Cobalt-catalyzed mono-coupling of R3SiCH2MgCl with 1,2-dihalogenoethylene: A general route to γ-substituted (E)-allylsilanes

Article abstract of DOI:10.1016/j.tetlet.2004.04.098

The reaction of trimethylsilylmethylmagnesium chloride (TMSCH ₂MgCl) with 1,2-dihalogenoethylene in the presence of 1mol% of Co(II) or Co(III) acetylacetonate in THF or THF-NMP proceeded exclusively in a mono-coupling pathway to provide 3-trimethylsilyl-1-halogeno-1-propene with >99% of E geometry in high yield, which was converted to a variety of γ-substituted allylsilanes by Ni- or Pd-catalyzed coupling with organometallic compounds.

Full text of DOI:10.1016/j.tetlet.2004.04.098

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 4677–4679
Cobalt-catalyzed mono-coupling of R3SiCH2MgCl with 1,2-
dihalogenoethylene: a general route to c-substituted (E)-allylsilanes
Taku Kamachi, Akiko Kuno, Chikashi Matsuno and Sentaro Okamoto*
Department of Applied Chemistry, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
Received 2 April 2004; revised 15 April 2004; accepted 19 April 2004
Abstract—The reaction of trimethylsilylmethylmagnesium chloride (TMSCH2MgCl) with 1,2-dihalogenoethylene in the presence of
1mol % of Co(II) or Co(III) acetylacetonate in THF or THF–NMP proceeded exclusively in a mono-coupling pathway to provide
3-trimethylsilyl-1-halogeno-1-propene with >99% of E geometry in high yield, which was converted to a variety of c-substituted
allylsilanes by Ni- or Pd-catalyzed coupling with organometallic compounds.
Ó 2004 Elsevier Ltd. All rights reserved.
Allylsilanes are versatile compounds in organic synthesis
useful as an allylating reagent or a starting material.1
Therefore, numerous methods have been developed for
their preparation, and several substituted allylsilanes as
well as simple unsubstituted ones have become obtain-
able from commercial sources. c-Substituted allylsilane
1 is an important member in the chemistry field that has
been widely used in inter- and intramolecular reactions
in the presence of a Lewis acid or Fꢀ with a variety of
electrophiles such as carbonyl, imino and iminium
compounds and a,b-unsaturated carbonyl compounds,
where high regio- and/or stereoselectivity has often been
attained. Therefore, development of a general method
for their preparation is desired.2 Herein we describe an
efficient preparation of (E)-3-silyl-1-halogeno-1-propene
(2)3 by a selective Co-catalyzed mono-coupling of 1,2-
dihalogenoethylene with TMSCH2MgCl (TMS ¼ tri-
methylsilyl), which allows a general access to (E)-c-
substituted allylsilanes 1 by the metal-catalyzed cross-
coupling with a variety of organometallic reagents
(Scheme 1).
Me3Si
R
Me3Si
X
2a (X = Cl)
2b (X = Br)
1
Me3Si
Scheme 1.
MgCl
X
+
X
tion of mono-coupling product 2a. Thus, (E)-1,2-
dichloroethylene (4.0 mmol) was treated with
TMSCH2MgCl4 (2.0 mmol) in the presence of 1mol % of
Ni, Pd, Co or Fe catalyst precursor. As can be seen from
Table 1summarizing the results, nickel-catalyzed reac-
tions5 afforded a mixture of (E)-3-trimethylsilyl-1-
chloro-1-propene (2a) and 1,4-bis(trimethylsilyl)-2-but-
ene (3) (entries 1–4).6 It was noteworthy that the reaction
with Ni–PPh3 complexes gave 2a predominantly (entries
1and 2) but Ni-complexes with a bidentate phosphine
ligand such as Cl2Ni(dppp) and Cl2Ni(dppb) catalyzed
production of 3 mainly (entries 3 and 4). As shown in
entries 6–8, to our delight, the reaction catalyzed by
Co(acac)2 or Co(acac)3 proceeded smoothly with nearly
complete selectivity of mono-coupling to provide 2a in
excellent yield, the isomeric purity of which was found to
be >99% E by GC and 500 MHz 1H NMR analyses.7 In
these reactions, use of NMP (N-methylpyrrolidin-2-one)
as an additive affected the reaction rate but not the
yield and selectivity (entries 6 and 7). Cahiez and
Avedissian originally reported the reaction of 1,2-di-
chloroethylene with alkyl-Grignard reagents providing
First, we investigated a transition metal-catalyzed cou-
pling reaction of (E)-1,2-dichloroethylene (>99% E),
which is commercially available at low price, with
TMSCH2MgCl to find conditions for selective produc-
Keywords: Allylsilane; Co-catalyst; Cross-coupling.
* Corresponding author. Tel.: +81-45-481-5661; fax: +81-45-413-9770;
e-mail: okamos10@kanagawa-u.ac.jp
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.04.098

4678
T. Kamachi et al. / Tetrahedron Letters 45 (2004) 4677–4679
Table 1a
Me3Si
Me3Si
Cl
Me3Si
Cl
MgCl
Cl
catalyst
2a
3
+
SiMe3
Entry
Catalyst (1mol %)
Conditions
Yield, % b
2a
3
1c
2
3
4
5
6
7
8
9
Br2Ni(PPh3)2 + 2PPh3
Cl2Ni(PPh3)2 + 2PPh3
Cl2Ni(dppp)2
0 °C, 30 min, benzene–ether
0 °C to rt, 2.5 h, ether
0 °C to rt, 2.5 h, ether
0 °C to rt, 2.5 h, ether
0 °C to rt, 12 h, THF–ether
0 °C, 5 h, THF
0 °C, 15 min, THF–NMP (4:1)
0 °C, 15 min, THF–NMP (4:1)
0 °C to rt, 1.5 h, THF–NMP (4:1)
78
33
15
20
10
5
87
32
Cl2Ni(dppb)2
Cl2Pd(PPh3)2
Trace
86
88
Trace
0
Co(acac)3
Co(acac)3
0
d
Co(acac)2
Fe(acac)2
81
Trace
0
Trace
dppp: 1,3-bis(diphenylphosphino)propane.
dppb: 1,4-bis(diphenylphosphino)butane.
acac: acetylacetonato.
a Reactions were performed using 2.0 mmol of Grignard reagent, 4.0 mmol of 1,2-dichloroethylene and 1 mol % of catalyst.
b GC yield.
c See Ref. 1. 1,2-Dichloroethylene (5 equiv) was used.
d Tetrahydrate was used.
mono-coupling products exclusively where addition of
NMP as a co-solvent was suggested for attaining good
Si
MgCl
Co(acac)3
(1 mol%)
yield.8 The yield of the reaction carried out here was
somewhat better than those of the reaction with the usual
alkyl-Grignard reagents reported by Cahiez. It can be
assumed that the absence of b-hydride in TMSCH2MgCl
might avoid other reaction(s) than the desired coupling.
With these results, we carried out 20 mmol scale synthesis
and 2a could be isolated in pure form by distillation in
90% yield. Pd- and Fe-compounds did not catalyze this
reaction (entries 5 and 9).
+
Si
Cl
THF-NMP
Cl
Cl
4
78% yield
Scheme 3.
With c-halo-(E)-allylsilanes 2a and 2b in hand, we car-
ried out their conversion to 1 by transition metal-cata-
lyzed coupling reactions. As can be seen from Table 2
summarizing the several representative results, 1 with
methyl as well as normal and secondary alkyl and aryl
groups could be readily prepared by the Ni-catalyzed
coupling with the corresponding Grignard reagent
(Kumada–Tamao reaction).5 It is noteworthy that the
Suzuki–Miyaura coupling9 of bromide 2b with boranes
was effective for synthesis of 1 having a functional group
as shown in entry 7.
Next we tried a Co-catalyzed coupling of TMSCH2MgCl
with (Z)-1,2-dichloroethylene and, unfortunately, found
that the reaction did not proceed at all. However, the
results prompted us to carry out the reaction with a
mixture of (E)- and (Z)-1,2-dibromoethylene, which is
commercially available at low price. Thus, a mixture of
E- and Z-isomers of 1,2-dibromoethylene (E/Z ¼ 35:65,
total 5 equiv) was treated with TMSCH2MgCl in the
presence of 1mol % of Co(acac) 2 in THF–NMP (Scheme
2). As expected, only (E)-3-trimethylsilyl-1-bromopro-
pene (2b) was produced in good yield of 74%.
In addition the use of 2 as a substrate for metal-cata-
lyzed coupling reactions, as illustrated in Scheme 4, 2a
and 2b are useful as an equivalent of 3-silyl-1-propynyl
and 3-silyl-1-propenyl anions. Thus, treatment of 2a
with LDA (2 equiv) and the following addition of alde-
hyde afforded the corresponding adduct, whereas
(E)-allylic alcohol was obtained by treatment of 2b with
t-BuLi and then aldehyde.10
Similarly, c-halogenoallylsilanes having a silyl moiety
other than trimethylsilyl could be prepared without loss
of yield and selectivity (Scheme 3).7
Me3Si
MgCl
Co(acac)3
(1 mol%)
Me3Si
Br
+
THF-NMP
In conclusion, we have developed a selective mono-
coupling reaction of R3SiCH2MgCl with 1,2-dihalogeno-
ethylene, which opens up a general method for prepa-
ration of c-substituted (E)-allylic silanes. Further study
for the preparation and synthetic utilization of func-
tionalized allylsilanes is underway in our laboratories.
0 oC, 20 min
2b
Br
Br
74% yield
E only
(E:Z = 35:65,
total 5 equiv.)
Scheme 2.

T. Kamachi et al. / Tetrahedron Letters 45 (2004) 4677–4679
4679
Table 2
R-M
Me3Si
X
Me3Si
R
catalyst
2a (X = Cl)
2b (X = Br)
1
Entry
1
2
R–M (solvent) catalyst (mol %)
Product
Yield, %a
95b
Me3Si
Me
2a
MeMgI (ether)
Cl2Ni(dppp) (2)
1a
Me3Si
Me3Si
2
3
2a
2a
n-C6H13MgBr (THF)
Cl2Ni(dppp) (2)
83
59
5
1b
c-C5H9MgCl (ether)
Cl2Ni(dppp) (2)
1c
4
2a
2a
c-C6H11MgCl (ether)
Cl2Ni(dppp) (2)
93
Me3Si
Me3Si
1d
R
5
6
91
95
R
MgBr (THF)
1e (R = H)
1f (R = Me)
Cl2Ni(dppp) (2)
CN
Me3Si
9-BBN
CN
7
2b
(4)
58
Cl2Pd(dppf)
K3PO4
1g
a Isolated yield unless otherwise indicated. Reaction was not optimized.
b GC yield.
2 LDA
1980, 21, 4369; For 2b: (c) Nishiyama, H.; Narimatsu, S.;
Itoh, K. Tetrahedron Lett. 1981, 22, 5289; (d) Angell, R.;
Parsons, P. J.; Naylor, A.; Tyrrell, E. Synlett 1992, 599; (e)
Parsons, P. J.; Angell, R.; Naylor, A.; Tyrell, E. J. Chem.
Soc., Chem. Commun. 1993, 366.
THF
then
PhCHO
TMS
2a
2b
OH
54% yield
(not optimized)
4. Prepared from TMSCH2Cl and magnesium turnings in
ether or THF and titrated by using acid and base. Yields
shown in Table 1and Scheme 2 were based on the amount
of the Grignard reagent used.
5. Tamao, K.; Sumitani, K.; Kumada, M. J. Am. Chem. Soc.
1972, 94, 4374.
2 t-BuLi
ether-pentane
then
PhCHO
TMS
OH
60% yield
6. One of the authors (S.O.) reported the preparation of 2a
by the reaction shown in entry 1in Table 1, in which 2a
was obtained by distillation as a benzene solution:
Okamoto, S.; Tani, K.; Sato, F.; Sharpless, K. B.;
Zargarian, D. Tetrahedron Lett. 1993, 34, 2509.
7. H NMR (CDCl3, 500 MHz): 2a: d 5.87 (dt, J ¼ 13, 8.5 Hz,
1H), 5.51 (d, J ¼ 13 Hz, 1H), 1.48 (d, J ¼ 8:5 Hz, 2H),
0.03 (s, 9H); 2b: d 6.16 (dt, J ¼ 13, 8.5 Hz, 1H), 5.82 (dt,
J ¼ 13, 1.0 Hz, 1H), 1.52 (dd, J ¼ 1:0, 8.5 Hz, 2H), 0.06 (s,
9H); 4: d 7.39–7.57 (m, 5H), 5.90 (ddt, J ¼ 1:0, 13, 8.5 Hz,
1H), 5.77 (dd, J ¼ 1:0, 13 Hz, 1H), 1.75 (d, J ¼ 8:5 Hz,
2H), 0.35 (s, 6H).
(not optimized)
Scheme 4.
Referencesand notes
1. Langkopf, E.; Schinzer, D. Chem. Rev. 1995, 95, 1375;
Weber, W. P. Silicon Reagents for Organic Synthesis;
Springer: New York, 1983.
2. For synthesis of c-substituted allylsilanes, see: Thibau-
deau, S.; Gouverneur, V. Org. Lett. 2003, 5, 4891, and
references cited therein.
8. Cahiez, G.; Avedissian, H. Tetrahedron Lett. 1998, 39,
6159.
9. Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
10. CrCl2-mediated reaction of 2b with aldehydes providing
d-trimethylsilyl allylic alcohols has been reported: see
Refs. 3d,e.
3. An E- and Z-mixture of 2a or 2b has been prepared from
the corresponding 1,3-dihalopropene by the reaction with
Cl3SiH and the following methylation with MeMgBr. For
preparation and synthetic utilization of 2, see: (a) for 2a,
Ochiai, M.; Fujita, E. J. Chem. Soc., Chem. Commun.
1980, 1118; (b) Ochiai, M.; Fujita, E. Tetrahedron Lett.