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

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278 NITRONES: NOVEL STRATEGIES IN SYNTHESIS<br />

RCH2CO2Bu t<br />

−H +<br />

O<br />

−<br />

Base<br />

RCH C OBu t<br />

Me<br />

Me<br />

N<br />

−<br />

RCH CO 2Bu t<br />

1R2RC O<br />

+<br />

N R3 Ester: R = Bu t , Et;<br />

Nitrone: a: R 1 = R 3 = Ph, R 3 = H;<br />

b: R 1 = Me, R 2 = H, R 3 = Et;<br />

c: R 1 = R 2 = Me, R 3 = Pr i ;<br />

d) R 1 - R 3 = (CH2)3, R 3 = H;<br />

e: R 1 - R 3 = O-C6H4(CH2)2, R 2 = H;<br />

f: R 1 - R 3 = (CH2)2CMe2, R2 = H<br />

OH<br />

CO 2Bu t<br />

Ph3P, CCl4,Et3N<br />

CH 2Cl 2, reflux<br />

Scheme 2.180<br />

404 406<br />

N<br />

OH<br />

CO 2Bu t<br />

Ph3P, CCl4,Et3N<br />

CH 2Cl2, reflux<br />

NH<br />

CO2But H<br />

(35%)<br />

Me<br />

Me<br />

405 407<br />

Scheme 2.181<br />

+<br />

R3 R1 N<br />

OH<br />

(32%)<br />

N<br />

CO<br />

H<br />

2But H<br />

(84%)<br />

CO2But R2 N<br />

CO 2Bu t<br />

sugars, <strong>and</strong> α-am<strong>in</strong>o nitriles (193, 648, 649). Thus, the reaction of v<strong>in</strong>ylmagnesium<br />

bromide with various nonchiral nitrones proceeds to the correspond<strong>in</strong>g<br />

allyl am<strong>in</strong>es <strong>in</strong> good yields (650). Addition of v<strong>in</strong>ylmagnesium bromide to chiral<br />

nitrones takes place with high diastereoselectivity <strong>in</strong> good yields (651). To illustrate<br />

stereocontrolled addition of v<strong>in</strong>yl organometalic compounds (CH2CHM,<br />

where M = MgBr, CeCl3, CuLi1/2, Li<strong>and</strong>AlEt2) the synthesis of allylam<strong>in</strong>es<br />

(409a,b) has been carried out. Hydroxylam<strong>in</strong>es (408a,b), the products of nucleophilic<br />

addition of v<strong>in</strong>yl organometalics to N -benzyl-2,3-O-isopropylidene-<br />

D-glyceraldehyde nitrone (BIGN) (292) are then reduced to (409a,b) upon<br />

treatment with Zn(0)/Cu(II) (Scheme 2.183) (Table 2.15) (652).

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