Insights into the reaction behaviour of stannylated allylic substrates

Article abstract of DOI:10.1002/ejoc.201001400

Stannylated allylic substrates are versatile building blocks for organic synthesis. Pd⁰-catalysed coupling reactions of 2-stannylated allylic carbonates, acetates and phenoxides with amines, malonates, phenoxides, imides and distannanes provide

Full text of DOI:10.1002/ejoc.201001400

FULL PAPER
DOI: 10.1002/ejoc.201001400
Insights into the Reaction Behaviour of Stannylated Allylic Substrates
Christian Bukovec,[a] Alexander O. Wesquet,[a] and Uli Kazmaier*[a]
Keywords: Allenes / Allylic alkylation / Bismetallation / Hydrostannation / Molybdenum / Palladium
Stannylated allylic substrates are versatile building blocks
for organic synthesis. Pd0-catalysed coupling reactions of 2-
stannylated allylic carbonates, acetates and phenoxides with
amines, malonates, phenoxides, imides and distannanes pro-
vide the corresponding substituted allylic compounds, which
are suitable for subsequent modifications including Stille
coupling reactions. The reaction mechanisms are dependent
on the temperature and the nucleophiles used. Tsuji–Trost
allylic substitution takes place with organic nucleophiles at
low temperature. When distannane is employed at higher
temperature, on the other hand, Pd0-catalysed bismetallation
of allenes formed in situ by elimination of tributyltin meth-
oxide predominates.
Introduction
In chemical biology and pharmaceutical chemistry, di-
verse libraries of small molecules are often investigated in
order to identify lead structures for new drug candidates.[1]
A key point for the success of such an approach is the
choice of a suitable building block allowing a wide range
of modifications and different reaction modes, generating
scaffold diversity. Good candidates for this purpose are
stannylated allyl carbonates such as 1a (Scheme 1), which
combine the structural features of two important cross-cou-
pling reactions: the Stille coupling[2] and allylic alkylation.[3]
Both reactions have been investigated intensively and are
often used in natural product syntheses and combinatorial
chemistry.
Stannylated compounds of type 1 can be obtained by
hydrostannation of the corresponding propargyl alcohol de-
rivatives either under radical or under transition-metal-cat-
alysed conditions. Whereas the radical version in general
gives mixtures of regio- (α,β) and stereoisomers (E/Z), the
catalytic approach proceeds stereoselectively in a syn man-
ner,[4] although the control of the regioselectivity is not a
trivial issue.[5] In addition, the commonly used Pd catalysts
are unsuitable for the hydrostannation of propargylic esters
and carbonates, providing only decomposition products un-
der the typical reaction conditions. This forced our group
to develop new hydrostannation catalysts, based on molyb-
denum[6] and tungsten[7] complexes. Our favourite catalyst –
Mo(CNtBu)3(CO)3 (MoBl3) – allows the hydrostannation
of a wide range of electron-poor alkynes with high yields
and good regioselectivities.[8] Propargylic ethers and esters
are also good substrates, giving rise to the required α-stann-
Scheme 1. Synthesis and conversion of stannylated allylic carbon-
ates.
ylated products of type 1 in only one step. Best results are
obtained under CO, under which the formation of side
products can be suppressed almost completely.[9]
With these building blocks to hand, we have been able
to show that the proposed allylic alkylation/Stille approach
can be applied successfully in amino acid and peptide chem-
istry. With chelated glycine enolates the corresponding stan-
nylated allyl glycines are formed.[10] Even peptides can be
allylated successfully, allowing highly stereoselective peptide
backbone modifications.[11] In such cases, the formation of
the new stereogenic centre can be controlled through the
adjacent stereocentres in the peptide chain.[12] The stann-
ylated amino acids can be further modified by subsequent
Stille couplings, allowing the generation of amino acid and
peptide libraries.[13]
[a] Institute of Organic Chemistry, Saarland University,
P. O. Box 151150, 66041 Saarbrücken, Germany
Fax: +49-681-302-2409
E-mail: u.kazmaier@mx.uni-saarland.de
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C. Bukovec, A. O. Wesquet, U. Kazmaier
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These examples clearly show that with reactive nucleo- normally observed, or b) the methoxide could attack the tin
philes the allylic alkylation can proceed selectively without fragment to liberate the allene 3 and the tin methoxide 4
affecting the vinylstannane subunit, which can be coupled (Scheme 2). All of these compounds should provide unmis-
separately afterwards.
takable signals in their 1H NMR spectra, so we carried out
the “reaction without the nucleophile” in a NMR tube to
follow the kinetics of the decomposition and to analyse the
intermediates and products.
Results and Discussion
In this experiment the generally used CDCl3 was re-
placed by [D8]toluene to avoid possible side reactions be-
tween the solvent and the vinylstannane. All ingredients
were mixed together at 0 °C and the measurements were
started immediately after the sample had been placed in the
To increase the synthetic potential of these stannylated
compounds, we were interested in finding other nucleo-
philes suitable for allylic alkylation and in developing com-
pletely new reactions of these substrates. This is not a trivial
issue, because β-metallated alcohol derivatives can easily
undergo elimination,[14] which should result here in the for-
mation of allenes.[15] In addition, vinylstannanes can also
be used as nucleophiles in allylic alkylations,[16] which might
result in oligo- or polymerization of the allylic substrate.
Because of our good results obtained with the chelated
enolates we used malonate in our initial experiments
(Scheme 2). To keep the reaction conditions as mild as pos-
sible we worked under neutral conditions with the stann-
ylated allyl carbonate 1b. In general, the methoxide liber-
ated during π-allyl complex formation deprotonates the ma-
lonate, generating the reactive nucleophile.[17] Surprisingly,
the expected substitution product was obtained only in
traces, although the allylic substrate 1b was consumed com-
pletely. Whereas no reaction was observed at low tempera-
tures (–20 to 0 °C), decomposition of the substrate obvi-
ously occurs at or above room temperature. Because 1b is
obtained by hydrostannation of the corresponding alkyne
at 50 °C in THF, the allylic substrate per se should be (ther-
mally) stable under the reaction conditions. Obviously the
Pd catalyst is responsible for the undesired decomposition.
1
NMR machine. H NMR spectra were taken every minute
at room temp. and Figure 1 shows the composition of the
NMR sample as a function of time. The formation of the
allene 3 as an elimination product could already be ob-
served after 1 min. Obviously, this decomposition starts im-
mediately after the addition of the catalyst. The amount of
allene 3 grows continuously as the amount of 1b is reduced.
After 25 min, the starting material had been completely
consumed.
Figure 1. Pd-catalysed decomposition of stannylated allyl carbon-
ates.
Decomposition to the allene 3 is definitely the major
pathway (attack b, ca. 90%), but nucleophilic attack of the
methoxide on the π-allyl complex (attack a), resulting in the
formation of the allyl ether 2 (ca. 10%), obviously also
plays a role.
Scheme 2. Pd-catalysed decomposition of stannylated allyl carbon-
ates.
Although the decomposition limits the scope of nucleo-
From our previous experiments with chelated enolates[8] philes that can be used for the allylic alkylations, it might
we knew that the allyl carbonate 1b forms the π-allyl com- also provide an easy and mild process for the generation of
plex A at very low temperatures, even at –70 °C. We can allenes, probably coordinated with the Pd in the initial
therefore be sure that the allyl complex A is formed, but phase of their formation. If one were able to trap these al-
obviously at higher temperature it undergoes side reactions/ lene-Pd complexes this would open up new synthetic per-
decomposition, which is not a problem with highly reactive spectives.
nucleophiles that react already at low temperature. One can
To find nucleophiles that would react by allylic alkylation
think of two possibilities: a) a direct nucleophilic attack of at 0 °C, and would hence be suitable for the reaction with
the liberated methoxide could occur on the π-allyl complex 1, and also to minimize the side reactions, we undertook a
to provide the decarboxylated product 2, a reaction not screening of several types of nucleophiles commonly used
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Reaction Behaviour of Stannylated Allylic Substrates
in these allylations. To obtain the required information as
On the basis of these results we set up another set of
quickly as possible we decided to use a competitive ap- nucleophiles, containing less reactive representatives such as
proach. Amines, especially secondary ones, are known to methyl malonate, succinimide, N-hydroxysuccinimide, phe-
be good nucleophiles in allylic alkylations, being applied in, nol and trifluoroacetamide. In principle, all these nucleo-
for example, the cleavage of allyl protecting groups.[18] We philes contain acidic hydrogens that should be removed by
therefore subjected a stoichiometric mixture of three dif- the liberated alkoxide. Unfortunately, though, no reaction
ferent amines to our standard reaction conditions (Table 1, was observed with any of them under these “neutral” reac-
Entries 1–3). For these model studies cinnamyl carbonate tion conditions. Addition of an excess of NaOMe changed
was used as substrate (instead of 1) to allow easy monitor- the situation dramatically. All nucleophiles showed good
ing of the reaction by GC–MS. Naphthalene was used as levels of conversion. Whereas the malonate (Entry 4) was
internal standard. The reaction was started at –78 °C and the most reactive of these substrates, showing a significant
the reaction mixture was warmed stepwise to room tem- degree of conversion at –20 °C,[20] succinimide[21] (Entry 5)
perature. After 18 h at room temperature the mixture was and phenol[22] (Entry 6) started slowly at this temperature.
heated at reflux for an additional three hours.
With N-hydroxysuccinimide[23] (Entry 7) the reaction set in
at 0 °C, and the trifluoroacetamide (Entry 8) required room
temperature to show significant reactivity. With all sub-
strates more than 60% conversion was observed after 18 h,
but this is probably too long for the sensitive stannylated
substrates. Piperidine was definitely the nucleophile of
choice, but 1-phenylethylamine, malonate, succinimide and
phenol also seemed worth investigation.
Table 1. Reactivities of several nucleophiles.
On the basis of the good results obtained with the sec-
ondary cyclic amine, piperidine was used to optimize the
reaction conditions for the conversion of the stannylated
allylic substrate (Table 2).[24] No allylation product was ob-
tained if the reaction was run in THF at room temperature
(Entry 1), although 1a was completely consumed. These re-
sults are comparable to those obtained earlier with malon-
ate. On reduction of the reaction temperature to 0 °C, the
decomposition reactions were diminished and the stan-
nylated allylamine 5 was obtained in good yield (Entry 2).
Interestingly, the decomposition seems to be highly depend-
ent on the solvent used. In other solvents such as CH2Cl2
or DMF the side reactions were less significant and 5 was
obtained at room temperature in acceptable to good yields
(Entries 3 and 4). The highly polar solvent DMF seems to
be the solvent of choice, showing the fastest conversion and
the best yield. Even at 0 °C the reaction was finished after
2 h (Entry 5). Further reduction of the reaction temperature
does not improve the yield considerably (Entry 6). There-
fore, for further optimization the reactions were carried out
at 0 °C.
We next investigated the influence of the leaving group
on the outcome of the reaction. Whereas the corresponding
methyl carbonate 1b gave comparable results (Entry 7), the
sterically more demanding tert-butyl carbonate 1c was sig-
nificantly less suitable (Entry 8). The best yield was ob-
With piperidine the reaction started slowly at –20 °C, tained with the corresponding acetate 1d (Entry 9), but in
and after 1 h around 10% of the allylation product could this case some impurities that could not be removed com-
be determined.[19] After 1 h at 0 °C the level of conversion pletely from the product were formed. To our great surprise,
was ca. 45% and after a further 1 h at room temperature it even the THP ether 1e (Entry 10) gave the coupling product
was complete (Entry 1). 1-Phenylethylamine (Entry 2) and in good yield, although this is normally a protecting and
anisidine (Entry 3) were significantly less reactive. Phenyl- not a leaving group. Interestingly, when phenoxides were
ethylamine reacted very slowly at room temperature (80% employed different reaction temperatures had to be chosen,
conversion after 18 h) and anisidine required subsequent depending on their substituents. The electron poor p-NO2-
heating. Interestingly, with these two primary amines only phenoxide 1f (Entry 11) reacted similarly to the carbonate
the formation of the diallylated product B was observed. 1a at 0 °C, whereas the unsubstituted phenoxide 1g (En-
No monoallylated product A could be determined.
try 12) had to be warmed to 65 °C for 2 h or to 45 °C over-
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C. Bukovec, A. O. Wesquet, U. Kazmaier
Table 3. Allylic substitution of various nucleophiles.
FULL PAPER
Table 2. Optimization of the reaction conditions.
Entry
1
X
React. cond.
Cat.[a] Yield [%]
1
2
3
4
5
6
7
8
1a
1a
1a
1a
1a
1a
1b
1c
1d
1e
1f
OCOOEt
OCOOEt
OCOOEt
OCOOEt
OCOOEt
OCOOEt
OCOOMe
OCOOtBu
OAc
THF, 20 °C, 1 h
THF, 0 °C, 5 h
CH2Cl2, 20 °C, 5 h
DMF, 20 °C, 1 h
DMF, 0 °C, 2 h
DMF, –20 °C, 2 h
DMF, 0 °C, 2 h
DMF, 0 °C, 2 h
DMF, 0 °C, 2 h
DMF, 0 °C, 2 h
A
A
A
A
A
A
A
A
A
A
A
A
A
B
C
0
74
49
70
79
80
79
56
88
71
88
62
76
79
94
9
10
11
12
13
14
15
OTHP
O-p-NO2-Ph DMF, 0 °C, 2 h
OPh
OPh
OCOOEt
OCOOEt
1g
1g
1a
1a
DMF, 65 °C, 2 h
DMF, 45 °C, 16 h
DMF, 0 °C, 2 h
DMF, 0 °C, 2 h
[a] Catalysts: A) [Pd(allyl)Cl]2 (1 mol-%), PPh3 (4.5 mol-%),
B) [Pd(allyl)Cl]2 (1 mol-%), dppf (4.5 mol-%), C) Pd(PPh3)4 (2 mol-
%).
night (Entry 13) in order to afford the desired product. we used NaH for deprotonation. Interestingly, in the reac-
With this less reactive leaving group the substrate was ob- tion with phthalimide the mixture had to be warmed to
served to be more stable to higher temperatures in the pres- 40 °C for 2 d to afford acceptable conversion of this rather
ence of Pd0, with no decomposition being observed in unreactive nucleophile. This example clearly shows that in
DMF even at 65 °C.
DMF the decomposition of the π-allyl complex A
To confirm the influence of the catalyst system, we also (Scheme 1) to the allene is rather slow. In contrast, in THF
varied the phosphane ligands used. Whereas slow and in- this side reaction seems to be favoured.
complete conversion was observed in the presence of elec-
According to the proposed mechanism discussed in
tron-donating PBu3, the ferrocenyl ligand dppf gave results Scheme 2, one might expect that the decomposition path-
comparable to those seen with PPh3 (Entry 14). The best way b should provides an allene still coordinated to the Pd
yield was obtained with Pd(PPh3)4, which provided 5 in a in the initial phase of the “decomposition”. To establish
very clean reaction (Entry 15).
whether or not this was true we tried to trap this “acti-
These optimized conditions were used to investigate the vated” allene directly by a Pd-catalysed addition reac-
allylation of various types of nucleophiles (Table 3). Other tion.[25] Our hope was to control the regioselectivity in the
nucleophilic secondary amines such as morpholine (En- addition step through selective addition to the activated
try 1), pyrrolidine (Entry 2) and diethylamine (Entry 3) gave double bond formed in the elimination step. Of course, such
results comparable to those obtained with piperidine, with an approach would only be successful if the addition were
yields between 86 and 90%. Although most primary amines faster than the dissociation of the Pd. A further require-
exclusively reacted twice, not forming monoallylation prod- ment is that the transition metal not undergo migration be-
ucts, in our test reactions with cinnamyl carbonate, we also tween the cumulated double bonds.
checked phenethylamine as nucleophile. With our sterically
more demanding allylic substrate 1b only the monoallyl- we became familiar with some interesting work by Mitchell
amine 9 was formed, in good yield (Entry 4). et al. describing distannylations and silastannylations of all-
During our search for suitable reactions for this purpose
We next focused on other types of nucleophiles, espe- enes.[26] These reactions provide highly interesting building
cially those that gave the best results in our test reaction. In blocks each containing both a vinylic and an allylic carbon
the presence of additional base, malonate (Entry 5), phenol metal bond. These bifunctional organometallics can be cou-
(Entry 6) and phthalimide (Entry 7) gave the desired al- pled independently at one or the other position, which al-
lylation products, although in lower yields than the more lows the synthesis of a variety of highly functionalized mo-
nucleophilic amines. In the first experiments we used meth- lecules.[27] Meanwhile a range of other bismetallations such
oxide (the same as was liberated from the allylic substrate as diborylations,[28] germastannylations,[29] silaborations[30]
1b) as a base. Although malonate gave acceptable yields un- and disilylations[31] have been described. Recently Cheng
der these conditions, significant amounts of the stannylated et al. reported on Pd-catalysed three-component couplings
allyl ether 2 (Scheme 2) were formed in the reactions with proceeding through one-pot dimetallation/Stille cou-
phthalimide and phenol. Therefore, in these two examples plings.[32] With regard to our long-term interest in hydrome-
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Reaction Behaviour of Stannylated Allylic Substrates
tallations[6–10] and our previous work on transition-metal- to the Pd before the addition. Otherwise, the free allene
catalysed hydrostannation of allenes[33] and distannyl- would immediately evaporate under the reaction conditions
ations[7] the dimetallation of allenes formed in situ became used.
a highly interesting goal.[34] We therefore treated the stan-
With these results to hand, we also investigated some
nylated allyl acetate 1d with (Bu3Sn)2 in THF at 60 °C – other bismetallations. Whereas the silylated allylstannane
conditions we know to favour allene formation – and the 14 was formed in good yield with Bu3Sn–SiMe3, no reac-
distannane 12 was indeed obtained in acceptable yield tion was observed with (Me3Si)2. The result of the reaction
(Scheme 3). In a detailed investigation of the reaction we with disilane was not surprising: Watanabe et al. had pre-
observed that this dimetallation is also very sensitive viously reported that this reaction requires harsh condi-
towards impurities in the catalyst and the distannane, and tions.[31] Under such conditions decomplexation of the al-
to circumvent these problems we also investigated distann- lene is probably faster than the addition, which explains the
ylation with Bu3SnH. It is well known that Bu3SnH “de- complete consumption of 1g without product formation.
composes” in the presence of Pd0 to give distannane,[35] On the other hand, the outcome of the reaction with the
generally as an undesired side product. In our case, how- mixed silylstannane was highly interesting. With a substo-
ever, this reaction could be used to produce the required ichiometric amount, 14 was formed as the sole product with
distannane freshly in situ. Indeed, with Bu3SnH the same excellent regioselectivity, which is in full agreement with the
distannylated product 12 was formed, even in better yield.
observations made by Mitchell, Cheng et al.[32]
In contrast, if the silylstannane was used in large excess
(more than 2 equiv.) only the disilane 15[31] was obtained,
in high yield, so this protocol is an excellent alternative for
the critical disilylation. If less than 2 equiv. Bu3SnSiMe3 is
used, mixtures of 14 and 15 are obtained. NMR studies
indicate that 14 is formed first in both cases, and that in the
presence of additional silylstannane slow transmetallation
occurs.
To establish whether or not the coordination of the allene
to the Pd could also be used for regioselective bismetalla-
tions, we next investigated some substituted stannylated all-
yl acetates, such as 16 (Scheme 4). This substrate showed
reaction behaviour similar to that of 1g, but the substituted
allene intermediate generated additional selectivity issues
that had to be addressed. The reaction with (Bu3Sn)2, for
example, provided the distannane 17[38] with excellent re-
gioselectivity. The distannane addition occurred exclusively
at the double bond formed in the elimination step. Interest-
ingly, if the reaction time was prolonged, complete conver-
sion into the isomeric distannane 18 was observed. The
thermodynamically more stable E isomer was formed,
which is in good agreement with observations made pre-
viously by Mitchell et al.[26b] Therefore, both isomeric dis-
tannanes can be obtained selectively simply by changing the
reaction time.
Scheme 3. Bismetallation of allenes generated in situ. Reaction con-
ditions and reagents: Pd(PPh3)4 (2 mol-%), THF, 60 °C; a) (Bu3Sn)2
(1.05 equiv.), 2.5 h, b) Bu3SnH (3.15 equiv.), 2.5 h, c) (Bu3Sn)2
(1.05 equiv.), 6 h, d) (Me3Sn)2 (1.05 equiv.), 18 h, e) Me3SiSnBu3
(0.7 equiv.), 18 h, f) (Me3Si)2 (1.05 equiv.), 18 h, g) Me3SiSnBu3
(2.2 equiv.), 18 h.
During the optimization of the allylic amination we ob-
A similar observation was made on addition of Me3Si-
served that even stannylated allylic ethers are good sub- SnBu3. The reaction occurred regioselectively at the substi-
strates for this reaction. To establish whether or not this tuted double bond to provide 19 (Scheme 4) in high yield.
would also be true for the bismetallation, we subjected the Again, an isomerization was observed during the reaction
phenyl ether 1g to the same reaction conditions. Although time, although here the conversion was not complete, with
the reaction was slightly slower than that of the acetate, the a 2:1 mixture of 19 and the isomerized product 20 being
distannane 12[36] was obtained in excellent yield.
obtained.[39] It is worth mentioning that no transmetalla-
To verify the hypothesis that the reaction proceeds via tion to the disilylated product was observed with an excess
an allene-Pd complex and not via a π-allyl complex that of the silastannane.
is attacked by a tin nucleophile, we performed the cross-
This exchange probably does not occur for steric reasons,
experiment. The reaction with (Me3Sn)2 provided the stan- and the same 2:1 product mixture was obtained. As ex-
nane 13[37] exclusively, and the formation of Bu3SnOPh was pected, no reaction occurred either with (Me3Si)2, but in
observed by NMR spectroscopy. This clearly indicates that this case we were able to isolate the substituted allene 21,[40]
the distannanes are formed by an elimination/addition pro- clearly indicating that the decomplexation of the allene is
cess. The high yield of 12 obtained in the previous reaction much faster than the disilylation. In the absence of any bis-
is also very strong evidence that the allene stays coordinated metal species, the allene 21 was obtained in excellent yield.
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C. Bukovec, A. O. Wesquet, U. Kazmaier
FULL PAPER
silastannation proceeded with high yield and regioselectiv-
ity (23), the corresponding distannylation was a very slow
process. Even after 20 h less than a 20% yield of product
24 was obtained. Interestingly, even after such a long reac-
tion time, no isomerization was observed under the reaction
conditions, as determined by NMR spectroscopy. Surpris-
ingly, though, the isomerized product 25 was obtained after
flash chromatography. Obviously, the isomerization is cata-
lysed by the silica gel.
Conclusions
In conclusion, we have been able to show that stann-
ylated allylic substrates are excellent building blocks for
combinatorial chemistry. Depending on the reaction condi-
tions used, they can either be modified through allylic sub-
stitutions or they can be converted into Pd-activated allenes
that undergo regioselective additions. These additions occur
with high regioretention, and the substrate spectrum can be
broadened by taking advantage of isomerization processes.
The scope and limitations of these processes are being
evaluated in ongoing studies.
Experimental Section
General Remarks: All air- or moisture-sensitive reactions were car-
ried out in oven-dried glassware (70 °C). Dried solvents were dis-
tilled before use: THF was distilled from LiAlH4 and CH2Cl2 was
dried with CaH2 before distillation. Hexabutyldistannane was puri-
fied before use by flash chromatography (silica, hexanes). The prod-
ucts were purified by flash chromatography on silica gel columns
(Macherey–Nagel 60, 0.063–0.2 mm). Analytical TLC was per-
formed on pre-coated silica gel plates (Macherey–Nagel, Poly-
gram® SIL G/UV254). Visualization was accomplished with the aid
1
of UV light, KMnO4 solution or iodine. H, 13C and 119Sn NMR
spectra were recorded with Bruker AC 400 [400 MHz (1H),
100 MHz (13C) and 149 MHz
(
119Sn)] or Bruker DRX 500
[500 MHz (1H), 125 MHz (13C) and 186 MHz (119Sn)] spectrome-
ters in CDCl3. Chemical shifts are reported in ppm (δ) with respect
to TMS, and CHCl3 was used as the internal standard. Selected
signals for minor isomers are extracted from the spectra of the iso-
meric mixtures. Mass spectra were recorded with a Finnigan
MAT 95 spectrometer by the CI technique. Elemental analyses
were performed at the Saarland University.
Scheme 4. Regioselective bismetallation of substituted allenes gen-
erated in situ. Reaction conditions and reagents: Pd(PPh3)4 (2 mol-
%), THF, 60 °C; a) (Bu3Sn)2 (1.20 equiv.), 5 h, b) (Bu3Sn)2
(1.2 equiv.), 18 h, c) Me3SiSnBu3 (0.8 equiv.), 2 h, d) Me3SiSnBu3
(0.8 equiv.), 16 h, e) 2 h, f) Me3SiSnBu3 (0.95 equiv.), 11 h,
g) (Bu3Sn)2 (1.05 equiv.), 21 h, h) SiO2, flash chromatography.
General Procedure for the Allylic Aminations (GP1): Pd(PPh3)4
(6 mg, 5.0 μmol, 2 mol-%) was dissolved in dry DMF (2 mL) in
a Schlenk flask and the mixture was stirred for 15 min at room
temperature under nitrogen. After addition of the amine
(0.275 mmol, 1.1 equiv.), the solution was cooled to 0 °C and the 2-
(tributylstannyl)allyl carbonate (1, 0.25 mmol, 1 equiv.) was added
dropwise. The reaction mixture was stirred at 0 °C for 2 h. After
evaporation of the solvent in vacuo and flash chromatography (hex-
anes/EtOAc/NEt3 99:0:1 to 97:2:1) the pure product was obtained.
We used this reaction to prepare 21 for a control experi-
ment. The isolated allene was subjected to reaction condi-
tions identical to those used with the stannylated acetate
16. Although the products obtained, 17 and 18, were the
same as from the allene generated in situ, the reaction was
much slower. After 5 h an incomplete reaction had provided
a 2:1 mixture of 17 and 18 in a moderate 49% yield. This
also supports the idea that a Pd-coordinated allene is
formed in situ and is the reacting species.
General Procedure for Pd-Catalysed Bismetallations (GP2): It is
strongly recommended that the Pd(PPh3)4 be prepared freshly be-
fore use,[41] because only the pure catalyst (pale yellow crystals)
shows activity in this reaction. The same is true for the distannane
used. It should be purified by flash chromatography directly before
To verify the scope and limitations of this interesting
process, we also subjected the isopropyl-substituted allyl
acetate 22 to the same reaction conditions. Although the use.
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Eur. J. Org. Chem. 2011, 1047–1056

Reaction Behaviour of Stannylated Allylic Substrates
The stannylated allylic substrate 1 (0.5 mmol) was dissolved in abs.
THF (1 mL) under Ar in a Schlenk tube. A solution of Pd(PPh3)4
(12 mg, 10.4 μmol, 2 mol-%) in THF (0.5 mL) was added by sy-
ringe, followed either by the bimetal compound (0.55 or
1.05 mmol) or by the tin hydride (480 mg, 1.65 mmol). The reaction
mixture was warmed to 60 °C and the reaction was monitored by
TLC. After the reaction was complete, the solvent was removed in
vacuo and the crude product was purified by flash chromatography
(silica, hexanes/Et2O + 1% NEt3).
1 equiv.) after 2 h at 0 °C. After evaporation of the solvent in vacuo
and flash chromatography (hexanes/EtOAc/NEt3 99:0:1 to 97:2:1)
the desired product could be isolated in 94% yield (98 mg,
0.236 mmol) as a colourless oil. Rf (hexanes/EtOAc 8:2): 0.70. H
NMR (400 MHz, CDCl3): δ = 0.81–0.97 (m, 15 H, 1-H, 4-H), 1.31
1
3
3
(tq, J2,3 = 7.3, J2,1 = 7.2 Hz, 6 H, 2-H), 1.36–1.60 (m, 12 H, 3-
3
H, 9-H, 10-H), 2.27 (br. s, 4 H, 8-H), 2.98 (m, J7,Sn = 47.1 Hz, 2
H, 7-H), 5.17 (m, 3J5cis,Sn = 62.8 Hz, 1 H, 5-Hcis), 5.76 (m, 3J5trans,Sn
= 138.6 Hz, 1 H, 5-Htrans) ppm. 13C NMR (100 MHz, CDCl3): δ =
1
9.6 (t, J4,Sn = 336 Hz, C-4), 13.7 (q, C-1), 24.5 (t, C-10), 26.1 (t,
GC–MS Screening of Amines: Piperidine (43 mg, 0.5 mmol,
0.33 equiv.), 1-phenylethylamine (61 mg, 0.5 mmol, 0.33 equiv.), 4-
methoxyaniline (62 mg, 0.5 mmol, 0.33 equiv.) and naphthalene
(62 mg, 0.5 mmol, 0.33 equiv.) were dissolved in dry THF (2.5 mL)
in a Schlenk flask and cooled to –78 °C. In a second Schlenk flask,
[Pd(allyl)Cl]2 (5.5 mg, 15 μmol, 1 mol-%) and PPh3 (17.7 mg,
67 μmol, 4.5 mol-%) were dissolved in dry THF (5 mL) and the
mixture was stirred under argon at room temp. for 15 min. The
yellowish catalyst solution was then cooled to –78 °C, cinnamyl
methyl carbonate (618 mg, 3.0 mmol, 2.0 equiv.) was added, and
the resulting mixture was stirred for 15 min at –78 °C and then
added dropwise to the amine solution. Samples for GC–MS analy-
ses were taken after 1 h at –78 °C, 1 h at –20 °C, 1 h at 0 °C, 1 h at
room temp., 18 h at room temp. and 3 h at 60 °C and directly in-
jected in the GC–MS machine (Hewlett–Packard HP 5890 GC with
HP 591A mass detector, DB5 column, 30 m length, 0.25 mm in-
ternal diameter, 0.25 μm film, helium as carrier gas, injector:
250 °C, detector: 300 °C, temperature program: 60–175 °C,
5 °Cmin–1; 175–275, 15 °Cmin–1, 275 °C, 5 min). Starting materials
were identified by their retention times, products were identified by
their MS spectra, and naphthalene was used as a internal standard
to allow quantitative statements.
C-9), 27.5 (t, 3J2,Sn = 58 Hz, C-2), 29.2 (t, 2J3,Sn = 19 Hz, C-3), 54.7
(t, C-8), 69.8 (t, C-7), 124.9 (t, C-5), 155.8 (s, C-6) ppm. 119Sn
NMR (149.2 MHz, CDCl3): δ = –50.1 ppm. HRMS (CI): calcd. for
C20H41N120Sn 415.2261 [M]+; found 415.2273. C20H41NSn
(414.24): calcd. C 57.99, H 9.98, N 3.38; found C 57.89, H 10.04,
N 3.27.
4-[2-(Tributylstannyl)allyl]morpholine (6): This compound was ob-
tained by GP1 from morpholine (24 mg, 0.275 mmol, 1.1 equiv.)
and methyl 2-(tributylstannyl)allyl carbonate (1b, 101 mg,
0.25 mmol, 1 equiv.) after 2 h at 0 °C. After evaporation of the sol-
vent in vacuo and flash chromatography (hexanes/EtOAc/NEt3
99:0:1 to 97:2:1) the desired product could be isolated in 87% yield
(91 mg, 0.219 mmol) as a colourless oil. Rf (hexanes/EtOAc 8:2):
1
0.59. H NMR (400 MHz, CDCl3): δ = 0.81–0.98 (m, 15 H, 1-H,
3
3
4-H), 1.32 (tq, J2,3 = 7.4, J2,1 = 7.2 Hz, 6 H, 2-H), 1.47 (m, 6 H,
3
4
3-H), 2.36 (br. s, 4 H, 8-H), 3.05 (dd, J7,Sn = 46.5, J7,5cis = 1.2,
4J7,5trans = 1.2 Hz, 2 H, 7-H), 3.67 (t, J9,8 = 4.6 Hz, 4 H, 9-H),
3
3
2
4
5.22 (dt, J5cis,Sn = 61.5, J5cis,5transs = 2.8, J5cis,7 = 1.4 Hz, 1 H, 5-
H
cis), 5.79 (dt, 3J5trans,Sn = 135.6, 2J5trans,5cis = 2.8, 4J5trans,7 = 1.4 Hz,
1 H, 5-Htrans) ppm. 13C NMR (100 MHz, CDCl3): δ = 9.6 (t, J4,Sn
1
3
= 330 Hz, C-4), 13.7 (q, C-1), 27.5 (t, J2,Sn = 58 Hz, C-2), 29.2 (t,
2J3,Sn = 19 Hz, C-3), 53.7 (t, C-8), 67.1 (t, C-9), 69.4 (t, C-7), 126.3
(t, C-5), 154.1 (s, C-6) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ =
–48.9 ppm. HRMS (CI): calcd. for C19H39NO120Sn 417.2054 [M]+;
found 417.2044.
GC–MS Screening of Other Nucleophiles: Dimethyl methylmalon-
ate (87 mg, 0.5 mmol, 0.20 equiv.), succinimide (50 mg, 0.5 mmol,
0.20 equiv.), phenol (47 mg, 0.5 mmol, 0.20 equiv.), N-hydroxysuc-
cinimide (58 mg, 0.5 mmol, 0.20 equiv.), trifluoroacetamide (57 mg,
0.5 mmol, 0.20 equiv.) and naphthalene (62 mg, 0.5 mmol,
0.20 equiv.) were dissolved in dry THF (2.5 mL) under argon in a
Schlenk flask and the mixture was cooled to 0 °C. NaOMe
(135 mg, 2.5 mmol, 1 equiv.) was added and the mixture was stirred
for 15 min at 0 °C and then cooled to –78 °C. In a second Schlenk
flask, [Pd(allyl)Cl]2 (9.2 mg, 25 μmol, 1 mol-%) and PPh3 (29.5 mg,
0.11 mmol, 4.5 mol-%) were dissolved in dry THF (5 mL) and the
mixture was stirred under argon at RT for 15 min. The yellowish
catalyst solution was then cooled to –78 °C, cinnamyl methyl car-
bonate (618 mg, 3.0 mmol, 1.2 equiv.) was added, and the resulting
mixture was stirred for 15 min at –78 °C and then added dropwise
to solution 1 at –78 °C. Samples for GC–MS analyses were taken
and analysed as described for the screening of amines.
1-[2-(Tributylstannyl)allyl]pyrrolidine (7): This compound was ob-
tained by GP1 from pyrrolidine (20 mg, 0.275 mmol, 1.1 equiv.)
and methyl 2-(tributylstannyl)allyl carbonate (1b, 101 mg,
0.25 mmol, 1 equiv.) after 2 h at 0 °C. After evaporation of the sol-
vent in vacuo and flash chromatography (hexanes/EtOAc/NEt3
99:0:1 to 97:2:1) the desired product could be isolated in 86% yield
(86 mg, 0.215 mmol) as a colourless oil. Rf (hexanes/EtOAc 8:2):
1
0.59. H NMR (400 MHz, CDCl3): δ = 0.79–0.96 (m, 15 H, 1-H,
3
3
4-H), 1.31 (tq, J2,3 = 7.4, J2,1 = 7.2 Hz, 6 H, 2-H), 1.49 (m, 6 H,
3
3-H), 1.71 (m, 4 H, 9-H), 2.39 (br. s, 4 H, 8-H), 3.17 (m, J7,Sn
=
44.9 Hz, 2 H, 7-H), 5.14 (dt, 3J5cis,Sn = 63.3, 2J5cis,5trans = 2.6, 4J5cis,7
= 1.3 Hz, 1 H, 5-Hcis), 5.79 (dt, J5trans,Sn = 139.1, 2J5trans,5cis = 2.7,
3
4J5trans,7 = 1.3 Hz, 1 H, 5-Htrans) ppm. 13C NMR (100 MHz,
CDCl3): δ = 9.5 (t, C-4), 13.7 (q, C-1), 23.6 (t, C-9), 27.5 (t, C-2),
29.2 (t, C-3), 54.0 (t, C-8), 66.1 (t, C-7), 123.8 (t, C-5), 152.5 (s, C-
6) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –49.0 ppm. HRMS
(CI): calcd. for C19H39N120Sn 401.2104 [M]+; found 401.2152.
In Situ NMR Studies: The substrate 1b (41 mg, 0.1 mmol, 1 equiv.)
was dissolved in [D8]toluene (0.3 mL) in a NMR tube and the mix-
ture was cooled to 0 °C. A solution of [Pd(allyl)Cl]2 (0.37 mg,
1 μmol, 1 mol-%) and PPh3 (1.2 mg, 4.5 μmol, 4.5 mol-%) in [D8]-
toluene (0.3 mL) was cooled to 0 °C and added, directly before in-
sertion of the NMR tube with the mixture into the NMR machine
N,N-Diethyl-1-[2-(tributylstannyl)allyl]amine (8): This compound
was obtained by GP1 from diethylamine (20 mg, 0.275 mmol,
1.1 equiv.) and methyl 2-(tributylstannyl)allyl carbonate (1b,
101 mg, 0.25 mmol, 1 equiv.) after 2 h at 0 °C. After evaporation
of the solvent in vacuo and flash chromatography (hexanes/EtOAc/
NEt3 99:0:1 to 97:2:1) the desired product could be isolated in 90%
yield (90 mg, 0.224 mmol) as a colourless oil. Rf (hexanes/EtOAc
1
(Bruker DRX 500, 500 MHz, H). Measurements were taken over
one hour, every minute for the first 10 min, then every 2 min for
10 min, then every 4 min for 20 min and every 5 min for 20 min.
The residual solvent peak was used as internal reference for quanti-
fication.
1
1-[2-(Tributylstannyl)allyl]piperidine (5): This compound was ob-
tained by GP1 from piperidine (24 mg, 0.275 mmol, 1.1 equiv.) and
ethyl 2-(tributylstannyl)allyl carbonate (1a, 105 mg, 0.25 mmol,
8:2): 0.54. H NMR (400 MHz, CDCl3): δ = 0.80–0.94 (m, 15 H,
3
3
1-H, 4-H), 0.96 (t, J9,8 = 7.1 Hz, 6 H, 9-H), 1.31 (tq, J2,3 = 7.3,
3J2,1 = 7.2 Hz, 6 H, 2-H), 1.49 (m, 6 H, 3-H), 2.43 (q, 3J8,9 = 7.1 Hz,
Eur. J. Org. Chem. 2011, 1047–1056
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1053

C. Bukovec, A. O. Wesquet, U. Kazmaier
FULL PAPER
3
4
4
4 H, 8-H), 3.11 (dd, J7,Sn = 47.1, J7,5cis = J7,5trans = 1.4 Hz, 2 H, (tributylstannyl)allyl carbonate (1b, 101 mg, 0.25 mmol, 1 equiv.)
7-H), 5.18 (m, J5cis,Sn = 63.0, J5cis,5trans = 2.8, J5cis,7 = 1.4 Hz, 1 was added. In a second Schlenk flask, phenol (26 mg, 0.275 mmol,
1.1 equiv.) was dissolved in dry DMF (2 mL), after which NaH
(7 mg, 0.30 mmol, 1.2 equiv.) was added. The solution was cooled
(t, J4,Sn = 328 Hz, C-4), 11.0 (q, C-9), 13.7 (q, C-1), 27.5 (t, J2,Sn to –20 °C and the catalyst solution was added dropwise. The reac-
3
2
4
3
2
4
H, 5-Hcis), 5.79 (m, J5trans,Sn = 138.7, J5trans,5cis = 2.8, J5trans,7
=
1.4 Hz, 1 H, 5-Htrans) ppm. 13C NMR (100 MHz, CDCl3): δ = 9.5
1
3
2
= 58 Hz, C-2), 29.2 (t, J3,Sn = 19 Hz, C-3), 45.9 (t, C-8), 64.1 (t, tion mixture was allowed to warm to room temp. over 18 h. After
2J7,Sn = 34 Hz, C-7), 124.9 (t, J5,Sn = 27 Hz, C-5), 156.2 (s, C-
evaporation of the solvent in vacuo and flash chromatography (hex-
2
6) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –49.4 ppm. HRMS anes/EtOAc/NEt3 98:1:1) the desired product could be isolated in
(CI): calcd. for C19H41N120Sn 403.2261 [M]+; found 403.2265.
36% yield (38 mg, 0.090 mmol) as a colourless oil. Rf (hexanes/
1
3
EtOAc 8:2): 0.88. H NMR (500 MHz, CDCl3): δ = 0.88 (t, J1,2
N-(1-Phenylethyl)-2-(tributylstannyl)prop-2-en-1-amine (9): This
compound was obtained by GP1 from 1-phenylethylamine (33 mg,
0.275 mmol, 1.1 equiv.) and methyl 2-(tributylstannyl)allyl carbon-
ate (1b, 101 mg, 0.25 mmol, 1 equiv.) after 2 h at 0 °C. After evapo-
ration of the solvent in vacuo and flash chromatography (hexanes/
EtOAc/NEt3 99:0:1 to 97:2:1) the desired product could be isolated
in 84% yield (94 mg, 0.209 mmol) as a colourless oil. Rf (hexanes/
3
3
= 7.3 Hz, 9 H, 1-H), 0.96 (m, 6 H, 4-H), 1.31 (tq, J2,1 = 7.4, J2,3
= 7.3 Hz, 6 H, 2-H), 1.51 (m, 6 H, 3-H), 4.66 (m, 3J7,Sn = 30.2 Hz,
3
2 H, 7-H), 5.36 (m, J5cis,Sn = 60.3 Hz, 1 H, 5-Hcis), 5.98 (td,
3J5trans,Sn = 126.2, 4J5trans,7 = 1.8, 2J5trans,5cis = 1.7 Hz, 1 H, 5-Htrans),
3
3
3
6.89 (d, J9,10 = 8.6 Hz, 2 H, 9-H), 6.94 (dt, J11,10 = 7.3, J11,9
=
0.7 Hz, 1 H, 11-H), 7.28 (m, 2 H, 10-H) ppm. 13C NMR (126 MHz,
1
CDCl3): δ = 9.7 (t, J4,Sn = 334 Hz, C-4), 13.7 (q, C-1), 27.3 (t,
1
EtOAc 8:2): 0.56. H NMR (400 MHz, CDCl3): δ = 0.82–0.99 (m,
2
3J2,Sn = 57 Hz, C-3), 29.1 (t, J3,Sn = 20 Hz, C-2), 74.8 (t, C-7),
15 H, 1-H, 4-H), 1.27–1.35 (m, 9 H, 2-H, 9-H), 1.49 (m, 6 H, 3-
114.6 (d, C-9), 120.5 (d, C-11), 125.1 (t, C-5), 129.3 (d, C-10), 151.6
(s, C-6), 158.7 (s, C-8) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ =
–42.4 ppm. HRMS (CI): calcd. for C21H36O120Sn 367.1084 [M –
Bu]+; found 367.1111. C21H36OSn (423.20): calcd. C 59.60, H 8.57;
found C 59.86, H 8.68.
3
4
4
H), 3.23 (dd, J7,Sn = 40.7, J7,5cis = J7,5trans = 1.3 Hz, 2 H, 7-H),
3
3
3
3.75 (q, J8,9 = 6.6 Hz, 1 H, 8-H), 5.18 (dt, J5cis,Sn = 62.8, J5cis,5-
trans = 2.6, 4J5cis,7 = 1.3 Hz, 1 H, 5-Hcis), 5.77 (dt, 3J5trans,Sn = 136.5,
2J5trans,5cis = 2.5, 4J5trans,7 = 1.5 Hz, 1 H, 5-Htrans), 7.23 (m, 1 H, 13-
H), 7.29–7.34 (m, 4 H, 11-H, 12-H) ppm. 13C NMR (100 MHz,
1
1-[2-(Tributylstannyl)allyl]phthalimide (11): Pd(PPh3)4 (6 mg,
5.0 μmol, 2 mol-%) was dissolved in dry DMF (2 mL) in a Schlenk
flask and the mixture was stirred under nitrogen at room tempera-
ture for 15 min. The solution was cooled to 0 °C, after which
methyl 2-(tributylstannyl)allyl carbonate (1b, 101 mg, 0.25 mmol,
1 equiv.) was added. In a second Schlenk flask, phthalimide (41 mg,
0.275 mmol, 1.1 equiv.) was dissolved in dry DMF (2 mL) and
NaH (7 mg, 0.30 mmol, 1.2 equiv.) was added. The solution was
cooled to 0 °C and the catalyst solution was added dropwise. The
reaction mixture was allowed to warm to room temp. and then
stirred at 40 °C for 48 h. After evaporation of the solvent in vacuo
and flash chromatography (hexanes/EtOAc/NEt3 98:1:1) the de-
sired product could be isolated in 46% yield (55 mg, 0.115 mmol)
as a colourless oil. Rf (hexanes/EtOAc 8:2): 0.56. 1H NMR
CDCl3): δ = 9.7 (t, J4,Sn = 328 Hz, C-4), 13.7 (q, C-1), 24.2 (q, C-
3
2
9), 27.4 (t, J2,Sn = 57 Hz, C-2), 29.2 (t, J3,Sn = 20 Hz, C-3), 57.2
2
(t, C-7), 57.8 (d, C-8), 124.4 (t, J5,Sn = 25 Hz, C-5), 126.6 (d, C-
11), 126.8 (d, C-13), 128.3 (d, C-12), 145.9 (s, C-10), 154.9 (s, C-
6) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –46.8 ppm. HRMS
(CI): calcd. for C23H41N120Sn 451.2261 [M]+; found 451.2271.
Dimethyl 2-[2-(Tributylstannyl)allyl]malonate (10): Pd(PPh3)4
(6 mg, 5.0 μmol, 2 mol-%) was dissolved in dry DMF (2 mL) in a
Schlenk flask and the mixture was stirred under nitrogen at room
temperature for 15 min. The solution was cooled to 0 °C and
methyl 2-(tributylstannyl)allyl carbonate (1b, 101 mg, 0.25 mmol,
1 equiv.) was added. In a second Schlenk flask, dimethyl malonate
(36 mg, 0.275 mmol, 1.1 equiv.) was dissolved in dry DMF (2 mL)
and NaOMe (14 mg, 0.26 mmol, 1.05 equiv.) was added. The solu-
tion was cooled to 0 °C and the catalyst solution was added drop-
wise. The reaction mixture was allowed to warm to room temp.
over 18 h and then stirred for 48 h at room temp. After evaporation
of the solvent in vacuo and flash chromatography (hexanes/EtOAc/
NEt3 98:1:1) the desired product could be isolated in 43% yield
(49 mg, 0.106 mmol) as a colourless oil. Rf (hexanes/EtOAc 8:2):
3
(400 MHz, CDCl3): δ = 0.85 (t, J1,2 = 7.3 Hz, 9 H, 1-H), 0.93 (m,
3
3
6 H, 4-H), 1.27 (tq, J2,1 = 7.3, J2,3 = 7.3 Hz, 6 H, 2-H), 1.47 (m,
3
3
3
6 H, 3-H), 4.41 (dd, J7,Sn = 24.0, J7,5cis = 1.6, J7,5trans = 1.6 Hz,
3
2
4
2 H, 7-H), 5.26 (dt, J5cis,Sn = 58.1, J5cis,5trans = 1.6, J5cis,7
=
3
2
1.6 Hz, 1 H, 5-Hcis), 5.70 (dt, J5trans,Sn = 122.5, J5trans,5cis = 1.8,
4J5trans,7 = 1.7 Hz, 1 H, 5-Htrans), 7.71 (m, 2 H, 11-H), 7.85 (m, 2
H, 10-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 9.4 (t, J4,Sn
=
1
0.62. 1H NMR (400 MHz, CDCl3): δ = 0.89 (t, J1,2 = 7.3 Hz, 9
H, 1-H), 0.92 (m, 6 H, 4-H), 1.31 (tq, J2,1 = 7.3, J2,3 = 7.2 Hz, 6
3
3
332 Hz, C-4), 13.6 (q, C-1), 27.3 (t, J2,Sn = 58 Hz, C-3), 29.0 (t,
3
3
2J3,Sn = 20 Hz, C-2), 45.6 (t, J7,Sn = 55 Hz, C-7), 123.2 (d, C-10),
2
3
3
2
H, 2-H), 1.48 (m, 6 H, 3-H), 2.82 (ddd, J7,Sn = 39.1, J7,8 = 7.6,
125.4 (t, J5,Sn = 20 Hz, C-5), 132.1 (s, C-9), 133.9 (d, C-11), 147.4
3
3
3J7,5cis = 1.3, J7,5trans = 1.6 Hz, 2 H, 7-H), 3.53 (t, J8,7 = 7.6 Hz,
(s, C-6), 168.0 (s, C-8) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ =
–40.0 ppm. HRMS (CI): calcd. for C23H35NO2120Sn 420.0986 [M –
Bu]+; found 420.0935.
3
2
1 H, 8-H), 3.72 (s, 6 H, 10-H), 5.18 (dt, J5cis,Sn = 60.9, J5cis,5trans
4
3
= 2.0, J5cis,7 = 1.3 Hz, 1 H, 5-Hcis), 5.70 (dt, J5trans,Sn = 130.6,
4
2J5trans,5cis = 1.9, J5trans,7 = 1.5 Hz, 1 H, 5-Htrans) ppm. 13C NMR
3-(Tributylstannyl)-2-(trimethylsilyl)prop-1-ene (14): This com-
pound was obtained by GP2 (reaction time: 18 h) from 1g (213 mg,
0.50 mmol) and Bu3SnSiMe3 (128 mg, 0.35 mmol) as a colourless
liquid; yield: 99 mg (0.26 mmol, 70%). Rf (hexanes): 0.67. 1H NMR
1
(100 MHz, CDCl3): δ = 9.6 (t, J4,Sn = 334 Hz, C-4), 13.7 (q, C-1),
3
2
27.4 (t, J2,Sn = 57 Hz, C-3), 29.0 (t, J3,Sn = 20 Hz, C-2), 39.3 (t,
C-7), 51.3 (d, C-8), 52.4 (q, C-10), 127.1 (t, C-5), 150.5 (s, C-6),
169.4 (s, C-9) ppm. 119Sn NMR (149.2 MHz, CDCl3):
δ =
2
(400 MHz, CDCl3): δ = –0.05 (d, J1,Si = 6.8 Hz, 9 H, 1-H), 0.81
–42.4 ppm. HRMS (CI): calcd. for C20H38O4120Sn [M]+: 405.1088;
found 405.1121.
2
2
3
(dt, J8,Sn = 50.2, J8,7 = 8.2 Hz, 6 H, 8-H), 0.87 (t, J5,6 = 7.3 Hz,
9 H, 5-H), 1.28 (tq, 3J6,7 = 8.2, 3J6,5 = 7.3 Hz, 6 H, 6-H), 1.42–1.51
2
4
1-[2-(Tributylstannyl)allyl]phenoxide (1g): The stannylated phenyl
ether 1g could be obtained either through hydrostannation of phen-
ylpropargyl ether[9] or by allylic alkylation. Pd(PPh3)4 (6 mg,
5.0 μmol, 2 mol-%) was dissolved in dry DMF (2 mL) in a Schlenk
flask and the mixture was stirred under nitrogen at room tempera-
ture for 15 min. The solution was cooled to 0 °C and methyl 2-
(m, 6 H, 7-H), 1.87 (dd, J4,Sn = 62.7, J4,2cis = 1.1 Hz, 2 H, 4-H),
4
2
5.05 (dd, J2trans,Sn = 20.8, J2trans,2cis = 3.0 Hz, 1 H, 2-Htrans), 5.32
4
2
4
(ddt, J2cis,Sn = 19.8, J2cis,2trans = 3.0, J2cis,1 = 1.1 Hz, 1 H, 2-
Hcis) ppm. 13C NMR (100 MHz, CDCl3): δ = –1.59 (q, C-1), 9.73
(t, JSn = 307.4 Hz, C-8), 13.7 (q, C-5), 17.2 (t, C-4), 27.4 (t, JSn
=
54.3 Hz, C-7), 29.3 (t, JSn = 29.0 Hz, C-6), 120.0 (t, C-2), 152.1 (s,
1054
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 1047–1056

Reaction Behaviour of Stannylated Allylic Substrates
C-3) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –16.8 ppm.
HRMS (CI): calcd. for C14H31Si120Sn 347.1217 [M]+; found
347.1260.
29.3 (t, JSn = 19.1 Hz, C-8), 31.7 (d, JSn = 16.1 Hz, C-5), 43.4 (d,
C-4), 120.9 (t, C-2), 156.3 (s, JSn = 30.8 Hz, C-3) ppm. 119Sn NMR
(149.2 MHz, CDCl3): δ = –21.5 ppm. HRMS (CI): calcd. for
C17H37Si120Sn 389.1687 [M]+; found 389.1719. C21H46SiSn
(445.37): calcd. C 56.63, H 10.41; found C 55.92, H 10.10.
(E)-1-Phenyl-2,3-bis(tributylstannyl)prop-1-ene [(E)-18]: This com-
pound was obtained by GP2 (reaction time: 18 h) from 16 (235 mg,
0.50 mmol) and (Bu3Sn)2 (348 mg, 0.60 mmol) as a colourless li-
quid; yield: 250 mg (0.36 mmol, 71%). Rf (hexanes): 0.55. 1H NMR
All other dimetallated products are known compounds. The refer-
ences are given in the text.
2
3
(400 MHz, CDCl3): δ = 0.77 (dt, J4,Sn = 49.5, J4,3 = 8.2 Hz, 6 H,
3
3
4-H), 0.84 [t, J1(8),2(9) = 7.3 Hz, 9 H, 1(8)-H], 0.90 [t, J8(1),9(2)
=
2
3
Acknowledgments
7.3 Hz, 9 H, 8(2)-H], 0.93 (dt, J11,Sn = 50.1, J11,10 = 8.4 Hz, 6 H,
3
3
11-H), 1.23 [tq, J2(9),3(11) = 7.4, J2(9),1(8) = 7.3 Hz, 6 H, 2(9)-H],
Financial support by the Deutsche Forschungsgemeinschaft
(DFG) (Ka 880/9-2) and the Fonds der Chemischen Industrie is
gratefully acknowledged.
1.25–1.45 [m, 6 H, 9(2)-H], 1.45–1.67 (m, 12 H, 3-H, 10-H), 2.42
(ddd, J7,Sn = 67.8, J7,SnЈ = 67.8, J7,5 = 1.0 Hz, 2 H, 7-H), 6.19
2
3
4
3
4
4
(ddd, J5,Sn = 73.8, J5,Sn = 22.6, J5,7 = 1.0 Hz, 1 H, 5-H), 7.11
3
4
(tt, J15,14 = 7.2, J15,13 = 1.7 Hz, 1 H, 15-H), 7.22–7.31 (m, 4 H,
13-H, 14-H) ppm. 13C NMR (100 MHz, CDCl3): δ = 9.7 (t, JSn
316.1 Hz, C-4), 10.2 (t, JSn = 303.0 Hz, C-11), 13.6 (q, C-12), 13.7
(q, C-8), 19.8 (t, C-7), 27.4 (t, C-2), 27.5 (t, C-9), 29.1 (t, JSn
=
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2002, 114, 3002–3015; Angew. Chem. Int. Ed. 2002, 41, 2878–
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=
19.1 Hz, C-3), 29.2 (t, JSn = 19.1 Hz, C-10), 123.5 (d, C-15), 128.1
(d, C-13), 128.5 (d, C-14), 132.9 (d, C-5), 139.2 (s, C-12), 148.9 (s,
C-6) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –37.9, –19.9 ppm.
Selected signals from the stereoisomer (Z)-18: 1H NMR (400 MHz,
2
3
4
CDCl3): δ = 2.22 (ddd, J7,Sn = 59.5, J7,Sn = 59.5, J7,5 = 1.0 Hz,
3
4
4
2 H, 7-H), 7.06 (ddd, J5,Sn = 132.0, J5,Sn = 21.6, J5,7 = 1.0 Hz,
1 H, 5-H) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ = –49.6,
–14.3 ppm.
3-Phenyl-3-tributylstannyl-2-(trimethylsilyl)prop-1-ene (19): This
compound was obtained by GP2 (reaction time: 2 h) from 16
(282 mg, 0.61 mmol) and Bu3SnSiMe3 (182 mg, 0.50 mmol) as a
colourless liquid; yield: 98 mg (0.20 mmol, 85%). Rf (hexanes):
1
2
0.50. H NMR (400 MHz, CDCl3): δ = –0.06 (d, J1,Si = 6.5 Hz, 9
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3
3
H, 1-H), 0.79 (t, J12,11 = 8.2 Hz, 6 H, 12-H), 0.83 (t, J9,10
7.3 Hz, 6 H, 9-H), 1.23 (tq, J10,11 = 7.3, J10,9 = 7.3 Hz, 6 H, 10-
H), 1.26–1.45 (m, 6 H, 11-H), 3.56 (dd, J4,Sn = 60.7, J4,2cis
1.0 Hz, 1 H, 4-H), 5.60 (dd, J2trans,Sn = 9.5, J2trans,2cis = 2.3 Hz, 1
H, 2-Htrans), 5.63 (dd, J2cis,Sn = 8.5, J2cis,2trans = 2.3, J2cis,4
1.0 Hz, 1 H, 2-Hcis), 6.96 (tt, J8,7 = 7.3, J8,6 = 1.4 Hz, 1 H, 8-H),
=
3
3
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2
4
=
4
2
4
2
4
=
3
4
3
4
3
7.04 (dd, J6,7 = 8.5, J6,8 = 1.4 Hz, 2 H, 6-H), 7.15 (ddd, J7,6
=
3
4
7.3, J7,8 = 7.3, J7,7Ј = 1.8 Hz, 2 H, 7-H) ppm. 13C NMR
(100 MHz, CDCl3): δ = –1.4 (q, JSi = 51.4 Hz, C-1), 10.4 (t, JSn
=
296.4 Hz, C-12), 13.7 (q, C-9), 27.4 (t, JSn = 55.8 Hz, C-11), 29.0
(t, JSn = 19.1 Hz, C-10), 41.3 (d, JSn = 242.1 Hz, C-4), 123.5 (t, JSn
= 13.2 Hz, C-2), 126.5 (d, JSn = 21.3 Hz, C-7), 127.0 (d, C-8), 128.0
(d, JSn = 11.0 Hz, C-6), 144.6 (s, JSn = 31.5 Hz, C-5), 153.7 (s,
JSn = 30.8 Hz, C-3) ppm. 119Sn NMR (149.2 MHz, CDCl3): δ =
–10.0 ppm. HRMS (CI): calcd. for C20H35Si120Sn 423.1530 [M]+;
found 423.153.
4-Methyl-3-(tributylstannyl)-2-(trimethylsilyl)pent-1-ene (23): This
compound was obtained by GP2 (reaction time: 11 h) from 22[11]
(255 mg, 0.59 mmol) and Bu3SnSiMe3 (207 mg, 0.57 mmol) as a
colourless liquid; yield: 206 mg (0.46 mmol, 81%). Rf (hexanes):
1
2
0.67. H NMR (400 MHz, CDCl3): δ = 0.04 (d, J1,Si = 6.5 Hz, 9
2
3
H, 1-H), 0.81 (dt, J10,Sn = 48.7, J10,9 = 8.3 Hz, 6 H, 10-H), 0.86
(d, 3J6,5 = 6.5 Hz, 3 H, 6-H), 0.87 (t, 3J7,8 = 7.3 Hz, 9 H, 7-H), 0.95
3
3
3
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2
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2.3 Hz, 1 H, 2-Htrans), 5.36 (dd, J2a,Sn = 18.3, J2cis,5trans = 2.3 Hz,
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Eur. J. Org. Chem. 2011, 1047–1056
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1055

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Received: October 13, 2010
Published Online: December 30, 2010
1056
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© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2011, 1047–1056