Sonochemical synthesis of bis(tri-n-butylstannyl) aromatic compounds via Barbier-like reactions

Article abstract of DOI:10.1016/j.jorganchem.2013.04.044

This paper reports a study of the synthesis of aryltri-n-butylstannanes via a sonochemical Barbier reaction of aryl- and heteroaryl bromides with bis(tri-n-butyltin) oxide (2) in THF. Our results demonstrate that, despite previous reports on contrary, the aryltributylstannanes can also be obtained under the same reaction conditions via sonicated reactions between aryl monobromides and tri-nbutyltin chloride (2). A comparative study of the reactions of electrophiles 2 and 3 with bromobenzene, 2-bromopyridin, o- and m-bromoanisole, m-bromotoluene, 9-bromophenthrene, and 9-bromoanthracene, indicates that the corresponding aryl- and heteroaryl-tri-n-butylstannyl derivatives are obtained in about the sameyields. Best reaction conditions and the results obtained in the investigation of the sonicated reactions between several aromatic and heteroaromatic dibromides are also reported. It was found that the reactions using 1,2-, 1,3-, and 1,4-dibromobenzenes, 4,40-dibromobiphenyl, 1,4-dibromonaphthalene, 2,5-and 3,5-dibromopyridines, and 2,5-dibromothiophene lead to the corresponding bis(tri-n-butylstannylated) derivatives in many cases in very high yields. Also the excellent results obtained in the sonicated reactions of 1,3,5-tribromobenzene with 2 and 3 are reported.

Full text of DOI:10.1016/j.jorganchem.2013.04.044

Journal of Organometallic Chemistry 741-742 (2013) 24e32
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Sonochemical synthesis of bis(tri-n-butylstannyl) aromatic
compounds via Barbier-like reactions
Darío C. Gerbino 1, Pablo M. Fidelibus, Sandra D. Mandolesi, Romina A. Ocampo 1,
1
,1
*
Jimena Scoccia , Julio C. Podestá
Instituto de Química del Sur (INQUISUR), Departamento de Química, Universidad Nacional del Sur-CONICET, Av. Alem 1253, 8000 Bahía Blanca, Argentina
a r t i c l e i n f o
a b s t r a c t
Article history:
This paper reports a study of the synthesis of aryltri-n-butylstannanes via a sonochemical Barbier re-
action of aryl- and heteroaryl bromides with bis(tri-n-butyltin) oxide (2) in THF. Our results demonstrate
that, despite previous reports on contrary, the aryltributylstannanes can also be obtained under the same
reaction conditions via sonicated reactions between aryl monobromides and tri-nbutyltin chloride (2).
A comparative study of the reactions of electrophiles 2 and 3 with bromobenzene, 2-bromopyridin,
o- and m-bromoanisole, m-bromotoluene, 9-bromophenthrene, and 9-bromoanthracene, indicates that
the corresponding aryl- and heteroaryl-tri-n-butylstannyl derivatives are obtained in about the same
yields. Best reaction conditions and the results obtained in the investigation of the sonicated reactions
between several aromatic and heteroaromatic dibromides are also reported. It was found that the re-
actions using 1,2-, 1,3-, and 1,4-dibromobenzenes, 4,40-dibromobiphenyl, 1,4-dibromonaphthalene, 2,5-
and 3,5-dibromopyridines, and 2,5-dibromothiophene lead to the corresponding bis(tri-n-butylstanny-
lated) derivatives in many cases in very high yields. Also the excellent results obtained in the sonicated
reactions of 1,3,5-tribromobenzene with 2 and 3 are reported.
Received 31 October 2012
Received in revised form
9 April 2013
Accepted 28 April 2013
Keywords:
Aryl- and heteroaryl bis(tri-n-
butylstannylated) compounds
Sonochemical synthesis
Bis(tri-n-butyltin) oxide and tri-n-butyltin
chloride electrophiles
Ó 2013 Published by Elsevier B.V.
1. Introduction
Some methods available for the synthesis of bis(stannylated)
aromatic compounds are the following. In first place the reaction
The synthesis of aromatic bis(stannylated) compounds is a very
important target due to their practical interest. These organotins
are valuable starting materials that enable the preparation of a wide
variety of organic and organometallic derivatives via known syn-
thetic procedures. For example, the StilleeMigita reaction [1], i.e.,
the reaction between alkyl halides and aryl- or vinyltins catalyzed
by Pd complexes that leads to the formation of new CeC bonds. This
reaction mainly involves the use of vinyl- and aryltins bearing
mostly only one organotin moiety. There are also some examples of
Stille reactions using bis- and tris-trimethylstannyl substituted
benzenes and pyridines [2]. Aromatic bis(stannylated) compounds
are also valuable starting material for the preparation of aryldi-
boronic acids via transmetalation with borane in THF [3].
The resulting aryldiboronic acids are widely used in polymer syn-
thesis [4] and also as starting material for Suzuki cross-coupling
reactions [5].
between aryl lithium or magnesium derivatives and trialkyltin
halides. However, the scope of these reactions is restricted to aro-
matic nucleus not containing functional groups that could react
with the organometallic reagents. The synthesis in 50% yield of 1,2-
bis(trimethylstannyl)benzene via a DielseAlder reaction between
bis(trimethylstannyl)ethyne and
a-pyrone, was first reported by
Seyferth et al. in 1966 [6a] who also described in 1977 the prepa-
ration of 1,8-bis(trimethylstannyl)naphthalene by reaction of 1,8-
dilithionaphthalene with trimethyltin chloride in tetraglyme [6b].
A much more straightforward approach to the synthesis of 1,2-
bis(trimethylstannyl)benzene (42% yield) via a nucleophilic aro-
matic substitution reaction of Me3SnNa with 1,2-dibromobenzene
in tetraglyme was described by Kuivila et al. in 1977 [7]. This
method was also used by Mitchell et al. to obtain various 1,2-
bis(trimethylstannyl)disubstituted aryl- and heteroaryl com-
pounds [8]. Jurkschat et al. [9] improved this method obtaining 1,2-
bis(trimethylstannyl)benzene in 67% yield. In 1992 it was reported
that the radical nucleophilic substitution (SRN1) of p-dichloroben-
zene with Me3SnNa in liquid ammonia gives the disubstitution
product, i.e., 1,2-bis(trimethylstannyl)benzene, in 88% yield [10].
Using the same photostimulated SRN1 reaction, in 2002 Rossi et al.
* Corresponding author.
E-mail address: jpodesta@uns.edu.ar (J.C. Podestá).
Member of CONICET, Argentina.
1
0022-328X/$ e see front matter Ó 2013 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.jorganchem.2013.04.044

D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
25
reported the synthesis of various bis(trimethylstannyl)pyridines in
high yields (80e88%), and also of 1,3,5-tris(trimethylstannyl)ben-
zene (71%) starting from the corresponding aromatic dichloro and
trichloro derivatives [11]. It should be noted that most of the
photostimulated SRN1 reactions have been performed using tri-
methyltin anions and a few with triphenyltin anions, and that no
examples of these reactions carried out using tri-n-butyltin anions
are found in the chemical literature. More recently, has been re-
ported the synthesis of bis(trimethyl-) and bis(tri-n-butylstanny-
lated) aromatic compounds in yields of 27e73% via distannylation
of arynes with hexamethyl- and hexa-n-butyldistannanes cata-
lyzed by palladium complexes [12].
On the other hand, in two papers published in 1996 and 1997
Lee and Dai reported the preparation of aryltributylstannanes via a
sonochemical Barbier reaction of aryl- and heteroaryl bromides
with bis(tri-n-butyltin) oxide (2) in THF [13]. Taking into account its
potential for the preparation of aromatic compounds containing
more than one tri-n-butylstannyl substituent, we considered it of
interest to carry out a study in order to determine the scope of this
sonochemical method.
spectrum of the crude mixture showed that the organotin species
present were 4 and hexa-n-butyldistannane (6). The formation of
distannane 6 in the reaction with electrophile 3 could arise from
the reaction of tri-n-butyltin chloride 3 with the stannylmagne-
sium compound (n-Bu3SnMgCl) formed via reaction of 3 with
Mg [1c].
We also found that under the same reaction conditions bis(-
trimethyltin) oxide, bis(tri-neophyltin) oxide, trimethyltin chloride,
and trineophyltin chloride do not react with phenyl bromide (1) to
give the corresponding substitution products.
We then studied the reaction of tin electrophiles 2 and 3 with 2-
bromopyridine, various bromoaromatic polycyclic hydrocarbons
and also with functionally substituted phenyl bromides. In all cases,
the substitution reactions took place with complete regiose-
lectivity. The results obtained are summarized in Fig. 1.
As shown in this figure, the reaction of 2-bromopyridine with
bis(tri-n-butyltin) oxide (2) led to the corresponding substitution
product, 2-(tri-n-butylstannyl)pyridine (7) in 83% yield, i.e., in
higher yield than that obtained by Lee et al. (65%) [13]. Fig. 1 also
shows that 2-bromopyridine reacts with tri-n-butyltin chloride (3)
leading to tin compound 7 in high yield.
In order to investigate the effect of functional substituents on
these reactions, we studied the reaction of substituted bromo-
benzenes with electrophiles 2 and 3 (Fig. 1). We found that the
sonicated reactions of m-bromoanisole and m-bromotoluene with
bis(tri-n-butyltin)oxide (2) lead in high yields to the corresponding
m-(tri-n-butylstannyl)anisole (9) (86%) and m-(tri-n-butylstannyl)
toluene (10) (82%) respectively. On the other hand, the reaction
with o-bromoanisole leads to o-(tri-n-butylstannyl)anisole (8) in
just 37% yield. Fig. 1 also shows that the reactions using tri-n-
butyltin chloride (3) follow the same pattern.
2. Results and discussion
In order to establish the best reaction conditions, we first
studied the reaction of bromobenzene (1) with bis(tri-n-butyltin)
oxide (2). In this case, the best yields were obtained as follows.
A solution of 1 (1 mmol), magnesium powder (1.1 mmol), electro-
phile 2 (1 mmol), 1,2-dibromoethane (0.5 mmol) in anhydrous THF
(5 mL), was sonicated under an Ar atmosphere during 45 min in a
commercial ultrasonic cleaning bath (Ultrasonic 104X) at medium
power (43e47 kHz) keeping the temperature at around 35 ꢀC.
Under these reaction conditions, phenyltri-n-butyltin (4) was ob-
tained in 83% yield (Scheme 1).
To establish the effect of the structure of the aryl group on these
reactions, we investigated the reactions of 9-bromophenanthrene
and 9-bromoanthracene with both electrophiles. As shown in
Fig. 1, the sonicated Barbier reactions of electrophiles 2 and 3 lead
In preliminary studies, the analysis by 119Sn NMR of the crude
mixture obtained in this reaction showed the formation of 4
together with tri-n-butyltin bromide (5). However, after passing a
solution of the crude product in ethyl acetate through a chro-
matographic column with silica gel doped with 10% of KF com-
pound 4 was obtained pure.
On the other hand, we found that, contrary to the reports of Lee
et al. [13], bromobenzene (1) reacts under the same experimental
conditions with tri-n-butyltin chloride (3) leading to the substitu-
tion product 4 in 78% yield (Scheme 1). In this case, the 119Sn NMR
Br
1
BrCH2CH2Br
Mg / THF
Product
N°
Isolated
Product
N°
Isolated
Electrophile
Electrophile
yield (%) a
yield (%) a
n-Bu3SnCl (3)
83
37
86
82
81
75
80
46
2
7
8
7
8
(n-Bu3Sn)2O (
)
77
61
80
60
9
9
(n-Bu3Sn)2O
n-Bu3SnCl
10
11
12
10
11
12
n-Bu3SnPh
n-Bu3SnPh + n-Bu3SnBr
+ (n-Bu3Sn)2
4
6
5
4
78 %
83 %
119Sn NMR -42.4 (Lit.14 -41.7 ppm)
a Pure compound after column chromatography
Scheme 1. Reaction of 1 with bis(tri-n-butyltin) oxide (2) and tri-n-butyltin chloride
(3).
Fig. 1. Aryl tri-n-butyltin products obtained in the sonicated reactions with tin elec-
trophiles 2 and 3.

26
D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
to the 9-(tri-n-butyl) substituted derivatives 11 and 12 respectively
with yields similar to those obtained in the previous reactions
(around 70e80%). The substitutions carried out using tri-n-tribu-
tyltin chloride (3) as electrophile took place in lower yields than
with electrophile 2.
spectrum of the crude product of the reaction between 21 and
bis(tri-n-butyltin)oxide (2) showed two big peaks at ꢁ35.9 ppm
and ꢁ36.2 ppm in a ratio 1:2 respectively, and also two very small
peaks at ꢁ40.9 ppm and ꢁ41.0 ppm. In the case of the reaction of 21
with tri-n-tributyltin chloride (3), the 119Sn NMR spectrum of the
crude product obtained indicated the formation of three com-
pounds with resonances at ꢁ35.9, ꢁ36.2, and ꢁ39.0 ppm with
approximately the same intensity, plus very small peaks with res-
onances at higher field. On the other hand, mass spectra of the
crude mixtures obtained in the reactions with both electrophiles
showed the formation of all the possible products of these re-
actions, i.e., compounds 22e26.
The only compound we were able to obtain pure via column
chromatography separation was methyl 2-tri-n-butylstannyl-5-
bromobenzoate (24). The assignment of the structure of com-
pound 26 was done making use of its NMR characteristics specially
nJ(1H,119Sn) and nJ(13C,119Sn) coupling constants. Although the other
compounds detected by mass spectrometry were not obtained
pure, taking into account that the 119Sn NMR shows a peak at
ꢁ36.1 ppm, i.e., very close to the one corresponding to the bro-
momonostannylated compound 24 (ꢁ35.9 ppm) and with the same
intensity, it might be possible that this compound could have the
structure 23 (Scheme 3). It should be stressed the fact that the 1H-
and 13C NMR spectra of these mixtures of organotin derivatives
indicated that the COOMe group remained unaffected.
The results obtained in the sonicated reactions of some aromatic
dibromo substituted polycyclic hydrocarbons with electrophiles 2
and 3 mediated by Mg are summarized in Scheme 5. As it can be
seen in Scheme 5, whereas the reaction of 4,40-dibromobiphenyl
(27) with bis(tri-n-butyltin) oxide (2) leads to a mixture of 4,40-
bis(tri-n-butylstannyl)biphenyl (28) and 4-(tri-n-butylstannyl)
biphenyl (29) in a ratio 28/29 ¼ 8.3, the reaction of 27 with elec-
trophile 3 leads exclusively to the bis(stannylated)biphenyl 28. It
should be noted that in the reactions with both electrophiles hexa-
n-butyldistannane (6) is also formed, and that the amount of 6
which is formed using tri-n-butyltin chloride (3) is higher. How-
ever, although the yields of distannylated compound 28 obtained
using electrophiles 2 and 3 are excellent, the column chromato-
graphic separation of distannane 6 is very difficult and diminishes
dramatically the yield of pure distannylated biphenyl 28. For the
same reason compound 29 could not be obtained pure.
In order to determine whether these reactions could also be of
preparative interest for the synthesis of aromatic bis(tri-n-butyltin)
derivatives, we carried out similar studies using as substrates
dibromo substituted aromatic molecules. The results obtained in
the sonicated reactions of dibromobenzenes with electrophiles 2
and 3 using ratios dibromo derivative/electrophile ¼ 1:3 under
Barbier conditions, are summarized in Scheme 2. These reactions
proceeded efficiently to give the corresponding bis(n-tributyl-
stannylated) compounds in high to excellent yields (Scheme 2). In
the reactions with both electrophiles, 2 and 3, it was observed the
formation of hexa-n-butyldistannane (6). The formation of ditin
compound 6 could arise from the reduction of bis(tri-n-butyltin)
oxide (2) with Mg [14]. Using electrophile 2, in the 119Sn NMR
spectrum of the crude products before the treatment with silica gel
doped with KF was also observed the formation of tri-n-butyltin
bromide (5).
In all these reactions was observed the formation of the
reduction product, i.e., phenyltri-n-butyltin (4). In some of the re-
actions carried out with bis(tri-n-butyltin)oxide (2) (Scheme 2), we
also determined the formation of monosubstitution’s products, i.e.,
phenyltri-n-butyltin bromides 18 and 20. The formation of aryl
bromides 18 and 20 clearly indicates that these substitutions take
place stepwise.
The formation of the reduction product 4 could be explained
taking into account that the fragmentation of the radical anion I,
product of the second electron transfer to 15, would lead to the
leaving group, i.e., the bromide anion and the aromatic radical
s II
(Scheme 3). The latter could then abstract a hydrogen atom from
the solvent (THF) leading to 4. It is to note that hydrogen abstrac-
tion from the solvent by aryl radicals is a possible termination
pathway when SRN1 reactions are carried out in organic solvents
[15].
It should be noted that using stoichiometrics amounts, i.e., ratio
dibromobenzene/tin electrophile ¼ 1:2, the composition of the
crude products changed dramatically. Thus, using stoichiometric
ratios in the case of 1,2-dibromobenzene (14) the mixtures ob-
tained consisted not only of compounds 4 and 16 but they also
included tri-n-butyl-2-bromophenyltin, i.e., the product of mono-
substitution. The latter is not formed using ratios 13/2 or 3 ¼ 1:3.
The previous results indicate that these sonicated Barbier-type
reactions could be extended to aryl dibromides leading to the
corresponding bis(tri-n-butylstannylated)benzenes in very good
yields. However, it should be noted the fact that in the case of the
1,2-dibromobenzene (13) the product of reduction 4 is formed in
much higher proportion than the desired 1,2-bis(tri-n-butyl-
stannyl)benzene (16). This might probably be connected with the
existence of steric hindrance.
The reaction between 1,4-dibromonaphthalene (30) with elec-
trophiles 2 and 3 leads in both cases exclusively to 1,4-bis(tri-n-
butylstannyl)naphthalene (31) and the compound was obtained
pure in high yield by column chromatography (Scheme 5). 13C NMR
spectroscopy enables a quick identification of compound 31. Thus,
the 13C NMR spectrum of 31 shows that the peak at 134.96 ppm
attributed to carbons C-2 and C-3 shows two satellite signals cor-
responding to 2J(119Sn,13C) and a 3J(119Sn,13C) coupling constants
with values of 26.8 and 45.0 Hz. respectively. These clearly
demonstrate that both carbons interact with the two tri-n-butyl-
stannyl groups attached to C-1 and C-4.
We then studied the reactions of methyl 2,5-dibromobenzoate
In the case of 9,10-dibromoanthracene (32), the 119Sn NMR
spectrum of the crude product obtained in the sonicated reaction
(21) with tin electrophiles 2 and 3 (Scheme 4). The 119Sn NMR
SnBu3
SnBu3
SnBu3
SnBu3
SET
Mg
SolvH
Solv
+
Br
+
4
Br
Br
II
20
I
Scheme 2. Mechanism of the reduction of compound 20.

D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
27
SnBu3
Br
SnBu3
Br
Mg / tin electrophile / THF
BrCH2CH2Br
4
+
119Sn: -41.9 ppm
SnBu3
16
13
SnBu3
Br
Mg / tin electrophile / THF
BrCH2CH2Br
4
+
+
SnBu3
Br
Br
14
17
18
119Sn: -43.3 ppm
119Sn: -37.7 ppm
a From 119Sn NMR spectrum. b Pure compound after column chromatography.
Reactions with (n-Bu3Sn)2O: substrate (1 mmol), Mg (3.3 mmol), (n-Bu3Sn)2O (3
mmol), 1,2-dibromoethane (0.5 mmol) in 5 ml of dry THF was sonicated 4 h. at r.t.
under argon. Reactions with n-Bu3SnCl: substrate (1 mmol), Mg (3.3 mol), n-Bu3SnCl
(3 mmol), 1,2-dibromoethane (0.5 mmol) in 5 ml of dry THF was sonicated 4 h. at r.t.
under argon.
Scheme 3. Barbier sonicated reactions of dibromobenzenes. Reactions with (n-Bu3Sn)2O: substrate (1 mmol), Mg (3.3 mmol), (n-Bu3Sn)2O (3 mmol), 1,2-dibromoethane (0.5 mmol)
in 5 mL of dry THF was sonicated 4 h. at r.t. under argon. Reactions with n-Bu3SnCl: substrate (1 mmol), Mg (3.3 mol), n-Bu3SnCl (3 mmol), 1,2-dibromoethane (0.5 mmol) in 5 mL of
dry THF was sonicated 4 h. at r.t. under argon.
with tri-n-butyltin chloride (3) showed it to consists of a mixture of
various organotin products, among them 9,10-distannylated com-
pound 33 (52%) and reduction compound 12 (6%). Using bis(tri-n-
butyltin)oxide (2) as electrophile, the reaction with 34 leads also to
a mixture of various organotin compounds in which, unexpectedly,
the reduction product 12 (36%) prevailed over the distannylated
compound 33 (26%). Unfortunately, we were not able to obtain
compound 33 pure from these mixtures.
It should be mentioned that we also studied the reactions of 2,4-
dibromo-1-methoxynaphthalene with electrophiles 2 and 3. The
119Sn NMR spectra of the crude product showed that these re-
actions lead to complex mixtures of organotin derivatives that we
could neither separate nor identify.
Due to the fact that bis(organotin)pyridine derivatives are very
important precursors for the synthesis of extended metal-
losupramolecular assemblies and polymers with grid-like archi-
tectures [16], we also investigated Barbier sonicated reactions of
some dibromo substituted aromatic heterocycles. However, it
should be noted that the preparation of bis(triorganostannyl)pyr-
idine compounds using the reaction between dibromopyridines
and n-butyllithium followed by trialkylstannylation at low tem-
perature has always been a difficult task, because of the time
consuming purification procedures and yields as low as 17% [17].
Taking into account the previous discussion, we investigated the
sonicated reactions of 3,5- (34) and 2,5-dibromopyridine (35) with
electrophiles 2 and 3. The obtained results are summarized in
Scheme 6.
As shown in Scheme 6, the sonicated reaction of 3,5-
dibromopyridine 34 with bis(tri-n-butyltin)oxide (2) leads to a
mixture of the known 3,5-bis(tri-n-butylstannyl)pyridine (36) [18] in
89% and 3-(tri-n-butylstannyl)pyridine (37) (11%), and the reaction
using tri-n-butyltin chloride (3) leads exclusively to the dis-
tannylpyridine 36. On the other hand, whereas the reaction of 2,5-
dibromopyridine 35 and electrophile 2 leads to a mixture of dis-
tannylated pyridine 38 (84%) and reduction’s product 37 (16%), the
reaction of 35 with 3 leads to a mixture of 37 and another organotin
compound. The column chromatography of the crude product of the
latter reaction afforded 37 (58%) pure, and mixtures of 37 with the
secondary organotin compound from which we were neither able to
separate nor to identify the latter.

28
D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
7
8
COOCH3
SnBu3
COOCH3
COOCH3
1
Br
SnBu3
2
6
5
+
+
3
COOMe
Bu3Sn
Bu3Sn
Br
4
24
119Sn: -35.9 ppm
22
Br
23
119Sn: -36.1 ppm
Mg / tin electrophile / THF
BrCH2CH2Br
+
Br
21
COOCH3
COOCH3
(n-Bu Sn) O and n-Bu SnCl
Tin electrophile =
3
2
3
SnBu3
+
Bu3Sn
25
26
13C-NMR dataa
C-5
Compound
C-1
C-2
C-3
C-4
C-6
C-7
C-8
24
145.9
(NO)
122.7
(NO)
138.5
(31.1)
134.71
(39.3)
137.4
132.8
(27.2)
167.9
(4.5)
52.6
b
a
In CDCl3
;
13C chemical shifts, δ, in ppm with respect to the central peack of CHCl3
(
13C spectra);
nJ(13C, 119Sn) coupling constants in Hz (in brackets). n-Butyl groups chemical shifts (coupling
b
constants): 29.3 (20.1); 27.5 (58.3); 13.8; 11.27 (363.6).
Scheme 4. Barbier sonicated reactions of methyl 2,5-dibromobenzoate (21) and 13C NMR characteristics of compound 24.
Another dibromo substituted aromatic heterocyclic compound
butylstannylated)aromatic compounds is similar to that founded in
other Stille reactions carried out with trimethylstannyl substituted
aromatic systems [21].
studied was 2,5-dibromothiophene (39). As shown in Scheme 7, the
only product of substitution obtained using compound 40 and
bis(tri-n-butyl)tin oxide (2) was the known 2,5-bis(tri-n-butyl-
stannyl)thiophene (41) [19] and also some distannane 6. Com-
pound 40 was isolated pure in 89% yield.
In conclusion, the results obtained demonstrate that, despite
initial reports indicating that tri-n-butyltin chloride (3) was not a
suitable tin electrophile for the Barbier sonicated substitutions of
aryl bromides, in fact in many cases it is the opposite, i.e., the use of
3 leads to bis(stannylated) products in excellent yields, even higher
than those obtained with electrophile 2. As for the effect of the
substituents, it was observed that in the case of aryl o-bromome-
thoxy and o-dibromo substituted compounds the yields of aryl tri-
n-butylsubstituted compounds are substantially lower. The re-
actions with dibromo substituted heterocycles lead to the corre-
sponding bis(tri-n-butylstannylated)heterocycles with excellent
yields. This is particularly important in the preparation of suitable
substrates for cross-coupling reactions leading to the synthesis of
extended metallosupramolecular assemblies and polymers. The
method and the work up are very simple, and enable the synthesis
of aromatic and heteroaromatic bis(tri-n-butylstannyl) substituted
derivatives with, in general, high global yields.
On the other hand, the reaction of 39 with the electrophile 3 led
a mixture of 40 and 2-(tri-n-butylstannyl)thiophene (41)
to
together with a high amount of distannane 6. It should be noted
that although the total yield was high we were not able to obtain
pure the monosubstituted compound 41 from the crude product
mixture.
The reactions of some tribromo substituted benzenes with
electrophiles 2 and 3 were also investigated. Thus, the reaction of
1,3,5-tribromobenzene (42) with electrophiles 2 and 3 leads to
mixtures in which, as shown in Scheme 8, 1,3,5-tris(tri-n-butyl-
stannyl)benzene (43) predominates largely.
However, the distannane 6 formed in these reactions precluded
us to obtain pure compounds 43 and 17 from the crude product
mixtures. The structures of these compounds were deduced from
the 1H-, 13C- and 119Sn NMR spectra and by mass spectrometry of
the mixtures.
It should be mentioned that we also carried out studies on the
sonicated Barbier reactions of 1,2,4-tetrabromobencene, 2,4,6-
tribromoanisol, and 1,6,8-tribromo-1-methoxynaphthalene with
electrophiles 2 and 3. However, the 119Sn NMR spectra of the crude
products obtained in these reactions showed them to consist of
various organotins. We were unable of obtaining pure any of the
compounds components of these mixtures.
Taking into account the previous results, we intend to carry out
new studies on the best reaction conditions in order to improve the
yields of the reactions of polybromo substituted aromatic com-
pounds, and also to develop a method for a more simple and effi-
cient separation of the hexa-n-butyldistannane (6).
3. Experimental
3.1. General methods
In order to test the chemical reactivity of the aryl- and hetero-
arylbispolytributylstannylated compounds, we carried out Stille
reactions with some of them. We found that the reaction between
1,4-bis(tri-n-butylstannyl)naphthalene (31) and p-iodotoluene
(Scheme 9) in THF in the presence of catalytic amounts of palladium
bis(triphenylphosphine) dichloride afforded the known 1,4-
ditolylnaphthalene (44) [5] in 71% yield.
Similarly, the reaction of 36 with p-bromoanisol in the presence
of the same catalyst leads to 3,5-di(p-anisyl)pyridine (45) [20] in
67% yield. These results indicate that the reactivity of the bis(tri-n-
1H, 13C and 119Sn NMR spectra were obtained in a Bruker ARX
300 instrument at 300 K, in 5 mm diameter tubes, using 10% (w/v)
solutions of the compounds and were recorded in CDCl3
(300.1 MHz for 1H, 75.5 MHz for 13C and 111.9 MHz for 119Sn).
Chemical shifts (d
) are given in ppm downfield relative to TMS (1H
and 13C), Me4Sn (119Sn) and coupling constants (nJ) are in Hz.
Infrared spectra were recorded with a Nicolet Nexus FT spectrom-
eter. Mass spectra were obtained with a GC/MS instrument (HP5-
MS capillary column, 30 m/0.25 mm/0.25
mm) equipped with

D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
29
Product
Isolated
Product
Isolated
Electrophile
Electrophile
N° (%) a yield (%) b
N° (%) a yield (%) b
28 (89)
29 (11)
55
--
28 (100)
82
--
27
--
31 (100)
84
--c
--c
31 (100)
33 (52)
86
--c
--c
(n-Bu3Sn)2O
30
32
n-Bu3SnCl
33 (22)
12 (61)
12 (6)
a
b
c
From 119Sn NMR spectrum. Pure compound after column chromatography. Could not be
separated pure.
Compound
13C-NMR data a
Compound
13C-NMR data a
28
31
C-1 & C-1’
140.90 (387.6)
137.02 (30.5)
C-1 & C-4
143.54 (386.5)
C-2, C-2’,
C-6. & C-6’
C-2 & C-3
134.96 (26.8 & 45.0)
C-3, C-3’,
C-5 & C-5’
126.72 (40.9)
141.03 (29.2)
C-5 & C-8
C-6 & C-7
131.42 (28.3)
C-4 & C-4’
125.32
n-Bu
9.84 (343.1); 13.83; C-9 & C-10
139.62 (27.5)
27.20 (56.2); 29.31
(20.3).
n-Bu
10.68 (338.8); 13.77;
27.69 (56.6); 29.42 (18.4)
a
In CDCl3
CHCl3 (13C spectra); nJ(13C, 119Sn) coupling constants in Hz (in brackets).
;
13C chemical shifts, δ, in ppm with respect to the central peack of
Scheme 5. Barbier sonicated reactions of 4,40-dibromobiphenyl (27), 1,4-dibromonaphthalene (30) and 9,10-dibromanthracene (32), and 13C NMR characteristics of the new
compounds 28 and 31.
5972 mass selective detector operating at 70 eV (EI). Melting points
were determined in a Kofler hot stage and are uncorrected. High
resolution mass spectra (HRMS) were recorded on a Finnigan Mat.
900 (HReEIeMS). Solvents were dried and distilled in accordance
with standard procedures. The reactions were performed under an
argon atmosphere using an NDI ULTRASONIC 104X bath operating
at 43e47 kHz at 35 ꢀC (ꢂ1 ꢀC). They were monitored by thin-layer
chromatography on silica gel plates (60F-254) and visualized under
UV light and/or using 5% phosphomolybdic acid in ethanol. Column
chromatography was performed over silica gel 60 (70e230 mesh)
doped with 10% of potassium fluoride [22]. Except dibromo sub-
strates 29 [23], 32 [24] and 34 [25] which were obtained by known
procedures, the mono-, di-, and tri-substituted substrates used in
these studies were commercially available and used as purchased.
3.2. Synthesis of arylstannanes via sonochemical Barbier reactions
All the reactions were carried out under an argon atmosphere
and following the same procedure. The reaction flask was located in
the water bath of the ultrasonic cleaner, and the temperature of the

30
D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
Product
Isolated
Product N° Isolated
Electrophile
Electrophile
N° (%) a yield (%) b
(%) a
yield
(%) b
36 (89)
37 (11)
65
--
36 (100)
55
--
34
35
37
(n-Bu3Sn)2O
n-Bu3SnCl
38 (84)
37 (16)
70
--
--
38
c
37
58
a
From 119Sn NMR spectrum. b Pure compound after column chromatography.c Plus other unidentified
organotin compound.
13C-NMR dataa
Compound
C-2
C-3
C-4
C-5
C-6
n-Bu
38
172.91
(504.5)
157.89
(30.8 &
57.2)
141.49
(21.8 &
29.4)
137.41
(NO)
132.67
(24.4)
9.71 (346.4); 9.81 (349.2); 13.58;
13.62; 27.29 (57.9); 27.32 (55.2);
29.00 (21.2); 29.06 (22.9).
a
In CDCl3
119Sn) coupling constants in Hz (in brackets).
; (
13C chemical shifts, δ, in ppm with respect to the central peack of CHCl3 13C spectra); nJ(13C,
Scheme 6. Barbier sonicated reactions of 3,5-dibromopyridine (34) and 2,5-dibromopyridine (35), and 13C NMR characteristics of compound 38.
bath was controlled using the water circulation flow of a thermo-
stat. One experiment is described in detail in order to illustrate the
methods used.
and 1,2-dibromoethane (0.094 g, 0.5 mmol) as initiator in dry THF
(5 mL) was sonicated for 1 h in an ultrasonic cleaning bath at
around 35 ꢀC, with monitoring of the reaction by TLC. Once the
reaction finished, aqueous saturated NH4Cl solution (40 mL) was
added and extracted with ethyl acetate (3 ꢃ 20 mL). The combined
extracts were washed with brine (60 mL) and dried over anhydrous
magnesium sulfate. The solvent was removed under reduced
3.2.1. Reactions with bis(tri-n-butyltin) oxide (2)
A mixture of magnesium turnings (0.027 g, 1.1 mmol), bromo-
benzene (0.15 g, 1 mmol), bis(tri-n-butyltin) oxide (0.60 g, 1 mmol)
Product
Isolated
Product
Isolated
Electrophile
Electrophile
N° (%) a yield (%) b
N° (%) a yield (%) b
40 (61)
41 (39)
55
-
(n-Bu3Sn)2O
40 (100) 89
n-Bu3SnCl
a From 119Sn NMR spectrum. b Pure compound after column chromatography.
+
Mg / tin electrophile / THF
Br
Br
Bu3Sn
SnBu3
SnBu3
BrCH2CH2Br
S
S
S
39
40
41
119Sn: -40.1 ppm
119Sn: -38.5 ppm
Scheme 7. Barbier sonicated reactions of 2,5-dibromothiophene (39) with electrophiles 2 and 3.

D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
31
Product
N° (%) a
Product
N° (%) a
Electrophile
Electrophile
43 (93)
17 (7)
43 (88)
17 (12)
(n-Bu3Sn)2O
n-Bu3SnCl
a From 119Sn NMR spectrum..
13C-NMR dataa
Compound
C-1, C-3, & C-5C-4
C-2, C-4, & C-6
144.56 (27.8)
n-Bu
43
141.25 (27.2 & 376.9)
9.83 (313.2); 13.88; 27.63 (54.4); 29.41 (20.5)
a
In CDCl3
119Sn) coupling constants in Hz (in brackets).
;
13C chemical shifts, δ, in ppm with respect to the central peack of CHCl3 13C spectra); nJ(13C,
(
Scheme 8. Barbier sonicated reactions of 1,3,5-tribromobenzene (42) with electrophiles 2 and 3, and 13C NMR characteristics of compound 38.
pressure and the crude product was purified by column chroma-
tography with silica gel doped with 10% of KF to retain the tri-n-
butyltin bromide formed during the reaction. 4 eluted with 95:5
(hexane/diethyl ether as an oil (0.304 g, 0.83 mmol, 83%, b.p. 137e
139 ꢀC/0.6 mmHg, (lit [26] b.p. 125e128 ꢀC/0.14 mmHg))). 119Sn
3.3. Physical and spectroscopic characteristic of the aryl tri-n-
butyltin obtained
The synthesis and physical characteristics of the following
compounds have already been reported: 2-tri-n-butylstannylpyr-
idine (7) (commercially available), 2-tri-n-butylstannylanisole (8)
[27], 3-Tri-n-butylstannylanisole (9) (commercially available), 3-
Tri-n-butylstannyltoluene (10) (commercially available), 9-tri-n-
butylstannylphenanthrene (11) [28], 9-tri-n-butylstannylan-
thracene (12) [28], 1,2-bis(tri-n-butylstannyl)benzene (16) [12], 1,3-
bis(tri-n-butylstannyl)benzene (17) [29], 1,4-bis(tri-n-butylstannyl)
benzene (20) [30], 4-(tri-n-butylstannyl)biphenyl (29) (commer-
cially available), 3,5-bis(tri-n-butylstannyl)pyridine (36) [17], 3-
(tri-n-butylstannyl)pyridine (37) (commercially available), 2-tri-n-
butylstannylthiophene (41) (commercially available), and 2,5-
bis(tri-n-butylstannyl)thiophene (42) [19].
NMR (CDCl3):
d
ꢁ42.4 ppm.
3.2.2. Reactions with tri-n-butyltin chloride (3)
A mixture of magnesium turnings (0.036 g, 1.5 mmol), bromo-
benzene (0.15 g, 1 mmol), tri-n-butyltin chloride (0.49 g, 1.5 mmol)
and 1,2-dibromoethane (0.094 g, 0.5 mmol) as initiator in dry THF
(5 mL) was sonicated for 1 h in an ultrasonic cleaning bath at
around 35 ꢀC, with monitoring of the reaction by TLC. Once the
reaction finished, aqueous saturated NH4Cl solution (40 mL) was
added and extracted with ethyl acetate (3 ꢃ 20 mL). The combined
extracts were washed with brine (60 mL) and dried over anhydrous
magnesium sulfate. The solvent was removed under reduced
pressure and the product was isolated by column chromatography
with silica gel doped with 10% of KF to retain tri-n-butyltin halides
formed during the reaction. 4 (0.286, 0.78 mmol, 78%) eluted with
98:2 (hexane/diethyl ether).
3.3.1. Methyl 5-bromo-2-(tri-n-butylstannyl)benzoate (24)
Colorless oil. 1H NMR (CDC13) 8.24 [d, 1H, 4J(H,H) 1.9]; 7.63 [dd,
d
1H, 4J(H,H) 1.9 & 3J(H,H) 7.8]; 7.51 [d, 1H, 3J(H,H) 7.8]; 3.93 (s, 3H);
1.65e0.96 (m, 18H); 0.88 [t, 9H, 3J(H,H) 6.9]. IR (film, cmꢁ1) 3028
Scheme 9. Barbier sonicated reactions of 1,3,5-tribromobenzene (42) with electrophiles 2 and 3.

32
D.C. Gerbino et al. / Journal of Organometallic Chemistry 741-742 (2013) 24e32
(d) A.G. Davies, M. Gielen, K. Pannell, E. Tiekink, Tin Chemistry: Fundamentals,
Frontiers and Applications, first ed., John Wiley & Sons, Ltd, West Sussex,
United Kingdom, 2008;
(e) P.J. Smith (Ed.), Chemistry of Tin, second ed., Blackie Academic & Profes-
sional, London, 1998.
(m), 2955 (s), 2910 (s), 2871 (s), 2850 (s), 1727 (s), 1600 (m), 1464
(s), 1240 (s), 1050 (s), 880 (s), 830 (m), 710 (s). HRMS (EI) calcd. for
C
C
20H33BrO2Sn2 504.0683, found 504.0678. Anal. calcd. for
20H33BrO2Sn2: C, 47.65; H, 6.60, found: C, 47.60; H, 6.55.
[2] (a) Y. Yang, H.N.C. Wong, Tetrahedron 50 (1994) 9583e9608;
(b) Y. Yamamoto, Y. Azuma, H. Mitoh, Synthesis (1986) 564e565;
(c) S. Gronowitz, D. Peters, Heterocycles 30 (1990) 645e658;
(d) T. Otsubo, Y. Kono, N. Hozo, H. Miyamoto, Y. Aso, F. Ogura, T. Tanaka,
M. Sawada Bull, Chem. Soc. Jpn. 66 (1993) 2033e2041;
(e) J.J.S. Lamba, J.M. Tour, J. Am. Chem. Soc. 116 (1994) 11723e11726;
(f) E.F. Córsico, R.A. Rossi, Synlett (2000) 230e232;
3.3.2. 4,40-Bis(tri-n-butylstannyl)biphenyl (28)
Colorless oil. 1H NMR (CDC13):
d 7.47 (m, 8H); 1.49 (m, 12H), 1.16
(m, 24H), 0.82 [t, 18H, 3J(H,H) 7.1]. IR (film, cmꢁ1) 3025 (m), 2960
(s), 2920 (s), 2870 (s), 2851 (s),1605 (m),1460 (s), 803 (s). HRMS (EI)
calcd for C36H62Sn2 734.2895, found 734.2889. Anal. calcd. for
(g) A.N. Santiago, S.M. Basso, J.P. Montañez, R.A. Rossi, J. Phys. Org. Chem. 19
(2006) 829e835.
C
36H62Sn2: C, 59.05; H, 8.53, found: C, 59.09; H, 8.57.
[3] (a) M.B. Faraoni, L.C. Koll, S.D. Mandolesi, A.E. Zúñiga, J.C. Podestá,
J. Organomet. Chem. 613 (2000) 236e238.(b) S.D. Mandolesi, S.E. Vaillard,
J.C. Podestá, R.A. Rossi, Organometallics 21 (2002) 4886e4888.
[4] (a) T.M. Miller, T.X. Neenan, R. Zayas, H.E. Bair, J. Am. Chem. Soc. 114 (1992)
1018e1025;
(b) J.M. Tour, J.J.S. Lamba, J. Am. Chem. Soc. 115 (1993) 4935e4936;
(c) A.B. Morgan, J.L. Jurs, J.M. Tour, J. Appl. Polym. Sci. 76 (2000) 1257e1268.
[5] P.M. Fidelibus, G.F. Silbestri, M.T. Lockhart, S.D. Mandolesi, A.B. Chopa,
J.C. Podestá, Appl. Organomet. Chem. 21 (2007) 682e687.
[6] (a) A.B. Evnin, D. Seyferth, J. Am. Chem. Soc. 89 (1967) 952e959;
(b) D. Seyferth, S.C. Vick, J. Organomet. Chem. 141 (1977) 173e187.
[7] (a) K.R. Wursthorn, H.G. Kuivila, G.F. Smith, J. Am. Chem. Soc. 100 (1977)
2779e2789;
(b) K.R. Wursthorn, H.G. Kuivila, J. Organomet. Chem. 140 (1977) 29e39.
[8] T.N. Mitchell, K. Böttccher, P. Bleckmann, B. Costisella, Ch. Schwittek, Eur. J.
Org. Chem. (1999) 2413e2417.
[9] R. Altmann, K. Jurkschat, M. Schürmann, D. Dakternieks, A. Duthie, Organo-
metallics 17 (1998) 5858e5866.
[10] C.C. Yammal, J.C. Podestá, R.A. Rossi, J. Org. Chem. 57 (1992) 5720e5725.
[11] E.F. Córsico, R.A. Rossi, Synlett (2000) 227e229.
[12] H. Yoshida, K. Tanino, J. Ohshita, A. Kunai, Angew. Chem. Int. Ed. 43 (2004)
5052e5055.
3.3.3. 1,4-Bis(tri-n-butylstannyl)naphthalene (31)
Colorless oil. 1H NMR (CDC13):
7.89 (m, 2H), 7.58 (m, 4H),
1.68(m, 12H), 1.38 (m, 24H); 0.98 [t, 18H, 3J(H,H) 7.2]. IR (film, cmꢁ1
d
)
3031 (m), 2955 (s), 2915 (s), 2880 (s), 2850 (s), 1600 (m), 1455 (s),
805 (s). HRMS (EI) calcd for C34H60Sn2 708.2739, found 708.2734.
Anal. calcd. for C34H60Sn2: C, 57.82; H, 8.56, found: C, 57.86; H, 8.60.
3.3.4. 2,5-Bis(tri-n-butylstannyl)pyridine (38)
Colorless oil. 1H NMR (CDC13)
d
8.25 [dd, 1H, 4J(H,H) 0.8 &
3J(H,Sn) 18.5]; 7.51 [dd, 1H, 3J(H,H) 7.6 & 3J(H,Sn) 34.1]; 7.35 [dd, 1H,
4J(H,H) 0.8 & 3J(H,H) 7.6]; 1.56 (m, 12H); 1.26 (m, 24H); 0.85 [t, 18H,
3J(H,H) 7.2]. IR (film, cmꢁ1) 3032 (m), 2962 (s), 2915 (s), 2880 (s),
2848 (s), 1573 (m), 1603 (m), 1460 (s), 850 (s), 713 (s). HRMS (EI)
calcd for C29H57NSn2 659.2535, found 659.2542. Anal. calcd. for
C
29H57NSn2: C, 53.00; H, 8.74, found: C, 53.06; H, 8.67.
[13] (a) A.S.-Y. Lee, W.-Ch. Dai, Tetrahedron Lett. 37 (1996) 495e498;
(b) A.S.-Y. Lee, W.-Ch. Dai, Tetrahedron 53 (1997) 859e868.
[14] B. Jousseaume, E. Chanson, M. Pereyre, Organometallics 5 (1986) 1271e1272.
[15] R.A. Rossi, A. Pierini, A.N. Santiago, Org. React. 54 (1999) 1e271.
[16] (a) J.A. Joule, K. Mills, Heterocyclic Chemistry, fifth ed., Wiley-VCH, Weinheim,
2010;
(b) J. Jack Li, G.W. Gribble, Palladium in Heterocyclic Chemistry: a Guide for
the Synthetic Chemist, second ed., Elsevier, Oxford, 2007.
[17] M.V. Nora de Souza, R.H. Dodd, Heterocycles 47 (1998) 811e827.
[18] G.S. Hanan, U.S. Schubert, D. Volkmer, E. Riviere, J.-M. Lehn, N. Kyritsakas,
J. Fischer, Can. J. Chem. 75 (1997) 169e182.
3.3.5. 1,3,5-Tris(tri-n-butylstannyl)benzene (43)
Clear oil. 1H NMR (CDC13):
d
7.39 (s, J ¼ 37.5 Hz, 3H), 1.64e1.58
(m, 36H), 1.45e1.33 (m, 18H), 0.91 (t, J ¼ 8.0 Hz, 27H). 13C NMR
(CDCl3): d 144.4 (27.9),141.1 (28.7 and 381.1), 29.2 (19.1), 27.4 (60.0),
13.7, 9.9 (360.7). 119Sn NMR (CDCl3):
d
ꢁ44.4. IR (film, cmꢁ1) 3027
(m), 2961 (s), 2910 (s), 2885 (s), 2850 (s), 1600 (m), 1462 (s), 865 (s),
820 (s), 710 (s).
[19] (a) J. Hou, Z. Tan, Y. Yan, Y. He, Ch. Yang, Y. Li, J. Am. Chem. Soc. 128 (2006)
4911e4916;
Acknowledgments
(b) X. Guo, M.D. Watson, Org. Lett. 10 (2008) 5333e5336.
[20] B. Balasubrahmanyam, I. Jeyashri, N. Namboothiri, Tetrahedron 50 (1994)
8127e8142.
[21] (a) J.K. Stille, Angew. Chem. Int. Ed. Engl. 25 (1986) 508e524;
(b) V. Farina, V. Krishnamurthy, W.J. Scott, Org. React. 50 (1997) 1e652.
[22] E. Ferrer Flegeau, M.E. Popkin, M.F. Greaney, J. Org. Chem. 73 (2008) 3303e3306.
[23] R.S. Schreiber, W. Bradley Reid Jr., R.W. Jackson, Org. Synth. Coll. 4 (1963)
256e257.
[24] O. Cakmak, I. Demirtas, H.T. Balaydin, Tetrahedron 58 (2002) 5603e5609.
[25] H.T. Clarke, T.F. Murray, Org. Synth. Coll. 1 (1941) 207e208.
[26] H. Gilman, S.D. Rosenberg, J. Am. Chem. Soc. 75 (1953) 2507e2509.
[27] C. Bolm, M. Ewald, M. Felder, G. Schingloff, Chem. Ber. 125 (1992) 1169e1173.
[28] (a) Weisemann, G. Schmidtberg, H.-A. Brune, J. Organomet. Chem. 365 (1989)
403e412;
This work was supported by grants from ANPCyT (Capital Fed-
eral, Argentina/BID 1728/OC-AR PICT Nꢀ 2467), CONICET (Buenos
Aires, Argentina), and Universidad Nacional del Sur (Bahía Blanca,
Argentina). Fellowships from CONICET to PMF and JS are
acknowledged. A postdoctoral fellowship to DCG and a grant for a
short scientific visit to Germany to JCP from the Alexander von
Humboldt Foundation are also gratefully acknowledged
References
(b) H. Nierengarten, J. Rojo, E. Leize, J.-M. Lehn, A. Van Dorsselaer, Eur. J. Inorg.
Chem. (2002) 573e579.
[29] (a) S. Kool, L.S. Liebeskind, J. Am. Chem. Soc. 117 (1995) 3389e3404;
(b) M.E. Wright, Organometallics 8 (1989) 407e411.
[1] (a) T.N. Mitchell, in: F. Diederich, P.J. Stang (Eds.), Metal-catalyzed Cross-
coupling, Wiley-VCH, Weinheim, Germany, 1998, pp. 167e202;
(b) V. Farina, V. Krishnamurthy, W.J. Scott, The Stille Reaction, John Wiley &
Sons Ltd, New York, 1998;
[30] S.M. Moerlein, J. Organomet. Chem. 319 (1987) 29e39.
(c) A. Davies, Organotin Chemistry, VCH, Weinheim, Germany, 2004;