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.

Anew "single-flask" method was developed for the synthesis of imidazolidines and pyrrolidines with high stereoselectivity.F irst, aS chiff base was arylated with an aryne. Second, an intramolecular proton transfer took place from the methylene position to the anionic aryne ring.T hird, the resultant ylide reacted with as econd 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 %y ields.

Aryne-Induced Novel Tandem 1,2-Addition/(3 + 2) Cycloaddition to Generate Imidazolidines and Pyrrolidines. -(SWAIN, S. P.; SHIH, Y.-C.; TSAY, S.-C.; JACOB, J.; LIN, C.-C.; HWANG, K. C.; HORNG, J.-C.; HWU*, J. R.; Angew. Chem., Int. Ed. 54 (2015) 34, 9926-9930, http://dx.doi.org/10.1002/anie.201503319 ; Dep. Chem., Natl. Tsing Hua Univ., Hsinchu 30013, Taiwan; Eng.) -Toeppel 51-063