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610 results on '"Xu, Xinfang"'

158. Copper‐ or Thermally Induced Divergent Outcomes: Synthesis of 4‐Methyl 2<italic>H</italic>‐Chromenes and Spiro‐4<italic>H</italic>‐Pyrazoles.

Author

Zheng, Yang, Qiu, Lihua, Hong, Kemiao, Dong, Shanliang, and Xu, Xinfang

Subjects
COPPER catalysts, PYRAZOLES, HYDRAZONES, RING formation (Chemistry), SULFONATION
Abstract

Abstract: An unprecedented divergent outcome transformation of alkyne tethered N‐sulfonyl hydrazones is reported, which provides a direct and effective access to 4‐methyl 2H‐chromene derivatives and spiro‐4H‐pyrazoles in the presence of copper catalyst or under thermal conditions, respectively. The notable features of this process include readily available starting materials, an inexpensive copper catalyst, mild reaction conditions, broad substrate scope, diverse transformations and potential applications of these generated products. Mechanistic studies indicate that the 3H‐pyrazole, which is generated via direct [3+2] cycloaddition, is the communal key intermediate of these two divergent transformations. To the best of our knowledge, this is the only example of sulfonation reaction that goes through a cascade process involving 3H‐pyrazole, which was isolated and confirmed by single crystal X‐ray diffraction analysis for the first time. [ABSTRACT FROM AUTHOR]

Published
2018
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159. Gold-Catalyzed Oxidative Cyclization/Aldol Addition of Homopropargyl Alcohols with Isatins

Author

Cai, Ju, Wang, Xin, Qian, Yu, Qiu, Lihua, Hu, Wenhao, and Xu, Xinfang

Abstract

A novel gold-catalyzed oxidative cyclization/aldol addition of homopropargyl alcohols with isatins has been developed that provides an effective access to the 3-hydroxyoxindoles in high yields under mild reaction conditions with high diastereoselectivities. In comparison with disclosed transformations of alkyne oxidations via an α-oxo gold carbene route, this is the first example of an aldol-type interception of an ylide (or its enolate form) intermediate with alkyne as a safe and readily available nondiazo carbene precursor.

Published
2019
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