Dimethyl Sulfoxide-Assisted, Iodine- and Ascorbic Acid-Catalyzed One-Pot Synthetic Approach for Constructing Highly Substituted Pyrazolo[1,5- a ]quinoline Thioether Derivatives.

A dimethyl sulfoxide-assisted and iodine/ascorbic acid-catalyzed 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 .