09.02.2013 Views

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

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

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

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

718 NITRONATES<br />

R 1 CH 2NO 2<br />

R 2 CHO<br />

R 3 CH=CHOEt<br />

R 3<br />

EtO<br />

Si – trialkylsilyl<br />

(SiMe 3/pyrid<strong>in</strong>e most preferable)<br />

NO 2<br />

R 3<br />

R 2<br />

R 1<br />

O N<br />

O<br />

575<br />

R 2<br />

573<br />

R 1<br />

N<br />

OH<br />

Scheme 3.279<br />

O N(OSiMe2But R′<br />

576a<br />

)2<br />

577a,b<br />

576b<br />

NO 2<br />

SiX/base<br />

R<br />

OSiMe 2Bu t•<br />

R 3<br />

EtO<br />

R 3<br />

R′<br />

R 2<br />

R 2<br />

R 1<br />

O N<br />

OSi<br />

A<br />

R 1<br />

N<br />

574<br />

EtOCHO<br />

OSi<br />

N<br />

578a–d<br />

50%–90%<br />

R′ = OSiMe2Bu t : R = CH2CO2Et, PhSO2; R′ = H : R = CH2X (X = CO2Et, SO2Ph)<br />

NO2 N(OSiMe2But ) 2 N<br />

R<br />

R• OSiMe2But •<br />

576c 577c 578e,f<br />

R = CH2X (X = CO2Et, SO2Ph)<br />

Scheme 3.280<br />

R •<br />

OSiMe 2Bu t<br />

70%–80%<br />

OSiMe2Bu t<br />

F<strong>in</strong>ally, conjugated enoximes can be synthesized by the reactions of radical<br />

reagents with specially synthesized BENA conta<strong>in</strong><strong>in</strong>g a system of conjugated<br />

double bonds (527) (see Scheme 3.280, for more details, see Section 3.5.4.2.3).<br />

The advantage of this method is that it does not afford unstable <strong>in</strong>termediate<br />

α-nitrosoalkenes.<br />

However, the necessity of us<strong>in</strong>g rather rare AN (576) for the construction of<br />

BENA (577) substantially limits its preparative value.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!