Chemistry Reference
In-Depth Information
Me
Me
MeO
MeO
HO
N
Si
, Et
3
N,
MeCN, reflux
R
1
= CO
2
Me 93% (GC)
R
1
= Ph 84% (GC)
109
R
1
X
N
: [PdX
2
]
R
1
I
N
HO
S
S
X
MeO
Si
51
108
110
N
MeO
Me
Me
109
Scheme 46 Heck reaction of 2-iodothiophene with alkenes using catalyst I-Pd [
337
]
O
1. Pd(OAc)
2,
DPPP,
Et
3
N, [ bmim ][ BF
4
]
2. HCl
Pd(OAc)
2,
DP PP ,
Et
3
N, [bmim][BF
4
]
Br
OH
Br
OH
2- Br 89%
3- Br 82%
2- Br 93%
3- Br 89%
OBu
S
S
S
S
111
112
113
111
114
115
Scheme 47 Heck arylation of butyl vinyl ether and allyl alcohol in an ionic liquid [
340
]
R
1
R
1
R
1
Br
Br
Br
[PdCl(C
3
H
5
)]
2
/
1
/
2
66,
K
2
CO
3,
NMP, 150 °C, 20 h
R
1
S
S
S
116
117
118
119
Scheme 48 Palladium-catalyzed Heck reactions with 3,4-dibromothiophene [
341
]
cross-coupling reaction of 2,5-dibromothiophene with tristyrylindium as nucleo-
philic reagent [
339
].
The palladium-catalyzed Heck reactions of 3- and 2-bromothiophene 111 with
the electron-rich olefins butyl vinyl ether 112 and allyl alcohol 114 proceed
effectively in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate
(Scheme
47
)[
340
]. The special feature of this reaction is that only branched olefin
products are formed using the imidazolium ionic liquid, whereas the utilization of
normal solvents gives rise to a mixture of regioisomers.
Alternatively, a catalytic system consisting of the tetrapodal phosphine ligand
Tedicyp 66 and the allylpalladium chloride dimer ([PdCl(C
3
H
5
)]
2
) can be used for
efficient Heck vinylation reactions (Scheme
48
, Table
26
)[
341
]. The cross-
coupling of 3,4-dibromothiophene 116 with various alkenes 117 gives rise to the
corresponding vinylated products 118 and 119.
Tetra(2-thienyl)ethylene (TTE) derivatives 122 can be synthesized by Suzuki-
Miyaura reactions of a
cis
-boronic ester 121 with differently functionalized
bromothiophenes 120 (Scheme
49
, Table
27
)[
342
].
Vic
-bis(pinacolatoboryl)ethyl-
ene 121 can be isolated from the reaction of di(2-thienyl)acetylene with bis-
pinacolato-diboron beforehand, but is subsequently employed as crude intermediate
