We dedicate this manuscript to Prof. Burkhard Koenig for his outstanding contribution to photocatalysisThe visible light promoted, oxidative coupling of phenylhydrazine hydrochloride with 2H-indazole derivatives has been demonstrated to obtain 3-arylated-2H-indazole derivatives using a catalytic amount of 4CzIPN (1,2,3,5-tetrakis(carbazol-9yl)-4,6-dicyanobenzene) as a photocatalyst under aerobic conditions. A library of arylated indazole derivatives was prepared in the organo-photocatalytic pathway in good yields under mild reaction conditions. The present strategy was applied to synthesis liver X receptor agonist 4-(7-methoxy-2phenyl-2H-indazol-3-yl) benzonitrile (3).

A dimethyl sulfoxide-assisted and iodine/ascorbic acidcatalyzed simple approach to pyrazolo[1,5-a]quinoline thioether derivatives 22 is described. The compounds were identified using 1 H NMR, 13 C NMR, high-resolution mass spectrometry, and single-crystal X-ray diffractometry. The pyrazolo[1,5-a]quinoline thioether was synthesized in a stepwise fashion through aryl sulfenylation and benzannulation strategies. The generated heteroaryl thioether compounds 23 were exposed to the benzannulation path to produce pyrazolo[1,5-a]quinoline thioether 22. The benzannulation reaction proceeds by way of diazotization of the pyrazole amine derivative 23, radical generation by the removal of nitrogen, and eventually trapping of the aryl radical with the support of phenylacetylene 19. A catalytic amount of ascorbic acid aided the benzannulation reaction. There were several other control studies conducted, including trapping reactions with isopropenyl acetate, tetramethylpiperidine N-oxyl reactions, and reactions without phenylacetylene. Since a change in the substitution has previously demonstrated substantial bioactivity, the core structure of pyrazole was evaluated for functional group tolerance. A reasonable mechanism is then proposed, accompanied by the support of control experiments and scope. A Suzuki reaction was used to create an aryl/heteroaryl compound 35 from one of the synthesized compounds 22b. In the controlled oxidation reaction paths, molecule 22a was selectively transformed into the corresponding sulfoxide 32 and sulfone 33.

A series of cascade reactions that produce a range of functionalized aromatic heterocyclic compounds with pyrazole/pyrazoline cores have been developed. The method relies on a metal-free dehydrogenative process to produce in-situ benzaldehydes. The produced benzaldehyde was then allowed to react with some other substances, including acetophenone, pyrazole amine, and phenylhydrazine. The intermediate produced from these substrates underwent several chemical processes, including electrocyclization, the aza-Diels–Alder reaction, and the formation of intramolecular C–N bonds. These positive outcomes would open up the possibility of producing biologically active pyrazolo­[3,4-b]­pyridine and pyrazoline derivatives through a variety of possible reactions.