Allylsilanes

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