Facile synthesis of 2H-indazole derivatives starting from the Baylis–Hillman adducts of 2-cyclohexen-1-one

One-pot easy conversion of Baylis-Hillman adducts into arylpyrazoles under ultrasound irradiation

“…NMR spectra were recorded on a 500 MHz Bruker DRX-500 using CDCl 3 as the solvent. 1 General procedure for the synthesis of 1,5-diarypyrazoles under classical condition 6 (2a-2g)…”

Five‐Membered Heterocycles: 1,2‐Azoles. Part 1. Pyrazoles

“…The reaction needs a slightly acidic medium to catalyze the conversion of the ketone into the hydrazone and it is imperative the use of a Dean-Stark apparatus to eliminate the water, to avoid mesylate hydrolysis to the corresponding phenol, which does not cyclize to indazoles under these reaction conditions. and hexahydro-1H-and 2H-indazole derivatives are also obtained from the reaction of appropriate chalcone-type compounds or b-diketones with hydrazine derivatives [283,284,[286][287][288].…”

“…Under identical conditions, ortho-fluorobenzonitriles 313 afford 3-amino-1H-indazoles 315 (Tetrahydro-2H-indazoles 317 are obtained from the reaction of the Baylis-Hillman adducts of cyclohexen-1-ones (316) with hydrazine derivatives. These tetrahydroindazoles(317) are oxidized to 2-substituted-2H-indazoles 318 by treatment with DDQ (Scheme 8.96)[283]. 3-Substituted-1-aryl-4,5,6,7-tetrahydro-1H-indazoles 320 are obtained by the reaction of diketone 319 with arylhydrazines (Scheme 8.97)[284].…”

A Green, Reusable and Highly Efficient Heterogeneous Catalyst for the Synthesis of Arylpyrazoles using Nano-Fe2O3

“…Arylpyrazole is an important class of organic compounds, which received a considerable attention due to their wide range of biological activities and widely used as pharmaceuticals, agrochemicals, anti-inflammatory, antiviral, antibacterial [3][4][5][6][7][8] . Although heterocycle compounds are valuable compounds and many applications have been reported 9 .…”