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

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160 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

Intramolecular variations of a series of bifunctional derivatives lead to the<br />

formation of cyclic nitrones. Many pyrrol<strong>in</strong>e N-oxide derivatives were obta<strong>in</strong>ed<br />

<strong>in</strong> the course of <strong>in</strong>tramolecular <strong>in</strong>teraction <strong>in</strong> situ between carbonyl <strong>and</strong> hydroxylam<strong>in</strong>e<br />

groups, result<strong>in</strong>g from the reduction of a γ-nitro group (Scheme 2.31)<br />

(Fig. 2.8) (238–253).<br />

The same approach was implemented <strong>in</strong> the synthesis of isoqu<strong>in</strong>ol<strong>in</strong>e- (a–f)<br />

<strong>and</strong> iso<strong>in</strong>dol<strong>in</strong>e-(g–i) nitrones (Fig. 2.9) (254).<br />

R = H, Ph<br />

R 2<br />

R 3<br />

Me<br />

−O Me<br />

N<br />

+<br />

N Ph<br />

Me<br />

N<br />

N<br />

Me<br />

R = Me, R = H<br />

R<br />

Me<br />

Me<br />

Me<br />

Me<br />

Ref. 240<br />

Me<br />

N<br />

R<br />

NO2<br />

R<br />

O<br />

O<br />

R 1<br />

Zn, H +<br />

Scheme 2.31<br />

Me<br />

R = H, Ph<br />

Me<br />

N<br />

Me<br />

Ref. 238 Ref. 238<br />

Ref. 241<br />

+<br />

−<br />

N<br />

O −<br />

H 3C<br />

H3C<br />

Me<br />

N<br />

O −<br />

N<br />

R<br />

R 2<br />

R 3<br />

Ph<br />

N<br />

Me<br />

+<br />

N<br />

− O<br />

MeO<br />

Ph<br />

Me Ph<br />

R 1<br />

Me<br />

CF3 R N 2<br />

+ +<br />

O −<br />

+<br />

+ +<br />

EtO 2C<br />

N<br />

O −<br />

OMe<br />

O −<br />

Ref. 242 Ref. 243<br />

Fig. 2.8<br />

Ref. 240<br />

+<br />

N<br />

Me<br />

Ref. 239<br />

N<br />

O −<br />

Ph<br />

R 1<br />

Ph<br />

Me<br />

Ph

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