Chemistry Reference
In-Depth Information
TABLE 10.2. Several Heterocyclic Olefi ns Effi ciently Hydroformylated Using Rh - ( R , S ) -
BINAPHOS System
Substrate
Product
% ee
a
X = O; 68 (
R
)
X = NBoc; 73(
R
)
X = NAc; 66 (
CHO
X
*
−
)
X
CHO
R = H; 76 (
)
R = Me; 70 (
R
)
−
*
OO
R
R
OO
R
R
CHO
38 (
S
)
O
*
O
97 (
S
)
*
CHO
Boc
Boc
a
Enantiomeric excess.
H
2
/CO
OHC
*
[M-Chiral Catalysts]
Scheme 10.7.
hydroformylation of 2,5-dihydrofuran is opposite to that which is obtained from the
hydroformylation of 2,3-dihydrofuran with the same catalyst [37].
Recently, the previously mentioned diphosphite ligands
10a
,
14a
,
15a
,
17a
, and
20a
(Figs. 10.1 and 10.3) were successfully applied for the fi rst time in the Rh-catalyzed
hydroformylation of 2,3- and 2,5-dihydrofuran. The results indicated that the backbone
of the ligand is crucial to suppressing isomerization and obtaining high ee's. High enan-
tioselectivities for both substrates have therefore been obtained by using the furanoside
diphosphite ligand
20a
(75% ee). Note that both enantiomers of tetrahydrofuran-3-
carbaldehyde
A
can be synthesized by using the same ligand
20a
by simple substrate
change [38] .
10.2.7. Rhodium - Catalyzed Asymmetric Hydroformylation of Bicyclic Olefi ns
The asymmetric hydroformylation of bicyclic olefi ns such as norbornene has received
little attention (Scheme 10.7 ).
