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ChemicalBook CAS DataBase List Antipyrine
60-80-0

Antipyrine synthesis

10synthesis methods
Antipyrine (1) was prepared from the reaction of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one with methyl iodide in methanol or in acetonitrile containing sodium bicarbonate in water in 58% yield. The reaction of 1-methyl-2-phenylhydrazine (2) with methyl 3-oxobutanoate (3) in acetonitrile gave 1 and pyrazolone 4 . Krohn has been reported the synthesis of 1 from the reaction of 5 with dimethyl sulfate in 71% yield. The reaction of pyrazolone 6 with methanol in the presence of triphenylphosphine afforded 1 (14%) and pyrazole 7 (53%). The same reaction was reported by Pegurier et al by heating the reactants in methanol containing calcium monoxide. Knorr early reported also, the synthesis of antipyrine from heating of 1-phenyl-5-ethoxy-3- methylpyrazole (8) with methyl iodide in methanol.
Synthesis of antipyrine
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Yield:60-80-0 58%

Reaction Conditions:

Stage #1:3-methyl-1-phenylpyrazolin-5-(4H)-one;methyl iodide in acetonitrile at 120;
Stage #2: with sodium hydrogencarbonate in water;ethyl acetate

Steps:

16
In a stainless steel pressure bomb the pyrazalone (1.0 equiv.) in acetonitrile was set stirring with iodomethane (5.0 equiv.) in a 12O0C oil bath overnight. The crude product was added to saturated sodium bicarbonate and then extracted four times into ethyl acetate. After concentration, the crude product was chromatographed in a mixture of dichloromethane and methanol. NMR was used to determine the purity of the isolated compounds.; I3 5-Dimethyl-2-phenyl-l, 2-dihydropyrazol-3-one was obtained from 5-methyl-2-phenyl-l, 2-dihydropyrazol-3-one (3.52 g, 20 mmol) and iodomethane (3.38 mL, 60 mmol) in acetonitrile (20 mL) as an off-white solid (2.2 g, 58%). 1H NMR (300 MHz, CDCl3): δ(ppm) 7.26 - 7.49 (m 5H), 5.41 (s, IH), 3.07 (s, 3H), 2.25 (s, 3H).

References:

ASTRAZENECA AB;NPS PHARMACEUTICALS, INC. WO2006/71730, 2006, A1 Location in patent:Page/Page column 50

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