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

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REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 329<br />

R 2<br />

O<br />

N<br />

O<br />

N<br />

R 1<br />

O<br />

N<br />

N<br />

NH<br />

H<br />

O<br />

O<br />

H 3C<br />

N<br />

O<br />

OH<br />

Ref. 751<br />

OH<br />

O<br />

N<br />

N<br />

R 2<br />

O<br />

NH<br />

H<br />

O<br />

N<br />

O<br />

O<br />

N<br />

R 1<br />

OH<br />

H 3C<br />

(a) R 1 = CH3(CH2)6CH2; R 2 = H; (b) R 1 = R 2 = CH3(CH2)6CH2;<br />

HOH2C<br />

H<br />

HOH2C<br />

H<br />

N O<br />

N O<br />

Ref. 752<br />

B<br />

HOH2C<br />

B = Thym<strong>in</strong>e (a)<br />

B<br />

H<br />

HOH2C<br />

H<br />

5-Fluorouracil (b)<br />

Ref. 753<br />

Fig. 2.36<br />

N O<br />

N O<br />

regioisomers of isoxazolid<strong>in</strong>es (531)-(534). Their compositions <strong>and</strong> yields depend<br />

on the structure of the start<strong>in</strong>g reagents with substituents at C3, C4, <strong>and</strong> C5 <strong>in</strong><br />

the cis-position (Scheme 2.250) (751).<br />

Cycloadditions of cyclic (a) <strong>and</strong> acyclic (b) nitrones to achiral (535a) <strong>and</strong><br />

chiral α-diphenylphosph<strong>in</strong>yl alkenes (535b,c) have been reported (752). In each<br />

case, addition to allyldiphenylphosph<strong>in</strong>e oxide (535a) gave a s<strong>in</strong>gle isoxazolid<strong>in</strong>e<br />

N<br />

B<br />

O<br />

B<br />

OH

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