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Handbook of Functionalized Organometallics Applications in S

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O<br />

R<br />

n + ArNC Ni(COD) 2<br />

R<br />

Ph<br />

SiMe 3<br />

n = 3, R = TMS 88%<br />

n=4,R=Et 94%<br />

+ ArNC<br />

n<br />

Ni(COD) 2 O<br />

82%<br />

10.6 Intramolecular Coupl<strong>in</strong>g <strong>of</strong> Enynes or Alkynes 421<br />

R<br />

R<br />

Ph<br />

NAr<br />

SiMe 3<br />

NAr<br />

CSA<br />

In the presence <strong>of</strong> silylhydrides,<strong>in</strong>tramolecular cyclizations <strong>of</strong> 1,7-diynes give<br />

stereoselectively the correspond<strong>in</strong>g term<strong>in</strong>ally substituted dienes <strong>in</strong> good yields [153,<br />

154].<br />

O<br />

O<br />

H<br />

H<br />

H<br />

+ H-SiMe2(O-i-C3H7) H<br />

Ni(acac) 2/DIBALH<br />

73%<br />

Z/E = 95/5<br />

Interest<strong>in</strong>gly,bisdiene also undergoes a similar cyclization ± hydrosilation<br />

across the two diene units to form trans-1,2-div<strong>in</strong>ylcyclopentane derivatives as a<br />

mixture <strong>of</strong> olef<strong>in</strong> geometrical isomers [151].<br />

MeO2C MeO2C MeO 2C<br />

MeO 2C<br />

+ H-SiMe2(O-i-C3H7) Ni(acac) 2 /DIBALH/PPh3 60%<br />

SiMe 2(O-i-C 3H 7)<br />

+ MeO 2C<br />

MeO 2C<br />

(2 : 1)<br />

O<br />

O<br />

H<br />

H<br />

n<br />

R<br />

R<br />

O<br />

SiMe 2(O-i-C 3H 7)<br />

When a disilane is employed <strong>in</strong> the above hydrosilation reaction under similar<br />

conditions,a bicyclic silacyclepentadiene (silole is formed via a nickel-silylene<br />

<strong>in</strong>termediate [151].<br />

TBSO<br />

S S<br />

OTBS<br />

R<br />

R<br />

+ H-SiR2SiX3 Ni(acac) 2<br />

SiR<br />

R<br />

DIBALH<br />

R<br />

+ HPh Ni(acac)<br />

2SiSiMe 2/PEt3/DIBALH 3<br />

~40%<br />

TBSO<br />

S Si S<br />

Ph Ph<br />

SiMe 2(O-i-C 3H 7)<br />

OTBS

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