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

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394 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

−<br />

F<br />

G<br />

N<br />

O<br />

R<br />

A B<br />

N<br />

Ph<br />

+<br />

O R<br />

N<br />

1 +<br />

R 2<br />

O<br />

N<br />

O<br />

+<br />

−<br />

+<br />

−<br />

Ph<br />

R 3<br />

790 791<br />

v<br />

i ii<br />

+<br />

b<br />

b<br />

E<br />

+<br />

a<br />

R<br />

N<br />

N<br />

N<br />

Scheme 2.327<br />

CO2R<br />

CO 2R<br />

O<br />

−<br />

−<br />

O<br />

R<br />

iv<br />

O Ph<br />

O Ph<br />

H I<br />

Yb(OTf)3<br />

Reaction of nitrones with cyclopropanes<br />

R 1 , R 2 , R 3 : see Fig 2.48<br />

Scheme 2.328<br />

R 1<br />

N<br />

C<br />

iii<br />

*<br />

D<br />

N<br />

N<br />

O R3<br />

R 2<br />

RO 2C CO 2R<br />

In these reactions, nitrones (790) can be formed <strong>in</strong> situ by the reaction of<br />

hydroxylam<strong>in</strong>es (793) with aldehydes (794) (Scheme 2.329) (Fig. 2.48). This<br />

three-component coupl<strong>in</strong>g of (793), (794), <strong>and</strong> (791) allows for the formation of<br />

a diverse array of cycloadducts (792) with excellent diastereoselectivity ( > 95%)<br />

<strong>and</strong> yields (66%–96%) (853).<br />

792<br />

O<br />

N<br />

O<br />

*<br />

R<br />

R

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