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

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Me<br />

REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 359<br />

FSPE<br />

O<br />

XR f<br />

Acylation<br />

1,3-DC<br />

FSPE<br />

HN O<br />

Bn<br />

O<br />

R<br />

XR f = fluorous chiral auxiliary<br />

Catalyst:<br />

+ −<br />

N O<br />

585<br />

Ph<br />

+<br />

PdCl 2(NCPh) 2<br />

OEt<br />

catalyst: Pd (II)<br />

Ph<br />

Scheme 2.282<br />

Fig. 2.45<br />

Ph<br />

O<br />

N<br />

FSPE<br />

Ph<br />

Reduction<br />

Tol2<br />

P<br />

P<br />

Tol2<br />

N<br />

Me O OEt<br />

Scheme 2.283<br />

XRf<br />

Ph<br />

Pd NCMe<br />

NCMe<br />

O<br />

N<br />

Ph<br />

Ph<br />

(BF 4) 2<br />

OH<br />

N<br />

Me O OEt<br />

trans-646 cis-646<br />

<strong>and</strong> (650), constitutes a new method for prepar<strong>in</strong>g hydroxy azepanes, such as<br />

monocyclic (652) (Scheme 2.284) or azepanes fused to a pyrrolid<strong>in</strong>e r<strong>in</strong>g (653),<br />

(654) (Scheme 2.285) (802).<br />

1,3-Dipolar cycloadditions of nitrones with v<strong>in</strong>yl acetate leads to 5-acetoxyisoxazolid<strong>in</strong>es,<br />

which can be easily transformed to isoxazolid<strong>in</strong>yl nucleosides by<br />

the Vorbrüeggen methodology (803).<br />

Cycloadditions of nitrones (655) <strong>and</strong> (656) to v<strong>in</strong>yl acetate proceed regioselectively<br />

<strong>and</strong> lead to the isoxazolid<strong>in</strong>es (657) <strong>and</strong> (658) as a mixture of diastereomers<br />

(Scheme 2.286) (Table 2.27) (206).<br />

+

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