Chemistry Reference
In-Depth Information
MeO
2
C
MeO
2
C
MeO
2
C
MeO
2
C
Ph
3
PAuCl, AgSbF
6
Z
not involved
6.268
6.269
MeO
2
C
MeO
2
C
Ph
3
PAuCl,
AgSbF
6
Ph
3
PAu
MeO
2
C
MeO
2
C
MeO
2
C
MeO
2
C
E
H
H
6
7
6
2
7
Scheme 6.109
Ts
Ts
Ts
N
N
N
O
O
PtCl
2
n
-Bu
3
SnH, Pd(0)
n
-Pr
n
-Pr
O
n
-Pr
6.272
6
2
6
.
4
Ts
N
1. LiAlH
4
2. PhOC(S)Cl, py
3.
n
-Bu
3
SnH
N
H
2
N(CH
2
)
3
NH K
n
-Bu
n
-Bu
6.275
6.276
MeO
N
N
n
-Bu
NH
6.277
Scheme 6.110
N
-tosyl pyrrole
6.275
was converted to a pyrrole
6.276
by treatment with a strong base, and thence to the
natural product
6.277
.
Gold-catalysed ene-yne cyclization has been employed in two closely related and simultaneous syntheses
of englerin A
6.278
, a sesquiterpene that has shown anti-tumour activity (Scheme 6.111).
123
Both syntheses
relied upon the intramolecular nucleophilic trapping of the cyclopropyl carbene intermediate
6.280
by a
ketone nucleophile, followed by counterattack of the anionic
1
-vinyl gold species onto the oxonium ion
6.281
formed in this way, to form the skeleton of the molecule, but differed in their approach to the other
functionality.
