Regioselective Preparation of Saturated Spirocyclic and Ring-Expanded Fused Pyrazoles

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• 作者：Rohan R. Merchant ; Daniel M. Allwood ; David C. Blakemore ; Steven V. Ley
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：September 19, 2014
• 年：2014
• 卷：79
• 期：18
• 页码：8800-8811
• 全文大小：603K
• ISSN：1520-6904

文摘

Saturated bicyclic pyrazoles represent an important class of biologically active molecules, but their preparation can be hampered by labor-intensive synthesis of required starting materials. A convenient one- or two-step procedure for the synthesis of saturated spirocyclic and fused pyrazoles is reported. The synthesis benefits from the use of readily available alkynes and bench-stable tosylhydrazones, which are easily prepared from their parent ketones. Sigmatropic rearrangement of spirocyclic pyrazoles to fused analogues occurs with concomitant one-carbon expansion of the saturated ring, allowing rapid access to a range of pharmaceutically and agrochemically relevant polycyclic structures featuring a broad scope of saturated ring sizes.