Cleavage of vinyl carbon-silicon bond in γ-trimethylsilyl allylic alcohols

Article abstract of DOI:10.1081/SCC-100107013

Cleavage of the vinyl carbon-silicon bond by fluoride ion requires a free hydroxyl group located in such a position that stable cyclic transition state can be attained.

Full text of DOI:10.1081/SCC-100107013

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CLEAVAGE OF VINYL CARBON–SILICON BOND IN γ-
TRIMETHYLSILYL ALLYLIC ALCOHOLS
M. I. Al-Hassan a & R. B. Miller b
a Department of Chemistry , College of Science, King Saud University , P.O. Box 2455,
Riyadh, 11451, Saudi Arabia
b Department of Chemistry , University of California , Davis, California, 95616, U.S.A.
Published online: 16 Aug 2006.
To cite this article: M. I. Al-Hassan & R. B. Miller (2001) CLEAVAGE OF VINYL CARBON–SILICON BOND IN γ-TRIMETHYLSILYL
ALLYLIC ALCOHOLS, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 31:23, 3641-3645, DOI: 10.1081/SCC-100107013
To link to this article: http://dx.doi.org/10.1081/SCC-100107013
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SYNTHETIC COMMUNICATIONS, 31(23), 3641–3645 (2001)
CLEAVAGE OF VINYL
CARBON–SILICON BOND
IN c-TRIMETHYLSILYL
ALLYLIC ALCOHOLS
M. I. Al-Hassan1 and R. B. Miller2
1Department of Chemistry, College of Science,
King Saud University, P.O. Box 2455,
Riyadh-11451, Saudi Arabia
2Department of Chemistry, University of
California, Davis, California 95616, USA
ABSTRACT
Cleavage of the vinyl carbon–silicon bond by fluoride ion
requires a free hydroxyl group located in such a position
that stable cyclic transition state can be attained.
The replacement of the silyl group in an alkenylsilane by an electro-
phile often takes place stereospecifically.1 With a proton as the electrophile,
retention of configuration occurs in all cases. A catalytic amount of
hydroiodic acid, either as such or generated in situ from iodine and water,
appears to be the reagent of choice.2 Also, benzenesulphenic acid has also
been recommended.3 Both reagents were employed with vinylsilanes 1 but
3641
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REPRINTS
3642
AL-HASSAN AND MILLER
unfortunately no reaction took place under the normal conditions.1
This might be explained by the electron withdrawing effect of the hydroxyl
group which may deactivate the double bond towards electrophilic attack.
Next attention was turned to the utility of nucleophilic reagents such
as fluoride ions. Despite the fact that the cleavage of silicon-vinyl carbon
bonds by nucleophilic displacement at silicon is extremely rare, Chan and
Mychajlowskij4,5,6 have found that treatment of hydroxyvinylsilane 3 with
fluoride ion in a dipolar solvent followed by quenching with water resulted
in cleavage of the siliconvinyl carbon bond with the formation of the corre-
sponding allylic alcohol. The presence of the hydroxyl group at the
(b-carbon to silicon is essential for the reaction to occur. Therefore, it was
surprising to find that, when vinylsilanes 1 were treated with potassium
fluoride in dimethylsulfoxide followed by quenching with water, cleavage
of the siliconvinyl carbon bond had occurred with the formation of the
corresponding allylic alcohols 2(Table) despite the fact that the hydroxyl
group is at the g-carbon to silicon.
R0
R
% Isolated Yield
H
H
H
n-C3H7
N-C4H9
CH3
Sec-C4H9
CH3
70
70a
80
70
aGLPC yield.
Although little is known about the mechanism of this reaction, Chan4
has postulated that a free hydroxyl group is necessary for hydrogen bonding
to a fluoride ion in the transition state which would result in a six-membered
ring with an exocyclic double bond 3. In the present case a similar postulate
could be proposed resulting in a seven-membered ring with an endocyclic
double bond 4.

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VINYL CARBON–SILICON BOND
3643
In order to determine that these structural requirements were indeed
necessary for this reaction to proceed, vinylsilanes 5,6,7 and 8 were
subjected to the reaction conditions and found to give no reaction.
From these results it is clear that indeed cleavage of the silicon-vinyl
carbon bond requires a free hydroxyl group which is cis to the silicon and
located in such a position that a cyclic transition state such as 3 or 4 can be
attained.
EXPERIMENTAL
Preparation of trans-2-Hepten-1-ol: To 0.372g (2mmol) of ( Z)-3-tri-
methylsilyl-2-hepten-1-ol in 10 mL of dry dimethyl sulfoxide was added
0.232 g (4 mmol, 2 eq.) of anhydrous potassium fluoride. The resulting
suspension was refluxed at 150ꢀC for 5 h, then partitioned between ether
and water and separated. The aqueous layer was thoroughly extracted with