4- pyrazol-3-ones, reaction with acetone

All recorded condensations with ketones have taken place at C4 of 2,4-dihydropyrazol-3-ones. Reaction even with the simplest ketone, acetone, requires heating at the boiling point. Therefore under these conditions pyrazol-3-ones 306a f... 

Palladium-catalyzed cross-coupling reactions of aryl chlorides 5 with hydrazine afforded intermediate arylhydrazines 6 at ambient temperatures, which reacted further with P-diketones to give 1,3,5-trisubstituted pyrazoles 7 in one-pot (13AG(E)3434). Palladium-catalyzed Heck car-boxylative cross-coupling reactions of aryl iodides with acetone afforded the in situ 1-aryl-1,3-butadiones, which reacted with an aqueous solution of hydrazine in ethanol to give 3-methyl-5-arylpyrazoles in moderate yields (13CEJ12624). 

To a stirred solution of aldehyde (1 1 mmol), active methylene cyano derivative (2 1.2 mmol) and Bestmann-Ohira reagent (3 1.5 mmol) in distilled methanol (4 mL), was added molecular sieves followed by powdered KOH (2 mmol) and the reaction mixture was stirred at room temperature for one hour. Upon completion of the reaction (TLC monitoring), methanol was distilled off under reduced pressure. The crude residue was dissolved in ethyl acetate (50 mL) and washed with saturated ammonium chloride (2 x 20 mL). Finally the organic layer was washed with saturated brine (20 mL) and dried over anhydrous sodium sulphate. After removal of the solvent, column chromatographic purification was carried out using 0-30% acetone-dichloromethane as eluent to afford phosphonyl pyrazole 4. All the products were characterized based on spectral studies. 

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