Aryne-Induced Novel Tandem 1,2-Addition/(3+2) Cycloaddition to Generate Imidazolidines and Pyrrolidines
Sharada P Swain1, Yi-Chun Shih1, Shwu-Chen Tsay1,2
1Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu 30013 (Taiwan).
Abstract:
A new "single-flask" method was developed for the synthesis of imidazolidines and pyrrolidines with high stereoselectivity. First, a Schiff base was arylated with an aryne. Second, an intramolecular proton transfer took place from the methylene position to the anionic aryne ring. Third, the resultant ylide reacted with a second equivalent of the same Schiff base in situ or an electron-deficient alkene through a (3+2) cycloaddition. These sequential tandem 1,2-addition/(3+2) cycloaddition reactions led to the desired heterocycles in 63-88% yields.
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