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. 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. 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).
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.
