5508
Scheme I
Ph,+.,N Ph
N, ’Ph
-kP
nonconcerted 1,3-sigmatropic rearrangement (e.g., 3 + 5 + 4). Moreover, the cycloadditions are of potential importance in synthesis as a direct route to methylenecyclopentanes.
h - N H w & P h
Ph
5
4
X,
4 + 5 -
+
a
1
Ph N
N
w
6
N
,
p
+
h
TFA
-----*
7
H P
7(or8) 6
+
base
-
+
h
-
excessTFA
N
w
-
-N
