Hydroalumination and bromination of 1-(phenylselenyl)- 1-alkynes

Article abstract of DOI:10.1081/SCC-100105675

Hydroaluminuation and bromination of 1-(phenylselenyl)-1-alkynes were studied and compared with the rate of hydroalumination and bromination of the corresponding alkynylsilanes.

Full text of DOI:10.1081/SCC-100105675

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HYDROALUMINATION AND BROMINATION OF 1-
(PHENYL-SELENYL)-1-ALKYNES
Mohammed I. Al-Hassan a
a Department of Chemistry, College of Science, King Saud University, P.O. Box 2455,
Riyadh, 11451, Saudi Arabia
Published online: 16 Aug 2006.
To cite this article: Mohammed I. Al-Hassan (2001): HYDROALUMINATION AND BROMINATION OF 1-(PHENYL-SELENYL)-1-
ALKYNES, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
31:19, 3027-3030
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SYNTHETIC COMMUNICATIONS, 31(19), 3027–3030 (2001)
HYDROALUMINATION AND
BROMINATION OF 1-(PHENYL-
SELENYL)-1-ALKYNES
Mohammed I. Al-Hassan
Department of Chemistry, College of Science,
King Saud University, P.O. Box 2455,
Riyadh 11451, Saudi Arabia
ABSTRACT
Hydroaluminuation and bromination of 1-(phenylselenyl)-
1-alkynes were studied and compared with the rate of
hydroalumination and bromination of the corresponding
alkynylsilanes.
Organoselenium compounds have become an important part of
organic chemistry in recent years.1,2,3 In this paper we have studied the
hydroalumination4 and bromination5 (Table) of 1-(phenylselenyl)-1-alkynes
(1). Thus, the starting material, 1-(phenylselenyl)-1-alkynes (1), was pre-
pared by treatment of the corresponding lithium acetylide with
phenylselenyl chloride in tetrahydrofuran at À75ꢀC for 5 min.6
Compound 2 was prepared via hyroalumination4 of the corresponding
alkynylselenium compound (1). It was found that hydroalumination
of alkynylselenium compound is slow (70ꢀC, 24h) as compared with the
hydroalumination of the corresponding alkynylsilane7,8 (40ꢀC, 1 h). The
disappearance of starting material and the appearance of product was
3027
Copyright & 2001 by Marcel Dekker, Inc.
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AL-HASSAN
Table. Hydroalumination and Bromination of Alkynylselenium
Compounds (1)
% Yield of
Hydroalumination
% Yield of
Bromination
R
CH3-
CH3CH2CH2CH2-
C6H5-
P-CH3-C6-H4-
THPOCH2-
(CH3)3Si-
75
77
78
73
60
70
72
73
80
78
55
62
followed by glpc (PYE unicam series 304chromtograph with OV1 glass
column).
Compound 3 was prepared via bromination5 of the corresponding
alkynylselenium compound (1) at a rate similar to the bromination of the
corresponding alkynylsilane5 (À12ꢀC/15 min).
Preparationof 1-(Phenylselenyl)-1-alkyne (1)
To a solution of 9 mmol of 1-alkyne in 9 mL of dry tetrahydrofuran
(THF) was added slowly to a slight excess of LDA (1.05 equiv.) (prepared
by adding an equivalent amount of n-butyllithium to dry diisopropyl-
amine in dry THF at À10ꢀC over 10 min) at À78ꢀC. After keeping
the mixture for 10 min at À78ꢀC, 9 mL of THF solution containing
9.5 mmol of phenylselenyl chloride (equivalent to LDA or slightly
in excess) was then added rapidly (reaction is instantaneous). The resulting
solution was washed with an excess of 0.1 N HCl and extracted with diethyl
ether. The combined organic layers were washed with saturated sodium
chloride solution and dried over anhydrous sodium sulphate evaporation

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1-(PHENYLSELENYL)-1-ALKYNES
3029
of solvents led to a residue which was chromatographed on 60 g of silica gel.
Elution with hexane gave the desired product in high (90–95%) yield.
Hydroalumination of 1-(Phenylselenyl)-1-alkyne (1)
To a solution of 3 mmol of 1-(phenylselenyl)-1-alkyne in 3 mL of
hexane was added dropwise 3.6 mL of 1 M diisobutylaluminium hydride
in hexane (3.6 mmol, 1.2 eq.) at room temperature for 15 min. The
reaction mixture was refluxed for 24h. At the end of this time, the resulting
mixture was poured into 0.1 N HCl and extracted with hexane. After drying
over sodium sulphate, the solvent was removed by rotary evaporation to
afford a residue which was chromatographed on 20 g of silica gel. Elution
with hexane gave the desired product in good yield.
Bromination of 1-(Phenylselenyl)-1-alkyne (1)
To 3 mmol of 1-(phenylselenyl)-1-alkyne in 6 mL carbon tetra-
chloride was added dropwise 3.6 mL of 1 M solution of bromine in carbon-
tetrachloride (1.2 equiv., 3.6 mmol) at À12ꢀC. The reaction mixture was
stirred for 0.5 h at À12ꢀC. At the end of this time, the resulting mixture
was poured into 10% sodium sulfite solution and extracted with hexane.
After drying over sodium sulfate the solvent was removed by rotary eva-
porator to afford a residue which was chromatographed on 20 g of silica gel.
Elution with hexane gave the desired product in good yield.
ACKNOWLEDGMENT
This research (Chem/1408/12) was supported by the Research Center,
College of Science, King Saud University, Riyadh, Saudi Arabia.
REFERENCES
1. Klayman, D.L.; Gunther, W.H.H. (Eds), Organic Selenium Compounds:
Their Chemistry and Biology. Wiley Interscience, New York (1973).
2. Zingaro, R.A.; Cooper, W.C. (Eds), Selenium. Van Nostrand Reinhold,
New York (1974).
3. Clive, D.L.J. Tetrahedron 1978 34, 1049.
4. Al-Hassan, M.I. Synth. Commun. 1986, 16, 353.

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AL-HASSAN
5. Al-Hassan, M.I. J. Organometal. Chem. 1989.
6. Al-Hassan, M.I. Gazzeta Chemica Italiana 1987, 177, 187.
7. Miller, R.B.; Al-Hassan, M.I. Tetrahedron Lett. 1983, 24, 2055.
8. Al-Hassan, M.I.; Miller, R.B. J. Saudi Chem. Soc. 2000, 4, 191.
Received in the Netherlands October 12, 2000

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