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

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

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208 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

O<br />

−<br />

+<br />

N<br />

(CH 2)n<br />

EtO 2C<br />

EtO 2C<br />

(CH2)n<br />

EtO2C<br />

( )n<br />

N<br />

O −<br />

n = 2, 3<br />

hn<br />

N<br />

+<br />

N<br />

AR<br />

O<br />

hv<br />

2 h<br />

Ph<br />

Ph<br />

Ph<br />

O M<br />

O<br />

N<br />

+<br />

O<br />

N<br />

(45%) (20%) (30%)<br />

Scheme 2.89<br />

EtO 2C<br />

( )n<br />

N<br />

EtO 2C O M<br />

( )n<br />

Scheme 2.90<br />

Ph<br />

N Ph<br />

+<br />

+<br />

EtO 2C<br />

O<br />

O N<br />

( )n<br />

N<br />

H<br />

M = Fe, Sn or Cu<br />

observed destruction <strong>in</strong> the presence of oxygen is very likely due to photooxidation<br />

(462).<br />

Experimental evidence of the formation of <strong>in</strong>termediate peroxide moieties<br />

<strong>in</strong> photo-oxidation of nitrones has been provided (463). Oxidation with s<strong>in</strong>glet<br />

oxygen was observed <strong>in</strong> the photoirradiation of DMPO (464).<br />

SpeciÞc regularities of nitrone rearrangements have been studied under photoirradiation<br />

at various conditions (<strong>in</strong> solvent, <strong>in</strong> polymeric matrixes, <strong>and</strong> <strong>in</strong> Þlms<br />

Ph

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