Chemistry Reference
In-Depth Information
1.
Pd(OAc)
2
, PPh
3
2. Boc
2
O, Et
3
N
3.
NH
2
Grubbs I
Ti(O
i
-Pr)
4
CO
2
H
O
AcO
OH
DCC, DMAP
N
O
t
-Boc
8.369
1. CF
3
CO
2
H
2. HCHO, NaBH
4
3. H
2
, (Ph
3
P)
3
RhC
l
N
O
O
N
O
O
H
H
H
H
t
-Boc
Me
8.370
8.371
Scheme 8.102
RCM
RCM
initiate here
8.372
Scheme 8.103
1. H
2
, (Ph
3
P)
3
RhCl
2. H
2
, Pd(OH)
2
Bn
H
Bn
Mo-catalyst
N
N
N
Me
Me
8.374
e.r. = 93.5:6.5
8.373
8.375
Ph
t
-Bu
Mo
Mo-catalyst
=
O
O
8.376
t
-Bu
Scheme 8.104
A Schrock-type molybdenum catalyst
8.376
with an axially chiral biaryloxide ligand was employed in a
synthesis of (
R
)-coniine
8.375
(Scheme 8.104).
115
It is notable that the molybdenum catalyst tolerates the
basic nitrogen atom in the substrate
8.373
.
A modified catalyst
8.380
, in which the molybdenum is also a stereogenic centre was employed in a
synthesis of quebrachamine
8.379
(Scheme 8.105).
116
An alternative scenario is the enantioselective ROM-RCM combination in which the initiating carbene
has a choice between two enantiotopic methyne groups in a C2-symmetrical alkene (Scheme 8.106). Such
