Chemistry Reference
In-Depth Information
O
O
N
N
N
L-9
(10 mol %)
CuOTf (10 mol %)
H
2
O
35°C, 2 days
H
HN
N
*
Ph
Ph
Ph
H
Ph
68% yield
91% ee
Scheme 1.22.
L-10
(10 mol %)
Cu(OAc)
2
•H
2
O (10 mol %)
Na-ascorbate (20 mol %)
OO
OO
+
Ph
O
O
O
O
H
2
O, 0°C, 14 h
(10 equiv)
R
R
Ph
Ph
R = aromatic, aliphatic
6 examples
HN
N
64-94% yield
82-97% ee
N
O
PPh
2
L-10
Scheme 1.23.
1.2.3.2. DNA-Based Asymmetric Catalysis in Water
The DNA - based asymmetric
Diels-Alder reaction proceeds in water. There are three key structural features: a DNA-
intercalating moiety, a spacer component, and a metal-binding group, which intimately
anchored the metal complexes to DNA to use its chiral information. The substituent
and the spacer length of the ligand are crucial for both of enantioselectivity and the
enantiopreference [28] .
1.2.3.3. Pauson-Khand-Type Reaction in Water
The chiral ligand BINAP [2,2′ - bis(di -
p - tolylphosphino) - 1,1 ′ - binaphthyl] together with [RhCl(COD)]
2
/TPPTS (trisodium salt
of 3,3′ ,3 ″-phosphanetriyl benzene sulfonic acid) is effective for the asymmetric Pauson-
Khand-type reaction in water. Formaldehyde can be used as a source of carbon monox-
ide directly in water (Scheme 1.24 ) [29] .
Rhodium-catalyzed asymmetric Pauson-Khand-type reactions in water work well in
the presence of a chiral atropisomeric dipyridyldiphosphane ligand (
S
- P - Phos), trans-
forming various enynes into the corresponding bicyclic cyclopentenones in good yields
and ees (up to 95% ee) (Scheme 1.25 ) [30] .
