The protocol of reduction of complex 81 was also efficiently applied to indoles
H63–H69 (Scheme 59) as well as to a range of diverse heterocycles H58 (Scheme
60), H72 (Scheme 61) and H90–H92 (Scheme 62). These substrates were all
reduced with excellent yield although quinoxaline H90 was isolated as its mono
N-formyl derivative [212].
2-Methylquinoline was quantitatively reduced to 2-methyl-1,2,3,4tetrahydroquinoline within 24 h at room temperature using 0.1 mol% loading of
Ir
Cp*
N
Cl
OMe
81
HN
Ir
NTs
83
Ph
Ph
H 2 N
Ir
Cp*
N
Cl
82
[Cp*IrCl 2 ] 2
+
H 2 N
HN
Ph
Ph
S
O
O
CF 3
CF 3
I
Cl
Cp*
Scheme 56 Iridium complexes for the reduction of N-heterocycles
H
2-Me
3-Me
4-Me
2-Ph
H1
H2
H3
H4
H5
R
N
R
6-Me
6-OMe
6-OBn
6-OAllyl
6-NHBoc
6-COOH
6-COOMe
H6
H7
H8
H9
H10
H11
H12
R
N
R
Me
6-CONEt 2
6-F
6-Cl
6-Br
7-F
8-Cl
6-CF 3
H13
H14
H15
H16
H17
H18
H19
R
N
R
Me
Cl
H20
H21
R
N
Me
Ph
H22
N
Me
H23
N
Me
H24
Me
Me
N
Me
H25
O
N
Me
H26
S
N
Me
H27
N
Me
H28
B
O
O
N
Me
Me
Me
Me
Scheme 57 Quinolines
Recent Advances in Iridium-Catalysed Transfer Hydrogenation Reactions
127