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

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

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REACTIONS OF DIPOLAR 1,3-CYCLOADDITION ([3 + 2] CYCLOADDITION) 357<br />

Me<br />

Me<br />

O<br />

O<br />

(+)-DIOP<br />

R<br />

O<br />

N<br />

PPh2<br />

PPh2<br />

N<br />

Cy2P<br />

N<br />

O<br />

a: R = Pr i (pybox-Pr i )<br />

b: R = Bu t (pybox-Bu t )<br />

Bu t<br />

O<br />

N<br />

R<br />

N<br />

Boc<br />

BCPM<br />

O<br />

R R<br />

Fig. 2.42<br />

O<br />

PPh 2<br />

PAr2<br />

PAr2<br />

(S)-BINAP : Ar = Ph<br />

(S)-TolBINAP : Ar = p-Tol<br />

(S)-MeOBINAP : Ar = p-MeOC 6H 4<br />

(S)-ClBINAP : Ar = p-ClC 6H 4<br />

N<br />

N<br />

a: R = H (pybox-hm)<br />

b: R = Sit-BuMe 2 (pybox-tbdmsom)<br />

c: R = Si(Pr i ) 3 (pybox-tipsom)<br />

d: R = Sit-BuPh 2 (pybox-tbdpsom)<br />

Fig. 2.43<br />

N<br />

N<br />

OR RO<br />

O<br />

Fig. 2.44<br />

Bu t<br />

O<br />

xabox - R<br />

a: R = Pr i<br />

b: R = Ph<br />

c: R = Bn<br />

cycloaddition reactions, with no change <strong>in</strong> the yields or selectivities (Scheme<br />

2.282).<br />

Dipolarophiles D11 . In the 1,3-dipolar cycloadditions of electron-rich oleÞns,<br />

such as v<strong>in</strong>yl ethers, with nitrone (585), common palladium (II) catalysts were<br />

used (Fig. 2.45). Reactions proceeded smoothly under mild conditions <strong>and</strong> <strong>in</strong><br />

good yield, afford<strong>in</strong>g isoxazolid<strong>in</strong>es (646) (Scheme 2.283) (799).

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