Chem. Soc., Perkin Trans. 1, 2001, 736–739
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Table 2 Pd(0)–Cu()-catalyzed carbonylative cross-coupling of alkynylsilanes with triarylantimony diacetates
Entry
Silanes
Triarylantimony diacetates
Product
Yieid (%)
1
Ph3Sb(OAc)2
2a
62
65
68
66
58
2
3
4
5
2a
2a
2a
2a
2a
6
7
8
80
77
80
1g
1b
(p-Tol)3Sb(OAc)2
2b
2b
Scheme 5
Triphenylantimony() diacetate (2a): mp 210–212 ЊC (lit.15
208–209 ЊC); δH 1.83 (s, 6H), 7.48 (m, 9H), 7.99 (m, 6H).
Tri(p-tolyl)antimony() diacetate (2b): mp 157–159 ЊC;
δH 1.82 (s, 6H), 2.39 (s, 9H), 7.27 (d, 6H, J = 8 Hz), 7.86 (d, 6H,
J = 8 Hz).
1-Phenylethynyl-4-methylbenzene (3b). Hexanes, Rf = 0.40;
δH (500 MHz; CDCl3) 2.37 (s, 3 H), 7.17 (d, 1 H, J = 7.8 Hz),
7.34 (m, 3 H), 7.42 (m, 2 H), 7.53 (m, 2 H); νmax (KBr)/cmϪ1
3084, 2964, 1612, 1480, 1372, 695; m/z 192 (100), 191, 189, 165,
115.
Typical procedure for the cross-coupling of alkynylsilanes with
organoantimony(V) compounds
1-Methoxy-4-(phenylethynyl)benzene (3c). EtOAc–hexanes
1 : 10, Rf = 0.52; δH (500 MHz; CDCl3) 3.83 (s, 3 H), 6.89 (dd,
1 H, J = 4.2, 2.0 Hz), 7.33 (m, 3 H), 7.51 (m, 4 H); νmax (KBr)/
cmϪ1 3080, 2958, 1617, 1405; m/z 208, 207 (100), 193 (49), 165
(52).
Diphenylacetylene (3a). To a mixture of triphenylantimony
diacetate (2a) (412 mg, 1.00 mmol), Pd2(dba)3ؒCHCl3 (112 mg,
5 mol%) and CuI (19 mg, 10 mol%) was added (phenyleth-
ynyl)trimethylsilane (1a) (169 mg, 1.00 mmol) under N2
charged at 50 ЊC in CH3CN (20 mL). The reaction mixture was
stirred at 50 ЊC for 5 h, extracted with ether (20 mL × 3), and
washed with water (20 mL × 3). The organic layer was dried
over anhydrous MgSO4 and evaporated in vacuo. The crude
product was separated by SiO2 column chromatography
(hexanes, Rf = 0.48) to afford the coupled product diphenyl-
acetylene (3a) (144 mg, 81%); δH (500 MHz; CDCl3) 7.26 (m,
2H), 7.36 (m, 4 H), 7.54 (m, 4 H); νmax (KBr)/ cmϪ1 3063, 1600,
1499, 1070, 755; m/z 178 (100), 176, 152, 89, 88, 76.
4-Phenylethynylbenzonitrile (3d). EtOAc–hexanes 1 : 30, Rf =
0.33; δH (500 MHz; CDCl3) 7.37 (m, 3 H), 7.50 (m, 2 H), 7.62
(m, 4 H); m/z 204 (11), 103 (100), 156 (10), 88 (11).
4-Phenylbut-3-yn-2-one (3e). EtOAc–hexanes 1 : 10, Rf =
0.48; δH (500 MHz; CDCl3) 2.45 (s, 3 H), 7.38 (m, 2 H), 7.45 (m,
1 H), 7.56 (m, 2 H); νmax (KBr)/cmϪ1 3054, 2865, 1680, 1456.
4-(4-Methylbenzene)but-3-yn-2-one (3f). EtOAc–hexanes
1 : 10, Rf = 0.47; δH (500 MHz; CDCl3) 2.38 (s, 3 H), 2.45 (s, 3
H), 7.19 (d, 2 H, J = 9.9 Hz), 7.47 (dd, 2 H, J = 9.9, 2.1 Hz);
Compounds 3b–3i were prepared following the above
procedures using the appropriate starting material.
738
J. Chem. Soc., Perkin Trans. 1, 2001, 736–739

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δC (125 MHz; CDCl3) 200.9, 157.9, 150.5, 137.6, 137.2, 130.0,
128.7, 30.1, 21.9; νmax (KBr)/cmϪ1 3054, 2865, 1680,1456; m/z
158 (27), 143 (100), 115 (13), 89 (9); HRMS for C11H10O calcd:
158.0732, found: 158.0728.
H), 7.27 (m, 2 H), 7.69 (m, 2 H), 8.00 (m, 2 H); δC (125 MHz;
CDCl3) 178.8, 145.5, 135.5, 130.3, 129.9, 104.1, 78.9, 30.9, 28.7,
22.5; νmax (KBr)/cmϪ1 3055, 2888, 1706, 1450; HRMS for
C14H16O calcd: 200.1201, found: 200.1203.
Bis(4-methylphenyl)acetylene (3g). Hexanes, Rf = 0.38;
δH (500 MHz; CDCl3) 2.36 (s, 3 H), 7.24 (d, 2 H, J = 8.0 Hz),
7.50 (d, 2 H, J = 8.0 Hz); νmax (KBr)/cmϪ1 3080, 2964, 1609,
1480, 1377; m/z 207 (10), 106 (100), 189 (15), 102 (10), 101 (11),
89 (14).
3-(4-Methoxyphenyl)-1-(p-tolyl)prop-2-yn-1-one
(4g).
EtOAc–hexanes 1 : 10, Rf = 0.16; δH (500 MHz; CDCl3) 2.45
(s, 3 H), 3.89 (s, 3 H), 6.98 (m, 2 H), 7.41 (m, 2 H), 7.45 (m, 1 H),
7.66 (m, 2 H), 8.19 (m, 2 H); δC (125 MHz; CDCl3) 178.5, 162.3,
145.7, 135.5, 130.3, 130.0, 129.7, 115.1, 112.7, 94.5, 87.6, 56.1,
22.5; νmax (KBr)/cmϪ1 3055, 2963, 2200, 1632, 1264; HRMS for
C17H14O2 calcd: 250.0994, found: 250.0988.
1,4-Bis(phenylethynyl)benzene (3h). Hexanes, Rf = 0.27;
δH (500 MHz; CDCl3) 7.45 (m, 3 H), 7.58 (m, 4 H); m/z 278
(100), 139 (28), 126 (9).
Acknowledgements
The authors wish to acknowledge the financial support by
KOSEF-Center for Molecular Design and Synthesis (CMDS).
H-C. Ryu and Y-T. Hong are BK-21 graduate fellows spon-
sored by the Ministry of Education.
Trimethyl[4-(phenylethynyl)phenylethynyl]silane (3i). Hex-
anes, Rf = 0.29; δH (500 MHz; CDCl3) 0.12 (s, 9 H), 7.32 (m,
3 H), 7.49 (m, 4 H), 7.52 (m, 2 H); m/z 274 (13), 273 (55), 260
(22), 259 (100), 130 (17).
Typical procedure for the carbonylative cross-coupling of
alkynylsilanes with organoantimony(V) compounds
References
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Pd2(dba)3ؒCHCl3 (112 mg, 5 mol%) and CuI (19 mg, 10 mol%)
was added (4-methoxyphenylethynyl)trimethylsilane (1b) (168
mg, 1.00 mmol) under atmospheric pressure of CO at 50 ЊC in
CH3CN (20 mL). The reaction mixture was stirred at 50 ЊC for
5 h, extracted with ether (20 mL × 3), and washed with water
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MgSO4 and evaporated in vacuo. The crude product was separ-
ated by SiO2 column chromatography (EtOAc–hexanes 1 : 10,
Rf = 0.19) to afford the coupled product 3-(4-methoxyphenyl)-
1-phenylprop-2-yn-1-one (4b) (118 mg, 65%); δH (500 MHz;
CDCl3) 3.89 (s, 3 H), 6.98 (m, 2 H), 7.41 (m, 2 H), 7.45 (m, 1 H),
7.66 (m, 2 H), 8.19 (m, 2 H); νmax (KBr)/cmϪ1 3055, 2200, 1632,
1264; m/z 237, 236, 208, 193, 165, 159 (100), 144.
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8 Triarylantimony() diacetates 2a and 2b were prepared by the
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reaction of triarylantimony() with PhI(OAc)2 by stirring in
CH2Cl2 at room temperature for 7 h afforded triarylantimony()
diacetates 2a and 2b.
Compounds 4a,c–g were prepared following the above
procedures using the appropriate starting material.
9 The phenylation of an alkynylsilane with triphenylbismuth
difluoride has been reported; S. A. Lermontov, I. M. Rakov, N. S.
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11 S. N. Bahahacharya and M. Singh, Indian J. Chem., Sect. A, 1979,
18, 515 (Chem. Abstr., 1980, 92, 215506e).
1,3-Diphenylprop-2-yn-1-one (4a). EtOAc–hexanes 1 : 10,
Rf = 0.34; δH (500 MHz; CDCl3) 7.41 (m, 2 H), 7.48 (m, 1 H),
7.52 (m, 1 H), 7.62 (m, 1 H), 7.68 (m, 1 H), 8.22 (m, 2 H); νmax
(KBr)/cmϪ1 3055, 2200, 1641; m/z 206 (95), 178 (100), 129 (94).
12 (a) F. Babudri, A. R. Cicciomessere, G. M. Farinola, V. Fiandanese,
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4-(3-Oxo-3-phenylprop-1-ynyl)benzonitrile (4c). EtOAc–
hexanes 1 : 7, Rf = 0.34; δH (500 MHz; CDCl3) 7.36–7.82 (m, 7
H), 8.19 (m, 2 H); δC (125 MHz; CDCl3) 174.9, 134.0, 132.1,
130.8, 130.6, 129.9, 127.2, 126.4, 122.5, 115.4, 111.6, 87.1; m/z
235 (15), 234 (99), 233 (100), 105 (14), 191 (12), 128 (29), 103
(82), 91 (23), 77 (33); νmax (KBr)/cmϪ1 3056, 2987, 2305, 2205,
1644; HRMS for C16H9NO calcd: 231.0684, found:231.0681.
1-Phenyl-3-(4-trimethylsilanylethynylphenyl)prop-2-yn-1-one
(4d). EtOAc–hexanes 1 : 10, Rf = 0.43; δH (500 MHz; CDCl3)
0.22 (s, 9 H), 7.58 (m, 2 H), 7.62 (m, 2 H), 7.74 (m, 1 H), 7.80
(m, 2 H), 8.18 (m, 2 H); δC (125 MHz; CDCl3) 178.5, 137.5,
134.9, 133.5, 132.8, 130.3, 129.5, 126.4, 120.6, 104.7, 98.9, 92.9,
88.9, 0.5; νmax (KBr)/cmϪ1 3055, 2987, 2199, 1641, 1423, 1265,
744; HRMS for C20H18OSi calcd: 302.1127, found: 302.1123.
14 As an indirect evidence for the formation of CuX (X = I or OAc) in
the catalytic cycle, when we have used CuOAc (10 mol%) instead
of CuI (10 mol%) as a catalyst for the coupling reaction of
triphenylantimony diacetate (2a) with (1-phenylethynyl)trimethyl-
silane (1a) under the same conditions we could get the coupled
product diphenylacetylene (3a) in 71% yield, which supports our
suggested mechanism.
4,4-Dimethyl-1-phenylpent-2-yn-1-one (4e). EtOAc–hexanes
1 : 10, Rf = 0.41; δH (500 MHz; CDCl3) 1.34 (s, 9 H), 7.61 (m,
2 H), 7.73 (m, 1 H), 8.05 (m, 2 H); m/z 186 (10), 143 (34), 128
(23), 105 (100), 77 (19).
4,4-Dimethyl-1-(p-tolyl)pent-2-yn-1-one (4f). EtOAc–hexanes
1 : 10, Rf = 0.47; δH (500 MHz; CDCl3) 1.56 (s, 9 H), 2.42 (s, 3
15 J. Bordner, G. O. Doak and T. S. Everett, J. Am. Chem. Soc., 1986,
108, 4206.
J. Chem. Soc., Perkin Trans. 1, 2001, 736–739
739