B(C6F5)3/I2 co-mediated cascade [4 + 2]/[3 + 2] cyclization to access spiroimidazolines
Huanyi Qiu1,2, Jingxi Fang2, Mingyan Guan3
1School of Pharmaceutical Science, Zhejiang Chinese Medical University, Hangzhou, Zhejiang, 310053, P. R. China. yongmin.ma@tzc.edu.cn.
Abstract:
A highly step- and atom-economical cascade [4 + 2]/[3 + 2] cyclization has been developed for the synthesis of structurally novel spiroimidazolines. Catalyzed by only 1 mol% B(C6F5)3 in the presence of I2, this one-pot, metal-free method assembles two rings from three readily available starting materials, affording a diverse library of products in up to 88% yields. Key to its practicality are the high step- and atom-economy, avoidance of pre-constructed rings, and operational simplicity. Mechanistic studies support a sequential pathway, offering a practical and sustainable approach to access privileged spiro scaffolds with potential medicinal chemistry applications.
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