Au(I)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines.

Hung-Chou Wu, Chia-Wen Yang, Long-Chih Hwang, Ming-Jung Wu

Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Taiwan.

Organic & biomolecular chemistry 2012 Sep 7

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Pyrazolo[1,5-a]pyridines and 6-iodopyrazolo[1,5-a]pyridines were synthesized by gold-catalyzed and iodine-mediated cyclization of enynylpyrazoles in good to excellent yields, respectively. The iodinated adducts were further converted to 6-arylpyrazolo[1,5-a]pyridines via Suzuki-Miyaura coupling reaction and 6-cyanopyrazolo[1,5-a]pyridine by Ullmann condensation reaction. One of the cyclization adducts, 2-(4-fluorophenyl)pyrazolo[1,5-a]pyridine, was converted to a p38 kinase inhibitor, 2-(4-fluorophenyl)-3-(4-pyridinyl)pyrazolo[1,5-a]pyridine, in two steps.

Citation

Hung-Chou Wu, Chia-Wen Yang, Long-Chih Hwang, Ming-Jung Wu. Au(I)-catalyzed and iodine-mediated cyclization of enynylpyrazoles to provide pyrazolo[1,5-a]pyridines. Organic & biomolecular chemistry. 2012 Sep 7;10(33):6640-8