Palladium-catalyzed cyclization of allylsilanes with nucleophilic displacement of the silyl group

Article abstract of DOI:10.1002/1521-3765(20011001)7:19<4097::AID-CHEM4097>3.0.CO;2-8

Allylsilanes containing hydroxy or tosylamide groups undergo palladium(II)-catalyzed cyclization to afford derivatives of tetrahydrofuran, piperidine, and pyrrolidine. This catalytic reaction proceeds through an (η³-allyl)palladium intermediate

Full text of DOI:10.1002/1521-3765(20011001)7:19<4097::AID-CHEM4097>3.0.CO;2-8

FULL PAPER
Palladium-Catalyzed Cyclization of Allylsilanes with Nucleophilic
Displacement of the Silyl Group
IstvaÂn MacsaÂri and KaÂlmaÂn J. SzaboÂ*[a]
Abstract: Allylsilanes containing hy-
droxy or tosylamide groups undergo
palladium(ii)-catalyzed cyclization to af-
ford derivatives of tetrahydrofuran, pi-
peridine, and pyrrolidine. This catalytic
reaction proceeds through an (h3-allyl)-
palladium intermediate that is generat-
ed by allylic displacement of the silyl
group of the allylsilane precursors. The
internal nucleophilic attack on the (h3-
allyl)palladium intermediates proceeds
with high chemo- and regioselectivity.
Benzoquinone and copper(ii) chloride
can be used for regeneration of the
palladium(ii) catalyst precursor. Mecha-
tration of chloride ligand and the sol-
vent. The structure and reactivity of the
key intermediates of the palladadesily-
lation process were studied by density
functional theory (DFT) calculations,
which showed that coordination of the
electrophilic palladium(ii) catalyst pre-
cursor to allylsilanes leads to a relatively
weak b-silicon effect. The DFT studies
also indicate that the cleavage of the
carbon ± silicon bond takes place by
coordination of a chloride ion to the
silicon atom.
nistic studies revealed that the copper(ii)
chloride reoxidant also activates the (h3-
allyl)palladium intermediate towards
nucleophilic attack. Kinetic studies on
the formation of the (h3-allyl)palladium
intermediates showed that the reaction
rate is highly dependent on the concen-
Keywords: cyclizations
´
density
functional calculations ´ heterocy-
cles ´ homogeneous catalysis ´ pal-
ladium
ester derivatives.[6d] Cerium(iv)-mediated oxidative ring clo-
sure of allylsilanes bearing hydroxy and amine groups has
been employed to prepare five- and eight-membered hetero-
cycles [Eq. (1)].[6e] Palladium(ii)-catalyzed oxidation of allyl-
silanes with UV light and molecular oxygen was used to
prepare a,b-unsaturated carbonyl compounds [Eq. (2)].[6f]
Introduction
Functionalized allylsilanes represent a useful class of reagents
that continue to show high potential in regio- and stereo-
controlled synthetic transformations.[1, 2] The highly selective
transformations of allylsilanes are usually performed by
electrophilic reagents.[3, 4] The driving force for electrophilic
attack on allylsilanes is the formation of a b-silicon-stabilized
carbocation intermediate.[5] Nucleophilic attack on allylsi-
lanes, however, does not benefit from this stabilization, and
this makes nucleophilic reagents less common in allylsilane
chemistry. Allylsilanes can be made accessible to nucleophilic
attack by employing organometallic reagents, electrochemical
methods, or oxidizing agents.[6] The metal-mediated processes
reported in the literature involve mercuration and thallation
reactions of trimethylallylsilane to give allylic alcohols and
amines.[6a±c, g±i]
SiMe3
R3
(H2C)n
R2
[CeIV]
(H2C)n
(1)
R3
+
(CH2)n
R2
X
XR1
R3
X
R1
R1
R2
Electrochemical oxidation of allylsilanes in the presence of
alcohols or carboxylic acids was reported to form ether or
Palladium catalysis proceeding by nucleophilic attack of
(h3-allyl)palladium complexes is a possible alternative for
nucleophilic displacement of the silyl group of allylsilanes.
Catalytic transformations involving (h3-allyl)palladium inter-
mediates have been widely applied in a number of important
chemical processes.[7±10] Awide range of allylic substrates, such
as allylic halides, acetates, carbonates, and carbamates, under-
go oxidative addition to palladium(0) to form (h3-allyl)palla-
dium complexes, which react with a great variety of nucleo-
philes. However, it is well known that many important allylic
Â
Â
[a] Dr. K. J. Szabo, I. Macsari
Department of Organic Chemistry
Arrhenius Laboratory
Stockholm University
106 91 Stockholm (Sweden)
Fax : (‡46)8154908
E-mail: kalman@organ.su.se
Supporting information for this article is available on the WWW under
http://www.wiley-vch.de/home/chemistry/ or from the author.
Chem. Eur. J. 2001, 7, No. 19
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4097

K. Szabó and I. Macsµri
FULL PAPER
substrates, including allylsilanes, do not undergo palladi-
um(0)-catalyzed allylic substitution. In fact, many palladi-
um(0)-catalyzed transformations have been successfully em-
ployed for preparation of functionalized allylsilanes.[10, 12]
In a preliminarily communication we presented a palladi-
um(ii)-catalyzed procedure based on internal nucleophilic
displacement of the silyl group of allylsilanes (Scheme 1).[11]
This catalytic procedure could be used for preparation of
substituted tetrahydrofuran derivatives in good yield.
O
ii
i
HO
SiMe3
SiMe3
9
8
Cl
iii
TsHN
SiMe3
SiMe3
10
11
NC
v
iv
H2N
SiMe3
SiMe3
10
13
SiMe3
12
vi
13
TsHN
14
O
NOH
R4
vii
R3R4
HO
R1R2
R3
R2
R1
SiMe3
cat.[PdII]
SiMe3
SiMe3
R5
R5
15
16
16
NHTs
CuCl2 or BQ
O
Scheme 1. Palladium(ii)-catalyzed cyclization of allylsilanes.
viii, vi
vii
SiMe3
17a, cis
17b, trans
Here we give a full account of our results on palladium(ii)-
catalyzed intramolecular cyclization of allylsilanes, and pres-
ent an extension of this process. We also demonstrate that the
employment of a silyl leaving group represents an interesting
alternative to the acetate and carbonate groups which are
commonly used in p-allylpalladium chemistry. To gain more
insight into the mechanistic details of this reaction, the key
steps of the catalytic transformation were investigated by
kinetic and theoretical (DFT) studies.
SiMe3
SiMe3
viii, vi
HON
O
3b
18
SiMe3
TsHN
18
19
Scheme 3. Preparation of toluenesulfonamides 11, 14, 17, and 19. i) NaBH4,
CeCl3 ´ 7H2O, THF/MeOH 3/1, RT, 1 h; ii) NCS, PPh3, THF, RT, 16 h; iii)
TsNHNa, TsNH2, DMSO, 608C, 16 h; iv) NaCN, DMSO, 908C, 16 h;
v) LiAlH4, Et2O, RT, 2.5 h; vi) TsCl, Et3N, CH2Cl2, 16 h, RT; vii) NaOAc,
NH2OH ´ HCl, H2O/EtOH 5/1, 608C, 16 h; viii) LiAlH4, THF, reflux, 16 h.
NCS ˆ N-chlorosuccinimide.
Results and Discussion
to amine 13 followed by reaction with TsCl to give sulfon-
amide 14. A different synthetic route was employed for the
preparation of amides 17 and 19: compounds 15 and 3b[12]
were transformed into the corresponding oximes 16 and 18
with NH2OH ´ HCl followed by reduction with LiAlH4 and
acylation with TsCl.
Synthesis of the starting materials: Allylsilane precursors with
an internal O nucleophile were prepared from allylsilanes 1 ±
3 (Scheme 2), which are readily available by a recently
reported palladium(0)-catalyzed alkylation process.[12] These
compounds were transformed into 6-trimethylsilylhex-4-en-1-
ol derivatives 4 ± 7 by Grignard reaction or reduction.
The above-mentioned synthetic procedures provide simple
access to the precursors of the catalytic reaction without
affecting the allylsilyl group. Note that the commonly used
substrates for palladium(0)-catalyzed allylic substitution re-
actions, such as allylic halides, acetates, and carbonates,
cannot be transformed by the above synthetic methods unless
their allylic functionality is protected.
OH
CO2Me
R
LiAlH4
SiMe3
Et2O
R
HO
Ph
MeO2C
SiMe3
4a, R=H
4b, R=Me
1a, R=H
1b, R=Me
SiMe3
NaBH4
R
THF/MeOH
OH
5a, R=H
SiMe3
R
Palladium(ii)-catalyzed cyclization of allylsilanes: It is well
documented that allylsilanes react with palladium(ii) salts to
give allylpalladium complexes.[14] Therefore, using this reac-
tion in a catalytic procedure requires regeneration of the
palladium(ii) catalyst precursor. Since nucleophilic attack on
an (h3-allyl)palladium complex involves reduction of palla-
dium(ii) to palladium(0), the catalyst precursor must be
reoxidized to maintain the catalytic cycle. Furthermore, the
palladadesilylation of the allylsilane substrate must be
sufficiently fast to obtain reasonable reaction times for the
catalytic processes.
Benzoquinone (BQ) and CuCl2 are frequently used reox-
idants in palladium(ii)-catalyzed procedures.[9] We found that
both reagents can be used in the cyclization reaction, and
accordingly developed two different methods for this catalytic
procedure. Diol 4a could be cyclized to give 20a in good yield
Ph
O
SiMe3
R
PhMgBr
THF
2a, R=H
2b, R=C5H11
Ph
Ph
OH
5b, R=H
7, R=C5H11
PhMgBr
THF
Ph
O
SiMe3
SiMe3
OH
3a
6
Scheme 2. Preparation of silylallyl alcohols 4 ± 7.
Allylsilanes functionalized with a toluene sulfonamide
(NHTs) group were prepared from 3b, 8, and 15. Aldehyde
8[13a, b] (Scheme 3) was reduced to alcohol 9, followed by
chlorination with NCS and PPh3 to give 10. Chloride 10 was
treated with TsNHNa to furnish amide 11. Compound 10 was
also treated with NaCN to give nitrile 12, which was reduced
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Pd-Catalyzed Cyclization of Allylsilanes
4097±4106
Table 2. Palladium(ii)-catalyzed cyclization of sulfonamides.
under mild, neutral conditions with CuCl2 as reoxidant
(Table 1, entry 1). However, using BQ as a reoxidant under
acidic conditions required an extended reaction time (Table 1,
entry 2) and gave 20a in poor yield. Since cyclization of 4a in
the presence of CuCl2 proceeds faster and in a better yield
than the BQ-mediated procedure, we used CuCl2 for the
cyclization of allylsilyl alcohols 4b and 5 ± 7.
Entry Substrate
Conditions[a] Product
Yield[b]
[%]
8C
h
TsHN
SiMe3
1
45
45
45
45
3.5
74
66
80
64
N
11
Ts
24
TsHN
SiMe3
14
2
4
2
2
4
N
Ts
25
Ts
NHTs
N
Table 1. Palladium(ii)-catalyzed cyclization of silylallyl alcohols 4 ± 7.
3
SiMe3
Entry Substrate
Conditions[a] Product
8C
Yield[b]
[%]
17a
NHTs
26a
Ts
h
N
OH
4
5
HO
SiMe3
1
2
3
25
25
25
1.5
86
40
62
HO
17b
SiMe3
26b
O
20a
4a
SiMe3
C5H11
4a
14[c]
2.5
20a
TsHN
45
80[c]
C5H11
N
19
OH
Ts
HO
27
HO
Ph
SiMe3
SiMe3
O
20b
4b
5a
[a] The reactions were conducted in tBuOH (5 mL) with allylsilane
(0.5 mmol), Li2[PdCl4] (0.025 mmol, 5 mol%), and CuCl2 (1.25 mmol).
[b] Yield of isolated product. [c] About 20% of the cis isomer was also
formed.
4
5
40
40
1.5
69
60
Ph
O
21a
OH
Ph
Ph
SiMe3
SiMe3
Ph
Ph
2.5[d]
O
21b
OH
OH
5b
6
Ph
6
7
20
20
14
53
Ph
O
22
closure reaction to afford fused ring systems 26a and 26b,
respectively.
SiMe3
C5H11
Ph
Ph
4[d]
66[e]
Ph
Ph
C5H11
O
23
7
OH
In the cyclization reactions the best results were obtained
by using alcohol solvents such as MeOH, iPrOH, and tBuOH.
In other solvents, such as acetonitrile, THF, DMSO, CH2Cl2,
and DMF slow reactions with poor yields were observed.
Cyclization of silylallyl alcohols 4 ± 7 could be readily
achieved in iPrOH. However, when the same solvent was
used for the ring closure of amides, considerable amounts of
acyclic isopropylallyl ether derivatives were also obtained.
Formation of this by-product is due to nucleophilic attack of
the solvent on the (h3-allyl)palladium intermediates of the
reaction. The fact that isopropylallyl ether derivatives are not
formed on cyclization of 4 ± 7 indicates that nucleophilic
attack by the internal hydroxy group is much faster than that
by an external secondary alcohol (e.g., the iPrOH solvent),
and it also shows that the tosylamides 11, 14, 17 and 19 are
much less nucleophilic than the corresponding alcohols 4 ± 7.
Therefore, for cyclization of tosylamides, tBuOH was used as
solvent, which is less nucleophilic than iPrOH. Conducting
the reaction in tBuOH leads to longer reaction times, but
formation of the alkylallyl ether by-products was completely
avoided.
[a] The reactions were conducted in iPrOH (5 mL) with allylsilane
(0.5 mmol), Li2[PdCl4] (0.025 mmol, 5 mol%) and CuCl2 (1.25 mmol).
[b] Yield of isolated product. [c] Allylsilane (0.5 mmol), Pd(OAc)2
(0.025 mmol, 5 mol%), BQ (1.1 mmol), and H3PO4 (0.135 mmol) in
CH2Cl2/MeOH (10/1, 5 mL). [d] The substrate was added by syringe pump
(0.5 and 3 h for 5b and 7, respectively) to the stirred reaction mixture.
[e] About 15% of the cis isomer was also formed.
Cyclization of alcohols 4 ± 7 was complete within 2 ± 4 h, but
a longer reaction time was required when methyl substituents
were present at the 3-position of the substrate (Table 1,
entry 6). The relatively short reaction time is particularly
important for cyclization of tertiary alcohols 5b and 7, since
these compounds readily eliminate water even under mild
reaction conditions. Since cyclization proceeded much faster
under neutral conditions than under acidic conditions (cf.
Table 1, entries 1 and 2), we attempted to use basic reaction
conditions to further accelerate the catalytic process. How-
ever, under these conditions only the unconverted starting
materials could be recovered after 24 h.
The palladium-catalyzed cyclization reaction was also
extended to allylsilanes containing toluenesulfonamide
groups (Table 2). Amides 11 and 19 were cyclized to give
substituted pyrrolidine derivatives in good yields. Cyclization
of the homologous 14 gave piperidine derivative 25. The
diastereomers of 17 were separated and subjected to the ring-
The regio- and chemoselectivity of the reaction are very
high. Ring closure of 4 ± 7, 11, 17, and 19 provided exclusively
five-membered rings, while formation of seven-membered
rings was not observed. Similarly, cyclization of 14 led only to
six-membered piperidine derivative 25. However, the diaster-
eoselectivity of the ring closure is poor, because the two
diastereomers of 20a 20b, 21a, 22, 26a, and 26b were formed
in approximately equal amounts.
Chem. Eur. J. 2001, 7, No. 19
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4099

K. Szabó and I. Macsµri
FULL PAPER
Mechanistic Aspects
100
80
The palladium(ii)-catalyzed nucleophilic substitution reaction
discussed above has three important steps: 1) palladadesily-
lation to give the (h3-allyl)palladium intermediate; 2) intra-
molecular nucleophilic attack on this complex; and 3)
reoxidation of the catalyst to complete the catalytic cycle
(Scheme 4). In particular steps 1 and 3 differ significantly
*
*
*
60
40
*
20
CuI
R3R4
HQ
R1R2
SiMe3
R5
5
10
Time / min
15
20
Oxidation
CuII
LnPdII
Figure 1. Rate of formation of the allylpalladium complex as a function of
~
&
*
the chloride ion concentration. Pd/Cl ratio: 10/1 ( ); 1/1 ( ); 1/2 ( ); and
1/10 (*).
Displacement
of the silyl
group
LnPd0
R3R4
HQ
R1R2
R4
increase in chloride concentration (Pd/Cl ˆ 1/10) decreased
the rate of complex formation.
R3
R2
R1
R5
Pd
R5
Cl
Q
The solvent effect of methanol on the rate of complex
formation was studied at low chloride concentrations (Pd/
Cl ˆ 10/1) in CDCl3. The reaction rate increased with
increasing amount of CD3OD in the solvent mixture (Fig-
ure 2). Addition of only 10% of CD3OD doubles the rate of
2
Nucleophilic
attack
Q = O, NTs
Scheme 4. Catalytic cycle of the ring-closure reaction.
from the mechanisms of the more common palladium(0)-
catalyzed nucleophilic displacement reactions. Therefore, we
studied the effects of ligands and solvents on the palladade-
silylation process, as well as the role of the reoxidants in
activating the nucleophilic attack.
100
80
60
Mechanistic investigations on the palladadesilylation reac-
tion: A rapid and clean palladadesilylation process is a
prerequisite for a synthetically useful catalytic nucleophilic
substitution of allylsilanes. The above results suggested that
the chloride concentration has a major influence on the rate of
the reaction. Using Li2[PdCl4] as catalyst precursor gave a
much faster catalytic reaction than with Pd(OAc)2 (cf. Table 1,
entries 1 and 2). The influence of the chloride ligand concen-
tration on the formation of the (h3-allyl)palladium complexes
was studied on a model system. The palladium(ii) precursor
for palladadesilylation was generated by mixing Pd(OAc)2
with various amounts of Ph4PCl in CDCl3. The progress of the
formation of the (h3-allyl)palladium complex from this
precursor and allyltrimethylsilane (Scheme 5) was monitored
by 1H NMR spectroscopy at 258C.
40
20
5
10
15
20
Time / min
Figure 2. Rate of formation of the allylpalladium complex as a function of
CD3OD concentration in CDCl3: 0% ( ); 10% ( ); 50% ( ).
~
&
*
complex formation. With 50% CD3OD complex formation
was complete after 15 min, and in pure CD3OD 28 was
completely converted to 29 in less than two minutes.
These results indicate that the employment of a moderately
high chloride concentration and alcohol solvents dramatically
increases the rate of the palladadesilylation process and hence
the overall catalytic reactions.
Pd(OAc)2,
Ph4PCl
SiMe3
28
Pd
2
CDCl3, RT
Cl
Reaction of the allylpalladium complexes: The allylpalladium
intermediate 30 was prepared by palladadesilylation of 5a
(Scheme 6). Complex 30 is air-stable and does not undergo
29
Scheme 5. Model reaction for the kinetic studies.
The palladadesilylation reaction was very slow in the
absence of chloride ligand. After 20 min less than 15% of
the allylsilane was converted to (h3-allyl)palladium complex
29. The rate of formation of 29 increased on increasing the Pd/
Cl ratio to 1/2 (Figure 1), and complete conversion of the
allylsilane substrate occurred within 10 min. However, a large
Ph
DDQ or CuCl2
iPrOH
Li2[PdCl4]
ROH, 0 oC, 6h
5a
21a
Pd
2
OH
Cl
30
Scheme 6. Preparation of allylpalladium complex 30 by palladadesilyla-
tion of 5a.
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Chem. Eur. J. 2001, 7, No. 19

Pd-Catalyzed Cyclization of Allylsilanes
4097±4106
spontaneous cyclization. Therefore, 30 must be activated to
allow nucleophilic attack by the hydroxy group. This activa-
tion could be achieved by addition of 2,3-dichloro-5,6-
dicyanobenzoquinone (DDQ) or CuCl2 to a solution of 30
in iPrOH. Thus CuCl2 has a dual role in the catalytic process:
1) it serves as an oxidizing agent for regeneration of the
palladium(ii) catalyst; 2) it activates the (h3-allyl)palladium
intermediates towards nucleophilic attack.
reaction by performing density functional calculations on the
structure and reactivity of adducts in which trimethylallylsi-
lane is coordinated to a PdCl3 (31a) or to a PdCl2 (32a)
2
fragment. Adduct 31a can be formed from PdCl4 by ligand
substitution of one of the chloride ligands. Dissociation of a
second chloride ion (32a) leads to the free coordination site
necessary for the h2 ! h3 conversion.
Interestingly, cyclization of 30 does not occur in the
presence of BQ, probably because BQ is a weaker activator
for nucleophilic attack on (h3-allyl)palladium complexes than
DDQ, especially in the presence of chloride ligands.[15]
Therefore, the BQ-mediated catalytic reaction should be
performed under chloride-free conditions (Table 1, entry 2).
Employment of BQ as activator and reoxidant requires acidic
reaction conditions, since a protonation step is involved in the
reduction of BQ to hydroquinone. However, using acidic
conditions and BQ as the reoxidant leads to a very slow
reaction with a low yield. This can be explained by the fact
that the ring closure involves deprotonation of the OH group,
which is hindered in the presence of acid. Cyclization with BQ
or CuCl2 does not proceed under basic conditions. Neutral
conditions gave the best results, which were achieved with
CuCl2 as reoxidant and activator. Employment of alcoholic
solvents was also beneficial, because the solvent molecules
can also act as weak bases that assist in the deprotonation of
the hydroxyl or amide groups.
Computational methods: The geometries were fully opti-
mized by employing a Becke-type[17a] three-parameter density
functional model B3PW91. This so-called hybrid functional
includes the exact (Hartree ± Fock) exchange, the gradient-
corrected exchange functional of Becke,[17a] and the more
recent correlation functional of Perdew and Wang[17b]. All
calculations were carried out with a double-z(DZ) ‡ P basis
set constructed from the LANL2DZ basis set[17c±e] by adding
one set of d-polarization functions to the heavy atoms
(exponents: C 0.63, Cl 0.514, O 1.154, Si 0.262) and one set
of diffuse d-functions on palladium (exponent: 0.0628). All
calculations were performed with the Gaussian 98 program
package.[17f]
Structure of (h2-allyl)palladium complexes: Harmonic vibra-
tion analysis of the fully optimized structures of 31a and 32a
gave only real frequencies, indicating that these complexes
represent minima on the potential energy surface. In these
complexes (Figure 3) the C Si bonds are perpendicular to the
allyl moiety (the C1-C2-C3-Si dihedral angles t are 91.2 and
99.78, respectively). Furthermore, the carbon ± silicon bonds
in both complexes are somewhat longer than a normal C Si
bond. Rotation of the silyl group by 908 leads to shortening of
the C Si bond and thermodynamic destabilization of the
complex. The geometrical and energy changes caused by the
908 rotation are more pronounced in 32a than in 31a.
Elongation of the C Si bond in 32a also weakens it, and this
facilitates the C Si bond cleavage required for formation of
the (h3-allyl)palladium intermediate. Clearly, the (h3-allyl)-
palladium intermediate is more easily formed from 32a than
from 31a.
Like the catalytic process, the stoichiometric cyclization
reaction proceeds with high regioselectivity, but the diaster-
eoselectivity is low. This can be explained by the fact that 30
readily undergoes syn ± anti isomerization and is therefore
present in two diastereomeric forms (Scheme 7). If the
H
H
Ph
Ph
H
Ph
O
Ph
O
H
OH
OH
H
H
Pd
Pd
H
H
Cl
Cl
2
2
cis-21a
syn-30
anti-30
trans-21a
Scheme 7. Cyclization is faster than syn ± anti isomerization.
The above results clearly indicate the presence of hyper-
conjugative interactions between the C Si bond and the p
system of the (h2-trimethylsilylallyl)palladium fragment in
32a. This interaction is very similar to the hyperconjugative
interaction between the C Si(s) orbital and the pp orbital in
b-silyl-substituted carbocations. This interaction forms the
basis of the b-silicon effect,[3, 5] which is the driving force of
electrophilic attack on vinyl- and allylsilanes. Theoretical
studies by Jorgensen et al.[5a] showed that the C Si bond is
strongly elongated (2.070 Š) in b-silyl carbocations, and that a
908 rotation of the silyl group from the conjugated upright
conformation (cf. 32a) to the unconjugated form (cf. 32b)
stability of the diastereomers were markedly different, the
complex would isomerize to the thermodynamically favored
form, which would undergo internal nucleophilic attack to
give one of the cyclic diastereomers.[16] However, in our
experiments the heterocyclic products were obtained as 1/1
mixtures of diastereomers, and this indicates that the thermo-
dynamic stabilities of the diastereomeric (h3-allyl)palladium
intermediates, such as syn-30 and anti-30, are about equal.
1
leads to a destabilization by 22.2 kcalmol . Clearly, electro-
Theoretical Studies on the Palladadesilylation
Process
philic attack (e.g., protonation) on an allylsilane generates
much larger b-silicon effect than the coordination of an
electrophilic palladium(ii) species such as PdCl2 (32a). This
also implies that the cleavage of the C Si bond is more
difficult in palladium(ii) adducts than in b-silyl carbocations.
The relatively weak b-silicon effect in 32a compared to b-
silyl carbocations (Scheme 8) can be explained by the fact that
The above studies on the palladium(ii)-catalyzed cyclization
of allylsilanes showed that formation of the allylpalladium
intermediate is influenced by the chloride concentration and
by the choice of the solvent. Therefore, we further inves-
tigated the mechanistic aspects of the palladadesilylation
Chem. Eur. J. 2001, 7, No. 19
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0947-6539/01/0719-4101 $ 17.50+.50/0
4101

K. Szabó and I. Macsµri
FULL PAPER
significantly to the cleavage of the C Si bond. On the other
hand, the approach of a free chloride ion to the silicon atom
leads to immediate C Si bond cleavage accompanied by
formation of chlorotrimethylsilane. This process leads to
formation of an (h3-allyl)palladium complex without an
activation barrier.
A more realistic model of the desilylation reaction in a
condensed phase involves coordination of two methanol
molecules to the attacking chloride ion (34, Figure 4).
According to harmonic frequency analysis, 34 represents a
minimum on the potential energy surface, and it is charac-
terized by a strongly elongated C Si bond. In fact, the C Si
bond in 34 (2.016 Š) is about as long as the C Si bond in b-
silyl carbocations (2.070 Š), and therefore it can be assumed
that the cleavage of the C Si bond in 34 is about as facile as in
b-silyl carbocations. The activation barrier to C Si bond
1
cleavage is extremely low (<0.5 kcalmol ), and therefore it
was not determined. Formation of the (h3-allyl)palladium
complex (35) and chlorotrimethylsilane from 34 is a highly
1
exothermic process ( 32.2 kcalmol ). Although this process
certainly requires a higher activation energy in a condensed
phase such as in methanol solution, and the reaction is less
exothermic than in this model calculation, it can be concluded
that the coordination of chloride to the silicon atom of 32a
considerably facilitates C Si bond cleavage.
The above theoretical results clearly indicate that the
location at which the chloride ion coordinates has a major
influence on the palladadesilylation process. The chloride ion
can coordinate to two centers in 32a. Coordination to the
silicon atom (34) facilitates C Si bond cleavage and forma-
tion of the (h3-allyl)palladium intermediate of the catalytic
reaction (35). However, coordination to palladium leads to
formation of 31a, in which the C Si bond is strong, and
therefore formation of the (h3-allyl)palladium intermediate is
not feasible. These conclusions are also in agreement with our
mechanistic results (Figure 1): at very low chloride concen-
trations complex 34 cannot be formed, and formation of the
(h3-allyl)palladium intermediate is slow. At very high chloride
concentration, dissociation of chloride ion from 31a is
hindered, and this also decelerates formation of the complex.
The alcohol solvents probably do not have a direct influence
on the palladadesilylation process. They react immediately
with chlorotrimethylsilane to give the alkyl trimethylsilyl
ether and release chloride ions for the palladadesilylation
process. This can explain the finding that addition of methanol
accelerates the formation of the (h3-allyl)palladium complex
even at low chloride concentration (Figure 2).
Figure 3. Selected B3PW91/LANL2DZ ‡ P geometrical parameters for
(h2-allyl)palladium complexes 31 and 32 (bond lengths in Š, angles in
degrees, energies in kcalmol 1).
Si
a)
E
Si
+
E
Si
b)
Pd
Si
Pd
Scheme 8. b-Silicon effect in a) b-silyl carbocations and b) in allyltri-
methylsilane ± PdCl2 adduct.
the electrophilic attack by palladium(ii) does not lead to
formation of a carbocation center at C2; instead, the
palladium atom coordinates to C1 C2 in an h2 manner. This
also means that the C Si(s) MO is not able to conjugate with
a low-lying pp MO, as in a b-silyl carbocation. Instead,
interaction of C Si(s) with a high-lying PdCC(p*) MO leads
to relatively weak hyperconjugation (Scheme 8).
Conclusion
We have described a new palladium(ii)-catalyzed cyclization
reaction involving nucleophilic displacement of the silyl group
of allylsilanes. This procedure is suitable for the preparation
of derivatives of tetrahydrofuran, pyrrolidine, and piperidine
under mild reaction conditions in good yields (Tables 1 and 2).
The cyclization reaction gave the best results under neutral
conditions with CuCl2 as activator and reoxidant. Mechanistic
studies indicate that the palladadesilylation of allylsilanes is
Factors promoting C Si bond cleavage: A weak electrostatic
interaction of the silicon atom of 32 with a methanol molecule
(Figure 4) leads to a slightly elongated C Si bond length of
1.941 Š (33). However, this interaction does not contribute
4102
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Chem. Eur. J. 2001, 7, No. 19

Pd-Catalyzed Cyclization of Allylsilanes
4097±4106
NMR spectra were recorded in CDCl3
(1H at 400 MHz and 13C at 100.5 MHz)
with CDCl3 (d(1H) ˆ 7.26, d(13C) ˆ
77.0) as internal standard. For column
chromatography, Merck silica gel 60
(230 ± 400 mesh) was used.
Reduction of 1a, b: The correspond-
ing diester[12] (2.1 mmol) in diethyl
ether (4.8 mL) was added dropwise
to
a suspension of LiAlH4 (0.21 g,
6.3 mmol) in diethyl ether (6 mL) at
08C. The mixture was stirred for 2.5 h
at room temperature. It was then
cooled to 08C, and water (0.2 mL)
was added. The resulting mixture was
allowed to warm to room temperature,
then an aqueous solution of NaOH
(15%, 0.2 mL) and water (0.61 mL)
were added.
A white slurry was
formed, which was filtered through
Celite and washed with EtOAc (3 Â
10 mL). The organic solvents were
removed, and the resulting oil was
purified by chromatography (diethyl
ether).
2-[(E)-4'-Trimethylsilylbut-2'-enyl]-
propane-1,3-diol (4a): Colorless crys-
tals (86% yield). M.p. 48 ± 498C;
1H NMR: d ˆ 5.45 (m, 1H; H3'), 5.23
(m, 1H; H2'), 3.83 (dd, J ˆ 10.8,
10.2 Hz, 2H; H1a, H3a), 3.66 (dd,
J ˆ 10.8, 10.4 Hz, 2H; H1b, H3b),
2.09 (s, 2H; OH), 2.00 (t, J ˆ 6.8 Hz,
2H; H1'), 1.82 (m, 1H; H2), 1.42 (d,
J ˆ 8.0 Hz, 2H; H4'), 0.01 (s, 9H;
Si(CH3)3); 13C NMR: d ˆ 128.9 (C3'),
125.9 (C2'), 66.5 (C1, C3), 42.9 (C2),
32.0 (C1'), 23.2 (C4'), 1.4 (Si(CH3)3);
elemental analysis (%) calcd for
C10H22O2Si (202.37):
C
59.35,
H
10.96; found: C 59.22, H 10.64.
2-Methyl-2-[(E)-4'-trimethylsilylbut-
2'-enyl]propane-1,3-diol (4b): Color-
less crystals (95% yield). M.p. 59 ±
608C; 1H NMR: d ˆ 5.47 (m, 1H;
H3'), 5.26 (m, 1H; H2'), 3.50 (m, 4H;
H1, H3), 2.38 (s, 2H; OH), 2.02 (t, J ˆ
7.4 Hz, 2H; H1'), 1.44 (d, J ˆ 8.0 Hz,
2H; H4'), 0.83 (s, 3H; CH3), 0.01 (s,
9H; Si(CH3)3); 13C NMR: d ˆ 130.1
(C3'), 123.7 (C2'), 70.7 (C1, C3), 40.0
(C2), 38.1 (C1'), 23.4 (C4'), 19.1 (CH3),
Figure 4. Selected B3PW91/LANL2DZ ‡ P geometrical parameters for 33, 34, and (h3-allyl)palladium complex
35 (bond lengths in Š, angles in degrees, energies in kcalmol 1).
‡
‡
strongly influenced by the concentration of chloride ions. The
optimal rate of formation of the (h3-allyl)palladium complex
is obtained with a Pd/Cl ratio of 1/2 (Figure 1). The DFT
calculations show that in the adduct formed by electrophilic
attack of palladium(ii) on allyltrimethylsilane (31a), the b-
silicon effect is relatively weak. Cleavage of the C Si bond
requires coordination of a chloride ion to the silicon atom
(34). On the other hand, a high chloride concentration leads to
formation of 31a, which slows down the palladadesilylation
process.
1.4 (Si(CH3)3). MS (CI): m/z (%): 226 (1) [M] , 201 (1) [M CH3] , 183
‡
‡
‡
(2) [C10H20OSi] , 143 (4) [C8H15O2] , 129 (10) [C7H13O2] , 93 (20), 73 (100)
‡
[C3H9Si] .
(E)-1-Phenyl-6-trimethylsilanylhex-4-en-1-ol (5a): NaBH4 (0.081 g,
2.15 mmol) was carefully added in small portions to a solution of ketone
2a (0.220 g, 0.89 mmol) and CeCl3 ´ 7H2O (0.33 g, 0.89 mmol) in THF/
methanol (3/1, 12 mL) at 08C. The resulting mixture was stirred at room
temperature for 1 h. Then it was quenched with a saturated aqueous
solution of NH4Cl (4.4 mL), filtered through Celite, and washed with
CH2Cl2 (3 Â 10 mL). The organic solvents were removed, and the aqueous
residue was diluted with brine and extracted with CH2Cl2 (3 Â 10 mL) and
diethyl ether (2 Â 10 mL). The combined organic layers were dried over
anhydrous MgSO4 and concentrated. The product was obtained after
chromatography (pentane/diethyl ether 4/1) as a colorless oil (79% yield).
1H NMR: d ˆ 7.34 (m, 4H; Ar), 7.28 (m, 1H; Ar), 5.44 (m, 1H; H5), 5.26
(m, 1H; H4), 4.69 (m, 1H; H1), 2.08 (m, 2H; H3), 1.91 ± 1.75 (brm, 2H;
H2), 1.42 (d, J ˆ 7.6 Hz, 2H; H6), 0.01 (s, 9H; Si(CH3)3); 13C NMR: d ˆ
145.0, 128.7, 127.7, 126.1 (Ar), 128.1 (C5), 127.3 (C4), 74.5 (C1), 39.7 (C2),
Experimental Section
The starting materials were purchased from Aldrich and Lancaster. All
solvents were freshly distilled prior to use. All reactions were conducted
under an argon atmosphere by employing standard manifold techniques.
‡
29.6 (C3), 23.2 (C6), 1.4 (Si(CH3)3); MS (CI): m/z (%): 249 (2) [M‡1] ,
Chem. Eur. J. 2001, 7, No. 19
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4103

K. Szabó and I. Macsµri
FULL PAPER
‡
‡
‡
‡
248 (2) [M] , 233 (3) [M CH3] , 205 (15) [C14H19Si] , 158 (17) [C12H14] ,
ether 9/1) to afford nitrile 12 as a colorless oil (88% yield). The NMR data
of 12 were identical with the literature data for the same product prepared
by an alternative procedure.[20] Nitrile 12 (0.086 g, 0.48 mmol) was reduced
to amine 13[20] by the procedure described for reduction of alcohols 4a, b to
give a colorless oil (86% yield). A solution of 13 (0.075 g, 0.4 mmol), TsCl
(0.152 g, 0.8 mmol), and Et3N (0.135 mL, 1.0 mmol) in CH2Cl2 (1.2 mL) was
stirred for overnight at room temperature. Thereafter, the reaction mixture
was diluted with diethyl ether (20 mL) and washed with water (10 mL). The
aqueous layer was extracted with diethyl ether (3 Â 8 mL), and the organic
layer was dried over anhydrous MgSO4. Subsequently, the solvent was
removed, and the residual oil was purified by chromatography (pentane/
diethyl ether 13/10) to give 14 as a colorless oil (93% yield). 1H NMR: d ˆ
7.75 (d, J ˆ 8.0 Hz, 2H; Ar), 7.30 (d, J ˆ 8.0 Hz, 2H; Ar), 5.33 (m, 1H; H6),
5.13 (m, 1H; H5), 4.11 (m, 1H; NH), 2.92 (m, 2H; H1), 2.43 (s, 3H;
ArCH3), 1.90 (m, 2H; H4), 1.44 (m, 2H; H2), 1.36 (d, J ˆ 8.0 Hz, 2H; H7),
1.29 (m, 2H; H3), 0.04 (s, 9H; Si(CH3)3); 13C NMR: d ˆ 143.7, 137.4,
130.0, 127.5 (Ar), 128.2 (C6), 127.2 (C5), 43.5 (C1), 32.5 (C4), 29.3 (C3), 27.2
(C2), 22.9 (C7), 21.9 (ArCH3), 1.6 (Si(CH3)3); MS (CI): m/z (%): 340 (2)
‡
‡
‡
143 (4) [C8H19Si] , 120 (9) [C8H8O] , 105 (100) [C7H5O] , 73 (50)
‡
[C3H9Si] .
Preparation of 5b, 6, and 7: Phenylmagnesium bromide (4.0 mmol) was
added dropwise to a solution of the corresponding ketone or aldehyde[12]
(0.5 mmol) in THF (1 mL) at 08C. The reaction mixture was stirred at
408C, and the progress of the reaction was monitored by TLC. When the
reaction was complete, it was quenched with a saturated aqueous solution
of NH4Cl. The resulting mixture was diluted with diethyl ether (10 mL) and
washed with brine. The organic layer was dried over anhydrous MgSO4,
concentrated, and purified by chromatography (pentane/diethyl ether 9/1).
(E)-1,1-Diphenyl-6-trimethylsilylhex-4-en-1-ol (5b): Colorless crystals
(68% yield). M.p. 54 ± 568C. 1H NMR: d ˆ 7.42 (m, 4H; Ar), 7.32 (m,
4H; Ar), 7.21 (m, 2H; Ar), 5.36 (m, 2H; H4, H5), 2.35 (m, 2H; H2), 2.00
(m, 2H; H2), 1.39 (d, J ˆ 7.6 Hz, 2H; H6), 0.02 (s, 9H; Si(CH3)3);
13C NMR: d ˆ 147.2, 128.3, 127.0, 126.3 (Ar), 128.5 (C5), 127.3 (C4), 78.8
(C1), 42.4 (C2), 28.0 (C3), 23.2 (C6), 1.4 (Si(CH3)3); MS (CI): m/z (%):
‡
‡
‡
‡
324 (1) [M] , 306 (6) [M H2O] , 232 (8) [C18H16] , 183 (20) [C13H11O] ,
‡
‡
‡
[M‡1] , 339 (7) [M] , 324 (10) [M CH3] , 256 (12), 228 (20), 180 (100)
‡
‡
‡
180 (100) [C14H12] , 165 (22) [C13H9] , 105 (24) [C7H5O] , 73 (13)
‡
‡
‡
[C10H18NSi] , 149 (12), 91 (12) [C7H7] , 73 (27) [C3H9Si] .
‡
[C3H9Si] .
Preparation of oximes 16 and 18: The corresponding aldehyde or ketone[12]
(4.1 mmol) in ethanol (1.5 mL) was added to a solution of NaOAc (0.330 g,
4.1 mmol) and NH2OH ´ HCl (0.422 g, 6.15 mmol) in water/ethanol (5/1,
8.6 mL) at 608C. After 1 h ethanol (4.5 mL) was added, and the mixture
was stirred overnight. Thereafter, the reaction mixture was diluted with ice
water (40 mL), extracted with diethyl ether, and dried over anhydrous
Na2SO4. Subsequently, the solvent was removed, and the residual yellow oil
was purified by column chromatography (pentane/diethyl ether).
(E)-2,2-Dimethyl-1-phenyl-6-trimethylsilylhex-4-en-1-ol (6): Colorless oil
(93% yield). 1H NMR: d ˆ 7.32 (m, 4H; Ar), 7.25 (m, 1H; Ar), 5.44 (m,
1H; H5), 5.36 (m, 1H; H4), 4.46 (d, J ˆ 2.8 Hz, 1H; H1), 2.12 (dd, J ˆ 13.6,
6.8 Hz, 1H; H3), 1.94 (dd, J ˆ 13.6, 6.8 Hz, 1H; H3), 1.45 (d, J ˆ 7.6 Hz, 2H;
H6), 0.88 (s, 3H; CH3), 0.80 (s, 3H; CH3), 0.01 (s, 9H; Si(CH3)3); 13C NMR:
d ˆ 142.2, 128.1, 127.8, 127.5 (Ar), 129.6 (C5), 125.0 (C4), 81.3 (C1), 43.0
(C2), 39.2 (C3), 24.0 (CH3), 23.5 (C6), 22.7 (CH3), 1.3 (Si(CH3)3); MS
‡
‡
‡
(CI): m/z (%): 277 (2) [M‡1] , 276 (3) [M] , 261 (15) [M CH3] , 203 (12)
‡
‡
‡
‡
2-[(E)-4'-Trimethylsilylbut-2'-enyl]cyclohexanone oxime (16): Compound
16 was obtained from 15 as a colorless oil (59% yield). 1H NMR: d ˆ 8.69
(s, 1H; OH), 5.40 (m, 1H; H3'), 5.21 (m, 1H; H2'), 2.75 (m, 1H; H6eq), 2.38
(m, 1H; H1'), 2.20 (brm, 2H; H2ax, H6ax), 2.04 (m, 1H; H1'), 1.85 (m, 1H;
H3eq), 1.69 (brm, 2H; H5eq, H4eq), 1.56 (m, 1H; H5ax), 1.49 (m, 1H; H4ax),
1.40 (d, J ˆ 8.0 Hz, 2H; H4'), 1.37 (m, 1H; H3ax), 0.02 (s, 9H; Si(CH3)3);
13C NMR: d ˆ 163.0 (C1), 128.5 (C3'), 126.6 (C2'), 42.8 (C2), 34.5 (C1'), 32.3
(C3), 26.5 (C5), 24.0 (C4), 23.4 (C6), 23.1 (C4'), 1.6 (Si(CH3)3); MS (CI):
[C14H19O] , 155 (24) [C9H19Si] , 113 (10) [C6H13Si] , 105 (100) [C7H5O] ,
‡
73 (62) [C3H9Si] .
(E)-1,1-Diphenyl-6-trimethylsilanyl-undec-4-en-1-ol (7): Colorless oil
(80% yield). 1H NMR: d ˆ 7.42 (m, 4H; Ar), 7.32 (m, 4H; Ar), 7.21 (m,
2H; Ar), 5.36 (m, 2H; H4, H5), 2.35 (m, 2H; H2), 2.00 (m, 2H; H3), 1.44 ±
1.13 (brm, 9H; H6 ± H10), 8.88 (t, J ˆ 7.2 Hz, 3H; H11), 0.05 (s, 9H;
Si(CH3)3); 13C NMR: d ˆ 147.2, 128.3, 127.0, 126.3 (Ar), 132.9 (C5), 127.6
(C4), 78.8 (C1), 42.6 (C2), 33.6 (C6), 32.2 (C7), 29.5 (C8), 29.3 (C9), 28.2
(C3), 23.1 (C10), 14.7 (C11), 2.6 (Si(CH3)3); elemental analysis (%) calcd
for C26H38OSi (394.68): C 79.12, H 9.70; found: C 78.97, H 9.87.
‡
‡
‡
m/z (%): 240 (1) [M‡1] , 239 (4) [M] , 224 (42) [M CH3] , 210 (13)
‡
‡
‡
[C11H20NOSi] , 166 (100) [C10H16NO] , 113 (7) [C6H13Si] , 73 (68)
‡
[C3H9Si] .
N-[(E)-6-Trimethylsilylhex-4-enyl]toluene-4-sulfonamide (11): Aldehyde
8[13a,b] was reduced by NaBH4 to alcohol 9 (93% yield) by the method
described for reduction of alcohol 5a. The NMR data for 9 were identical
with those given in the literature for the same compound prepared by an
alternative procedure.[18] Alcohol 9 was chlorinated by the following
procedure: PPh3 (0.904 g, 3.4 mmol) in THF (4 mL) was added to a
suspension of N-chlorosuccinimide (0.464 g, 3.4 mmol) in THF (4 mL) at
08C. The resulting pink slurry was stirred at room temperature for 0.5 h,
followed by addition of alcohol 9 in THF (4 mL), and this mixture was
stirred overnight at the same temperature. Thereafter, the solvent was
removed, and the crude product was purified by column chromatography
(pentane) to give 10 (81% yield). The NMR data of this product were
identical with the literature data for the same compound prepared by an
alternative procedure.[19] A solution of 10 (0.26 g, 1.36 mmol), TsNH2
(0.233 g, 1.36 mmol), and TsNHNa (0.263 g, 1.36 mmol) in DMSO (6 mL)
was stirred for 16 h at 608C. Thereafter, the reaction mixture was diluted
with brine and extracted with diethyl ether. The solvent was removed, and
purification by chromatography (pentane/diethyl ether 2/1) afforded 11 as
a colorless oil (68% yield). 1H NMR: d ˆ 7.75 (d, J ˆ 8.0 Hz, 2H; Ar), 7.30
(d, J ˆ 8.0 Hz, 2H; Ar), 5.33 (m, 1H; H5), 5.10 (m, 1H; H4), 4.53 (t, J ˆ
2.0 Hz, 1H; NH), 2.92 (dd, J ˆ 13.2, 6.8 Hz, 2H; H1), 2.42 (s, 3H; ArCH3),
1.94 (dd, J ˆ 13.8, 7.0 Hz, 2H; H3), 1.48 (m, 2H; H2), 1.34 (d, J ˆ 8.0 Hz,
2H; H6), 0.05 (s, 9H; Si(CH3)3); 13C NMR: d ˆ 143.6, 137.4, 130.0, 127.4
(Ar), 127.9 (C5), 127.3 (C4), 43.0 (C1), 30.0 (C2, C3), 23.0 (C6), 21.8
(ArCH3), 1.7 (Si(CH3)3); elemental analysis (%) calcd for C16H27NO2SSi
(325.56): C 59.03, H 8.36, N 4.30; found: C 58.86, H 8.38, N 4.44.
(E)-2,2-Dimethyl-6-trimethylsilylundec-4-enal oxime (18): Compound 18
was prepared from 3b as a pale yellow oil (87% yield). 1H NMR: d ˆ 7.49
(s, 1H; OH), 7.33 (s, 1H; H1), 5.19 (m, 2H; H5, H4), 2.10 (d, J ˆ 6.0 Hz,
2H; H3), 1.44 ± 1.10 (brm, 9H; H6 ± 10), 1.06 (s, 6H; 2  CH3), 0.86 (t, J ˆ
7.2 Hz, 3H; H11), 0.04 (s, 9H; Si(CH3)3); 13C NMR: d ˆ 159.6 (C1), 136.0
(C5), 123.0 (C4), 45.0 (C3), 37.4 (C2), 33.6 (C6), 32.0 (C9), 29.5 (C8), 29.3
(C7), 25.4 (CH3), 25.3 (CH3), 23.0 (C10), 14.5 (C11), 2.8 (Si(CH3)3); MS
‡
‡
‡
(CI): m/z (%): 283 (2) [M] , 282 (5) [M 1] , 266 (10) [M OH] , 210 (8)
‡
‡
‡
[C13H24NO] , 159 (25), 141 (22) [C8H17Si] , 73 (27) [C3H9Si] .
Preparation of sulfonamides 17 and 19: The oximes were reduced by a
procedure similar to the reduction described for preparation of 4a, b. The
modifications were that THF was used as solvent and the reaction mixture
was heated to reflux overnight. The amine intermediates were used without
further purification. The acylation with TsCl was performed by the
procedure described for preparation of 14.
N-{2-[(E)-4'-Trimethylsilylbut-2'-enyl)]cyclohexyl}toluene-4-sulfonamide
(17) was obtained as a 2/1 mixture of diastereomers in 64% yield. For
identification of the diastereomers 17a and 17b, we used the NMR data
given for cis- and trans-N-tosyl-2-allylcyclohexylamine.[21] According to the
literature data, the d(H1) signal of cis-N-tosyl-2-allylcyclohexylamine is
observed at lower field than the that of the trans isomer. cis-17a: Colorless
1
crystals, m.p. 116 1188C. H NMR: d ˆ 7.75 (d, J ˆ 8.0 Hz, 2H; Ar), 7.28
(d, J ˆ 8.0 Hz, 2H; Ar), 5.26 (m, 1H; H3'), 4.98 (m, 1H; H2'), 4.46 (d, J ˆ
8.4 Hz, 1H; NH), 3.43 (m, 1H; H1), 2.42 (s, 3H; ArCH3), 1.84 (m, 2H;
H1'), 1.60 ± 1.06 (brm, 10H; H2 ± 6), 1.33 (d, J ˆ 8.0 Hz, 2H; H4'), 0.04 (s,
9H; Si(CH3)3); 13C NMR: d ˆ 143.5, 138.9, 130.0, 127.4 (Ar), 128.4 (C3'),
126.5 (C2'), 53.7 (C1), 41.2 (C2), 34.6 (C1'), 30.9 (C3), 27.3 (C6), 24.1 (C4),
23.1 (C4'), 21.9 (ArCH3), 21.5 (C5), 1.6 (Si(CH3)3). trans-17b: 1H NMR:
d ˆ 7.76 (d, J ˆ 8.0 Hz, 2H; Ar), 7.26 (d, J ˆ 8.0 Hz, 2H; Ar), 5.26 (m, 1H;
H3'), 4.99 (m, 1H; H2'), 4.45 (d, J ˆ 8.8 Hz, 1H; NH), 2.83 (m, 1H; H1),
2.41 (s, 3H; ArCH3), 1.75 (m, 2H; H1'), 1.59 (brm, 4H; H3 ± H6eq), 1.35 (d,
N-[(E)-7-Trimethylsilylhept-5-enyl]toluene-4-sulfonamide (14): Chloride
10 (0.11 g, 0.58 mmol) and NaCN (0.088 g, 1.8 mmol) in DMSO (3 mL) were
stirred overnight at 908C. Thereafter, the reaction mixture was diluted with
water (20 mL) and extracted with diethyl ether (5 Â 10 mL) and CH2Cl2
(2 Â 10 mL). The combined organic layers were dried over anhydrous
MgSO4, concentrated, and purified by chromatography (pentane/diethyl
4104
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0719-4104 $ 17.50+.50/0
Chem. Eur. J. 2001, 7, No. 19

Pd-Catalyzed Cyclization of Allylsilanes
4097±4106
J ˆ 8.0 Hz, 2H; H4'), 1.23 (brm, 3H; H4 ± H6ax), 0.88 (m, 1H; H3ax), 0.04
(s, 9H; Si(CH3)3); 13C NMR: d ˆ 143.4, 138.9, 129.9, 127.3 (Ar), 128.6 (C3'),
126.2 (C2'), 57.4 (C1), 43.8 (C2), 36.0 (C1'), 34.7 (C3), 31.0 (C6), 25.5 (C4),
25.3 (C5), 23.1 (C4'), 21.9 (ArCH3), 1.6 (Si(CH3)3); elemental analysis
(%) calcd for C20H33NO2SSi (379.65): C 63.27, H 8.76, N 3.69; found: C
63.45, H 8.56, N 3.73.
2,2-Diphenyl-5-vinyltetrahydrofuran (21b): Colorless crystals, m.p. 68 ±
1
698C. H NMR: d ˆ 7.49 ± 7.17 (m, 10H), 5.97 (m, 1H; CHCH2), 5.29 (dt,
J ˆ 17.2, 1.2 Hz, 1H; CHCH2), 5.12 (dt, J ˆ 10.4, 1.2 Hz, 1H; CHCH2), 4.61
(q, J ˆ 6.8 Hz, 1H; H5), 2.70 ± 2.52 (m, 2H; H3), 2.11 (m, 1H; H4), 1.77 (m,
1H; H4); 13C NMR: d ˆ 147.1, 146.7, 128.4, 128.2, 126.9, 126.8, 126.1, 126.0
(Ar), 139.6 (CHCH2), 115.7 (CHCH2), 88.8 (C2), 80.4 (C5), 38.9 (C3), 32.4
‡
‡
‡
(C4); MS (EI): m/z (%): 251 (7) [M‡1] , 250 (17) [M] , 234 (35) [C18H18] ,
N-[(E)-2,2-Dimethyl-6-trimethylsilylundec-4-enyl]toluene-4-sulfonamide
(19): Compound was obtained as a colorless oil (87% yield). 1H NMR: d ˆ
7.74 (d, J ˆ 8.0 Hz, 2H; Ar), 7.29 (d, J ˆ 8.0 Hz, 2H; Ar), 5.12 (m, 2H; H5,
H4), 4.43 (brs, 1H; NH), 2.67 (d, J ˆ 6.8 Hz, 2H; H1), 2.42 (s, 3H; ArCH3),
1.88 (d, J ˆ 6.4 Hz, 2H; H3), 1.40 ± 1.10 (brm, 9H; H6 ± 10), 0.86 (t, J ˆ
7.2 Hz, 3H; H11), 0.83 (s, 6H; 2 Â CH3), 0.09 (s, 9H; Si(CH3)3); 13C NMR:
d ˆ 143.5, 137.5, 130.0, 127.4 (Ar), 135.8 (C5), 123.2 (C4), 53.3 (C1), 43.5
(C3), 37.8 (C2), 33.6 (C6), 32.0 (C9), 29.3 (C8), 29.0 (C7), 25.2 (CH3), 25.1
(CH3), 23.0 (C10), 21.8 (ArCH3), 14.5 (C11), 2.8 (Si(CH3)3). MS (CI): m/z
‡
‡
‡
182 (33) [C13H10O] , 180 (100) [C14H12] , 173 (53) [C12H13O] , 154 (37), 105
‡
‡
‡
(73) [C7H5O] , 77 (37) [C6H5] , 68 (32) [C5H8] . For alternative procedure
for preparation of 21b, see ref. [22]
3,3-Dimethyl-2-phenyl-5-vinyltetrahydrofuran (22): Colorless oil. Cis iso-
mer: 1H NMR: d ˆ 7.40 ± 7.25 (m, 5H), 6.08 (m, 1H; CHCH2), 5.37 (dt, J ˆ
17.2, 1.6 Hz, 1H; CHCH2), 5.17 (dt, J ˆ 10.4, 1.6 Hz, 1H; CHCH2), 4.57 (s,
1H; H2), 4.52 (m, 1H; H5), 2.07 (m, 1H; H4), 1.71 (m, 1H; H4), 1.19 (s,
3H; CH3), 0.64 (s, 3H; CH3). 13C NMR: d ˆ 139.2 (CHCH2), 139.8, 128.1,
127.4, 126.6 (Ar), 115.4 (CHCH2), 90.0 (C2), 78.1 (C5), 47.5 (C3), 43.0 (C4),
‡
‡
‡
(%): 424 (4) [M‡1] , 423 (12) [M] , 408 (9) [M CH3] , 366 (11)
1
‡
‡
‡
27.3, 25.2 (CH3). Trans isomer: H NMR: d ˆ 7.40 ± 7.25 (m, 5H), 5.97 (m,
[C19H32NO2SSi] , 256 (34) [C13H22NO2S] , 228 (12) [C11H18NO2S] , 180
(11) [C13H24] , 133 (100), 91 (12) [C7H7] , 74 (62), 73 (30) [C3H9Si] .
‡
‡
‡
1H; CHCH2), 5.30 (dt, J ˆ 17.2, 1.4 Hz, 1H; CHCH2), 5.11 (dt, J ˆ 10.4,
1.4 Hz, 1H; CHCH2), 4.72 (m, 1H; H5), 4.66 (s, 1H; H2), 2.07 (m, 1H; H4),
1.77 (m, 1H; H4), 1.13 (s, 3H; CH3), 0.69 (s, 3H; CH3); 13C NMR: d ˆ 140.2
(CHCH2), 139.8, 127.9, 127.4, 126.6 (Ar), 114.8 (CHCH2), 88.9 (C2), 78.3
(C5), 48.7 (C3), 43.7 (C4), 25.5, 22.4 (CH3); MS (EI): m/z (%): 203 (50)
Representative procedure for palladium(ii)-catalyzed cyclization: The
corresponding allylsilane (0.5 mmol), Li2[PdCl4] (0.007 g, 0.025 mmol,
5 mol%), and CuCl2 (0.168 g, 1.25 mmol) in iPrOH or tBuOH (5 mL)
were stirred for the temperatures and times listed in Tables 1 and 2. When
the reaction was complete, the reaction mixture was diluted with diethyl
ether (25 mL) and extracted with brine (2 Â 10 mL), followed by drying
over anhydrous MgSO4. The solvent was removed, and the products were
purified by chromatography (pentane/diethyl ether).
‡
‡
‡
‡
[M‡1] , 202 (20) [M] , 201 (100) [M 1] , 185 (96) [C14H17O] , 159 (10)
‡
‡
‡
‡
[C11H11O] , 125 (10) [C8H13O] , 96 (7) [C7H12] , 81 (39) [C6H9] .
(E/Z)-5-(Hept-1'-enyl)-2,2-diphenyltetrahydrofuran (23): Colorless oil. E
isomer: 1H NMR: d ˆ 7.49 ± 7.17 (m, 10H), 5.75 (m, 1H; H1'), 5.57 (m, 1H;
H2'), 4.55 (q, J ˆ 7.2 Hz, 1H; H5), 2.72 ± 2.52 (m, 2H; H3), 2.06 (m, 3H; H4,
H3'), 1.75 (m, 1H; H4), 1.45 ± 1.27 (m, 6H; H4' ± H6'), 0.90 (t, J ˆ 6.8 Hz,
3H; H7'); 13C NMR: d ˆ 147.3, 146.9, 128.3, 128.2, 126.8, 126.7, 126.2 (Ar),
133.2 (C1'), 131.2 (C2'), 88.5 (C2), 80.6 (C5), 39.4 (C3), 32.9 (C4), 32.6 (C5'),
31.9 (C3'), 29.2 (C4'), 23.0 (C6'), 14.5 (C7'); Z isomer: 1H NMR: d ˆ 7.49 ±
7.17 (m, 10H), 5.57 (m, 1H; H1' and H2'), 4.90 (q, J ˆ 7.2 Hz, 1H; H5),
2.72 ± 2.52 (m, 2H; H3), 2.06 (m, 3H; H4 and H3'), 1.75 (m, 1H; H4), 1.45 ±
1.27 (m, 6H; H4'-6'), 0.90 (t, J ˆ 6.8 Hz, 3H; H7'); 13C NMR: d ˆ 147.3,
146.9, 128.3, 128.2, 126.8, 126.7, 126.2 (Ar), 133.2 (C1'), 131.2 (C2'), 88.5
(C2), 75.2 (C5), 39.8 (C3), 33.3 (C4), 32.6 (C5'), 29.8 (C3'), 28.1 (C4'), 23.0
(C6'), 14.5 (C7'); elemental analysis (%) calcd for C23H28O (320.47): C
86.20, H 8.81; found C 86.01, H 8.99.
4-Hydroxymethyl-2-vinyltetrahydrofuran (20a): Colorless oil. cis isomer:
1H NMR: d ˆ 5.86 (m, 1H; CHCH2), 5.25 (dt, J ˆ 16.8, 1.4 Hz, 1H;
CHCH2), 5.11 (dt, J ˆ 10.4, 1.4 Hz, 1H; CHCH2), 4.28 (m, 1H; H2), 3.86
(dd, J ˆ 8.8, 7.6 Hz, 1H; H5), 3.75 (dd, J ˆ 8.8, 5.6 Hz, 1H; H5), 3.60 (m,
2H; CH2OH), 2.52 (m, 1H; H4), 2.20 (m, 1H; H3), 1.34 (m, 1H; H3).
13C NMR: d ˆ 138.9 (CHCH2), 116.2 (CHCH2), 80.9 (C2), 70.9 (C5), 65.5
1
(CH2OH), 42.5 (C4), 35.7 (C3); trans isomer: H NMR: d ˆ 5.82 (m, 1H;
CHCH2), 5.23 (dt, J ˆ 16.8, 1.4 Hz, 1H; CHCH2), 5.09 (dt, J ˆ 10.4, 1.4 Hz,
1H; CHCH2), 4.38 (q, J ˆ 7.2 Hz, 1H; H2), 4.03 (dd, J ˆ 8.8, 7.0 Hz, 1H;
H5), 3.60 (m, 3H; H5, CH2OH), 2.52 (m, 1H; H4), 1.89 (m, 1H; H3), 1.80
(m, 1H; H3). 13C NMR: d ˆ 139.1 (CHCH2), 115.6 (CHCH2), 79.7 (C2),
70.8 (C5), 65.0 (CH2OH), 41.8 (C4), 35.1 (C3); MS (CI): m/z (%): 130 (6)
1
1-(Toluene-4-sulfonyl)-2-vinylpiperidine (25): Colorless oil. H NMR: d ˆ
‡
‡
‡
‡
[M‡2] , 129 (5) [M‡1] , 115 (14) [C6H11O2] , 94 (16), 81 (8) [C6H9] , 79
7.67 (d, J ˆ 8.0 Hz, 2H; Ar), 7.25 (d, J ˆ 8.0 Hz, 2H; Ar), 5.68 (m, 1H; H1'),
5.16 (dt, J ˆ 17.5, 1.5 Hz, 1H; CHCH2), 5.13 (dt, J ˆ 10.5, 1.5 Hz, 1H;
CHCH2), 4.58 (brs, 1H; H2), 3.66 (d, J ˆ 13.6 Hz, 1H; H6eq), 2.98 (ddd, J ˆ
13.2, 12.8, 2.4 Hz, 1H; H6ax), 2.40 (s, 3H; ArCH3), 1.70 ± 1.36 (brm, 6H;
H3 ± 5); 13C NMR: d ˆ 143.2, 138.2, 129.8, 127.6 (Ar), 135.8 (CHCH2), 117.4
(CHCH2), 55.3 (C6), 41.9 (C2), 30.0 (C3), 25.3 (C5), 21.8 (ArCH3), 19.4
(C4). For alternative literature procedure for preparation of 25, see ref. [23]
‡
‡
‡
(55), 75 (54) [C3H7O2] , 73 (100) [C4H9O] , 67 (53) [C5H7] .
4-Hydroxymethyl-4-methyl-2-vinyltetrahydrofuran (20b): Colorless oil. cis
isomer: 1H NMR: d ˆ 5.85 (m, 1H; CHCH2), 5.23 (dt, J ˆ 17.2, 1.4 Hz, 1H;
CHCH2), 5.09 (dt, J ˆ 10.4, 1.4 Hz, 1H; CHCH2), 4.38 (m, 1H; H2), 3.83 (d,
J ˆ 8.8 Hz, 1H; H5), 3.50 (brs, 2H; CH2OH), 3.45 (d, J ˆ 8.8 Hz, 1H; H5),
1.80 (dd, J ˆ 12.8, 7.2 Hz, 1H; H3), 1.60 (dd, J ˆ 12.8, 8.4 Hz, 1H; H3), 1.15
(s, 1H; CH3); 13C NMR: d ˆ 139.0 (CHCH2), 116.0 (CHCH2), 80.5 (C2),
76.9 (C5), 70.1 (CH2OH), 45.6 (C4), 42.7 (C3), 21.9 (CH3). trans isomer:
1H NMR: d ˆ 5.85 (m, 1H; CHCH2), 5.21 (dt, J ˆ 17.2, 1.4 Hz, 1H;
CHCH2), 5.07 (dt, J ˆ 10.4, 1.4 Hz, 1H; CHCH2), 4.38 (m, 1H; H2), 3.71 (d,
J ˆ 8.8 Hz, 1H; H5), 3.50 (m, 3H; H5,CH2OH), 2.08 (dd, J ˆ 12.8, 7.2 Hz,
1H; H3), 1.42 (dd, J ˆ 12.8, 8.8 Hz, 1H; H3), 1.13 (s, 1H; CH3); 13C NMR:
d ˆ 139.3 (CHCH2), 115.4 (CHCH2), 80.6 (C2), 76.3 (C5), 68.9 (CH2OH),
1-(Toluene-4-sulfonyl)-2-vinyloctahydroindole (26a, b): 26a: Obtained as
a 1/1 mixture of diastereomers, colorless oil. Diastereomer 1: 1H NMR: d ˆ
7.72 (d, J ˆ 8.0 Hz, 2H; Ar), 7.29 (d, J ˆ 8.0 Hz, 2H; Ar), 5.93 (m, 1H;
CHCH2), 5.25 (dt, J ˆ 17.2, 1.2 Hz, 1H; CHCH2), 5.08 (dt, J ˆ 10.0, 1.2 Hz,
1H; CHCH2), 3.99 (q, J ˆ 8.3 Hz, 1H; H2), 3.68 (dt, J ˆ 11.2, 6.6 Hz, 1H;
H7a), 2.42 (s, 3H; ArCH3), 1.95 (m, 1H; H7), 1.82 (dd, J ˆ 10.0, 8.7 Hz, 2H;
H3), 1.70 ± 1.11 (brm, 8H; H3a, H4 ± H6, H7); 13C NMR: d ˆ 143.4, 136.3,
129.8, 127.7 (Ar), 141.0 (CHCH2), 115.0 (CHCH2), 62.7 (C7a), 61.4 (C2),
36.8 (C3a), 35.4 (C3), 31.2 (C4), 26.1 (C7), 24.5 (C5), 21.7 (ArCH3), 20.6
‡
45.9 (C4), 42.7 (C3), 22.3 (CH3). MS (EI): m/z (%): 143 (100) [M‡1] , 142
‡
‡
‡
‡
(18) [M] , 125 (19) [M OH] , 111 (30) [C7H11O] , 109 (28) [C7H9O] , 95
‡
‡
‡
(24) [C7H11] , 81 (19) [C6H9] , 67 (53) [C5H7] .
1
(C6). Diastereomer 2: H NMR: d ˆ 7.70 (d, J ˆ 8.0 Hz, 2H; Ar), 7.24 (d,
2-Phenyl-5-vinyltetrahydrofuran (21a): Colorless oil. This compound was
previously reported[22] without NMR data. cis isomer: 1H NMR: d ˆ 7.40 ±
7.25 (m, 5H), 6.01 (m, 1H; CHCH2), 5.34 (dt, J ˆ 15.6, 1.2 Hz, 1H;
CHCH2), 5.16 (dt, J ˆ 10.4, 1.2 Hz, 1H; CHCH2), 4.96 (t, J ˆ 7 Hz, 1H; H2),
4.49 (q, J ˆ 7 Hz, 1H; H5), 2.33 (m, 1H; H3), 2.16 (m, 1H; H3), 1.85 (m,
2H; H4); 13C NMR: d ˆ 143.6 (CHCH2), 139.3, 128.5, 127.4, 126.1 (Ar),
115.8 (CHCH2), 81.5 (C2), 81.1 (C5), 34.8 (C3), 32.4 (C4); trans isomer:
1H NMR: d ˆ 7.40 ± 7.25 (m, 5H), 5.95 (m, 1H; CHCH2), 5.32 (dt, J ˆ 16.8,
1.4 Hz, 1H; CHCH2), 5.14 (dt, J ˆ 10.4, 1.4 Hz, 1H; CHCH2), 5.08 (t, J ˆ
7.6 Hz, 1H; H2), 4.49 (q, J ˆ 6.4 Hz, 1H; H5), 2.40 (m, 1H; H3), 2.20 (m,
1H; H3), 1.86 (m, 2H; H4); 13C NMR: d ˆ 143.7 (CHCH2), 139.5, 128.5,
127.4, 125.8 (Ar), 115.3 (CHCH2), 81.0 (C2), 80.9 (C5), 35.6 (C3), 33.2 (C4).
J ˆ 8.0 Hz, 2H; Ar), 5.62 (m, 1H; CHCH2), 5.12 (dt, J ˆ 17.2, 0.8 Hz, 1H;
CHCH2), 4.94 (dt, J ˆ 9.6, 0.8 Hz, 1H; CHCH2), 4.25 (t, J ˆ 8.2 Hz, 1H;
H2), 3.82 (dt, J ˆ 10.8, 5.3 Hz, 1H; H7a), 2.40 (s, 3H; ArCH3), 2.29 (m, 2H;
H3), 2.21 (m, 1H; H7), 1.70 ± 1.11 (brm, 8H; H3a, H4 ± H6, H7); 13C NMR:
d ˆ 142.8, 139.6, 129.4, 127.7 (Ar), 139.5 (CHCH2), 115.7 (CHCH2), 61.4
(C7a), 61.0 (C2), 35.8 (C3a), 35.0 (C3), 29.4 (C4), 26.3 (C7), 24.0 (C5), 21.7
(ArCH3), 20.6 (C6). 26b: Formed as a 1/1 mixture of diastereomers as
colorless crystals, m.p. 90 ± 928C. Diastereomer 1: 1H NMR: d ˆ 7.70 (d, J ˆ
8.0 Hz, 2H; Ar), 7.30 (d, J ˆ 8.0 Hz, 2H; Ar), 5.86 (m, 1H; CHCH2), 5.35
(d, J ˆ 16.4 Hz, 1H; CHCH2), 5.14 (d, J ˆ 10.0 Hz, 1H; CHCH2), 4.40 (q,
J ˆ 8.0 Hz, 1H; H2), 2.78 (dt, J ˆ 10.4, 3.6 Hz, 1H; H7a), 2.54 ± 2.44 (brm,
2H; H3), 2.43 (s, 3H; ArCH3), 1.85 ± 0.95 (brm, 9H; H3a, H4 ± H7);
13C NMR: d ˆ 142.8, 140.1, 129.6, 127.6 (Ar), 140.0 (CHCH2), 115.5
(CHCH2), 65.8 (C7a), 62.2 (C2), 45.8 (C3a), 36.2 (C3), 32.9 (C4), 30.3 (C7),
25.6 (C5), 25.0 (C4), 21.8 (ArCH3). Diastereomer 2: 1H NMR: d ˆ 7.69 (d,
‡
‡
‡
MS (EI): m/z (%): 175 (5) [M‡1] , 174 (33) [M] , 157 (100) [M OH] ,
‡
‡
‡
‡
145 (58) [C10H9O] , 117 (90) [C9H9] , 104 (32) [C8H8] , 91 (15) [C7H7] , 77
‡
‡
(13) [C6H5] , 67 (42) [C5H7] .
Chem. Eur. J. 2001, 7, No. 19
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0719-4105 $ 17.50+.50/0
4105

K. Szabó and I. Macsµri
FULL PAPER
J ˆ 8.0 Hz, 2H; Ar), 7.24 (d, J ˆ 8.0 Hz, 2H; Ar), 5.65 (m, 1H; CHCH2),
5.22 (d, J ˆ 16.8 Hz, 1H; CHCH2), 5.05 (d, J ˆ 10.4 Hz, 1H; CHCH2), 4.22
(m, 1H; H2), 2.54 ± 2.44 (brm, 2H; H3), 2.40 (s, 3H; ArCH3), 2.18 (m, 1H;
H7a), 1.85 ± 0.95 (brm, 9H; H3a, H4 ± 7); 13C NMR: d ˆ 143.6, 135.1, 129.8,
128.1 (Ar), 139.7 (CHCH2), 115.7 (CHCH2), 67.2 (C7a), 63.6 (C2), 43.2
(C3a), 38.4 (C3), 31.2 (C4), 29.9 (C7), 25.7 (C5), 25.3 (C4), 21.9 (ArCH3);
[6] a) N. X. Hu, Y. Aso, T. Otsubo, F. Ogura, Tetrahedron Lett. 1988, 29,
4949; b) M. Arimoto, H. Yamaguchi, E. Fujita, M. Ochiai, Y. Nagao,
Tetrahedron Lett. 1987, 28, 6289; M. Ochiai, E. Fujita, M. Arimoto, H.
Yamaguchi, Chem. Pharm. Bull. 1985, 33, 41, 989; c) T. Fuchigami, K.
Yamamoto, Chem. Lett. 1996, 937; M. Ochiai, E. Fujita, M. Arimoto,
H. Yamaguchi, Chem. Pharm. Bull. 1984, 32, 5027; d) J. Yoshida, T.
Murata, S. Isoe, Tetrahedron Lett. 1986, 27, 3373; T. Takanami, K.
Suda, H. Ohomori, M. Masui, Chem. Lett. 1986, 1335; e) S. R. Wilson,
C. E. Augelli-Safran, Tetrahedron 1988, 44, 3983; f) A. Riahi, J. Cossy,
J. Muzart, J. P. Pete, Tetrahedron Lett. 1985, 26, 839; g) J. A.
Soderquist, K. L. Thompson, J. Organomet. Chem. 1978, 159, 237;
h) M. Ochiai, S. Tada, M. Arimoto, E. Fujita, Chem. Pharm. Bull.
1982, 30, 2836; i) M. Ochiai, E. Fujita, M. Arimoto, H. Yamaguchi,
Chem. Pharm. Bull. 1984, 32, 5027.
[7] a) J. Tsuji, Palladium Reagents and Catalysts: Innovations in Organic
Synthesis, Wiley, Chichester, 1995, chaps. 3 and 4; b) S. A. Godleski in
Comprehensive Organic Synthesis, Vol. 4 (Eds.: B. M. Trost, I. Flem-
ing), Pergamon Press, New York, 1991, chap. 3.3.
[8] P. J. Harrington in Comprehensive Organometallic Chemistry II,
Vol. 12 (Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson, R. J.
Puddephatt), Elsevier, New York, 1995, p. 797.
‡
‡
MS (CI): m/z (%): 306 (13) [M‡1] , 305 (63) [M] , 262 (100)
‡
‡
‡
[C14H16NO2S] , 241 (17), 198 (6) [C9H12NO2S] , 155 (14) [C7H7O2S] ,
‡
‡
‡
150 (21) [C10H16N] , 107 (13) [C8H11] , 91 (29) [C7H7] .
2-(Hept-1'-enyl)-4,4-dimethyl-1-(toluene-4-sulfonyl)pyrrolidine (27): Ob-
tained as a 4/1 mixture of E and Z isomers, colorless oil. 1H NMR: d ˆ 7.67
(d, J ˆ 8.0 Hz, 2H; Ar), 7.26 (d, J ˆ 8.0 Hz, 2H; Ar), 5.68 (m, 1H; H1'), 5.34
(m, 1H; H2'), 4.05 (q, J ˆ 7.9 Hz, 1H; H2), 3.22 (dd, J ˆ 9.9, 1.3 Hz, 1H;
H5), 3.15 (dd, J ˆ 9.9 Hz, 1H; H5), 2.42 (s, 3H; ArCH3), 1.96 (m, 2H; H3'),
1.74 (ddd, J ˆ 12.7, 7.4, 1.2 Hz, 1H; H3), 1.52 (dd, J ˆ 12.6, 8.5 Hz, 1H; H3),
1.29 (brm, 6H; H4' ± H6'), 1.05 (s, 3H; CH3), 0.88 (s, 3H; H7'), 0.76 (s, 3H;
CH3); 13C NMR: d ˆ 143.2, 136.7, 129.6, 127.9 (Ar), 132.6 (C1'), 131.3 (C2'),
62.3 (C5), 61.6 (C2), 48.3 (C3), 37.7 (C4), 32.3 (C3'), 31.8 (C5'), 29.0 (C4'),
26.8 (CH3), 26.4 (CH3), 22.9 (C6'), 21.8 (ArCH3), 14.4 (C7'); elemental
analysis (%) calcd for C20H31NO2S (349.54): C 68.72, H 8.94, N 4.01; found:
C 68.59, H 9.06, N 4.16.
[9] a) J.-E. Bäckvall, Metal-Catalyzed Cross Coupling Reactions, VCH,
Weinheim, 1998, p. 339; b) J.-E. Bäckvall, J.-E. Nyström, R. E.
Nordberg J. Am. Chem. Soc. 1985, 107, 3676; c) J.-E. Bäckvall, S. E.
Byström, R. E. Nordberg J. Org. Chem. 1984, 49, 4619; d) A. M.
Formation of the (h3-allyl)palladium complexes: The influence of the
chloride concentration on the formation of the (h3-allyl)palladium complex
29 was studied by mixing Pd(OAc)2 (0.011 g, 0.05 mmol) with various
amounts of Ph4PCl in CDCl3 (0.5 mL). This solution was transferred to an
NMR tube followed by addition of 28 (0.006 g, 0.05 mmol) in CDCl3
(0.2 mL). Formation of 29 was monitored by 1H NMR spectroscopy. The
solvent effect was studied by using Pd(OAc)2 (0.011 g, 0.05 mmol), Ph4PCl
(0.002 g, 0.005 mmol), and 28 (0.006 g, 0.05 mmol) dissolved in various
CD3OD/CDCl3 mixtures (0.7 mL).
Ä
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Bis(m-Chloro)bis[1-phenyl-(4,5,6-h3)-hexen-1-ol]palladium (30): Allylsi-
lane 5a (0.040 g, 0.16 mmol) in methanol (3.5 mL) was added to a stirred
solution of Li2[PdCl4] (0.045 g, 0.17 mmol) in methanol (3.5 mL) at 08C.
The progress of the reaction was monitored by TLC (pentane/diethyl ether
4/1). After completion of the reaction, the solvent was removed, and the
residual yellow oil was purified by chromatography (CH2Cl2/MeOH 14/1)
to afford 30 as yellow crystals (88% yield). Complex 30 was formed as a 1/1
mixture of diastereomers. 1H NMR: d ˆ 7.34 (m, 4H; Ar), 7.28 (m, 1H; Ar),
5.27 (m, 1H; H5), 4.75 (m, 1H; H4), 3.88 (m, 2H; H6), 2.82 (d, J ˆ 11.8,
6.8 Hz, 1H; H1), 2.30 ± 1.69 (brm, 2H; H2, H3); 13C NMR: d ˆ 144.4, 144.3,
128.7, 127.8, 126.1, 126.0 (Ar), 110.1, 110.0 (C5), 86.2, 86.1 (C4), 74.2, 73.8
(C1), 59.3 (C6), 38.2, 37.8 (C2), 28.9, 28.7 (C3); MS (CI): m/z (%): 634 (1)
Â
Â
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Â
Â
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Â
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Farkas, J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C.
Pomelli, C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson, P. Y.
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G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L.
Martin, D. J. Fox, T. A. Keith, M. A. Al-Laham, C. Y. Peng, A.
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Pittsburgh, PA, 1998.
‡
‡
‡
[M‡2] , 175 (6) [C12H15O] , 157 (26) [C12H13] , 117 (47), 107 (43)
‡
‡
‡
‡
[C7H7O] , 79 (100) [C6H7] , 77 (55) [C6H5] , 67 (40) [C5H7] .
Acknowledgements
This work was supported by the Swedish Natural Science Research Council
(NFR). The calculations were performed at the IBM SP2 parallel computer
facility of the Paralleldatorcentrum (PDC) at the Royal Institute of
Technology (KTH) in Stockholm, Sweden. We thank the PDC for a
generous allotment of computer time. The financial support of the Carl
Tryggers Foundation is also gratefully acknowledged.
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Received: March 13, 2001 [F3128]
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