- Microwave-assisted synthesis of symmetrical and unsymmetrical N,N 0-disubstituted thioureas and ureas over MgO in dry media
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Under mild microwave irradiation conditions a variety of symmetrical and unsymmetrical A,N′-disubsti-tuted thioureas and ureas were prepared via the reaction of Af-monosubstituted hydroxylamines with isocyanate and isothiocyanate derivatives over MgO under solvent-free conditions. This new method afforded satisfactory results with good yields, short reaction time, and simplicity in the experimental procedure.
- Valizadeh, Hassan,Dinparast, Leila
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experimental part
p. 251 - 254
(2012/07/01)
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- Process to prepare alkyl-ureas from O,S-dimethyl dithiocarbonate
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The present invention relates to the preparation of alkyl-ureas, starting from O,S-dimethyl dithiocarbonate, which provides the following steps: A) causing the O,S-dimethyl dithiocarbonate to react with a primary amine of general formula R1NH2in order to obtain an O-methyl thiocarbamate; B) isomerising the O-methyl thiocarbamate in order to obtain an S-methyl thiocarbamate; C) causing the S-methyl thiocarbamate with a compound of general formula R′R″NH, wherein R′ and R″ may be equal or different one in respect of the other and of R1and may be H, R2or R3, in order to obtain one of the alkyl-ureas of formula (4), (5) or (6).
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Page column 8-9
(2010/02/06)
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- Pyrimidine Derivatives and Related Compounds. Part 45. Synthesis of 4-Allophanoylpyrazoles via a Pyrimidine-to-pyrazole Ring Transformation
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Reaction of the 5-formyluracil derivatives (1a-f) with hydrazines in the presence of acetic acid produced a ring contraction to give the corresponding 4-allophanoylpyrazoles (2a-h).Further treatment of these pyrazoles (2a-h) with sodium methoxide afforded methyl pyrazole-4-carboxylate (3a).Conceivable mechanisms for the present pyrimidine-to-pyrazole transformation were discussed.
- Hirota, Kosaku,Kitade, Yukio,Shimada, Kaoru,Senda, Shiego,Maki, Yoshifumi
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p. 1293 - 1298
(2007/10/02)
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