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

Bn
REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 337
O Me
N
N
H
HX
O
R 2
R 2
R 1 O
O
S
N
H
HX
R 1 = H, R 2 = H
R 1 = Me, R 2 = H
R 1 = H, R 2 = MeO
O
H
N
H
(HX)n
R1 R1 R2 R 1 = Me, R 2 = OH
R 1 = Ph, R 2 = OH
R 1 = Me, R 2 = OMe
R1 = H, R2 = N
R1 = H, R2 = N
HX = HCl, HClO 4, TFA
Fig. 2.38 Catalysts used in 1,3-dipolar cycloadditions of nitrones.
H
+
AcO
_
O +
N
Me
Ph
H
H
545
1. One of the
catalysts in Fig. 2.38
DMF/H2O
H
2. NaBH 4
MeOH O N
H
H
AcO
Scheme 2.256
O
+
Me
Major
C
Ar H
Ph
_
O + Ph
N
OH
Δ 100 Reflux dry benzene
° Sealed tube
H
Scheme 2.257
H
546
H
O
O
+
H
H
H
Ar
O N
N Ph
Me
Minor
Ph
OH