Copper- and Manganese-Catalyzed Cross-Coupling of Organostannanes with Organic Iodides in the Presence of Sodium Chloride

Full text of DOI:10.1021/jo970656j

4208
J . Org. Chem. 1997, 62, 4208-4209
Ta ble 1. Cu I- a n d Mn Br 2-Ca ta lyzed Cr oss-Cou p lin g of
Cop p er - a n d Ma n ga n ese-Ca ta lyzed
Cr oss-Cou p lin g of Or ga n osta n n a n es w ith
Or ga n ic Iod id es in th e P r esen ce of Sod iu m
Ch lor id e†
2-Th ien yltr ibu tylsta n n a n e (1d ) w ith p-Iod oa n isole (2e)a
Suk-Ku Kang,* J ae-Sun Kim, and Sang-Chul Choi
Department of Chemistry, Sung Kyun Kwan University,
Natural Science Campus, Suwon 440-746, Korea
yieldsd (%)
Received April 11, 1997
entry
catalystb
saltsc
3i
85
85
80
40
10
88
86
4
1
2
3
4
5
6
7
8
9
CuI
CuI
CuI
CuI
NaCl
KCl
LiCl
KF
CsF
NaCl
KCl
KF
traces
traces
traces
22(10)e
30(16)e
traces
traces
50(10)e
35(12)e
20(8)e
The palladium-catalyzed cross-coupling of organostan-
nanes with aryl or vinyl halides and triflates, known as
the Stille reaction, has emerged into an extremely
powerful tool for carbon-carbon bond formation.1 It is
known2 that the use of cocatalytic copper(I) dramatically
enhances the reaction rate. In the copper effect, trans-
metalation of the R group from RSnBu3 to CuI was
suggested, and recent studies support the tin to copper
transmetalation.3 Recently, cross-coupling of organostan-
nanes with organic halides mediated by stoichiometric
amounts of copper alone was performed by Piers,4
Takeda,5 and Liebeskind.6 Falck et al.7 reported the
copper (I)-catalyzed cross-coupling of R-heteroatom-
substituted alkyltributylstannanes with organic halides.
Here, we now report the cuprous iodide- and manganese
bromide-catalyzed cross-coupling of organostannanes
with iodides in the presence of sodium chloride without
using palladium (eq 1).
CuI
MnBr2
MnBr2
MnBr2
MnBr2
MnBr2
20
10
trace
LiCl
CsF
10
a
Reaction conditions for CuI as catalyst: CuI (10 mol %), NMP,
90 °C, 7 h, salt (1 equiv). For MnBr2 as catalyst: MnBr2 (10 mol
b
%), NMP, 100 °C, 8 h, salt (1 equiv). As the catalyst, two kinds
of copper(I) iodide (99.999% from Aldrich Chem. Co.) and copper(I)
iodide (98% from J anssen Chimica.) can be used. c In the case of
NaCl and KCl, if 0.90 equiv of organostannane was used, the
d
homocoupled product was not detected with CuI. Of the man-
ganese catalysts tested, MnBr2 was the best choice, and with
MnCl2‚4H2O the yield was lower. The use of MnI2 did not give
the coupled product. e The yields of 4,4-dimethoxybiphenyl.
were the most preferable. The solvent DMF can be used
instead of NMP.8 In the experiment, it is necessary to
add organostannanes slowly via a syringe pump to avoid
the homocoupling of organostannanes.
The results of copper- and manganese-catalyzed cross-
coupling of organostannanes with organic iodides are
summarized in Table 2.9 Vinylstannane 1a was slowly
added via a syringe pump to (E)-â-styryl iodide (2a ) in
NMP at 100 °C over 1 h and then heated at reflux for 10
h in the presence of CuI (10 mol %) and 1 equiv of NaCl
to afford the diene 3a in 71% yield (method A in entry 1
in Table 2). Under the same conditions but with MnBr2
(10 mol %), the reaction gave the diene 3a in comparable
yield (method B). The addition of NaCl was crucial in
these cross-couplings. In considering the mechanistic
role of NaCl, it is presumed that the trasmetalation of
RSnBu3 with cuprate is reversible. By adding NaCl,
n-Bu3SnI formed from transmetalation of RSnBu3 with
CuI can be converted to n-Bu3SnCl, which does not
participate in a back-reaction with cuprate and thus
drives the transmetalation favorable, although the mech-
anism remains unclear.
The reaction of (E)-â-styryltributylstannane (1b) with
(E)-â-styryl iodide (2a ) in NMP at 120 °C proceeded
smoothly to give the (E,E)-diene 3b10 in 90% and 81%
yields, respectively (Methods A and B in entry 2, Table
2). Similarly, when the stannane 1b was treated with
(Z)-â-styryl iodide (2b) (E,Z)-diene 3c10 was provided
along with the (E,E)-diene 3b (33%) in 59% yield (Method
A in entry 3, Table 2). However, in the case of MnBr2
(method B in entry 3, Table 2), the (E,E)-diene 3b was
Initially, we have examined the copper-catalyzed cross-
coupling of 2-thienylorganostannane with p-iodoanisole
to determine optimum reaction conditions. A series of
experiments were performed, and the results are shown
in Table 1. The yields of the coupled product 3i are
highly dependent on the salts employed. Among the salts
tested, NaCl and KCl were the most suitable (Table 1,
entries 1 and 2). With KF and CsF as salts, the
homocoupled product 4 was formed. Accordingly, we
have tested manganese bromide as the catalyst to
discover a palladium-free Stille protocol, and the cross-
coupling of the organostannane 1d with iodide 2e has
been accomplished. Of the salts used, KCl and NaCl
† Dedicated to Professor Sang Chul Shim on the occasion of his 60th
birthday.
(1) (a) Stille, J . K. Angew. Chem., Int. Ed. Engl. 1986, 25, 508-
524. (b) Mitchell, T. N. Synthesis 1992, 803-815.
(2) Farina, V. Pure Appl. Chem. 1996, 68, 73-78.
(3) Behling, J .; Babiak, K.; Ng, J .; Campbell, A.; Moretti, R.; Koerner,
M.; Lipshutz, B. J . Am. Chem. Soc. 1988, 110, 2641-2643.
(4) Piers, E.; Romero, M. A. J . Am. Chem. Soc. 1996, 118, 1215-
1216 and references therein.
(8) In the copper-catalyzed alkylation of organomanganese chlorides,
the solvent THF/NMP (1:1) was used, and the influence of N-
methylpyrrolidone (NMP) was remarkable. See: Cahiez, G.; Marquais,
S. Synlett 1993, 45-46.
(9) In our hands, aryl bromides and triflates did not couple.
(10) Miyaura, N.; Yamada, K.; Suginome, H.; Suzuki, A. J . Am.
Chem. Soc. 1985, 107, 972-980.
(5) Takeda, T.; Matsunaga, K.; Kabasawa, Y.; Fujiwara, T. Chem.
Lett. 1995, 771-772.
(6) Allred, G. D.; Liebeskind, L. S. J . Am. Chem. Soc. 1996, 118,
2748-2749.
(7) Falck, J . R.; Bhatt, R. K.; Ye, J . J . Am. Chem. Soc. 1996, 117,
5973-5982.
S0022-3263(97)00656-7 CCC: $14.00 © 1997 American Chemical Society

Communications
Ta ble 2. Cop p er - a n d Ma n ga n ese-Ca ta lyzed
J . Org. Chem., Vol. 62, No. 13, 1997 4209
product in 88% yield (method A in entry 7, Table 2).
Under the same conditions wtih MnBr2 the coupling gave
3f in 85% yield (method B).11 For 2-thienylstannane (1d ),
treatment with 2a gave the coupled product 3g (entry 8,
Table 2). Alternatively, for aryl-aryl coupling, 2-thie-
nylstannane (1d ) was reacted with iodobenzene (2c) and
p-iodoanisole (2e) to give biaryls 3h and 3i (entries 9 and
10, Table 2).12-14 The p-diiodobenzene (2f) was reacted
with 2-thienylstannane 1d to afford bisthiophene 3j in
86% yield in method A and 86% in method B (entry 11,
Table 2). Similarly, 2-furylstannane 1e was successfully
coupled with 2a and 2e to furnish 3k and 3l (entries 12
and 13, Table 2). This method was also applied to the
coupling reaction of alkynyl-substituted organostan-
nanes. The alkynylstannane 1f was coupled with vinyl
iodide 2a and aromatic iodide 2c to afford the substituted
alkynes 3m and 3n , respectively (entries 14 and 15, Table
2).
Cr oss-Cou p lin g of Or ga n osta n n a n es w ith Or ga n ic
Iod id es
In summary, the cuprous iodide- and manganese
bromide-catalyzed cross-couplings of organostannanes
with iodides in NMP in the presence of NaCl were
accomplished without using palladium. We believe that
the methods described here may be valuable alternatives
to Stille coupling.
Ack n ow led gm en t. The generous financial support
of Ministry of Education (BSRI-96-3420) and KOSEF-
OCRC is gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and analytical data for the compounds (3 pages).
J O970656J
(11) The typical procedure is as follows. Method B: To a stirred
solution of 4-iodoanisole (2e) (200 mg, 0.85 mmol) and NaCl (50 mg,
0.85 mmol) in NMP (2 mL) was added MnBr2 (18.3 mg, 10 mol %), the
mixture was heated to 90 °C, and then tributylvinyltin (1a ) (0.27 g,
0.85 mmol) in NMP (2 mL) was added slowly for 1 h via a syringe
pump. The reaction mixture was stirred at 90 °C for 6 h and cooled to
rt, and saturated KF solution was added. The reaction mixture was
extracted with ether, and the organic layer was dried over anhydrous
MgSO4 and evaporated in vacuo. The crude product was separated
by SiO2 column chromatography (hexanes, Rf ) 0.25) to afford the
coupled product 3f (98 mg, 85%).
(12) The typical procedures is as follows. Method A: To a stirred
solution of 4-iodoanisole (2e) (200 mg, 0.85 mmol) and NaCl (50 mg,
0.85 mmol) in NMP (2 mL) was added CuI (16.2 mg, 10 mol %), the
mixture was heated to 90 °C, and then 2-(tributylstannyl)thiophene
(1d ) (320 mg, 0.85 mmol) in NMP (2 mL) was added slowly for 1 h via
a syringe pump. The reaction mixture was stirred at 90 °C for 8 and
cooled to rt, and saturated KF solution was added. The reaction
mixture was extracted with ether, and the organic layer was dried over
anhydrous MgSO4 and evaporated in vacuo. The crude product was
separated by SiO2 column chromatography (hexanes, Rf ) 0.28) to
afford the coupled product 3i (138 mg, 85%).
(13) In the MgBr2(10 mol %)-catalyzed coupling of organostannane
1d with iodobenzene (2c) (Table 2, entry 9, method B), we could get
the product 3h in 90% yield when DMF was used as solvent instead
of NMP.
a
Method A: CuI (10 mol %), NMP, NaCl (1 equiv). Method B:
MnBr2 (10 mol %), NMP, NaCl (1 equiv). b The yield of (E,E)-diene.
(14) In a control experiment for the reaction of organostannane 1d
with iodobenzene (2c) (Table 2, entry 9, Method A), when organostan-
nane 1d in NMP was added slowly for 1 h via a syringe pump, the
coupled product 3h was obtained in 92% yield. However, when
organostannane 1d was added in one portion, the coupled product 3h
was obtained in 60% yield along with the homocoupled product 4 (34%).
The cross-coupling by adding organostannane 1d slowly with DMF as
solvent was also carried out to give the coupled product 3h in 88%
yield.
obtained as a major product. The stannane 1b with
iodobenzene (2c) afforded the stilbene (3d ) in 88% yield
with CuI (10 mol %) (method A) and 80% yield with
MnBr2 (Method B in entry 4, Table 2). The stilbene (3d )
was readily obtained by reacting phenyltributylstannane
(1c) with the iodide 2a under similar conditions (methods
A and B) in 78 and 72% yields (entry 5, Table 2). This
method was also extended to aryl-aryl cross-coupling.
The arylstannane 1c was coupled with p-iodotoluene (2d )
to give unsymmetrical biphenyl 3e (method A, entry 6,
Table 2). Under similar conditions with MnBr2, biphenyl
3e was obtained (method B, entry 6, Table 2). With
p-iodoanisole (2e), the coupling reaction with 1a in the
presence of CuI gave p-methoxystyrene (3f) as the sole