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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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180 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

OH<br />

N<br />

O<br />

O<br />

O<br />

O<br />

Me<br />

Me<br />

O<br />

183<br />

O<br />

186<br />

N<br />

187<br />

+<br />

N<br />

OH<br />

N<br />

O<br />

Ph<br />

N<br />

Ph O<br />

−<br />

R<br />

O<br />

O<br />

O<br />

Me<br />

Me<br />

Scheme 2.65<br />

+<br />

+<br />

Scheme 2.66<br />

R<br />

Δ<br />

Acetone<br />

+ CO2<br />

N O<br />

181<br />

O<br />

Ph<br />

N<br />

O<br />

N<br />

[3+2]<br />

Cycloaddition<br />

O N<br />

R<br />

C<br />

O<br />

184<br />

Nitrosoketene<br />

+ N<br />

O<br />

−<br />

O<br />

R 1<br />

185<br />

R = Ph<br />

R = p-O 2NC 6H 5<br />

R= Ac<br />

O<br />

O<br />

R 1 R 2<br />

2.2.2.5. Other Methods of <strong>Synthesis</strong> Intramolecular cyclic hydroxyam<strong>in</strong>oalkynes<br />

(188) <strong>and</strong> (189), depend<strong>in</strong>g on the relative position between the hydroxylam<strong>in</strong>o<br />

group <strong>and</strong> acetylenic fragment, leads to Þve-(190), six-(191), <strong>and</strong><br />

seven-(192) membered cyclic nitrones (Scheme 2.67) (348–350).<br />

The reaction of N -alkyl- <strong>and</strong> N -arylhydroxylam<strong>in</strong>es with ethyl cyanoformate<br />

(193) leads to carbethoxyam<strong>in</strong>o nitrones (194) (Scheme 2.68), which appear<br />

to be excellent start<strong>in</strong>g materials for the synthesis of various nitrogen-bear<strong>in</strong>g<br />

R 2

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