162
product 30 and ruthenium hydride species 31. Finally, species 31 reacted with
AcOH, releasing H 2 gas and regenerating the catalytically active species 32. The
oxidation state of the metal did not change during the whole catalytic reaction
process.
In 2016, Dong’s group reported a rhodium (Rh)-catalyzed H 2 -releasing orthoalkenylation of N-aryl-substituted 7-azaindoles without the need for an oxidant
(Scheme  5.12) [7]. The reaction mechanism is similar to that of the above
Ru-catalyzed ortho-alkenylation reaction [6].
Scheme 5.10 Ruthenium-catalyzed ortho alkenylation of aromatics with alkenes
[RuX n (L)]
+ [X]n
-
[{RuCl 2 (L)} 2 ]
AgCl
AgSbF 6
O
NH
AcOH
Ru
O
NHMe
Ru
O
MeHN
H-Ru-L
H 2
O
HN
C-H
activation
insertion
hydrogen
evolution
25
26
27
32
28
29
30
31
-H
elimination
R
R
R
AcOH
X = SbF 6 , OAc, Cl
n = 1, 2
L = p-cymene
b
Scheme 5.11 A plausible mechanism for the alkenylation of benzene
W. Ai et al.