Synthesis of Indazoles by the [3+2] Cycloaddition of Diazo Compounds with Arynes and Subsequent Acyl Migration
作者:Zhijian Liu、Feng Shi、Pablo D. G. Martinez、Cristiano Raminelli、Richard C. Larock
DOI:10.1021/jo702062n
日期:2008.1.1
The [3+2] cycloaddition of a variety of diazocompounds with o-(trimethylsilyl)aryl triflates in the presence of CsF or TBAF at room temperature provides a very direct, efficient approach to a wide range of potentially biologically and pharmaceutically interesting substituted indazoles in good to excellent yields under mild reaction conditions. Simple diazomethane derivatives afford N-unsubstituted
An unusual cascade annulation of arynes with N-alkyl-N-nitrosamides is developed by leveraging aryne σ-insertion and C(sp3)–H bond functionalization strategies under transition-metal-free conditions at ambient temperature, offering functionalized indazoles in high yields and regioselectivity. The protocol is scalable and exhibits a broad substrate scope. The reaction mechanism is also studied with