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

R
N
O Cl
367
−O
+
N
Bu t
LDA, THF
−98 °C
N
N
O
R = Li
R = H
O
371
Ph
Cl
O N R
O N
Bu t
N
O
Ph
H
Cl
Li
NITRONE REACTIONS 261
N
O
Cl
Ph
N
O
O
N R
R = Li
R = H
369 370
Scheme 2.159
+
O
N
O N
Bu t
Li
Cl
The reaction of lithiated 2-(1-chloroethyl)-2-oxazolines (367) with nitrones led
to the stereoselective synthesis of oxazolinyl-[1.2] oxazetidines (372a,b) which
are important as precursors of α-hydroxy-β-amino acids (Scheme 2.160) (601).
2.6.6.1.4. Addition of Organometalic Compounds as an EfÞcient Synthetic Method
of Stable Nitroxyl Radicals Nucleophilic additions of organometalic compounds
have been successfully applied to the synthesis of stable nitroxyl radicals. Owing
to structural and reactive variations of organometalic compounds, this reaction
offers great possibilities for the synthesis of different types of nitroxyl radicals
with wide variations of R 1 -R 4 substituents. The resulting hydroxylamines can
be readily oxidized to the corresponding nitroxyl radicals, at mild conditions
(Scheme 2.161) (602).
A wide range of the nitroxyl radicals, presented in Fig. 2.27, have been
obtained by this strategy (603–615).
It was found (616) that the course of the heterogeneous reaction of 1-hydroxy-
5,5- dimethyl-2,4- diphenyl-3-imidazoline-3-oxide with PhLi depends on the
crystalline phase of the starting compound, which can be obtained, predominantly,
in cyclic or open chain tautomeric forms.
Ph
H