Chemistry Reference
In-Depth Information
FIGURE 16.8
Copper(I) dendritic complexes for the catalyzed coupling of pyrazole.
product within 20 h at 80
C, when starting from iodobenzene. When starting from less
reactive bromobenzene, the best catalytic activity was obtained in the presence of the
third-generation dendritic ligand
34-G
3
, phenylpyrazole being obtained in 80% yield
after 20 h at 80
C (Figure 16.8). We have also demonstrated specific advantages for
copper(I) catalysis of the very important O- and N-arylation and vinylation of phenol
and pyrazole using these copper dendritic complexes, for which the highest yields
under the mildest conditions were used [43].
Another example of copper-catalyzed reactions was provided by dendrimers
ended by bisoxazoline ligands attached via “click” reactions, from generation 1 to
generation 3. These macromolecules were evaluated in copper(II)-catalyzed asym-
metric benzoylations, starting from two different diols. Dendrimers
35-G
2
afford good yields and enantioselectivities in both cases, whereas the third generation
has a detrimental influence on the enantioselectivity. The copper(II)-catalysts could
be readily recovered and reused in several cycles (Figure 16.9) [44].
35-G
1
and
FIGURE 16.9
Cu(II) dendritic complexes and their reuse for catalyzed asymmetric
benzoylations.
