- A practical access to novel 2-amino-5-arylidene-1,3-thiazol-4(5H)-ones via sulfur/nitrogen displacement under solvent-free microwave irradiation
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A new effective approach to the synthesis of a small library of 2-amino-5-arylidene-1,3-thiazol-4(5H)-ones was reported using solvent-free reaction conditions under microwave irradiation. In the first step, rhodanines were subjected to Knoevenagel condens
- Bourahla, Khadidja,Derdour, A?cha,Rahmouni, Mustapha,Carreaux, Fran?ois,Bazureau, Jean Pierre
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- Chemoselectivity of the [2+3]-cycloaddition of thiocarbonyl ylides with 5-benzylidene-3-phenylrhodanine
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Reactions of three different thiocarbonyl S-methylides, generated from thiobenzophenone (2), 2,2,4,4-tetramethyl-3-thioxocyclobutanone (3), and adamantanethione (8), respectively, and diazomethane, with 5-benzylidene-3- phenylrhodanine (12) were carried out. The aromatic thiocarbonyl ylide la adds chemoselectively to the C,C-double bond, but the spirocyclic 1,3-dithiolane 18, i.e. the [2+3]-cycloadduct with the C=S group of 12, was also formed as a minor product. In the cases of the aliphatic thiocarbonyl ylides 6 and 20, the [2+3]-cycloaddition occurred at the exocyclic C,C-double bond exclusively to give the spirocyclic tetrahydrothiophene derivatives 23 and 21, respectively. A smooth acid-catalyzed decomposition of 18 yielded the 2-diphenylmethylidene derivative 19. The formation of product 24, which was obtained in the reaction of the sterically congested ylide 6 with 12, is explained by a 1,4-H-shift in an intermediate zwitterionic adduct. The structures of the tetrahydrothiophenes 17, 21 and 23, as well as that of 24, were established by X-ray crystallography.
- Seyfried,Linden,Mloston,Heimgartner
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p. 1363 - 1376
(2007/10/03)
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