Pentadienyl type lithium and potassium species: The regioselectivity of their reactions with electrophiles

Article abstract of DOI:10.1055/s-2001-17521

Seven structurally distinct pentadienyl type lithium and potassium compounds were screened against a variety of electrophiles in order to assess the regioselectivity of the trapping reactions. Organoborates and analogs thereof (fluorodimethoxyborane) proved to be perfectly regioreliable attacking only unsubstituted terminal positions and thus providing, after oxidation, exclusively primary allylic alcohols. 2,4-Pentadienyllithiums or -potassiums, that carry a methyl group at the 1- or 3-position, exhibit the same extreme regioselectivity towards halotrialkylsilanes or carbon dioxide. Although the unsubstituted parent compounds combine with such electrophiles still preferentially at the terminal position, considerable proportions of branched products are concomitantly formed as well (1/3-attack ratios ranging from 2:1 to >20:1). Hydroxyalkylating and alkylating reagents such as formaldehyde, oxirane or butyl iodide invariably afford regioisomeric mixtures generally varying in composition between 3:1 and 1:3. The condensation reaction with halotrialkylsilanes appears to follow a concerted (S_N2-like) rather than an addition/elimination (ate complex-mediated) mechanism.

Full text of DOI:10.1055/s-2001-17521

1830
PAPER
Pentadienyl Type Lithium and Potassium Species:
The Regioselectivity of their Reactions with Electrophiles
P
entadienyl Type Lithi
a
um and Po
n
c
f
ies red Schlosser,* Armin Zellner, Frédéric Leroux
Section de Chimie, Université, BCh, 1015 Lausanne, Switzerland
Fax +41(21)6923965; E-mail: manfred.schlosser@ico.unil.ch
Received 9 April 2001; revised 23 May 2001
immense practical importance, the following issues will
now be addressed specifically:
Abstract: Seven structurally distinct pentadienyl type lithium and
potassium compounds were screened against a variety of electro-
philes in order to assess the regioselectivity of the trapping reac-
tions. Organoborates and analogs thereof (fluorodimethoxyborane)
proved to be perfectly regioreliable attacking only unsubstituted ter-
minal positions and thus providing, after oxidation, exclusively pri-
mary allylic alcohols. 2,4-Pentadienyllithiums or -potassiums, that
carry a methyl group at the 1- or 3-position, exhibit the same ex-
treme regioselectivity towards halotrialkylsilanes or carbon diox-
ide. Although the unsubstituted parent compounds combine with
such electrophiles still preferentially at the terminal position, con-
siderable proportions of branched products are concomitantly
formed as well (1/3-attack ratios ranging from 2:1 to > 20:1). Hy-
droxyalkylating and alkylating reagents such as formaldehyde, ox-
irane or butyl iodide invariably afford regioisomeric mixtures
generally varying in composition between 3:1 and 1:3. The conden-
sation reaction with halotrialkylsilanes appears to follow a concert-
ed (SN2-like) rather than an addition/elimination (ate complex-
mediated) mechanism.
– How regioselectively do 2,4-pentadienylmetals and 3-
methyl-2,4-pentadienylmetals react with a wide vari-
ety of electrophiles?
– How stereoselectively can the metalation of (Z)- and
(E)-1,4-hexadiene and 2,6-dimethyl-2,5-heptadiene be
accomplished?
The stereopreferences of pentadienyl-type organometal-
lics were probed either by NMR spectroscopy2,3,6,8 or by
correlation of the stereocomposition of the reactive inter-
mediates with that of their final, isolable products.4,5,7,9,10
The latter approach relies on the availability of “well-be-
haved” electrophiles, such as silanes or boranes, which at-
tack preferentially or exclusively terminal positions of the
delocalized area. If, on the contrary, the electrophile be-
comes attached to the central carbon atom, most if not all
stereochemical information inherent in the organometallic
intermediate gets lost. Therefore, virtually all trapping
studies performed so far employed either chlorotrimethyl-
silane or fluorodimethoxyborane,11,12 both electrophiles
being reputed to exhibit the required regioselectivity.
Key words: diene metalation, superbase chemistry, organometallic
mobility, regioselectivity, stereoselectivity
The fascinating stereopreferences and stereodynamics of
pentadienyl-type organometallics have been reviewed
some years ago.1 Fundamental facts shall nevertheless be
briefly summarized. Whereas 2,4-pentadienyllithium2 in
tetrahydrofuran and 2,4-pentadienylpotassium in liquid
ammonia3 or in paraffinic suspension4 adopt the zigzag-
like outstretched “W-form”, 2,4-pentadienylpotassium
coils up to produce the horseshoe-like “U-form” when
dissolved in tetrahydrofuran.5,6 The conformational popu-
lation of pentadienyls carrying a primary alkyl chain at the
1-position again depends on the nature of the metal and
the solvent.7 In contrast, all 3-methyl-2,4-pentadienyls4,8
exist in the “W-shape” and all 2,4-dimethyl-2,4-
pentadienyl4 in the “U-shape” regardless whether com-
bined with lithium or potassium and dissolved in tetrahy-
drofuran or suspended in hexanes. The third privileged
structure, the equally coplanar and hence again optimally
resonance-stabilized “S-form” has so far been identified
only in mobility-restricted cyclic structures.9,10
As a more systematic investigation has now revealed, the
latter assumption is only partially fulfilled. Whereas all
halotrialkylsilanes investigated reacted with 2,4-penta-
dienylpotassium, if suspended in hexanes, almost exclu-
sively at the terminal positions and the 3-substituted iso-
mer was formed only in traces (£3%), the amount of the
latter increased significantly (to 11–44%) whenever tet-
rahydrofuran was used as the solvent. Carbon dioxide,
formaldehyde, oxirane and ethylene sulfate afforded re-
gioisomeric mixtures (1, 2, see Scheme 1) in all solvents
(Table 1). In contrast, fluorodimethoxyborane11,12 and 2-
methoxy-1,3,2-dioxa-borolane13,14 gave only primary de-
rivatives (Z-1 or E-1) regardless of the reaction medium
(Table 1).
A substituent at the 3-position as present in 3-methyl-1,4-
pentadienylmetals tends to hinder the approach of an elec-
trophile. After deprotonation of the hydrocarbon precur-
sor with butyllithium in the presence of potassium tert-
butoxide (“LIC-KOR”) in tetrahydrofuran and subsequent
interception with silanes or boranes, only the end-on prod-
ucts 3 were found (Scheme 2, Table 2). When oxirane or
1-iodobutane served as the trapping reagents, both the
chain-lengthened and the doubly branched regioisomers,
The principal features of the scenario thus being known,
numerous details remain to be elucidated. In view of their
Synthesis 2001, No. 12, 25 09 2001. Article Identifier:
1437-210X,E;2001,0,12,1830,1836,ftx,en;T02301SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
Pentadienyl Type Lithium and Potassium Species
1831
3 and 4, were obtained (Table 2). The configuration of the
end-on products 3 was invariably E.
M
M
"U"
"W"
K
El
El
El
El
El
4
"W"
E-3
Z-1
E-1
2
b : El = Si(C2H5)3; d : El = OH;
a : El = Si(CH3)3;
e : El = B(OR)2;
b : El = Si(C2H5)3; c : El = Si(iC3H7)3;d : El = OH;
f : El = COOH; g : El = CH2OH; h : El = CH2CH2OH.
a : El = Si(CH3)3;
e : El = B(OR)2;
f : El = COOH; h : El = CH2CH2OH; i : El = C4H9.
Scheme 2
Scheme 1
Table 2 Reaction of 3-Methyl-2,4-pentadienylpotassium in THF
with a Series of Electrophiles: Yields of Trapping Products, g/a-Ra-
tios of Regioisomers 4 vs. 3 and Z/E-Composition of Isomers 3
Table 1 Reaction of 2,4-Pentadienylpotassium in Petroleum Ether
and in THF with a Variety of Electrophiles El-X: Yields of Trapping
Products, g/a-Ratios of Regioisomers 2 vs. 1 and Z/E-Composition of
Isomers 1
Compd
El-X
Yield
(%)
g/a
(Z/E)-3
Cpd El-X
In PETa
In THFb
a
b
d
c
f
ClSi(CH3)3
ClSi(C2H5)3
86
83
52
63
73
73
67
<1:99
<1:99
<1:99
<1:99
<1:99
64:36
54:46
>97:3
>97:3
>97:3
>97:3
>97:3
>97:3
>97:3
Yield g/a
Z/E
Yield g/a
Z/E
Ratio Ratio
(%)
Ratio Ratio (%)
a
a
a
a
b
c
ISi(CH3)3
95
3:97
3:97
3:97
2:98
2:98
2:98
95
96
98
95
95
46:54 98:2
41:59 98:2
24:76 98:2c
16:84 94:6
15:85 98:2
<1:99 80:20
<1:99 93:7
<1:99 95:5
38:62 98:2
50:50 97:3
91:9 98:2k
a
FB(OCH3)2
BrSi(CH3)3
ClSi(CH3)3
FSi(CH3)3
95
b
H3COB(OR)2
95
c
CO2
88
<1:99 5:95
4:96 2:98
c,d
h
i
O(CH2)2
ClSi(C2H5)3 85
ClSi(iC3H7)3 33
IC4H9
<1:99 11:89 97
a After treatment of the initially formed boronate with alkaline hydro-
gen peroxide the allyl alcohol was isolated.
b B(OR)2 = 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolyl).
c Followed by neutralization at 0 °C.
d
d
e
FB(OCH3)2 43
<1:99 2:98
<1:99 9:91
12:88 4:96
54
54
71
54
65
H3COB(OR)2e 67
d O(CH2)2 = oxirane.
f
f
CO2
49
-
f,g,h,i
g
h
OCH2
-
-
The 1,4-pentadiene derived products 1 were trans-iso-
mers when prepared in petroleum ether and cis-isomers
when prepared in tetrahydrofuran (Table 1). The 3-meth-
yl-1,4-pentadiene derived products 3 had invariably the E-
configuration (Table 2). We wanted to include in the
present study also “5-methyl-2,4-pentadienylmetals”
(2,4-hexadienylmetals) which we expected to show, qual-
itatively at least, the same stereochemical dynamics and
preferences as already reported for 2,4-decadienylmetals.7
This was indeed found to be the case. For well intelligible
reasons,7,18 the internal double bond retained the configu-
ration inherited from its hydrocarbon precursor and the or-
ganometallic intermediate generated upon deprotonation
with sec-butyllithium adopted the “W-form”. However,
after the interception with standard electrophiles, some
2Z,4Z-isomer (2Z,4Z-5) was inevitably isolated along
with the 2E,4Z-isomer (2E,4Z-5) in an approximate ratio
of 1:12 (Table 3). Since admixtures of the sterically unre-
f,i,j
O(CH2)2
64
52:48 9:91
a PET = petroleum ether (in general, hexanes).
b THF = tetrahydrofuran.
c When the metalation was carried out with sec-butyllithium at –75 °C
in the absence of potassium tert-butoxide, 93% of products were
formed in a g/a-ratio of 12:88 and a Z/E-ratio of 5:95.
d After the immediately ensuing treatment with alkaline hydrogen
peroxide the allyl alcohol was isolated.
e B(OR)2 = 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolyl).
f Followed by neutralization at 0 °C.
g Formaldehyde as a 0.8 M solution in THF.15,16,
h When the metalation was carried out with sec-butyllithium at
–75 °C in the absence of potassium tert-butoxide, 42% of products
were formed in a g/a-ratio of 69:31 and a Z/E-ratio of 5:95.
i The branched g-product underwent partial isomerization to its con-
jugated isomer (see Ref.17).
j O(CH2)2 = oxirane.
k Ethylene sulfate (1,3,2-dioxathiolane 2,2-dioxide) instead of ox-
irane.
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York

1832
M. Schlosser et al.
PAPER
alistic “U-form” can be ruled out, there must have oc- The metalation of 5-methyl-1,4-hexadiene with sec-butyl-
curred some leakage to the “S-form”. The coexistence of lithium or superbasic mixed metal reagent followed by
“S-forms” offers also the most plausible explanation of treatment with chlorotrimethylsilane invariably produced
why trans-1,4-hexadiene after metalation with “LIC- stereomixtures suggesting the coexistence of a “W-con-
KOR” did not provide the pure 2(Z,4E)-isomer (2Z,4E-5, former” and an “S-conformer”.19 On the contrary, a neat
via the U-shaped intermediate) nor after metalation with “W-structure” can be attributed to the organometallic spe-
sec-butyllithium, again in tetrahydrofuran, the pure cies generated by metalation of 2,6-dimethyl-2,5-heptadi-
2E,4E-isomer (2E,4E-5, via the W-shaped intermediate) ene with “LIC-KOR” in tetrahydrofuran. Although its
but mutually stereocontaminated materials in approxi- condensation with chlorotrimethylsilane mainly takes
mate ratios of 7:1 and 12:1, respectively (Scheme 3, place at the 4-position (51% of isomer 6) and only to a
Table 3).
small extent (6%) at the 2-position, the exclusive trans-
configuration of the latter isomer 7 has been unequivocal-
ly established (Scheme 4).
M = Li;
THF
M = K;
THF
M = Li;
THF
LIC-KOR
M
M
M
M
"exo-U"
"endo-W"
"exo-W"
El
El
H
El-X
El-X
"W"
6
E-7
El
El
El
Scheme 4
2Z,4E-5
2E,4E-5
2E,4Z-5
To our knowledge, fluorotrimethylsilane (see Table 1)
has never been used before as a trapping agent for polar
organometallic species. It proved to be far less reactive
than the heavier halotrimethylsilanes. For example, when
chlorotrimethylsilane was added to a solution of 2,4-pen-
tadienylpotassium in tetrahydrofuran kept at –75 °C, the
characteristic red color disappeared in the course of a few
seconds while a steep temperature rise indicated an exo-
thermal process. In contrast, fluorotrimethylsilane was
found to be inert at –75 °C and to react only slowly at –50
°C. Judging on this basis, the relative chloride/fluoride
rates kCl/kF must be situated between 10 and 100, thus fall-
ing in the same range which is typical for bimolecular nu-
cleophilic substitutions (SN2).20,21 In contrast, one would
expect to encounter reversed ratios if a nucleophilic addi-
tion/nucleofugal elimination mechanism featuring an ate
complex22,23 intermediate were operative. 4-Fluoro-
nitrobenzene undergoes irreversible nucleophilic aromat-
ic substitutions up to 400 times faster than the chloro ana-
log does.24–26
a : El = Si(CH3)3;
d : El = OH; e : El = B(OR)2; f : El =COOH.
Scheme 3
Table 3 Consecutive Reaction of cis- or trans-1,4-Hexadiene with
Various Metalating Reagents (“rg.”) and Various Electrophiles (El-
X): Yields and 2Z,4Z/2E,4Z- or 2Z,4E/2E,4E-Product Ratios Depend-
ing on Whether the cis-Diene or the trans-Diene Served as the Precur-
sor
Cpd El-X
cis-Diene
trans-Diene
rg.: LISa
rg.: LIC-KORb rg.: LISa
Yield Product Yield Product Yield Product
(%) Ratio (%) Ratio (%) Ratio
a
d
e
f
ClSi(CH3) 3
59
41
10:90 72
91:9
92:8
96:4
92:8
57
45
65
17
12:88
12:88
18:82
16:84
c
FB(OCH3)2
9:91
8:92
6:94
53
63
16
d
H3COB(OR)2 60
e
CO2
18
For laboratory routine and abbreviations, see previous publications
emanating from this laboratory (e.g., Ref.27). 1H NMR spectra were
recorded of solutions in CDCl3 at 400 MHz.
a LIS = sec-butyllithium.
b LIC-KOR = “superbasic” 1:1 mixture of butyllithium (“LIC”) and p
tassium tert-butoxide (“KOR”).
Starting Materials and Reagents: 1,4-Pentadiene, 3-methyl-1,4-
pentadiene and cis-1,4-hexadiene are commercial. trans-1,4-Hexa-
diene28 and 2,7-dimethyl-2,6-heptadiene29 were prepared according
to literature procedures. The same holds for the reagents
fluorodimethoxyborane11,12 and 2-methoxy-4,4,5,5-tetramethyl-
1,3,2-dioxaborolane and the solution of formaldehyde in tetrahy-
drofuran.15,16
c After the immediately ensuing treatment with alkaline hydrogen per
ide the allyl alcohol was isolated.
d B(OR)2 = 2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolyl).
e After neutralization at 0 °C, the carboxylic acid was obtained.
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Pentadienyl Type Lithium and Potassium Species
1833
Metalation and Trapping Reactions; General Procedures
a) At 0 °C, BuLi (25 mmol) in hexanes (15 mL) and the diene (25
mmol) were added to a suspension of potassium tert-butoxide (2.8
g, 25 mmol) in hexanes (25 mL). After 20 min of vigorous stirring
at 0 °C, the electrophile (25 mmol) was added to the mixture at
–75 °C or the latter was poured onto an excess of freshly crushed
dry ice. If the reagent was a trialkylhalosilane or 2-methoxy-4,4,5,5-
tetramethyl-1,3,2-dioxaborolane, the precipitate formed was re-
moved by filtration or centrifugation and the product isolated by
distillation. The alcoholates and carboxylates obtained in reactions
with formaldehyde, oxirane or carbon dioxide were neutralized with
a slight excess of HCl in Et2O24 before the workup continued as de-
scribed above. The dimethyl boronates resulting from the treatment
with fluorodimethoxyborane were oxidized with 35% aq H2O2 in al-
kaline medium11 to afford allylic alcohols, which were extracted
with Et2O and distilled. The composition of crude reaction mixtures
was always checked by gas chromatography using calibrated refer-
ence compounds (“internal standards”) for the assessment of yields.
To make acids more volatile, they had beforehand been converted
into their methyl esters by exhaustive treatment with ethereal diazo-
methane.
Triethyl-(1-vinyl-2-propenyl)silane (2b)
Separated from the isomers Z-1b or E-1b by preparative gas chro-
matography (2 m, 10% SE-30, 125 °C); bp 88–89 °C/12 mmHg;
nD20 1.4718.
1H NMR: d = 5.92 (2 H, ddd, J = 17.2, 9.6, 8.5 Hz), 4.9 (4 H, m),
2.66 (1 H, t, J = 8.3 Hz), 0.97 (9 H, t, J = 7.7 Hz), 0.59 (6 H, q, J =
7.7 Hz).
MS: m/z = 183 (84, M+ + H), 132 (81), 115 (85), 104 (34), 87 (100).
Anal. Calcd for C11H22Si (182.4): C, 72.44; H, 12.16. Found: C,
72.54; H, 12.03.
(Z)-Triisopropyl-2,4-pentadienylsilane (Z-1c)
Colorless liquid; bp 119–120 °C/12 mmHg; nD20 1.4641.
1H NMR: d = 6.71 (1 H, ddd, J = 16.7, 11.3, 10.2 Hz), 5.92 (1 H, t,
J = 10.9 Hz), 5.60 (1 H, qm, J = 9.5 Hz), 5.14 (1 H, d, J = 17.1 Hz),
5.05 (1 H, dm, J = 10.1 Hz), 1.76 (2 H, d, J = 8.4 Hz), 1.05 (18 H,
d, J = 2.6 Hz).
MS: m/z (%) = 225 (100, M+ + H), 174 (92), 157 (23), 87 (33), 76
(31), 73 (66).
Anal. Calcd for C14H28Si (224.5): C, 74.91; H, 12.57. Found: C,
74.91; H, 12.15.
b) If the reaction between the dienyl type organopotassium com-
pound and the electrophilic reagent was to be performed in homo-
geneous solution, the metalation was carried out as described in the
preceding paragraph. Then the hexanes were stripped off under re-
duced presure. At 75 °C, precooled THF (125 mL) was added, fol-
lowed 20 min later, still at –75 °C, by the electrophile.
(E)-Triisopropyl-2,4-pentadienylsilane (E-1c)
Colorless liquid; bp 119–120 °C/12 mmHg; nD20 1.4648.
1H NMR: d = 6.30 (1 H, dt, J = 16.7, 10.1 Hz), 6.00 (1 H, dd, J =
15.1, 10.4 Hz), 5.00 (1 H, dm, J = 17.0 Hz), 4.85 (1 H, dm, J = 10.1
Hz), 1.67 (2 H, d, J = 7.9 Hz), 1.05 (18 H, d, J = 2.6 Hz).
MS: m/z (%) = 225 (100, M+ + H), 174 (72), 87 (21), 76 (31), 73
(52).
c) If the organolithium derivative was to be generated in THF, the
hydrocarbon (25 mmol) was dissolved in this solvent (125 mL) and
was treated with sec-BuLi (25 mmol) for 1 h at –50 °C. The electro-
phile (25 mmol) was added at –75 °C.
Anal. Calcd for C14H28Si (224.5): C, 74.91; H, 12.57. Found: C,
74.66; H, 12.31.
Products Derived from 1,4-Pentadiene
(Z)- and (E)-Trimethyl-2,4-pentadienylsilane (Z- and E-1a),30 tri-
methyl-(1-vinyl-2-propenyl)silane (2a),31 (Z)32- and (E)33-2,4-pen-
tadien-1-ol (Z- and E-1e), (Z)34- and (E)35-3,5-hexadien-1-ol (Z- and
E-1g), 2-vinyl-3-buten-1-ol (2g),36 (Z)37- and (E)38-4,6-heptadien-1-
ol (Z- and E-1h), 3-vinyl-4-penten-1-ol37,39 and methyl (E)-3,5-
hexadienoate40 (2h) have been reported previously.
(Z)-4,4,5,5-Tetramethyl-2-(2,4-pentadienyl)-1,3,2-dioxa-
borolane (Z-1d)
Colorless liquid; bp 102–104 °C/35 mmHg; nD20 1.4582.
1H NMR: d = 6.64 (1 H, dt, J = 16.4, 10.3 Hz), 6.02 (1 H, t, J = 10.4
Hz), 5.58 (1 H, q, J = 8.7 Hz), 5.16 (1 H, d, J = 16.1 Hz), 5.07 (1 H,
d, J = 9.8 Hz), 1.84 (2 H, d, J = 7.0 Hz), 1.26 (12 H, s).
(Z)-Triethyl-2,4-pentadienylsilane (Z-1b)
Purified by preparative gas chromatography (2 m, 10% SE-30,
MS: m/z (%) = 194 (81, M+), 179 (23), 136 (20), 95 (100), 83 (56).
125 °C); bp 90–91 °C/12 mmHg; nD20 1.4786.
Anal. Calcd for C11H19BO2 (194.1): C, 68.08; H, 9.87. Found C,
67.79; H, 9.59.
1H NMR: d = 6.63 (1 H, ddd, J = 16.9, 11.0, 10.4 Hz), 5.93 (1 H, t,
J = 10.8 Hz), 5.52 (1 H, q, J = 9.4 Hz), 5.13 (1 H, d, J = 16.5 Hz),
5.03 (1 H, d, J = 9.7 Hz), 1.69 (2 H, d, J = 8.9 Hz), 0.96 (9 H, s),
0.55 (6 H, q, J = 7.7 Hz).
MS: m/z = 183 (100, M+ + 1), 182, (9, M+), 132 (64), 115 (73), 104
(32), 87 (97).
(E)-4,4,5,5-Tetramethyl-2-(2,4-pentadienyl)-1,3,2-dioxa-
borolane (E-1d)
Colorless liquid; bp 102–104 °C/32 mmHg; nD20 1.4577.
1H NMR: d = 6.30 (1 H, dt, J = 16.9, 10.5 Hz), 6.04 (1 H, dd, J =
15.0, 10.2 Hz), 5.75 (1 H, dt, J = 14.9, 7.3 Hz), 5.02 (1 H, d, J = 16.9
Hz), 4.90 (1 H, d, J = 10.0 Hz), 1.75 (2 H, d, J 7.5 Hz), 1.24 (12 H,
s).
Anal. Calcd for C11H22Si (182.4): C, 72.44; H, 12.16. Found: C,
72.39; H, 12.10.
(E)-Triethyl-2,4-pentadienylsilane (E-1b)
MS: m/z (%) = 194 (100, M+), 179 (11), 136 (34), 84 (45).
Purified by preparative gas chromatography (2 m, 10% SE-30,
125 °C); bp 90–91 °C/12 mmHg; nD20 1.4792.
Anal. Calcd for C11H19BO2 (194.1): C, 68.08; H, 9.87. Found: C,
67.74; H, 9.82.
1H NMR: d = 6.29 (1 H, dt, J = 17.1, 10.2 Hz), 5.94 (1 H, dd, J =
15.1, 10.2 Hz), 5.72 (1 H, dt, J = 15.1, 8.3 Hz), 4.98 (1 H, d, J = 17.1
Hz), 4.84 (1 H, d, J = 10.2 Hz), 1.57 (2 H, d, J = 8.3 Hz), 0.93 (9 H,
t, J = 8.0 Hz), 0.53 (6 H, q, J = 8.0 Hz).
Methyl (Z)-3,5-Hexadienoate (Z-1f)
After alkaline extraction of the corresponding acid, neutralization,
re-extraction into Et2O, treatment with ethereal diazomethane and
purification by preparative gas chromatography (2 m, 10% C-20M,
125 °C); bp 50–52 °C/12 mmHg; nD20 1.4314.
Anal. Calcd for C11H22Si (182.4): C, 72.44; H, 12.16. Found C,
72.02; H, 11.90.
1H NMR: d = 5.95 (2 H, ddd, J = 16.9, 10.3, 7.4 Hz), 5.20 (2 H, d,
J = 10.2 Hz), 5.18 (2 H, d, J = 17.1 Hz), 3.76 (1 H, t, J = 7.5 Hz),
3.72 (3 H, s).
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York

1834
M. Schlosser et al.
PAPER
MS: m/z (%) = 126 (36, M+), 111 (12), 95 (19), 84 (100).
(E)-5-Methyl-4,6-heptadien-1-ol (E-3h)
Separated by preparative gas chromatography (2 m, 10% C-20M,
150 °C) from a 2:1 mixture, which contained the regioisomer 4h42
as the major component; colorless liquid; bp 108–110 °C/5 mmHg;
nD20 1.4429.
1H NMR: d = 6.38 (1 H, dd, J = 17.0, 10.3 Hz), 5.51 (1 H, t, J = 7.0
Hz), 5.11 (1 H, d, J = 17.0 Hz), 4.94 (1 H, d, J = 10.3 Hz), 3.67 (2
H, d, J = 6.2 Hz), 2.24 (2 H, q, J = 7.0 Hz), 1.76 (3 H, s), 1.68 (2 H,
pent, J = 6.2 Hz), 1.38 (1 H, s).
Anal. Calcd for C7H10O2 (126.2): C, 66.65; H, 7.99. Found: C,
66.91; H, 8.01.
Methyl 2-Vinyl-3-butenoate (2f)
Workup and gas chromatographic isolation as described in the pre-
20
ceding paragraph; colorless liquid; bp 54–55 °C/12 mmHg; nD
1.4911.
1H NMR: d = 6.56 (1 H, ddd, J = 16.6, 11.2, 10.3 Hz), 6.17 (1 H, t,
J = 7.0 Hz), 5.62 (1 H, dt, J = 10.7, 7.1 Hz), 5.28 (1 H, d, J = 16.6
Hz), 5.20 (1 H, d, J = 9.6 Hz), 3.70 (3 H, s), 3.24 (2 H, d, J = 7.5 Hz).
MS: m/z (%) = 126 (15, M+), 109 (12), 93 (100), 79 (53).
Anal. Calcd for C8H14O (126.2): C, 76.14; H, 11.18. Found: C,
76.36; H, 10.99.
MS: m/z (%) = 144 (74, M+ + NH4), 126 (33, M+), 85 (100).
Anal. Calcd for C7H10O2 (126.2): C, 66.65; H, 7.99. Found: C,
67.00; H, 7.84.
3-Methyl-3-vinyl-1-heptene (4i)
Separated by preparative gas chromatography (2 m, 5% C-20M,
125 °C) from a 1:1 mixture containing also the regioisomer E-3i;43
colorless liquid; bp 143–145 °C/12 mmHg; nD20 1.4476.
1H NMR: d = 5.81 (2 H, dd, J = 17.0, 10.0 Hz), 4.99 (2 H, d, J = 10.0
Hz), 4.97 (2 H, d, J = 17.0 Hz), 1.3 (6 H, m), 1.09 (3 H, s), 0.90 (3
H, t, J = 7.1 Hz).
Products Derived from 3-Methyl-1,4-pentadiene
(E
)-3-Methyl-2,4-pentadien-1-ol,41 3-methyl-3-vinyl-4-penten-1-
ol42 and (E)-3-methyl-1,3-nonadiene43 have been reported previous-
ly. Therefore, these compounds were only characterized by their
physical constants (bp, nD20), their 1H and 13C nuclear magnetic res-
onances and mass spectra.44
Anal. Calcd for C10H18 (138.3): C, 86.88; H, 13.12. Found: C,
86.92; H, 12.81.
(E)-Trimethyl-(3-methyl-2,4-pentadienyl)silane (E-3a)
1
Configurational assignment on the basis of H,1H-NOESY; color-
5-Methyl-5-vinyl-6-hepten-1-ol
less liquid; bp 59–60 °C/8 mmHg; nD20 1.4706.
By product formed in 12% yield upon trapping of the 3-methyl-2,4-
pentadienylpotassium intermediate with fluorodimethoxyboron
along with (E)-3-methyl-2,4-pentadien-1-ol41 (52%); separation by
preparative gas chromatography (2 m, 10% C-20M, 150 °C); color-
less liquid; bp 88–90 °C/0.5 mmHg; nD20 1.4820.
1H NMR: d = 5.80 (2 H, dd, J = 17.5, 10.9 Hz), 5.00 (2 H, d, J = 11.4
Hz), 4.97 (2 H, d, J = 18.0 Hz), 3.64 (2 H, t, J = 6.6 Hz), 1.55 (2 H,
pent, J = 7.0 Hz), 1.4 (4 H, m), 1.10 (3 H, s).
1H NMR: d = 6.40 (1 H, dd, J = 17.2, 10.7 Hz), 5.58 (1 H, t, J = 9.0
Hz), 4.99 (1 H, d, J = 17.2 Hz), 4.84 (1 H, d, J = 10.7 Hz), 1.69 (3
H, s), 1.60 (2 H, d, J = 9.0 Hz), 0.01 (9 H, s).
Anal. Calcd for C9H18Si (154.3): C, 70.04; H, 11.76. Found: C,
70.48; H, 11.76.
(E)-Triethyl-(3-methyl-2,4-pentadienyl)silane (E-3b)
Colorless liquid; bp 108–110 °C/8 mmHg; nD20 1.4826.
1H NMR: d = 6.38 (1 H, dd, J = 17.4, 10.7 Hz), 5.58 (1 H, t, J = 8.9
Hz), 4.98 (1 H, d, J = 17.4 Hz), 4.84 (1 H, d, J = 10.7 Hz), 1.72 (3
H, s), 1.63 (2 H, d, J = 8.9 Hz), 0.95 (9 H, t, J = 7.9 Hz), 0.54 (6 H,
q, J = 7.9 Hz).
MS: m/z (%) = 121 (3), 107 (9), 95 (20), 82 (199).
Anal. Calcd for C10H18O (154.3): C, 77.87; H, 11.76. Found: C,
77.87; H, 11.64.
Products Derived from cis-1,4-Hexadiene
Anal. Calcd for C12H24Si (196.4): C, 73.38; H, 12.32. Found: C,
72.80; H, 12.02.
(2E,4Z E,4Z-5a) and
)-(2,4-Hexadienyl)trimethylsilane31,45 (2
(2E,4Z)-2,4-hexadien-1-ol46 (2E,4Z-5b) are known compounds.
They were identified on basis of their physical constants (bp, nD20),
1H NMR and mass spectra.44
(E)-4,4,5,5-Tetramethyl-2-(3-methyl-2,4-pentadienyl)-1,3,2-
dioxaborolane (E-3e)
Colorless liquid; bp 100–102 °C/13 mmHg; nD20 1.4648.
(2E,4Z)-2-(2,4-Hexadienyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2E,4Z-5e)
1H NMR: d = 6.38 (1 H, dd, J = 17.0, 10.4 Hz), 5.62 (1 H, t, J = 7.8
Hz), 5.02 (1 H, d, J = 17.0 Hz), 4.86 (1 H, d, J = 10.4 Hz), 1.76 (2
H, d, J = 7.8 Hz), 1.70 (3 H, s), 1.22 (12 H, s).
MS: m/z (%) = 209 (89, M+ + H), 208 (61, M+), 151 (22), 108 (95),
85 (100).
Colorless liquid; isolated by distillation; (2E,4Z/2E,4Z) ratio 8:92;
bp 98–100 °C/12 mmHg; nD20 1.4672; 3.1 g (60%).
1H NMR: d = 6.32 (1 H, dd, J = 14.7, 10.7 Hz), 5.98 (1 H, t, J = 10.6
Hz), 5.71 (1 H, dt, J = 14.7, 7.3 Hz), 5.32 (1 H, dq, J = 10.6, 7.0 Hz),
1.78 (2 H, d, J = 7.3 Hz), 1.72 (3 H, d, J = 7.0 Hz), 1.25 (12 H, s).
Anal. Calcd for C12H21BO2 (208.1): C, 68.08; H, 9.87. Found: C,
67.82; H, 9.87.
MS: m/z (%) = 208 (100, M+), 109 (56), 81 (68).
Anal. Calcd for C12H21BO2 (208.1): C, 68.08; H, 9.87. Found: C,
67.97; H, 10.01.
(E)-4-Methyl-3,5-hexadienoic Acid (E-3f)
Configurational assignment on the basis of 1H, 1H-NOESY; mono-
clinal colorless crystals; mp 32–33 °C; bp 108–110 °C/0.2 mmHg.
Methyl (3E,5Z)-3,5-Heptadienoate (3E,5Z-5f’)
After treatment of the extracted and neutralized carboxylic acids
with diazomethane; main component (18%) in a 45:40:15 mixture
containing two further regioisomers (see below); separation of the
colorless liquid by preparative gas chromatography (2 m, 10% C-
20M, 125 °C); (3Z,5Z/3Z,5E) ratio 6:94; bp 78–80 °C/12 mmHg;
nD20 1.4722.
1H NMR: d = 6.45 (1 H, dd, J = 15.2, 10.9 Hz), 6.01 (1 H, t, J = 10.9
Hz), 5.73 (1 H, dt, J = 15.2, 7.2 Hz), 5.49 (1 H, dq, 10.9, 7.2 Hz),
3.70 (3 H, s), 3.16 (2 H, d, J = 7.2 Hz), 1.75 (3 H, d, J = 7.2 Hz).
1H NMR: d = 6.43 (1 H, dd, J = 17.5, 10.6 Hz), 5.66 (1 H, t, J = 7.2
Hz), 5.20 (1 H, d, J = 17.5 Hz), 5.05 (1 H, d, J = 10.6 Hz), 3.26 (2
H, d, J = 7.2 Hz), 1.78 (3 H, s).
MS: m/z (%) = 126 (36, M+), 111 (12), 84 (100).
Anal. Calcd for C7H10O2 (126.2): C, 66.65; H, 7.99. Found: C,
66.61; H, 7.87.
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Pentadienyl Type Lithium and Potassium Species
1835
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.74; H, 8.86.
Products Derived From trans-2,4-Hexadiene: Metalation with
sec-Butyllithium;
(2E,4E)-2-(2,4-Hexadienyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2E,4E-5c)
Methyl (E)-2-Methyl-3,5-hexadienoate
Workup and gas chromatographic separation as described in the
preceding paragraph; 16%; colorless liquid; bp 71–72 °C/12 mm-
Hg; nD20 1.4735.
1H NMR: d = 6.32 (1 H, dt, J = 16.9, 10.1 Hz), 6.13 (1 H, dd, J =
15.1, 10.7 Hz), 5.77 (1 H, dd, J = 15.1, 8.0 Hz), 5.19 (1 H, d, J =
16.9 Hz), 5.08 (1 H, d, J = 10.1 Hz), 3.69 (3 H, s), 3.20 (1 H, quint,
J = 7.0 Hz), 1.29 (3 H, d, J = 7.0 Hz).
Isolated by distillation; (2Z,4E/2E,4E) ratio 18:82; bp 104–105 °C/
12 mmHg; nD20 1.4611; 3.4 g (65%).
1H NMR: d = 6.07 (1 H, dd, J = 14.1, 10.3 Hz), 5.99 (1 H, dd, J =
14.2, 10.3 Hz), 5.57 (2 H, dt, J = 14.2, 8.1 Hz), 5.49 (1 H, dt, J =
14.1, 6.6 Hz), 1.73 (2 H, d, J = 8.1 Hz), 1.71 (3 H, d, J = 6.6 Hz),
1.24 (12 H, s).
MS: m/z (%) = 209 (31, M+ + H), 208 (100), 109 (77), 84 (88), 81
(79).
MS: m/z = 158 (68, M+ + NH4), 140 (22, M+), 81 (100), 79 (18).
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.78; H, 8.45.
Anal. Calcd for C12H21BO2 (208.1): C, 68.08; H, 9.87. Found: C,
67.92; H, 9.76.
Methyl (Z)-2-Vinyl-3-pentenoate
Methyl (3E,5E)-3,5-Heptadienoate (2E,4E-5e)
Workup and gas chromatographic separation as described above
(see 3E,5Z-5d); 6%; colorless liquid; bp 72–74 °C/12 mmHg; nD
1.4749.
1H NMR: d = 5.94 (1 H, ddd, J = 17.0, 10.0, 6.9 Hz), 5.70 (1 H, dq,
J = 10.6, 6.6 Hz), 5.55 (1 H, dd, J = 10.6, 9.1 Hz), 5.17 (1 H, d, J =
16.9 Hz), 5.15 (1 H, d, J = 10.2 Hz), 4.07 (1 H, dd, J = 9.1, 6.9 Hz),
3.71 (3 H, s), 1.68 (3 H, d, J = 6.0 Hz).
Obtained as the main component (17%) of a 56:30:14 regioisomeric
mixture along with methyl (E)-2-vinyl-3-pentenoate (see above;
9.3%) and methyl (E)-2-methyl-3,5-hexadienoate (see above;
4.3%), separated by preparative gas chromatography (2 m, 5% C-
20M, 125 °C); (3Z,5E/3E,5E) ratio 16:84; bp 75–76 °C/12 mmHg;
nD20 1.4750.
1H NMR: d = 6.10 (1 H, dd, J = 14.1, 10.2 Hz), 6.03 (1 H, dd, J =
14.2, 10.2 Hz), 5.66 (1 H, dq, J = 14.2, 7.1 Hz), 5.61 (1 H, dt, 14.1,
7.4 Hz), 3.69 (3 H, s), 3.10 (2 H, d, J = 7.4 Hz), 1.75 (3 H, d, J = 7.1
Hz).
20
MS: m/z (%) = 158 (43, M+ + NH4), 140 (12, M+), 81 (100), 79 (19).
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.79; H, 8.34.
MS: m/z (%) = 158 (74, M+ + NH4), 141 (52), 140 (36), 81 (100), 80
(33).
Products Derived from trans-1,4-Hexadiene: Metalation with
Butyllithium and Potassium tert-Butoxide;
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.75; H, 8.82.
(2Z,4E)-2-(2,4-Hexadienyl)-4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (2Z,4E-5e)
Isolated by distillation; (2Z,4E/2E,4E) ratio 96:4; colorless liquid;
Products Derived From 2,6-Dimethyl-2,5-heptadiene
Trimethyl[3-methyl-1-(2-methyl-1-propenyl)-2-butenyl]silane
(6)
bp 100–101 °C/12 mmHg; nD20 1.4709.
1H NMR: d = 6.32 (1 H, dd, J = 14.6, 10.8 Hz), 5.96 (1 H, t, J = 10.8
Hz), 5.66 (1 H, dq, J = 14.6, 6.7 Hz), 5.42 (1 H, dt, J = 10.8, 7.8 Hz),
1.82 (2 H, d, J = 7.8 Hz), 1.78 (3 H, d, J = 6.7 Hz), 1.26 (12 H, s).
Major component (51%) of a 89:11 regioisomeric mixture (for the
minor part, see below), separation by preparative gas chromatogra-
20
phy (2 m, 5% SE-30, 125 °C); bp 104–106 °C/20 mmHg; nD
MS: m/z (%) = 209 (27, M+ + H), 208 (100), 109 (68), 81 (44).
1.4599.
1H NMR: d = 5.06 (2 H, d, J = 10.6 Hz), 2.78 (1 H, t, J = 10.6 Hz),
1.72 (6 H, s), 1.61 (6 H, s), –0.04 (9 H, s).
Anal. Calcd for C12H21BO2 (208.1): C, 68.08; H, 9.87. Found: C,
68.23; H, 9.58.
MS: m/z (%) = 196 (3, M+), 122 (38), 107 (48), 73 (100).
Methyl (3Z,5E)-3,5-Heptadienoate (3Z,5E-5f’)
After carboxylation of the organometallic intermediate, by extrac-
tion and treatment of the resulting 3:2 mixture of acids with diazo-
methane; main component (minor component: see directly below)
24%; separation by preparative gas chromatography (2 m, 5% C-
20M, 125 °C), (3Z,5E/3E,5E) ratio 92:8; bp 75–77 °C/12 mmHg;
nD20 1.4776.
Anal. Calcd for C12H24Si (196.4): C, 73.38; H, 12.32. Found: C,
73.29; H, 12.24.
(E)-Trimethyl-(1,1,5-trimethyl-2,4-hexadienyl)silane (E-7)
Minor component (6%) as mentioned in the preceding paragraph:
(Z/E) < 2:98; bp 114–115 °C/12 mmHg; nD20 1.4438.
1H NMR: d = 6.26 (1 H, dd, J = 14.8, 10.8 Hz), 6.11 (1 H, t, J = 10.8
Hz), 5.77 (1 H, dq, 14.8, 6.9 Hz), 5.44 (1 H, dt, J = 10.8, 7.4 Hz),
3.70 (3 H, s), 3.22 (2 H, d, J = 7.4 Hz), 1.79 (3 H, d, J = 6.9 Hz).
1H NMR: d = 5.98 (1 H, dd, J = 15.4, 10.6 Hz), 5.82 (1 H, d, J = 10.6
Hz), 5.62 (1 H, d, J = 15.4 Hz), 1.76 (3 H, s), 1.75 (3 H, s), 1.03 (6
H, s), –0.03 (9 H, s).
MS: m/z (%) = 158 (100, M+ + NH4), 141 (74), 81 (85), 79 (21).
Anal. Calcd for C12H24Si (196.4): C, 73.38; H, 12.32. Found: C,
73.26; H, 12.25.
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.57; H, 8.32.
Acknowledgement
Methyl (E)-2-Vinyl-3-pentenoate
Workup and gas chromatographic separation as described in the
This work was financially supported by the Schweizerische Natio-
nalfonds zur Förderung der wissenschaftlichen Forschung, Bern
(grant 20-55'303-98) and the Bundesamt für Bildung und Wissen-
schaft, Bern (grant 97.0083 linked to the TMR project
FMRXCT970129).
preceding paragraph; 16%; bp 71–72 °C/12 mmHg; nD20 1.4735.
1H NMR: d = 5.94 (1 H, ddd, J = 16.6, 10.4, 7.4 Hz), 5.58 (2 H, m),
5.16 (1 H, d, J = 10.4 Hz), 5.14 (1 H, d, J = 16.6 Hz), 3.71 (3 H, s),
1.71 (3 H, s).
Anal. Calcd for C8H12O2 (140.2): C, 68.54; H, 8.63. Found: C,
68.75; H, 8.73.
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York

1836
M. Schlosser et al.
PAPER
(22) Wittig, G. Quart. Rev. 1966, 20, 191.
(23) (a) Tochtermann, W. Angew. Chem. 1966, 78, 355.
References
(1) Schlosser, M.; Desponds, O.; Lehmann, R.; Moret, E.;
Rauchschwalbe, G. Tetrahedron 1993, 49, 10175,
spec.10189–10193.
(2) Bates, R. B.; Gosselink, D. W.; Kaczynski, J. A.
Tetrahedron Lett. 1967, 8, 205.
(3) Heiszwolf, G. J.; Kloosterziel, H. Recl. Trav. Chim. Pays-
Bas 1967, 86, 807.
(4) Schlosser, M.; Rauchschwalbe, G. J. Am. Chem. Soc. 1978,
100, 3258.
(b) Tochtermann, W. Angew. Chem., Int. Ed. Engl. 1966, 5,
351.
(24) Bevan, C. W. L. J. Chem. Soc. 1951, 2340.
(25) Bunnett, J. F.; Garbisch, E. W.; Pruitt, K. M. J. Am. Chem.
Soc. 1957, 79, 387.
(26) (a) Suhr, H. Chem. Ber. 1964, 97, 3268. (b) Suhr, H. Chem.
Ber. 1964, 97, 3277.
(27) Desponds, O.; Huynh, C.; Schlosser, M. Synthesis 1998,
983.
(5) (a) Yasuda, H.; Ohnuma, Y.; Yamauchi, M.; Tani, H.;
Nakamura, A. Bull. Chem. Soc. Jpn. 1979, 52, 2036.
(b) See, also: Yasuda, H.; Yamauchi, M.; Ohnuma, Y.;
Nakamura, A. Bull. Chem. Soc. Jpn. 1981, 54, 1481.
(6) (a) Schlosser, M.; Stähle, M. Angew. Chem. 1982, 94, 142.
(b) Schlosser, M.; Stähle, M. Angew. Chem., Int. Ed. Engl.
1982, 21, 145. (c) Schlosser, M.; Stähle, M. Angew. Chem.
Suppl. 1982, 198.
(7) Bosshardt, H.; Schlosser, M. Helv. Chim. Acta 1980, 63,
2393.
(8) Ford, W. T.; M, J. Am. Chem. Soc. 1974, 96, 309.
(9) Schlosser, M.; Bosshardt, H.; Walde, A.; Stähle, M. Angew.
Chem., Int. Ed. Engl. 1980, 19, 303.
(10) Moret, E.; Schlosser, M. Tetrahedron Lett. 1984, 25, 1449.
(11) Rauchschwalbe, G.; Schlosser, M. Helv. Chim. Acta 1975,
58, 1094.
(12) Improved preparation: Schlosser, M.; Franzini, L. Synthesis
1998, 707, footnote 14.
(13) Finch, A.; Gardner, P. J.; Pearn, E. J. Recl. Trav. Chim.
Pays-Bas 1964, 83, 1314.
(14) Hoffmann, R. W.; Endersfelder, A.; Zeiss, H.-J. Carbohydr.
Res. 1983, 123, 320.
(28) (a) Salimgareeva, I. M.; Zhebarov, O. Z.; Bogatova, N. G.;
Yurev, V. P. Zh. Obshch. Khim. 1981, 51, 420. (b) Chem.
Abstr. 1981, 95, 81087v.
(29) Ansell, M. F.; Thomas, D. A. J. Chem. Soc. 1961, 539.
(30) Seyferth, D.; Pornet, J.; Weinstein, R. M. Organometallics
1982, 1, 1651.
(31) Hosomi, A.; Saito, M.; Sakurai, H. Tetrahedron Lett. 1980,
21, 3783.
(32) Woods, G. F.; Lederle, H. F. J. Am. Chem. Soc. 1951, 73,
2245.
(33) Crombie, L.; Harper, S. H.; Thompson, D. J. Chem. Soc.
1951, 2906.
(34) Meinwald, J.; Nozaki, H. J. Am. Chem. Soc. 1958, 80, 3132.
(35) Woods, G. F.; Bolgiano, N. C.; Duggan, D. E. J. Am. Chem.
Soc. 1955, 77, 1800.
(36) Gérard, F.; Miginiac, P. Bull. Soc. Chim. Fr. 1974, 1924.
(37) Berger, J. G.; Stogryn, E. L.; Zimmerman, A. A. J. Org.
Chem. 1964, 29, 950.
(38) Hartmann, J.; Muthukrishnan, R.; Schlosser, M. Helv. Chim.
Acta 1974, 57, 2261.
(39) Gauthier, J. Y.; Guindon, Y. Tetrahedron Lett. 1987, 28,
5985.
(15) Schlosser, M.; Coffinet, D. Synthesis 1971, 380.
(16) Schlosser, M.; Jenny, T.; Guggisberg, Y. Synlett 1990, 704.
(17) Hartmann, J.; Muthukrishnan, R.; Schlosser, M. Helv. Chim.
Acta 1974, 57, 2261.
(18) Schlosser, M. Modern Synthetic Methods, Vol. 6; Scheffold,
R., Ed.; Verlag Helvetica Chimica Acta: Basel, 1992, 227,
spec. 260–261.
(40) Stevens, R. V.; Cherpeck, R. E.; Harrison, B. L.; Lai, J.;
Lapalme, R. J. Am. Chem. Soc. 1976, 98, 6317.
(41) Burger, B. V.; du Plessis, E.; Garbers, C. F.; Pachler, K. G.
R. J. Chem. Soc., Perkin Trans. 1 1973, 584.
(42) Eilbracht, P.; Hüttmann, G.-E. Chem. Ber. 1990, 123, 1053.
(43) Margot, C.; Rizzolio, M.; Schlosser, M. Tetrahedron 1990,
46, 2411.
(19) Rauchschwalbe, G.; Schlosser, M.; unpublished results,
1976.
(44) Zellner, A. Doctoral Dissertation; Université de Lausanne:
Switzerland, 1997.
(20) (a) Tronov, B. V.; Krüger, E. A. Zhur. Russ. Fiz.-Khim
Obshch. 1926, 58, 1270. (b) Chem. Abstr. 1927, 21, 38879.
(21) (a) Glew, D. N.; Moelwyn-Hughes, E. A. Proc. Roy. Soc.
(London) 1952, A211, 254. (b) Chem. Abstr. 1952, 46,
10809. (c) Glew, D. N.; Moelwyn-Hughes, E. A. Disc.
Faraday Soc. 1953, 15, 150. (d) Chem. Abstr. 1954, 48,
678.
(45) Goel, S. C.; Grovenstein, E. Organometallics 1992, 11,
1565.
(46) Crombie, L.; Harper, S. H.; Smith, R. J. D. J. Chem. Soc.
1957, 2754.
Synthesis 2001, No. 12, 1830–1836 ISSN 0039-7881 © Thieme Stuttgart · New York