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

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548 NITRONATES<br />

3.4.3.1.2. Silyl <strong>Nitronates</strong> The characteristic features of the behavior of SENAs<br />

<strong>in</strong> [3 + 2]-addition reactions (75, 133, 175–177, 185, 186, 189, 201a, 203, 205,<br />

206, 216, 355–362c) are virtually identical to those of acyclic alkyl nitronates<br />

considered <strong>in</strong> the previous section. As mentioned above, m<strong>in</strong>or but more reactive<br />

Z -tautomers of SENAs derived from primary AN can be detected by cycloaddition<br />

reactions (see Section 3.3.4.1 <strong>and</strong> Scheme 3.128).<br />

Chart 3.12 shows the most characteristic oleÞns <strong>in</strong>volved <strong>in</strong> [3 + 2]-addition<br />

reactions with SENAs.<br />

Here two facts can be mentioned. For example, cycloaddition of nitronate<br />

(MeO2C)CH=N(O)OSiMe3 to ethylene was observed (203), whereas its<br />

O-methyl analog does not react with ethylene. It is hardly probable that this<br />

fact is due to the high reactivity of the silyl nitronate. More likely, the negative<br />

result for alkyl nitronate is attributed to low stability of this derivative.<br />

Second, fullerene C60 was <strong>in</strong>volved <strong>in</strong> the st<strong>and</strong>ard reaction with very reactive<br />

nitronate CH2=N(O)OSiMe3 (362b).<br />

Cycloaddition of SENAs to sulfonyl-substituted allene (362a) or v<strong>in</strong>yl phosphonates<br />

(362c) is worthy of notice.<br />

3.4.3.1.3. Five-membered Cyclic <strong>Nitronates</strong> In spite of the fact that Þvemembered<br />

cyclic nitronates are known for more than a hundred years <strong>and</strong> are<br />

classiÞed as the most stable representative of this class of compounds, their<br />

Ref.203<br />

Ph<br />

Bu n<br />

Ref.<br />

175–177<br />

186 203<br />

205 206<br />

75<br />

CF 3 Ref.360<br />

Br<br />

Ref.133<br />

CF2CF2Br Ref.360<br />

Br<br />

CO 2Alk<br />

Fullerene C60<br />

Ref.359<br />

CO 2Alk<br />

Si Ref.361<br />

O<br />

Ref.189<br />

Ref.362b<br />

Me<br />

Ref.<br />

175<br />

201a<br />

203<br />

Ref.358<br />

NO 2<br />

Ref.<br />

205<br />

206<br />

185<br />

CO 2Alk<br />

Ref.<br />

216<br />

355<br />

Ref.133<br />

P(O)(OAlk) 3 Ref.362c<br />

COR<br />

Chart 3.12 [3 + 2]Reactivity of silyl nitronates.<br />

Ref.<br />

201a<br />

186<br />

206<br />

CO2Alk Ref.133<br />

Me<br />

•<br />

Ref.<br />

133<br />

356<br />

357<br />

SO 2Ph<br />

Ref.75<br />

Ref.362a<br />

Ref.359<br />

CO2Ac

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