71709-21-2Relevant academic research and scientific papers
SELENOPYRYLIUM SALTS IN REACTIONS WITH SODIUM METHOXIDE
Drevko, B. I.,Petrakov, S. N.,Fomenko, L. A.,Zhukov, O. I.,Smushkin, M. I.,et al.
, p. 124 - 126 (2007/10/02)
It was shown by PMR spectroscopy that the reaction of selenopyrylium salts with sodium methoxide gives various reaction products, depending on the number and nature of the substituents at the heteroaromatic cation: 4H-Selenopyrans, a mixture of 4H- and 2H
Pyrylium Compounds. 33. 2-Dialkylamino-2H-thiopyrans from 2,4,6-Triaryl-thiopyrylium Salts
Zimmermann, Thomas,Fischer, Gerhard W.
, p. 567 - 572 (2007/10/02)
2,4,6-Triaryl-thiopyrylium salts 7 react with dialkylamines in diethyl ether to give stable crystalline 2-dialkylamino-2H-thiopyrans 8, the structure of which is in accordance with their u.v., n.m.r. and mass spectra.The chemical properties of 8 parallel those of structurally analogous 2-alkoxy- and 2-dialkylamino-2H-pyrans and 2-alkoxy-2H-thiopyrans.Thus, on heating 2-dimethylamino-2,4,6-triphenyl-2H-thiopyran (8a) with methanol the corresponding 2-methoxy-2H-thiopyran 9 is formed.Nitromethane and ethyl cyanoacetate give rise to ring transformations yielding 1,3,5-triphenyl benzene (10) and 2,4,6-benzonitrile (11), respectively.From 8a electrophiles (e.g. mineral acids, methyl iodide, benzoyl chloride) regenerate the initial thiopyrylium system by taking over the dialkylamino group.
Pyrylium Compounds. 32. 2-Methoxy-2H-thiopyrans from 2,4,6-Triaryl-thiopyrylium Salts
Zimmermann, Thomas,Fischer, Gerhard W.
, p. 373 - 379 (2007/10/02)
Reaction of 2,4,6-triarylthiopyrylium salts 1 with sodium methoxide in absolute methanol yields isolable 2-methoxy-2H-thiopyrans 2, the structure of which was proved spectroscopically.Using the 2,4,6-triphenyl derivative 2a as model compound, the behaviour of the 2-methoxy-2H-thiopyran system towards some nucleophiles and electrophiles was studied.Thus, on heating with ethanol the 2-ethoxy-2H-thiopyran 3 is formed.Nitromethane and ethyl cyanoacetate react with 2a in the presence of triethylamine to give 2,4,6-triphenylbenzene (6) and 2,4,6-triphenylbenzonitrile (7), respectively.Electrophiles (e.g. mineral acids or acyl halides) regenerate from 2a the starting thiopyrylium system; the same principle underlies the formation of 2,4,6-triphenyl-thiopyrylium perchlorate (1a) and 2-methoxy-3-methyl-2,4,6-triphenyl-2H-pyran (5) from 2a and 3-methyl-2,4,6-triphenylpyrylium perchlorate (4).
1H Nuclear Magnetic Resonance Study of Methoxide Addition to Pyrylium and Thiopyrylium Cations; Heteroatom and Substituent Effects
Doddi, Giancarlo,Ercolani, Gianfranco
, p. 271 - 276 (2007/10/02)
Methoxide addition to pyrylium and thiopyrylium salts with various α-substituents (Ph or tBu) and γ-substituents (H, Me, tBu, Et3C, Ph or MeO) in methanol at -40 and 25 deg C has been studied by 1H n.m.r.The composition of the product mixtures, kinetically controlled at -40 deg C and thermodynamically controlled at 25 deg C, gives information on the factors affecting positional selectivity and the relative thermodynamic stability of the addition products (the 2H- and 4H-adduct).The methyl-substituted substrates also undergo deprotonation, to yield the corresponding anhydro-bases.Analysis of heteroatom and substituent effects on the rean course emphasizes the role of polar and steric interactions, and sheds light on the structures of the transition states.
Proton Nuclear Magnetic Resonance Study of the Addition of Methoxide Ion to 2,4,6-Triphenylpyrylium, 2,4,6-Triphenylthiopyrylium, 1,2,4,6-Tetraphenylpyridinium, and 1-(p-Nitrophenyl)-2,4,6-triphenylpyridinium Cations
Aveta, Raffaele,Doddi, Giancarlo,Insam, Normanno,Stegel, Franco
, p. 5160 - 5163 (2007/10/02)
The reactions of 2,4,6-triphenylpyrylium (1a) and 2,4,6-triphenylthiopyrylium (1b) with methoxide ion are shifted toward the formation of adducts, as shown by 1H NMR.The former yields practically only a 2H-pyran adduct in MeCN, Me2SO, or MeOH.In MeOH, 1b yields an adduct with a 2H-thiopyran structure, whereas in MeCN this adduct is obtained together with the isomeric 4H-thiopyran adduct.In Me2SO or MeCN, the 1,2,4,6-tetraphenylpyridinium cation yields a 1,2-dihydropyridine.In contrast, in MeOH this equilibrium is shifted toward the reagents.The lower degree of delocalization of the positive charge in the pyridinium cation seems to be the main cause of its lower tendency to undergo nucleophilic addition.
