One-Pot, Three-Step Copper-Catalyzed Five-/Four-Component Reaction Constructs Polysubstituted Oxa(Thia)zolidin-2-imines

A novel one-pot synthesis of polysubstituted oxa(thia)zolidin-2-imines has been developed. It employs A 3 -cou- pling of aldehyde and amine with alkyne to form propargyl amine, which on (thio)amidation with iso(thio)cyanate produces N-propar- gyl(thio)urea, and a cyclization reaction. A 5-exo-dig iodocycliza- tion of N-propargylurea constructs 5-iodomethyleneoxazolidin-2- imine, while cycloisomerization of the thio analogue provides 5- methylenethiazolidin-2-imine. In this process, CuI catalysis has been found to be crucial, and the cyclization occurs through oxy- gen/sulfur (not nitrogen) nucleophilic attack to alkyne.