donor ligands gave full conversion of nitroarenes but variable aniline yields
(53–98%). The bidentate nitrogen ligand 1,10-phenanthroline (L11) showed the
highest yield in aniline [185].
A monitoring experiment and a series of controlled experiments employing
nitrobenzene as the substrate showed that the transformation proceeds via
phenylhydroxylamine and azobenzene intermediates. However, after 15 h of treatment under the reaction conditions above indicated, using [IrCl(COD)] 2 /L11 as the
catalyst, a series of nitroarenes (E1-E3, E5-E14, E19-E24, E26-E30, Scheme 43)
were completely reduced to the corresponding anilines in 70–98% yield.
A phosphine bisbenzothienyl iridium(III) complex (73, Scheme 44) was applied
to the TH of ketones. Under the best conditions found, namely, 2 mol% of 73, 1.5
equiv. of tBuOH, toluene as the reaction solvent, at 110
C, several methyl aryl
ketones (B1, B2, B10, B156, B20, B27, Scheme 4) were hydrogenated. Yields of the
corresponding alcohol up to 68% were obtained [186].
A range of ketones was reduced to the corresponding alcohols by [IrCl(COD)] 2 /
chiral amine ligand mixtures. The amino ligands employed are collected in Scheme
45.
The best reaction conditions were as follows: a 1/2 metal/ligand ratio, a 1/1
mixture of formic acid and sodium formate (pH 3.5 at the beginning of the reaction)
and water/methanol (1/1) as a solvent. After 1 h of treatment at RT under argon
atmosphere, the reducing agent was added and the solution heated at 70
C. Under
these conditions, moderate to high isolated yields (41–87%) and e.r.’s (57.5/
42.5–99.5/0.5) were obtained for the reduction of a range of methyl aryl ketones
(B1, B2, B8, B12, B18, B21-B25, B27, B34) [187].
NO 2
NO 2
N
S
O
O
NH 2
R
H
2-Me
3-Me
4-Me
4-Et
4-OMe
2-NH 2
3-NH 2
E1
E2
E3
E4
E5
E6
E7
E8
R
4-NH 2
2-Cl
3-Cl
4-Cl
4-Br
3-CF 3
4-COMe
4-CONH 2
E9
B10
B11
B12
B13
B14
B15
B16
R
4-COOEt
4-CN
3-NO 2
2,3-Me 2
3-Me,4-Cl
3-Br,4-Me
2-Cl,5-OMe
3,5-Cl 2
B17
B18
B19
B20
B21
B22
B23
B24
NO 2
E25
E26
E27
E28
E29
E30
NO 2
N
NO 2
N
H
NO 2
N
Me
NO 2
R
Scheme 43 Nitroarenes
114
M. Pilar Lamata et al.
(53–98%). The bidentate nitrogen ligand 1,10-phenanthroline (L11) showed the
highest yield in aniline [185].
A monitoring experiment and a series of controlled experiments employing
nitrobenzene as the substrate showed that the transformation proceeds via
phenylhydroxylamine and azobenzene intermediates. However, after 15 h of treatment under the reaction conditions above indicated, using [IrCl(COD)] 2 /L11 as the
catalyst, a series of nitroarenes (E1-E3, E5-E14, E19-E24, E26-E30, Scheme 43)
were completely reduced to the corresponding anilines in 70–98% yield.
A phosphine bisbenzothienyl iridium(III) complex (73, Scheme 44) was applied
to the TH of ketones. Under the best conditions found, namely, 2 mol% of 73, 1.5
equiv. of tBuOH, toluene as the reaction solvent, at 110
C, several methyl aryl
ketones (B1, B2, B10, B156, B20, B27, Scheme 4) were hydrogenated. Yields of the
corresponding alcohol up to 68% were obtained [186].
A range of ketones was reduced to the corresponding alcohols by [IrCl(COD)] 2 /
chiral amine ligand mixtures. The amino ligands employed are collected in Scheme
45.
The best reaction conditions were as follows: a 1/2 metal/ligand ratio, a 1/1
mixture of formic acid and sodium formate (pH 3.5 at the beginning of the reaction)
and water/methanol (1/1) as a solvent. After 1 h of treatment at RT under argon
atmosphere, the reducing agent was added and the solution heated at 70
C. Under
these conditions, moderate to high isolated yields (41–87%) and e.r.’s (57.5/
42.5–99.5/0.5) were obtained for the reduction of a range of methyl aryl ketones
(B1, B2, B8, B12, B18, B21-B25, B27, B34) [187].
NO 2
NO 2
N
S
O
O
NH 2
R
H
2-Me
3-Me
4-Me
4-Et
4-OMe
2-NH 2
3-NH 2
E1
E2
E3
E4
E5
E6
E7
E8
R
4-NH 2
2-Cl
3-Cl
4-Cl
4-Br
3-CF 3
4-COMe
4-CONH 2
E9
B10
B11
B12
B13
B14
B15
B16
R
4-COOEt
4-CN
3-NO 2
2,3-Me 2
3-Me,4-Cl
3-Br,4-Me
2-Cl,5-OMe
3,5-Cl 2
B17
B18
B19
B20
B21
B22
B23
B24
NO 2
E25
E26
E27
E28
E29
E30
NO 2
N
NO 2
N
H
NO 2
N
Me
NO 2
R
Scheme 43 Nitroarenes
114
M. Pilar Lamata et al.