Chemistry Reference
In-Depth Information
TABLE 10.11. Iodine(III)-Mediated, Cyclization of N-p-Methoxyphenyl-Substituted
4-Pentynamides via Alkyne Trifluoroacetoxyamidation
O
PIFA
PMP
R
O
N
N
PMP
TFE, 0°C
O
R
H
586
587
Entry
R
Yield (%)
Entry
R
Yield (%)
1
Ph
62
7
2-Thienyl
74
2
p
-MeOC
6
H
4
84
8
p
-ClC
6
H
4
33
3
o
-MeC
6
H
4
77
9
3-Pyridyl
0
4
m
-MeC
6
H
4
70
10
p
-O
2
NC
6
H
4
0
5
p
-MeC
6
H
4
58
11
Vinyl
0
6
1-Naphthyl
78
12
E
-2-styryl
68
ınguez and
Tellitu have also examined the iodine(III)-mediated 5-
exo-dig
cyclization of
In an extension of their olefin amidohydroxylation methodology, Dom
b
-alky-
(Table 10.11).
209
Treatment of these substrates with PIFA in trifluor-
oethanol leads to the efficient formation of 5-aroylpyrrolidinones
nylamides
586
through alkyne
amidation. This useful transformation has subsequently been employed byWang
et al.
for the diastereoselective preparation of
cis
-2-substituted 5-aroylpyrrolidinones.
210
From a mechanistic perspective, the formation of
587
587
is interpreted as occurring
via the formation and subsequent alkyne addition of aryl nitrenium ion
588
to form
a vinyl cation
589
. Interception of this short-lived intermediate then leads to enol
ester
590
, which is hydrolyzed upon workup to yield the corresponding
PIFA
TFE, 0°C
O
O
Ad
E
PMP
N
N
R
R
H
PhI, TFA
CF
3
CO
2
586
OMe
588
CF
3
CO
2
R
F
3
C
O
O
O
O
Basic
workup
N
N
N
R
O
O
R
OMe
OMe
OMe
589
590
587
SCHEME 10.96.
