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

442 NITRONATES
It should be noted that in the latter case, stereoisomers of O-nitronates were
isolated and identiÞed (20).
In reactions of certain alkyl halides with salts of polynitromethanes, C-alkylation
can also be diminished and target O-nitronates can be prepared in satisfactory
yields (21, 22) (Scheme 3.8, Eq. 2). Of special note is the study by Kim
and Adolph (22), who prepared numerous nitronates by alkylation of salts of
dinitromethane, cyanodinitromethane, and trinitromethane with a representative
series of α-chloro-substituted (including functionalized) ethers.
Very interesting results were obtained by Russian researchers in alkylation of
the Ag salt of trinitromethane with alkyl halides (Scheme 3.9) (23–25).
Both C-alkylation products and the corresponding O-alkyl nitronates were
detected in the reaction mixture prepared by the reactions of above mentioned
salt with primary alkyl halides (Scheme 3.9, Eq. 1). However, isoxazolidines
(1) are the main identiÞed products of the reactions with secondary or tertiary
alkyl halides. The possible pathway of their formation is shown in Scheme 3.9.
Here, the key event is generation of the corresponding oleÞns from alkyl halides.
These oleÞns can be trapped with O-nitronates that are simultaneously formed in
[3 + 2]-cycloaddition reactions. Presumably, these oleÞns are generated through
deprotonation of stabilized cationic intermediates (see Scheme 3.9).
In this manner, the Ag salt of trinitromethane is involved in cascade reactions
with branched alkyl halides to give unexpected products.
Equally interesting processes occur in the reactions of tetranitromethane and
some of its derivatives with oleÞns (Scheme 3.10).
HC(NO 2) 3
Ag[C(NO 2) 3] RCH 2Hal
R
−AgHal
R′′
Hal
R′
C(NO −
2) 3 + R
RCH 2C(NO 2) 3 + (NO2) 2C N
+
R′
Scheme 3.9
−H +
R′′
R
O
OCH 2R
O
(NO2) 2C N R′′
O
R′
R′′
R′
R
R′
R′′
N
O O
1
(1)
R′
R′′
R
R