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Selective, Metal-Free Approach to 3- or 5-CF3-Pyrazoles: Solvent Switchable Reaction of CF3-Ynones with Hydrazinesстатья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 30 августа 2017 г.
- Авторы: Muzalevskiy Vasiliy M., Rulev Alexander Yu, Romanov Alexey R., Kondrashov Evgeniy V., Ushakov Igor A., Chertkov Vyacheslav A., Nenajdenko Valentine G.
- Журнал: Journal of Organic Chemistry
- Том: 82
- Номер: 14
- Год издания: 2017
- Издательство: American Chemical Society
- Местоположение издательства: United States
- Первая страница: 7200
- Последняя страница: 7214
- DOI: 10.1021/acs.joc.7b00774
- Аннотация: A detailed study of the reaction of trifluoroacetylated acetylenes and aryl (alkyl) hydrazines was performed, aimed to the regioselective synthesis of 3- or 5-trifluoromethylated pyrazoles. It was found that the regioselectivity of reaction depends dramatically on the solvent nature. Highly polar protic solvents (hexafluoroisopropanol) favor the formation of 3-trifluoromethylpyrazoles. In contrast, when the reaction was performed in polar aprotic solvents (DMSO), the formation of their 5-CF3-substituted isomers was preferentially observed. Alternatively, the regioselective assembly of 3-CF3-substituted pyrazoles can be performed via two-step one-pot procedure. The reaction of trifluoromethylated ynones with aryl (alkyl) hydrazines in the presence of acidic catalysts leads to formation of the corresponding hydrazones. The latter can be smoothly transformed into 3-CF3-pyrazoles by treatment with a base. This solvent-switchable procedure was used for the preparation of such important drugs as Celebrex and SC-560 as well as their isomers in gram scale. The possible reaction mechanism is discussed.
- Добавил в систему: Музалевский Василий Михайлович