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

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

680 NITRONATES<br />

R 2<br />

R 2<br />

R 2<br />

N H<br />

434<br />

SiO<br />

N<br />

NO2<br />

432<br />

R 1<br />

N(OSi) 2<br />

R 1<br />

R 1<br />

O Si<br />

H N<br />

+<br />

Si<br />

R 2 N<br />

N<br />

R 2 N<br />

SiO<br />

456<br />

N<br />

454<br />

R 1<br />

R 1<br />

R 2<br />

OSi<br />

OSi<br />

SiO<br />

A<br />

MeOH<br />

N<br />

R 1<br />

Scheme 3.243<br />

N H<br />

OH<br />

N Si<br />

N Si<br />

SiOH<br />

R 2 N<br />

N<br />

SiO<br />

N<br />

R 2<br />

B<br />

R 1<br />

R 2 N<br />

453<br />

R 2 N<br />

455<br />

R 1<br />

N<br />

R 1<br />

R 1<br />

OH<br />

453<br />

OH<br />

N H<br />

transform various AN (432) <strong>in</strong>to not well known α-am<strong>in</strong>o oximes (453), which<br />

can be considered as promis<strong>in</strong>g build<strong>in</strong>g blocks <strong>in</strong> the design of organic molecules<br />

<strong>and</strong> also as compounds hav<strong>in</strong>g potential biological activity <strong>and</strong> other useful properties<br />

(e.g., polydentate lig<strong>and</strong>s, chelat<strong>in</strong>g agents).<br />

The reactions of am<strong>in</strong>es with BENAs were discussed <strong>in</strong> several publications<br />

(464, 499, 521–523). Although there are no special studies on the reaction mechanism,<br />

the available data comb<strong>in</strong>ed with the results <strong>in</strong> Reference 502 suggest a<br />

mechanistic model for this process (Scheme 3.243).<br />

Apparently, am<strong>in</strong>es act as Si-nucleophiles toward BENAs (434), <strong>and</strong> elim<strong>in</strong>ation<br />

of silylam<strong>in</strong>es (SiN < ) <strong>and</strong> silanol (from hemiacetals A) affords nitrosoalkenes<br />

B as key <strong>in</strong>termediates of this process. Accord<strong>in</strong>g to the published data<br />

(503), α-nitrosoalkenes B react with am<strong>in</strong>es to give the target oximes (453),<br />

O<br />

OH

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

Saved successfully!

Ooh no, something went wrong!