ABSTRACT
A convenient and straightforward approach for the radical cascade cyclization/hydrolysis of CN-containing 1,6-enynes with simple ethers under metal- and base-free conditions is described. This strategy provides a variety of valuable ethers-substituted polyheterocycles via the construction of three C-C bonds, one C=O bond, and two new six-membered rings within a single procedure. The resulting products can smoothly undergo follow-up conversions to various useful scaffolds. The methodology shows excellent functional group tolerance, high step- and atom- economy, and mild reaction conditions, which can be further scaled up to gram quantity in a satisfactory yield.
ABSTRACT
C-N bonds are pervasive throughout organic-based materials, natural products, pharmaceutical compounds, and agricultural chemicals. Considering the widespread importance of C-N bonds, the development of greener and more convenient ways to form C-N bonds, especially in late-stage synthesis, has become one of the hottest research goals in synthetic chemistry. Copper-catalyzed radical reactions involving N-centered radicals have emerged as a sustainable and promising approach to build C-N bonds. As a chemically popular and diverse radical species, N-centered radicals have been used for all kinds of reactions for C-N bond formation by taking advantage of their inherently incredible reactive flexibility. Copper is also the most abundant and economic catalyst with the most relevant activity for facilitating the synthesis of valuable compounds. Therefore, the aim of the present Review was to illustrate recent and significant advances in C-N bond formation methods and to understand the unique advantages of copper catalysis in the generation of N-centered radicals since 2016. To provide an ease of understanding for the readers, this Review was organized based on the types of nitrogen sources (amines, amides, sulfonamides, oximes, hydrazones, azides, and tert-butyl nitrite).
