Chemistry Reference
In-Depth Information
1.
(Ph
3
P)
4
Pd, CuI,
n
-PrNH
2
2.
(Ph
3
P)
4
Pd, CuI,
n
-PrNH
2
Si
t
-BuPh
2
1. H
3
O
+
2.
Si
t
-BuPh
2
Si
t
-BuPh
2
Li
Cl
CH(OEt)
2
OM
e
Cl
OMe
CH(OEt)
2
2.375
2
.
3
7
2
.
3
OH
1. TBAF
2.
CO
2
Me
H
I
CO
2
Me
(Ph
3
P)
4
Pd, CuI, Et
3
N
CO
2
Me
Δ
OMe
OMe
OTBS
OR
2.380
2.378
R = H
2.379
R = TBS
Scheme 2.117
(MeCN)
2
PdCl
2
,
(
t
-Bu)
3
P, CuI, Et
3
N
+
MeO
Br
MeO
Ph
Ph
2.381
2.382
Scheme 2.118
Ph
(MeCN)
2
PdCl
2
, L,
Cs
2
CO
3
, CH
3
CN
OMe
OMe
PCy
2
i
-Pr
L =
Ph
Cl
i
-Pr
2
3
2
8
2.385
i
-Pr
Scheme 2.119
Ph
(MeCN)
2
PdCl
2
, L,
Cs
2
CO
3
, CH
3
CN
MeO
2
C
MeO
2
C
OMe
Ph
OTs
MeO
2
C
2.387
MeO
2
C
2.386
Scheme 2.120
After desilylation of the other alkyne, a third Sonogashira reaction added an electron-poor alkene to give
a tetraene
2.378
, setting the stage for an intramolecular Diels-Alder reaction. Another approach to the
ene-diynes using the Sonogashira reaction can be found in Scheme 7.8.
Tri-
t
-butyl phosphine can be more effective in the coupling of reluctant aryl bromides (Scheme 2.118).
139
Bulky electron-rich biaryl phosphine ligands, such as
2.385
, can also promote the Sonogashira reaction of
“difficult” aryl chlorides (Scheme 2.119).
140
Interestingly, in this case, the presence of copper(I) salts inhibited
the reaction, and the copper-free version provided better yields. Aryl tosylates, easily prepared from phenols,
also couple under these conditions (Scheme 2.120).
