80
X. Feng et al.
Table 2.39 Direct enantioselective α-amination reactions
X
H
O
R
+
N
N
OR
O
RO
O
X
O
R
HN
N
COOR
COOR
B(C 6 F 5 ) 3
81
82
83
Ph
N
H
CF 3
N
Me
Me
Ph O
84
entry product
yield (%) ee (%)
1
83a
HN
N
COOMe
COOMe
O
85
36
2
83i
HN
N
COOMe
COOMe
O
86
94
3
83j
HN
N
COOMe
COOMe
O
O
87
88
4
83k
HN
N
COOMe
COOMe
O
47
70
5
83l
HN
N
COOEt
COOEt
O
H
78
86
α-C− H bond, the deprotonation was promoted by the hindered amine to form a tight
ionic pair consisting of a boron enolate and an ammonium cation. The ammonium
cation served as hydrogen bond donor to activate dialkyl azodicarboxylates to afford
aminocarbonyl products. It was facile to independently modify the Lewis acid and
Brønsted base for higher reaction efficiency and/or enantioselectivity (Fig. 2.6).
X. Feng et al.
Table 2.39 Direct enantioselective α-amination reactions
X
H
O
R
+
N
N
OR
O
RO
O
X
O
R
HN
N
COOR
COOR
B(C 6 F 5 ) 3
81
82
83
Ph
N
H
CF 3
N
Me
Me
Ph O
84
entry product
yield (%) ee (%)
1
83a
HN
N
COOMe
COOMe
O
85
36
2
83i
HN
N
COOMe
COOMe
O
86
94
3
83j
HN
N
COOMe
COOMe
O
O
87
88
4
83k
HN
N
COOMe
COOMe
O
47
70
5
83l
HN
N
COOEt
COOEt
O
H
78
86
α-C− H bond, the deprotonation was promoted by the hindered amine to form a tight
ionic pair consisting of a boron enolate and an ammonium cation. The ammonium
cation served as hydrogen bond donor to activate dialkyl azodicarboxylates to afford
aminocarbonyl products. It was facile to independently modify the Lewis acid and
Brønsted base for higher reaction efficiency and/or enantioselectivity (Fig. 2.6).