Benign catalysis with zinc: atom-economical and divergent synthesis of nitrogen heterocycles by formal [3 + 2] annulation of isoxazoles with ynol ethers
作者:Xin-Qi Zhu、Han Yuan、Qing Sun、Bo Zhou、Xiao-Qin Han、Zhi-Xin Zhang、Xin Lu、Long-Wu Ye
DOI:10.1039/c8gc02051e
日期:——
zinc-catalyzed formal [3 + 2] annulation of isoxazoles with ynol ethers under exceptionally mild reaction conditions, leading to the atom-economical and divergent synthesis of 2-alkoxyl 1H-pyrroles and 3H-pyrroles, respectively. Importantly, this zinc-catalyzed protocol demonstrates the dramatically divergent reactivity from the relevant platinum catalysis, where the formal [4 + 2] annulation of isoxazoles with
3,5-Dimethylisoxazole (1) was alkylated with sodium amide in liquid ammonia to give 3-methyl-5-alkylisoxazoles. By di- and tri-alkylation reactions using excess sodium amide, isoxazoles having secondary and tertiary alkyl groups at 5-position could be obtained. The hydrogenolysis and hydrolysis of these isoxazoles were also studied.