Chemistry Reference
In-Depth Information
n
-Bu
MeO
2
C
MeO
2
C
n
-Bu
11.47
major product,
ligand = DPPF
[Ir(cod)Cl]
2
, ligand
MeO
2
C
MeO
2
C
11.46
MeO
2
C
MeO
2
C
n
-Bu
11.48
major product,
ligand = DPPE
Scheme 11.19
2] cyclotrimerization can
even tolerate three boron atoms to give triborylated arenes, capable of selective Suzuki coupling reactions
(Scheme 11.20).
38
All three alkynes can be incorporated into a single molecule, making the reaction entirely intramolecular.
This has been used in a synthesis of Cryptoacetalide
11.60
(Scheme 11.21).
39
The triyne
11.58
was constructed
by coupling a diyne
11.56
containing a carboxylic acid with an alkynol
11.57
. A ruthenium catalyst was
found to be most effective for the cyclotrimerization, combined with microwave heating. The synthesis was
completed by deprotection and free-radical spiroketal formation.
The cyclotrimerization can also be used to formunusual and challenging aromatic systems, including biaryls
and helicenes (Scheme 11.22).
40
The triyne substrate
11.63
was constructed by a Sonogashira reaction of
Boron substituents are tolerated by the reaction conditions. The [2
+
2
+
pinB
HN
(COD)
2
RhBF
4
,
To l - B I N A P
B
Bpin
H
+
HN
NH
Bpin
B
pinB
1
.
4
1
.
0
11.51
OMe
CF
3
1.
p
-MeOC
6
H
4
I, dppfPdCl
2
, K
2
CO
3
2. H
3
O
+
3.
p
-F
3
C
6
H
4
I, dppfPdCl
2
, K
2
CO
3
O
Bpin =
B
O
11.52
OMe
Scheme 11.20
