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

196 NITRONES: NOVEL STRATEGIES IN SYNTHESIS
R 1
R 2
R
N
R3 O
+
−
+
N
O
−
−
O +
N
R 1
R2 N
R3 −
Route A: X
X O
−e
Route B: H
Route C: X
Route D: −e
Route E: +e
−
− e
+
−
−
R
R 1
R 1
R 2
R 1
R 2
R 1
R 2
+
+
−
−
N
R3 OH
N
R3 O
N
R3 O
Scheme 2.77
+
N
O
O
N
R 1
X
−e, −H
219 220
NNR
Scheme 2.78
XH
−H
X
NuH
−H+
−
+
+
+
R
R 1
R 2
Nu O
N +
N
O
N
R3 X O
obtained hydroxylamine from oxidation, but as a result of the subsequent work
up (neutralization), it is likely to be oxidized to the corresponding SA.
On studying electrochemical properties of 1-hydroxy-3-imidazoline-3-oxides
and their conversion into nitronyl nitroxyl radicals (NNR), the intermediate production
of a nonaromatic radical cation (220) of4H -imidazole-1,3- dioxides
(219) (Scheme 2.78) (101) was suggested.
In the course of electrochemical oxidation (EO) of 4H -imidazole-1,3- dioxides
(219) (Table 2.6) in dry CH2Cl2 at −80 ◦ to −40 ◦ C, RCs (220) wereÞrst detected
(424, 425). Cyclic voltammograms (CVA) correspond to a one-electron reversible
oxidation (219c) toRC(220c) (Fig. 2.16, curve A).
−
R 1