Regiospecific synthesis of 1,5-disubstituted-1H-pyrazoles containing differentiated 3,4-dicarboxylic acid esters via Suzuki coupling of the corresponding 5-trifluoromethane sulfonates

Iodine-promoted synthesis of pyrazoles from 1,3-dicarbonyl compounds and oxamic acid thiohydrazides

A novel approach to 3,4-dicarbonyl-substituted pyrazoles from 1,3-dicarbonyl compounds and oxamic acid thiohydrazides was developed via iodine-promoted cascade imination/halogenation/cyclization/ring contraction reaction.

A chemo- and regiocontrolled approach to bipyrazoles and pyridones via the reaction of ethyl 5-acyl-4-pyrone-2-carboxylates with hydrazines

Chemo- and regiocontrolled syntheses of pyrazoles and pyridones are presented on the basis of 4-pyrones. A novel approach towards highly functionalized 3,4'-bipyrazoles has been developed by using reactions of ethyl 5-acylcomanoates with hydrazines. The acid-promoted double cyclocondensation allows switching of the structure of the pyrazole rings easily through changing both the nature of hydrazine and the reaction conditions. The transformation of 4-pyrones with phenylhydrazine in EtOH at -20 °C leads to hydroxypyridones as monoaddition products which can be used as precursors for the preparation of pyridone and pyrazole derivatives. A novel rearrangement of 2-hydroxypyridone to pyrazolyl-1,3-diketones in DMSO was found. The structure and regiochemistry of bipyrazoles were confirmed by X-ray analysis and 2D NMR experiments.