Oxidation of 2,4,6-triaryl-4H-thio(seleno)pyrans with selenium dioxide

Drevko, B. I.; Fomenko, L. A.; Харченко, В. Г.

doi:10.1007/bf00470019

Cited by 2 publications

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“…The 1 H NMR and IR spectra agree with the previous data. 1 2 Benzoyl 3,5 diphenylselenophene (4) was obtained from 2,4,6 triphenylselenopyrylium perchlorate (1). The yield of the crude product was 88% (89% purity according to GC MS data).…”

Section: Methodsmentioning

confidence: 99%

New thermal rearrangement of 2,4,6-triarylthio(seleno)pyrylium salts

et al. 2006

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It is known that 1-3 4H thio(seleno)pyrans and thio pyrylium salts can be oxidized into the corresponding aroylfurans, thiophenes, and selenophenes. In addition, when analyzing pyrylium, thiopyrylium, and seleno pyrylium perchlorates by the GC MS method, we have found that the mass spectra and retention times of the compounds under analysis are completely identical with those of aroylselenophenes, thiophenes, and furans. 4 This is in conflict with the previous 5 MS data for 2,4,6 tri phenylpyrylium perchlorate: analogous spectra have been explained by the specific character of fragmentation of the heteroaromatic cation. 5 We have found that seleno(thio)pyrylium perchlorates 1-3 applied to alumina transform to the corresponding aroylselenophenes and thiophenes 4-6 (Scheme 1) in 42-65% yields on heating to 300 °C in an inert atmo sphere (the yields of crude products reached 85-95%; however, the content of impurities was 10 to 30% (GC MS data)). Scheme 1Compound X R 1, 4 Se H 2, 5 Se OMe 3, 6 S HIt should be noted that the reactions with seleno pyrylium salts are slightly more selective than those with thiopyrylium salts. When the corresponding pyrylium per chlorates were used, aroylfurans were not isolated in the individual state: they were only detected by GC MS with aroylfuran as an authentic sample.Heating of selenopyrylium (1, 2) and thiopyrylium perchlorates (3) in the absence of an adsorbent gave com plex mixtures of products that was not reliably analyzed by GC MS.Products were analyzed by GC MS on an HP5890/5972 instrument (T inj = 200 °C; t i = 3 min; T i = 50 °C; T f = 280 °C; ∆T = 10 °C min -1 ; helium as a carrier gas, v = 1 mL min -1 ; HP 5MS 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. IR spectra were recorded on an IKS 29 spectrophotometer (Nujol and hexachlorobutadiene). 1 H NMR spectra were re corded on a Varian FT 80A spectrometer at 30 °C with Me 4 Si as the internal standard.Experimental procedure. An appropriate chalcogenopyrylium perchlorate 6,7 (2 mmol) was dissolved in a minimum amount of EtOH-CHCl 3 (1 : 2), applied to alumina (10 g), concentrated at ~20 °C, and transferred to a quartz reaction vessel. The sys 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 sol vent was removed and the residue was purified by column chro matography on alumina with hexane-ether (6 : 1) as an eluent. The 1 H NMR and IR spectra agree with the previous data. 1 2 Benzoyl 3,5 diphenylselenophene (4) was obtained from 2,4,6 triphenylselenopyrylium perchlorate (1). The yield of the crude product was 88% (89% purity according to GC MS data). After the chromatography, the yield was 65%, m.p. 89-90 °C (cf. Ref. 1: m.p. 85.0-86.5 °C).2 (4 Methoxybenzoyl) 5 (4 methoxyphenyl) 3 phenyl selenophene (5) was obtained from 2,6 bis(4 methoxyphenyl) 4 phenylselenopyr...

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Section: Methodsmentioning

confidence: 99%

New thermal rearrangement of 2,4,6-triarylthio(seleno)pyrylium salts

et al. 2006

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“…There are several reports concerning the oxidation of mono and benzene ring fused six-membered heterocycles containing a chalcogen atom. The selenium dioxide oxidation of 4 H -thiopyrans [ 14 ] and 4 H -selenopyrans [ 14 ] produces a ring contraction to give hiophenes and selenophenes, respectively. The oxidation of dihydro-2 H -selenopyrans [ 15 ] with sodium periodate is also known to produce selenophenes.…”

Section: Introductionmentioning

confidence: 99%