loading. Conversions up to 80% were achieved after 24 h of treatment. With 1.0 mol%
precatalyst loading, the same compounds converted N-benzylideneaniline into
N-benzylaniline (17–50%) after 18 h of treatment at 100
C [63].
The dinuclear half-sandwich iridium complexes 6 and 7 having a bridging bis-Nheterocyclic carbene ligand catalysed the TH of methyl aryl (B1, B10), diaryl (B66),
dialkyl (B102, B113) and cyclic (B117, B118) ketones (Scheme 4). Reactions were
carried out in refluxing 2-propanol, under basic conditions (iPrONa, 3 mol%) and at
0.5 mol% of catalyst loading. After several hours, conversions in the range 5–100%
were achieved, the cationic complex 6 being more active than the neutral orthometallated complex 7 [67].
Half-sandwich iridium complexes 8a-c bearing di- and tridentate
bis(2-pyridylimino)isoindolato ligands are catalytically active in the TH of ketones
and imines. In refluxing 2-propanol, with 0.5 equiv. of KOH and at 1 or 5 mol% of
precatalyst loading, ketones B1, B18, B27, B37, B66 and B118 (Scheme 4) were
converted to the corresponding hydrogenated species in good yield. Under similar
conditions, TH of the imines C1 and C14 (Scheme 5) afforded the corresponding
amines in 53 and 16% yield, respectively, after 4 h of reaction [68].
Reduction of acetophenone was carried out at 95
C in 2-propanol and KOH as a
base. At 2 mol% loading of the precatalysts 9a and 9b conversions of 96 and 98%,
respectively, was achieved after 24 h of reaction [69].
The half-sandwich complexes 10–12 (Scheme 2) with monodentate, bidentate
chelating or bidentate bridging ditriazolylidine ligands containing alkyl or ether
linkers of different lengths between the triazolium heterocycles were investigated
as catalyst precursors for the TH of benzophenone. At a substrate/base/catalyst molar
ratio of 100:10:1, in refluxing 2-propanol, yields in the range 30–98% were obtained
Scheme 5 (continued)
78
M. Pilar Lamata et al.
precatalyst loading, the same compounds converted N-benzylideneaniline into
N-benzylaniline (17–50%) after 18 h of treatment at 100
C [63].
The dinuclear half-sandwich iridium complexes 6 and 7 having a bridging bis-Nheterocyclic carbene ligand catalysed the TH of methyl aryl (B1, B10), diaryl (B66),
dialkyl (B102, B113) and cyclic (B117, B118) ketones (Scheme 4). Reactions were
carried out in refluxing 2-propanol, under basic conditions (iPrONa, 3 mol%) and at
0.5 mol% of catalyst loading. After several hours, conversions in the range 5–100%
were achieved, the cationic complex 6 being more active than the neutral orthometallated complex 7 [67].
Half-sandwich iridium complexes 8a-c bearing di- and tridentate
bis(2-pyridylimino)isoindolato ligands are catalytically active in the TH of ketones
and imines. In refluxing 2-propanol, with 0.5 equiv. of KOH and at 1 or 5 mol% of
precatalyst loading, ketones B1, B18, B27, B37, B66 and B118 (Scheme 4) were
converted to the corresponding hydrogenated species in good yield. Under similar
conditions, TH of the imines C1 and C14 (Scheme 5) afforded the corresponding
amines in 53 and 16% yield, respectively, after 4 h of reaction [68].
Reduction of acetophenone was carried out at 95
C in 2-propanol and KOH as a
base. At 2 mol% loading of the precatalysts 9a and 9b conversions of 96 and 98%,
respectively, was achieved after 24 h of reaction [69].
The half-sandwich complexes 10–12 (Scheme 2) with monodentate, bidentate
chelating or bidentate bridging ditriazolylidine ligands containing alkyl or ether
linkers of different lengths between the triazolium heterocycles were investigated
as catalyst precursors for the TH of benzophenone. At a substrate/base/catalyst molar
ratio of 100:10:1, in refluxing 2-propanol, yields in the range 30–98% were obtained
Scheme 5 (continued)
78
M. Pilar Lamata et al.