Iron-catalyzed coupling reaction between 1,1-dichloro-1-alkenes and Grignard reagents

Article abstract of DOI:10.1055/s-2004-835626

This letter reports the coupling reaction of Grignard reagents with 1,1-dichloro-1-alkenes in the presence of the environmentally friendly iron(III) catalyst. This non-toxic procedure is general and provides the di-coupled products as the major compounds. The scope and limitations of this new reaction are described.

Full text of DOI:10.1055/s-2004-835626

LETTER
2697
Iron-Catalyzed Coupling Reaction between 1,1-Dichloro-1-alkenes and
Grignard Reagents
a
a
a
a
b
C
M
oupling
R
eactionbet
i
w
een1
c
,1-Dichlor
o
k
-1-alkene
s
a
a
nd
G
rignard
ë
Reagents l Dos Santos, Xavier Franck, Reynald Hocquemiller, Bruno Figadère,* Jean-François Peyrat,
b
b
b
Olivier Provot, Jean-Daniel Brion, Mouâd Alami*
a
Laboratoire de Pharmacognosie, BioCIS – CNRS (UMR 8076), Université Paris-Sud, Faculté de Pharmacie,
rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France
Fax +33(1)46835399; E-mail: bruno.figadere@cep.u-psud.fr
b
Laboratoire de Chimie Thérapeutique, BioCIS – CNRS (UMR 8076), Université Paris-Sud, Faculté de Pharmacie,
rue Jean-Baptiste Clément, 92296 Châtenay-Malabry, France
E-mail: mouad.alami@cep.u-psud.fr
Received 6 September 2004
bromo derivatives (vide infra). Previously, Tamao et al.5
have studied the palladium-catalyzed reaction of aryl
Grignard reagents with 1,1-dichloro-1-alkenes to afford
Abstract: This letter reports the coupling reaction of Grignard
reagents with 1,1-dichloro-1-alkenes in the presence of the environ-
mentally friendly iron(III) catalyst. This non-toxic procedure is gen-
eral and provides the di-coupled products as the major compounds. stereoselectively the Z-chloro cross-coupled alkenes,
The scope and limitations of this new reaction are described.
which then could be engaged in a second cross-coupling
reaction with alkyl or aryl Grignard reagents producing
trisubstituted alkenes. However, these authors have point-
ed out that alkyl Grignard reagents do not react with 1,1-
dichloro-1-alkenes in the presence of the palladium cata-
Key words: Grignard reagents, iron, 1,1-dichloro-1-alkenes, tri-
substituted alkenes
6
lyst used. Under nickel-catalysis, Okamoto et al. have re-
Recently, during our investigations on Fe(III)-catalyzed
cross-coupling reactions of vinyl- and/or aryl halides with
ported that the reaction of 1,1-dichloro-2-phenyl-1-
alkenes with phenyl-magnesium bromide fails to stop at
the monoarylation stage and affords the reduced
monoarylated (E)-1,2-diphenyl-1-alkenes as the major
products. The cobalt-catalyzed coupling reaction of 1,1-
dichloroethylene or 1,1,2-trichloroethylene has also been
1
Grignard reagents, we observed that 2-aryl-1,1-dibromo-
1
-alkenes undergo selective hydrodebromination under
usual conditions [RMgX 1 equiv, THF–NMP, Fe(acac) 5
3
mol%, –10 °C, 0.5 h] to afford stereoselectively (E)-vinyl
2
bromides in good yields. Interestingly, we have found
7
studied by Cahiez et al. but no reaction was observed
that if a second Grignard reagent was added to the reaction
mixture the desired E-alkenes were thus obtained in good
when Grignard reagents were used.
overall yields (Scheme 1). In this work, we decided to Recently, a new environmentally friendly procedure using
extend this study and focused our attention on the use of the non-toxic iron(III) acetylacetonate was reported al-
less reactive 1,1-dichloro-1-alkenes in the Fe-catalyzed lowing the coupling of Grignard and organozinc reagents
coupling reaction with Grignard reagents.
with simple halogenoalkenes (e.g. chloro-, iodo- and
bromoalkenes) in a stereoselective manner. To the best of
8
Reference 2
our knowledge, no study has been reported on the iron
catalyzed-reaction with 1,1-dichloro-1-alkenes. There-
fore, we turned our attention to investigate the reactivity
of these derivatives towards Grignard reagents in the pres-
ence of the non-toxic iron(III) acetylacetonate catalyst.
The results of this study are now reported.
1
R1
Br R MgX
Fe(acac)3
Br R1MgX
Ar
Ar
Ar
Br
This work
1
R1
R1
Cl
R MgX
R
R
R
+
Fe(acac)3
R1
Cl
At first, we studied the reactivity of 1,1-dichloro-2-(4-
methoxyphenyl)ethylene (1) with butylmagnesium bro-
major
minor
R, R1 = aryl, alkyl
mide in the presence of Fe(acac) under different reaction
3
conditions (solvent, temperature, amount of catalyst and
Grignard reagent used, Equation 1, Table 1). The required
substrate 1 was readily prepared from para-methoxybenz-
aldehyde and triphenylphosphine–tetrachloromethane
mixture in dichloromethane.9
Scheme 1
Although the reactivity of 1,1-dibromo-1-alkenes with or-
ganometallic reagents under classical transition metal ca-
talysis (Pd, Ni) is now well documented, the coupling of
3
4
When BuMgBr (1.5 equivalents) was added to 1,1-dichlo-
ro-2-(4-methoxyphenyl)ethylene (1) in a THF–NMP so-
lution at –10 °C, in the presence of a catalytic amount of
1
,1-dichloro-1-alkenes has received little attention, prob-
ably because of their weaker reactivity compared to the
Fe(acac) (3 mol%), no reaction occurred and the starting
3
SYNLETT 2004, No. 15, pp 2697–2700
Advanced online publication: 22.10.2004
DOI: 10.1055/s-2004-835626; Art ID: G25904ST
0
7
.1
2
.2
0
0
4
material was recovered unchanged (entry 1). However,
when the same reaction was run in THF alone for one
hour, the dehydrochlorinated-coupled product 3(Z) was
©
Georg Thieme Verlag Stuttgart · New York

2
698
M. Dos Santos et al.
LETTER
Bu
Bu
or less polar solvents (Et O, CH Cl , toluene) did not
2
2
2
allow the reaction to occur (results not shown). When the
amount of Grignard reagent was increased the conversion
was not improved (entry 3), and some starting material
was recovered (34%). Thus, the catalyst and the Grignard
amounts were increased to 10 mol% and three equiva-
lents, respectively, leading to approximately the same
amounts of the different compounds (entry 4) with a high-
er ratio of di-coupled 2 versus mono-coupled reduced
compounds 3, and 18% of starting material was re-
covered. Finally, when the temperature was brought to
Bu
Cl
MeO
MeO
2
BuMgBr (n equiv)
+
Cl
Fe(acac)3 (x mol%),
solvent
MeO
1
3
Equation 1
Table 1 Reaction of 1,1-Dichloro-2-(4-methoxyphenyl)ethylene
1) with BuMgBr, in the Presence of Fe(acac)3
–
30 °C a higher yield of the di-coupled product 2 was thus
(
obtained (entry 5), and we observed complete disappear-
ance of starting material.
Entry BuMgBr Fe(acac) Solvent
Time Yield
(°C)
3
(
equiv) (mol%)
(%)a
We then decided to apply these reaction conditions to 1,1-
dichloro-2-(2-quinolyl)ethylene (4), since 2-substituted
quinoline derivatives have shown interesting in vitro and
in vivo leishmanicide activities.10 In a structure–activity
relationships study numerous quinolines have been syn-
thesized, and the crucial role of unsaturation (e.g. dou-
ble or triple bond) at the 2-position of the quinoline ring
has been highlighted for biological activity. Thus, we
were interested in preparing quinolines substituted at the
2
3(E) 3(Z)
Nrb
1
2
3
4
5
1.5
1.5
3
3
3
THF–NMP –10
THF
THF
THF
THF
–10
–10
–10
–30
51
32
45
65
0
2
7
9
20c
10d
10e
17f
11
3
3
10
10
3
2
-position by a disubstituted alkenyl moiety. Quinoline 4,
a
b
c
d
e
f
Yields of isolated products.
Exclusively recovered starting material.
4% Of recovered starting material.
4% Of recovered starting material.
8% Of recovered starting material.
No starting material was recovered.
prepared in good yield from 2-quinaldine in a three-steps
sequence (i. 2.5 equiv NBS in refluxed CHCl , ii. Me NH
treatment in a methanol–water mixture under reflux, iii.
CCl –PPh treatment of 2-quinaldehyde so obtained), was
treated by several Grignard reagents (3 equivalents) in
THF at –30 °C, in the presence of 10 mol% of Fe(acac)3,
and the results are reported in Scheme 2.
3
2
1
3
1
12
4
3
obtained in 20% yield, together with the di-coupled prod-
uct 2 (51%) and the starting material was recovered (14%, It is noteworthy that primary aliphatic as well as aromatic
entry 2). This result is interesting and shows that 2-aryl- Grignard reagents gave the di-coupled products 5a–d in
1
,1-dichloro-1-alkenes afford mainly di-coupled prod- high yields (70–80%) as the single products. Interesting-
ucts, whereas 2-aryl-1,1-dibromo-1-alkenes give the ly, the 1,5-di-Grignard reagent gave exclusively the cy-
hydrodebrominated products under the almost identical clized product 5e in excellent isolated yield (84%)
2
reaction conditions (THF–NMP, vide infra). The solvent through an intramolecular coupling reaction; no products
effect was then studied, but more polar solvents (DMSO) resulting from intermolecular reactions could be isolated.
Me2NH
NBS
H2O/MeOH
Br
N
N
N
O
Br
PPh3/CCl4
Cl
Cl
Cl
R
c-HexMgBr (3 equiv)
RMgBr (3 equiv)
N
N
N
Fe(acac)3 (10 mol%),
THF, –30 °C, 3 h
Fe(acac)3 (10 mol%),
THF, –30 °C, 1.5–3 h
R
6
: 64% (5:1)
4
5a : R = Bu : 76%
BrMg
5b : R = Et : 70%
MgBr
3
5c : R = 4-MePh : 72%
Fe(acac)3 (10 mol%),
THF, –30 °C, 3 h
5d : R = 2-Thienyl : 80%
N
5e : 84%
Scheme 2
Synlett 2004, No. 15, 2697–2700 © Thieme Stuttgart · New York

LETTER
Coupling Reaction between 1,1-Dichloro-1-alkenes and Grignard Reagents
2699
When 1,1-dichloro-2-(2-quinolyl)ethylene (4) was treated with 1,1-dichloro-2-(2-quinolyl)ethylene (4) which led to
by 3 equivalents of c-hexylmagnesium bromide, surpris- the mono-cross-coupled product 6. With an aryl Grignard
ingly, the reaction stopped at the monoalkylation stage reagent, the dicoupled product 8e was not formed but in-
and a 5:1 mixture of undetermined E/Z mono-coupled stead the alkene 9e(E) was obtained as the major product
chloro alkenes 6 was obtained in 64% yield, and no di- with only trace amount of the 9e(Z)-isomer.
coupled product could be isolated.
In conclusion, we describe herein the iron(III)-catalyzed
We then decided to study the reaction of aliphatic 1,1- cross-coupling reaction of 1,1-dichloro-1-alkenes with
1
3
dichloro-1-alkenes (Equation 2 and Table 2), and choose Grignard reagents. This reaction leads mainly to the di-
-benzyloxy-1,1-dichlorobut-1-ene (7) as starting materi- coupled products in good to excellent yields and requires
4
al. This latter compound was prepared as described above mild conditions (–30 °C in a few hours). Nevertheless, in
from the corresponding aldehyde. We already reported one case we obtained the mono-coupled adduct, where the
that when the corresponding aliphatic 1,1-dibromo-1-alk- remaining chloride atom could be engaged in a second
enes were subjected to Grignard reagents in the presence coupling reaction, leading to unsymmetrical trisubstituted
2
of Fe(III) catalyst, no coupling reactions occured. In- alkenes. Furthermore, these results highlight the differ-
stead, alkynes were obtained through a Fritsch–Butten- ence of reactivity of 1,1-dichloro-1-alkenes and 1,1-di-
berg–Wiechell rearrangement.
bromo-1-alkenes towards Grignard reagents in the
presence of iron(III) catalyst. Further studies for elucida-
tion of the mechanism of this reaction are undertaken in
our laboratories. Furthermore, the quinoleine derivatives
prepared in this study are now evaluated for their anti-
parasitic properties against several trypanosomia species,
and the results will be published elsewhere.
R
R
O
Cl RMgBr (3 equiv)
O
8
+
R
Fe(acac)3 (10mol%),
THF, –30 °C,
Cl
7
O
2.5–18 h
a : R = Bu
9
b : R = C12H25
c : R = (CH2)3OH
d : R = c-Hex
e : R = Ph
Acknowledgment
The CNRS is gratefully acknowledged for financial support of this
research. We wish to thank J.-C. Jullian for the NMR experiments,
Dr. A. Fournet for his interest in this study, and Blandine Seon,
Aude Jacob together with Lok-Hang Yan for their technical assi-
stance.
Equation 2
Table 2 Reaction of 4-Benzyloxy-1,1-dichlorobut-1-ene (7) with
Grignard Reagents in the Presence of 10 mol% of Fe(acac) at –30 °C
3
in THF
Entry RMgBr (R)
Time (h) Yield (%)a
References
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1) (a) Defretin, J.; Saez, J.; Franck, X.; Hocquemiller, R.;
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–
–
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–
–
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–
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(
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(
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3
3) (a) Bryant-Friedrich, A.; Neidlein, R. Synthesis 1995, 1506.
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2
). Again, these results are quite remarkable since the cor-
responding aliphatic 1,1-dibromo-1-alkenes do not lead to
2
the cross-coupled products. In the case of less reactive
alkyl Grignard reagents, such as the functionalized b-hy-
droxylated reagent or the cyclohexyl reagent, the mono-
coupled-reduced compounds 9c,d were obtained as the
major products of the reaction (as the E-isomer or as a
mixture of E- and Z-isomers). This result is unexpected in
regards to the reactivity of c-hexylmagnesium bromide
Ed. 2000, 39, 1042. (g) Hanisch, I.; Brückner, R. Synlett
2000, 374. (h) Bauer, A.; Miller, M. W.; Vice, S. F.;
McCombie, S. W. Synlett 2001, 254. (i) Uenishi, J.;
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Synlett 2004, No. 15, 2697–2700 © Thieme Stuttgart · New York

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700
M. Dos Santos et al.
LETTER
Huh, D. H.; Oh, J. S.; Min, G. H.; Kim, B. H.; Lee, D. H.;
Hz, 2 H), 6.20 (s, 1 H), 3.81 (s, 3 H), 2.16 (m, 4 H), 1.42 (m,
Hwang, J. K.; Kim, Y. G. Tetrahedron 2001, 57, 8283.
8 H), 0.94 (t, J = 7.1 Hz, 3 H), 0.90 (t, J = 7.1 Hz, 3 H) ppm.
1
3
(
m) Uenishi, J.; Matsui, K.; Ohmiya, H. J. Organomet.
Chem. 2002, 653, 141. (n) Hopf, H. Angew. Chem. Int. Ed.
001, 40, 705.
C NMR (50 MHz): d = 157.7, 142.6, 131.4, 129.7, 124.1,
113.5, 55.2, 37.1, 30.5, 30.4, 22.9, 22.6, 14.0, 13.9 ppm.
1
2
1,1-Dibutyl-2-(2-quinolyl)ethylene (5a): H NMR (200
(
4) (a) Ratovelomanana, V.; Hammoud, A.; Linstrumelle, G.
Tetrahedron Lett. 1987, 28, 1649. (b) For a review, see:
Alami, M.; Peyrat, J. F.; Brion, J. D. Synthesis 2000, 1499.
5) Minato, A.; Suzuki, K.; Tamao, K. J. Am. Chem. Soc. 1987,
MHz): d = 8.04 (d, J = 8.4 Hz, 2 H), 7.74 (d, J = 8.1 Hz, 1
H), 7.66 (td, J = 8.2, 1.1 Hz, 1 H), 7.45 (t, J = 7.4 Hz, 1 H),
7.30 (d, J = 8.4 Hz, 1 H), 6.47 (s, 1 H), 2.67 (t, J = 7.3 Hz,
2 H), 2.28 (t, J = 6.9 Hz, 2 H), 1.60 (m, 4 H), 1.37 (m, 4 H),
(
(
(
(
1
3
109, 1257.
0.97 (t, J = 7.4 Hz, 3 H), 0.93 (t, J = 7.3 Hz, 3 H) ppm.
NMR (50 MHz): d = 157.6, 151.3, 148.0, 135.4, 129.2,
129.1, 127.2, 126.2, 125.6, 124.4, 122.4, 38.1, 31.3, 30.6,
C
6) Okamoto, Y.; Yoshikawa, Y.; Hayashi, T. J. Organomet.
Chem. 1989, 359, 143.
7) Cahiez, G.; Avedissian, H. Tetrahedron Lett. 1998, 39,
30.3, 23.0, 22.6, 14.0, 13.9 ppm. ESI-MS: m/z (%) = 268
+
6159.
(100) [MH ].
1
8) (a) Cahiez, G.; Avedissian, H. Synthesis 1998, 1199.
1,1-Diethyl-2-(2-quinolyl)ethylene (5b): H NMR (200
(
(
5
5
2
b) Tamura, M.; Kochi, J. J. Am. Chem. Soc. 1971, 93, 1487.
c) Neuemann, S. M.; Kochi, J. K. J. Org. Chem. 1975, 40,
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001, 1901. (f) Fürstner, A.; Leitner, A. Angew. Chem. Int.
MHz): d = 8.07 (d, J = 6.9 Hz, 1 H), 8.02 (d, J = 6.4 Hz, 1
H), 7.73 (d, J = 8.1 Hz, 1 H), 7.66 (td, J = 7.1, 1.5 Hz, 1 H),
7.45 (t, J = 7.4 Hz, 1 H), 7.31 (d, J = 8.6 Hz, 1 H), 6.47 (br
s, 1 H), 2.65 (q, J = 7.6 Hz, 2 H), 2.30 (qd, J = 7.4, 1.1 Hz,
2 H), 1.19 (t, J = 7.2 Hz, 3 H), 1.16 (t, J = 7.3 Hz, 3 H) ppm.
1
3
Ed. 2002, 41, 609.
C NMR (50 MHz): d = 157.5, 153.4, 147.8, 135.6, 129.2,
(
9) (a) Rabinowitz, R.; Marcus, R. J. Am. Chem. Soc. 1962, 84,
129.0, 127.2, 126.2, 125.6, 123.1, 122.2, 30.3, 24.6, 12.9,
+
1
(
312. (b) Appel, R. Angew. Chem. 1975, 87, 863.
c) Vinczer, P.; Struhar, S.; Novak, L.; Szantay, C.
Tetrahedron Lett. 1992, 33, 683.
12.5 ppm. ESI-MS: m/z (%) = 234 (35) {M + Na ], 212 (100)
+
[MH ].
1
1,1-Di-p-toluyl-2-(2-quinolyl)ethylene (5c): H NMR (200
(
10) (a) Fournet, A.; Hocquemiller, R.; Roblot, F.; Cavé, A.;
MHz): d = 8.04 (d, J = 8.8 Hz, 1 H), 7.72 (d, J = 8.7 Hz, 1
H), 7.64 (m, 2 H), 7.44 (t, J = 7.3 Hz, 1 H), 7.31 (m, 3 H),
7.15 (m, 6 H), 6.84 (d, J = 8.8 Hz, 1 H), 2.40 (s, 3 H), 2.38
Richomme, P.; Bruneton, J. J. Nat. Prod. 1993, 56, 1547.
(b) Fournet, A.; Angelo Barrios, A.; Muñoz, V.;
1
3
Hocquemiller, R.; Roblot, F.; Bruneton, J.; Richomme, P.;
Gantier, J. C. PCT/FR92/00903, 1992. (c) Fournet, A.;
Ferreira, M. E.; Torres de Ortiz, S.; Fuentes, S.; Nakayama,
H.; Rojas de Arias, A.; Schinini, A.; Hocquemiller, R.
Antimicrob. Agents Chemother. 1996, 40, 2447.
(s, 3 H) ppm. C NMR (50 MHz): d = 157.5, 148.1, 147.3,
139.8, 138.1, 137.8, 136.9, 134.7, 130.3, 129.3, 128.9,
128.1, 127.9, 127.3, 126.5, 126.0, 122.0, 21.3, 21.1 ppm.
+
+
ESI-MS: m/z (%) = 358 (10) [M + Na ], 336 (100) [MH ].
1
1,1-Dithienyl-2-yl-2-(2-quinolyl)ethylene (5d): H NMR
(
d) Fournet, A.; Gantier, J. C.; Gautheret, A.; Leysalles, L.;
(200 MHz): d = 8.03 (d, J = 8.2 Hz, 1 H), 7.80 (d, J = 8.7
Hz, 1 H), 7.69 (d, J = 7.6 Hz, 1 H), 7.65 (dd, J = 7.1, 1.6 Hz,
1 H), 7.45 (m, 3 H), 7.32 (dd, J = 5.0, 1.9 Hz, 1 H), 7.08 (s,
Munos, M. H.; Mayrargue, J.; Moskowitz, H.; Cavé, A.;
Hocquemiller, R. J. Antimicrob. Chemother. 1994, 33, 537.
(
de Bilbao, N.; Torres, S.; Schinini, A.; Fournet, A.
Phytother. Res. 2001, 15, 630.
13
e) Nakayama, H.; Ferreira, M. E.; Rojas de Arias, A.; Vera
1 H), 7.05 (m, 3 H), 6.91 (d, J = 8.7 Hz, 1 H) ppm. C NMR
(50 MHz): d = 156.1, 147.9, 146.4, 139.3, 135.0, 133.1,
129.4, 129.1, 129.0, 128.9, 127.5, 127.4, 127.3, 127.1,
126.6, 126.5, 126.4, 121.5 ppm. ESI-MS: m/z (%) = 342 (15)
(
11) (a) Fakhfakh, M. A.; Franck, X.; Fournet, A.; Hocquemiller,
R.; Figadère, B. Tetrahedron Lett. 2001, 42, 3847.
+
[M + Na], 320 (100) [MH ].
1,1-Cyclohexyliden-2-(2-quinolyl)ethylene (5e): H NMR
1
(
b) Fakhfakh, M. A.; Franck, X.; Fournet, A.; Hocquemiller,
R.; Figadère, B. Synth. Commun. 2002, 32, 2863.
12) Through the slightly modified procedure of: Bankston, D.
Synthesis 2004, 283.
13) Typical Procedure and Selected Spectroscopic Data: In a
round-bottomed flask, under a nitrogen atmosphere,
containing the 1,1-dichloro-1-alkene (1.00 mmol) and
(200 MHz): d = 8.05 (d, J = 8.5 Hz, 2 H), 7.75 (d, J = 7.9
Hz, 1 H), 7.67 (td, J = 8.3, 1.3 Hz, 1 H), 7.46 (t, J = 7.8 Hz,
1 H), 7.32 (d, J = 8.5 Hz, 1 H), 6.48 (s, 1 H), 2.75 (m, 2 H),
(
(
1
3
2.36 (t, J = 5.6 Hz, 2 H), 1.66 (m, 6 H) ppm. C NMR (50
MHz): d = 157.6, 149.9, 147.9, 135.7, 129.3, 129.1, 127.3,
126.3, 125.8, 122.6, 122.4, 38.1, 29.9, 28.6, 27.8, 26.5 ppm.
+
Fe(acac) (35.3 mg, 0.10 mmol) was added THF (1.2 mL).
ESI-MS: m/z (%) = 224 (100) [MH ].
4-Benzyloxy-1,1-dibutylbut-1-ene (8a): H NMR (200
3
1
The reaction mixture was cooled to –30 °C and the desired
Grignard reagent (3.00 mmol of typically 1 M solution in
THF) was added dropwise. The red colored solution turned
dark brown to black (depending on the Grignard reagent).
The reaction mixture was stirred for 1.5 h to 18 h, until the
disappearance of starting material as judged by TLC. A 1 M
aq HCl solution (5.0 mL) was then added, and the two layers
were separated. After extraction of the organic layer by
EtOAc (2 × 20 mL), the combined organic layers were
washed three times with H O, then dried over MgSO ,
MHz): d = 7.36 (m, 5 H), 5.13 (br t, J = 7.0 Hz, 1 H), 4.53 (s,
2 H), 3.47 (t, J = 7.2 Hz, 2 H), 2.36 (q, J = 7.1 Hz, 2 H), 2.00
1
3
(m, 4 H), 1.33 (m, 8 H), 0.91 (t, J = 6.8 Hz, 6 H) ppm.
NMR (50 MHz): d = 142.0, 138.7, 128.3, 127.6, 127.4,
C
119.9, 72.8, 70.5, 36.6, 30.7, 30.4, 30.0, 28.5, 22.9, 22.5,
14.0 ppm. ESI-MS: m/z (%) = 297 (81) [M + Na ], 275 (16)
+
+
[MH ].
1
4-Benzyloxy-1,1-didodecylbut-1-ene (8b): H NMR (200
MHz): d = 7.34 (m, 5 H), 5.12 (br t, J = 7.0 Hz, 1 H), 4.56 (s,
2
4
filtered, and concentrated under vacuum. The crude residue
was then purified by silica gel column chromatography to
2 H), 3.46 (t, J = 7.2 Hz, 2 H), 2.35 (q, J = 7.1 Hz, 2 H), 2.00
1
3
(m, 4 H), 1.27 (m, 40 H), 0.89 (t, J = 6.4 Hz, 6 H) ppm.
NMR (50 MHz): d = 142.1, 138.7, 128.3, 127.6, 127.4,
C
yield the expected adducts (see in the text for yields).
1
1
,1-Dibutyl-2-(4-methoxyphenyl)ethylene (2): H NMR
119.9, 72.8, 70.5, 37.0, 31.9, 29.8, 29.7, 29.5, 29.4, 28.5,
28.2, 22.7, 14.1 ppm. ESI-MS: m/z (%) = 499 (100) [MH ].
+
(
200 MHz): d = 7.14 (d, J = 8.7 Hz, 2 H), 6.86 (d, J = 8.8
Synlett 2004, No. 15, 2697–2700 © Thieme Stuttgart · New York