A ionic hydrogenation of aryl-substituted 4H-selenopyrans

Full text of DOI:10.1007/s10593-009-0239-1

Chemistry of Heterocyclic Compounds, Vol. 45, No. 1, 2009
A IONIC HYDROGENATION OF ARYL-
SUBSTITUTED 4H-SELENOPYRANS
B. I. Drevko1*, A. F. Almaeva1, I. N. Isaev1,
V. G. Mandych1, and I. M. Uchaeva1
Keywords: 2,4,6-triaryl-4H-selenopyrans, 2,4,6-triarylselenacyclohexanes, ionic hydrogenation.
Aryl-substituted 4H-thiopyrans readily undergo catalytic and ionic hydrogenation [1]. Their seleno
analogs readily eliminate elemental selenium in attempts to perform catalytic and other traditional methods of
hydrogenation [2]. Aryl-substituted selenacyclohexanes were obtained and characterized upon the
disproportionation of 4H-selenopyrans under acid catalysis conditions [3].
We are the first to report the ionic hydrogenation of 2,4,6-triaryl-4H-selenopyrans 1 and 2 to give the
corresponding 2,4,6-triarylselenacyclohexanes.
C6H4R-p
C6H4R-p
CF3COOH
HSiEt3
Ph
Se
Ph
Ph
Se
Ph
3, 4
1, 2
1, 3 R = H; 2, 4 R = OMe
GC/MS analysis of the reaction mixture indicated that the isomer content of the sample of
2,4,6-triphenylselenacyclohexane (3) obtained by ionic hydrogenation was identical to the isomer content of the
product obtained by disproportionation [3] and contained more than 97% of one isomer, while the second isomer
was present as an impurity. (p-Methoxyphenyl)-2,6-diphenyl-4-selenacyclohexane (4) was obtained as a mixture
of four isomers; the content of the major isomer was about 70%. Selenacyclohexane 4 obtained by
disproportionation contained more than 90% major isomer.
The GC/MS analysis of the samples was carried out on an HP5890/5972 unit equipped with an HP-5MS
capillary column. The injector temperature was 200°C. The onset time was 3 min. The onset temperature was
50°C. The final temperature was 280°C, ∆T = 10°C/min. Helium served as the gas carrier, v = 1 ml/min. The
1H NMR spectra were obtained at 30°C on a Varian FT 80A spectrometer at 80 MHz in CDCl3 using TMS as
the internal standard.
_______
* To whom correspondence should be addressed, e-mail: svirhbz@overta.ru, drevko777@mail.ru.
1Saratov Military Institute of Biological and Chemical Security, Saratov 410037, Russia.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 143-144, January, 2009. Original
article submitted October 2, 2008.
0009-3122/09/4501-0123©2009 Springer Science+Business Media, Inc.
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Preparation of Selenacyclohexanes 3 and 4 (General Method). Triethylsilane (0.3 ml, 2.1 mmol) was
added to selenopyran (1 mmol) and then trifluoroacetic acid (0.37 ml) was added with stirring. After the
reaction mixture became a homogeneous liquid phase, it was cooled to room temperature. The crystalline
precipitate was filtered off, analyzed by GC/MS, and recrystallized from ethanol to give compound 3 and
compound 4 as single isomers.
1
2,4,6-Triphenylselenacyclohexane (3) was obtained in 79% yield (0.297 g), mp 110-112°C. H NMR
spectrum, δ, ppm (J, Hz): 2.37-2.50 (4H, m, β-H); 2.51-2.84 (1H, m, γ-H); 4.48 (2H, dd, J = 3.9, J = 11.8, α-H);
7.14-7.39 (15H, m, C6H5).
4-(p-Methoxyphenyl)-2,6-diphenylselenacyclohexane was obtained in 85% yield (0.343 g) (38% after
recrystallization), mp 116-118°C. 1H NMR spectrum, δ, ppm (J, Hz): 2.32-2.72 (5H, m, β-H + γ-H); 3.71 (3H, s,
OCH3); 4.35 (2H, dd, J = 4.3, J = 9.6, α-H); 6.71 (2H, d, J = 8.8, arom); 7.05-7.33 (12H, m, arom).
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