Chemistry Reference
In-Depth Information
Pd(0), PCy
3
,
NaO
t
-Bu
O
6.151
>20:1 dr
Br
HO
6.147
Pd(0),
dppbz,
NaO
t
-Bu
O
6.152
15:1 dr
Scheme 6.50
Br
Pd(0), dppbz,
NaO
t
-Bu
HO
Pd(0), PCy
3
,
NaO
t
-Bu
6.147
Ph
2
P
Cy
3
P
O
Pd
Pd
PPh
2
6.153
6.155
O
insertion
anti-attack
PdL
Pd
O
Cy
3
P
O
6.154
6.156
reductive
elimination
reductive
elimination
O
O
6.151
6.152
Scheme 6.51
coordination of both the alkene and the alkoxide to palladium after oxidative addition, giving a complex
6.153
. Insertion of the alkene into the C-Pd bond, gives an alkoxy palladium complex
6.154
, which undergoes
reductive elimination to form the C-O bond. These are all
syn
processes, so isomer
6.151
is formed. On the
other hand, the bidentate phosphine, dppbz
1.31
, may block O-Pd coordination, so that complex
6.155
is
formed and only
anti
-attack of the alkoxide can occur, leading to the other diastereoisomer
6.152
.
