EosinY and copper-catalyzed oxidative [2 + 3] annulation of glycine esters with oxiranes and thiiranes under light free conditions

Herein, we report an oxidative formal [2 + 3] cycloaddition reaction of glycine esters with oxiranes/thiiranes under non-photoredox conditions using the catalytic system consisting of eosin-Y, Cu(OAc)₂ and HI. This one-pot protocol delivers an array of oxazolidine-2-carboxylic acids and thiaoxazolidine-2-carboxylic acid derivatives in moderate to good yields under mild reaction conditions. The value of this methodology is demonstrated in preparative scale reactions and downstream synthetic transformations. Based on a series of control experiments, a mechanistic pathway is also proposed.