Preparation of (Z)- and (E)-vinyl selenides utilizing vinylboronic acids and vinylboronic esters in ionic liquids

Article abstract of DOI:10.1016/S0040-4039(02)00610-X

Vinylboronic acids and vinylboronic esters react with phenylselenyl chloride in ionic liquids to generate vinyl selenides stereospecifically.

Full text of DOI:10.1016/S0040-4039(02)00610-X

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 3703–3705
Preparation of (Z)- and (E)-vinyl selenides utilizing vinylboronic
acids and vinylboronic esters in ionic liquids
George W. Kabalka* and Bollu Venkataiah
Departments of Chemistry and Radiology, The University of Tennessee, Knoxville, TN 37996-1600, USA
Received 4 March 2002; accepted 25 March 2002
Abstract—Vinylboronic acids and vinylboronic esters react with phenylselenyl chloride in ionic liquids to generate vinyl selenides
stereospecifically. © 2002 Elsevier Science Ltd. All rights reserved.
Vinyl selenides have attracted considerable attention
in recent years as synthetic precursors.1 Many sele-
nide preparations involve the use of expensive cata-
lysts or starting materials that are not readily
available.2 Recently, Ogawa and his co-workers
reported that organic selenols react with acetylenes to
generate vinyl selenides.3 However, they were unsuc-
cessful in generating stereochemically pure products,
although (Z)-isomers formed preferentially.
Several vinylboronic acids4,6 and esters were treated
with phenyl selenyl chloride. Substituents such as
bromo and hydroxy are tolerated quite well. Both
(E)- and (Z)-vinylboronates react (Table 1). Pinacol-
ate esters are also reactive but catechol esters are not
suitable substrates due to the electrophilic substitution
reactions of the phenyl selenium cation on the cate-
chol moiety.7
The synthesis of 1-hexenylselanylbenzene is represen-
tative: 1-Hexenylboronic acid (1 mmol) and BmimBF4
(400 mg) were placed in a 10 mL round-bottomed
flask. Phenyl selenenyl chloride (1 mmol) was added
and the mixture was allowed to stir at room tempera-
ture for 2 h. The mixture was washed with ether (4×5
mL) and the combined organic extracts were dried
(MgSO4), filtered, the solvent removed under reduced
pressure and the product purified by silica gel column
chromatography (pentane) to yield 82% of the desired
product.
Since the hydroboration of alkynes proceeds stereose-
lectively to generate (E)-vinylboranes,4 the stereospe-
cific displacement of the boron moiety by selenium
reagents would then afford (E)-vinyl selenides. We
wish to report that vinylboronic acids and vinyl-
boronic esters readily react with phenyl selenenyl
chloride in ionic liquids such as butylimidazolium tet-
rafluoroborate (BmimBF4) and BmimBr to generate
the corresponding phenyl vinyl selenides. Since
BmimBF4 is a liquid at room temperature and it is
easily prepared,5 we decided to utilize BmimBF4 in
the initial phase of the study.
In conclusion, we have developed a simple and
efficient method for the preparation of geometrically
pure vinyl selenides from vinylboronic acids and
esters in ionic liquids. The solvent can be recycled
without significant loss in yields.
Fortunately, good yields are obtained in BmimBF4 at
room temperature. In addition, after completion of
the reaction, the products are simply extracted into
ether and the ionic liquid recycled.
BmimBF4
R
R
OR'
B
+
PhSeCl
SePh
rt, 2 hr.
OR'
Keywords: selenides; boronic acids; boronic esters; ionic liquids.
* Corresponding author. Tel.: (865) 974-3260; fax: (865) 974-3260; e-mail: kabalka@utk.edu
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00610-X

3704
G. W. Kabalka, B. Venkataiah / Tetrahedron Letters 43 (2002) 3703–3705
Table 1. Preparation of vinyl selenides from alkenyl boronates
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