A novel reaction of 2,4,6-triphenyl(thio)selenopyrylium salts leading to benzoyl(thio)selenophenes and 2,4,6-triphenyl(thio)selenopyrans

Article abstract of DOI:10.1007/s11172-009-0207-z

Thio- and selenopyrylium salts undergo simultaneous oxidation, leading to the corresponding benzoylselenophene or benzoylthiophene, and reduction reactions leading to 4H-selenopyran or 4H-thiopyran In the presence of water and triethylamine .

Full text of DOI:10.1007/s11172-009-0207-z

Russian Chemical Bulletin, International Edition, Vol. 58, No. 7, pp. 1526—1527, July, 2009
1526
A novel reaction of 2,4,6ꢀtriphenyl(thio)selenopyrylium salts leading
to benzoyl(thio)selenophenes and 2,4,6ꢀtriphenyl(thio)selenopyrans
B. I. Drevko, E. G. Bol'shakova, A. F. Almaeva, M. A. Suchkov, V. G. Mandych, and G. A. Shekhter
Saratov Military Institute of Biological and Chemical Safеty,
5 prosp. 50ꢀletiya Oktyabrya, 410037 Saratov, Russian Federation.
Fax: +7 (845) 255 0744. Eꢀmail:svirhbz@overta.ru
Thioꢀ and selenopyrylium salts undergo simultaneous oxidation, leading to the correspondꢀ
ing benzoylselenophene or benzoylthiophene, and reduction reactions leading to 4Нꢀseleꢀ
nopyran or 4Нꢀthiopyran In the presence of water and triethylamine .
Key words: selenopyrylium salts, thiopyrylium salts, benzoylselenophene, benzoylthiophene,
4Нꢀselenopyran, 4Нꢀthiopyran.
It is well known that pyrylium, thiopyrylium, and seleꢀ
GCꢀMS data indicate that the ratio of oxidized and
reduced forms is 1:1. The product yield of this reaction in
the case of 2,4,6ꢀtriphenylselenopyrylium perchlorate (1)
is somewhat higher than in the case of 2,4,6ꢀtriphenylꢀ
thiopyrylium perchlorate (2). The product yield of the
same reaction with thioꢀ and selenopyrylium bromozincꢀ
ates is less then 50% (GCꢀMS data). It was not possible
to reliably determine the possibility of the disproportinaꢀ
tion process in the case of pyrylium salts even with the
GCꢀMS method with the use of authentic samples.
When preparative syntheses were carried out, selenopyꢀ
ran 3 and benzoylselenophene 5 crystallized separately
from the ethanolꢀether solution: compound 3 formed
spherical conglomerates of crystals and compound 5
formed needleꢀlike crystals, which were separated manuꢀ
ally. Derivatives of thiopyran 4 and benzoylthiophene 6
were separated by column chromatography.
In a similar reaction, 2,6ꢀdiphenylselenopyrylium perꢀ
chlorate 7 gave a more complex mixture of products
(Scheme 2), which judging by GCꢀMS data consists of
2,6ꢀdiphenylselenopyranꢀ4ꢀone (8, 36%), 2ꢀphenylꢀ5ꢀ
benzoylselenophene (9, 12%), 4Нꢀselenopyran (10, 42%),
and 2,6ꢀdiphenylꢀ2Нꢀselenopyran (11, 5%). It is worth
mentioning that compound 11 was identified only by mass
spectral data (no authentic samples were used).
nopyrylium salts can undergo oxidation or thermal rearꢀ
rangement resulting in the corresponding aroylfurans,
aroylthiophenes, and aroylselenophenes,1—4 or reduction
in the presence of metal hydrides, organometallic reagents,
or sodium methoxide leading to the corresponding pyrans,
thiopyrans, and selenopyrans.2,5—8 Thus, heteroaromatic
cations can both be oxidized and reduced, which is typical
of many disproportionation reactions.
Results and Discussion
We found that arylꢀsubstituted selenopyrylium salts 1
and arylꢀsubstituted thiopyrylium salts 2 undergo disproꢀ
portionation in the presence of water and triethylamine.
The reaction is carried out in DMF and it leads to mixꢀ
tures of benzoylselenophenes and selenopyrans or benꢀ
zoylthiophenes and thiopyrans (Scheme 1).
Scheme 1
Thus, it was established that thioꢀ and selenopyrylium
salts can undergo disproportionation.
Experimental
Analysis by GCꢀMS was carried out on an HP 5890/5972
instrument, the injector temperature was 200 °С; starting temꢀ
perature of the column was 50 °C, this temperature was kept for
3 min after the sample injection after that the temperature was
raised at a rate of 10 °C min–1; the temperature at the end of the
analysis was 280 °C; the carrier gas was helium at a flow rate
X = Se (1, 3, 5); S (2, 4, 6)
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1481—1482, July, 2009.
1066ꢀ5285/09/5807ꢀ1526 © 2009 Springer Science+Business Media, Inc.

2,4,6ꢀTriphenyl(thio)selenopyrylium salts
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 7, July, 2009
1527
Scheme 2
10 : 1) to give 2ꢀbenzoylꢀ3,5ꢀdiphenylthiophene (6). Yield 0.095 g
(14%), m.p. 86—87 °С (lit. data4: m.p. 85—87 °С), yield by GCꢀMS
48%. 2,4,6ꢀTriphenylꢀ4Нꢀthoipyran (4). Yield 0.143 g (22%), m.p.
104—105 °С (lit. data10: m.p. 104—106 °С), yield by GCꢀMS 45%.
After carrying out the reaction with 2,4,6ꢀtriphenylthiopyryꢀ
lium tribromozincate, the etheral solution was analyzed by GCꢀ
MS using authentic samples, which showed that the reaction
mixture contained 24% of 2ꢀbenzoylꢀ3,5ꢀdiphenylthiophene (6)
and 21% of 2,4,6ꢀtriphenylꢀ4Нꢀthiopyran (4).
The reaction of 2,6ꢀdiphenylselenopyrylium perchlorate inꢀ
cluded hexane as a solvent in the workꢀup, column chromatogꢀ
raphy on silica gel L (100/400) (hexane—ether, 10 : 1) afforded
2,6ꢀdiphenylꢀ4Нꢀselenopyran (10), yield 17%, m.p. 50—51 °С
(lit. data12: m.p. 49.5—51.0 °С), yield by GCꢀMS 42% (together with
supposed 2,6ꢀdiphenylꢀ2Нꢀselenopyran (11), which was not deꢀ
scribed in literature; the peak of putative compound 11 was not
completely separated from the peak of compound 10 in GC). The
chromatographical yield of 2ꢀbenzoylꢀ5ꢀphenylselenophene (9)
was 8%, and that of 2,6ꢀdiphenylselenopyranꢀ4ꢀone (8) was 31%.
The 1Н NMR and IR spectra of the products obtained correꢀ
spond to those described earlier .
of 1 mL min–1, capillary column HPꢀ5MS. Analysis by TLC was
carried out on TLC plates using solvent systems hexane—ether
5 : 1 and hexane—ether—chloroform 3 : 1 : 1, visualisation with
iodine vapor. IR spectra were recorded on an IRSꢀ29 spectroꢀ
photometer in Nujol or hexachlorobutadiene. Н NMR spectra
were recorded with a Varian FT 80A spectrometer at 30 °С using
Me4Si as the internal standard.
Authentic samples were obtained using the known methods
of synthesis of 4Нꢀselenopyrans,5,9 4Нꢀthiopyrans,10 3,5ꢀdiphenꢀ
ylꢀ2ꢀbenzoylselenophene and ꢀthiophene,1 5ꢀphenylꢀ2ꢀbenꢀ
zoylselenophene,11 and 2,6ꢀdiphenylselenopyranꢀ4ꢀone.12
Selenopyrylium13 and thiopyrylium14 salts were obtained by
the described methods.
References
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Aroyl(thio)selenophenes and 2,4,6ꢀtriaryl(thio)selenopyrans
(general procedure). Halcogenopyrylium salt (2 mmol), Н2О
(0.1 mL) and 20% ethanolic solution of triethylamine (1 mL)
were added to DMF (10 mL). The reaction was carried out at
60 °С until all the starting salt disappeared from the reaction
mixture (TLC). Water (10 mL) and ether (20 mL) were added to
the reaction mixture. The etheral layer was washed with water,
dried with Na2SO4, and analyzed by GCꢀMS.
After carring out the reaction with 2,4,6ꢀtriphenylselenopyꢀ
rylium perchlorate and workꢀup, ethanol (20 mL) was added to
the etheral solution, and the mixture was concenrated in air.
Needleꢀlike crystals of compound 5 and spherical conglomerꢀ
ates of crystals of compound 3 were separated manually. The
residual oil consists of a mixture of the mentioned compounds
(GCꢀMS data). 2ꢀBenzoylꢀ3,5ꢀdiphenylselenophene (5). Yield
0.14 g (18%), m.p. 88—89 °С (lit. data4: m.p. 89—90 °С), yield by
GCꢀMS 49%. 2,4,6ꢀTriphenylꢀ4Нꢀselenopyran (3). Yield 0.105 g
(14%), m.p. 108—109 °С (lit. data9: m.p. 107.5—109.0 °С), yield
by GCꢀMS 46%.
After carrying out the reaction with 2,4,6ꢀtriphenylselenopyꢀ
rylium tribromozincate, the etheral solution was analyzed by
GCꢀMS using authentic samples, which showed that the reacꢀ
tion mixture contained 27% of 2ꢀbenzoylꢀ3,5ꢀdiphenylseleꢀ
nophene (5) and 22% of 2,4,6ꢀtriphenylꢀ4Нꢀselenopyran (3).
After carrying out the reaction with 2,4,6ꢀtriphenylthiopyryꢀ
lium perchlorate, the etheral solution was concentrated. The
obtained oil was chromatographed on alumina (hexane—ether,
12. B. I. Drevko, S. N. Petrakov, L. A. Fomenko, V. G. Kharchꢀ
enko, Khim. Geterotsikl. Soedin., 1991, 996 [Chem. Heteroꢀ
cycl. Compd. (Engl. Transl.), 1991, 27, 996].
13. Pat. RU 2276150; Bull. Izobret., 2006, No. 13 (in Russian)
14. Invention certificate USSR 1703649; Bull. Izobret., 1992,
No. 1 (in Russian).
Received October 3, 2008;
in revised form March 10, 2009