Trimethylstannylation of mono- and dichloroarenes by the SRN1 mechanism in liquid ammonia

Article abstract of DOI:10.1002/poc.1046

The photostimulated reaction of methyl 2,5-dichloro benzoate (1) or methyl 3,6-dichloro-2-methoxy benzoate (7) with ^-SnMe₃ ions give good yields of the disubstitution products by the S_RN1 mechanism in liquid ammonia. Conversely, in dark conditions, substrate 1 reacts with ^-SnMe3 ions to afford the mono-substitution products by the S _RN1 mechanism. On the other hand, substrate 7 reacts with ^-SnMe₃ ions in dark conditions to give mono-reduced product probably by a halogen metal exchange reaction. In addition, the photostimulated reaction of 2-chloro-N⁴-ethyl-N⁶- isopropyl-1,3,5-triazin-4,6-diamine (Atrazine, 11) with ^-SnMe ₃ ions affords the reduced and substitution products in liquid ammonia-DMSO as co-solvent. Copyright

Full text of DOI:10.1002/poc.1046

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
J. Phys. Org. Chem. 2006; 19: 829–835
Published online 3 November 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/poc.1046
Trimethylstannylation of mono- and dichloroarenes by
y
the S 1 mechanism in liquid ammonia
RN
Ana N. Santiago,* Silvana M. Basso, Juan P. Monta n˜ ez 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, Ciudad Universitaria, 5000
C o´ rdoba, Argentina
Received 12 November 2005; revised 28 December 2005; accepted 30 December 2005
ABSTRACT: The photostimulated reaction of methyl 2,5-dichloro benzoate (1) or methyl 3,6-dichloro-2-methoxy
ꢀ
benzoate (7) with SnMe ions give good yields of the disubstitution products by the SRN1 mechanism in liquid
3
ꢀ
ammonia. Conversely, in dark conditions, substrate 1 reacts with SnMe ions to afford the mono-substitution
3
ꢀ
products by the SRN1 mechanism. On the other hand, substrate 7 reacts with SnMe ions in dark conditions to give
3
mono-reduced product probably by a halogen metal exchange reaction. In addition, the photostimulated reaction of
4
6
ꢀ
-chloro-N -ethyl-N -isopropyl-1,3,5-triazin-4,6-diamine (Atrazine, 11) with SnMe ions affords the reduced and
3
2
substitution products in liquid ammonia-DMSO as co-solvent. Copyright # 2006 John Wiley & Sons, Ltd.
ꢀ
KEYWORDS: SRN1 reactions; radicals; SnMe ions; chloroarenes; Disugran; Atrazine
3
INTRODUCTION
(
ArX)
Nu
Ar
+
X
(1)
(2)
The radical nucleophilic substitution, or SRN1 reaction, is
a chain process with radicals and radical anions as
intermediates, through which an aromatic nucleophilic
substitution is obtained. The scope of the process has
considerably increased, and nowadays it is an important
synthetic possibility to achieve substitution of different
Ar
ArNu)
+
(ArNu)
(
+
ArX
ArNu + (ArX)
(3)
Scheme 1
1
substrates. Several nucleophiles can be used, such as
carbanions and anions from compounds bearing heteroa-
toms, which react to form new C—C or C-heteroatom
bonds in good yields.
solvent, and on the reaction conditions. We have
described the photostimulated reactions of trimethyl-
stannyl ions ( SnMe ) with several chloroarenes in liquid
3
ꢀ
This chain process requires an initiation step. The most
frequently used methods for initiation are chemical
initiation by alkali metals in liquid ammonia, electro-
chemical initiation at a cathode, and photoinitiation. In a
few systems a thermal (spontaneous) initiation is
observed. The propagation steps of an SRN1 mechanism
are presented in Scheme 1.
The wide variety of nucleophiles that can be used, the
great functional group tolerance and the fact that many
carbon–carbon and carbon–heteroatom bonds can be
obtained, makes the SRN1 reaction a powerful synthetic tool.
The reaction of triorganostannyl ions as nucleophiles
with aryl halides has long been known, and the products
obtained depend on the leaving group, the nucleophile,
ammonia that afford ArSnMe3 from very good to
2
excellent yields (70–100%). The fact that there is no
reaction in the dark but only under irradiation, and that the
photostimulated reactions are inhibited by p-dinitroben-
zene (p-DNB), a well-known inhibitor of SRN1 reactions,
indicates that these reactions occur by the SRN
1
mechanism. These reactions are an alternative route to
the synthesis of stannanes, avoiding the use of Grignard
reagents or organolithium compound. These reactions can
3
also be carried out in DMSO as solvent under irradiation.
The SRN1 reactions of dihaloarenes with nucleophiles
afford either the monosubstitution or disubstitution
product, depending on the structure of the substrate,
and the nature of the nucleofugal group or the
nucleophile. We found that several dichloroarenes give
the disubstitution product in high yields [Eqn (4)]. Also,
dichloropyridines react to afford disubstituted products.
*
Correspondence to: A. N. Santiago, Departamento de Qu ´ı mica Org a´ -
nica, Facultad de Ciencias Qu ´ı micas, Universidad Nacional de
C o´ rdoba, Ciudad Universitaria, 5000-C o´ rdoba, Argentina.
E-mail: santiago@mail.fcq.unc.edu.ar
The photostimulated reaction of 1,3,5-trichlorobenzene
ꢀ
y
in the presence of an excess of SnMe ions affords 71%
3
Dedicated to Professor Norma Sbarbati Nudelman. This article is
published as part of the special issue Festschrift for Norma Nudelman.
4
of the trisubstitution product.
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

8
30
A. N. SANTIAGO ET AL.
Cl
SnMe3
reaction was assumed to be aromatic nucleophilic
substitution (S Ar). In another study, the effect of free
N
11
hv / NH3
+
2
-SnMe3
(4)
radical inhibitors on the reaction rate of polysulfides was
evaluated with the herbicides Atrazine, Simazine, and
Cyanazine. The reaction was significantly inhibited by
radical scavengers, such as oxygen and 1,4-benzoqui-
none, suggesting involvement of free radicals in the
reactions. Spectral analysis of the reaction mixture using
electron spin resonance showed that after the reaction, the
free radical concentration in polysulfide solution sub-
stantially decreased. This evidence indicates that sulfur
centered radicals may also be involved in the reaction,
Cl
SnMe3
8-96%
5
Mono- and distannanes can also be formed from
diethylaryl phosphonates or aryltrimethyl ammonium
5
,6
7
,8
salts by the SRN1 mechanism. It has been demonstrated
ꢀ
that haloarenes react in diglyme with SnMe ions under
3
8
irradiation by the SRN1 mechanism.
A simple method to synthesize five-substituted
12
likely via the SRN1 mechanism.
In order to synthesize different substituted herbicides we
resorcinol derivatives has been published. 1-Chloro-
ꢀ
3,5-dimethoxybenzene reacts with the SnMe ions in
liquid ammonia under irradiation to afford substitution
decided to investigate the reaction of chloro-substituted
ꢀ
3
herbicides with SnMe ions by the SRN1 mechanism in
3
9
product in good yields [Eqn (5)].
liquid ammonia. This approach provides a facile prep-
aration of compounds bearing trimethylstannyl groups.
The synthesis of these stannyl derivatives is of great
interest since this group is readily changed by electro-
philes, generating a new C—C bond and increasing the
synthetic value of these reactions.
Cl
SnMe3
hv / NH3
-SnMe
(5)
+
3
MeO
OMe
MeO
OMe
80%
ꢀ
The SRN1 reactions of SnMe ions with haloarenes
3
are quite versatile. The reaction products are of prominent
synthetic relevance and can be utilized as intermediates in
RESULTS AND DISCUSSION
8
,9,10
important reactions, such as the Stille reaction.
A
Reactions of methyl-2,5-dichlorobenzoate (1)
S
sequence of SRN1 followed by a cross-coupling reaction
catalyzed by Pd(0) has been developed to obtain
polyphenylated compounds as shown in Eqn (6).
Following the same procedure, 1,3,5-triphenylbenzene
was obtained in 61% isolated yield from 1,3,5-trichlor-
with SnMe
3
ions in liquid ammonia
We studied methyl 2,5-dichlorobenzoate (1) as a model
compound of certain chlorinated herbicides. It was found
ꢀ
that 1 reacts with the SnMe
ions in liquid ammonia
under irradiation to afford disubstitution product (2) and
3
10
obenzene in a one-pot procedure.
only trace of other substitution product (3 and 4).
ꢀ
Cl
However, in the dark, 1 reacted with SnMe ions to give
3
Ph
1
. hv / NH3
the mono-substitution product 3 in 81% yield [Eqn (7)]
(Table 1, experiments 1 and 2).
Z
-SnMe3
Z
+
2
(6)
2
. PhI, Pd(PPh ) Cl
DMF, 80 C
3 2 2
0
Cl
Cl
SnMe3
Ph
hv / NH3
Z= CH, m-: 76%
Z= CH, p-: 71%
Z= N, 2,6-: 60%
-SnMe
+
2
(7)
3
CO Me
2
CO Me
2
Cl
1
SnMe3
2
Although dehalogenation by a halogen metal exchange
HME) takes place with iodoarenes and 2- and 3-
chlorothiophene, good yields of substitution are found
Me Sn
3
Me Sn
3
(
+
+
CO Me
2
3
CO Me
2
H
with 2- and 3-chloropyridines in DMSO.
2
Cl
4
-chloro-N -ethyl-N -isopropyl-1,3,5-triazin-4,6-dia-
6
3
4
mine (known as Atrazine) or 3,6-dichloro-2-methoxy
benzoic acid (known as Dicamba) are among the most
widely used chlorinated herbicides in different countries.
These compounds are relatively stable under natural
conditions and have become prominent contaminants in
soil and hydrologic systems.
The dark reaction is not inhibited by p-DNB, but it is
inhibited by radical scavengers as di-ter-butyl nitroxide
(Table 1, experiments 3 and 4).
Moreover, the photostimulated reaction of 1 in excess
ꢀ
with SnMe ions rendered the products 2, 3, and 4 in
3
It was previously reported that chloro-s-triazine was
rapidly dechlorinated in water by polysulfides, and the
32%, 50%, and 10% yields, respectively. The fact that
the monochloro substitution product 3 was formed
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

TRIMETHYLSTANNYLATION
831
ꢀ
reacts with SnMe ions to form the radical anion 3
3
[Eqn (9)]. This radical anion 3 by intermolecular
electron transfer (ET) to the substrate affords the
monosubstitution product 3 [Eqn (10)], or by intramo-
ꢁS
Table 1. Reaction of methyl 2,5-dichlorobenzoate (1) with
ꢀ
a
ꢁS
SnMe ions in liquid ammonia
3
ꢀ
1
:
SnMe3 Conditions
Ratio
b
Experiment
(min)
Products (%)
ꢁ
lecular ET to the second C—Cl bond forms the radical 6
ꢀ
1
1:2.2
hn, (60)
2 (99), 3 (traces),
(traces)
Dark (60) 2 (2), 3 (81), 4 (<2)
[Eqn (11)], which by coupling with SnMe ions affords
3
ꢁ
S
4
the radical anion of the disubstitution product 2 , which
by an ET reaction yields the disubstitution product
2 [Eqn (12)].
2
1:2.2
1:2.2
1:2.2
1:1.1
c
d
3
4
Dark (60) 2 (6), 3 (76), 4 (19)
Dark (60) 2 (—), 3 (9), 4 (1)
hn, (60)
e,f
g
5
2 (32), 3 (50), 4 (10)
The fact that the monosubstitution product 3 is formed
indicates that the intermolecular ET of the radical anion
a
ꢀ3
The concentration of substrate was 6.66 ꢃ 10 M. The concentration of
ꢁS
ꢂ
ꢀ2
3
s MO of the C—Cl bond [Eqn (11)]. The intermediate
[Eqn (10)] is faster than intramolecular ET to the
nucleophile was 1.4 ꢃ 10 M, unless otherwise indicated.
b
Quantified by GLC by the internal standard method with p-dibromoben-
zene as reference.
stannane 3 further reacts by the SRN1 mechanism with
ꢀ
c
p-DNB (20 mol%) was added.
Together with hydrolyzed compound (ca. 1:1)
d
SnMe ions to give finally the disubstitution product 2
3
e
Di-ter-butyl nitroxide (20 mol%) was added.
Substrate and hydrolyzed substrate recovered in 61%.
[Eqn (13)].
f
g
ꢀ3
The concentration of nucleophile was 7 ꢃ 10 M.
indicates that this product is an intermediate in the reac-
tion (Table 1, experiment 5).
Reactions of methyl 3,6-dichloro-
2-methoxybenzoate
S
These results suggest that 1 reacted by the SRN1
mechanism, as shown in Scheme 2. When 1 receives one
(7) with SnMe ions in liquid ammonia
3
ꢁꢀ
electron it gives a radical anion intermediate 1 which
fragments at one of the C—Cl bond to give a radical
Methyl 3,6-dichloro-2-methoxybenzoate (7), know as
Disugran, is the methyl ester of the herbicide Dicamba.
Substrate 7 reacts under photostimulation with SnMe
ꢁ
ꢁ
ꢀ
intermediate 5 [Eqn (8)]. This radical intermediate 5
3
ions in liquid ammonia to give the substitution products
8 and 9, and the reduced product 10 in 64%, 6%, and 3%
yields, respectively [Eqn (14)]. This reaction affords
principally 10 in the dark (Table 2, experiments 1 and 2).
.
hv / NH3
-
.
1
1
-SnMe
(8)
- Cl-
3
CO Me
2
ET
Cl 5.
SnMe3
OMe
Cl
OMe
hv / NH3
-
+
2 SnMe
(14)
3
-
.
Me Sn
CO Me
2
3
CO Me
2
5.
+ SnMe
-
(
9)
3
Cl
SnMe3
7
8
Cl
CO Me
2
Cl
-
.
Me Sn
3
OMe
CO Me
3
OMe
+
+
-
.
-
.
inter ET
2
3
+ 1
3
+ 1
(10)
CO Me
2
H
Cl
9
10
Me Sn
3
-
.
intra ET
(11)
3
-
-
Cl
CO Me
2
.
The photostimulated reaction was carried out in the
presence of high excess of nucleophile in order to obtain
the best conditions by the coupling reaction; however, the
yield of the reduced product 10 increases. The fact that at
higher concentration of the nucleophile, the reaction
affords 10 and that the substitutions products (8 and 9) are
formed in lower yields, suggest that the reduction process
proceeds by a HME reaction [Eqn (15)] in competition
with the SRN1 reaction, with a very fast protonation of the
6.
SnMe3
-SnMe3
inter ET
(12)
6.
2
CO Me
2
SnMe
3
-
.
2
-SnMe3
hv / NH3
-SnMe3
ET
ꢀ
6.
2
(13)
aromatic anion 10 formed by liquid ammonia (Table 2,
3
ET
experiment 3). The compound 7 reacts by an HME
reaction faster compared to by the SRN1 mechanism in
dark condition.
Scheme 2
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

8
32
A. N. SANTIAGO ET AL.
Table 2. Reaction of methyl 3,6-dichloro-2-methoxybenzo-
ꢀ
a
ate (7) with SnMe ions in liquid ammonia
HN
N
NH
hv / NH3 HN
N
NH HN
+
N
NH
3
-SnMe3
(16)
ꢀ
N
N
N
N
N
N
7:
SnMe3 Conditions
Ratio
Products
(%)
b
Experiment
(min)
Cl
SnMe3
c
1
1
12
13
1
1:3.2
1:3.2
1:6.2
1:1.1
hn, (60) 8 (64), 9 (6), 10 (3)
Dark (60) 8 (8), 9 (4), 10 (73)
c,d
2
3
4
hn, (60)
hn, (60)
8 (38), 9 (35), 10 (15)
8 (34), 9 (29), 10 (—)
e
f
ꢀ
Table 3. Reaction of Atrazine (11) with SnMe3 ions in
a
a
ꢀ3
The concentration of substrate was 6.66 ꢃ 10 M. The concentration of
liquid ammonia
ꢀ
2
nucleophile was 1.4 ꢃ 10 M, unless otherwise indicated.
b
ꢀ
Quantified by GLC by the internal standard method with p-dibromoben-
zene as reference.
11: SnMe3 DMSO Conditions
b
Experiment
ratio
1:1.1
1:1.1
1:1.1
1:1.1
1:1.1
1:3.2
1:3.2
1:3.2
(mL)
(min)
Products (%)
c
The concentration of nucleophile was 2.1 ꢃ 10ꢀ2 M.
d
Relative yields. Substrate recovered in 14%.
The concentration of nucleophile was 6.66 ꢃ 10 M.
1
2
3
4
—
6
hn, (150)
hn, (150)
hn, (210)
Dark (210)
hn, (210)
hn, (150)
hn, (150)
Dark (150)
12 (—),
13 (—)
12 (26),
e
f
ꢀ3
Together with hydrolyzed compound.
1
3 (40)
12 (14),
3 (39)
12 (—),
3 (—)
4
1
4
1
c
Cl
5
4
12 (—),
13 (—)
12 (56),
-SnMe3
OMe
NH3
(
15)
7
10
d
-
6
6
-
ClSnMe3
- NH2
CO Me
2
1
3 (—)
12 (43),
3 (—)
12 (—),
-
d
7
1
1
0-
1
d
8
1
13 (—)
a
-3
The concentration of substrate and nucleophile were 3.33 ꢃ 10 M, unless
In addition to this, the photostimulated reaction of 7 in
excess with SnMe ions rendered the disubstitution 8 and
monochloro substitution product 9 in 34% and 29% yields,
respectively. The reduced product 10 was not formed in this
experimental condition (Table 2, experiment 4).
ꢀ
otherwise indicated.
b
3
Relative yields. Substrate recovered in all reactions.
p-DNB (20 mol%) was added.
c
d
ꢀ3
The concentration of substrate was 3.33 ꢃ 10 M. The concentration of
ꢀ2
nucleophile was 1.0 ꢃ 10 M.
The photostimulated reaction was performed in the
presence of an excess of nucleophile in order to obtain the
best conditions by the coupling reaction; however,
reduced product 12 was obtained exclusively. The fact
that the higher concentration of nucleophile affords 12
and that the reaction was inhibited by p-DNB suggest that
reaction proceeds by a radical process but the coupling
reaction is not efficient. Atrazine reacts by a reduction
reaction faster than by the SRN1 mechanism when
an excess of nucleophile was used (Table 3, experiments
6–8).
S
Reactions of Atrazine (11) with SnMe ions in
liquid ammonia
3
4
-chloro-N -ethyl-N -isopropyl-1,3,5-triazin-4,6-dia-
6
2
mine (11) (Atrazine) is an herbicide used as a selective
herbicide on corn and by control broadleaf and grassy
weeds. It is effectively non-toxic to birds but readily
the gastrointestinal tract. It is slightly toxic to fish and
other aquatic life, though low bioaccumulation. It can be
absorbed orally, dermal, and by inhalation and it is
slightly to moderately toxic to humans and other animals.
It has potential for groundwater contamination.
Finally, the fact that photostimulated reactions of 11
ꢀ
with SnMe afforded the reduction and substitution
3
products, and this reaction did not occur in the dark, and
both reactions were inhibited by p-DNB is indicative that
11 reacts with this anion by an ET process (Scheme 3).
When 11 receives an electron it forms its radical anions,
Substrate 11 is quite insoluble in liquid ammonia, and
ꢀ
no reaction occurs under irradiation with SnMe ions. In
3
order to improve the solubility, 11 was added with a small
amount of DMSO. In this experimental condition, 11
ꢁ
which fragment to afford radical 14 [Eqn (17)]. This
radical intermediate has two competing processes:
ꢀ
reacts under photostimulation with SnMe ions to give
3
ꢀ
the reduction and substitution products 12 and 13 in 26%
and 40% yields, respectively [Eqn (16)]. This reaction did
not occur neither without a little volume of DMSO nor in
the dark conditions. The photostimulated reaction was
inhibited by p-DNB (Table 3, experiments 1–5).
coupling with SnMe ions to afford the substitution
3
product 13 [Eqn (18)], or being reduced to product 12
[Eqn (19)].
The fact that the main product is the reduction product
12 is indicative that the coupling reaction of the radical
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

TRIMETHYLSTANNYLATION
833
results can be of great interest to obtain these compounds
as precursors in organic synthesis.
hv / NH3
-SnMe3
ET
-
.
HN
N
NH
11
11
(17)
- Cl-
N
N
.
.
EXPERIMENTAL
Methods
14
-SnMe3
.
.
ET
-.
1
4
13
1
3
(18)
reduction
1
4
12
(19)
Irradiation was conducted in a reactor equipped with
two 400-W UV lamps emitting maximally at 350 nm
Scheme 3
(Philips Model HPT, water-refrigerated). The HRMS
were recorded at UCR Mass Spectrometry Facility,
University of California, United States.
.
HN
N
NH
Materials
.
N
N
N
N
:
.
14
Methyl 2,5-dichlorobenzoate, Dicamba, Atrazine, tri-
methylstannyl chloride and potassium t-butoxide
.
.
.
1
5
16
(KOtBu) were commercially available and used as
received. DMSO was distilled under vacuum and stored
Scheme 4
˚
under molecular sieves (4 A). Liquid ammonia was
distilled under nitrogen and Na metal, and used
immediately.
ꢁ
4 with the anion is not efficient, probably due to
electronic reasons, and the radicals are reduced to 12.
1
It has been determined that the coupling rate of 2-
ꢁ
ꢀ
7
ꢀ
quinolyl radical (15 ) with OP(EtO) and CH COMe
2
2
7
ꢀ1 ꢀ1
ions (2.6 ꢃ 10 and 1.0 ꢃ 10 M s , respectively) are
Preparation of methyl 3,6-dichloro-2-
methoxybenzoate (7)
substantial lower than the coupling rate of 4-quinolyl
ꢁ
9
radicals (16 ) with the same nucleophiles (1.6 ꢃ 10 and
9
ꢀ1 ꢀ1
5
.4 ꢃ 10 M s , respectively). These observations
The 3,6-dichloro-2-methoxybenzoic acid (1 g, 4.5 mmol)
was added to 0.5 g., 4.5 mmol of KOtBu dissolved in
25 mL of dry DMSO. Then, the reaction was quenched
with a 0.8 mL, 12.5 mmol of methyliodide. The solution
was dissolved with water and then extracted with diethyl
ether. The product was isolated as yellow oil and
identified by GC/MS. Identified by comparison with
were rationalized by the existence of an electronic
repulsion between the lone pair electrons on the nitrogen
ꢀ
14
and the electrons of the Nu . This repulsion contributes
ꢁ
to decrease the coupling rate (Scheme 4). Radical 14 has
two lone pairs which decrease the coupling rate with the
nucleophile even more.
15
NIST Mass Spec Data of bibliography.
CONCLUSIONS
Photostimulated reactions of 1 and 7
S
Aryltrimethyl stannanes are valuable intermediates in
organic syntheses, and the fact that they can be easily
synthesized through the SRN1 mechanism opens up
important synthetic routes, such as stannanes intermedi-
ates in cross coupling reaction with different electrophiles
catalyzed by palladium. These SRN1 reactions are
compatible with many functional groups compared to
the drastic experimental conditions of other trimethyl-
stannylation reactions.
with SnMe ions in liquid ammonia
3
The following procedure is representative of these
reactions. Me SnCl (2.2 mmol or 3.2 mmol, respectively)
and then Na metal (5.3 mmol or 7.7 mmol respectively,
20% excess) in small pieces were added to 150 mL of
distilled ammonia, until total decoloration between two
3
consecutive additions, and 20 min after the last addition,
ꢀ
when no more solid was present, SnMe ions were ready
3
We have reported the conversion of different substrates
ꢀ
for use (lemon yellow solution). The substrate 1 or 7
(1 mmol) was added to the solution, and the reaction
mixture was irradiated. Then, the reaction was quenched
with an excess of ammonium nitrate, and the ammonia
was allowed to evaporate. The residue was dissolved with
water and then extracted with diethyl ether. The products
were isolated by column chromatography. In the other
to aryltrimethylstannanes by reaction with SnMe3
ions under irradiation. Thus, disubstituted methyl 2,5-
bis(trimethylstannyl)benzoate (2, 99%), methyl 2-meth-
oxy-3,6-bis(trimethylstannyl)benzoate (8, 64%), and
2
4
substituted
1
N -ethyl-N -isopropyl-6-trimethylstannyl-
,3,5-triazin-2,4-diamine (13, 40%) were obtained. These
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

8
34
A. N. SANTIAGO ET AL.
experiments the products were quantified by GLC using
the internal standard method.
Methyl 2-methoxy-3,6-bis-trimethylstannanylbenzo-
ate (8): Isolated as a white solid after column
chromatography on silica gel, eluted with pentane. Mp:
1
6
2.5–63.5 8C. H-NMR (CDCl ) d: 0.27 (9H, s,
3
S
Photostimulated reactions of 11 with SnMe
ions in liquid ammonia
JH–Sn ¼ 54.2 Hz); 0.33 (9H, s, J
¼ 55.2); 3,77 (3H,
3
H–Sn
s); 3.93 (3H, s); 7.33–7.36 (1H, d, J
¼ 6.8 Hz);
3
H–Sn
13
7
.51–7.54 (1H, d, JH–Sn ¼ 6.8). C-NMR (CDCl ) d:
The procedure was similar to that for the previous
reaction, except from the fact that Me SnCl (1.2 mmol)
ꢀ8.64; ꢀ7.60; 52.33; 62.71; 129.12; 131.37; 137.08;
139.30; 148.38; 164.59; 169.98. EM (EIþ) m/z (%): 479
(76), 477 (100), 475 (94), 445 (19), 430 (3), 415 (19), 385
(7); 230 (17), 214 (11), 165 (6), 151 (7). HRMS (CI) exact
mass calcd for C H O Sn (—CH ) 478.9691, found
3
and then Na metal (2.6 mmol, 20% excess) in small pieces
was added to 300 mL of distilled ammonia. Next, the
substrate 11 (1 mmol) dissolved in dry DMSO was added
to the solution and them the reaction mixture was
irradiated.
15
26
17
3
2
3
þ
(M —CH ) 478.9695.
3
2
N -ethyl-N -isopropyl-6-trimethylstannanyl-1,3,5-tria-
4
zin-2,4-diamine (13): White solid that decomposed in
1
column chromatography on silica gel. H-NMR (CDCl )
3
S
Reactions of 1, 7, and 11 with SnMe ions in
liquid ammonia in the dark
d: 0.27 (9H, s, JH–Sn ¼ 27.6 Hz); 1.13–1.21 (9H, m); 3.37–
3
13
3.39 (2H, m); 4.08–4.16 (1H, m). C-NMR (CDCl ) d:
3
ꢀ
9.53; ꢀ2.47; 14.82; 22.71; 35.25; 42.02; 162.41;
The procedure was similar to that for the previous
reaction, except that the reaction flask was wrapped with
aluminum foil.
162.98; 165.28. EM (EIþ) m/z (%): 334(6), 330(37),
328(27), 298(1), 260(3), 237(19), 233 (18); 219 (15), 203
(3), 180 (100), 163 (7). HRMS (EI) exact mass calcd for
þ
C H N Sn 345.0975, found (MH ) 346.1062.
1 23
1
5
2
2
4
N -Ethyl-N -isopropyl-1,3,5-triazin-2,4-diamine (12):
S
Inhibited reactions with SnMe ions in liquid
Isolated as a white solid after column chromatography on
silica gel, eluted with pentane/ethyl ether (80:20). Mp:
3
ammonia
1
1
81–182 8C. H-NMR (CDCl ) d: 1.17–1.22 (9H, m);
3
1
3.37–3.44 (2H, m); 4.13–4.16 (1H, m); 7.99 (1H, s). C-
3
The procedure was similar to that for the previous
reaction, except that 20 mol% of p-DNB or di-ter-butyl
nitroxide was added to the solution of nucleophile prior to
substrate addition.
NMR (CDCl ) d: 13.77; 22.72; 35.44; 42.28; 165.16;
3
172.26. EM (EIþ) m/z (%): 181(86), 166(94), 153(4),
138(34), 136(3), 124(18), 122 (29); 111 (25), 98(17), 96
(17), 83 (19), 71(67), 58(100), 55(21). HRMS (EI) exact
mass calcd for C H N 181.1327, found 181.1324.
8
15 5
Isolation and identification of products
ꢂ
Methyl 2,5- Bis-trimethylstannanylbenzoate (2): Isolated
as a white solid after column chromatography on silica
gel, eluted with pentane. Mp: 113–113.7 8C. H-NMR
REFERENCES
1
1
. For reviews, see: (a) Rossi RA, Pierini AB, Pe n˜ e´ n˜ ory AB. In
Recent Advances in the SRN1 Reaction of Organic Halides. The
Chemistry of Functional Groups, Patai S, Rappoport Z (eds).
Wiley: Chichester, 1995; Suppl. D2, Chapt. 24, 1395–1485; (b)
Rossi RA, Pierini AB, Santiago AN. In Organic Reactions,
Paquette LA, Bittman R (eds), Wiley & Sons: 1999, vol. 54,
pp. 1–271; (c) Rossi RA, Pierini AB, Pe n˜ e´ n˜ ory AB. Chem. Rev.
2003; 103: 71–167; (d) Rossi RA. In Synthetic Organic Photo-
chemistry, Griesberck AG, Mattay J (eds). Marcel Dekker: New
York, 2005; vol. 12, Chapter 15, pp. 495–527.
. Yammal CC, Podest a´ JC, Rossi RA. J. Org. Chem. 1992; 57: 5720–
5725.
. Lockhart MT, Chopa AB, Rossi RA. J. Organomet. Chem. 1999;
582: 229–234.
. C o´ rsico EF, Rossi RA. Synlett 2000; 227–229.
(
CDCl ) d: 0.25 (9H, s, J
¼ 27 Hz); 3.92 (3H, s); 7,64 (2H, s); 8,23 (1H, s).
¼ 27 Hz); 0,31 (9H, s,
3
H–Sn
J
H–Sn
1
3
C-NMR (CDCl ) d: ꢀ9.57; ꢀ7.51; 52.23; 134.54;
3
1
36.00; 136.97; 139.31; 142.55; 146.68; 169.21. EM
(
EIþ) m/z (%): 449 (80), 447 (100), 417 (22), 400 (6), 284
(5), 216 (35), 201 (23), 135 (9), 133 (6). HRMS (CI) exact
mass calcd for C H O Sn 463.9820 found 463.9811.
16
14
24
2
2
Methyl 2-chloro-5-trimethylstannanylbenzoate and
methyl 5-chloro-2-trimethylstannanyl benzoate (3): Iso-
2
3
4
lated as yellow oil after K u¨ gelrohr distillation (50 8C/
1
mm Hg). H-NMR (CDCl3) d: 0.27 (9H, s,
1
JH–Sn ¼ 27 Hz); 3.92 (3H, s); 7.49–7.61 (2H, m); 8.08–
5. Chopa AB, Lockhart MT, Silbestri G. Organometallics 2000; 19:
249–2250.
. Chopa AB, Silbestri G, Lockhart MT. J. Organomet. Chem. 2005;
90: 3865–3877.
7. Chopa AB, Lockhart MT, Silbestri G. Organometallics 2001; 20:
358–3360.
1
3
2
8
.09 (1H, d). C-NMR (CDCl ) d: ꢀ9.57; ꢀ7.38; 52.57;
3
6
1
29.81; 131.79; 137.68; 167.82. EM (EIþ) m/z (%): 319
6
(
100), 317 (73), 302 (4), 289 (50), 287 (36), 272 (3),
3
2
61(6), 259 (14), 231 (5), 165 (2), 151 (24), 133 (7), 118
5), 89 (5), 75 (7), 63 (4). HRMS (CI) exact mass calcd for
8
9
. C o´ rsico EF, Rossi RA. J. Org. Chem. 2002; 67: 3311–3316.
. Dol GC, Kamer PCJ, van Leeuwen PWNM. Eur. J. Org. Chem.
1998; 359–364.
(
C H ClO Sn (—CH ) 318.9548, found (M — CH )
þ
11
15
2
7
3
3
1
1
0. C o´ rsico EF, Rossi RA. Synlett 2000; 230–232.
3
18.9553.
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835

TRIMETHYLSTANNYLATION
835
1
1
1
1. Lippa KA, Roberts AL. Environ. Sci. Technol. 2002; 36: 2008–
018.
2. Yang W, Gan JJ, Bondarenko S, Liu W. J. Agric. Food Chem. 2004;
2: 7051–7055.
3. It has been demonstrated before that when the HME is faster than
the SRN1 mechanism the anion formed is protonated very fast by
liquid ammonia, see Ref. 2.
15. NIST Mass Spec Data Center, Stein SE, director, ‘‘Mass Spectra’’.
In NIST Chemistry WebBook, NIST Standard Reference Database
Number 69 Linstrom PJ, Mallard WG (eds). March 2003, National
Institute of Standards and Technology, Gaithersburg MD, 20899
(http://webbook.nist.gov).
16. All new compounds were purified by column chromatography and
were determined to be >95% pure by GLC and NMR.
17. We have tried DEI, CI, FAB, and even laser desorption and we
always see the loss of a methyl group.
2
5
1
4. Amatore C, Oturan MA, Pinson J, Sav e´ ant JM, Thi e´ bault A. J. Am.
Chem. Soc. 1985; 107: 3451–3459.
Copyright # 2006 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2006; 19: 829–835