1,3-Dipolar Cycloaddition of Alkyne-Tethered N-Tosylhydrazones: Synthesis of Fused Polycyclic Pyrazoles

Yang Zheng, Xiaolu Zhang, Ruwei Yao, YueCheng Wen, Jingjing Huang^*（黄晶晶）, and Xinfang Xu^*（徐新芳）

Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science; Analysis and Testing Centre, Soochow University, Suzhou 215123, China

J. Org. Chem., 2016, 81 (22), pp 11072–11080

A general and transition-metal-free access to the fused polycyclic pyrazoles via an intramolecular 1,3-dipolar cycloaddition reaction of alkyne-tethered tosylhydrazones has been reported. The pure solid products could be obtained without column chromatography in high to excellent yields, and the obtained products are useful bioactive molecules or could be used as the key intermediate for synthesis of these compounds in one or two steps. Additionally, a [3+2]-cycloaddition followed by a direct H-shift aromatization reaction mechanism was proposed, which is different from the previously reported aryl or alkyl sequential [1,5]-sigmatropic rearrangement pathway.

链接：http://pubs.acs.org/doi/abs/10.1021/acs.joc.6b02076