Electrochemical oxyphenylselenation of dienes

Article abstract of DOI:10.1007/PL00010143

The electrochemical oxidation of diphenyl diselenide in the presence of dienes affords the corresponding cyclic β-phenylselenoethers via an oxyphenylselenation process. The yields of ethers depend on the nature of the diene and on the reaction temperature

Full text of DOI:10.1007/PL00010143

Monatshefte fuÈr Chemie 129, 1309±1312 (1998)
Electrochemical Oxyphenylselenation of Dienes
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Rastko D. Vukicevic , Milos Radovic, and Stanimir Konstantinovic
Department of Chemistry, Faculty of Science, University of Kragujevac, YU-34000 Kragujevac,
Yugoslavia
Summary. The electrochemical oxidation of diphenyl diselenide in the presence of dienes affords
the corresponding cyclic ꢀ-phenylselenoethers via an oxyphenylselenation process. The yields of
ethers depend on the nature of the diene and on the reaction temperature.
Keywords. Dienes; Oxyphenylselenation; ꢀ-Phenylselenoethers; Tetrahydrofurans; Tetrahydropy-
rans.
Elektrochemische Oxyphenylselenierung von Dienen
Zusammenfassung. Die elektrochemische Oxidation von Diphenyldiselenid in Gegenwart von Dienen
ergibt uÈber einen Oxyphenylselenierungsprozeû die entsprechenden cyclischen ꢀ-Phenylselenoether.
È
Die Ausbeuten an Ethern hangen von der Natur des Diens und der Reaktionstemperatur ab.
Introduction
The anodic generation of electrophilic selenium species in the presence of suitable
substrates like carbonyl compounds, ole®ns, unsaturated alcohols, and carboxylic
acids etc. has become a neat method for the introduction of selenium units into
organic molecules. The application of this method in the synthesis of ꢁ-phenyl-
selenoketons [1], aliphatic and cyclic ꢀ-phenylselenoethers [2, 3], ꢀ-phenylsele-
nolactones [3] etc. has appeared in the literature. In continuation of our investigations
directed at developing syntheses of oxygen containing heterocycles [3, 4], we
subjected dienes to a treatment with the phenylselenyl cation derived from the
electrochemical oxidation of diphenyl diselenide, expecting the formation of the
corresponding cyclic ethers. These expectations were based on literature data
describing oxyselenation induced by reagents such as PhSeOH [5], phenyl
selenocyanate [6], and phenylselenyl chloride [7].
Results and Discussion
In the present investigation we started from the electrolysis of an acetic acid/water
solution (10:1) of 1,5-cyclooctadiene (1a), diphenyl diselenide, and tetraethylam-
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Corresponding author

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R. D. Vukicevic et al.
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Scheme 1
monium chloride or bromide at a constant current (4 F/mol). From the reaction
mixture, two selenosubstituted isomeric oxabicyclononanes, i.e. 2,5-bis(phenylse-
leno)-9-oxabicyclo[4.2.1]nonane (2a) and 2,6-bis(phenylseleno)-9-oxabicyclo-
1
[3.3.1]nonane (3a) were isolated and identi®ed by their IR, H NMR, and 13C
NMR spectroscopic data. When the reaction was carried out at ambient
temperature, the total yield of these compounds was 74%; electrolysis under
re¯ux resulted in a yield of 85%. However, in both cases ether 2a was found to be
the predominant one (2a/3a ˆ 90:10 and 92:8).
We believe that the reaction starts by oxidation of halide ions at the anode to
elemental halogens or halonium ions which then oxidize diphenyl diselenide,
affording the phenylselenyl halide or the free phenylselenyl cation. These selenium
species react with one of the double bonds of the diene, giving an episelenonium
ion which attacks of the nucleophile water, affording the selenosubstituted unsaturated
alcohol 4. The reaction then proceeds further on the known way [3], affording
ethers 2a and 3a (Scheme 1).
We applied this reaction technique to the oxyphenylsenation of another four
dienes in order to synthesize the corresponding cyclic ethers. Thus, 4-
vinylcyclohexene (1b), 1,5-hexadiene (1c), 1,6-heptadiene (1d), and 1,7-octadiene
(1e) were subjected to electrolysis under the same conditions. The results are
summarized in Scheme 2. As it can be seen from Scheme 2, the yield of the
corresponding ethers depends on the nature of the dienes. Cyclic and open-chain
dienes that contain a system of double bonds like 1a, 1c, and 1d underwent this
reaction giving good yields of tetrahydrofuran or of tetrahydropyran-type cyclic
ethers. On the other hand, 1e, with its remote double bonds gave a low yield of the
corresponding oxepane derivative as could be expected (only 3% at ambient
temperature and 12% under re¯ux). However, 1b, containing the same system of
double bonds as 1c, gave also a lower yield of ethers. We think that this is mainly
caused by the conformational situation of the substrate as well as of the reaction
products.

Oxyphenylselenation of Dienes
1311
Isolated yields based on diphenyl diselenide; a at ambient temperature; b under re¯ux
Scheme 2
In our opinion, the reaction described above could be of interest for the
synthesis of cyclic ethers or complex molecules containing these structural
fragments. Its advantages are relatively cheap substrates, the simple experimental
technique (which does not require expensive and complex equipment), and the ease
of removal the phenylseleno group, either by oxidative or reductive methods [8].
Experimental
All chemicals, substrates, and electrode materials used were commercially available and were used
as received. IR measurements were carried out with a Perkin-Elmer instrument (Model 137B). NMR
spectra were obtained with a Varian Gemini (model 200) spectrometer (200 MHz) using TMS as
internal standard and CDCl3 as the solvent. As a direct current source, a Uniwatt, Beha Labor-
È
Netzgerat (NG 394) was used. A cylindrical glass vessel supplied with a magnetic stirrer, electrodes
(two 1.5Â2.5 cm platinum foils), and a re¯ux condenser was used as an undivided cell for
electrolysis.
In a typical procedure, 20 ml of an acetic acid/water (10:1) solution of 5 mmol of the corre-
sponding substrate, 5 mmol of diphenyl diselenide, and 200 mg of (C2H5)4NCl were placed in the
cell and electrolyzed at ambient temperature or under re¯ux. After passing 4 F/mol of electricity
(200 mA, 32 min) through the mixture, electrolysis was stopped, and the resulting reaction mixture
was stirred for 3 h, poured into 30 ml of water, and extracted with ether (3Â30 ml). The organic
layers were washed with a saturated solution of NaHCO3, water, and brine and dried over anhydrous
Na2SO4. After evaporation of the solvent, the residual oil was puri®ed by column chromatography
(SiO2; petroleum ether/ethyl acetate ˆ 20:1). All products of reactions (2a, 3a, 2b, 3b, 2c, 3c, 2d,
1
and 2e) are known compounds; their IR, H NMR, and 13C NMR spectroscopic data were identical
with those described in the literature [5±7].

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R. D. Vukicevic et al.: Oxyphenylselenation of Dienes
1312
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Received July 7, 1998. Accepted (revised) July 31, 1998