Chemistry Reference
In-Depth Information
EtMgCl,
Cp
2
ZrCl
2
OR
OMgCl
OMe
MgCl
MgCl
5.278
5.276
5.277
Et
Et
R = H
R = Me
B(OMe)
3
; H
2
O
2
or O
2
OH
OH
OH
OH
Et
Et
5.280
5.279
Scheme 5.76
5
-4,5,6,7-tetrahydro-1-indenyl, EBTHI) (Scheme 5.77).
90
This
reaction is proposed to proceed by formation of a zirconocycle
5.284
. The zirconacycle is cleaved by the
Grignard reagent, and this is followed by ring opening of the oxygen heterocycle, and regeneration of the
catalytic species
5.287
.
The products are useful building blocks for the synthesis of more complex molecules. Both the diastereos-
elective and the enantioselective reactions were combined in a synthesis of fluviricin B
1
5.288
, an antifungal
and anti-influenza agent (Scheme 5.78).
91
Of the two fragments required for the formation of the macrocycle,
bis-indenyl-based structure (ethylene-1,2-bis(
EtMgCl,
catalyst
Et
pre-catalyst =
ZrCl
2
O
(EBTHI)ZrCl
2
5.283
OH
5.281
5.282
EtMgCl
H
O
H
5.281
Zr
O
5.284
O
EtMgCl
Cl
Zr
Zr
Cl
Zr
H
Et
MgCl
5.287
5.285
5.283
Et
OMgCl
OH
5.282
Zr
H
Et
5.286
Scheme 5.77
