Allylsilanes
Allylsilanes
Allylsilanes
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Scheme 35 Enantioenriched E-<strong>Allylsilanes</strong> by Palladium(0)-Catalyzed Intramolecular<br />
Bis-silylsilylation of Allyl Alcohols [138,139]<br />
SiMe2Ph<br />
Ph2Si<br />
O<br />
( )<br />
5<br />
(R,E)-75 99.7% ee<br />
SiMe2Ph Ph2Si O<br />
( ) 5<br />
(R,Z)-75 96.0% ee<br />
Pd(acac) 2 (cat.)<br />
NC<br />
90%<br />
1. Pd(acac) 2 (cat.)<br />
NC<br />
2. BuLi<br />
84%<br />
H<br />
O SiPh2<br />
H<br />
( )<br />
5<br />
H<br />
SiMe2Ph<br />
76<br />
Ph2Si<br />
O<br />
O<br />
SiPh2<br />
H +<br />
( )<br />
5<br />
H ( )<br />
5<br />
PhMe2Si H<br />
77<br />
SiMe2Ph<br />
(S,E)-78 99.1% ee<br />
( ) 5<br />
SiMe 2Ph<br />
(R,E)-78 95.4% ee<br />
[(S,E)-1-Hexylbut-2-enyl]dimethylphenylsilane [(S,E)-78]; Typical Procedure: [138,140]<br />
To Pd(acac) 2 (1.4 mg, 4.5 ” 10 ±3 mmol) placed in a Schlenk tube was added 1,1,3,3-tetramethylbutyl<br />
isocyanide (3.2 ” 10 ±3 mL, 1.8 ” 10 ±2 mmol) at rt. The mixture was stirred for<br />
15 min at rt. To the vivid red catalyst that formed was added toluene (0.4 mL) and disilane<br />
(R,E)-75 (99.7% ee; 107 mg, 0.23 mmol) at rt. The mixture was refluxed with stirring for 2 h.<br />
After the mixture had cooled to rt, the solvent was removed in vacuo. To a soln of the residue<br />
in THF (0.5 mL) was added 1.6 M BuLi in hexane (0.21 mL, 0.34 mmol) at 0 8C. After the<br />
mixture had stirred at 08C for 30 min, sat. aq NH 4Cl was added. Extraction with Et 2O followed<br />
bycolumn chromatography(silica gel, hexane) afforded (S,E)-78 (99.1% ee); yield:<br />
56 mg (90%).<br />
4.4.40.21 Method 21:<br />
Formation of Bis(allylsilanes) from 1,3-Dienes<br />
Bis(allylsilanes) 80 have been prepared with complete control of regio- and stereoselectivity<br />
from 1,3-dienes by a palladium-catalyzed dimerization±disilylation reaction (Scheme<br />
36). [141] It should be noted that this procedure yields exclusively E-1,4 head-to-head dimeric<br />
allylsilanes from 2-substituted 1,3-dienes. [141]<br />
Scheme 36 Synthesis of Bis(allylsilanes) [141]<br />
R 1<br />
79<br />
+<br />
FOR PERSONAL USE ONLY<br />
862 Science of Synthesis 4.4 Silicon Compounds<br />
Me 3Si SiMe 3<br />
Pd(dba) 2<br />
DMF, rt, 40 h<br />
R1 = H 71%<br />
R1 = Me 85%<br />
R1 = Ph 82%<br />
Me 3Si<br />
Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG<br />
R 1<br />
BuLi<br />
80<br />
R 1<br />
SiMe 3