Allylsilanes

4.4.40.29 Method 29:
From Mixed Vinylcuprates and (Iodomethyl)trimethylsilane or
Related Reagents
Allylsilanes, for example, 115 (Scheme 50), are available from reaction of mixed vinyl cuprates,
obtainable from vinyllithium reagents and 3-methoxy-3-methylbut-1-ynylcopper,
with (iodomethyl)trimethylsilane or the corresponding trifluoromethanesulfonate 114,
the latter generallygiving better yields. [179] Use of (iodomethyl)dimethylphenylsilane is
preferred in cases where volatilityof the product is of concern. The vinyllithium intermediates
are prepared bya lithium±halogen exchange reaction of vinyl halides, or, alternatively,
by a Shapiro reaction of triisopropylbenzenesulfonylhydrazones (ªtrisylhydrazonesº)
[180] of cyclic and acyclic ketones.
Scheme 50 Allylsilanes from Mixed Vinylcuprates [179]
O O
Br
1. BuLi, THF
2.
MeO
FOR PERSONAL USE ONLY
874 Science of Synthesis 4.4 Silicon Compounds
Cu
O O
Cu
MeO
Me3SiCH2OTf 114
49%
O O
(1,4-Dioxaspiro[4.4]non-6-en-6-ylmethyl)trimethylsilane (115); Typical Procedure: [179]
To a soln of 3-methoxy-3-methylbut-1-yne (74 mg, 0.75 mmol) in THF (3 mL) at 0 8C, BuLi
(0.75 mmol) was added dropwise, and the mixture was stirred for 10 min. The resulting
butynylide anion was added to a stirred suspension of CuI (150 mg, 0.75 mmol) in THF
(3 mL) at 08C, and the mixture was stirred at 08C for 30 min. This soln was added dropwise
to a soln of the 2-lithiated cyclopent-2-en-1-one ethylene ketal (0.75 mmol) (prepared from
the corresponding bromide) in THF (5 mL) at ±788C, and the resulting mixture was stirred
for 30 min at ±788C. To this a soln of trifluoromethanesulfonate 114 (0.19 g, 0.75 mmol) in
THF (2 mL) was added dropwise at ±788C. The mixture was stirred at ±788C for 1 h,
warmed to ±358C, and then stirred at ±358C for 6 h. The mixture was quenched bythe addition
of sat. aq NH 4Cl soln (1 mL). Standard workup in Et 2O gave an oil, which was chromatographed
(silica gel), to provide allylsilane 115; yield: 78 mg (49%).
4.4.40.30 Method 30:
From Carboxylic Acid Derivatives and an Organocerium Reagent
by a Peterson-type Reaction
2-Substituted allylsilanes have been prepared from carboxylic acid derivatives such as
esters byexposure to a twofold excess of organocerium reagent, prepared in situ from
[(trimethylsilyl)methyl]magnesium chloride and cerium(III) chloride, followed by a Peterson-type
elimination of the resultant bis(silylmethyl)carbinols. This method has, for example,
been used in the formation of silane 116 (Scheme 51). [181] Chiral 2-substituted allylsilanes,
for example, 117, [182] as well as allylsilanes containing acid-sensitive functional
groups, for example, 118 [183,184] are also available bythis method (Scheme 51). This procedure
is equallyapplicable to lactones as substrates, as shown bythe preparation of silane
Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG
115
SiMe3