Chemistry Reference
In-Depth Information
HO
O
H
Cl
Cl
Sn
Cl
Cl
LBA
4
O
OH
LBA
4
(10 mol %)
Na
2
CO
3
(20 mol %)
Toluene, -78°C
O
R
1
B
+
O
R
R
H
R
2
R
1
R
2
Up to 99% yield
Up to 80% ee
O
OH
LBA
4
(10 mol %)
OH
TBSO
H
Na
2
CO
3
(20 mol %)
Toluene, -78°C, 24 h
TBSO
TBSO
anti-syn
syn-syn
O
SnCl
4
LBA
4
(11 mol %)
alone
66
:
34
(81% yield)
B
O
95
:
5 (77% yield)
ent
-LBA
4
(11 mol %)
68
:
32 (50% yield)
Scheme 3.26.
PA
1a
: X = H
PA
1b
: X = Ph
PA
1c
: X = 4-NO
2
C
6
H
4
PA
1d
: X = 4-
PA
1h
: X = 1-naphthyl
PA
1i
: X = 2,4,6-(
i
-Pr)
3
C
6
H
3
PA
1j
: X = 9-anthryl
PA
1k
: X = 9-phenanthryl
PA
1l
: X = biphenyl
PA
1m
: X = 2-naphthyl
PA
1n:
X = SiPh
3
X
O
O
OH
-naph-C
6
H
4
PA
1e
: X = 4-ClC
6
H
4
PA
1f
: X = 3,5-(CF
3
)
2
C
6
H
3
PA
1g
: X = 3,5-dimesitylphenyl
β
P
O
X
Figure 3.5.
Chiral phosphoric acids.
optically pure BINOL carrying bulky 3,3′-substituents as a novel class of chiral Brønsted
acid catalysts.
Since these seminal papers, many research groups have expanded the application of
these catalysts to various organic transformations [49]. It was found that phosphoric
acids are bifunctional catalysts bearing both a Brønsted acidic site and a Lewis basic site
and that 3,3′-substituents play a crucial role in attaining high stereoinduction as well as
high reactivity by controlling structural and electronic properties.
3.5.1. Nucleophilic Additions of Aldimines
Akiyama et al. fi rst reported that chiral phosphoric acids effectively catalyzed Mannich-
type reaction of imines with ketene silyl acetals (Scheme 3.27) [52]. Although phosphoric
acid PA
1a
was not effective as a chiral catalyst, introduction of aryl substituents at
