Chemistry Reference
In-Depth Information
Pd cat
.
RM
R'
X
RR'
MX
Scheme 2.1
L
2
PdX
2
L
4
Pd
reduction
±2L
L
2
Pd
R'X
RR'
2.1
reductive
elimination
oxidative
addition
R'
R'
L
2
Pd
L
2
Pd
R
X
2.3
2.2
MX
RM
transmetallation
Scheme 2.2
L
2
Pd(II)X
2
+
2RM
L
2
Pd(0)
+
R
2
+
2MX
2.1
Scheme 2.3
2.1.1 The Main-Group Metal, M
A wide variety of main group metals, M, have been employed (Scheme 2.4). In terms of the main group metal,
M, reactivity follows electropositivity. When highly electropositive metals such as lithium and magnesium are
employed, transmetallation can be expected to be fast, but problems of low functional-group tolerance as well
as air and moisture sensitivity arise. Less-reactive metals are more often employed: lithium and magnesium
(Kumada or Corriu-Kumada reaction), zinc (Negishi reaction), aluminium, zirconium, tin (Stille coupling),
R
Li
R
Cu
R MgBr
R
SiR"
3
R
ZnBr
R
R'
RAlR
2
R
BR"
2
R
Sn
n
-Bu
3
R
ZrClCp
2
X
R'
; catalyst
Scheme 2.4
