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Handbook of Functionalized Organometallics Applications in S

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286<br />

7 Polyfunctional Z<strong>in</strong>c <strong>Organometallics</strong> for Organic Synthesis<br />

199<br />

(FG-R) 2Zn<br />

or<br />

FG-RZnI<br />

Zn<br />

2<br />

1) PCl 3<br />

1) Et2NPCl2, Et2O 2) BH 3<br />

2) BH 3 . Me2S<br />

1) Cl2P PCl2 2) BH 3 . Me2S<br />

(FG-R) 2PNEt 2<br />

BH 3<br />

Scheme 7.60 Preparation <strong>of</strong> polyfunctional phosph<strong>in</strong>es.<br />

HCl<br />

P<br />

H 3B<br />

BH 3<br />

200 :75%<br />

P P<br />

BH 3<br />

201 :70%<br />

(FG-R) 2PCl<br />

Et 2O BH 3<br />

203 202<br />

Similarly functionalized organometallics such as the ser<strong>in</strong>e-derived z<strong>in</strong>c±copper<br />

derivate 204 react under mild conditions with ClPPh2. The result<strong>in</strong>g phosph<strong>in</strong>e<br />

was protected as a sulfide provid<strong>in</strong>g enantiomerically pure 205 <strong>in</strong> 75%<br />

yield. Modification <strong>of</strong> the protect<strong>in</strong>g groups furnishes the selectively protected<br />

diphenylphosph<strong>in</strong>oser<strong>in</strong>e 206 <strong>in</strong> 80% yield (Scheme 7.61) [146a].<br />

A comb<strong>in</strong>ation <strong>of</strong> a substitution reaction with a chlorophosph<strong>in</strong>e followed by a<br />

hydroboration, boron±z<strong>in</strong>c exchange allows the preparation <strong>of</strong> the mixed 1,2diphosph<strong>in</strong>e<br />

207 <strong>in</strong> good yield (Scheme 7.62) [145].<br />

Reactive organometallic reagents, such as Cr(CO) 5´THF readily add diorganoz<strong>in</strong>cs<br />

lead<strong>in</strong>g <strong>in</strong> the presence <strong>of</strong> CO (1 atm) and Me3O + ±<br />

BF4 (rt, 2 h) to functionalized<br />

Fischer-carbene complexes [146b]. Excellent addition reactions are also<br />

obta<strong>in</strong>ed with im<strong>in</strong>ium trifluoroacetates, such as 208. The reaction <strong>of</strong> the am<strong>in</strong>al<br />

209 with trifluoroacetic anhydride <strong>in</strong> CH2Cl2 at 0 C gives the im<strong>in</strong>ium trifluoroacetate<br />

208 with quantitative yield. Its reaction with phenylz<strong>in</strong>c chloride furnishes<br />

the expected am<strong>in</strong>e 210 <strong>in</strong> 85% yield [147]. Interest<strong>in</strong>gly, this approach can be<br />

extended to functionalized organomagnesium reagents [148]. <strong>Functionalized</strong> diarylz<strong>in</strong>cs<br />

such as 211 add to the activated Schiff base 212 lead<strong>in</strong>g to am<strong>in</strong>o-acid<br />

213 <strong>in</strong> 62% yield [149].

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