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

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294 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

products of <strong>in</strong>itial nucleophilic substitution (431) were obta<strong>in</strong>ed. They were readily<br />

transformed <strong>in</strong>to compounds (213b) shown <strong>in</strong> Scheme 2.204 (539, 540).<br />

The reactions of α-bromoalkyl nitrones (298) with secondary am<strong>in</strong>es lead<br />

<strong>in</strong>itially to α-dialkylam<strong>in</strong>o derivatives (432), which on heat<strong>in</strong>g, give aldehydes<br />

<strong>and</strong> ketones (75a,b) <strong>in</strong> high yield (Scheme 2.205) (540).<br />

H<br />

H<br />

NR<br />

O<br />

N<br />

R 2<br />

N<br />

R 1 = H<br />

R 1 BrHC<br />

N<br />

O<br />

+<br />

N<br />

R NH 2 R NH2<br />

R 2<br />

R 1 = H (a), CH 3 (b);<br />

R 2 = O , OH, CH 3, NO, NO 2<br />

R = Me, Bu t , Pr i<br />

R 1 = CH 3<br />

NHR<br />

−<br />

H3C<br />

CH O<br />

+<br />

N<br />

213a 298 a,b 431<br />

N<br />

R 2<br />

N<br />

R2NH<br />

R1 r.t.<br />

= H<br />

−<br />

Scheme 2.204<br />

R 1 BrHC<br />

N<br />

O<br />

+<br />

N<br />

R 2<br />

R 2NH<br />

R 1 = CH3<br />

R 1 = H (a), CH3 (b);<br />

R 2 = O , OH, CH3, NO, NO2<br />

R = Me, Et<br />

H 3C<br />

H 3C<br />

R<br />

−H 2O<br />

N<br />

O<br />

N<br />

R 2<br />

N<br />

R 2<br />

N<br />

213b<br />

R<br />

H3C CH<br />

NR<br />

−<br />

O<br />

+<br />

N<br />

75a 298 a,b 432<br />

−<br />

Scheme 2.205<br />

N<br />

R 2<br />

Δ<br />

N<br />

R 2<br />

75b<br />

N

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