Palladium-catalyzed cross-coupling of organolead(IV) triacetates with terminal alkynes

Article abstract of DOI:10.1081/SCC-100103537

The palladium-catalyzed carbon-carbon bond formation of organolead(IV) triacetates with terminal alkynes was accomplished with Pd₂(dba)₃·CHCl₃ (5mol%) and CuI (10mol%) in the presence of NaOMe (2 equiv.) in MeOH/CH₃

Full text of DOI:10.1081/SCC-100103537

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PALLADIUM-CATALYZED
CROSS-COUPLING
OF ORGANOLEAD(IV)
TRIACETATES WITH TERMINAL
ALKYNES
Suk-Ku Kang a , Hyung-Chul Ryu a & Sang-Ho Lee a
a Department of Chemistry , Sungkyunkwan
University , Natural Science Campus, Suwon,
440-746, Korea
Published online: 09 Nov 2006.
To cite this article: Suk-Ku Kang , Hyung-Chul Ryu & Sang-Ho Lee (2001)
PALLADIUM-CATALYZED CROSS-COUPLING OF ORGANOLEAD(IV) TRIACETATES WITH
TERMINAL ALKYNES, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 31:7, 1059-1064, DOI: 10.1081/
SCC-100103537
To link to this article: http://dx.doi.org/10.1081/SCC-100103537
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SYNTHETIC COMMUNICATIONS, 31(7), 1059–1064 (2001)
PALLADIUM-CATALYZED CROSS-
COUPLING OF ORGANOLEAD(IV)
TRIACETATES WITH TERMINAL ALKYNES
Suk-Ku Kang,* Hyung-Chul Ryu, and Sang-Ho Lee
Department of Chemistry, Sungkyunkwan University,
Natural Science Campus, Suwon 440-746, Korea
ABSTRACT
The palladium-catalyzed carbon-carbon bond forma-
tion of organolead(IV) triacetates with terminal alkynes was
accomplished with Pd2(dba)3ꢀCHCl3 (5 mol%) and CuI
(10 mol%) in the presence of NaOMe (2 equiv.) in MeOH/
CH3CN (1:1) at room temperature.
The palladium-catalyzed cross-coupling of terminal alkynes with aryl
or vinyl halides (or triflates) in the presence of cuprous iodide as co-catalyst,
known as the Sonogashira coupling reaction,1–3 now has become a versatile
synthetic method in carbon-carbon bond formation. As an alternative to
organic electrophiles, we have reported the palladium-catalyzed coupling of
terminal alkynes with hypervalent iodonium salts and iodanes in aqueous
medium under mild conditions.4 Although Pinhey et al.5–7 reported the
arylation, alkenylation, and alkynylation of organolead(IV) compounds
with soft carbon nucleophiles, such as active methylene compounds, no
coupling of terminal alkynes by organolead(IV) compounds has been
known.8 In connection with our programs to utilize organolead triacetates
in the cross-coupling reaction9–11 we report here the palladium-catalyzed
* Corresponding author.
1059
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

1060
KANG, RYU, AND LEE
coupling of terminal alkynes with organolead(IV) triacetates using CuI as
co-catalyst in the presence of sodium methoxide (Scheme 1).
Scheme 1.
The results of the palladium-catalyzed cross-coupling of terminal
alkynes with organolead(IV) triacetates are summarized in Table 1. To
achieve the coupling for the coupling of phenylacetylene (1a) with p-tolyl-
lead triacetate (2b), we have found that the addition of 2 equivalents of
NaOMe as a base was critical.12 Presumably organolead methoxide inter-
mediate RPb(OMe)2OAc is formed from RPb(OAc)3 and NaOMe (2 equiv.),
which drives facile oxidative addition with Pd(0), followed by transmetalla-
tion and reductive elimination. We examined for the reaction of 1a with
2b, with various catalysts, for Pd2(dba)3ꢀCHCl3, Pd(OAc)2, Pd(PPh3)4,
and PdCl2. Pd2(dba)3ꢀCHCl3 was the best choice. To avoid homocoupling
of organolead compounds,13 it is essential to add CuI as co-catalyst. Of the
solvents tested (CHCl3, NMP, DMF, and benzene), the co-solvent MeOH/
CH3CN(1 : 1) was the best choice for this cross-coupling. When phenyl-
acetylene (1a) reacted with p-CH3C6H4Pb(OAc)3 (2b)14 (1 equiv.) in the
presence of Pd2(dba)3ꢀCHCl3 (5 mol%) and CuI (10 mol%) in with
NaOMe (2 equiv.) in MeOH/CH3CN (1 : 1) at room temperature for 3 h,
the coupled product 3a was afforded in 74% yield (entry 1 in Table 1).
Under the same conditions, the reaction of 1a with p-MeOC6H4Pb(OAc)3
(2c)15 gave the substituted alkynes 3b in 78% yield (entry 2). The 2-
thienyllead(IV) triacetate (2d)13 was subjected to couple with 1a and 1b to
afford the coupled product 3c and 3d in 79% and 72% yields, respectively
(entries 3 and 4). This coupling was also applied to alkenyllead(IV) triace-
tates 2e16 to provide the ynene 3e in 80% yield (entry 5). For the propargylic
alcohol 1c without protection, organolead(IV) triacetates 2a and 2d were
smoothly coupled to afford 3f and 3g in 78% and 76% yields, respectively
(entries 6and 7). It is notable that the methoxyvinyl-substituted terminal
alkynes 1d was readily coupled under mild conditions to afford the sub-
stituted alkynes 3h, 3i, and 3j in moderate yields (entries 8–10).

ORGANOLEAD(IV) TRIACETATES
1061
Table 1. The Palladium-Catalyzed Coupling of Organolead Compounds with
Terminal Alkynes
Organolead
Compounds
Isolated
Yield (%)
Entry
1
Substrate
Product
74
1a
1a
2b
2c
3a
2
3
4
78
79
72
3b
3c
3d
1a
2d
2d
1b
1b
5
6
7
80
78
76
2e
3e
3f
PhPb(OAc)3
1c
1c
2a
2d
2a
3g
8
76
1d
1d
3h
3i
3j
9
2c
2d
77
77
10
1d

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KANG, RYU, AND LEE
In summary, organolead(IV) triacetate was utilized as a novel reagent
for direct arylation and alkenylation of terminal alkynes under mild
conditions.
EXPERIMENTAL
Typical Procedure
Method A: Preparation of 1-Methoxy-4-(phenylethynyl)-benzene (3b)
To a stirred solution of p-methoxyphenyllead triacetate (2c) (280 mg,
0.58 mmol) and NaOMe (63 mg, 1.16 mmol) in MeOH/CH3CN (1 : 1, 5 mL)
was added Pd2(dba)3ꢀCHCl3 (28 mg, 5 mol%) and CuI (10 mg, 10 mol%),
followed by phenylacetylene (1a) (60 mg, 0.58 mmol) via syringe at room
temperature under N2 charged. The mixture was stirred at room tempera-
ture for 3 h. The reaction mixture was extracted with ether (20 mL ꢁ 3) and
washed with water (3 times), and the organic layer was dried over anhydrous
MgSO4 and evaporated in vacuo. The crude product was separated by
SiO2 column chromatography (EtOAc/hexanes ¼ 1 : 10, Rf ¼ 0.52) to give
coupled product 3b (94 mg, 78%). TLC, SiO2, EtOAc/hexanes 1 : 10,
Rf ¼ 0.52. 1H NMR (400 MHz, CDCl3), ꢀ 3.83 (s, 3H), 6.89 (dd, 2H,
J ¼ 4.2, 2.0 Hz), 7.33 (m, 3H), 7.51 (m, 4H). IR (KBr) ¼ 3080, 2958, 1617,
1405 cmÀ1. MS (EI): m/e (relative inensity) ¼ 208(Mþ), 207 (100), 193 (49),
165 (52).
Method B: Preparation of 3-(2-thiophenyl)propyn-1-ol (3g)
To a stirred solution of propargyl alcohol (33 mg, 0.58 mmol) and
NaOMe (63 mg, 1.16 mmol) in MeOH/CH3CN (1 : 1, 5 mL) was added
Pd2(dba)3ꢀCHCl3 (28 mg, 5 mol%) and CuI (10 mg, 10 mol%), followed by
2-thienyllead triacetate (2d) (270 mg, 0.58 mmol) in one portion at room
temperature under N2 and stirred at room temperature for 3 h. The reaction
mixture was extracted with ether (20 mL ꢁ 3) and washed with water, and
the organic layer was dried over anhydrous MgSO4 and evaporated in vacuo.
The crude product was separated by SiO2 column chromatography (EtOAc/
hexanes ¼ 1 : 5, Rf ¼ 0.42) to give coupled product 3g (61 mg, 76%).
1
TLC, SiO2, EtOAc/hexanes 1 : 5, Rf ¼ 0.42. H NMR (400 MHz, CDCl3)
ꢀ 4.50 (d, 2H, J ¼ 4.4 Hz), 6.97 (m, 1H), 7.21 (m, 1H), 7.27 (m, 1H).
IR (KBr) ¼ 3505, 3055, 1265, 896, 950 cmÀ1. MS (EI): m/e (relative
intensity) ¼ 139 (Mþ), 138 (100), 137 (44), 121 (22), 110 (50). HRMS
calcd. for C7H6OS: 138.0121, found: 138.0139.

ORGANOLEAD(IV) TRIACETATES
1063
(Z)-(4-Methoxy-3-buten-1-ynyl)benzene (3h)
1H NMR (400 MHz, CDCl3) ꢀ 3.87 (s, 3H), 4.85 (d, 1H, J¼ 6.4 Hz),
6.40 (d, 1H, J ¼ 6.4 Hz), 7.41 (m, 3H), 7.56 (m, 2H). IR (KBr) ¼ 3075,
2950, 1615, 1410 cmÀ1. MS (EI): m/e (relative intensity) ¼ 159 (Mþ), 158
(Mþ, 100), 115 (83). HRMS calcd. for C11H10O: 158.0732, found: 158.0733.
1-Methoxy-4-(4-methoxy-3-butten-1-ynyl)benzene (3i)
1H NMR (400 MHz, CDCl3) ꢀ 3.69 (s, 3H), 3.70 (s, 3H), 4.62 (d, 1H,
J ¼ 6.4 Hz), 6.22 (d, 1H, J ¼ 6.4 Hz), 6.72 (m, 2H), 7.32 (m, 2H).
IR (KBr) ¼ 3063, 1710, 1520, 910 cmÀ1. MS (EI): m/e (relative intensity) ¼
189 (Mþ1), 188 (M, 100), 145 (61), 115 (15). HRMS calcd. for C12H12O2:
188.0873, found: 188.0835.
2-(4-Methoxy-3-buten-1-ynyl)thiophene (3j)
1
Hexanes, Rf ¼ 0.35. H NMR (400 MHz, CDCl3) ꢀ 3.81 (s, 3H), 4.74
(d, 1H, J ¼ 6.4 Hz), 6.32 (d, 1H, J ¼ 6.4 Hz), 6.95 (dd, 1H, J ¼ 3.7, 1.6Hz),
7.17 (m, 1H), 7.21 (m, 1H). IR (KBr) ¼ 3060, 2967, 1410, 867 cmÀ1. MS
(EI): m/e (relative intensity) ¼ 165 (9), 164 (100), 121 (79), 63 (10).
ACKNOWLEDGMENTS
Generous financial support from KOSEF-Center for Molecular
Design and Synthesis (CMDS) is gratefully acknowledged.
REFERENCES AND NOTES
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4467–4470.
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5. Pinhey, J.T. Aust. J. Chem. 1991, 44, 1353–1382.
6. Pinhey, J.T. Pure & Appl. Chem. 1996, 68, 819–824.

1064
KANG, RYU, AND LEE
7. Hashimoto, S.; Miyazaki, Y.; Shinoda, T.; Ikegami, S. J. Chem. Soc.,
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8. Phenylation of terminal acetylene by triphenylbismuth difluoride in the
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12. Excess NaOMe (3–4 equiv.) gave the homocoupling product. With
Et3N as base, the homocoupled product of organolead compound
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Accepted May 8, 2000