Topics in Current Chemistry (2019) 377:37
1 3
the authors obtained an array of 1,4-dicarbonyl products in good to excellent
enantioselectivities (Scheme 11).
In 2016, Melchiorre et al. achieved the asymmetric construction of quaternary
carbons enabled by the combination of photoredox and iminium catalysis [14].
The carbon radicals were generated via oxidation by the excited photocatalyst
tetrabutylammonium decatungstate (TBADT) or PC-7. The key to their success
is the design of carbazole-containing catalyst OC-10, which acts as a bifunctional catalyst for generating a chiral iminium ion intermediate and facilitating
intramolecular reduction (Scheme 12).
+
N
N
N
N
N
N
Ru
PC-1
(Cl
- ) 2
R
3
R
4
O
H
OC-8 (20 mol%)
PC-1•6H 2 O (3 mol%)
m-NO 2 C 6 H 4 COOH (40 mol%)
Co(dmgH)Cl 2 (8 mol%)
0.5 W blue LEDs, -10 °C
up to 91% yield and 98% ee
N
R
3
R
4
O
+
N
NH 2
n-Pr
n-Pr
23
24
25
OC-8
R
1
R
2
N
H
• HOTf
Co(dmgH)Cl 2
R
1
R
2
Co
Cl
Cl
N
N
Me
Me
O
N
N
Me
Me
O
O O
H
H
N
Ar
N
N
H
H
Scheme 10 Catalytic asymmetric CDC reactions of amines and ketones
R
1
OH
O
O
R
2
R
1
H
O
O
R
2
OC-9 (20 mol%)
PC-6 (5 mol%)
CH 3 CN, -20 °C, N 2
white LEDs, 60 h
up to 99% yield and 80% ee
+
N
H
F
F
OTDS
Ar
Ar
Ar = 3,5-(CF 3 ) 2 C 6 H 3
TDS = thexyldimethylsilyl
OC-9
26
27
28
H
O
+
N
N
N
N
N
N
N
N
N
N
N
N
Ru
PC-6
(PF 6
-
) 2
Scheme 11 Catalytic asymmetric hydroacylation of enals
Reprinted from the journal
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