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

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Et<br />

H3CO<br />

H 3CO<br />

− O<br />

R R<br />

N<br />

1<br />

H<br />

N<br />

H<br />

O<br />

C O<br />

NHAc<br />

+<br />

N<br />

H<br />

O<br />

C O<br />

NHAc<br />

H<br />

H<br />

CN<br />

MeOH<br />

OCH3<br />

OH<br />

OH<br />

OCH 3<br />

OH<br />

OH<br />

OCH 3<br />

OCH 3<br />

H 3C<br />

Scheme 2.15<br />

C<br />

H2<br />

HO<br />

R + R1<br />

SYNTHESIS OF NITRONES 141<br />

H 3CO<br />

− O<br />

+<br />

N<br />

H<br />

O<br />

C O<br />

H 3CO<br />

NHAc<br />

N<br />

H<br />

O<br />

C O<br />

NHAc<br />

H<br />

H<br />

OCH 3<br />

OH<br />

OH<br />

OCH 3<br />

OH<br />

OH<br />

R<br />

N<br />

R1 NC<br />

m-CPBA<br />

CH2Cl2 N<br />

O<br />

CN<br />

−<br />

R R<br />

N<br />

OH<br />

1<br />

+<br />

44 45 46<br />

Scheme 2.16<br />

OCH 3<br />

OCH 3<br />

Oxidations of a range of β-cyanoethyl tertiary am<strong>in</strong>es (44) with m-CPBA <strong>in</strong><br />

CH2Cl2 give the correspond<strong>in</strong>g N -oxides (45), which can be isolated or undergo<br />

Cope elim<strong>in</strong>ation afford<strong>in</strong>g hydroxylam<strong>in</strong>es (46) <strong>in</strong> high yields (Scheme 2.16)<br />

(Table 2.1) (96). Hydroxylam<strong>in</strong>es (46) can be easily oxidated <strong>in</strong>to nitrones (see<br />

Section 2.2.1.3).<br />

Recently, an oxidative biotransformation of secondary am<strong>in</strong>es <strong>in</strong>to nitrones<br />

apply<strong>in</strong>g cyclohexanone monooxygenase, an enzyme isolated from Ac<strong>in</strong>etobacter<br />

CN

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