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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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332 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

O<br />

O<br />

292 a<br />

26<br />

+<br />

N<br />

O<br />

−<br />

+<br />

O −<br />

N Bn<br />

O<br />

O<br />

Bn<br />

100%<br />

CN<br />

N O<br />

(3R, 5R)-540 c<br />

10%<br />

N 538<br />

Scheme 2.252<br />

O<br />

CN<br />

O<br />

Bn<br />

N O<br />

(3S, 5S)-540 a<br />

35%<br />

+<br />

O<br />

Scheme 2.253<br />

O<br />

Bn<br />

N<br />

CN<br />

N<br />

O<br />

N O<br />

(3R, 5S)-540 d<br />

5%<br />

+<br />

1. SiO2<br />

H<br />

O<br />

H<br />

+<br />

CN<br />

Regio isomers<br />

2. SiO2 Chiral phase<br />

3. HO H<br />

HOOC<br />

COOH<br />

539<br />

O<br />

N<br />

O<br />

Bn<br />

N<br />

N O<br />

(3S, 5R)-540 b<br />

50%<br />

CN

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