2930-37-2Relevant academic research and scientific papers
2,4,5-Triarylthiobenzophenones by ring transformation of 2,4,6- triarylthiopyrylium salts with arylacetaldehydes
Zimmermann
, p. 252 - 254 (2007/10/02)
2,4,6-Triarylthiopyrylium salts 1 and arylacetaldehydes 2 react in the presence of sodium methoxide in methanol by a 2,5-[C4 + C2, ring transformation to give 2,4,5-triarylthiobenzophenones 3. This ring transformation offers a new an
Pyrylium Compounds. 34. 2-Acetonyl-2H-thiopyrans from 2,4,6-Triarylthiopyrylium Salts
Zimmerman, Thomas,Fischer, Gerhard W.
, p. 573 - 581 (2007/10/02)
2,4,6-Triarylthiopyrylium salts 4 react with acetone in the presence of amine salts of weak acids (e.g. piperidine acetate) to give the hithero unknown 2-acetonyl-2H-thiopyrans 5, the structure of which was established by spectroscopic methods.Depending on the nature of the amine salts used, the enamine 6 or the enol 7 of acetone may function as attacking nucleophile.Using the 2,4,6-triphenyl derivative 5a as model compound, some typical reactions of 2-acetonyl-2H-thiopyrans were studied.With 2,4-dinitrophenylhydrazine, semicarbazide and thiosemicarbazide, the carbonyl derivatives 10a-c are formed.Hydrogen peroxide in acetic acid affords the S,S-dioxide 11.Methanolic sodium methoxide or sodium hydroxide in aqueous ethanol give rise to a ring transformation yielding 1,3,5-triphenylbenzene (12) and 2,4,6-triphenylacetophenone (13).Under similar conditions, benzaldehyde reacts with 5a to give 2',4',6'-triphenylchalcone (14).Perchloric acid regenerates from 5a the initial thiopyrylium perchlorate 4a.
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).
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.
Rates and Equilibria of the Reaction of 2,4,6-Triphenylthiopyrylium Ion with Piperidine and Morpholine in Me2SO. An Unusual Proton Transfer to a Nitrogen Base
Doddi, Giancarlo,Ercolani, Gianfranco
, p. 7082 - 7087 (2007/10/02)
The complete set of kinetic and equilibrium constants of the reaction of 2,4,6-triphenylthiopyrylium ion (1) with piperidine and morpholine has been obtained in Me2SO at 25 deg C.The reaction involves the formation of both the corresponding 2H- and 4H-thiopyrans, which equilibrate to form only the more stable 2H adduct.The kinetic data are consistent with a two-step process wherein the proton transfer form the protonated 2H- and 4H-thiopyran intermediates to the amine is the rate-controlling step.The thermodynamically favored proton transfer to the neutral adducts by the solvated proton shows a rate below the diffusion limit, whwreas the observed Broensted coefficient would indicate a diffusion-controlled process.This behavior is discussed in terms of the Eigen mechanism.The factors affecting the nucleophilic addition are discussed, and a comparison is made with the previously reported reaction of 1 with primary amines.
