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

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360 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

O<br />

O O<br />

648<br />

iii<br />

O<br />

O O<br />

648<br />

OMe<br />

i<br />

Bn<br />

N<br />

O<br />

O<br />

O O<br />

649<br />

OMe<br />

i: CH 2=N( O)Bn 647 toluene, reflux, 72 h,<br />

59% (30% of 647 recovered).<br />

ii: Raney Ni, H 2, MeOH, H 3BO 3 (20 equiv.),<br />

MgSO 4, 20˚C, 2 h, 56%.<br />

iii: NaBH 3CN, AcOH (gl.), 20˚C, 24 h, 49%.<br />

OMe<br />

+<br />

MOMO<br />

X = O<br />

X = H, OH<br />

654<br />

N<br />

O<br />

+<br />

−<br />

312<br />

Scheme 2.284<br />

OMOM<br />

MOMO<br />

MOMO H<br />

i<br />

ii<br />

MOMO<br />

MOMO<br />

HO<br />

O<br />

O O<br />

651<br />

iii<br />

N<br />

Bn<br />

N<br />

H<br />

HO<br />

H H<br />

O O<br />

650<br />

652<br />

Bn<br />

N O OMe<br />

O<br />

H<br />

H H<br />

O O<br />

i: Toluene, reflux, 48 h, 96%.<br />

ii: Raney Ni, H2, MeOH, H3BO3 (20 equiv), MgSO4, 20˚C, 24 h, 43% of 653 <strong>and</strong> 56% of<br />

654 (as a ca. 1:1 mixture of epimers).<br />

iii: NaBH 3, EtOH, 20˚C, 4 h, 98% (as a ca. 1:1 mixture of epimers).<br />

N<br />

653<br />

Scheme 2.285<br />

X<br />

H<br />

O<br />

O<br />

ii

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