- Synthesis of 4-trifluoromethylpyrimido[4,5-c]-pyridazine-5,7-dignes from uracils
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The reaction of 6-hydrazinouracils (1) with 3-aryl-1,1,1-trifluoropropane-2,3-dione monohydrates (2) in refluxing ethanol in the presence of p-toluenesulfonic acid gave regioselectively 3-aryl-4-trifluoromethyl-5,6,7,8-tetrahydropyrimido[4,5-c]pyridazine-
- Takahashi, Masahiko,Ogawa, Yoshinobu,Inoue, Kazuhiro
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p. 1875 - 1883
(2007/10/03)
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- Studies on uracils: A facile one-pot synthesis of pyrazolo[3,4-d]pyrimidines
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The reaction of 6-hydrazino uracils 1 and nitrones 2 result in an efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidines 3 in excellent yields. The isolation of the by-product aniline from the reaction mixture supported the plausible mechanism for the formation of pyrazolo[3,4-d]pyrimidines.
- Bhuyan,Borah,Lekhok,Sandhu
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p. 491 - 493
(2007/10/03)
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- Studies on Uracils. 10. A Facile One-Pot Synthesis of Pyrido- and Pyrazolopyrimidines
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The reaction of functionalised uracils bearing amino and hydroxyamino groups at C-6 position (4 and 5) with strongly electrophilic cyano olefins (1,2 and 3) gave rise to pyridopyrimidines 7-9 in excellent yields.Hydrazine-substituted uracil 6 gave access to an efficient one-step synthesis of pyrazolopyrimidines 10.The capture of an eliminated hydrogen molecule by cyano olefins in the case of their reaction with 4 and 6 was confirmed by the isolation of dihydrocyano olefins.This fact further supported the plausible mechanism for the formation of compounds 7-10 via dihydropyrido- and dihydropyrazolopyrimidine intermediates A and C.
- Bhuyan, Pulakjyoti,Boruah, Romesh Chandra,Sandhu, Jagir Singh
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p. 568 - 571
(2007/10/02)
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- Reaction of 6-Arylidenehydrazino-1,3-dimethyluracils with Thionyl Chloride Leading to Purine, Thiazolopyrimidine, Pyrimidothiadiazine, Pyrazolopyrimidine, and Thiadiazolopyrimidine Derivatives
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The reaction of 6-arylidenehydrazino-1,3-dimethyluracils with thionyl chloride in benzene afforded purine, thiazolopyrimidine, pyrimidothiadiazine, pyrazolopyrimidine, and thiadiazolopyrimidine derivatives, while
- Ichiba, Misuzu,Senga, Keitaro
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p. 381 - 384
(2007/10/02)
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- N-Bromosuccinimide in Heterocyclic Synthesis. Synthesis of Pyrazolopyrimidines, Pyrimido-as-triazines, and Pyrimidopyridazines from 6-Arylidenehydrazino-1,3-dimethyluracil Derivatives
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Reactions of 6-arylidenehydrazino-1,3-dimethyluracil derivatives with N-bromosuccinimide leading to pyrazolopyrimidines, pyrimido-as-triazines, and pyrimidopyridazines are described.
- Kanazawa, Hashime,Nishigaki, Sadao,Senga, Keitaro
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p. 969 - 974
(2007/10/02)
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- Photochemistry of Heterocycles, 8. The Photoreaction of 2,5-Diaryl-1,3,4-oxadiazoles with 1,3-Dimethyluracils. A New and Simple Synthesis of 1,2,4,5-Tetrazines
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Upon UV-irradiation 2,5-diaryl-1,3,4-oxadiazoles 2a-g do not undergo (2+2)-cycloaddition with 1,3-dimethyluracil, but instead ring cleavage occurs to afford the benzoylhydrazones 3a-e as well as the decomposition products 4-6.With 6-chloro-1,3-dimethyluracil (1b) 3h is formed, which in turn photoeliminates benzoyl chloride to give the pyrazolopyrimidine 7.Saponification of 3a gives smoothly 5-benzoyl-1,3-dimethyluracil (photoselective 5-benzoylation). - A new and simple synthesis of 3,6-disubstituted 1,2,4,5-tetrazines from aroylhydrazines is described, employing the system triphenylphosphane/hexachloroethane/triethylamine.
- Farkas, Lajos,Keuler, Josef,Wamhoff, Heinrich
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p. 2566 - 2574
(2007/10/02)
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