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Journal of Organometallic Chemistry 553 1998 481–482
Preliminary communication
An unusual rearrangement of
1-trimethylsiloxy-3-bromomagnesium-2-propyne
)
A.S. Medvedeva , V.V. Novokshonov, M.M. Demina, M.G. Voronkov
Institute of Organic Chemistry, Siberian DiÕision, Russian Academy of Sciences, 1 FaÕorsky Street, 664033 Irkutsk, Russian Federation
Received 14 May 1997
Abstract
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3-Trimethylsilyl-2-propyn-1-ol 4 was synthesized via the rearrangement of 1-trimethylsiloxy-3-bromomagnesium-2-propyne and
followed by hydrolysis of the latter. The yield of compound 4 depends largely on the solvent used. q 1998 Elsevier Science S.A.
Keywords: Rearrangement; Silyl migration; Silyl ethers; Silylacetylenic alcohols
The general method for the preparation of trior-
ganylsilylethynyl-alkanols R3SiC[CCH2OH is the re-
The rearrangement occurs under reflux of intermedi-
ate 2 in the solvent. The subsequent hydrolysis of the
reactive complex with 5% HCl leads to the isolation of
alcohol 4 in 80% yield with THF as the solvent and
24% in ether. The promotion of the reaction with THF
is likely to be due to the good solubility of Iotsitch’s
reagent 1. On 10-fold dilution of the reaction mixture
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action of trialkylhalosilanes with bis bromomagnesium
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derivatives of acetylenic alcohols 1 . Recently, we have
developed a method for the preparation of 3-trialkylsi-
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lyl trialkylgermyl -2-propyn-1-ols by reaction of 1-tri-
methylsiloxy-3-bromomagnesium-2-propyne with trior-
ganylchlorosilanes or -germanes yield 85–87% 2 .
The application of trimethylsilyl ethers of acetylenic
alcohols in synthetic chemistry is mainly connected
with blocking or protecting of hydroxyl by trimethyl-
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. w x
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in ether the yield of 4 is five times lower. This fact
counts in favor of the intermolecular character of the
transformation of 1 to 4. The described reaction is a
new convenient route to the preparation of alcohol 4
widely used in the synthesis of carbofunctional
w x
siloxy group 3 .
w
x
Silyl protected cyclopropan alkanols and alkenols
containing a tin substituent were found to undergo
transmetalation followed by 1,4-silyl migration from
trimethylsilyl ethynyl silanes 5–7 .
w x
oxygen to carbon in the presence of methyllithium 4 .
An unusual transformation of 1-trimethylsiloxy-2-pro-
1. Experimental details
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pyne 1 to isomeric alcohol 3-trimethylsilyl-2-propyn-
1-ol 4 in the presence of Grignard reagent has been
1.1. Typical procedure for the synthesis of 4
found by us.
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To a solution of Grignard reagent 1.95 g, 80 mmol
1,4-Migration of trimethylsilyl group O™Csp in 1
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Mg, 8.72 g, 80 mmol EtBr, 100 ml THF reagent 1
10.26 g, 80 mmol was added dropwise, then the
reaction mixture was heated at reflux for 9 h. The
reaction mixture was treated with 5% hydrochloric acid
and extracted with ether. Organic solution was dried
over MgSO4, concentrated and distilled in vacuo to give
probably proceeds by this scheme.
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EtMgBr
Me3SiOCH2C[CH ™ Me3SiOCH2C[CMgBr
1
2
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. ™ BrMgOCH2C[CSiMe3
THF Et2O
H 3Oq
™
™
reflux
3
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the alcohol 4 8.21 g, 80% , b.p. 70–718Cr11 mm Hg,
HOCH2C[CSiMe3
n2D0 1.4510. Lit. 3 : b.p. 768Cr11 mm Hg, nD 1.4508.
20
w x
4
y1
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1240 Si–C , 2172 C[C ,
IR-spectrum film : n cm
3300 OH . 1H NMR CDCl3 : d 0.16 s, 9H,
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)
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CH3 3Si ; 2.88 s, 1H, OH ; 4.25 s, 2H, CH . Anal.
Corresponding author.
0022-328X
r
98
r
$19.00
q
1998 Elsevier Science S.A. All rights reserved.