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

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R 3<br />

R 4<br />

R 5<br />

R 3<br />

R 4<br />

R 5<br />

Et3N<br />

R 3<br />

R 4<br />

R 5<br />

R 3<br />

R 4<br />

R 2<br />

O N<br />

518<br />

R 5<br />

R 2<br />

O N<br />

A<br />

R 2<br />

O N<br />

516<br />

R 2<br />

O N<br />

R 1<br />

O<br />

Me3SiX/Et3N<br />

R 1<br />

OSiMe3<br />

X<br />

Et3NHX<br />

R 1<br />

Me3Si Nu<br />

Me3SiX + Nu<br />

OSiMe3<br />

Me 3SiNu<br />

R 1<br />

OSiMe3<br />

SILYLATION OF NITRO COMPOUNDS AS A PROCESS 705<br />

Nu – Et3N or MeCN<br />

+<br />

Me3Si2O<br />

Nu<br />

R 3<br />

R 4<br />

R 3<br />

R 4<br />

R 5<br />

R 3<br />

R 4<br />

R 5<br />

R 5<br />

[NuSiMe3] + + X −<br />

R 2<br />

R 1<br />

R 3<br />

R 2<br />

R 1<br />

O N<br />

O N<br />

R5 R4 X +<br />

X<br />

517 517′<br />

R 2<br />

X<br />

R 2<br />

O N<br />

R 1<br />

R 1<br />

R 3<br />

R 4<br />

R 2<br />

R 1<br />

R 3<br />

R 4<br />

R 5<br />

R 3<br />

R 4<br />

R 2<br />

O N<br />

R 2<br />

O N<br />

N<br />

R5 O O N<br />

R5 B B′′ B′<br />

Scheme 3.268<br />

these products were used for the synthesis of the correspond<strong>in</strong>g bromo derivatives<br />

(520) accord<strong>in</strong>g to the procedure described <strong>in</strong> the study (472).<br />

Functionalized oxaz<strong>in</strong>es (521) <strong>and</strong> (522) were synthesized from these key<br />

<strong>in</strong>termediates by the nucleophilic substitution of brom<strong>in</strong>e (<strong>in</strong> 55%–100% yields<br />

based on derivatives (520) or 20%–30% yields based on the start<strong>in</strong>g nitroethane).<br />

Besides, bromo derivatives (520) are convenient start<strong>in</strong>g reagents for the synthesis<br />

of functionalized oxaz<strong>in</strong>es (523) <strong>and</strong> (524).<br />

X<br />

R 1<br />

R 1

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