Synthesis of functionalized diaryldimethylstannanes from the Me 2Sn2- dianion by SRN1 reactions

Article abstract of DOI:10.1021/jo0514422

The reaction of different ArCl with the Me₂Sn^2- dianion in liquid ammonia under irradiation afforded Ar₂SnMe ₂ in good yields (68-85%). The results obtained clearly indicate that the reaction proceeded through an S_RN1 reaction. As a synthetic application of these Ar₂SnMe₂, the homocoupling is described in the presence of Cu(NO₃)₂·2.5H ₂O to afford the biaryls. These reactions proceeded almost quantitatively.

Full text of DOI:10.1021/jo0514422

Synthesis of Functionalized
Diaryldimethylstannanes from the Me
Dianion by SRN1 Reactions
SCHEME 1
Sn2
-
2
Paula M. Uberman, Sandra E. Mart ´ı n,* and
Roberto A. Rossi*
INFIQC, Departamento de Qu ı´ mica Org a´ nica, Facultad de
Ciencias Qu ı´ micas, Universidad Nacional de C o´ rdoba,
C o´ rdoba, 5000, Argentina
-
-
from sulfides, such as S-R-S (R ) alkyl, aryl), reacted
3
4,5
with haloarenes and dihaloarenes. Other dianions
studied by electrochemical induced reactions were Se
2
-
2
2-
dianions.6
and Te
2
martins@mail.fcq.unc.edu.ar
Received July 12, 2005
Other types of dianions are those where the negative
charges are on only one heteroatom. By reaction with Na
metal in liquid ammonia elemental M (M ) P, As, Sb)
affords an “M ” species and reacts with PhX (X ) I, Cl)
3
under irradiation to form Ph M from fair to good yields.
3-
7
In addition, the dianion prepared in liquid ammonia
from elemental Se and Na metal reacts with haloarenes
-
to give (ArSe)
2
after oxidation of the ArSe ions inter-
The reaction of different ArCl with the Me2Sn2- dianion in
mediate, or it is trapped with MeI to afford ArSeMe in
8
2-
good yields. Similar results were obtained with Te
liquid ammonia under irradiation afforded Ar2SnMe2 in good
yields (68-85%). The results obtained clearly indicate that
the reaction proceeded through an SRN1 reaction. As a
synthetic application of these Ar2SnMe2, the homocoupling
is described in the presence of Cu(NO3)2‚2.5H2O to afford
the biaryls. These reactions proceeded almost quantitatively.
ions.8
We have described the photostimulated reactions of
-
Me
3
Sn ions with several ArCl in liquid ammonia that
from very good to excellent yields (70-
These stannanes are intermediates in Pd-
afforded ArSnMe
3
9,10
1
00%).
11,12
catalyzed cross-coupling reactions
and their synthesis
extends the scope and applications of the SRN1 mecha-
The radical nucleophilic substitution or SRN1 is a chain
process through which an aromatic nucleophilic substitu-
tion is obtained. The scope of the process has considerably
nism.
-
We hereby report the formation of the dianion Me
in liquid ammonia by the reaction of Me SnX
Br) and Na metal, and the novel use of this dianion in a
photostimulated reaction with ArCl to obtain Ar SnMe
As a synthetic application of the stannanes thus obtained,
2
Sn2
(X ) Cl or
increased, and nowadays it is an important synthetic1
2
2
possibility to achieve substitution of different substrates.
2
.
Several nucleophiles can be used such as carbanions and
anions from compounds bearing heteroatoms, which react
to form new C-C or C-heteroatom bonds in good yields.
Many substituents are compatible with the SRN1 mech-
2
the homocoupling of the Ar
reagents was carried out.
2 2
SnMe mediated by Cu
1
anism. This chain process requires an initiation step.
Biaryls are an important type of compound because of
their numerous applications.13 A variety of methods are
In a few systems, spontaneous electron transfer (ET) from
the nucleophile to the substrate has been observed. When
14,15
available for the aryl-aryl C-C bond formation.
The
the ET does not occur spontaneously, it can be induced
1
by light stimulation. The propagation steps of the SRN
1
(3) Beugelmans, R.; Ginsburg, H. Tetrahedron Lett. 1987, 28, 413-
14.
4
1
1
5
mechanism are presented in Scheme 1. Overall, eqs 1-3
depict a nucleophilic substitution in which radicals and
radical anions are intermediates (Scheme 1, eq 1-3).
Most of the nucleophiles studied are monoanions.
There are few reports on the reaction of 1,3-dianions from
â-dicarbonyl compounds that react quite well through the
(
4) Beugelmans, R.; Chbani, M.; Soufiaoui, M. Tetrahedron Lett.
996, 37, 1603-1604.
(5) Pierini, A. B.; Baumgartner, M. T.; Rossi, R. A. J. Org. Chem.
987, 52, 1089-1092.
(
6) (a) Thobie-Gautier, C.; Degrand, C. J. Org. Chem. 1991, 56,
703-5707. (b) Thobie-Gautier, C.; Degrand, C. J. Electroanal. Chem.
1993, 344, 383-387. (c) Degrand, C.; Prest, R.; Nour, M. Phosphorus
Sulfur 1988, 38, 201-209.
2
terminal carbon site under irradiation. Dianions derived
(
7) Bornancini, E. R. N.; Alonso, R. A.; Rossi, R. A. J. Organomet.
Chem. 1984, 270, 177-183.
*
Address correspondence to this author. Phone: 54-351-433-4170.
Fax: 54-351-433-3030.
1) For reviews, see: (a) Rossi, R. A.; Pierini A. B.; Pe n˜ e´ n˜ ory, A. B.
Recent Advances in the SRN1 Reaction of Organic Halides. In The
Chemistry of Functional Groups; Patai S., Rappoport, Z., Eds.; Wiley,
Chichester, UK, 1995; Supl. D2, Chapter 24, p 1395. (b) Rossi, R. A.;
Pierini, A. B.; Santiago, A. N. Aromatic Substitution by the SRN
Reaction. In Organic Reactions; Paquette, L. A., Bittman, R., Eds.;
999; Vol. 54, p 1. (c) Rossi, R. A.; Pierini, A. B.; Pe n˜ e´ n˜ ory, A. B. Chem.
(8) Rossi, R. A.; Pe n˜ e´ n˜ ory, A. B. J. Org. Chem. 1981, 46, 4580-4582.
(9) Yammal, C. C.; Podest a´ , J. C.; Rossi, R. A. J. Org. Chem. 1992,
57, 5720-5725.
(
(10) C o´ rsico, E. F.; Rossi, R. A. Synlett 2000, 227-229.
(11) C o´ rsico, E. F.; Rossi, R. A. J. Org. Chem. 2002, 67, 3311-3316.
(12) C o´ rsico, E. F.; Rossi, R. A. Synlett 2000, 230-232.
(13) (a) Papillon, J.; Schulz, E.; Gelinas, S.; Lessard, J.; Lemaire,
M. Synth. Met. 1998, 96, 155-160. (b) Yamamoto, T.; Maruyama, T.;
Zhou, Z.; Ito, T.; Fukada, T.; Yoneda, Y.; Begum, F.; Ikeda, T.; Sasaki,
S.; Takezoe, H.; Fukada, A.; Kubota, K. J. Am. Chem. Soc. 1994, 116,
4832-4845. (c) Bringmann, G.; Walter, R.; Weirich, R. Angew. Chem.,
Int. Ed. Engl. 1990, 29, 977-991.
1
1
Rev. 2003, 103, 71-168. (d) Rossi, R. A. In Synthetic Organic
Photochemistry; Griesberck, A. G., Mattay, J., Eds.; Marcel Dekker:
New York, 2005; Vol. 12, Chapter 15, pp 495-527.
(
2) (a) Bunnett, J. F.; Sundberg, J. E. J. Org. Chem. 1976, 41, 1702-
(14) (a) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire,
M. Chem. Rev. 2002, 102, 1359-1469. (b) Abiraj, K.; Srinivasa, G. R.;
Channe Gowda, D. Tetrahedron Lett. 2004, 45, 2081-2084.
1
3
706. (b) Wolfe, J. F.; Greene, J. C.; Hudlicky, T. J. Org. Chem. 1972,
7, 3199-3200.
1
0.1021/jo0514422 CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/27/2005
J. Org. Chem. 2005, 70, 9063-9066
9063

Ullmann coupling has been used for these purposes.16
Also, many improved methods of this reaction have been
2-
TABLE 1. Reaction of the Dianion Me2Sn (2) with
ArCl in Liquid Ammoniaa
14,17
18
17,19
developed.
Moreover, aryl boronic acid, aryl zinc,
20-25
as well as ArSnR
3
are frequently used in the homo-
coupling of aryls. Several methods based on Cu-mediated
or Cu-catalyzed coupling of stannanes have been re-
2
0b,21,22
23
ported.
Ar SnMe
by the reaction of aryllithiums with Me
more, the oxidative homocoupling of ArSnR
ful synthetic method to obtain symmetrical biaryls.
Recently, the Cu- and Mn-catalyzed homocoupling of
Iyoda et al. described the couplings of
with Cu where the Ar SnMe were prepared
SnCl . Further-
is a use-
2
2
2
2
2
2
substrate Me2Sn2
mmol)
-
yieldb
(%)
conditions (vol)
prod-
ucts
3
(
(mmol)
24
1
2
3
1 (1.6)
1 (1.6)
4a (0.4)
0.40 4 equiv Na (400 mL) 3
0.40 6 equiv Na (400 mL) 3
- (53)
93 (86)
c
25
ArSnR
Herein we report the homocoupling mediated by Cu-
NO of the Ar SnMe obtained from the dianion
Me Sn via the SRN1 reaction. The synthesis of Ar SnMe
2
3
in the presence of iodine has been achieved.
0.22 3 h, dark (200 mL)
5a
5a
4 4a (0.8)
0.44 3 h, hν (400 mL)
85 (63)
PhOMe 13
(
3
)
2
2
2
5 i.4a (19.6)
ii.4a (22.8)
6
7 4b (0.52)
8 4c (156)
19.7d
i. 1 h, hν (700 mL)e 5a
ii. 1 h, hν
- (59)
2-
2
2
was carried out in one step, which in most cases requires
two steps or lithium reagents.
When Me SnX (X ) Br or Cl) was treated with Na
2 2
metal in liquid ammonia, and the reaction was quenched
4b (0.52)
0.20 1 h, dark (200 mL)
0.20 1 h, hν (200 mL)
0.60 3 h, dark (400 mL)
5b
5b
5c
c
81 (63)
68 (63)
f
PhCN 10
9
4c (0.40)
0.20 3 h, dark, 10%
DTBN (250 mL)
0.55 3 h, hν (400 mL)
5c
5c
c
with benzyl chloride (1) to trap the dianion 2 formed, the
2 2 2
double substitution product Me Sn(CH Ph) (3) was
10 4c (1.0)
56 (40)
obtained in 93% yield (eq 4). It is important to notice that
PhCN 28
6
equiv of Na metal are needed to form 2. When only 4
11 6 (0.48)
0.30 3 h, dark (200 mL)
0.55 3 h, hν (400 mL)
7
c
12 6 (1.00)
7
68 (51)
27
equiv of the metal were used, only 53% of the isolated
Naph
10
9
product 3 was obtained (Table 1, entries 1 and 2).
1
3 8 (0.52)
4 8 (1.04)
0.20 2 h, dark (200 mL)
0.40 2 h, hν (400 mL)
- (96)
95
1
a
The dianion Me2Sn2- (2) was obtained from Me2SnX2 and 6
b
equiv of Na metal in dry liquid ammonia under nitrogen. By GC
with the internal standard method. Isolated yields in parentheses.
-
c
d
A dimeric species (Me
2
Sn) 2
2
may be formed as previ-
Substrate was recovered in almost 100% yield. The nucleophile
-
e
26
was the Me Sn ions. After the irradiation, 42 mmol of Na metal
ously proposed. Evidence of the presence of the dimmer
is the formation of the product (Me ArSn) in the SRN1
3
f
was added. Substrate 4c was recovered in 20% yield.
2
2
reactions carried out with the dianion obtained with 4
equiv of Na. When 6 equiv of Na metal was used, this
product was not practically observed. Even so the net
reaction requires 4 equiv of Na; the extra 2 equiv
consumed may be due to the loss of Na by reduction of
ammonia.
(
15) (a) Kang, S.-K.; Namkoong, E.-Y.; Yamaguchi, T. Synth. Com-
mun. 1997, 27, 641-642. (b) Stanforth, S. P. Tetrahedron 1998, 54,
2
63-303. (c) Miller, J. A.; Farrell, R. P. Tetrahedron Lett. 1998, 39,
441-6444. (d) Nagano, T.; Hayashi, T. Org. Lett. 2005, 7, 491-493
6
To evaluate the reactivity of 2 we allowed it to react
with ArCl in liquid ammonia under photostimulation.
There is no reaction of p-chloroanisole (4a) with 2 in dark
conditions; however, under irradiation it gave the double
substitution product 5a in good yields (Table 1, entries
and references therein. (e) Cahiez, G.; Chaboche, C.; Mauteau-Betzer,
F.; Ahr, M. Org. Lett. 2005, 7, 1943-1946.
(16) (a) Sainsbury, M. Tetrahedron 1980, 36, 3327-3359. (b) Fanta,
P. E. Synthesis 1974, 1, 9-21. (c) Ullmann, F.; Bielecki, J. Chem. Ber.
901, 34, 2174-2185.
17) Iyoda, M.; Kabir S. M. H.; Vorasingha, A.; Kuwatani, Y.;
Yoshida, M. Tetrahedron Lett. 1998, 39, 5393-5396.
18) (a) Basu, B.; Das, P.; Bhuiyan, M. H.; Jha S. Tetrahedron Lett.
1
(
27
3
and 4).
(
On the other hand, we have reported28 the synthesis
2
9
5
003, 44, 3817-3820. (b) Miyaura, N.; Suzuki, A. Chem. Rev. 1995,
5, 2457-2483. (c) Wallow, T. I.; Norak, B. M. J. Org. Chem. 1994,
9, 5034-5037. (d) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth.
of Ar SnMe through a two step-one pot procedure in
liquid ammonia. Substrate 4a was added to a solution of
2
2
Commun. 1981, 11, 513-519.
-
Me
3 3
Sn ions prepared from Me SnCl and Na metal, and
(
19) (a) Stanforth, S. P. Tetrahedron 1998, 54, 263-303. (b) Miller,
J. A.; Farrell, R. P. Tetrahedron Lett. 1998, 39, 6441-6444.
20) (a) Shirakawa, E.; Nakao, Y.; Murota, M.; Hiyama, T. J.
then irradiated for 1 h. Next, Na metal was added to
-
(
6 4 2
obtain the nucleophile (p-MeOC H )Me Sn ions. Sub-
Organomet. Chem. 2003, 670, 132-136. (b) Beddoes, R. L.; Cheeseright,
T.; Wang, J.; Quayle, P. Tetrahedron Lett. 1995, 36, 283-286. (c)
Farina, V.; Kapadia, S.; Krishnan, B.; Wang, C.; Liebeskind, L. S. J.
Org. Chem. 1994, 59, 5905-5911.
strate 4a was added again and irradiated for 1 h. The
double substitution product 5a was obtained in 59%
isolated yield (entry 5). The result obtained after the two
subsequent SRN1 reactions was similar to that obtained
with the dianion in one reaction (63%), but the later
reaction required less time and less experimental work.
Also, there was no reaction of p-chlorotoluene (4b) in
the dark; however, under irradiation, the disubstitution
product 5b was obtained in high yields (entries 6 and 7).
(
21) Piers, E.; Yee, J. G. K.; Gladstone, P. L. Org. Lett. 2000, 2, 481-
84.
22) Iyoda, M.; Kondo, T.; Nakao, K.; Hara, K.; Kuwatani, Y.;
4
(
Yoshida, M.; Matsuyama, H. Org. Lett. 2000, 2, 2081-2083.
(
23) Harada, G.; Yoshida, M.; Iyoda, M. Chem. Lett. 2000, 160-161.
(
24) (a) Piers, E.; Gladstone, P. L.; Yee, J. G. K.; McEachern, E. J.
Tetrahedron 1998, 54, 10609-10626. (b) Piers, E.; McEachern, E. J.;
Romero, M. A. Tetrahedron Lett. 1996, 37, 1173-1176. (c) Piers, E.;
Romero, M. A. J. Am. Chem. Soc. 1996, 118, 1215-1216. (d) Ghosal,
S.; Luke, G. L.; Kyler, K. S. J. Org. Chem. 1987, 52, 4296-4298.
(
25) Kang, S.-K.; Baik, T.-G.; Jiao, X. H.; Lee, Y.-T. Tetrahedron Lett.
999, 40, 2383-2384.
26) Kraus, C. A.; Greer, W. N. J. Am. Chem. Soc. 1925, 47, 2568-
575.
(27) The difference between GC and isolated yields is because part
of the stannanes decompose in the purification process.
(28) Yammal, C. C.; Podesta, J. C.; Rossi, R. A. J. Organomet. Chem.
1996, 509, 1-8.
1
(
2
9064 J. Org. Chem., Vol. 70, No. 22, 2005

TABLE 2. Homocoupling Reactions of Ar2SnMe2
Mediated by Cu(NO3)2 in THFa
The coupling of an asymmetrical stannane was studied
to know the scope of the homocoupling reactions. The
coupling of the asymmetrical phenyl(p-methoxyphenyl)-
dimethylstannane 12 in the same reaction conditions
described above led to three different products, one from
the cross coupling of the two aryls affording the asym-
metrical biaryl (57%) and two others corresponding to
the coupling of the same aryls themselves affording the
symmetrical biaryls (entry 6). No coupling products were
found in the reaction carried out with the benzylic
stannane 3 (entry 7). We only observed the oxidation
products.
time
yield
b
entry
substrate
(h)
products
11a
(%)
1
2
3
4
5a
5a
5a
5c
5c
2
67
71
99
70
86
12 11a
24 11a
24 11c
24 11c
c
5
We also carried out the one-pot reaction from 4a to the
biaryl 11a without isolation of the stannane. The proce-
dure was found to be possible. In this reaction the overall
yield was 42% of the biaryl 11a.
6
Me2SnPh(p-C6H4OMe) (12) 24 p-MeOC6H4-Ph 57
(
p-MeOC6H4)2
17
20
45
42
(
Ph)2
7
3
24 PhCHO
PhCH2OH
In conclusion, we developed a new approach to obtain
a
The reaction was carried out with 1 mmol of the stannane and
2 2
Ar SnMe and also an application of the stannanes
2
.8 mmol of Cu(NO3)2‚2.5H2O in 1 mL of THF at room tempera-
obtained. Even though the direct oxidative homocoupling
b
c
ture. Determined by GC. The reaction was carried out with 3.6
of Ar
described,
2
SnMe
2
to achieve the symmetrical biaryls was
this approach could be an interesting
mmol of Cu(NO3)2‚2.5H2O.
2
4,25
alternative in view that this method presents the advan-
tage that involves the use of less tin during the whole
process.
These reactions were carried out with an excess of
substrate with respect to the nucleophile. The results
obtained in this condition were practically the same as
those in the cases where an excess of nucleophile was
used.
Experimental Section
When p-chlorobenzonitrile (4c) and 2 were allowed to
react in the dark during 3 h, the substitution product 5c
was obtained in 63% yield (entry 8). This reaction was
completely inhibited by di-tert-butyl nitroxide (DTBN),
General Procedure for the Photostimulated Reaction
2
-
2
of Me Sn Dianion in Liquid Ammonia. The following
2
-
procedure of the reaction of 4a with Me
2
Sn
dianions is
representative of all the reactions. Into a three-necked, 500-mL,
round-bottomed flask equipped with a coldfinger condenser
charged with dry ice-ethanol, a nitrogen inlet, and a magnetic
stirrer was condensed 400 mL of ammonia previously dried with
Na metal under nitrogen. The Me SnBr (0.44 mmol) was added
1
a well-known inhibitor of SRN1 reactions (entry 9). The
fact that there is reaction in dark condition, but it is
inhibited by DTBN, is indicative that there is a sponta-
neous ET from 2 to 4c to initiate the SRN1 reaction. The
yield of 5c decreases under irradiation (40%) (entry 10).
No increase in the product yield was observed when the
reaction was carried out with an excess of the substrate.
There was no reaction of 1-chloronaphthalene (6) with
2
2
and then 6 equiv of Na metal (2.64 mmol) in small pieces,
waiting for bleaching between each addition. After 20-30 min
of the last addition 4a (0.80 mmol) was added and then
irradiated for 3 h. The reaction was quenched by adding
4 3
NH NO in excess, and the ammonia was allowed to evaporate.
The residue was dissolved in water and next extracted with
diethyl ether. The product 5a was quantified by GC, using the
internal standard method, yielding 85% of product. The product
2
in the dark. However, good yields of the disubstitution
product di(1-naphthyl)dimethylstannane (7) were ob-
tained under irradiation (entries 11 and 12). When the
potassium salt of 3-chlorobenzoic acid (8) was allowed to
react with 2 in dark conditions there was no reaction and
the 3-chlorobenzoic acid (10) was obtained in 96% yield
5
a was isolated by vacuum distillation by using a K u¨ gelrohr
apparatus, yielding 63% of the isolated product. Column chro-
matography seems to be an unsuitable purification method for
these stannanes, since they decompose in long contact with silica
1
13
gel. The product was characterized by H NMR, C NMR, and
GC-MS. All these spectroscopic date agreed with those reported
(
entry 13). The photostimulated reaction with the potas-
2
9
sium salt 8 gave only the reduction product benzoic acid
(
in the literature for this compound 5a, and for the other
2
9
30
31
1
13
stannanes obtained, 5b, 7, and 3. H NMR and C NMR
9) (entry 14).
spectra are provided in the Supporting Information.
On the other hand, as a synthetic application of the
Following the general method described above, 5c was
Ar
Ar
2
SnMe
2
obtained, the homocoupling reaction of
mediated by Cu(NO was carried out in THF.
1
obtained as a white crystalline solid (mp 118-119 °C). H NMR
2
SnMe
2
)
3 2
(
3
200 MHz, CDCl ): δ 7.40-7.75 (m, 8H), 0.61 (s, 6H, JSn-H
)
These reaction conditions are similar to the ones de-
56 Hz). 13C NMR (60 MHz, CDCl ): δ 147.0, 136.5 (J
) 39
3
Sn-C
scribed by Iyoda et al.;23 however, we used Cu(NO
.5H
coupling reactions are summarized in Table 2.
The homocoupling reaction of 5a mediated by Cu(NO
)
2
‚
Hz), 131.2 (JSn-C ) 47 Hz), 118.6, 112.6, -2.0. Mass spectra m/z
3
+
(
(
3
rel intensity): 352 (6) M , 339 (100), 252 (14), 222 (45), 120
2
2
O and the reaction required longer time. The
+
26), 103 (4). HRMS for C16
52.0182.
One-Pot Synthesis of 5a from Me
monia (Table 1, entry 5). To 800 mL of dry liquid ammonia
14 2
H N Sn (M ) 352.0179, found
)
3 2
3
SnCl in Liquid Am-
gave 4,4′-dimethoxybiphenyl (11a) in excellent yields
entries 1-3). With longer reaction time, the coupling
(
3
treated as before, the Me SnCl (19.7 mmol) was added and then
Na metal (43.5 mmol) in small pieces, waiting for bleaching
product yields were higher. The reaction needed 24 h to
be completed (entry 3). Also, with an electron withdraw-
ing substituent on the aromatic ring such as CN, 5c, the
homocoupling reaction took place (entry 4). To obtain
higher yields of the biaryl 11c (86%), more Cu(NO ) was
3 2
needed (entry 5).
(29) Thomas, J. C.; Peters, J. C. Inorg. Chem. 2003, 42, 5055-5073.
(
30) Mainwald, J.; Knapp, S.; Tatsvoka, T. Tetrahedron Lett. 1977,
2
6, 2247-2250.
31) De Boer, H. J. R.; Akkerman, O. S.; Bickelhaupt, F. J.
Organomet. Chem. 1987, 321, 291-306.
(
J. Org. Chem, Vol. 70, No. 22, 2005 9065

between each addition, to form Me
3
SnNa. Later, 4a (19.6 mmol)
Cl
2
CH
2
mixtures as eluants. The product was characterized by
1
13
was added to this solution and then irradiated for 1 h. The
equipment was taken from the photochemical reactor, and then
Na metal (38.4 mmol) was added to form the second nucleophile
H NMR, C NMR, and GC-MS. The spectroscopic date agreed
3
2
with those reported in the literature for this compound 11a,
and also for the product 11c.
3
3
(
p-anisyl)dimethylstannylsodium. Then, 4a (22.8 mmol) was
added to this solution, which was then irradiated for 1 h. The
reaction was quenched and treated as explained before. The
Acknowledgment. We would like to thank
CONICET, FONCYT, and SECYT, Universidad Nacio-
nal de C o´ rdoba, for their continuous support to our work
in this area. P.M.U. thanks CONICET for a fellowship.
2
9
product 5a was quantified by GC with use of the internal
standard method, yielding 59% of product.
Homocoupling Reaction of the Stannanes Mediated by
3 2 2
Cu(NO ) ‚2.5H O. The following procedure is representative of
Supporting Information Available: Experimental de-
all these reactions. Into a 10 mL reaction tube and a magnetic
stirrer, 1 mL of THF was added, and afterward the stannane
1
tails and characterization data of the stannane compounds ( H
13
NMR and C NMR spectra). This material is available free of
5
a (1 mmol). Next, the Cu(NO
to this solution, which was stirred at room temperature for 24
h. Then, water (20 mL) and Cl CH (20 mL) were added and
extracted three times with Cl CH . The product was quantified
3 2 2
) ‚2.5H O (2.8 mmol) was added
charge via the Internet at http://pubs.acs.org.
2
2
JO0514422
2
2
by GC, using the internal standard method, yielding 99% of 11a.
The biaryl product was isolated by radial thin-layer chromatog-
raphy with plates of 2 mm (silica gel 60 PF254), using hexanes-
(
32) Kuroboshi, M.; Waki, Y.; Tanaka, H. J. Org. Chem. 2003, 68,
3938-3942.
(33) Jutand, A.; Molesh, A. J. Org. Chem. 1997, 62, 261-274.
9066 J. Org. Chem., Vol. 70, No. 22, 2005