Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

MeO2C
Ph
CO2Me
O N O
X 1
X 2
Ph
H
REACTIVITY OF NITRONATES 539
O N X
CO2Me MeO2C
O
3
X
N
CO2Me
O
2
X1 R
CO2Me
1 X
LA
O
147 148 8%–15%
1 = X2 = X3 = H
X1 = Me; X2 = X3 = H
X1 = F; X2 = X3 = H
X1 = Cl; X2 = X3 = H
X1 = Br; X2 = X3 = H
X1 = X3 = H; X2 = Me
X1 = X3 = H; X2 = F, Cl
R1 LA TiCl4, SnCl4, FeCl3, AlCl3, BF3•Et2O = H, COMe, COPh,
CO-C6H4-NO2-p LA
O
+
N
MeO2C
H
H
A
B
OLA
H
H
+
N
O
CO2Me
OLA
Scheme 3.121
CO2Me
X 1
X 1
X 3
+
N
O
H
CO 2Me
O
H
CO2Me
149 44%–81%
X 1 = Me, F, Cl, Br.
O
O
H
CO2Me
149
MeO2C
H
N
N
O
148
H
CO2Me
OR
H
CO2Me
series of 3,5-bis-methoxycarbonylisoxazoline-2 N -oxides (147) (Scheme 3.121)
containing substituted aryl groups at position 4 with different LA.
Depending on the nature of the substituents X 1 ,X 2 , and X 3 , the reactions
produced nitrones (148) (as indole derivatives) or annelated isoxazolines (149).
The authors performed a series of experiments (including one with the use of
a deuterium label) and suggested a mechanistic scheme for the interpretation