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O
Br
22 examples
45-90% yield
[(Cinnamyl)PdCl]
2
(2 mol%)
PPh
3
CO
R''
R''
R'
R'
Scheme 10.16 Palladium-catalysed carbonylative Heck reaction of aryl bromides.
L
X
Ph
Pd
X
Ph
Pd
L
Ph
Ph
Ph
PhX
NEt
3
Ph
X
X
Ph
O
Ph
Pd
L
H
Pd
CO
L
Ph
NEt
3
.
HX
CO
X
L
Ph
Pd
L
X
Pd
O
CO
Ph
X
O
X
O
Ph
L
Pd
Pd
L
Ph
Ph
Ph
X=I,Br,Cl,OTf
Scheme 10.17 General reaction mechanism for the carbonylative Heck reaction and
non-carbonylative Heck reaction.
mechanism was studied step by step. The results fitted well with DFT
calculations.
Most recently, the synthesis of chalcones from aryl bromides in the
presence of PPh
3
as ligand was achieved (Scheme 10.16).
21
Based on both
experimental results and DFT calculations, the proposed mechanism for this
reaction is shown in Scheme 10.17. It starts with oxidative addition of ArX to
the Pd
0
center to form the corresponding aryl-palladium complex, followed
by the coordination and insertion of CO to produce the respective acyl-
palladium complex. After coordination, addition and elimination processes,
the desired chalcone is obtained. With the help of base, Pd
0
is formed again
and the next reaction cycle can start.
10.3 Carbonylative Sonogashira Reactions
The Sonogashira reaction is generally known as a coupling reaction of
terminal alkynes with aryl or vinyl halides. This reaction was first reported by
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