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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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R<br />

R<br />

O<br />

OAc<br />

19<br />

Mn III<br />

−H +<br />

NO2<br />

Me<br />

Me<br />

R<br />

O<br />

R 2<br />

CAN<br />

Mn(OCOMe) 3<br />

Mn<br />

O<br />

II<br />

MeO 2CCH 2NO 2<br />

Me<br />

Me<br />

A<br />

R 1<br />

EtO2C<br />

EtO2C<br />

N<br />

R 1<br />

O<br />

AcO<br />

20<br />

R 2<br />

R<br />

CO 2Et<br />

Ph<br />

R<br />

O<br />

1. KOH<br />

2. Ce(NH3) 2(NO2) 6<br />

O R 2<br />

N<br />

O<br />

O 18%–81%<br />

5g<br />

N<br />

R<br />

O<br />

R 2<br />

CO 2Me<br />

O<br />

SYNTHESIS OF NITRONATES 453<br />

[O]<br />

−H +<br />

∼35%<br />

Scheme 3.22<br />

NO 2<br />

N<br />

Ph OK<br />

O<br />

CO2Et<br />

Scheme 3.23<br />

R 1<br />

O<br />

N<br />

O<br />

R 1<br />

R = Ph,<br />

Z<br />

X<br />

X = CH, N; Z = H, Cl, NO2<br />

R = AcO<br />

Ph<br />

5h<br />

EtO2C<br />

EtO2C<br />

O<br />

N<br />

O<br />

OAc<br />

AcO<br />

Me<br />

H<br />

Me<br />

Ph<br />

Ce (IV)<br />

KO<br />

N<br />

O<br />

Me<br />

H<br />

Me<br />

Target nitronates (24) are 1,3-dipoles <strong>and</strong>, consequently, can also be <strong>in</strong>volved<br />

<strong>in</strong> [3 + 2]-cycloaddition reactions with oleÞns. However, it can a priori be<br />

expected that the rate of the second cycloaddition will be substantially lower.<br />

Anions of polynitro compounds (21) or neutral nitrodiazo compounds (22)<br />

can be considered as possible precursors of nitrocarbenes (A↔B) by analogy<br />

with other functionalized carbenes. Nitrocarbenes can react with a double bond<br />

(1)<br />

(2)

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