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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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532 NITRONATES<br />

groups present as substituents (41, 237b, 319). Selected details <strong>and</strong> the possible<br />

pathway of this reaction are shown <strong>in</strong> Scheme 3.109.<br />

Five-membered cyclic nitronates can be subjected to aromatization by alkali<br />

(21) or dilute acids (37, 319) (Scheme 3.110).<br />

AlkO2C<br />

R′HNOC<br />

R<br />

R<br />

heat<br />

O N<br />

O N<br />

CO 2Alk<br />

R′NH2<br />

O<br />

CONHR′<br />

O<br />

Base<br />

R′HNOC<br />

O<br />

R′HNOC<br />

R<br />

R<br />

CONHR′<br />

O<br />

R<br />

R′HNOC<br />

HO<br />

−H 2O<br />

O N<br />

CONHR′<br />

R′NH2 – NH3 R – p–MeOC6H4 Ref.319 (33%); Ref.41 (61%);<br />

N<br />

H<br />

R′NH 2 – Bu n NH 2; R – alkyl Ref.237b (50%–65%).<br />

O2N<br />

R<br />

p-MeOC 6H 4<br />

EtOOC<br />

O N<br />

Me<br />

O N<br />

O<br />

CONEt 2<br />

O<br />

Scheme 3.109<br />

2% NaOH, H 2O<br />

55–60°C, 1 h<br />

AcOH dil.<br />

H2SO4 dil.<br />

Me<br />

HCl / Et2O N<br />

EtO2C O<br />

Scheme 3.110<br />

O N<br />

CO 2H H 2O<br />

CONHR′<br />

N<br />

O low yieldRef.21 (1)<br />

(2)

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