The effect of CO on the reaction of (tributyltin)lithium with alkyl and aryl bromides

Article abstract of DOI:10.1016/s0022-328x(98)00486-0

The reaction of (tributyltin)lithium with alkyl and aryl bromides in THF was studied in the presence of CO and of p-dinitrobenzene under several reaction conditions. The observed results indicate that electron transfer is involved in the substitution reac

Full text of DOI:10.1016/s0022-328x(98)00486-0

Journal of Organometallic Chemistry 563 (1998) 31–36
The effect of CO on the reaction of (tributyltin)lithium with alkyl and
aryl bromides
N. Sbarbati Nudelman *, Cecilia Carro
Departamento de Qu´ımica Orga´nica, Facultad de Ciencias Exactas y Naturales, Uni6ersidad de Buenos Aires, Pab II, P.3, C. Uni6ersitaria,
1428 Buenos Aires, Argentina
Received 15 September 1997; received in revised form 16 January 1998
Abstract
The reaction of (tributyltin)lithium with alkyl and aryl bromides in THF was studied in the presence of CO and of
p-dinitrobenzene under several reaction conditions. The observed results indicate that electron transfer is involved in the
substitution reaction. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Tin; Lithium; Carbon monoxide; Electron transfer; Substitution
1. Introduction
reported for the case of Me3SnNa ([1]a), while in other
cases the authors seem to favor an almost exclusively
radical pathway [3]). Evidence has recently been pre-
sented that establishes that even the formation of car-
bene-derived products in the reaction of geminal
dihalides with trimethyltinsodium is in fact preceded by
a radical intermediate [3].
In the last few years, several mechanistic studies have
been reported on the trialkylstannylation of organic
halides [1–3]. The most recent studies, carried out using
bridged bicyclic halides [1,2] and cyclizable probes [3] as
a way of distinguishing between polar and radical
pathways, are controversial.
Three basic mechanistic pathways have been pro-
posed for the reaction of alkyl halides with trialkyltin
alkali–metal compounds: (a) a classic SN2 substitution
of the alkyl halide with a trialkyltin anion as the
nucleophile (mainly observed with primary halides)
[4,5], (b) substitution by an electron transfer (ET)-ini-
tiated SRN1 process [3,6] and (c) substitution by halo-
gen–metal exchange (HME; only established for
polyhalogenated compounds and for alkyl and aryl
iodides) ([1]b,[4]). In many cases, the observed distribu-
tion of products was interpreted as the result of differ-
ent apportionments between two or three pathways
[1,2,4] (albeit a mainly carbanionic mechanism was
Previous studies were based on the trapping of inter-
mediates with carbanion and/or radical traps [2], or
other ways of trapping the intermediates [7], the forma-
tion of rearranged products [3,6,8] and a variety of
stereochemical studies [9,10]. The present approach is
based on the use of carbon monoxide as a good one-
electron acceptor, as it has been described in previous
studies carried out with phenyllithium [11]. The reac-
tion of organotin compounds with carbon monoxide is
a well-known reaction that has been successfully used
for the synthesis of carbonyl-functionalized compounds
[12]. Taking into account the reagents and reaction
conditions, those reactions were usually written as clas-
sical polar reactions. However, recent research has been
reported describing the generation of radicals from
trialkyltin hydride and azo-bis-isobutyronitrile (AIBN)
[13,14] as an efficient method for the preparation of
acylstannyl compounds.
* Corresponding author. Fax: +54 1 7820529; e-mail: nudel-
man@quimor.qo.fcen.uba.ar
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00486-0

32
N. Sbarbati Nudelman, C. Carro / Journal of Organometallic Chemistry 563 (1998) 31–36
Table 1
Reaction between Bu3SnLi and organic bromides, RBr, in the presence of CO, in THF at 0°Ca
Entry
RBr
Reaction conditions
% Composition of the reaction mixture
% RBr conversion into Bu3SnR
RBrb
Bu4Snc
Bu3Snc
Bu6Sn2
1e
2f
c-C6H11Br
—
CO
—
31
45
30
50
30
43
14
17
35
20
51
31
26
36
9
43
24
68
35
3g
4h
C6H5Br
CO
33
a Initial [Bu3SnLi] 0.4–0.5 M; b % recovered; c % yields based on [Bu3SnLi]i; d % yield of Bu3SnR based on [RBr]i; e [Bu3SnLi]:[c-C6H11Br], 1:0.9;
f [Bu3SnLi]:[c-C6H11Br], 1:0.85; g [Bu3SnLi]:[C6H5Br], 1:0.81; h [Bu3SnLi]:[C6H5Br], 1:0.88.
Most of the synthetic and mechanistic studies on the
stannylation of organic halides were carried out using
triorganotinsodium ([1]a,[2–6,8–10]) and, only in a few
cases, comparison with triorganotinlithium was re-
ported ([1]b). We have recently reported the role of
aggregation effects in the reaction of organolithium
compounds with CO [15]: although the information on
the aggregation state of organostannyl alkali–metal
compounds is currently very scarce [16], the possibility
of aggregates should be borne in mind. In spite of the
fact that usually only the tin substitution products are
reported, it is likely that some information could be
also provided by a careful examination of most of the
tin products in the reaction mixture. Therefore, in the
present paper, as an additional mechanistic clue, the
yields of Bu3SnR and of other unsubstituted BunSnm
are given to account for the fate of the stannyl reagent.
preparation and quantitative analysis of the reagent are
given in Section 2.3. Since some small amounts of
Bu6Sn2 (and sometimes Bu4Sn) are almost unavoidable
in the preparation of Bu3SnLi, discussion of the yields
of these organotin compounds will be made on the
basis of relative differences; in all cases, a control
determination of the reaction in the absence of any
additive was carried out each time.
We have examined the reaction of Bu3SnLi with an
alkyl halide and an aromatic halide in the presence of
CO in THF at 0°C. The results are summarized in
Table 1. With cyclohexyl bromide, 1, the yield of
substitution product is decreased from 35% to 20%
(entries 1 and 2) in the presence of CO in the same time
period. Moreover, the amounts of by-products, Bu4Sn
and Bu6Sn2, have slightly increased and also the
amount of recovered cyclohexyl bromide. In the reac-
tion of Bu3SnLi with bromobenzene (entries 3 and 4) a
similar decrease in the yield of substitution product was
observed, while the yield of Bu6Sn2 significantly in-
creased (from 9% to 33%) as has the amount of unre-
acted bromobenzene. These results indicate that CO
interferes with the substitution reaction. CO is an inert
gas toward any polar reaction, while it was previously
reported that CO is an excellent one-electron acceptor
in the reactions of aryllithium compounds. In spite of
previous reports that radicals were not involved in the
reactions of primary halides with Bu3SnLi [21], Ashby
and coworkers [6] have provided evidence that the
reactions of primary alkyl bromides with Bu3SnNa
proceeds via an ET pathway to a significant extent. On
the other hand, in kinetic studies of the reactions of
trialkyltinlithiums with aliphatic chlorides in THF,
Kuivila reported that while the 1-butyl chloride reacted
by an SN2 pathway, geminal dichlorides such as CH2Cl2
and Me2CCl2 reacted by electron transfer processes [5].
The effect of CO observed in the present work is
interpreted as a competition in the first electron transfer
step (measured by k1), in which Bu3SnLi transfers one
electron to the organic bromide, giving a radical
cation–radical anion pair. CO would operate as a good
one-electron acceptor, competing with the organic
halide for the transferred electron (Eqs. (1) and (2)). It
2. Results and discussion
2.1. The nature of the reagent
Taking into account the fact that usually the reac-
tions of organotin compounds lead to complex reaction
mixtures [17], several methods of preparation described
in the literature were tried and in each case the presence
of by-products was carefully tested. Tributyltinlithium
can be prepared through the reaction in THF of:
hexabutylditin and metallic lithium [1]; tetrabutyltin
and lithium metal [18]; tributyltinchloride and lithium
metal [19]; or hexabutyltin and lithium dispersion at 0°
(as described for the preparation of Me3SnNa) [20]. The
best results (highest yield of reagent and smaller
amounts of by-products) were obtained from the reac-
tion of tributyltinchloride and lithium metal. Several
ratios of [Bu3SnCl]:[Li] were tested, 1:2,1:3, 1:5, 1:12
and 1:15. For ratios where the excess of [Li] was B1:5,
the yield of the reagent was low and a significant
amount of Bu6Sn2 was obtained. For [Li] excess \1:5,
the yield of the reagent was good, but a significant
amount of the disubstitution product (Bu2SnR2) was
observed in the reactions with RX. Details of the

N. Sbarbati Nudelman, C. Carro / Journal of Organometallic Chemistry 563 (1998) 31–36
33
Table 2
Reaction between Bu3SnLi and bromobenzene in the presence of CO and/or PDNB, in THF at 0°Ca
Entry
Reaction conditions
% Composition of thereaction mixture
% C6H5Br conversion into Bu3SnRd
C6H5Brb
Bu4Snc
Bu3SnRc
Bu6Snc2
1e
—
30
50
45
0
21
87
82
14
10
9
16
13
14
19
51
28
10
57
41
0
9
46
46
7
17
55
80
68
33
13
83
60
0
2f,g
3h,g
4i
PDNB
CO/PDNB
—
5i
CO
6i
PDNBk
CO/PDNBl
7j
0
0
a Initial [Bu3SnLi] 0.4–0.5 M; b % recovered; c % yields based on [Bu3SnLi]i; d % yield of Bu3SnR based on [C6H5Br]i; e [Bu3SnLi]:[C6H5Br], 1:0.81;
f [Bu3SnLi]:[C6H5Br], 1:1.02; g [Bu3SnLi]:[PDNB], 1:0.1; h [Bu3SnLi]:[C6H5Br], 1:0.88; i [Bu3SnLi]:[C6H5Br], 1:0.76 (quenching with Ac2O);
j [Bu3SnLi]:[C6H5Br], 1:0.81 and [Bu3SnLi]:[PDNB], 1:1; k 57% PDNB recovered; i 90% PDNB recovered.
mobenzene was observed in the absence of a radical
trap (entry 4), while 20% of bromobenzene was recov-
ered when CO was present (entry 5) and no substitution
product was detected in the presence of p-dinitroben-
zene (PDNB) (entry 6) or in the presence of both
CO/PDNB (entry 7).
can be observed that for PhBr, in which the radical
anion would be more stabilized, the yield of substitu-
tion product is higher than for cyclohexyl bromide. The
radical ions formed in the first step give the organic free
’
’
radicals, R and Bu3Sn by diffusion out of the solvent
’
cage. R reacts with fresh Bu3SnLi to start the SRN
1
The effects of temperature and of the reaction of
structurally different organic bromides with Bu3SnLi
was then examined. Table 3 summarizes the results of
the reactions with cyclohexyl, phenyl, allyl and benzyl
bromide with Bu3SnLi in THF at 50°C. By comparison
with the results in Table 1, it can be observed that, as
expected for an ET reaction, the temperature has no
effect on the yield of the substitution product (entries 1
and 2 of Tables 1 and 2). For the reaction of PhBr, a
slight decrease is observed, probably due to the smaller
[PhBr]. As was found at 0°C, the formation of the
substitution product is slowed down in the presence of
CO. However, a new feature appeared, namely the
significative increase in the amount of Bu4Sn (entries
1–4), which will be discussed below. Since its yield is
almost unaffected by the presence of CO or PDNB it
could suggest that the formation of Bu4Sn is not in-
volved in the reaction with RX.
radical chain.
k
1
“
“
Bu3SnLi+RBr“[(Bu3SnLi)+ , (RBr)−
]
(1)
(2)
ET
CO
k
“
“
Bu3SnLi+CO“[(Bu3SnLi)+ , (CO)−
]
ET
Although Eq. (1) is usually written as the anion
Bu3Sn− giving the free radicals Bu3Sn and R , it is
preferred to write it as a radical ion pair in view of the
differential effect observed for the counter-ion in the
few reactions where both, Na and Li organotin com-
pounds, were studied ([1]a,[2]). Solvent effects seem to
suggest that the lithium atom is in the co-ordination
sphere; thus, the addition of electron donors and of
18-crown-6 ether, has a significant effect on the reaction
of Me3SnLi with 2-bromooctane [22]. The effect of the
viscosity of the solvent has also been studied, and the
findings are consistent with the formation of a radical
anion–radical cation pair, and diffusion out of the
solvent cage increases as the viscosity of the solvent
decreases [6,10].
’
’
All the above results can be interpreted by the reac-
tion scheme shown (Scheme 1). The first slow step (k1)
would be the electron transfer from Bu3SnLi to the
organic halide to form a radical cation–radical anion
pair, I. Although a parallel SN2 reaction is not ex-
cluded, the evidence indicates that radicals are strongly
involved in the whole mechanisms. Reaction within the
cage (measured by k3) could produce the substitution
product but diffusion of the radicals out of the cage (k2)
is favoured in solvents of relatively low viscosity. The
If the above interpretation is correct, a known radical
anion scavenger such as p-dinitrobenzene (PDNB)
would trap the radical anion, and thus slow down the
substitution reaction. It can be observed from Table 2
(entry 2) that PDNB produces a significant decrease in
the yield of Bu3SnPh; 50% of bromobenzene is recov-
ered unreacted and, moreover, the yield of Bu6Sn2 has
increased from 9% to 46%. When the reaction was
carried out in the presence of both CO and PDNB
(entry 3), the yield of substitution product was only
10%, while formation of Bu6Sn2, a likely coupling
’
organic radical, R , could react with unreacted Bu3SnLi
’
(k4), giving the (Bu3SnR)− , which by further attack on
the organic halide would give the substitution products
’
’
product of Bu3Sn , was significant. When the reaction
and a fresh R . Further formation of Bu3SnR could
was carried out with the Bu3SnLi in a slight excess and
quenched with acetic anhydride, no unreacted bro-
occur by propagation of
mechanisms.
a radical chain SRN1

34
N. Sbarbati Nudelman, C. Carro / Journal of Organometallic Chemistry 563 (1998) 31–36
Table 3
Reaction between Bu3SnLi and organic bromides, RBr, in the presence of CO, in THF at 50°Ca
Entry
Halide
Reaction conditions
% Composition of the reaction mixture
% RBr conversion into Bu3SnRd
RBrb
Bu4Snc
Bu3SnRc
Bu6Snc2
1e
2
c-C6H11Br
C6H5Br
—
CO
—
CO
—
CO
—
30
33
23
42
58
50
55
43
41
44
18
21
35
5
10
8
32
31
31
17
22
53
32
76
57
22f
30h
22i
41
3g
4
5j
6
C3H5Br
32
7k
8
C6H5CH2Br
3
10
60l
44m
63
46
CO
a Initial [Bu3SnLi] 0.4–0.5 M; b % recovered; c % yields based on [Bu3SnLi]; d % yield of Bu3SnR based on [RBr]i; e [Bu3SnLi]:C6H11Br], 1:0.87;
f Bu2Sn(c-C6H11 2 9%; g [Bu3SnLi]:[C6H5Br], 1:0.60; h Bu2SnPh2 3%; i Bu2SnPh2 6%; j [Bu3SnLi]:[C3H5Br], 1:0.9, the % unreacted C3H5Br could
not be determined by GC under the present conditions; k [Bu3SnLi]:[C6H5CH2Br], 1:1; l toluene 11%; m toluene 9%.
)
In the presence of CO, ET to this good one-electron
3). In the presence of CO, the yield of toluene is slightly
acceptor (measured by k6) would compete with k1,
resulting in a lower production of R and a consequent
lower than that in the absence of CO, which is consis-
tent with the above proposed reaction (Scheme 1). The
effect of [PDNB] is also suggestive. It can be observed
from Table 2 that a significant decrease in the conver-
sion of C6H5Br is observed in the presence of PDNB
(entries 1–3). However, the production of Bu3SnPh is
only completely inhibited when a 1:1 reagent:scavenger
ratio is used (entries 6 and 7). This shows that if the
SRN1 chain exists, it is not very long.
Variable amounts of Bu4Sn are observed as an addi-
tional by-product in all cases, but it is especially high in
the reactions carried out at 50°C (Table 3). Although,
in principle, it could be assumed to arise from a side
reaction when preparing the reagent, it is clear that its
proportion in the reaction mixture varies according to
the reaction conditions, and it is especially high in the
reactions carried out at 50°C. A possible explanation
for the formation of Bu4Sn could be the partial decom-
position of the substrate and further reactions as shown
by Eqs. (3) and (4).
’
decrease in the yield of the substitution product,
’
Bu3SnR. The relatively high [Bu3Sn ] compared with
’
[R ] leads the reaction toward the production of higher
yields of the coupling products, Bu6Sn2 (k6). Termina-
tion of the radical chain by proton abstraction by the
solvent is indicated by reaction k7. With most of the
organic halides studied, the hydrocarbon was not de-
tected by GC (probably owing to their volatility). How-
ever, in the case of benzyl bromide, toluene was
detected in significant amounts (entries 7 and 8 in Table
Bu3SnLi“Bu•+(Bu2SnLi)•
(3)
(4)
Bu3SnLi+Bu•+SH“Bu4Sn+Li+ +(SH)•
Although compounds with Bu entities B3 have been
detected only as traces in some reaction mixtures, it is
’
likely that species like (Bu2SnLi) could also react with
the solvent, giving volatile compounds as well as with
’
R (or RBr) giving disubstitution products (Eqs. (5) and
(6)). Partial decomposition of the products to
’
(Bu2SnR) could also occur (although only to a minor
extent), which by further reaction would give rise to the
disubstitution product Bu2SnR2, which was observed in
small amounts (9, 3 and 6%, for entries 2–4, respec-
tively) when the reaction was carried out at 50°C (Table
3).
Scheme 1. The reaction scheme of (tributyltin)lithium with alkyl and
aryl bromides.
(Bu2SnLi)•+R•“Bu2RSnLi
(5)

N. Sbarbati Nudelman, C. Carro / Journal of Organometallic Chemistry 563 (1998) 31–36
35
Bu2RSnLi+RBr“Bu2R2Sn+Li+ +Br−
(6)
The injection port was kept at 270°C, and the detector
at 300°C. All product yields were obtained by GC.
NMR spectra were recorded in CDCl3 solution with
tetramethylsilane as reference, using a Brucker 200
spectrometer. Mass spectra were recorded using a BG
Trio-2 mass spectrometer. The isolation of the com-
pounds was made by reverse-phase chromatography,
using CH2Cl2 and CH3CN as eluents.
Decomposition of Bu3SnLi has been observed on
standing and it is known that it increases with tempera-
ture. This explanation is consistent with the observation
that with a more reactive alkyl bromide such as
C6H5CH2Br (entries 7 and 8) less decomposition of the
substrate is observed.
For the reactions with 1-bromopropene, in which
stabilization of the radical anion is also possible, the
amount of substitution product is similar to PhBr. In
the case of benzyl bromide (entries 7 and 8), the
increased yield may be due to the slightly higher
[PhCH2Br]. It is worthwhile noting that in this case
toluene was also present in the reaction mixture in 11
and 9%, respectively (entries 7 and 8). This is a clear
2.3.3. Lithium Tributyltin
Bu3SnLi was synthesized by a modification of a
method described in Ref. ([18]b). Lithiumtributyltin
was prepared by cutting lithium wire (25 mmol) into
small pieces into a flask containing boiling THF (16
ml), the flask was capped with a nonair stopper and
kept at 0°C. Tributyltinchloride (2 ml, 5 mmol) was
syringed into the flask and kept for 4 h at 0°C. The
mixture was then kept at 4–6°C until used. The concen-
tration of the solution of Bu3SnLi was typically 0.35–
0.45 M. This determination was made by Gilman’s
double titration method. The total amount of tin
present was determined by quenching a 1-ml aliquot of
the solution of Bu3SnLi with excess n-butyl chloride at
0°C and CG analyses of the reaction mixture.
’
indication of the presence of the PhCH2 radical, that
abstracts a proton from the solvent giving the hydro-
carbon. Similar results were not observed in the previ-
ous reactions, probably due to the more volatile nature
of the corresponding hydrocarbon. In all cases, the
yield of substitution product decreased while formation
of the by-products has increased.
2.2. Conclusions
2.3.4. Reaction of halides with lithium tributyltin in the
presence of CO
The observed inhibition in the production of the
substitution product in the reaction of tributyltin-
lithium with organic bromides, when CO is present,
indicates that electron transfer is involved in the substi-
tution mechanism and that CO is a good one-electron
acceptor competitor in that reaction. This conclusion is
confirmed by the effect of radical scavengers and the
yields of by-products arising from radical couplings and
hydrogen abstraction from the solvent.
A vial containing a Teflon-coated stirring bar was
capped with a nonair stopper, it was evacuated and
filled with dry nitrogen alternatively several times, and
then put into a bath at the appropriate temperature,
with vigorous magnetic stirring. A solution of Bu3SnLi
in THF was added by a syringe, the solution was
exposed to CO at ca. 1013 mbar for 30 min. Then
aliquots of the halide in THF solution was added by a
syringe during 90 min, under a CO atmosphere. The
reaction was quenched by treating the reaction mixture
with NH4Cl (10%). When the radical trap PDNB was
used (typically 10 mol%) it was added to the vial prior
to the addition of Bu3SnLi.
2.3. Experimental
2.3.1. Materials
Tetrahydrofuran and hexane were purified as previ-
ously described [23] and distilled from sodium ben-
zophenone ketyl immediately prior to use.
Tributyltinchloride (Merck) was used as-received. All
halides were distilled prior to use.
2.3.5. Bu4Sn
EM; m/z (relative intensity): 291 (M+-57) (46), 289
(34), 235 (72), 233 (55), 177 (93), 179 (100), 119 (36),
121 (45). 1H-NMR (CDCl3, l ppm): 1.60–1.40 (m, 6H),
1.30–1.15 (m, 12H), 1.00–0.75 (m, 9H). 13C-NMR
(CDCl3, l ppm): 29.8, 27.4, 13.7, 8.8.
2.3.2. General procedures
All reactions were carried out in a nitrogen-inert
atmosphere. Solutions and solvents were transferred by
syringes, under a stream of inert gas. Quantitative GC
analyses were performed using a Hewlett Packard HP
5890 series II plus gas chromatograph equipped with a
flame ionization detector and a HP-5 column; n-decane
was used as an internal reference in all cases. A typical
procedure employed a N2 flow rate of 1.5 ml min−1
and a temperature programing from 70°C (held for 5
2.3.6. Bu6Sn2
EM; m/z (relative intensity): 525 (M+-57) (16), 523
(14), 467 (16), 465 (14), 355 (46), 353 (43), 295 (21), 293
(20), 291(20), 239 (28), 235 (39), 179 (89), 177 (100), 121
(49), 119 (52). 1H-NMR (CDCl3, l ppm): 1.55–1.51 (m,
12H), 1.50–1.35 (m, 12H), 1.30–1.15 (m, 12H), 1.00–
0.75 (m, 19H). 13C-NMR (CDCl3, l ppm): 28.8, 27.4,
13.7, 8.5.
min) to 250 or 270°C (held for 10 min) at 10°C min−1
.

36
N. Sbarbati Nudelman, C. Carro / Journal of Organometallic Chemistry 563 (1998) 31–36
Acknowledgements
2.3.7. Bu3SnC6H5
EM; m/z (relative intensity): 311 (M+-57) (64), 309
(49), 255 (80), 253 (61), 197 (100), 195 (89), 120 (30).
1H-NMR (CDCl3, d ppm): 7.50–7.49 (m, 2H), 7.35–
7.33 (m, 3H), 1.62–1.60 (m, 6H), 1.41–1.38 (m, 6H),
1.15–1.12 (m, 6H), 0.98–0.80 (m, 9H). 13C-NMR
(CDCl3, l ppm): 142.0, 136.0, 127.0, 29.1, 27.4, 13.7,
9.6.
C. Carro is a grateful recipient of a fellowship from
the National Research Council (CONICET) from Ar-
gentina. Financial support from the CONICET and the
University of Buenos Aires is gratefully acknowledged.
References
2.3.8. Bu3SnCH2C6H5
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[12] N.S. Nudelman, The carbonylation of main group organometallic
compounds, in: S. Patai (Ed.), The Chemistry of Double-Bonded
Functional Groups, Wiley, Chicester, 1989.
2.3.9. Bu3SnC6H11
EM; m/z (relative intensity): 317 (M+-57) (17), 315
(13), 291 (34), 289 (24), 261 (33), 259 (24), 235 (57), 233
1
(45), 179 (100), 177 (90), 121 (51), 119 (42). H-NMR
(CDCl3, l ppm): 1.40–1.20 (m, 23H), 1.05–0.70 (m,
15H). 13C-NMR (CDCl3, l ppm): 30.6, 29.3, 29.08,
27.6, 25.6, 13.6, 10.0, 7.8.
[13] I. Ryu, K. Kusano, H. Yamazaki, N. Sonoda, J. Org. Chem. 56
(1991) 5003.
[14] I. Ryu, K. Kusano, A. Ogawa, N. Kambe, N. Sonoda, J. Am.
Chem. Soc. 112 (1990) 1295.
2.3.10. Bu3SnC3H5
[15] (a) N.S. Nudelman, E.S. Lewkowicz, J.J.P. Furlong, J. Org. Chem.
58 (1993) 1847. (b) G. Boche, I. Langlotz, M. Marsch, K. Harms,
N.S. Nudelman, Angew Chem. Int. Ed. Engl. 31 (1992) 1205.
EM; m/z (relative intensity): 275 (M+-57) (10), 235
(57), 233 (40), 179 (100), 177 (90), 121 (50), 119 (47).
1H-NMR (CDCl3, l ppm): 6.02–5.88 (m, 1H), 4.84–
4.63 (m, 2H), 1.81–1.77 (m, 1H), 1.60–1.40 (m, 6H),
1.35–1.10 (m, 12H), 1.10–0.60 (m, 10H). 13C-NMR
(CDCl3, l ppm): 138.1, 109.1, 30.6, 29.1, 27.3, 13.6,
9.13.
7
[16] H. Reich, J. Borst, R. Dykstra, Recent Li-NMR determinations
favor a monomeric structure for Bu3SnLi in THF, Organometal-
lics 1 (13) (1994) 1.
[17] D. Curran, S. Hadida, J. Am. Chem. Soc. 118 (1996) 2531.
[18] (a) Y. Horikawa and T. Takeda, J. Organomet. Chem. 523 (1996)
99. (b) C. Tamborski, F.E. Ford, E. Soloski, J. Org. Chem. 28
(1963) 181.
[19] C. Yammal, J. Podesta´, R. Rossi, J. Org. Chem. 57 (1992) 5720.
[20] E.C. Ashby, X. Sun, J.L. Duff, J. Org. Chem. 59 (1994) 1270.
[21] M. Newcomb, A.R. Courtney, J. Org. Chem. 45 (1980) 1707.
[22] M. Alnajjar, H. Kuivila, J. Am. Chem. Soc. 107 (1985) 415.
[23] (a) N.S. Nudelman, D. Perez, J. Org. Chem. 53 (1988) 4088. (b)
A.A. Vitale, F. Doctorovich, N.S. Nudelman, J. Organomet.
Chem. 393 (1987) 91.
2.3.11. C6H5CH2CH2C6H5
EM; m/z (relative intensity): 182 (M+) (17), 91 (100),
1
77 (4). H-NMR (CDCl3, l ppm): 7.18–7.16 (m, 8H),
7.12–7.09 (m, 12H), 2.57–2.60 (m, 4H). 13C-NMR
(CDCl3, l ppm): 144.2, 128.5, 127.9, 125.7, 28.9.
.