Russian Chemical Bulletin, International Edition, Vol. 55, No. 10, pp. 1867—1868, October, 2006
1867
New thermal rearrangement of
2
,4,6ꢀtriarylthio(seleno)pyrylium salts
B. I. Drevko,aꢀ E. V. Suchkova, G. A. Baranchikova, and V. G. Mandych
b
a
a
aSaratov Military Institute of Radioactive, Chemical, and Biological Defense,
5
prosp. 50ꢀletiya Oktyabrya, 410037 Saratov, Russian Federation.
Fax: +7 (845 2) 55 0744. Eꢀmail: svirhbz@overta.ru
b
Saratov State Technical University,
7
7 ul. Politekhnicheskaya, 410054 Saratov, Russian Federation
It is known that1—3 4Hꢀthio(seleno)pyrans and thioꢀ
pyrylium salts can be oxidized into the corresponding
aroylfurans, ꢀthiophenes, and ꢀselenophenes. In addition,
when analyzing pyrylium, thiopyrylium, and selenoꢀ
pyrylium perchlorates by the GCꢀMS method, we have
found that the mass spectra and retention times of the
compounds under analysis are completely identical with
It should be noted that the reactions with selenoꢀ
pyrylium salts are slightly more selective than those with
thiopyrylium salts. When the corresponding pyrylium perꢀ
chlorates were used, aroylfurans were not isolated in
the individual state: they were only detected by GCꢀMS
with aroylfuran as an authentic sample.
Heating of selenopyrylium (1, 2) and thiopyrylium
perchlorates (3) in the absence of an adsorbent gave comꢀ
plex mixtures of products that was not reliably analyzed
by GCꢀMS.
4
those of aroylselenophenes, ꢀthiophenes, and ꢀfurans.
5
This is in conflict with the previous MS data for 2,4,6ꢀtriꢀ
phenylpyrylium perchlorate: analogous spectra have been
explained by the specific character of fragmentation of
the heteroaromatic cation.5
Products were analyzed by GCꢀMS on an HP5890/5972
instrument (Tinj = 200 °C; t = 3 min; T = 50 °C; T = 280 °C;
i
i
f
We have found that seleno(thio)pyrylium perchlorates
–1
–1
∆
T = 10 °C min ; helium as a carrier gas, v = 1 mL min ;
1
—3 applied to alumina transform to the corresponding
aroylselenophenes and ꢀthiophenes 4—6 (Scheme 1) in
2—65% yields on heating to 300 °C in an inert atmoꢀ
HPꢀ5MS capillary column). Preparative TLC was performed
with hexane—ether (5 : 1) and hexane—ether—chloroform
(3 : 1 : 1) as eluents; spots were visualized with the iodine vapor.
4
IR spectra were recorded on an IKSꢀ29 spectrophotometer
sphere (the yields of crude products reached 85—95%;
however, the content of impurities was 10 to 30%
1
(
Nujol and hexachlorobutadiene). H NMR spectra were reꢀ
corded on a Varian FT 80A spectrometer at 30 °C with Me Si as
4
(
GCꢀMS data)).
the internal standard.
Experimental procedure. An appropriate chalcogenopyrylium
perchlorate6 (2 mmol) was dissolved in a minimum amount of
,7
Scheme 1
EtOH—CHCl (1 : 2), applied to alumina (10 g), concentrated
3
at ~20 °C, and transferred to a quartz reaction vessel. The sysꢀ
tem was purged with argon, heated to 300 °C, and then cooled
to ~20 °C. The resulting product was thoroughly extracted with
diethyl ether (the starting salts are insoluble in ether). The solꢀ
vent was removed and the residue was purified by column chroꢀ
matography on alumina with hexane—ether (6 : 1) as an eluent.
1
1
The H NMR and IR spectra agree with the previous data.
ꢀBenzoylꢀ3,5ꢀdiphenylselenophene (4) was obtained from
,4,6ꢀtriphenylselenopyrylium perchlorate (1). The yield of the
2
2
crude product was 88% (89% purity according to GCꢀMS data).
After the chromatography, the yield was 65%, m.p. 89—90 °C
(
cf. Ref. 1: m.p. 85.0—86.5 °C).
ꢀ(4ꢀMethoxybenzoyl)ꢀ5ꢀ(4ꢀmethoxyphenyl)ꢀ3ꢀphenylꢀ
2
selenophene (5) was obtained from 2,6ꢀbis(4ꢀmethoxyphenyl)ꢀ
4ꢀphenylselenopyrylium perchlorate (2). The yield of the crude
product was 85% (90% purity according to GCꢀMS data). After
the chromatography, the yield was 54%, m.p. 134—136 °C
(cf. Ref. 1: m.p. 135—137 °C).
Compound
X
R
1
2
3
, 4
, 5
, 6
Se
Se
S
H
OMe
H
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1800—1801, October, 2006.
066ꢀ5285/06/5510ꢀ1867 © 2006 Springer Science+Business Media, Inc.
1
Drevko
